Communication method, communication system, master base station and program to be executed by computer

Abstract

To provide a communication method for transmitting data from an access point to a wireless device while avoiding a competition of a plurality of base station groups.SOLUTION: A communication method includes: a first step for a master base station 2-1 of a cooperative base station group AP_G1 to determine whether or not a joint transmission JT by the cooperative base station group AP_G1 competes with a joint transmission JT by one cooperative base station group in cooperative base station groups AP_G2 to AP_Gm; a second step for the master base station 2-1 and q1 pieces of slave base stations in n1 pieces of slave base stations to transmit (q1+1) pieces of transmission frames to a wireless device 4-1 through a wireless communication using the joint transmission JT when it is determined in the first step that the joint transmissions do not compete; and a third step only for the master station 2-1 to transmit the transmission frame to the wireless device 4-1 through the wireless communication when it is determined in the first step that the joint transmissions compete.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a communication method, a communication system, a master base station, and a program to be executed by a computer. [Background technology]

[0002] Toward the realization of Society 5.0, there is a demand for high-capacity, simultaneous multi-connection transmission technologies for high-definition video, sensing information, and other data in fields such as education and medical care, as well as for the advancement of communication tools such as AR and VR, and mobility (Non-Patent Documents 1 to 3).

[0003] For example, if you try to transmit full-spec 8K video at 120 fps uncompressed to reduce latency, a communication speed of over 100 Gbps is required.

[0004] For example, when focusing on wireless LAN (Local Area Network), the maximum communication speed of the IEEE802.11 wireless LAN standard (176 Gbps for IEEE802.11ay), which has been completed and published to date, is insufficient when considering simultaneous provision of services to multiple users and widespread use.

[0005] Meanwhile, IEEE802.15.3d, whose standard was finalized and published in 2017, utilizes the terahertz band, which allows for wide frequency channel widths, enabling point-to-point communication at a maximum transmission speed of 100 Gbps. However, it does not support the license-free and simultaneous connection of multiple devices that is typical of IEEE802.11 wireless LAN.

[0006] Currently, at the IEEE802.11 standardization conference, discussions are underway on Joint Transmission, which involves linking multiple access points to transmit data over multiple links. [Prior art documents] [Non-patent literature]

[0007] [Non-Patent Document 1] Cabinet Office, "Society 5.0: A New Society Pioneering Science and Technology Innovation" Explanatory Material" [Non-patent document 2] Cabinet Office, "Sixth Science, Technology and Innovation Basic Plan," March 2021 [Non-patent document 3] KDDI Corporation, "Beyond5G / 6G White Paper Ver.2.0.1", October 2021 Summary of the Invention [Problem to be solved by the invention]

[0008] To perform Joint Transmission, it is necessary to allocate data to be transmitted to each cooperating access point in advance.

[0009] However, if the same channel as that used for data transmission from each access point to a wireless device is used to distribute transmission data to each cooperating access point, wireless resources become constrained, resulting in a problem of low throughput.

[0010] In cellular CoMP (Coordination Multi-Point), data transmission time is fixed by time slot unit transmission and scheduling, but IEEE802.11 wireless LAN uses channel access by CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance) and the transmission time is variable, which causes the above problem.

[0011] In order to solve the above problem, it is conceivable to distribute data by using a backhaul network connected via multiple base stations.

[0012] However, when a star configuration is adopted in which multiple base stations are directly connected to a switch via a backhaul, a problem occurs in which joint transmissions of multiple base stations having the star configuration conflict with each other.

[0013] Therefore, according to an embodiment of the present invention, a communication method is provided in which data is transmitted from an access point to a wireless device while avoiding contention among a plurality of base station groups.

[0014] Furthermore, according to the embodiment of the present invention, there is provided a communication system that transmits data from an access point to a wireless device while avoiding contention among a plurality of base station groups.

[0015] Furthermore, according to the embodiment of the present invention, a master base station is provided that transmits data from an access point to a wireless device while avoiding contention among a plurality of base station groups.

[0016] Furthermore, according to an embodiment of the present invention, there is provided a program for causing a computer to execute data transmission from an access point to a wireless device while avoiding contention among a plurality of base station groups. [Means for solving the problem]

[0017] (Configuration 1) According to an embodiment of the present invention, the communication method comprises: A communication system including: a first cooperating base station group having a star configuration in which a master base station and a slave base station are directly connected to a switch via a backhaul, the first cooperating base station group including a first master base station and n1 (n1 is an integer equal to or greater than 1) first slave base stations; and a second cooperating base station group having a star configuration and including a second master base station, the second master base station and n2 (n2 is an integer equal to or greater than 1) second slave base stations, the system comprising ... transmitting transmission data D_trsm to a wireless device using joint transmission in which the master base station and the slave base stations jointly transmit data to the wireless device by wireless communication of a CSMA / CA system using a communication channel consisting of one or a plurality of channels; a first step of determining whether joint transmission by a first cooperating base station group is possible when a first master base station receives transmission data D_trsm from a transmission source; a second step of calculating, when it is determined in the first step that joint transmission is possible, q1 data amounts of q1 pieces of transmission data to be allocated to q1 (q1 is an integer satisfying 1≦q1≦n1) first slave base stations that are capable of joint transmission among the n1 first slave base stations; a third step in which the first master base station calculates padding having a length consisting of a padding time; a fourth step in which the first master base station transmits a notification of execution of joint transmission to the second cooperating base station group; a fifth step in which, after the fourth step, the first master base station transmits, via wireless communication, a transmission timing notification for notifying the wireless device of the timing for transmitting the transmission frame and padding to the q first slave base stations; a sixth step in which, after the second step, the first master base station transmits q1 pieces of transmission data, each having q1 data amounts, to the q1 first slave base stations via the backhaul via the switch; a seventh step in which the first master base station and each of the q1 first slave base stations perform a transmission frame generation process, which is a process of generating a transmission frame based on the transmission data, after the second step; an eighth step of, when a transmission timing arrives, transmitting (q1+1) transmission frames to the wireless device by wireless communication through joint transmission by the first master base station and the q1 first slave base stations; The method further comprises a ninth step in which, after the eighth step, the first master base station receives a Block Ack from the wireless device, which sends a block Ack to confirm reception of the frames.

[0018] (Configuration 2) In configuration 1, in a first step, when the first master base station determines that joint transmission by the first cooperating base station group does not conflict with joint transmission by the second cooperating base station group, the first master base station determines that joint transmission by the first cooperating base station group is possible.

[0019] (Configuration 3) In configuration 2, in the first step, the first master base station determines that joint transmission is possible when it satisfies a first condition consisting of the initiation of joint transmission by the first cooperating base station group, satisfies a second condition consisting of receiving a notification of execution of joint transmission from the second master base station of the second cooperating base station group, and satisfies a third condition consisting of not being within the occupied time of joint transmission by the second cooperating base station group, or when it satisfies both the first condition and a fourth condition consisting of not receiving a notification of execution of joint transmission from the second master base station of the second cooperating base station group.

[0020] (Configuration 4) In configuration 3, in the first step, the first master base station determines that joint transmission is possible when it satisfies, in place of the third and fourth conditions, a fifth condition that the time is within the occupied time for joint transmission by the second cooperating base station group and a sixth condition that the second master base station of the second cooperating base station group has obtained from the second master base station the switching capacity of the switch to be occupied in data distribution to q2 (q2 is an integer satisfying 1≦q2≦n2) second slave base stations out of n2 second slave base stations, and when it satisfies the first and second conditions.

[0021] (Configuration 5) In configuration 1, when the first master base station determines in the first step that it is not possible to start joint transmission by the first cooperating base station group, or when it receives a notification of execution of joint transmission from the second master base station of the second cooperating base station group and determines that it is within the occupied time for joint transmission by the second cooperating base station group, instead of steps 2 to 8, the configuration further includes a tenth step in which only the first master base station transmits a transmission frame including transmission data D_trsm to the wireless device by wireless communication.

[0022] (Configuration 6) In configuration 1, when it is determined in the first step that the first master base station will not perform joint transmission based on a first transmission time when the (q1+1) transmission frames are transmitted to the wireless device through joint transmission and a second transmission time when only the first master base station transmits a transmission frame including the transmission data D_trsm to the wireless device, the first master base station transmits a transmission frame including the transmission data D_trsm to the wireless device only by the first master base station; When the first master base station and q1 first slave base stations determine in the first step to perform joint transmission based on the first transmission time and the second transmission time, in the eighth step, when the transmission timing arrives, they transmit (q1+1) transmission frames to the wireless device via wireless communication through joint transmission.

[0023] (Configuration 7) In configuration 1, the sixth and seventh steps are performed in parallel with the fifth step.

[0024] (Configuration 8) In configuration 1, when joint transmission by the first cooperating base station group and joint transmission by the second cooperating base station group conflict with each other, in the sixth step, the first master base station adjusts the transmission speed when transmitting q1 pieces of transmission data from the switch via backhaul to each of the q1 first slave base stations using the switching capacity occupied by the first cooperating base station group, and transmits the q1 pieces of transmission data to each of the q1 first slave base stations using the adjusted transmission speed.

[0025] (Configuration 9) Furthermore, according to an embodiment of the present invention, the communication system includes: a first cooperating base station group having a star configuration in which a master base station and a slave base station are directly connected to a switch via a backhaul, the first cooperating base station group including a first master base station and n1 (n1 is an integer equal to or greater than 1) first slave base stations; a second cooperating base station group having a star configuration, the second cooperating base station group including a second master base station and n2 (n2 is an integer equal to or greater than 1) second slave base stations; a switch that receives data transmitted from either the first or second master base station via a backhaul and transmits the received data via the backhaul to a slave base station in the same cooperating base station group as the data transmission source; a first cooperating base station group; and a wireless device that receives (q1+1) transmission frames through joint transmission by q1 (q1 is an integer satisfying 1≦q1≦n1) first slave base stations among n1 first slave base stations, in which the master base station and the slave base stations jointly transmit data to the wireless device by wireless communication of a CSMA / CA system using a communication channel consisting of one or a plurality of channels, or that receives a transmission frame including transmission data D_trsm transmitted only by the first master base station; The first master base station of the first cooperating base station group performs a first receiving process when receiving a notification of execution of joint transmission from a second master base station of a second cooperating base station group; a first calculation process when determining that joint transmission is possible, of calculating q1 data amounts of the q1 transmission data to be assigned to each of the q1 first slave base stations; a second calculation process when calculating padding having a length equal to a padding time; a first transmitting process when transmitting a notification of execution of joint transmission to the second cooperating base station group after the first and second calculation processes; and a first transmitting process when transmitting a notification of transmission timing to notify a wireless device of a timing to transmit a transmission frame and the padding wirelessly. a second transmission process for transmitting q1 pieces of transmission data, each having q1 data amounts allocated to the q1 first slave base stations, to each of the q1 first slave base stations; a transmission frame generation process for generating a transmission frame based on its own transmission data after the first and second calculation processes; and a second reception process for transmitting (q1+1) transmission frames to the wireless device by joint transmission with the q1 first slave base stations and then receiving a block Ack from the wireless device that collectively sends an Ack to confirm reception of the frames; the q1 first slave base stations perform a third reception process of receiving a notification of a transmission timing from the first master base station and a fourth reception process of receiving the q1 pieces of transmission data from the first master base station via the switch and the backhaul, and perform a transmission frame generation process of generating q1 transmission frames based on the q1 pieces of transmission data received in the fourth reception process; When a transmission timing arrives, the first master base station and the q1 first slave base stations transmit (q1+1) transmission frames to the wireless device through joint transmission; The wireless device receives (q1+1) transmission frames transmitted by joint transmission from the first master base station and the q1 first slave base stations, and transmits a Block Ack to the first master base station.

[0026] (Configuration 10) In configuration 9, when the first master base station determines that joint transmission by the first cooperating base station group does not conflict with joint transmission by the second cooperating base station group, the first master base station determines that joint transmission by the first cooperating base station group is possible.

[0027] (Configuration 11) In configuration 10, the first master base station determines that joint transmission is possible when it satisfies a first condition consisting of the initiation of joint transmission by the first cooperating base station group, a second condition consisting of receiving a notification of execution of joint transmission from the second master base station of the second cooperating base station group, and a third condition consisting of not being within the occupied time of joint transmission by the second cooperating base station group, or when it satisfies both the first condition and a fourth condition consisting of not receiving a notification of execution of joint transmission from the second master base station of the second cooperating base station group.

[0028] (Configuration 12) In configuration 11, the first master base station determines that joint transmission is possible when it satisfies, in place of the third and fourth conditions, a fifth condition that the period is within the occupied time for joint transmission by the second cooperating base station group, and a sixth condition that the second master base station of the second cooperating base station group has obtained from the second master base station the switching capacity of the switch to be occupied in distributing data to q2 (q2 is an integer satisfying 1≦q2≦n2) second slave base stations out of n2 second slave base stations, and when it satisfies the first and second conditions.

[0029] (Configuration 13) In configuration 9, when the first master base station determines that it is not possible to start joint transmission by the first cooperating base station group, or when it receives a notification of execution of joint transmission from the second master base station of the second cooperating base station group and determines that it is within the occupied time for joint transmission by the second cooperating base station group, only the first master base station transmits a transmission frame including transmission data D_trsm to the wireless device via wireless communication.

[0030] (Configuration 14) In configuration 9, the first master base station determines whether to perform joint transmission based on a transmission time when (q1+1) transmission frames are transmitted to the wireless device by joint transmission and a transmission time when only the first master base station transmits a transmission frame including the transmission data D_trsm to the wireless device; and when it is determined not to perform joint transmission, transmits a transmission frame including the transmission data D_trsm to the wireless device only by the first master base station; When the first master base station and the q1 first slave base stations determine to perform joint transmission, when the transmission timing arrives, the first master base station and the q1 first slave base stations transmit (q1+1) transmission frames to the wireless device via wireless communication through joint transmission.

[0031] (Configuration 15) In configuration 9, the first master base station executes the second transmission process and the process of generating a transmission frame in parallel with the first transmission process.

[0032] (Configuration 16) In configuration 9, in the second transmission process, when joint transmission by the first cooperating base station group and joint transmission by the second cooperating base station group compete with each other, the first master base station adjusts the transmission speed when transmitting q1 pieces of transmission data from the switch to each of the q1 first slave base stations via backhaul using the switching capacity occupied by the first cooperating base station group, and transmits the q1 pieces of transmission data to each of the q1 first slave base stations using the adjusted transmission speed.

[0033] (Configuration 17) Furthermore, according to an embodiment of the present invention, the master base station A first cooperating base station group has a star configuration in which a master base station and a slave base station are directly connected to a switch via a backhaul, the first cooperating base station group including n1 (n1 is an integer equal to or greater than 1) first slave base stations, a determination unit that determines whether or not joint transmission is possible, in which the master base station and q1 (q1 is an integer satisfying 1≦q1≦n1) slave base stations among n1 (n1 is an integer equal to or greater than 1) first slave base stations jointly transmit data to a wireless device by CSMA / CA wireless communication using a communication channel consisting of one or more channels; a calculation unit that calculates padding having a length equal to a padding time and a data amount of each of the q1 transmission data to be allocated to each of the q1 first slave base stations when the determination unit determines that joint transmission is possible; q1 transmission data d each having q1 data amounts from q1 first slave base stations are transmitted via the switch via backhaul. 1_trsm ~d q1_trsm to the q1 first slave base stations, and transmits a notification of execution of joint transmission to cooperating base station groups other than the first cooperating base station group; Transmission frame F of the master base station of the first cooperating base station group mst_trsma generation unit that performs a process of generating a transmission frame, which is a process of generating a transmission frame; A notification of transmission timing for notifying the wireless device of the timing for transmitting the transmission frame and padding having a length equal to the padding time are transmitted to the q1 first slave base stations by wireless communication, and when the transmission timing of the transmission frame arrives, a transmission frame F is transmitted by joint transmission. mst_trsm and a wireless unit that transmits the frame to the wireless device by wireless communication and receives a block Ack from the wireless device, which transmits an Ack in a batch to confirm reception of the frame.

[0034] (Configuration 18) In configuration 17, when a cooperating base station group having a star configuration and including a second master base station and n2 (n2 is an integer equal to or greater than 1) second slave base stations is defined as a second cooperating base station group, The determination unit determines that joint transmission by the first cooperating base station group is possible when it determines that joint transmission by the first cooperating base station group does not conflict with joint transmission by the second cooperating base station group.

[0035] (Configuration 19) In configuration 18, the determination unit determines that joint transmission is possible when a first condition is satisfied, which is that joint transmission can be started by the first group of cooperating base stations, a second condition is satisfied, which is that a notification of joint transmission execution has been received from the second master base station, and a third condition is satisfied, which is that the time is not within the occupied time of joint transmission by the second group of cooperating base stations, or when the first condition and a fourth condition is satisfied, which is that a notification of joint transmission execution has not been received from the second master base station.

[0036] (Configuration 20) In configuration 19, the determination unit determines that joint transmission is possible when the fifth condition, which is that the period is within the occupied time for joint transmission by the second cooperating base station group, and the sixth condition, which is that the second master base station of the second cooperating base station group has obtained from the second master base station the switching capacity of the switch to be occupied in data distribution to q2 (q2 is an integer satisfying 1≦q2≦n2) second slave base stations out of n2 second slave base stations, are satisfied in place of the third and fourth conditions, and when the first and second conditions are satisfied.

[0037] (Configuration 21) In configuration 17, when the determining unit determines that joint transmission is not possible, the wireless unit transmits a transmission frame F_trsm including transmission data D_trsm to the wireless device.

[0038] (Configuration 22) In the configuration 17, when the joint transmission by the first cooperating base station group and the joint transmission by the second cooperating base station group compete with each other, the wired unit transmits q1 pieces of transmission data d 1_trsm ~d q1_trsm The transmission speed when transmitting from the switch to the q1 first slave base stations is adjusted using the switching capacity occupied by the first cooperating base station group, and the q1 transmission data d 1_trsm ~d q1_trsm to the q1 first slave base stations, respectively.

[0039] (Configuration 23) Further, according to an embodiment of the present invention, the program A program for causing a computer to execute transmission of transmission data D_trsm in a master base station of a first cooperating base station group having a star configuration in which a master base station and a slave base station are directly connected to a switch via a backhaul, the first cooperating base station group including n1 (n1 is an integer equal to or greater than 1) first slave base stations, a first step in which a determination unit determines whether or not joint transmission is possible in which a master base station and q1 slave base stations jointly transmit data to a wireless device by wireless communication in a CSMA / CA system using a communication channel consisting of one or more channels; a second step in which, when it is determined in the first step that joint transmission is possible, the calculation unit calculates padding having a length equal to q1 data amounts of the q1 transmission data to be assigned to each of the q1 first slave base stations and a padding time; a third step in which the wired unit transmits a notification of execution of joint transmission to the second cooperating base station group via the switch; a fourth step in which the wireless unit transmits, via wireless communication, to the q first slave base stations, a notification of transmission timing for notifying the wireless device of the timing for transmitting the transmission frame and padding; The wired unit transmits q1 pieces of transmission data d each having q1 amounts of data from q1 (q1 is an integer satisfying 1≦q1≦n1) first slave base stations among the n1 first slave base stations via a backhaul through a switch. 1_trsm ~d q1_trsm a fifth step of transmitting the q1 first slave base stations to the q1 first slave base stations and transmitting a notification of execution of joint transmission to cooperating base station groups other than the first cooperating base station group; The generating unit generates a transmission frame F of the master base station of the first cooperating base station group. mst_trsm a sixth step of performing a process of generating a transmission frame, which is a process of generating a The wireless unit transmits a notification of transmission timing, which notifies the wireless device of the timing to transmit the transmission frame, and padding to the q1 first slave base stations by wireless communication, and when the transmission timing of the transmission frame arrives, transmits the transmission frame F by joint transmission. mst_trsm a seventh step of transmitting the frame to the wireless device via wireless communication, and receiving a block Ack from the wireless device that collectively sends an Ack to confirm reception of the frames.

[0040] (Configuration 24) In configuration 23, when a cooperating base station group having a star configuration and including a second master base station and n2 (n2 is an integer equal to or greater than 1) second slave base stations is defined as a second cooperating base station group, In the first step, when the determination unit determines that joint transmission by the first cooperating base station group does not conflict with joint transmission by the second cooperating base station group, the determination unit determines that joint transmission by the first cooperating base station group is possible.

[0041] (Configuration 25) In configuration 24, in the first step, the determination unit determines that joint transmission is possible when a first condition is satisfied, which is that joint transmission can be started by the first group of cooperating base stations, a second condition is satisfied, which is that a notification of joint transmission execution has been received from the second master base station, and a third condition is satisfied, which is that the time is not within the occupied time of joint transmission by the second group of cooperating base stations, or when the first condition and a fourth condition is satisfied, which is that a notification of joint transmission execution has not been received from the second master base station.

[0042] (Configuration 26) In configuration 25, in the first step, the judgment unit judges that joint transmission is possible when the fifth condition, which is that the time is within the occupation time of joint transmission by the second cooperating base station group, and the sixth condition, which is that the second master base station of the second cooperating base station group has obtained from the second master base station the switching capacity of the switch to be occupied in data distribution to q2 (q2 is an integer satisfying 1≦q2≦) second slave base stations out of n2 second slave base stations, are satisfied in place of the third and fourth conditions, and the first and second conditions are satisfied.

[0043] (Configuration 27) In the configuration 23, when the wireless unit determines in the first step by the determining unit that joint transmission is not possible, in the seventh step, the wireless unit transmits a transmission frame F_trsm including transmission data D_trsm to the wireless device.

[0044] (Configuration 28) In the configuration 23, when the joint transmission by the first cooperating base station group and the joint transmission by the second cooperating base station group compete with each other, in the fifth step, the wired unit 1_trsm ~d q1_trsm The transmission speed when transmitting from the switch to the q1 first slave base stations is adjusted using the switching capacity occupied by the first cooperating base station group, and the q1 transmission data d 1_trsm ~d q1_trsm to the q1 first slave base stations, respectively. [Effects of the Invention]

[0045] Data can be transmitted from an access point to a wireless device while avoiding contention among multiple base station groups. [Brief explanation of the drawings]

[0046] [Figure 1] 1 is a schematic diagram of a communication system in accordance with a first embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram of a master base station 2-1 shown in FIG. [Figure 3] 10 is a conceptual diagram showing information previously stored in the control unit 13. FIG. [Figure 4] 1 is a schematic diagram showing the contention of joint transmission JT in a star-type backhaul. [Figure 5] FIG. 10 is a schematic diagram showing frame processing when a joint transmission JT conflict occurs. [Figure 6] FIG. 2 is a schematic diagram of a slave base station 3-11 shown in FIG. [Figure 7] FIG. 2 is a schematic diagram of a wireless device 4-1 shown in FIG. [Figure 8] FIG. 10 is a conceptual diagram for explaining a method for generating transmission data in a master base station 2-1 and q1 slave base stations. [Figure 9] FIG. 2 is a conceptual diagram showing the configuration of a transmission frame. [Figure 10] 2 is a schematic diagram illustrating frame processing in the communication system 10 shown in FIG. [Figure 11] FIG. 1 is a schematic diagram illustrating conventional frame processing. [Figure 12] 1. FIG. 4 is another schematic diagram illustrating frame processing in the communication system 10 shown in FIG. [Figure 13] 1 is a first flowchart illustrating the operation of communication system 10 shown in FIG. [Figure 14] 10 is a second flowchart illustrating the operation of the communication system 10 shown in FIG. [Figure 15] 14 is a flowchart for explaining the detailed operation of step S14 in FIG. 13. [Figure 16] FIG. 10 is a schematic diagram of a communication system according to a second embodiment. [Figure 17] FIG. 17 is a schematic diagram of the master base station 2-1A shown in FIG. [Figure 18] FIG. 10 is a schematic diagram showing frame processing in the second embodiment. [Figure 19] 17 is a first flowchart illustrating the operation of the communication system 10A shown in FIG. [Figure 20] 17 is a second flowchart illustrating the operation of the communication system 10A shown in FIG. [Figure 21] 21 is a flowchart for explaining the detailed operation of step S14A in FIG. 20. DETAILED DESCRIPTION OF THE INVENTION

[0047] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals and description thereof will not be repeated.

[0048] [Embodiment 1] 1 is a schematic diagram of a communication system according to a first embodiment of the present invention. Referring to FIG. 1, a communication system 10 according to the first embodiment of the present invention includes a switch 1 and a group of cooperating base stations AP_G1 to AP_Gm m is an integer of 2 or more.

[0049] m cooperative base station groups AP_G1 to AP_G m Each of the above has a star configuration, in which a master base station and a slave base station are directly connected to a switch 1 via a backhaul 4.

[0050] The cooperating base station group AP_G1 includes a master base station 2-1, n1 (n1 is an integer equal to or greater than 1) slave base stations 3-11 to 3-1n1, and a wireless device 4-1. m is the master base station 2-m and n m (n m is an integer equal to or greater than 1) slave base stations 3-m1 to 3-mn m and a wireless device 4-m.

[0051] In the cooperating base station group AP_G1, the master base station 2-1 and n1 slave base stations 3-11 to 3-1n1 are directly connected to the switch 1 via the backhaul 4. m In this case, master base stations 2-m and n m Slave base stations 3-m1 to 3-mn m is directly connected to Switch 1 by Backhaul 4.

[0052] Therefore, the cooperating base station groups AP_G1 to AP_G m Each of these is a group of cooperating base stations having a star configuration.

[0053] In FIG. 1, solid arrows represent transmission and reception of data via wireless communication and notification of transmission results via wireless communication, and dotted arrows represent transmission and reception of control information via wireless communication.

[0054] m cooperative base station groups AP_G1 to AP_G m Each of these is arranged in a wireless communication space.

[0055] The master base station 2-1 is connected to n1 slave base stations 3-11 to 3-1n1 via the backhaul 4 and the switch 1. Similarly, the master base station 2-m is connected to n1 slave base stations 3-11 to 3-1n1 via the backhaul 4 and the switch 1. m Slave base stations 3-m1 to 3-mn m and is connected.

[0056] In the cooperating base station group AP_G1, the master base station 2-1 and n1 slave base stations 3-11 to 3-1n1 are located at mutually different positions, and the wireless device 4-1 is located within the communication range of wireless communication by each of the master base station 2-1 and the n1 slave base stations 3-11 to 3-1n1.

[0057] Similarly, the cooperative base station group AP_G m In this case, master base stations 2-m and n m Slave base stations 3-m1 to 3-mn m are located at different positions from each other. The wireless device 4-m is connected to the master base stations 2-m and n. m Slave base stations 3-m1 to 3-mn m are located within communication range of wireless communication by each of the

[0058] The switch 1 transmits m cooperating base station groups AP_G1 to AP_G2 via a backhaul 4. m The base station receives transmission data transmitted from one of the master base stations (= one of the master base stations 2-1 to 2-m), and transmits the received transmission data via the backhaul 4 to a slave base station in the same cooperating base station group as the data sender.

[0059] In this way, the switch 1 is a repeater that relays transmission data between the master base station and the slave base station of each cooperating base station group.

[0060] The master base station 2-1, n1 slave base stations 3-11 to 3-1n1, and wireless device 4-1 perform wireless communication using a single channel, Ch_JT, according to the CSMA / CA system.

[0061] Similarly, master base stations 2-m, n m Slave base stations 3-m1 to 3-mn m The wireless device 4-m and the wireless device 4-m communicate wirelessly on a channel Ch_JT consisting of one channel using the CSMA / CA method.

[0062] In the embodiment of the present invention, the "joint transmission JT" refers to the master base station 2-1 and q1 (q1 is an integer satisfying 1≦q1≦n1) slave base stations among the n1 slave base stations 3-11 to 3-1n1 in the cooperating base station group AP_G1 cooperating to transmit the transmission data D_trsm to the wireless device 4-1 by wireless communication using the channel Ch_JT in accordance with the CSMA / CA system. m In this case, the master base station 2-m and m Slave base stations 3-m1 to 3-mn m Q of m (q m is 1≦q m ≦n m The slave base stations (an integer satisfying the above condition) cooperate to transmit the transmission data D_trsm to the wireless device 4-m by wireless communication using the channel Ch_JT in accordance with the CSMA / CA method.

[0063] In the cooperating base station AP_G2, q2 (q2 is an integer satisfying 1≦q2≦n2) slave base stations out of n2 (n2 is an integer equal to or greater than 1) slave base stations 3-21 to 3-2n2 are slave base stations capable of performing the joint transmission JT, and in the cooperating base station AP_G3, q3 (q3 is an integer satisfying 1≦q3≦n3) slave base stations out of n3 (n3 is an integer equal to or greater than 1) slave base stations 3-31 to 3-3n3 are slave base stations capable of performing the joint transmission JT. m-1 In this case, n m-1 (n m-1 is an integer equal to or greater than 1) slave base stations 3-m-11 to 3-m-1n m-1 Q ofnm-1 (q nm-1 is 1≦q nm-1 ≦n m-1 The slave base stations that can perform joint transmission JT are the slave base stations that can perform joint transmission JT.

[0064] The master base station 2-1 receives the transmission data D_trsm from the source, and then transmits an RTS (Request To Send) to the n1 slave base stations 3-11 to 3-1n1 and the wireless device 4-1 by wireless communication using the channel Ch_JT.

[0065] Thereafter, when the master base station 2-1 receives a CTS (Clear To Send) from the wireless device 4-1 via wireless communication using channel Ch_JT, it transmits a start possibility confirmation frame FS_PB to n1 slave base stations 3-11 to 3-1n1 via wireless communication using channel Ch_JT to confirm whether or not the joint transmission JT can be started.

[0066] Then, the master base station 2-1 receives, via wireless communication using channel Ch_JT, from n1 slave base stations 3-11 to 3-1n1, start possibility response frames FRSP indicating whether or not the joint transmission JT can be started in response to the start possibility confirmation frame FS_PB for the joint transmission JT.

[0067] Here, the start permission response frame FRSP includes "JT_OK" indicating that the joint transmission JT can be started, or "JT_NG" indicating that the joint transmission JT cannot be started.

[0068] When the master base station 2-1 receives n1 start possibility response frames FRSP from n1 slave base stations 3-11 to 3-1n1, it determines whether or not it is possible to start the joint transmission JT based on the received n1 start possibility response frames FRSP.

[0069] More specifically, the master base station 2-1 determines that the joint transmission JT can be started when q1 of the n1 start permission / rejection response frames FRSP contain "JT_OK." That is, the master base station 2-1 determines that the joint transmission JT with the q1 slave base stations 3-11 to 3-1q1 can be started.

[0070] On the other hand, when all of the n1 start permission / prohibition response frames FRSP include "JT_NG", the master base station 2-1 determines that the start of the joint transmission JT is impossible.

[0071] When the master base station 2-1 determines that the joint transmission JT can be started, the master base station 2-1 receives a joint transmission JT execution notification E from the master base stations of the other cooperating base station groups other than the cooperating base station group AP_G1. X-NOTF It is determined whether or not the message has been received.

[0072] Then, the master base station 2-1 receives a notification E of execution of the joint transmission JT from the master base stations of the other cooperating base station groups. X-NOTF When it is determined that the signal has been received, the occupied time T of the joint transmission JT by other cooperating base stations is OCCUPY Determine whether it is within the range.

[0073] Then, in either of the following cases (I) and (II), the master base station 2-1 determines that joint transmission JT by the cooperating base station group AP_G1 is possible.

[0074] (I) Determine that the joint transmission JT can be started, and receive a joint transmission JT execution notification E from other cooperating base stations. X-NOTF and the occupancy period T of the joint transmission JT of the other cooperating base station group is OCCUPY When it is determined that the (II) Determine that the joint transmission JT can be started, and send a joint transmission JT execution notification E from other cooperating base station groups. X-NOTF When it is determined that the When the master base station 2-1 determines that joint transmission JT is possible by the above (I) or (II), it determines the amount of data d to be distributed to each of the q1 slave base stations 3-11 to 3-1q1. 11 ~d 1q1 and calculate the padding time.

[0075] The master base station 2-1 then assigns the occupation time T OCCUPY Joint transmission of JT execution notice E including X-NOTF Send.

[0076] Then, the master base station 2-1 executes the following steps (1) to (3).

[0077] (1) The master base station 2-1 transmits a notification of transmission timing and padding PD having a length equal to the padding time to q1 slave base stations by wireless communication using the channel Ch_JT.

[0078] (2) The master base station 2-1 calculates the amount of data (= the calculated amount of data d 11 ~d 1q1 ) and distributes the transmission data to the slave base stations via the backhaul 4 and the switch 1 in parallel with (1).

[0079] (3) The master base station 2-1 and the slave base station perform the transmission frame generation process in parallel with the "transmission of padding PD" in (1).

[0080] Then, when the padding time ends, the master base station 2-1 and the q1 slave base stations simultaneously transmit transmission frames to the wireless device 4-1 by wireless communication using the channel Ch_JT.

[0081] The transmission timing is the timing at which the transmission frame is transmitted to the wireless device 4-1, and the notification of the transmission timing is the notification of the timing at which the transmission frame is transmitted to the wireless device 4-1.

[0082] When the above steps (1) to (3) are executed, the master base station 2-1 and the q1 slave base stations simultaneously transmit a transmission frame including transmission data to the wireless device 4-1 by wireless communication using the channel Ch_JT.

[0083] Thereafter, the master base station 2-1 receives a block Ack from the wireless device 4-1, which sends a block Ack to acknowledge reception of the frames.

[0084] On the other hand, when the master base station 2-1 determines that the joint transmission JT cannot be started, or when it determines that the joint transmission JT can be started and sends a joint transmission JT execution notification E X-NOTF is received, and the joint transmission JT's occupancy time T OCCUPY If it is determined that the value is within the predetermined range, the following (A) or (B) is executed.

[0085] (A) The master base station 2-1 transmits a transmission frame F_trsm including transmission data D_trsm to the wireless device 4-1 by wireless communication using the channel Ch_JT.

[0086] (B) The master base station 2-1 does not transmit the transmission frame F_trsm including the transmission data D_trsm to the wireless device 4-1.

[0087] The n1 slave base stations 3-11 to 3-1n1 receive the RTS transmitted by the master base station 2-1 via wireless communication using the channel Ch_JT from the master base station 2-1.

[0088] Furthermore, the n1 slave base stations 3-11 to 3-1n1 receive the start possibility confirmation frame FS_PB of the joint transmission JT transmitted by the master base station 2-1 via wireless communication using the channel Ch_JT.

[0089] Then, in response to receiving the start possibility confirmation frame FS_PB, each of the n1 slave base stations 3-11 to 3-1n1 determines whether or not joint transmission JT with the master base station 2-1 is possible.

[0090] When joint transmission JT with the master base station 2-1 is possible, each of the n1 slave base stations 3-11 to 3-1n1 transmits a start permission / prohibition response frame FRSP including "JT_OK" to the master base station 2-1 by wireless communication using the channel Ch_JT.

[0091] On the other hand, when joint transmission JT with the master base station 2-1 is not possible, each of the n1 slave base stations 3-11 to 3-1n1 transmits a start permission / prohibition response frame FRSP including "JT_NG" to the master base station 2-1 via wireless communication using channel Ch_JT.

[0092] However, if each of the n1 slave base stations 3-11 to 3-1n1 cannot transmit the initiation permission / rejection response frame FRSP (for example, when it is in communication with a radio device other than the master base station 2-1), it may not transmit the initiation permission / rejection response frame FRSP to the master base station 2-1. In this case, the master base station 2-1 determines that joint transmission JT is not possible for the slave base stations from which it did not receive the initiation permission / rejection response frame FRSP.

[0093] The q1 slave base stations 3-11 to 3-1q1 that have transmitted the start permission / prohibition response frame FRSP containing "JT_OK" to the master base station 2-1 receive the data amount d 11 ~d 1q1 After calculating, the following steps (4) to (6) are executed.

[0094] (4) Each of the q1 slave base stations receives notification of the transmission timing from the master base station 2-1 via wireless communication using channel Ch_JT.

[0095] (5) Each of the q1 slave base stations receives transmission data from the master base station 2-1 via the backhaul 4 and the switch 1 in parallel with (4).

[0096] (6) Each of the q1 slave base stations performs a transmission frame generation process in parallel with (4).

[0097] Here, (4) is executed in response to the above-mentioned "(1) The master base station 2-1 transmits, to q slave base stations, notification of the transmission timing and padding PD having a length consisting of the padding time by wireless communication using the channel Ch_JT." Also, (5) is executed in response to the above-mentioned "(2) The master base station 2-1 calculates the data amount (= the calculated data amount d 11 ~d 1q1 ) is executed in parallel with (1)." Furthermore, (6) is executed in response to the above-mentioned "(3) The master base station 2-1 and the q1 slave base stations perform transmission frame generation processing in parallel with transmitting the padding in (1)."

[0098] Thereafter, each of the q1 slave base stations transmits a transmission frame to the wireless device 4-1 simultaneously with the master base station 2-1 through wireless communication using channel Ch_JT.

[0099] The wireless device 4-1 receives an RTS from the master base station 2-1 through wireless communication using the channel Ch_JT, and then transmits a CTS to the master base station 2-1 through wireless communication using the channel Ch_JT.

[0100] Thereafter, when joint transmission JT is possible, the wireless device 4-1 receives (q1+1) transmission frames from the master base station 2-1 and the q1 slave base stations by wireless communication using the channel Ch_JT.

[0101] Then, the wireless device 4-1 transmits a Block Ack to the master base station 2-1 by wireless communication using the channel Ch_JT.

[0102] On the other hand, when the wireless device 4-1 is unable to start the joint transmission JT, it receives a transmission frame F_trsm including transmission data D_trsm only from the master base station 2-1 by wireless communication using the channel Ch_JT.

[0103] Then, the wireless device 4-1 transmits a Block Ack to the master base station 2-1 by wireless communication using the channel Ch_JT.

[0104] When joint transmission JT is not possible, the wireless device 4-1 may not receive the transmission data frame F_trsm containing the transmission data D_trsm from only the master base station 2-1.

[0105] [master base station 2-2, slave base stations 3-21 to 3-2n2, and wireless device 4-2] to [master base station 2-m, slave base stations 3-m1 to 3-mn m and wireless device 4-m] is the same as the above description of [master base station 2-1, slave base stations 3-11 to 3-1n1, and wireless device 4-1].

[0106] Fig. 2 is a schematic diagram of the master base station 2-1 shown in Fig. 1. Referring to Fig. 2, the master base station 2-1 includes an antenna 11, a receiving unit 12, a control unit 13, a wireless unit 14, generating units 15 and 16, a wired unit 17, and a calculation unit 18.

[0107] The receiving unit 12 receives the transmission data D_trsm addressed to the wireless device 4-1 via the network, and outputs the received transmission data D_trsm to the control unit 13.

[0108] The control unit 13 transmits and receives a beacon to a plurality of slave base stations, and designates Q (Q is an integer equal to or greater than 1) slave base stations from which the beacon can be received as candidates for n1 slave base stations 3-11 to 3-1n1.

[0109] The control unit 13 then holds the MAC addresses of the Q slave base stations in advance.

[0110] The MAC addresses of the Q slave base stations are shown in Table 1.

[0111] [Table 1]

[0112] In Table 1, MAC addresses Add_MAC_1 to Add_MAC_Q are assigned at timing t 1_CAD are the MAC addresses of the slave base stations that are candidates for the n1 slave base stations 3-11 to 3-1n1, and the MAC addresses Add_MAC_1' to Add_MAC_Q' are 2_CAD are the MAC addresses of the slave base stations that are candidates for the n1 slave base stations 3-11 to 3-1n1, and the MAC addresses Add_MAC_Q" to Add_MAC_Q" are 3_CAD are the MAC addresses of the slave base stations that are candidates for n1 slave base stations 3-11 to 3-1n1.

[0113] In this way, the control unit 13 performs the process at the timing t before forming the cooperating base station group that transmits the transmission data to the wireless device 4-1 by the joint transmission JT. 1_CAD In the base station, a beacon is transmitted and received to and from a plurality of slave base stations to obtain Q MAC addresses Add_MAC_1 to Add_MAC_Q, and the obtained Q MAC addresses Add_MAC_1 to Add_MAC_Q are stored.

[0114] When the control unit 13 transmits the transmission data D_trsm to the wireless device 4-1 by joint transmission JT, it detects n1 MAC addresses from the Q MAC addresses Add_MAC_1 to Add_MAC_Q, and forms an associated base station group AP_G1 with the master base station 2-1 and n1 slave base stations 3-1 to 3-1n1 that respectively have the detected n1 MAC addresses.

[0115] Then, the master base station 2-1 transmits the transmission data D_trsm to the wireless device 4-1 by joint transmission JT with q1 slave base stations that are capable of joint transmission JT among the n1 slave base stations 3-1 to 3-1n1.

[0116] Then, when the transmission of the transmission data D_trsm to the wireless device 4-1 is completed, the master base station 2-1 disbands the associated base station group AP_G1.

[0117] Thereafter, the master base station 2-1 receives the 2_CAD In the base station, a beacon is transmitted and received to and from a plurality of slave base stations to obtain Q' MAC addresses Add_MAC_1' to Add_MAC_Q', and the obtained Q' MAC addresses Add_MAC_1' to Add_MAC_Q' are stored.

[0118] When the master base station 2-1 transmits transmission data D_trsm to the wireless device 4-1 by joint transmission JT, it detects n1 MAC addresses from the Q' MAC addresses Add_MAC_1' to Add_MAC_Q', and forms an associated base station group AP_G1 together with n1 slave base stations 3-1 to 3-1n1 that respectively have the detected n1 MAC addresses.

[0119] Then, the master base station 2-1 transmits the transmission data D_trsm to the wireless device 4-1 by joint transmission JT with q1 slave base stations that are capable of joint transmission JT among the n1 slave base stations 3-1 to 3-1n1.

[0120] Then, when the transmission of the transmission data D_trsm to the wireless device 4-1 is completed, the master base station 2-1 disbands the associated base station group AP_G1.

[0121] Thereafter, the master base station 2-1 receives the 3_CAD In the base station, a beacon is transmitted and received to and from a plurality of slave base stations to obtain Q″ MAC addresses Add_MAC_1″ to Add_MAC_Q″, and the obtained Q″ MAC addresses Add_MAC_1″ to Add_MAC_Q″ are stored.

[0122] When the master base station 2-1 transmits transmission data D_trsm to the wireless device 4-1 by joint transmission JT, it detects n1 MAC addresses from the Q″ MAC addresses Add_MAC_1″ to Add_MAC_Q″, and forms an associated base station group AP_G1 together with n1 slave base stations 3-1 to 3-1n1 that respectively have the detected n1 MAC addresses.

[0123] Then, the master base station 2-1 transmits the transmission data D_trsm to the wireless device 4-1 by joint transmission JT with q1 slave base stations that are capable of joint transmission JT among the n1 slave base stations 3-1 to 3-1n1.

[0124] Then, when the transmission of the transmission data D_trsm to the wireless device 4-1 is completed, the master base station 2-1 disbands the associated base station group AP_G1.

[0125] Thereafter, the master base station 2-1 repeatedly executes the above-mentioned operations.

[0126] Therefore, the n1 slave base stations 3-11 to 3-1n1 may be different or the same each time a joint transmission JT is executed.

[0127] When the control unit 13 receives the transmission data D_trsm from the receiving unit 12, it outputs an RTS to the wireless unit 14 and controls the wireless unit 14 to transmit the RTS to n1 slave base stations 3-11 to 3-1n1 and the wireless device 4-1 via wireless communication using the channel Ch_JT.

[0128] Thereafter, upon receiving a CTS from the wireless unit 14, the control unit 13 generates a start permission / prohibition confirmation frame FS_PB. Then, the control unit 13 outputs the start permission / prohibition confirmation frame FS_PB to the wireless unit 14, and controls the wireless unit 14 to transmit the start permission / prohibition confirmation frame FS_PB to n1 slave base stations 3-11 to 3-1n1 by wireless communication using the channel Ch_JT.

[0129] The control unit 13 outputs the start possibility confirmation frame FS_PB to the wireless unit 14, and then receives n1 start possibility response frames FRSP from the wireless unit 14. Then, the control unit 13 determines whether or not it is possible to start the joint transmission JT based on the n1 start possibility response frames FRSP.

[0130] In this case, the control unit 13 determines that the joint transmission JT can be started when q1 of the n1 start permission response frames FRSP include "JT_OK." That is, the control unit 13 determines that the joint transmission JT can be started with q1 of the n1 slave base stations 3-11 to 3-1n1 (at least one of the n1 slave base stations 3-11 to 3-1n1).

[0131] On the other hand, when all of the n1 start permission / prohibition response frames FRSP contain "JT_NG", the control unit 13 determines that the start of the joint transmission JT is impossible.

[0132] The control unit 13 issues a notification E of execution of the joint transmission JT. X-NOTFWhen the master base station of the cooperating base station group other than the cooperating base station group AP_G1 receives the execution notification E of the joint transmission JT, X-NOTF to the control unit 13.

[0133] Then, when the control unit 13 determines that the joint transmission JT can be started, it sends a joint transmission JT execution notification E X-NOTF In this case, the control unit 13 determines whether or not the execution notification E of the joint transmission JT has been received from the wired unit 17. X-NOTF When receiving the JT execution notification E X-NOTF and determines that the wired unit 17 has received the execution notification E of the joint transmission JT. X-NOTF If you do not receive the JT execution notice E X-NOTF It is determined that the received signal was not received.

[0134] Then, the control unit 13 issues a notification E of execution of the joint transmission JT. X-NOTF When it is determined that the joint transmission JT has been received, it is determined whether or not the joint transmission JT can be executed.

[0135] In this case, the control unit 13 issues a notification E of execution of the joint transmission JT. X-NOTF It is determined that the joint transmission JT has been received and the occupancy time T OCCUPY When it is determined that the notification is not within the time limit, or when the execution notification E of the joint transmission JT is X-NOTF When it is determined that the joint transmission JT has not been received, it is determined that the joint transmission JT can be executed.

[0136] When the control unit 13 determines that the joint transmission JT can be executed, it selects q1 addresses Add1 to Add2 of q1 slave base stations that can start the joint transmission JT with the master base station 2-1. q1 Based on the above, q1 slave base stations have q1 wireless transmission rates r1 to r q1 Detect.

[0137] In this case, the control unit 13 calculates n1 wireless transmission rates r1 to rn1 of the n1 slave base stations 3-11 to 3-1n1. n1 The n1 addresses Add1 to Add2 of the n1 slave base stations 3-11 to 3-1n1 are respectively n1 The timer is also built in.

[0138] Then, the control unit 13 refers to the correspondence table TBL and selects q1 addresses Add1 to Add2 of q1 slave base stations that can start joint transmission JT with the master base station 2-1. q1 Based on the above, q1 slave base stations have q1 wireless transmission rates r1 to r q1 Detect.

[0139] Thereafter, the control unit 13 calculates the transmission data D_trsm and the q1 wireless transmission rates r1 to r q1 to the generation unit 15, and the data amount D of the transmission data D_trsm and the q1 wireless transmission rates r1 to r q1 The amount of data d to be allocated to the master base station 2-1 based on mst and the amount of data d1 to d2 to be distributed to q1 slave base stations. q1 Calculate the data volume d mst The transmission data d of the master base station 2-1 having mst_trsm and data volume d1~d q1 q1 transmission data d 1_trsm ~d q1_trsm and the transmission data d of the master base station 2-1 is generated. mst_trsm to the generating unit 16, and q1 transmission data d 1_trsm ~d q1_trsm to the control unit 13.

[0140] Thereafter, the control unit 13 receives q1 pieces of transmission data d 1_trsm ~d q1_trsm When the data amount d1 to d2 is received from the generating unit 15, q1 data amounts d1 to d2 are generated. q1 , q1 transmission rates S1 to Sq1 , q1 transmission frame generation processing time t 1_F ~t q1_F , transmission time T and SIFS time T SIFS to the arithmetic unit 18, and the minimum required padding time T padding_nd Calculate the minimum required padding time T padding_nd to the control unit 13.

[0141] The control unit 13 calculates the transmission data D_trsm and q1 wireless transmission rates r1 to r q1 to the generation unit 15, and then the q1 transmission data d 1_trsm ~d q1_trsm When the data amount d1 to d2 is received from the generating unit 15, q1 to the arithmetic unit 18, and i The joint transmission JT's occupancy time T occupy(i) Calculate the joint transmission JT's occupancy time T occupy(i) to the control unit 13.

[0142] Then, the control unit 13 determines the occupation time T occupy(i) When the calculation unit 18 receives the occupancy time T occupy(i) Joint transmission of JT execution notice E including X-NOTF and generates the execution notification E of the generated joint transmission JT. X-NOTF to the wired unit 17, and the execution notification E of the joint transmission JT X-NOTF The base station group AP_G i The wired unit 17 is controlled so as to transmit to the master base station and the slave base station of the other cooperating base station group.

[0143] Then, the control unit 13 determines the minimum required padding time T padding_nd When the signal is received from the calculation unit 18, a notification of the transmission timing is generated, and the generated notification of the transmission timing and the required minimum padding time T padding_ndto the wireless unit 14, and notifies the transmission timing and the necessary minimum padding time T padding_nd The wireless unit 14 is controlled so as to transmit the signal to the q1 slave base stations.

[0144] The control unit 13 also receives q1 pieces of transmission data d 1_trsm ~d q1_trsm to the wired unit 17, and q1 pieces of transmission data d 1_trsm ~d q1_trsm The wired unit 17 is controlled so that the signals are transmitted to the q1 slave base stations 3-11 to 3-1q1.

[0145] Furthermore, the control unit 13 receives the transmission data d of the master base station 2-1 from the generation unit 15. mst_trsm The master base station 2-1 transmits a frame F based on mst_trsm and the generated transmission frame F mst_trsm to the radio unit 14.

[0146] Thereafter, the control unit 13 refers to the timer and when the transmission timing arrives, the control unit 13 transmits the transmission frame F mst_trsm The instruction signal S ISTR to the wireless unit 14, and the transmission frame F of the master base station 2-1 received from the generation unit 16 is transmitted by wireless communication using the channel Ch_JT. mst_trsm to the wireless device 4-1.

[0147] The control unit 13 outputs an instruction signal S ISTR to the wireless unit 14, and then receives a Block Ack from the wireless unit 14. The wireless device 4-1 then transmits a transmission frame F mst_trsm ,F 1_trsm ~F q1_trsm Detects that a message has been received.

[0148] On the other hand, when the control unit 13 determines that joint transmission JT between the master base station 2-1 and q1 slave base stations is not possible, it outputs the transmission data D_trsm to the generation unit 16, generates a transmission frame F_trsm including the transmission data D_trsm, and controls the generation unit 16 to output the generated transmission frame F_trsm to the wireless unit 14.

[0149] Then, the control unit 13 receives a Block Ack from the wireless unit 14 and detects that the wireless device 4-1 has received the transmission frame F_trsm transmitted only by the master base station 2-1.

[0150] If the control unit 13 determines that joint transmission JT between the master base station 2-1 and the q1 slave base stations is not possible and does not transmit the transmission data D_trsm to the wireless device 3, it discards the transmission data D_trsm.

[0151] When the wireless unit 14 receives the RTS from the control unit 13, it transmits the RTS via the antenna 11 to the n1 slave base stations 3-11 to 3-1n1 and the wireless device 4-1 by wireless communication using the channel Ch_JT.

[0152] Furthermore, the wireless unit 14 receives a CTS from the wireless device 4-1 via the antenna 11 by wireless communication using the channel Ch_JT, and outputs the received CTS to the control unit 13.

[0153] Thereafter, when the wireless unit 14 receives the start permission confirmation frame FS_PB from the control unit 13, it transmits the start permission confirmation frame FS_PB via the antenna 11 to n1 slave base stations 3-11 to 3-1n1 by wireless communication using the channel Ch_JT.

[0154] Then, the wireless unit 14 receives n1 start possibility response frames FRSP from the n1 slave base stations 3-11 to 3-1n1 via the antenna 11 by wireless communication using the channel Ch_JT, and outputs the received n1 start possibility response frames FRSP to the control unit 13.

[0155] Furthermore, when the radio unit 14 receives a notification of the transmission timing from the control unit 13, it transmits the notification of the transmission timing to the q1 slave base stations via the antenna 11 by radio communication using the channel Ch_JT.

[0156] The radio unit 14 then transmits an instruction signal S ISTR from the control unit 13, and transmits the frame F mst_trsm from the generating unit 16, an instruction signal S ISTR In response to the signal, a transmission frame F is transmitted via the antenna 11 by wireless communication using the channel Ch_JT. mst_trsm to the wireless device 4-1.

[0157] The wireless unit 14 transmits a transmission frame F mst_trsm After transmitting the Block Ack, the control unit 13 receives a Block Ack from the wireless device 4-1 by wireless communication using the channel Ch_JT and outputs the received Block Ack to the control unit 13.

[0158] Furthermore, when joint transmission JT is not possible and only the master base station 2-1 transmits transmission data D_trsm to the wireless device 4-1, the wireless unit 14 transmits a transmission frame F mst_trsm from the generating unit 16.

[0159] Then, the wireless unit 14 transmits a transmission frame F via the antenna 11 by wireless communication using the channel Ch_JT. mst_trsm to the wireless device 4-1.

[0160] The generation unit 15 calculates the data amount D of the transmission data D_trsm, the wireless transmission rate r1 of the master base station 2-1, and the wireless transmission rates r 1,1 ~r 1,q1 is received from the control unit 13.

[0161] The generation unit 15 then calculates the data amount D of the transmission data D_trsm, the wireless transmission rate r1 of the master base station 2-1, and the wireless transmission rates r 1,1 ~r 1,q1 Substituting this into equation (1) gives the data volume d 1,j The calculation is performed for all j=1 to q1, and the amount of data d 1,1 ~d 1,q1 Calculate.

[0162]

number

[0163] In formula (1A), d i,j is the data length (=data volume) allocated to the jth slave base station in the ith cooperating base station group, and r i,j is the wireless transmission rate of the jth slave base station in the ith cooperating base station group (= the wireless transmission rate of the transmission data at the jth slave base station for which the data amount is to be calculated), and R i is represented by formula (1B), and D i is the total amount of data to be transmitted to the wireless device 4-i. i is the wireless transmission rate of the transmission data of the master base station 2-i in the i-th cooperating base station group, and r i,j is set B i is the wireless transmission rate of the transmission data of the jth slave base station in the ith cooperating base station group capable of joint transmission JT included in i is the wireless transmission rate r of the master base station 2-i in the i-th cooperating base station group. i and the sum of the wireless transmission rates of all slave base stations capable of joint transmission JT.

[0164] Furthermore, in equation (1), if all of the n1 slave base stations 3-11 to 3-1n1 are capable of performing joint transmission JT, the set B1 in equation (1) is B1={jεN|1≦j≦n1}.

[0165] On the other hand, in equation (1), if q1 slave base stations among n1 slave base stations 3-11 to 3-1n1 are capable of performing joint transmission JT, the set B1 in equation (1) is B1={j∈N|1≦j≦q1}.

[0166] According to equation (1), the generation unit 15 of the master base station 2-i calculates the amount of data d i,j The i-th cooperative base station group AP_G i The transmission data d at the slave base station j i,j_trsm Wireless transmission speed r i,j and the transmission data d mst_trsm Wireless transmission speed r i and q i q at slave base stations i Wireless transmission speed r1~r qi (or n i n slave base stations i wireless transmission rate r 1,1 ~r 1,ni ) and the sum R i The data volume d of the slave base station for which the data volume is to be calculated is inversely proportional to i,j Calculate.

[0167] That is, the generation unit 15 of the master base station 2-i generates the wireless transmission rate r i,j The largest amount of data is allocated to the slave base station with the fastest wireless transmission speed r i,j The second-largest amount of data is assigned to the slave base station with the second-fastest wireless transmission rate, r i,j The second slowest slave base station is assigned the second smallest amount of data, and the wireless transmission rate r i,jThe slowest slave base station is assigned the least amount of data.

[0168] The generation unit 15 generates q1 data amounts d1 to d for all q1 slave base stations by using the formula (1). q1 When calculating, the amount of data d1 to d q1 Sum of (=d1+d2+···+d q1 ) and add it to the total data volume D (= d1 + d2 + + d q1 ) to obtain the data volume d of the master base station 2-1. mst (=D-(d1+d2+···+d q1 Then, the generation unit 15 calculates the calculated data amounts d1 to d q1 ,d mst (=(q1+1) data amount d1~d q1+1 ) based on the transmission data d mst_trsm and q1 transmission data d from q1 slave base stations 1_trsm ~d q1_trsm and generate.

[0169] Then, the generation unit 15 generates q1 pieces of transmission data d 1_trsm ~d q1_trsm to the control unit 13, and the transmission data d mst_trsm to the generation unit 16.

[0170] The generating unit 16 generates the transmission data d mst_trsm The generating unit 16 receives the transmission data d mst_trsm Transmit frame F based on mst_trsm and the generated transmission frame F mst_trsm is output to the wireless unit 14.

[0171] Furthermore, when joint transmission JT between the master base station 2-1 and the q1 slave base stations is not possible, the generation unit 16 receives transmission data D_trsm from the control unit 13. Then, the generation unit 16 generates a transmission frame F_trsm based on the transmission data D_trsm and outputs the generated transmission frame F_trsm to the wireless unit 14.

[0172] The wired unit 17 is connected to the backhaul 4. The wired unit 17 then transmits, via the backhaul 4 and the switch 1, a notification E of execution of the joint transmission JT. X-NOTF from the master base station of another cooperating base station group (= at least one of the master base stations 2-2 to 2-m), the execution notification E of the received joint transmission JT X-NOTF to the control unit 13, and the control unit 13 outputs the execution notification E of the joint transmission JT. X-NOTF Upon receiving the JT, the execution notification E of the joint transmission JT is sent to other cooperating base stations via the backhaul 4 and the switch 1. X-NOTF and transmit q1 pieces of data d 1_trsm ~d q1_trsm When the control unit 13 receives q1 pieces of transmission data d 1_trsm ~d q1_trsm are transmitted to q1 slave base stations, respectively.

[0173] The calculation unit 18 calculates q1 pieces of data d1 to d q1 , q1 transmission frame generation processing time t 1_F ~t q1_F , the transmission time T and SIFS time T of the transmission timing notification SIFS from the control unit 13, the minimum required padding time T padding_nd Calculate the padding time T padding_nd is output to the control unit 13.

[0174] Fig. 3 is a conceptual diagram showing information held in advance by control unit 13. Referring to Fig. 3, control unit 13 holds basic information B_info in advance. The basic information B_info is basic information used when calculating the padding time.

[0175] The basic information B_info is the link capacity s i , the transmission frame generation processing time, the transmission time T, and the SIFS time T SIFS Includes:

[0176] Address Add1~Add n1 are the addresses of the slave base stations 3-11 to 3-1n1, respectively, and the transmission frame generation processing time t 1_F ~t n1_F are associated with the following:

[0177] Link capacity s i is the link capacity of the master base station in the i-th cooperating base station group.

[0178] In addition, the transmission frame generation processing time t 1_F is the processing time for generating a transmission frame in the slave base station 3-11 having the address Add1, and the processing time for generating a transmission frame t 2_F is the processing time for generating a transmission frame in the slave base station 3-12 having the address Add2, and similarly, the processing time for generating a transmission frame t n1_F Add the address n1 1. This is the processing time required to generate a transmission frame in the slave base station 3-1n1 having the above-mentioned sine wave number.

[0179] Then, the transmission frame generation processing time t 1_F ~t n1_F are addresses Add1 to Add n1 can be associated with

[0180] Furthermore, the transmission time T is the transmission time for the notification of the transmission timing transmitted from the master base station 2-1 to each of the n1 slave base stations 3-11 to 3-1n1.

[0181] Furthermore, the SIFS time T SIFS is the time length of the SIFS.

[0182] The processing time for generating n1 transmission frames is t1_F ~t n1_F Each of the time slots includes a signaling delay time. SIFS is a value specified in IEEE802.11.

[0183] The control unit 13 calculates the transmission data d to be distributed to the q1 slave base stations 3-11 to 3-1q1. 1_trsm ~d q1_trsm The amount of data d1~d q1 from the generation unit 15. Then, the control unit 13 detects the link capacity s1 of the master base station from the basic information B_info.

[0184] In addition, the control unit 13 sets q1 addresses Add1 to Add q1 The processing time t for generating q transmission frames is 1_F ~t q1_F is detected from the basic information B_info. Here, the processing time for generating q1 transmission frames is t 1_F ~t q1_F Each of these is the transmission frame generation processing time t 1_F ~t n1_F It consists of either:

[0185] Furthermore, the control unit 13 detects the transmission time T from the basic information B_info.

[0186] Furthermore, the control unit 13 determines the SIFS time T SIFS is detected from the basic information B_info.

[0187] Then, the control unit 13 receives q1 pieces of data d1 to d q1 , link capacity s i , q1 transmission frame generation processing time t 1_F ~t q1_F , transmission time T and SIFS time T SIFS to the arithmetic unit 18, and the minimum required padding time T padding_nd The calculation unit 18 is controlled to calculate the following.

[0188] Padding time T padding_nd The calculation unit 18 calculates the amount of data d1 to d q1 , link capacity s i , q1 transmission frame generation processing time t 1_F ~t q1_F , transmission time T and SIFS time T SIFS is received from the control unit 13.

[0189] Then, the calculation unit 18 calculates the q1 data amounts d1 to d q1 , link capacity s1, q1 transmission frame generation processing time t 1_F ~t q1_F , transmission time T and SIFS time T SIFS Based on this, the minimum required padding time T padding(1) Calculate.

[0190] In this case, the calculation unit 18 calculates the amount of data d 1,j (j is one of 1 to q1), link capacity s1, transmission frame generation processing time t j_F , transmission time T and SIFS time T SIFS Substituting into equation (2) gives the padding time T padding(1)_j Calculation is performed for all j=1 to q1 to obtain q1 padding times T padding(1)_1 ~T padding(1)_q1 Calculate the padding time T padding(1)_1 ~T padding(1)_q1 The maximum value of the coordinated base station group AP_G i Padding time T padding(1) It is calculated as follows.

[0191]

number

[0192] In equation (2), d i,j is the i-th cooperating base station group AP_G i is the amount of data allocated to the j-th slave base station in si,j is the i-th cooperating base station group AP_G i is the transmission rate of data distribution communication between the master base station 2-i and the j-th slave base station on the backhaul 4, and t i,j is the i-th cooperating base station group AP_G i is the transmission frame generation processing time in the j-th slave base station in the time domain, T is the transmission time of the notification of the transmission timing transmitted from the master base station 2-i to each slave base station, and T SIFS is the SIFS time, and T padding(i) is the i-th cooperating base station group AP_G i is the padding time in

[0193] Note that the padding time T padding(1)_1 ~T padding(1)_q1 Each of these is the length of the padding PD, which consists of a fixed value.

[0194] s in equation (2) i,j is expressed by the following equation:

[0195]

number

[0196] In equation (3), s i is the transmission rate of the backhaul 4 of the i-th cooperative base station group, and q _i is the number of slave base stations cooperating in the i-th cooperating base station group. As a result, the i-th cooperating base station group AP_G i The transmission rate s of the data distribution communication between the master base station 2-i and the j-th slave base station on the backhaul 4 i,j is the transmission rate s of the backhaul 4 of the i-th cooperative base station group i Let q be the number of slave base stations in the i-th cooperative base station group. i The average transmission rate s i It consists of the average value of

[0197] In equation (2), the transmission rate si The transmission rate s i,j Using this, in the i-th cooperative base station group, q i padding time T padding(i)_1 ~T padding(i)_qi is calculated.

[0198] In this case, q i padding time T padding(i)_1 ~T padding(i)_qi When calculating, s in equation (2) i,j is the transmission speed s i The data volume d i,j is different for each slave base station j, so q i padding time T padding(i)_1 ~T padding(i)_qi are q i Amount of data d i,1 ~d i,qi and padding time proportional to q i Amount of data d i,1 ~d i,qi The maximum value of the i-th cooperative base station group AP_G i Padding time T padding(i) This becomes:

[0199] Therefore, the largest amount of data d i,j_max The slave base station that transmits the transmission data of the i-th cooperating base station group AP_G takes the longest time to receive the transmission data from the master base station i. i The padding time T of the slave base station in padding(i) is the largest amount of data d i,j_max The amount of data d transmitted by the slave base station i,j_max Since it is calculated to be proportional to the i-th cooperated base station group AP_G i All slave base stations in padding(i) By the time the padding time T padding(i) When the transmission is completed, the transmission data can be sent to the wireless device at the same time.

[0200] In equation (2), if all of the n1 slave base stations 3-11 to 3-1n1 can perform joint transmission JT, B1 in equation (2) is B1={j∈N|1≦j≦n1}. As a result, the calculation unit 18 calculates n1 padding times T padding(1)_1 ~T padding(1)_n1 Calculate the n1 padding times T padding(1)_1 ~T padding(1)_n1 The maximum value of the padding time T padding(1) Calculate.

[0201] On the other hand, in equation (2), if q1 slave base stations among n1 slave base stations 3-11 to 3-1n1 can perform joint transmission JT, then B in equation (2) i As a result, the calculation unit 18 calculates q1 padding times T padding(1)_1 ~T padding(1)_q1 Calculate the padding time T padding(1)_1 ~T padding(1)_q1 The maximum value of the coordinated base station group AP_G i Padding time T padding(1) Calculate.

[0202] Then, the calculation unit 18 calculates the padding time T padding(1) is output to the control unit 13.

[0203] In addition, in equation (2), the padding time T padding(1) T padding(1) If ≦0, the padding time T padding(1) =0.

[0204] In addition, in equation (2), the padding time T padding(1)_1 ~T padding(1)_q1 Among them, the maximum padding time T padding If there are multiple maximum padding times T padding Any one of the padding times T padding(1)The padding time T padding(1)_1 ~T padding(1)_n1 The same applies when is calculated.

[0205] The control unit 13 determines the padding time T padding(1) When the calculation unit 18 receives the notification of the transmission timing and the padding time T padding(1) and the padding time T padding(1) and padding PD having a length of q to q1 slave base stations.

[0206] The calculation unit 18 receives q1 pieces of data d1 to d q1 Receive the received q1 data amounts d1 to d q1 Based on equation (4), the occupancy time T of backhaul 4 in joint transmission JT is calculated. occupy(1) Calculate the occupied time T occupy(1) is output to the control unit 13.

[0207]

number

[0208] In equation (4), d i,j is the i-th cooperating base station group AP_G i is the amount of data allocated to the j-th slave base station 3-ij in s i,j is the i-th cooperating base station group AP_G i is the transmission rate of the backhaul 4 between the master base station 2-i and the j-th slave base station 3-ij.

[0209] The q1 slave base stations that have transmitted the start permission / prohibition response frame FRSP containing "JT-OK" to the master base station 2-1 are allocated data amounts d1 to d2 by the master base station 2-1 to the q1 slave base stations. q1 After calculating the above, the following steps (4A) to (6A) are executed.

[0210] (4A) Each of the q1 slave base stations receives padding time T from the master base station 2-1 by wireless communication using channel Ch_JT. padding(1) Receive a notification of the transmission timing with the attached .

[0211] (5A) Each of the q1 slave base stations receives transmission data from the master base station 2-1 via the backhaul 4 in parallel with the "reception of notification of transmission timing" of (4A).

[0212] (6A) Each of the q1 slave base stations executes the transmission frame generation process in parallel with the "reception of notification of transmission timing" of (4A).

[0213] Here, (4A) is executed in response to the above-mentioned "(1) The master base station 2-1 transmits, via wireless communication using channel Ch_JT, notification of transmission timing and a padding PD having a length consisting of the padding time to the q1 slave base stations." Also, (5A) is executed in response to the above-mentioned "(2) The master base station 2-1 transmits q1 pieces of transmission data, each having a data amount of q1, to the q1 slave base stations via the backhaul 4 and the switch 1, in parallel with the "transmission of padding PD" in (1)." Furthermore, (6A) is executed in response to the above-mentioned "(3) The master base station 2-1 and the q1 slave base stations perform a transmission data frame generation process in parallel with the "transmission of padding PD" in (1)."

[0214] 4 is a schematic diagram showing contention of joint transmission JT in a star-type backhaul. Referring to FIG. 4, the master base station 2-1 and slave base stations 3-11 and 3-12 in the cooperating base station group AP_G1 are directly connected to the switch 1 by the backhaul 4, and the master base station 2-2 and slave base stations 3-21 and 3-22 in the cooperating base station group AP_G2 are directly connected to the switch 1 by the backhaul 4.

[0215] Then, the master base station 2-1 of the associated base station group AP_G1 transmits transmission data to the switch 1 via the backhaul 4 at a transmission rate of 3.0 Gbps in data allocation to the slave base stations 3-11 and 3-12.

[0216] Furthermore, the master base station 2-2 of the cooperating base station group AP_G2 transmits transmission data to the switch 1 via the backhaul 4 at a transmission rate of 3.0 Gbps in data allocation to the slave base stations 3-21 and 3-22.

[0217] As a result, the sum of the transmission speeds of the data allocation traffic flowing from the master base stations 2-1 and 2-2 to the switch 1 becomes 6.0 Gbps, exceeding the switching capacity of the switch 1, which is 5.0 Gbps.

[0218] In this case, switch 1 transmits transmission data from master base station 2-1 to slave base stations 3-11 and 3-12 via backhaul 4 at a distribution speed of 1.25 Gbps, which is obtained by dividing the switching capacity of 5.0 Gbps by the total number of slave base stations (=4), and transmits transmission data from master base station 2-2 to slave base stations 3-21 and 3-22 via backhaul 4 at a distribution speed of 1.25 Gbps.

[0219] In this way, contention for joint transmission JT occurs when the sum of the capacities of data distribution traffic flowing from the master base stations 2-1 and 2-2 to the switch 1 (6 Gbps) exceeds the switching capacity of the switch 1 (5 Gbps).

[0220] 5 is a schematic diagram showing frame processing when a contention occurs in a joint transmission JT. Referring to FIG. 5, the master base station 2-1 of the cooperating base station group AP_G1 starts a process of generating a transmission frame at timing t3, and the slave base stations 3-11 and 3-12 start a process of generating a transmission frame at timing t4 after timing t3.

[0221] This is because, as explained in FIG. 4, the transmission speed of the data transmitted from the switch 1 to the slave base stations 3-11 and 3-12 when the joint transmission JT is executed is limited to 1.25 Gbps.

[0222] In this case, the master base station 2-1 starts transmitting the transmission frame PPDU0 to the wireless device 4-1 at timing t5, while the slave base stations 3-11 and 3-12 start transmitting the transmission frames PPDU1 and PPDU2 to the wireless device 4-1 at timing t6, which is later than timing t5.

[0223] As a result, the master base station 2-1A and the slave base stations 3-11 and 3-12 cannot simultaneously transmit the transmission frames PPDU0, PPDU1, and PPDU2 to the wireless device 4-1.

[0224] Therefore, the master base station 2-1 and the slave base stations 3-11 and 3-12 fail to execute the joint transmission JT.

[0225] Therefore, in embodiment 1, when a conflict occurs between the joint transmission JT by the cooperating base station group AP_G1 and the joint transmission JT by the cooperating base station group AP_G2, it is determined that the joint transmission JT cannot be executed without adjusting the transmission speed of the backhaul 4.

[0226] Fig. 6 is a schematic diagram of the slave base station 3-11 shown in Fig. 1. Referring to Fig. 6, the slave base station 3-11 includes an antenna 21, a wireless unit 22, a wired unit 23, a control unit 24, and a generation unit 25.

[0227] The radio unit 22 receives the RTS from the master base station 2-1 via the antenna 21 by radio communication using the channel Ch_JT, and outputs the received RTS to the control unit 24.

[0228] Furthermore, the wireless unit 22 receives the initiation permission confirmation frame FS_PB from the master base station 2-1 via the antenna 21 by wireless communication using the channel Ch_JT, and outputs the received initiation permission confirmation frame FS_PB to the control unit 24.

[0229] Thereafter, when the wireless unit 22 receives from the control unit 24 a start permission / non-permission response frame FRSP in response to the start permission / non-permission confirmation frame FS_PB, it transmits the start permission / non-permission response frame FRSP to the master base station 2-1 via the antenna 21 by wireless communication using the channel Ch_JT.

[0230] Furthermore, the radio unit 22 receives a notification of the transmission timing from the master base station 2-1 via the antenna 21 by radio communication using the channel Ch_JT, and outputs the received notification of the transmission timing to the control unit 24.

[0231] Furthermore, when the radio unit 22 receives the transmission frame from the control unit 24, it transmits the transmission frame F via the antenna 21 by radio communication using the channel Ch_JT. 1_trsm to the wireless device 4-1.

[0232] The wired unit 23 is connected to the backhaul 4. The wired unit 23 receives the transmission data d from the wired unit 17 of the master base station 2-1 via the backhaul 4. 1_trsm Receive the received transmission data d 1_trsm to the control unit 24.

[0233] The control unit 24 receives the RTS from the wireless unit 22. The control unit 24 also receives the start possibility confirmation frame FS_PB from the wireless unit 22. Then, the control unit 24 determines whether or not the slave base station 3-11 is capable of joint transmission JT with the master base station 2-1 in accordance with the start possibility confirmation frame FS_PB.

[0234] In this case, for example, if the slave base station 3-11 is conducting wireless communication with a wireless device other than the wireless device 4-1, the control unit 24 determines that the slave base station 3-11 is unable to conduct joint transmission JT with the master base station 2-1, and if the slave base station 3-11 is not conducting wireless communication with a wireless device other than the wireless device 4-1, the control unit 24 determines that the slave base station 3-11 is able to conduct joint transmission JT with the master base station 2-1.

[0235] Alternatively, whether joint transmission JT is possible may be determined by the following method: The radio unit 22 detects a received signal strength indicator (RSSI) when transmitting radio waves on channel Ch-JT via the antenna 21, and outputs the detected received signal strength RSSI to the control unit 24. When the received signal strength RSSI received from the radio unit 22 is equal to or less than a threshold RSSI_th (e.g., −83 dBm), the control unit 24 determines that no other radio communication is taking place and that joint transmission JT is possible. On the other hand, when the received signal strength RSSI is greater than the threshold RSSI_th, the control unit 24 determines that another radio communication is taking place and that joint transmission JT is not possible.

[0236] When the control unit 24 determines that joint transmission JT is possible, it generates a start permission / rejection response frame FRSP including "JT_OK."The control unit 24 then outputs the start permission / rejection response frame FRSP including "JT_OK" to the wireless unit 22, and controls the wireless unit 22 to transmit the start permission / rejection response frame FRSP including "JT_OK" to the master base station 2-1 by wireless communication using channel Ch_JT.

[0237] On the other hand, when the control unit 24 determines that joint transmission JT is not possible, it generates a start permission / rejection response frame FRSP including "JT_NG."The control unit 24 then outputs the start permission / rejection response frame FRSP including "JT_NG" to the wireless unit 22 and controls the wireless unit 22 to transmit the start permission / rejection response frame FRSP including "JT_NG" to the master base station 2-1 by wireless communication using channel Ch_JT.

[0238] The control unit 24 also receives notification of the transmission timing from the wireless unit 22 and transmits the transmission data d 1_trsm The control unit 24 receives the transmission data d 1_trsm to the generating unit 25, and the transmission data d 1_trsm The generating unit 25 is controlled to perform the frame generating process based on the above.

[0239] Thereafter, the control unit 24 receives the transmission data d 1_trsm A transmission frame F containing 1_trsm (PPDU1) is received from generation unit 25.

[0240] Then, when the transmission timing arrives, the control unit 24 sends the transmission data d 1_trsm A transmission frame F containing 1_trsm (PPDU1) to the wireless unit 22, and transmits a transmission frame F via wireless communication using the channel Ch_JT. 1_trsm The wireless unit 22 is controlled to transmit (PPDU1) to the wireless device 4-1.

[0241] The generating unit 25 generates the transmission data d 1_trsm When the control unit 24 receives the transmitted data d 1_trsm A transmission frame F containing 1_trsm A process for generating a transmission frame (PPDU1) is executed, and the generated transmission frame F 1_trsm (PPDU1) is output to the control unit 24.

[0242] Each of the slave base stations 3-12 to 3-1n1 shown in FIG. 1 has the same configuration as the slave base station 3-11 shown in FIG.

[0243] Fig. 7 is a schematic diagram of the wireless device 4-1 shown in Fig. 1. Referring to Fig. 7, the wireless device 4-1 includes an antenna 31, a wireless unit 32, a control unit 33, and an application .

[0244] The radio unit 32 receives the RTS from the master base station 2 - 1 via the antenna 31 by radio communication using the channel Ch_JT, and outputs the received RTS to the control unit 33 .

[0245] Thereafter, the wireless unit 32 receives the CTS from the control unit 33. Then, the wireless unit 32 transmits the CTS to the master base station 2-1 via the antenna 31 by wireless communication using the channel Ch_JT.

[0246] Further, the wireless unit 32 transmits a transmission frame F via the antenna 31 by wireless communication using the channel Ch_JT. mst_trsm ,F 1_trsm ~F q1_trsm (=(q1+1) transmission frames) are received from the master base station 2-1 and the q1 slave base stations, respectively, and the received transmission frames F mst_trsm ,F 1_trsm ~F q1_trsm (=(q1+1) transmission frames) to the control unit 33.

[0247] Thereafter, upon receiving the block Ack from the control unit 33, the radio unit 32 transmits the block Ack to the master base station 2-1 via the antenna 31 by radio communication using the channel Ch_JT.

[0248] Furthermore, when joint transmission JT is not possible, the radio unit 32 receives a transmission frame F_trsm (= a frame including transmission data D_trsm) from the master base station 2-1 via the antenna 31 by radio communication using the channel Ch_JT, and outputs the received transmission frame F_trsm (= a frame including transmission data D_trsm) to the control unit 33.

[0249] Thereafter, upon receiving the block Ack from the control unit 33, the radio unit 32 transmits the block Ack to the master base station 2-1 via the antenna 31 by radio communication using the channel Ch_JT.

[0250] The control unit 33 receives the RTS from the radio unit 32. Then, the control unit 33 receives from the radio unit 32 the received signal strength RSSI when radio waves are transmitted on the channel Ch-JT via the antenna 31, and when the received signal strength RSSI is equal to or less than the threshold RSSI_th, determines that no other radio communication is taking place, and when the received signal strength RSSI is greater than the threshold RSSI_th, determines that another radio communication is taking place.

[0251] When the control unit 33 determines that no other wireless communication is taking place, it outputs a CTS to the wireless unit 32 and controls the wireless unit 32 to transmit the CTS to the master base station 2-1 via wireless communication using the channel Ch_JT.

[0252] Thereafter, the control unit 33 transmits the transmission frame F mst_trsm ,F 1_trsm ~F q1_trsm (=(q1+1) transmission frames) from the wireless unit 32, mst_trsm ,F 1_trsm ~F q1_trsm (=(q1+1) transmission frames) and outputs the transmission data D_trsm to the application 34.

[0253] Subsequently, the control unit 33 outputs the block Ack to the radio unit 32 and controls the radio unit 32 to transmit the block Ack to the master base station 2-1 by radio communication using the channel Ch_JT.

[0254] Furthermore, when the control unit 33 receives a transmission frame F_trsm (=a frame including transmission data D_trsm) from the wireless unit 32, it decodes the transmission frame (=a frame including transmission data D_trsm) and outputs the transmission data D_trsm to the application .

[0255] Thereafter, the control unit 33 outputs the block Ack to the radio unit 32 and controls the radio unit 32 to transmit the block Ack to the master base station 2-1 by radio communication using the channel Ch_JT.

[0256] The application 34 receives the transmission data D_trsm from the control unit 33 .

[0257] The cooperating base station groups AP_G2 to AP_G shown in FIG. m The description of each of these is the same as the description of the associated base station group AP_G1 described above.

[0258] FIG. 8 is a conceptual diagram for explaining a method for generating transmission data in the master base station 2-1 and q1 slave base stations.

[0259] 8, the transmission data D_trsm has a data amount D. The generation unit 15 of the master base station 2-1 generates data amounts d1 to d2 to be allocated to the q1 slave base stations by the above-described method. q1 When the calculation is performed, the portion of the transmission data D_trsm with the data amount d1 is cut out from the beginning of the transmission data D_trsm, and the transmission data D 1_trsm Generate.

[0260] Next, the generating unit 15 cuts out a portion of the data amount d2 from the beginning of the transmission data D_trsm from which the data amount d1 has been cut out, and generates transmission data D_trsm having the data amount d2. 2_trsm Generate.

[0261] Furthermore, the generating unit 15 cuts out a portion of data amount d3 from the beginning of the transmission data D_trsm from which the data amount d1+d2 has been cut out, and generates transmission data D_trsm having the data amount d3. 3_trsm Generate.

[0262] Similarly, the generating unit 15 generates the data amount d1+d2+···+d q1-1 The amount of data d from the beginning of the cut transmission data D_trsm q1 Cut out the part and reduce the data volume d q1 Transmission data d having q1_trsm Generate.

[0263] Then, the generation unit 15 calculates the remaining data amount (=D-(d1+d2+···+d q1 )) transmission data d mst_trsm Generate.

[0264] Then, the generating unit 15 generates the transmission data d 1_trsm ~d q1_trsm are the transmission data to be transmitted to q1 slave base stations, and the transmission data d mst_trsm is the transmission data of the master base station 2-1.

[0265] Fig. 9 is a conceptual diagram showing the structure of a transmission frame. The transmission frame shown in Fig. 9 has the structure of a transmission frame in IEEE 802.11a.

[0266] Referring to FIG. 9, a transmission frame PPDU (PLCP Protocol Data Unit) includes RATE, Reserved, Length, Parity, Tail, Service, PSDU, Tail, and Padding.

[0267] RATE, Reserved, Length, Parity, Tail, and Service make up the PLCP Header.

[0268] The PSDU (PLCP Service Data Unit) follows the PLCP Header and is passed from the upper layer to the physical layer. PLCP stands for Physical Layer Convergence Protocol.

[0269] Since a bit-tailing convolutional code is used as the error correction code in the physical layer (PHY layer), tail bits are added after the PSDU in the physical layer (PHY layer).

[0270] The end of the packet is terminated with an OFDM (Orthogonal Frequency Division Multiplexing) symbol, so bits are padded as necessary.

[0271] The RATE, Reserved, Length, Parity, and Tail constitute the Signal, and the Service, PSDU, Tail, and Padding constitute the Data.

[0272] Therefore, the PPDU consists of a signal and data. When the master base station 2-1 generates a transmission frame, the transmission data d mst_trsm is stored in Data. When each of the q slave base stations generates a transmission frame, the transmission data d j_trsm (j=1 to q1) is stored in Data.

[0273] In the "transmission frame generation process," the master base station 2-1 generates a transmission frame F having the configuration shown in FIG. mst_trsm (=PPDU0) is generated.

[0274] In addition, the slave base station 3-11 generates a transmission frame F having the configuration shown in FIG. 1_trsm (=PPDU1), and the slave base station 3-12 generates a transmission frame F having the configuration shown in FIG. 2_trsm (=PPDU2) is generated.

[0275] That is, the master base station 2-1 receives the data amount d mst Transmit frame F based on mst_trsm The slave base station 3-11 then executes a transmission frame generation process to generate a transmission frame F (=PPDU0) based on the data amount d1. 1_trsm The transmission frame generation process is executed to generate a transmission frame (=PPDU1).

[0276] Fig. 10 is a schematic diagram showing frame processing in communication system 10 shown in Fig. 1. Note that Fig. 10 shows only slave base station 3-11 out of the q1 slave base stations.

[0277] Referring to FIG. 10, the master base station 2-1 transmits an RTS to the slave base station 3-11 and the wireless device 4-1 by wireless communication using the channel Ch_JT.

[0278] The slave base station 3-11 and the wireless device 4-1 then receive the RTS from the master base station 2-1 via wireless communication using the channel Ch_JT.

[0279] Thereafter, the wireless device 4-1 transmits a CTS to the master base station 2-1 by wireless communication using the channel Ch_JT.

[0280] Then, when the master base station 2-1 receives a CTS from the wireless device 4-1 via wireless communication using channel Ch_JT, it generates a start possibility confirmation frame FS_PB for the joint transmission JT and transmits the start possibility confirmation frame FS_PB to the slave base station 3-11 via wireless communication using channel Ch_JT.

[0281] When the slave base station 3-11 receives the initiation possibility confirmation frame FS_PB from the master base station 2-1 by wireless communication using channel Ch_JT, it determines whether joint transmission JT with the master base station 2-1 is possible. If the slave base station 3-11 determines that joint transmission JT with the master base station 2-1 is possible, it generates an initiation possibility response frame FRSP including "JT_OK", and if it determines that joint transmission JT with the master base station 2-1 is not possible, it generates an initiation possibility response frame FRSP including "JT_NG".

[0282] Then, the slave base station 3-11 transmits a start permission / prohibition response frame FRSP (a response frame FRSP including "JT_OK" or "JT_NG") in response to the start permission / prohibition confirm frame FS_PB to the master base station 2-1 by wireless communication using channel Ch_JT.

[0283] The master base station 2-1 receives the start permission / prohibition response frame FRSP from the slave base station 3-11 via wireless communication using the channel Ch_JT.

[0284] Then, when the master base station 2-1 determines that it is possible to start the joint transmission JT with the slave base station 3-11 based on the start permission response frame FRSP (response frame FRSP including "JT_OK"), it receives a joint transmission JT execution notification E from the master base station of another cooperating base station group. X-NOTF It is determined whether or not the message has been received.

[0285] Then, the master base station 2-1 issues a notification E of execution of the joint transmission JT. X-NOTF When it is determined that the JT has been received, the execution notification E of the joint transmission JT is X-NOTF The joint transmission JT occupancy time T OCCUPY ” and other cooperative base station groups’ “joint transmission JT’s occupancy time T OCCUPY It is determined whether the value is "within" the range.

[0286] The master base station 2-1 issues a joint transmission JT execution notification EX-NOTF When it is determined that the JT has not been received, or when the JT has been OCCUPY If it is determined that the data amount d is not within the range of 1 / 2, the data amount d to be distributed to the master base station 2-1 and the slave base station 3-11 is mst ,d 3-11 Calculate the padding time T padding(1) Calculate.

[0287] Then, the master base station 2-1 determines the occupied time T OCCUPY Execution notification E including X-NOTF to the master base station and the slave base station of the other cooperating base station group.

[0288] Thereafter, the master base station 2-1 executes the following steps (1) to (3).

[0289] (1) The master base station 2-1 transmits a "transmission timing notification" and a "padding PD consisting of padding time" to the slave base station 3-11 by wireless communication using the channel Ch_JT, and (2) the master base station 2-1 transmits the transmission data d 3-11_trsm (Data volume d 3-11 (3) the master base station 2-1 and the slave base station 3-11 perform a process of generating a transmission frame in parallel with the transmission of the padding PD in (1).

[0290] In this case, the above (2) is executed first, the above (1) is executed in parallel with (2), and after (2) is completed, the above (3) is executed in parallel with (1). As a result, the time required for the master base station 2-1 to allocate transmission data (2) partially overlaps with the time required for the transmission of the transmission timing notification (1), and the time required for the master base station 2-1 and the slave base station 3-11 to perform the transmission frame generation process (3) partially overlaps with the time required for the transmission of the transmission timing notification (1).

[0291] The allocation of transmission data in the master base station 2-1 (2) and the generation of transmission frames in the master base station 2-1 and slave base station 3-11 (3) are executed serially.

[0292] Here, (2) the master base station 2-1 transmits data d 1_trsm The allocation of (transmission data having a data amount d1) to the slave base station 3-11 is performed in parallel with (1). 1_trsm The time required to allocate (transmission data having a data amount d1) to the slave base station 3-11 and the time required to transmit the notification of the transmission timing in (1) overlap at least partially.

[0293] Furthermore, (3) the master base station 2-1 and the slave base station 3-11 perform the process of generating the transmission frame in parallel with the transmission of the padding PD in (1), which means that the time required for the process of generating the transmission frame and the time required for transmitting the padding PD in (1) overlap for at least a portion of the time length.

[0294] After the process of generating the transmission frame is completed, the master base station 2-1 and the slave base station 3-11 each transmit a transmission frame F by wireless communication using the channel Ch_JT in the joint transmission JT. mst_trsm (=PPDU0),F 1_trsm (=PPDU1) to the wireless device 4-1 at the same time.

[0295] Then, the wireless device 4-1 receives a transmission frame F from the master base station 2-1 by wireless communication using the channel Ch_JT. mst_trsm (=PPDU0) and receives the transmission frame F from the slave base station 3-11. 1_trsm Upon receiving (=PPDU1), the master base station 2-1 transmits a Block Ack to the master base station 2-1 by wireless communication using the channel Ch_JT.

[0296] Then, the master base station 2-1 receives a Block Ack from the wireless device 4-1 by wireless communication using the channel Ch_JT, and receives a transmission frame F transmitted by the wireless device 4-1 through joint transmission JT between the master base station 2-1 and the slave base station 3-11. mst_trsm (=PPDU0),F 1_trsm Detects that (=PPDU1) has been received.

[0297] Therefore, the master base station 2-1 transmits a "transmission timing notification" to the slave base station 3-11 and transmits the transmission data d via the backhaul 4. 1_trsm to the slave base station 3-11, and when the padding time ends, the master base station 2-1 and the slave base station 3-11 simultaneously transmit a transmission frame F mst_trsm (=PPDU0),F 1_trsm (=PPDU1) is transmitted to the wireless device 4-1.

[0298] In FIG. 10, the master base station 2-1 transmits an RTS to the slave base station 3-11 and the wireless device 4-1 at timing t1, and then receives a Block Ack from the wireless device 4-1 at timing t2.

[0299] As a result, the time required for data transmission from the master base station 2-1 and the slave base station 3-11 to the wireless device 4-1 is t2-t1.

[0300] Fig. 11 is a schematic diagram showing conventional frame processing. Referring to Fig. 11, in conventional frame processing, the master base station 2-1 transmits a notification of transmission timing to the slave base station 3-11 by wireless communication using channel Ch_JT, and then allocates transmission data by wireless communication, and thereafter the master base station 2-1 and the slave base station 3-11 perform processing to generate a transmission frame.

[0301] That is, in FIG. 11, the transmission of the notification of the transmission timing to the slave base station 3-11, the allocation of the transmission data, and the generation of the transmission frame are executed serially.

[0302] As a result, the master base station 2-1 and the slave base station 3-11 each transmit a transmission frame F, which is a frame of the physical layer (PHY layer), by wireless communication using the channel Ch_JT. mst_trsm (=PPDU0),F 1_trsm The timing at which the transmission of (=PPDU1) to the wireless device 4-1 is completed is timing t3.

[0303] Then, the master base station 2-1 receives a Block Ack from the wireless device 4-1 at timing t4, which is later than timing t3.

[0304] 11 is a timing that comes after the timing t2 at which the master base station 2-1 receives the Block Ack from the wireless device 4-1 in FIG.

[0305] 10, in communication system 10 according to the first embodiment, master base station 2-1 allocates transmission data to slave base stations 3-11 using backhaul 4 and switch 1, which reduces the amount of wireless resources used compared to allocating transmission data to slave base stations 3-11 by wireless communication, thereby improving throughput.

[0306] Furthermore, as shown in FIG. 10, in the communication system 10 according to the first embodiment, the master base station 2-1 allocates transmission data to the slave base station 3-11 using the backhaul 4 and the switch 1, and the master base station 2-1 and the slave base station 3-11 perform processing to generate a transmission frame, in parallel with the master base station 2-1 transmitting a notification of the transmission timing to the slave base station 3-11 by wireless communication using the channel Ch_JT. Therefore, compared to the frame processing shown in FIG. 11, the time required to transmit transmission data to the wireless device 4-1 can be shortened, and throughput can be further improved.

[0307] Furthermore, in the communication system 10 according to the first embodiment, a joint transmission execution notification E X-NOTF If you do not receive the notification, or if you do not receive the notification, X-NOTF Receive "Joint transmission occupancy time T OCCUPY When the state is not "inside," the master base station 2-1 and the slave base station 3-11 transmit a transmission frame to the wireless device 4-1 by joint transmission JT, so that when the master base station 2-1 transmits transmission data to the slave base station 3-11 via the backhaul 4 and the switch 1, there is no conflict with communication via the backhaul 4 between other cooperating base stations and the switch 1.

[0308] Therefore, the master base station 2-1 can transmit transmission data to the slave base station 3-11 via the backhaul 4 and the switch 1 without limiting the speed of data distribution to the slave base station 3-11.

[0309] That is, the master base station 2-1 can avoid contention with other cooperating base stations in the backhaul 4 and transmit the q1 pieces of transmission data to be transmitted to the wireless device 4-1 to the q1 slave base stations, respectively.

[0310] Fig. 12 is another schematic diagram showing frame processing in the communication system 10 shown in Fig. 1. Note that Fig. 12 shows frame processing in the case where the number of slave base stations is two.

[0311] Referring to FIG. 12, the master base station 2-1 transmits an RTS to the slave base stations 3-11 and 3-12 and the wireless device 4-1 by wireless communication using the channel Ch_JT.

[0312] Then, the slave base stations 3-11 and 3-12 and the wireless device 4-1 receive the RTS through wireless communication using the channel Ch_JT.

[0313] Thereafter, the wireless device 4-1 transmits a CTS to the master base station 2-1 by wireless communication using the channel Ch_JT.

[0314] Then, when the master base station 2-1 receives the CTS by wireless communication using the channel Ch_JT, it transmits a joint transmission JT start confirmation frame FS_PB to the slave base stations 3-11 and 3-12 by wireless communication using the channel Ch_JT.

[0315] The slave base stations 3-11 and 3-12 receive the start permission / prohibition confirmation frame FS_PB from the master base station 2-1 by wireless communication using the channel Ch_JT.

[0316] Each of the slave base stations 3-11, 3-12 then determines whether joint transmission JT with the master base station 2-1 is possible, and if it determines that joint transmission JT with the master base station 2-1 is possible, it generates a start possibility response frame FRSP including "JT_OK", and if it determines that joint transmission JT with the master base station 2-1 is not possible, it generates a start possibility response frame FRSP including "JT_NG".

[0317] Then, each of the slave base stations 3-11 and 3-12 transmits a start possibility response frame FRSP (=start possibility response frame FRSP including "JT_OK" or "JT_NG") in response to the start possibility confirmation frame FS_PB to the master base station 2-1 by wireless communication using channel Ch_JT.

[0318] The master base station 2-1 receives the start permission / prohibition response frames FRSP_1 and FRSP_2 from the slave base stations 3-11 and 3-12, respectively, via wireless communication using the channel Ch_JT.

[0319] Then, based on the start permission / prohibition response frames FRSP_1 and FRSP_2, the master base station 2-1 determines that (I) the joint transmission JT can be started, and sends a joint transmission execution notification E from the other cooperating base station groups. X-NOTF and the occupied time T OCCUPY (II) When it is determined that the joint transmission JT is not within the range, or (II) when the start of the joint transmission JT is possible and the execution notification E of the joint transmission is received from another cooperating base station group. X-NOTF When determining that the master base station 2-1 has not received the data, the master base station 2-1 determines the amount of data d 3-11 ,d 3-12 Calculate.

[0320] Thereafter, the master base station 2-1 calculates the padding time.

[0321] Then, the master base station 2-1 determines the occupied time T OCCUPY Execution notification E including X-NOTF to the master base station and the slave base station of the other cooperating base station group.

[0322] Then, the master base station 2-1 executes the following steps (1) to (3).

[0323] (1) The master base station 2-1 transmits a "transmission timing notification" and a padding PD consisting of a padding time to the slave base stations 3-11 and 3-12 by wireless communication using the channel Ch_JT, and (2) the master base station 2-1 transmits the transmission data d 1_trsm (Data volume d 3-11 transmission data having the same value), transmission data d 2_trsm (Data volume d 3-12(3) the master base station 2-1 and the slave base stations 3-11 and 3-12 perform a process of generating a transmission frame in parallel with the transmission of the padding PD in (1).

[0324] In this case, the above (2) is executed first, the above (1) is executed in parallel with (2), and after (2) is completed, the above (3) is executed in parallel with (1). As a result, the time required for the allocation of transmission data (2) in the master base station 2-1 partially overlaps with the time required for the transmission of the transmission timing notification (1), and the time required for the transmission frame generation process (3) in the master base station 2-1 and the slave base stations 3-11 and 3-12 partially overlaps with the time required for the transmission of the padding PD (1).

[0325] The process of allocating transmission data in the master base station 2-1 (2) and the process of generating transmission frames in the master base station 2-1 and the slave base stations 3-11 and 3-12 (3) are executed serially.

[0326] Then, the master base station 2-1, the slave base station 3-11, and the slave base station 3-12 each transmit a transmission frame F via wireless communication using the channel Ch_JT in the joint transmission JT. mst_trsm (=PPDU0),F 1_trsm (=PPDU1),F 2_trsm (=PPDU2) is simultaneously transmitted to the wireless device 4-1.

[0327] Then, the wireless device 4-1 receives a transmission frame F from the master base station 2-1 by wireless communication using the channel Ch_JT. mst_trsm (=PPDU0) and receives the transmission frame F from the slave base station 3-11. 1_trsm (=PPDU1) is received, and the slave base station 3-12 transmits the transmission frame F 2_trsm (=PPDU2) and transmits a Block Ack to the master base station 2-1 via wireless communication using channel Ch_JT.

[0328] Then, the master base station 2-1 receives a Block Ack from the wireless device 4-1 by wireless communication using the channel Ch_JT, and the wireless device 4-1 transmits a transmission frame F by joint transmission JT between the master base station 2-1 and the slave base stations 3-11 and 3-12. mst_trsm (=PPDU0),F 1_trsm (=PPDU1),F 2_trsm Detects that (=PPDU2) has been received.

[0329] Therefore, the master base station 2-1 transmits a "transmission timing notification" to the slave base stations 3-11 and 3-12, and the master base station 2-1 distributes transmission data to the slave base stations 3-11 and 3-12 via the backhaul 4 and the switch 1 in parallel with transmitting the "transmission timing notification" to the slave base stations 3-11 and 3-12. After that, the master base station 2-1 and the slave base stations 3-11 and 3-12 generate transmission frames in parallel with transmitting the "transmission timing notification" to the slave base stations 3-11 and 3-12. Then, the master base station 2-1 and the slave base stations 3-11 and 3-12 each generate a transmission frame F mst_trsm (=PPDU0),F 1_trsm (=PPDU1),F 2_trsm (=PPDU2) is transmitted to the wireless device 4-1.

[0330] Therefore, as shown in FIG. 12, in the communication system 10 according to the first embodiment, the master base station 2-1 allocates transmission data to the slave base stations 3-11 and 3-12 using the backhaul 4 and the switch 1, and therefore the amount of wireless resources used is less than when the transmission data is allocated to the slave base stations 3-11 and 3-12 by wireless communication, as shown in FIG. 9, and therefore the throughput can be improved compared to the case shown in FIG. 9.

[0331] Furthermore, as shown in FIG. 12, in the communication system 10 according to the first embodiment, the master base station 2-1 transmits a notification of the transmission timing to the slave base stations 3-11 and 3-12 by wireless communication using the channel Ch_JT, the master base station 2-1 allocates the transmission data to the slave base stations 3-11 and 3-12 using the backhaul 4 and the switch 1 in parallel with the transmission of the "notification of the transmission timing" and "padding PD" to the slave base stations 3-11 and 3-12, and the master base station 2-1 and the slave base stations 3-11 and 3-12 perform the process of generating a transmission frame in parallel with the transmission of the "notification of the transmission timing" to the slave base stations 3-11 and 3-12. Therefore, compared to the frame processing shown in FIG. 11, the time required to transmit the transmission data to the wireless device 4-1 can be shortened, and the throughput can be further improved.

[0332] In FIG. 10, the frame processing has been described for the case where there is one slave base station, and in FIG. 12, the frame processing has been described for the case where there are two slave base stations.

[0333] As a result, the changes in frame processing due to the addition of one slave base station are the number of initiation possibility confirmation frames FS_PB, the number of initiation possibility response frames FRSP, the calculation of the amount of data to be allocated to the slave base stations, the allocation of transmission data to the slave base stations, and the number of transmission frames PPDU.Therefore, if frame processing for the case where there is one slave base station and frame processing for the case where there are two slave base stations are explained, frame processing can generally be performed in the same way as the frame processing shown in Figure 12 even when there are q1 slave base stations capable of joint transmission JT.

[0334] 13 and 14 are first and second flowcharts, respectively, for explaining the operation of the communication system 10 shown in FIG.

[0335] 13, when the operation of the communication system 10 starts, the master base station 2-1 transmits an RTS to the slave base stations (=n1 slave base stations 3-11 to 3-1n1) and the wireless device 4-1 by wireless communication using the channel Ch_JT (step S1).

[0336] Then, the slave base stations (=n1 slave base stations 3-11 to 3-1n1) receive the RTS from the master base station 2-1 via wireless communication using channel Ch_JT (step S2), and the wireless device 4-1 receives the RTS from the master base station 2-1 via wireless communication using channel Ch_JT (step S3).

[0337] Thereafter, the wireless device 4-1 transmits a CTS to the master base station 2-1 by wireless communication using the channel Ch_JT (step S4).

[0338] The master base station 2-1 receives the CTS from the wireless device 4-1 through wireless communication using the channel Ch_JT (step S5).

[0339] Then, the master base station 2-1 transmits a start possibility confirmation frame FS_PB to the slave base stations (=n1 slave base stations 3-11 to 3-1n1) by wireless communication using the channel Ch_JT to confirm whether or not the joint transmission JT can be started (step S6).

[0340] The slave base stations (=n1 slave base stations 3-11 to 3-1n1) receive a start possibility confirmation frame FS_PB from the master base station 2-1 by wireless communication using channel Ch_JT (step S7), and transmit a joint transmission start possibility response frame FRSP indicating whether joint transmission JT is possible or not in response to the start possibility confirmation frame FS_PB to the master base station 2-1 (step S8).

[0341] Then, the master base station 2-1 receives the start permission / prohibition response frame FRSP from the slave base stations (=n1 slave base stations 3-11 to 3-1n1) by wireless communication using the channel Ch_JT (step S9).

[0342] Then, the master base station 2-1 determines whether or not it is possible to start the joint transmission JT based on the start possibility response frames FRSP (=n1 start possibility response frames FRSP) (step S10).

[0343] In this case, the master base station 2-1 determines that the joint transmission JT can be started if at least one of the start possibility response frames FRSP (=n1 start possibility response frames FRSP) contains "JT_OK", and determines that the joint transmission JT cannot be started if all of the start possibility response frames FRSP (=n1 start possibility response frames FRSP) contain "JT_NG".

[0344] In step S10, when it is determined that the joint transmission JT can be started, the master base station 2-1 transmits the joint transmission JT to the other cooperating base station groups (=cooperating base station groups AP_G2 to AP_G3) other than the cooperating base station group AP_G1. m Joint Transmission JT Execution Notification E, which is a notification to execute a joint transmission JT from X-NOTF It is determined whether or not the message has been received (step S11).

[0345] In step S11, the execution notification E of the joint transmission JT is X-NOTF When it is determined that the master base station 2-1 has received the signal, the master base station 2-1 transmits the signal to the other cooperating base station groups (=cooperating base station groups AP_G2 to AP_G m Occupancy time T in joint transmission JT by either OCCUPY It is determined whether or not the value is within the predetermined range (step S12).

[0346] Here, “occupation time T in joint transmission JT” OCCUPY " is the occupancy time of backhaul 4, T OCCUPY Then, the master base station 2-1 determines the occupied time TOCCUPY Whether it is within the range is determined by the following method.

[0347] The master base station 2-1 issues a joint transmission JT execution notification E X-NOTF The time t when receive_JT The occupancy time of backhaul 4 is T OCCUPY The time t when receive_JT +T OCCUPY is the current time t CRT If it is before, the occupied time T OCCUPY It is determined that it is not within the time t receive_JT +T OCCUPY is the current time t CRT If it is later than T OCCUPY It is determined that the value is within the range.

[0348] Then, in step S11, the execution notification E of the joint transmission JT is sent. X-NOTF When it is determined that the joint transmission JT has not been received, or when the joint transmission JT has been occupied for a certain period T OCCUPY If it is determined that the data amount is not within the range, the master base station 2-1 calculates the amount of data to be distributed to the n1 slave base stations 3-11 to 3-1n1 (or q1 slave base stations) (step S13).

[0349] Thereafter, the master base station 2-1 calculates the padding time T padding is calculated (step S14).

[0350] After step S14, the operation of the communication system 10 proceeds to step S15 in FIG.

[0351] In addition, when it is determined in step S10 that the joint transmission JT cannot be started, or when it is determined in step S12 that the other cooperating base station groups (=cooperating base station groups AP_G2 to AP_G m The joint transmission JT by either OCCUPY If it is determined that the time is within the predetermined range, the operation of the communication system 10 proceeds to step S21 in FIG.

[0352] 14, after step S14 in FIG. 13, the master base station 2-1 sets the occupation time T OCCUPY Joint transmission of JT execution notice E including X-NOTF " to other cooperating base station groups AP_G2 to AP_G m (step S15).

[0353] Then, (1) the master base station 2-1 transmits a "transmission timing notification" and "padding consisting of padding time" to the slave base stations (= q1 slave base stations that can start joint transmission JT) on channel Ch_JT, (2) the master base station 2-1 distributes the transmission data to the slave base stations (= q1 slave base stations) via the backhaul 4 and switch 1 in parallel with (1), and (3) the master base station 2-1 and the slave base stations (= q1 slave base stations) perform transmission frame generation processing in parallel with transmitting the padding PD of (1) (step S16).

[0354] Thereafter, the master base station 2-1 and the slave base stations (=q1 slave base stations) simultaneously transmit data frames to the wireless device 4-1 by wireless communication using the channel Ch_JT (step S17).

[0355] The wireless device 4-1 receives data frames from the master base station 2-1 and the slave base stations (=q1 slave base stations) by wireless communication using the channel Ch_JT (step S18).

[0356] Then, the wireless device 4-1 transmits a Block Ack to the master base station 2-1 by wireless communication using the channel Ch_JT (step S19).

[0357] The master base station 2-1 receives the Block Ack from the wireless device 4-1 through wireless communication using the channel Ch_JT (step S20).

[0358] On the other hand, when it is determined in step S10 of FIG. 12 that the joint transmission JT cannot be started, or when it is determined in step S12 that the other cooperating base station groups (=cooperating base station groups AP_G2 to AP_G m The joint transmission JT by either OCCUPY If it is determined that the master base station 2-1 is within the range, only the master base station 2-1 transmits a data frame to the wireless device 4-1 by wireless communication using the channel Ch_JT, or does not transmit a data frame to the wireless device 4-1 (step S21).

[0359] Thereafter, the wireless device 4-1 determines whether or not it has received a data frame from the master base station 2-1 through wireless communication using the channel Ch_JT (step S22).

[0360] In this case, if the master base station 2-1 transmits a data frame in step S21, the wireless device 4-1 determines in step S22 that it has received the data frame, and if the master base station 2-1 stops transmitting data in step S21, the wireless device 4-1 determines in step S22 that it has not received the data.

[0361] If it is determined in step S22 that the wireless device 4-1 has received the data, the above-described steps S19 and S20 are executed in sequence.

[0362] After step S20, or when it is determined in step S22 that the wireless device 4-1 has not received data, the operation of the communication system 10 ends.

[0363] In the flowcharts shown in FIGS. 13 and 14, "YES" in step S10 → "YES" in step S11 → S12 is executed when the joint transmission JT of the cooperating base station group AP_G1 is transmitted to the cooperating base station group AP_G2 to the cooperating base station group AP_G3, which is different from the cooperating base station group AP_G1. m This corresponds to determining whether or not there is a conflict with the joint transmission JT of at least one of the cooperating base station groups.

[0364] In step S10, determining that the joint transmission JT can be started (= "YES" in step S10) corresponds to determining that there are slave base stations (= q1 slave base stations) that execute the joint transmission JT in the cooperating base station group AP_G1, and in step S11, a joint transmission JT execution notification E X-NOTF The determination that the base station group AP_G1 has received the ACK signal ("YES" in step S11) indicates that the base station group AP_G2 to AP_G3 are different from the base station group AP_G1. m At least one of the cooperative base stations sends a joint transmission JT execution notification E X-NOTF In step S12, the occupancy time T OCCUPY It is determined that the time period during which the joint transmission JT is performed in the cooperating base station group AP_G1 is within the range of the cooperating base station groups AP_G2 to AP_G1. m This corresponds to overlapping (i.e., competing) with the time period in which the joint transmission JT is performed in at least one of the cooperating base station groups, and in step S12, the occupancy time T OCCUPY It is determined that the time period during which the joint transmission JT is executed in the cooperating base station group AP_G1 is not within the range of the time period during which the joint transmission JT is executed in the cooperating base station group AP_G2 to AP_G3. m This is because the time period does not overlap with (ie, does not conflict with) the time period in which the joint transmission JT is executed in at least one of the cooperating base station groups.

[0365] Therefore, when the master base station 2-1 of the cooperating base station group AP_G1 executes "YES" in step S10, "YES" in step S11, and "NO" in step S12, the master base station 2-1 of the cooperating base station group AP_G1 determines whether the joint transmission JT of the cooperating base station group AP_G1 is a joint transmission JT of the cooperating base station group AP_G2 to AP_G3, which are different from the joint transmission JT of the cooperating base station group AP_G1. m When it is determined that the joint transmission JT of the cooperating base station group AP_G1 does not conflict with the joint transmission JT of at least one of the cooperating base station groups AP_G2 to AP_G3, and the process is performed as follows: "YES" in step S10 → "YES" in step S11 → "YES" in step S12, the joint transmission JT of the cooperating base station group AP_G1 conflicts with the joint transmission JT of the cooperating base station group AP_G2 to AP_G3 different from the cooperating base station group AP_G1. mIt is determined that the signal conflicts with the joint transmission JT in at least one of the cooperating base station groups.

[0366] 13 and 14, executing "YES" in step S10 and then "NO" in step S11 means that the joint transmission JT of the cooperating base station group AP_G1 is transmitted to the cooperating base station groups AP_G2 to AP_G3, which are different from the cooperating base station group AP_G1. m This corresponds to determining that the signal does not conflict with the joint transmission JT in any of the cooperating base station groups.

[0367] The master base station 2-1 of the cooperating base station group AP_G1 is a base station of the cooperating base station groups AP_G2 to AP_G m The execution notification E of the joint transmission JT from any of the cooperative base station groups X-NOTF Since the joint transmission JT in the cooperating base station group AP_G1 is not received, the joint transmission JT in the cooperating base station groups AP_G2 to AP_G m This is because there is no conflict with the joint transmission JT in any of the cooperating base station groups.

[0368] From the above, "YES" in step S10 → steps S11 and S12 are performed to determine whether the joint transmission JT in the cooperating base station group AP_G1 is transmitted to the cooperating base station groups AP_G2 to AP_G m This corresponds to determining whether or not there is a conflict with the joint transmission JT in at least one of the cooperating base station groups.

[0369] 13 and 14, the joint transmission JT in the cooperating base station group AP_G1 is transmitted to the cooperating base station groups AP_G2 to AP_G m When it is determined that there is no conflict with the joint transmission JT in any of the cooperating base station groups (= "YES" in step S10 → "YES" in step S11 → "NO" in step S12, or "YES" in step S10 → "NO" in step S11), the master base station 2-1 of the cooperating base station group AP_G1 sequentially executes steps S13 to S20 to transmit the transmission data to the wireless device 4-1 through the joint transmission JT with the slave base stations (= q1 slave base stations), thereby completing the joint transmission JT.

[0370] Therefore, data transmission from the access point (=master base station 2-1 and q1 slave base stations) to the wireless device 4-1 can be performed while avoiding contention among a plurality of base station groups.

[0371] In the flowcharts shown in FIGS. 13 and 14, the following steps (1) to (3) are executed in step S16.

[0372] (1) The master base station 2-1 sends a “transmission timing notification” and a “padding time T padding The padding consisting of (2) In parallel with (1), the master base station 2-1 distributes the transmission data to the slave base stations (= q1 slave base stations) via the backhaul 4 and switch 1. (3) The master base station 2-1 and the slave base stations (=q1 slave base stations) perform the transmission frame generation process in parallel with the transmission of the padding PD in (1). Therefore, since the transmission data is distributed to the slave base stations (=q1 slave base stations) using the backhaul 4 and the switch 1, the amount of wireless resources used can be reduced compared to when the transmission data is distributed to the slave base stations (=q1 slave base stations) by wireless communication, and as a result, the throughput can be improved.

[0373] Furthermore, the master base station 2-1 distributes transmission data to the slave base stations (=q1 slave base stations) using the backhaul 4 and the switch 1, and the master base station 2-1 and the slave base stations (=q1 slave base stations) perform the process of generating transmission frames, in parallel with the master base station 2-1 transmitting notification of transmission timing to the slave base stations (=q1 slave base stations) by wireless communication using channel Ch_JT, so the time required to transmit transmission data to the wireless device 4-1 can be further reduced and throughput can be further improved.

[0374] In the above-described first embodiment, in step S16 of FIG. 14, (2) does not have to be executed in parallel with (1), and (3) does not have to be executed in parallel with (1).

[0375] Even if (2) and (3) are not executed in parallel with (1), if the master base station 2-1 executes the allocation of transmission data to the slave base stations (=q1 slave base stations) via the backhaul 4 and the switch 1, the amount of wireless resources used can be reduced compared to the case where the transmission data is allocated to the slave base stations (=q1 slave base stations) by wireless communication, and the transmission frame F from the master base station 2-1 and the q1 slave base stations to the wireless device 4-1 can be reduced. mst_trsm ,F 1_trsm ~F m_trsm This is because it can improve the throughput when transmitting.

[0376] Fig. 15 is a flowchart for explaining the detailed operation of step S14 in Fig. 13. However, in the explanation of the master base station 2-1, i=1.

[0377] Referring to FIG. 15, after step S13 in FIG. 13, the calculation unit 18 of the master base station 2-1 calculates q i Amount of data d i,1 ~d i,qi , link capacity s i , q i Transmission frame generation processing time t i,1 ~t i,qi , transmission time T and SIFS time T SIFS is received from the control unit 13 (step S141).

[0378] Then, the calculation unit 18 sets j=1 (step S142). Here, j is a function of q i Slave base stations 3-i1 to 3-iq i where j=1~q i is.

[0379] After step S142, the calculation unit 18 calculates the i-th cooperating base station group AP_G i The link capacity of the master base station s i and the i-th cooperative base station group AP_G i The number of slave base stations in i Substituting into equation (3), the i-th cooperating base station group AP_G i The transmission rate s on the backhaul 4 side between the master base station 2-i and the j-th slave base station 3-ij in i,j is calculated (step S143).

[0380] Then, the calculation unit 18 calculates j=q i It is determined whether or not this is the case (step S144).

[0381] In step S144, j=q i If it is determined that j is not j, the calculation unit 18 sets j=j+1 (step S145).

[0382] Thereafter, the operation of the arithmetic unit 18 proceeds to step S143, and in step S144, j=q i Steps S143 to S145 are repeatedly executed until it is determined that the above condition is met.

[0383] Then, in step S144, j=q i If it is determined that the q i Amount of data d i,1 ~d i,qi , q i Link capacity s i,1 ~s i,qi , the i-th cooperative base station group AP_G i q in i Slave base stations 3-i1 to 3-iq i The transmission frame generation processing time t i,1 ~t i,qi , transmission time T and SIFS time T SIFS Substituting into equation (2), q i padding time T padding(i)_1 ~T padding(i)_qiCalculate the calculated q i padding time T padding(i)_1 ~T padding(i)_qi The maximum value of the padding time T padding(i) (step S146).

[0384] After step S146, the operation of the communication system 10 proceeds to step S15 in FIG.

[0385] In the first embodiment, the operation of the master base station 2-1 may be performed by software.

[0386] In this case, the master base station 2-1 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory).

[0387] The ROM stores a program Prog_A having steps S1, S5, S6, S9 to S17, S20, and S21 shown in FIGS. 13 and 14 (including the flowchart shown in FIG. 15).

[0388] The CPU reads and executes the program Prog_A from the ROM, determines whether the joint transmission JT conflicts with the joint transmission JT of other cooperating base station groups, and when it determines that the joint transmission JT does not conflict with the joint transmission JT of other cooperating base station groups, allocates q1 pieces of transmission data to q1 slave base stations and transmits (q1+1) pieces of transmission data to the wireless device 4-1 through the joint transmission JT with the q1 slave base stations, and receives a block Ack from the wireless device 4-1.

[0389] In this case, the RAM temporarily stores (q1+1) pieces of transmission data, notification of transmission timing, padding, and the like.

[0390] [Embodiment 2] 16 is a schematic diagram of a communication system according to the second embodiment. Referring to FIG. 16, in the communication system 10A according to the second embodiment, the cooperating base station group AP_G1 of the communication system 10 shown in FIG. 1 is replaced with the cooperating base station group AP_G'1, and similarly, the cooperating base station group AP_G of the communication system 10 shown in FIG. m The cooperative base station group AP_G' m The rest is the same as the communication system 10.

[0391] The cooperating base station group AP_G'1 is the same as the cooperating base station group AP_G1 shown in Fig. 1 except that the master base station 2-1 of the cooperating base station group AP_G1 shown in Fig. 1 is replaced with a master base station 2-1A. m is the cooperative base station group AP_G shown in Figure 1. m The master base station 2-m has been changed to the master base station 2-mA. The rest are the cooperating base station group AP_G shown in Figure 1. m is the same as

[0392] The master base station 2-1A determines whether the joint transmission JT in the cooperating base station group AP_G'1 is a signal from the cooperating base station groups AP_G'2 to AP_G' m If there is a conflict with the joint transmission JT in at least one of the cooperating base station groups, the joint transmission JT is adjusted by the method described below.

[0393] Otherwise, the master base station 2-1A performs the same operations as the master base station 2-1 described above.

[0394] Fig. 17 is a schematic diagram of the master base station 2-1A shown in Fig. 16. Referring to Fig. 17, the master base station 2-1A is the same as the master base station 2-1, except that the control unit 13, wired unit 17, and arithmetic unit 18 of the master base station 2-1 shown in Fig. 2 are replaced with control unit 13A, wired unit 17A, and arithmetic unit 18A, respectively.

[0395] In the second embodiment, the execution notification E of the joint transmission JT X-NOTFis the switching capacity s occupied when the master base station distributes transmission data to the slave base stations in the i-th cooperating base station group via the backhaul 4 and the switch 1. i sw and joint transmission JT's occupancy time T OCCUPY Includes:

[0396] The control unit 13A receives the execution notification E of the joint transmission JT transmitted from the master base station of the cooperating base station group other than the cooperating base station group AP_G'1. X-NOTF is received from wired unit 17A.

[0397] Then, the control unit 13A determines that the joint transmission JT can be started based on the start permission response frame FRSP of the joint transmission JT, and sends an execution notification E of the joint transmission JT from the wired unit 17A. X-NOTF Upon receiving the notification, the execution of the joint transmission JT will be notified. X-NOTF is received, and the joint transmission JT's occupancy time T OCCUPY When it is determined that the switching capacitance is within the range of s1 sw’ ~s K sw’ (K is an integer greater than or equal to 1).

[0398] Then, after calculating the data distribution amount and the padding time, the control unit 13A calculates the index F by the following equations (5) to (9). i , the transmission time of the transmission frame T PPDU(i) , padding time T * padding(i) , and the data distribution communication speed s i sw Calculate the calculated index F i , the transmission time of the transmission frame T PPDU(i) , padding time T * padding(i) , and the data distribution communication speed s i sw to the control unit 13A.

[0399] Here, the data distribution communication speed si sw transmits data from the master base station 2-1A via the backhaul 4 and the switch 1. i Slave base stations 3-i1 to 3-iq i is the speed at which the power is allocated to the

[0400]

number

[0401] In equation (5), the first term on the right side is the i-th cooperating base station group AP_G i is the transmission time when only the master base station 2-i transmits the transmission data D_trsm to the wireless device 4-i, and the second term on the right side is the time when the i-th cooperating base station group AP_G i is the transmission time when a transmission frame is transmitted to the wireless device 4-i by joint transmission JT in i is the i-th cooperating base station group AP_G i is the amount of transmission data D_trsm when only the master base station 2-i transmits the transmission data D_trsm to the wireless device 4-i, and r i is the i-th cooperating base station group AP_G i Only the master base station 2-i of i is the transmission rate when transmitting the transmission data having i is the i-th cooperating base station group AP_G i Only the master base station 2-i of i , and the frame generation processing time when transmitting the transmission data having the above-mentioned value to the wireless device 4-i.

[0402] Also, in equation (5), T * padding(i) is the padding time, and T is the number of the i-th cooperating base station group AP_G i is the transmission time of the transmission timing notification frame when notifying the slave base station of the transmission timing in T SIFS is the time of the SIFS, and T PPDU(i) is the i-th cooperating base station group AP_Gi is the transmission time of the transmission frame.

[0403] And, T in Eq. (5) PPDU(i) is expressed by the following equation:

[0404]

number

[0405] In equation (6), D i is the i-th cooperating base station group AP_G i is the amount of data sent (=data length) in r i is the i-th cooperating base station group AP_G i is the wireless transmission rate of the master base station at d i,j is the i-th cooperating base station group AP_G i is the amount of data (=data length) allocated to the jth slave base station in r i,j is the i-th cooperating base station group AP_G i is the wireless transmission rate of the j-th slave base station in

[0406] The first term on the right side of equation (6) is the i-th cooperating base station group AP_G i represents the transmission time when the master base station transmits transmission data to the wireless device, and the second term on the right side of equation (6) represents the time when the master base station transmits transmission data to the wireless device. i represents the maximum transmission time of j transmission times when j slave base stations transmit j transmission data to a wireless device.

[0407] Therefore, equation (6) is expressed as follows: In the joint transmission JT, the i-th cooperating base station group AP_G i and the transmission time when the master base station in the i-th cooperating base station group AP_G i The maximum transmission time max(d i,j / ri,j ) and the maximum transmission time of the i-th cooperating base station group AP_G i The transmission time T of the transmission frame PPDU(i) This means that:

[0408] The i-th cooperative base station group AP_G i and the transmission time when the master base station in the i-th cooperating base station group AP_G i The maximum transmission time max(d i,j / r i,j ) is the same, the i-th cooperating base station group AP_G i and the transmission time when the master base station in the i-th cooperating base station group AP_G i The maximum transmission time max(d i,j / r i,j ) and any one of them is transmitted at the transmission time T PPDU(i) Let's say.

[0409] Also, the padding time T * padding(i) is expressed by the following equation:

[0410]

number

[0411] In equation (7), s * i,j is the i-th cooperating base station group AP_G i is the transmission rate of the data distribution communication through the backhaul 4 and the switch 1 between the master base station and the j-th slave base station at t i,j is the i-th cooperating base station group AP_G i is the transmission frame generation processing time in the j-th slave base station 3-ij.

[0412] In addition, in equation (7), the padding time T * padding(i) T * padding(i) <0, T * padding(i) =0.

[0413] In equation (7), the transmission rate s * i,j Using padding time T * padding(i) Therefore, the transmission speed s of backhaul 4 and switch 1 is calculated. * i,j When the padding time T * padding(i) The transmission speed of backhaul 4 and switch 1 is increased by s * i,j Even if the arrival of the transmitted data at the slave base station is delayed due to a decrease in * i,j Padding time T by the drop * padding(i) Since the padding time T * padding(i) If the data frame is transmitted when the time has elapsed, the master base station and the slave base station can transmit the data frame simultaneously.

[0414] And, s in Eq. (7) * i,j is expressed by the following equation:

[0415]

number

[0416] In equation (8), s i sw is the switching capacity that the i-th cooperating base station group occupies for data distribution. i sw is expressed by the following equation:

[0417]

number

[0418] In equation (9), s i is the link capacity of the master base station in the i-th cooperating base station group (= the transmission speed of the backhaul 4 from the master base station to the switch 1 when the master base station in the i-th cooperating base station group transmits transmission data to the slave base station in the i-th cooperating base station group via the backhaul 4 and the switch 1), and s sw max is the switching capacitance of switch 1, and s margin is the margin for the switch capacitance of switch 1, and s k sw’ is the execution notification E of the kth cooperative base station group X-NOTF This is the "occupied switching capacity" that has been notified in the

[0419] And margin s margin is set to estimate the switching capacity that background traffic will occupy.

[0420] In addition, in equation (9), the margin s margin The reason why is included is that in practice, in addition to data distribution traffic, switch 1 also has communication traffic, which consumes switching capacity, so a margin must be taken into account when calculating the speed of data distribution traffic.

[0421] In equation (9), s k sw’ is the "occupied switching capacity" notified by the kth cooperating base station group.

[0422] And in equation (9), s k sw’ Adding for k=1 to K is equivalent to calculating the switching capacity occupied by K cooperating base station groups.

[0423] In equation (9), the switching capacitance of switch 1 s sw max ] to [Margin s for the switching capacity of switch 1 margin ] and [switching capacity occupied by K cooperative base station groups] and [link capacity s of the master base station in the i-th cooperative base station group] i ] and the result is the remaining switching capacitance of switch 1.

[0424] Therefore, equation (9) is expressed as [the link capacity s i ] and [the remaining switching capacity of switch 1] is defined as the smaller capacity of “the switching capacity s i sw "

[0425] Then, by using equation (9), the switching capacity s i sw " is calculated in order to minimize the occupation of the switching capacity of the switch 1 in the allocation communication in which the master base station 2-iA allocates transmission data to q1 slave base stations in the i-th cooperating base station group, and to enable the allocation communication for allocating data to slave base stations in cooperating base station groups different from the i-th cooperating base station group to be performed without limiting the original switching capacity of the switch 1 (for example, 5.0 Gbps).

[0426] The control unit 13A determines the index F i , the transmission time of the transmission frame T PPDU(1) , padding time T * padding(1) , and the switching capacity s1 of the data distribution communication sw When the calculation unit 18A receives the value of s1 from the calculation unit 18B, the switching capacity s1 when distributing the transmission data to the q1 slave base stations is calculated. sw Determine whether or not is greater than "zero (=0)".

[0427] Then, the control unit 13A controls the switching capacitance s1 sw After determining that is greater than "zero (=0)", it is determined whether to execute joint transmission JT.

[0428] In this case, the control unit 13A calculates the index F AP_G’1 (=index F in the cooperating base station group AP_G'1) i ) is greater than "zero (=0)", it is determined that the joint transmission JT is to be executed, and the index F AP_G’1 If it is determined that is not greater than "zero (=0)", it is determined that joint transmission JT is not to be executed.

[0429] The first term on the right side of equation (5) represents the transmission time when only the master base station transmits transmission data to the wireless device, and the second term on the right side of equation (5) represents the transmission time when transmitting transmission data to the wireless device by joint transmission JT.

[0430] And the index F AP_G’1 is greater than "zero (=0)", this means that the first term on the right side of equation (5) is greater than the second term on the right side of equation (5), i.e., the second term on the right side of equation (5) is smaller than the first term on the right side of equation (5).

[0431] Also, the index F AP_G’1 is smaller than "zero (=0)", this means that the first term on the right side of equation (5) is smaller than the second term on the right side of equation (5).

[0432] Therefore, the index F shown in equation (5) AP_G’1 Determining the transmission method (joint transmission JT or transmission by only the master base station) using this is equivalent to selecting the transmission method that results in the shorter transmission time of "the transmission time when only the master base station transmits transmission data to the wireless device" and "the transmission time when transmission data is transmitted to the wireless device by joint transmission JT."

[0433] When the control unit 13A determines that the joint transmission JT is to be performed, the control unit 13A determines the “occupation time T OCCUPY " and "occupied switching capacity s1 sw " and the execution notice E of the joint transmission JT X-NOTF Create a joint transmission JT execution notification E X-NOTF to the wired unit 17A, and the execution notification E of the joint transmission JT X-NOTF to other cooperating base station groups, and transmits the “occupied switching capacity s1 sw "The speed of data allocation based on s * i,j and controls the wired unit 17A so as to adjust the speed of data distribution from the master base station 2-1A to the q1 slave base stations.

[0434] On the other hand, when the control unit 13A determines not to execute the joint transmission JT, it outputs "joint transmission JT not to be executed" to the wired unit 17A.

[0435] Furthermore, when control unit 13A receives from generation unit 15 q1 pieces of transmission data to be distributed to q1 slave base stations, control unit 13A outputs the received q1 pieces of transmission data to wired unit 17A.

[0436] Other than that, the control unit 13A performs the same functions as the control unit 13 in the first embodiment.

[0437] The wired unit 17A jointly transmits the JT execution notification E via the backhaul 4 and the switch 1. X-NOTF The cooperative base station group AP_G'2 to AP_G' m and receiving a notification of execution of the received joint transmission JT from at least one of the X-NOTF is output to the control unit 13A.

[0438] In addition, the wired unit 17A is configured to transmit a joint transmission JT execution notification E X-NOTF When the control unit 13A receives the execution notification E of the joint transmission JT via the backhaul 4 and the switch 1,X-NOTF The cooperative base station group AP_G'2 to AP_G' m Send to.

[0439] Furthermore, the wired unit 17A, under the control of the control unit 13A, determines the “occupied switching capacity s1 sw " is calculated by the data allocation transmission rate s * 1,j and adjusts the speed of data distribution from the master base station 2-1A to the q1 slave base stations. In this case, the wired unit 17A holds in advance the "number n1 (i.e., number q1) of slave base stations in the cooperating base station group AP_G'1" in equation (8).

[0440] Then, if the wired unit 17A can allocate the transmission data to q1 slave base stations at the desired transmission rate using the remaining switching capacity of the switch 1, it calculates the transmission rate of the backhaul 4 from the desired transmission rate and determines the transmission rate of the backhaul 4.

[0441] On the other hand, if the wired unit 17A cannot distribute the transmission data to the q1 slave base stations at the desired transmission speed using the remaining switching capacity of the switch 1, the wired unit 17A uses the available switching capacity of the switch 1 (=s1 sw ) and the transmission speed s * 1,j is calculated to determine the transmission speed of backhaul 4.

[0442] Furthermore, when the wired unit 17A receives q1 pieces of transmission data each having a data amount of q1 from the control unit 13A, the wired unit 17A transmits the received q1 pieces of transmission data via the backhaul 4 and the switch 1 at the adjusted transmission rate s * 1,j (or the transmission speed of backhaul 4 calculated from the desired transmission speed) to q1 slave base stations.

[0443] Other than that, the wired unit 17A performs the same functions as the wired unit 17 in the first embodiment.

[0444] The calculation unit 18A, under the control of the control unit 13A, calculates the index F1 shown in the formulas (5) to (9), the transmission time T PPDU(1) , padding time T * padding(1) , data distribution communication speed s * 1,j , and the switching capacitance s sw 1, and the calculated index F1 and the transmission time T PPDU(1) , padding time T * padding(1) , data distribution communication speed s * 1,j , and the switching capacitance s sw 1 to the control unit 13A.

[0445] The arithmetic unit 18A performs the same functions as the arithmetic unit 18 in the first embodiment.

[0446] In addition, the cooperating base station groups AP_G'2 to AP_G' m Each of the master base stations 2-2A to 2-mA has the same configuration as the master base station 2-1A shown in FIG.

[0447] As described in FIGS. 4 and 5, when a conflict occurs between the joint transmission JT by the cooperating base station group AP_G′1 and the joint transmission JT by the cooperating base station groups other than the cooperating base station group AP_G′1, in the second embodiment, the padding time T padding(1) When calculating the link capacity s1 of the master base station 2-1A in the cooperating base station group AP_G'1 and the remaining switching capacity of the switch 1 (= the second term on the right side of the formula (9)), the smaller capacity is used as the "switching capacity s1 occupied by the cooperating base station group AP_G'1 for data distribution." sw " and "the switching capacity s1 swIn equation (8), the division result (=s1 sw / q1) into "s * 1,j ” to find the padding time T * padding(1) The calculation of the padding time T * padding(1)_1 ~T * padding(1)_q1 Calculate the padding time T * padding(1)_1 ~T * padding(1)_q1 The maximum value of the padding time T * padding(1) Let's say.

[0448] Therefore, the timing at which the master base station 2-1A and the q1 slave base stations start the transmission frame generation process coincides, and the timing at which the master base station 2-1A and the q1 slave base stations transmit the transmission frames to the wireless device 4-1 also coincides.

[0449] Therefore, the master base station 2-1A and the q1 slave base stations successfully complete the joint transmission JT.

[0450] Fig. 18 is a schematic diagram showing frame processing in embodiment 2. Fig. 18 shows the master base station 2-1A and slave base station 3-11 in the cooperating base station group AP_G'1, and the master base station 2-2A, master base station 2-2A, slave base station 3-21, and wireless devices 4-1 and 4-2 in the cooperating base station group AP_G'2.

[0451] Referring to FIG. 18, the master base station 2-1A of the associated base station group AP_G'1 transmits an RTS to the slave base station 3-11 and the wireless device 4-1 by wireless communication using the channel Ch_JT.

[0452] The slave base station 3-11 and the wireless device 4-1 then receive the RTS from the master base station 2-1A via wireless communication using the channel Ch_JT.

[0453] Thereafter, the wireless device 4-1 transmits a CTS to the master base station 2-1A by wireless communication using the channel Ch_JT.

[0454] Then, when the master base station 2-1A receives a CTS from the wireless device 4-1 via wireless communication using channel Ch_JT, it generates a start possibility confirmation frame FS_PB for the joint transmission JT and transmits the start possibility confirmation frame FS_PB to the slave base station 3-11 via wireless communication using channel Ch_JT.

[0455] When the slave base station 3-11 receives the initiation possibility confirmation frame FS_PB from the master base station 2-1A by wireless communication using channel Ch_JT, it determines whether joint transmission JT with the master base station 2-1A is possible. If the slave base station 3-11 determines that joint transmission JT with the master base station 2-1A is possible, it generates an initiation possibility response frame FRSP including "JT_OK", and if it determines that joint transmission JT with the master base station 2-1A is not possible, it generates an initiation possibility response frame FRSP including "JT_NG".

[0456] The slave base station 3-11 then transmits a start permission / non-permission response frame FRSP (=start permission / non-permission response frame FRSP including "JT_OK" or "JT_NG") in response to the start permission / non-permission confirmation frame FS_PB to the master base station 2-1A by wireless communication using channel Ch_JT.

[0457] The master base station 2-1A receives the start permission / prohibition response frame FRSP from the slave base station 3-11 via wireless communication using the channel Ch_JT.

[0458] On the other hand, the master base station 2-2A of the associated base station group AP_G2 transmits an RTS to the slave base station 3-21 and the wireless device 4-2 by wireless communication using the channel Ch_JT.

[0459] The slave base station 3-21 and the wireless device 4-2 then receive the RTS from the master base station 2-2A via wireless communication using the channel Ch_JT.

[0460] Thereafter, the wireless device 4-2 transmits a CTS to the master base station 2-2A by wireless communication using the channel Ch_JT.

[0461] Then, when the master base station 2-2A receives a CTS from the wireless device 4-2 via wireless communication using channel Ch_JT, it generates a start possibility confirmation frame FS_PB for the joint transmission JT and transmits the start possibility confirmation frame FS_PB to the slave base station 3-21 via wireless communication using channel Ch_JT.

[0462] When the slave base station 3-21 receives the initiation possibility confirmation frame FS_PB from the master base station 2-2A by wireless communication using channel Ch_JT, it determines whether joint transmission JT with the master base station 2-2A is possible. If the slave base station 3-21 determines that joint transmission JT with the master base station 2-2A is possible, it generates an initiation possibility response frame FRSP including "JT_OK", and if it determines that joint transmission JT with the master base station 2-2A is not possible, it generates an initiation possibility response frame FRSP including "JT_NG".

[0463] Then, the slave base station 3-21 transmits a start permission / non-permission response frame FRSP (=start permission / non-permission response frame FRSP including "JT_OK" or "JT_NG") in response to the start permission / non-permission confirmation frame FS_PB to the master base station 2-2A by wireless communication using channel Ch_JT.

[0464] The master base station 2-2A receives the start permission / prohibition response frame FRSP from the slave base station 3-21 via wireless communication using the channel Ch_JT.

[0465] In the cooperating base station group AP_G'1, when the master base station 2-1A receives the start permission response frame FRSP, it determines whether or not it is possible to start the joint transmission JT with the slave base station 3-11 based on the start permission response frame FRSP. Then, when the master base station 2-1A determines that it is possible to start the joint transmission JT based on the start permission response frame FRSP (response frame FRSP including "JT_OK"), it receives a joint transmission JT execution notification E from the master base station of another cooperating base station group. X-NOTF It is determined whether or not the message has been received.

[0466] Then, the master base station 2-1A issues a notification E of execution of the joint transmission JT. X-NOTF When it is determined that the JT has been received, the execution notification E of the joint transmission JT is X-NOTF The joint transmission JT occupancy time T OCCUPY ” and the “occupation time T of the joint transmission JT by the cooperative base station group AP_G2” OCCUPY It is determined whether the value is "within" the range.

[0467] The master base station 2-1A issues a joint transmission JT execution notification E X-NOTF When it is determined that the JT has not been received, or when the JT has been OCCUPY When it is determined that the data amount d is not within the range of 100 Mbps, the data amount d to be distributed to the master base station 2-1A and the slave base station 3-11 is mst ,d 3-11 Calculate the padding time T padding(AP_G’1) Calculate.

[0468] Then, the master base station 2-1A sets the occupied time T OCCUPY and "occupied switching capacity s1 sw (=Switching capacity occupied by AP_G'1)" X-NOTF Create an execution notification E X-NOTFis transmitted to the master base station 2-2A and the slave base station 3-21 of the cooperating base station group AP_G'2 via the backhaul 4 and the switch 1.

[0469] In the cooperating base station group AP_G'2, the master base station 2-2A and the slave base station 3-21 receive the execution notification E transmitted from the cooperating base station group AP_G'1 via the backhaul 4 and the switch 1. X-NOTF Then, the master base station 2-2A determines whether or not the joint transmission JT can be executed by the above-described method, and if it determines that the joint transmission JT can be executed, it sends a joint transmission JT execution notification E to the cooperating base station group AP_G'1. X-NOTF Send.

[0470] Thereafter, in the associated base station group AP_G'1, the master base station 2-1A executes the following steps (1) to (3).

[0471] (1) The master base station 2-1A transmits a "transmission timing notification" and a "padding PD" to the slave base station 3-11 by wireless communication using the channel Ch_JT, and (2) the master base station 2-1A transmits the transmission data d via the backhaul 4 and the switch 1. 3-11_trsm (Data volume d 3-11 (3) the master base station 2-1A and the slave base station 3-11 perform a process of generating a transmission frame in parallel with (1).

[0472] In this case, the above (2) is executed first, the above (1) is executed in parallel with (2), and after (2) is completed, the above (3) is executed in parallel with (1). As a result, the time required for the master base station 2-1A to allocate transmission data (2) partially overlaps with the time required for the transmission of the transmission timing notification (1), and the time required for the master base station 2-1A and the slave base station 3-11 to perform the transmission frame generation process (3) partially overlaps with the time required for the transmission of the transmission timing notification (1).

[0473] The allocation of transmission data in the master base station 2-1A (2) and the generation of transmission frames in the master base station 2-1A and the slave base station 3-11 (3) are executed serially.

[0474] Here, (2) the master base station 2-1A transmits data d 1_trsm The allocation of (transmission data having a data amount d1) to the slave base station 3-11 is performed in parallel with (1). 1_trsm The time required to allocate (transmission data having a data amount d1) to the slave base station 3-11 and the time required to transmit the notification of the transmission timing in (1) overlap at least partially.

[0475] Furthermore, (3) the master base station 2-1A and the slave base station 3-11 perform the process of generating the transmission frame in parallel with (1), which means that the time required for the process of generating the transmission frame and the time required for sending the notification of the transmission timing in (1) overlap for at least a portion of the time length.

[0476] In the cooperating base station group AP_G′1, when the master base station 2-1A is executing the above (1) to (3), the master base station 2-1A receives a joint transmission execution notification E from the master base station 2-2A of the cooperating base station group AP_G2 via the backhaul 4 and the switch 1. X-NOTF Receive.

[0477] Then, the master base station 2-1A of the cooperating base station group AP_G′1 receives the padding time T * padding When the above process is completed, the master base station 2-1A and the slave base station 3-11 each transmit a transmission frame F mst_trsm (=PPDU10),F 1_trsm (=PPDU11) is simultaneously transmitted to the wireless device 4-1.

[0478] Here, the master base station 2-1A determines whether the joint transmission JT in the cooperating base station group AP_G'1 is occupied by the joint transmission JT in the cooperating base station group AP_G'2. OCCUPY The reason for determining that the value is not within the range is as follows.

[0479] The master base station 2-1A receives the execution notification E of the joint transmission JT from the master base station 2-2A of the cooperating base station group AP_G'2. X-NOTF The occupied time T included in OCCUPY , and the data distribution to the slave base station 3-11 is completed in the cooperating base station group AP_G'1 at the time t alc_end However, at the time t when the cooperating base station group AP_G′2 starts data distribution to the slave base station 3-21, alc_start This is because, since this is before the time when the transmission data allocation communication using the backhaul 4 by the cooperating base station group AP_G'1 and the transmission data allocation communication using the backhaul 4 by the cooperating base station group AP_G'2 do not conflict with each other.

[0480] In the cooperating base station group AP_G'1, the master base station 2-1A and the slave base station 3-11 transmit a transmission frame F mst_trsm (=PPDU10),F 1_trsm After transmitting the PPDU11 to the wireless device 4-1, the wireless device 4-1 receives a transmission frame F from the master base station 2-1A by wireless communication using the channel Ch_JT. mst_trsm (=PPDU10) and the slave base station 3-11 transmits the frame F 1_trsm Upon receiving the PPDU11, the master base station 2-1A transmits a Block Ack to the master base station 2-1A by wireless communication using the channel Ch_JT.

[0481] Then, the master base station 2-1A receives a Block Ack from the wireless device 4-1 by wireless communication using the channel Ch_JT, and receives a transmission frame F transmitted by the wireless device 4-1 through joint transmission JT between the master base station 2-1A and the slave base station 3-11. mst_trsm(=PPDU10),F 1_trsm Detects that (=PPDU11) has been received.

[0482] Therefore, the master base station 2-1A transmits a "transmission timing notification" to the slave base station 3-11 and transmits the transmission data d via the backhaul 4. 1_trsm The master base station 2-1A and the slave base station 3-11 perform the process of generating a transmission frame, and then allocate the padding time T * padding When the above is completed, the transmission frame F mst_trsm (=PPDU10),F 1_trsm (=PPDU11) is transmitted to the wireless device 4-1.

[0483] On the other hand, in the cooperating base station group AP_G'2, the master base station 2-2A issues a notification E of execution of the joint transmission JT. X-NOTF to the associating base station group AP_G'1, the master base station 2-2A and the slave base station 3-21 execute the above-mentioned (1) to (3) in the same manner as the master base station 2-1A and the slave base station 3-11 of the associating base station group AP_G'1, and then transmit the transmission frame F mst_trsm (=PPDU20),F 1_trsm (=PPDU21) is transmitted to the wireless device 4-2.

[0484] Then, the wireless device 4-2 transmits a transmission frame F via wireless communication using the channel Ch_JT. mst_trsm (=PPDU20),F 1_trsm (=PPDU21) and transmits a Block Ack to the master base station 2-2 via wireless communication using channel Ch_JT.

[0485] Then, the master base station 2-2A receives a Block Ack from the wireless device 4-2 by wireless communication using the channel Ch_JT, and receives a transmission frame F transmitted by the wireless device 4-2 through joint transmission JT between the master base station 2-2 and the slave base station 3-21. mst_trsm (=PPDU20),F 1_trsm Detects that (=PPDU21) has been received.

[0486] In FIG. 18, frame processing has been described for the case where there is one slave base station.

[0487] Furthermore, when the number of slave base stations in the cooperating base station group AP_G'1 and the cooperating base station group AP_G'2 is increased from one to two, the changes in frame processing are the number of start possibility confirmation frames FS_PB, the number of start possibility response frames FRSP, the calculation of the amount of data to be allocated to the slave base stations, the allocation of transmission data to the slave base stations, and the number of transmission frames PPDU.Therefore, if the frame processing for the case where there is one slave base station is described, the frame processing in the cooperating base station group AP_G'1 and the cooperating base station group AP_G'2 will be as follows.

[0488] The master base station 2-1A of the associated base station group AP_G'1 transmits the RTS to the slave base stations 3-11 and 3-12 and the wireless device 4-1 by wireless communication using the channel Ch_JT.

[0489] The slave base stations 3-11 and 3-12 and the wireless device 4-1 then receive the RTS from the master base station 2-1A via wireless communication using the channel Ch_JT.

[0490] Thereafter, the wireless device 4-1 transmits a CTS to the master base station 2-1A by wireless communication using the channel Ch_JT.

[0491] Then, when the master base station 2-1A receives a CTS from the wireless device 4-1 via wireless communication using channel Ch_JT, it generates a start possibility confirmation frame FS_PB for the joint transmission JT and transmits the start possibility confirmation frame FS_PB to the slave base stations 3-11 and 3-12 via wireless communication using channel Ch_JT.

[0492] When each of the slave base stations 3-11, 3-12 receives the initiation possibility confirmation frame FS_PB from the master base station 2-1A by wireless communication using channel Ch_JT, it determines whether joint transmission JT with the master base station 2-1A is possible. If each of the slave base stations 3-11, 3-12 determines that joint transmission JT with the master base station 2-1A is possible, it generates an initiation possibility response frame FRSP including "JT_OK", and if it determines that joint transmission JT with the master base station 2-1A is not possible, it generates an initiation possibility response frame FRSP including "JT_NG".

[0493] Then, each of the slave base stations 3-11 and 3-12 transmits a start possibility response frame FRSP (=start possibility response frame FRSP including "JT_OK" or "JT_NG") in response to the start possibility confirmation frame FS_PB to the master base station 2-1A by wireless communication using channel Ch_JT.

[0494] The master base station 2-1A receives the start permission / prohibition response frame FRSP from the slave base stations 3-11 and 3-12 by wireless communication using the channel Ch_JT.

[0495] On the other hand, the master base station 2-2A of the associated base station group AP_G'2 transmits an RTS to the slave base stations 3-21 and 3-22 and the wireless device 4-2 by wireless communication using the channel Ch_JT.

[0496] The slave base stations 3-21 and 3-22 and the wireless device 4-2 then receive the RTS from the master base station 2-2A via wireless communication using the channel Ch_JT.

[0497] Thereafter, the wireless device 4-2 transmits a CTS to the master base station 2-2A by wireless communication using the channel Ch_JT.

[0498] Then, when the master base station 2-2A receives a CTS from the wireless device 4-2 via wireless communication using channel Ch_JT, it generates a start possibility confirmation frame FS_PB for the joint transmission JT and transmits the start possibility confirmation frame FS_PB to the slave base stations 3-21 and 3-22 via wireless communication using channel Ch_JT.

[0499] When each of the slave base stations 3-21, 3-22 receives the initiation possibility confirmation frame FS_PB from the master base station 2-2A by wireless communication using channel Ch_JT, it determines whether joint transmission JT with the master base station 2-2A is possible. If each of the slave base stations 3-21, 3-22 determines that joint transmission JT with the master base station 2-2A is possible, it generates an initiation possibility response frame FRSP including "JT_OK", and if it determines that joint transmission JT with the master base station 2-2A is not possible, it generates an initiation possibility response frame FRSP including "JT_NG".

[0500] Then, each of the slave base stations 3-21 and 3-22 transmits a start possibility response frame FRSP (=start possibility response frame FRSP including "JT_OK" or "JT_NG") in response to the start possibility confirmation frame FS_PB to the master base station 2-2A by wireless communication using channel Ch_JT.

[0501] The master base station 2-2A receives the start permission / prohibition response frame FRSP from the slave base stations 3-21 and 3-22 by wireless communication using the channel Ch_JT.

[0502] In the cooperating base station group AP_G'1, when the master base station 2-1A receives the start permission response frame FRSP, if it determines that it is possible to start the joint transmission JT with the slave base stations 3-11 and 3-12 based on the start permission response frame FRSP (response frame FRSP including "JT_OK"), it receives a joint transmission JT execution notification E from the master base station of another cooperating base station group. X-NOTF It is determined whether or not the message has been received.

[0503] Then, the master base station 2-1A issues a notification E of execution of the joint transmission JT. X-NOTF When it is determined that the JT has been received, the execution notification E of the joint transmission JT is X-NOTF The joint transmission JT occupancy time T OCCUPY ” and the “occupation time T of the joint transmission JT” by the cooperative base station group AP_G′2 OCCUPY It is determined whether the value is "within" the range.

[0504] The master base station 2-1A issues a joint transmission JT execution notification E X-NOTF When it is determined that the JT has not been received, or when the JT has been OCCUPY If it is determined that the data amount d is not within the range of 100 Mbps, the data amount d to be distributed to the master base station 2-1A and the slave base stations 3-11 and 3-12 is mst ,d 3-11 ,d 3-12 Calculate the padding time T padding(AP_G’1) Calculate.

[0505] Then, the master base station 2-1A sets the occupied time T OCCUPY and "occupied switching capacity s1 sw (=Switching capacity occupied by AP_G'1)" X-NOTF Create an execution notification E X-NOTF is transmitted to the master base station 2-2A and the slave base stations 3-21 and 3-22 of the cooperating base station group AP_G'2 via the backhaul 4 and the switch 1.

[0506] In the cooperating base station group AP_G'2, the master base station 2-2A and the slave base stations 3-21 and 3-22 receive the execution notification E transmitted from the cooperating base station group AP_G'1 via the backhaul 4 and the switch 1. X-NOTF Then, the master base station 2-2A determines whether or not the joint transmission JT can be executed by the above-described method, and if it determines that the joint transmission JT can be executed, it sends an execution notification E to the cooperating base station group AP_G'1. X-NOTF Send.

[0507] Thereafter, in the associated base station group AP_G'1, the master base station 2-1A executes the following steps (1) to (3).

[0508] (1) The master base station 2-1A transmits a "transmission timing notification" and a "padding PD" to the slave base stations 3-11 and 3-12 by wireless communication using the channel Ch_JT, and (2) the master base station 2-1A transmits the transmission data d via the backhaul 4 and the switch 1. 3-11_trsm (Data volume d 3-11 (3) the master base station 2-1A and the slave base stations 3-11 and 3-12 perform processing to generate a transmission frame in parallel with (1).

[0509] In this case, the above (2) is executed first, the above (1) is executed in parallel with (2), and after (2) is completed, the above (3) is executed in parallel with (1). As a result, the time required for the allocation of transmission data (2) in the master base station 2-1A partially overlaps with the time required for the transmission of the transmission timing notification (1), and the time required for the transmission frame generation process (3) in the master base station 2-1A and the slave base stations 3-11 and 3-12 partially overlaps with the time required for the transmission of the transmission timing notification (1).

[0510] The allocation of transmission data in the master base station 2-1A (2) and the generation of transmission frames in the master base station 2-1A and the slave base stations 3-11 and 3-12 (3) are executed serially.

[0511] Here, (2) the master base station 2-1A transmits data d 1_trsm The allocation of (transmission data having a data amount d1) to the slave base stations 3-11 and 3-12 is performed in parallel with (1). 1_trsm (transmission data having a data amount d1), d 2_trsm The time required to allocate (transmission data having a data amount d2) to the slave base stations 3-11 and 3-12 and the time required to transmit the notification of the transmission timing in (1) overlap at least partially.

[0512] Furthermore, (3) the master base station 2-1A and the slave base stations 3-11 and 3-12 perform the process of generating the transmission frame in parallel with (1), which means that the time required for the process of generating the transmission frame and the time required for sending the notification of the transmission timing in (1) overlap for at least a portion of the time length.

[0513] In the cooperating base station group AP_G'1, when the master base station 2-1A is executing the above (1) to (3), the master base station 2-1A receives a joint transmission execution notification E from the master base station 2-2A of the cooperating base station group AP_G'2 via the backhaul 4 and the switch 1. X-NOTF Receive.

[0514] Then, the master base station 2-1A of the cooperating base station group AP_G′1 receives the padding time T * padding When the above process is completed, the master base station 2-1A and the slave base stations 3-11 and 3-12 each transmit a transmission frame F mst_trsm (=PPDU10),F 1_trsm (=PPDU11),F 2_trsm(=PPDU12) to the wireless device 4-1 at the same time.

[0515] Here, the master base station 2-1A determines whether the joint transmission JT in the cooperating base station group AP_G'1 is occupied by the joint transmission JT in the cooperating base station group AP_G'2. OCCUPY The reason for determining that the value is not within the range is as follows.

[0516] The master base station 2-1A receives the execution notification E of the joint transmission JT from the master base station 2-2A of the cooperating base station group AP_G'2. X-NOTF The occupied time T included in OCCUPY , and the data distribution to the slave base stations 3-11 and 3-12 is completed in the cooperating base station group AP_G'1. alc_end However, at the time t when the cooperating base station group AP_G′2 starts distributing data to the slave base stations 3-21 and 3-22, alc_start This is because, since this is before the time when the transmission data allocation communication using the backhaul 4 by the cooperating base station group AP_G'1 and the transmission data allocation communication using the backhaul 4 by the cooperating base station group AP_G'2 do not conflict with each other.

[0517] In the cooperating base station group AP_G'1, the master base station 2-1A and the slave base stations 3-11 and 3-12 transmit a transmission frame F mst_trsm (=PPDU10),F 1_trsm (=PPDU11),F 2_trsm After transmitting the PPDU12 to the wireless device 4-1, the wireless device 4-1 receives a transmission frame F from the master base station 2-1A by wireless communication using the channel Ch_JT. mst_trsm (=PPDU10) and the slave base station 3-11 transmits the frame F 1_trsm (=PPDU11) is received, and the slave base station 3-12 transmits the transmission frame F 2_trsm Upon receiving the block Ack (=PPDU12), the master base station 2-1A transmits a block Ack to the master base station 2-1A by wireless communication using the channel Ch_JT.

[0518] Then, the master base station 2-1A receives a Block Ack from the wireless device 4-1 by wireless communication using the channel Ch_JT, and receives a transmission frame F transmitted by the wireless device 4-1 through joint transmission JT between the master base station 2-1A and the slave base stations 3-11 and 3-12. mst_trsm (=PPDU10),F 1_trsm (=PPDU11),F 2_trsm Detects that (=PPDU12) has been received.

[0519] Therefore, the master base station 2-1A transmits the "transmission timing notification" to the slave base stations 3-11 and 3-12 and transmits the transmission data d via the backhaul 4. 1_trsm ,d 2_trsm to the slave base stations 3-11 and 3-12, and the master base station 2-1A and the slave base stations 3-11 and 3-12 perform the process of generating the transmission frame, and then, after that, the padding time T * padding When the above is completed, the transmission frame F mst_trsm (=PPDU10),F 1_trsm (=PPDU11),F 2_trsm (=PPDU12) is transmitted to the wireless device 4-1.

[0520] On the other hand, in the cooperating base station group AP_G'2, the master base station 2-2A issues a notification E of execution of the joint transmission JT. X-NOTF to the associating base station group AP_G'1, the master base station 2-2A and the slave base stations 3-21 and 3-22 execute the above-mentioned (1) to (3) in the same manner as the master base station 2-1A and the slave base stations 3-11 and 3-12 of the associating base station group AP_G'1, and then each transmits a transmission frame F mst_trsm (=PPDU20),F 1_trsm (=PPDU21),F 2_trsm (=PPDU22) is sent to the wireless device 4-2.

[0521] Then, the wireless device 4-2 transmits a transmission frame F via wireless communication using the channel Ch_JT. mst_trsm (=PPDU20),F 1_trsm (=PPDU21),F 2_trsm (=PPDU22) and transmits a Block Ack to the master base station 2-2 by wireless communication using channel Ch_JT.

[0522] Then, the master base station 2-2A receives a Block Ack from the wireless device 4-2 by wireless communication using the channel Ch_JT, and receives a transmission frame F transmitted by the wireless device 4-2 through joint transmission JT between the master base station 2-2 and the slave base stations 3-21 and 3-22. mst_trsm (=PPDU20),F 1_trsm (=PPDU21),F 2_trsm Detects that (=PPDU22) has been received.

[0523] The changes in frame processing due to the addition of one slave base station are the number of initiation possibility confirmation frames FS_PB, the number of initiation possibility response frames FRSP, the calculation of the amount of data to be allocated to the slave base stations, the allocation of transmission data to the slave base stations, and the number of transmission frames PPDU.Therefore, as described above, if the frame processing for the case where there is one slave base station and the frame processing for the case where there are two slave base stations, frame processing can generally be performed in the same manner as described above even when there are q1 slave base stations capable of joint transmission JT.

[0524] 19 and 20 are first and second flowcharts, respectively, for explaining the operation of the communication system 10A shown in FIG.

[0525] The flowcharts shown in Figures 19 and 20 are the same as the flowcharts shown in Figures 13 and 14, except that step S14 in the flowcharts shown in Figures 13 and 14 is replaced with step S14A and steps S23 to S26 are added to the flowcharts shown in Figures 13 and 14.

[0526] Referring to FIG. 19, when the operation of the communication system 10A is started, the above-described steps S1 to S12 are sequentially executed.

[0527] Then, in step S12, the occupied time T OCCUPY If it is determined that the occupied switching capacities are within the range of 100 Mbps, the control unit 13A of the master base station 2-1A acquires all the occupied switching capacities notified from the other cooperating base station groups (step S23) and stores all the acquired occupied switching capacities. Then, in step S11, the control unit 13A of the master base station 2-1A acquires all the occupied switching capacities notified from the other cooperating base station groups and stores the acquired occupied switching capacities. X-NOTF When it is determined that the joint transmission JT has not been received, or when the joint transmission JT has been received for the occupancy time T OCCUPY If it is determined that the time is not within the predetermined range, or after step S23, the above-described step S13 is executed.

[0528] After step S13, the operation of the communication system 10A proceeds to step S24 in FIG. 20, or when it is determined in step S10 that the joint transmission JT cannot be started, the operation of the communication system 10A proceeds to step S21 in FIG. 20.

[0529] 20, after step S13 in FIG. 19, the control unit 13A of the master base station 2-1A calculates the switching capacity s sw is calculated (step S24).

[0530] Then, the control unit 13A calculates the switching capacity s sw It is determined whether or not is greater than "zero (=0)" (step S25).

[0531] In step S25, the switching capacitance s sw If it is determined that is not greater than "zero (=0)", the operation of the communication system 10A proceeds to step S21.

[0532] On the other hand, in step S25, the switching capacitance s sw is determined to be greater than "zero (=0)", the calculation unit 18A of the master base station 2-1A calculates the padding time T * padding(1) (Step 14A). Then, the calculation unit 18A calculates the padding time T * padding(1) is output to the control unit 13A.

[0533] After step S14A, the control unit 13A of the master base station 2-1A determines whether or not to execute joint transmission JT (step S26).

[0534] In this case, the control unit 13A of the master base station 2-1A determines to execute the joint transmission JT when the index F1 of equation (5) is greater than "zero (=0)", and determines not to execute the joint transmission JT when the index F1 of equation (5) is not greater than "zero (=0)".

[0535] Then, in step S26, when it is determined that joint transmission JT is to be executed, the above-mentioned steps S15 to S20 are executed in order.

[0536] On the other hand, when it is determined in step S10 of FIG. 19 that the joint transmission JT cannot be started, or when it is determined in step S25 that the switching capacity s occupied by the cooperating base station group AP_G'1 is sw If it is determined that is not greater than "zero (=0)", or if it is determined in step S26 that joint transmission JT is not to be executed, the above-mentioned steps S21 and S22 are executed in sequence.

[0537] Then, when it is determined in step S22 that a data frame has been received, the above-described steps S19 and S20 are executed in sequence, and the operation of the communication system 10A ends.

[0538] On the other hand, if it is determined in step S22 that a data frame has not been received, the operation of the communication system 10A ends.

[0539] In the flowcharts shown in FIGS. 19 and 20, in step S25, the switching capacitance s sw is determined to be greater than "zero (=0)", in step S14A, the padding time T * padding(1) is calculated.

[0540] This is the switching capacitance s sw is not greater than "zero (=0)" (i.e., switching capacitance s sw When is less than or equal to "zero (=0)" (s sw ≦0)), in equation (8), the communication speed s * 1,j As a result, the padding time T * padding(1) This is because it is not possible to calculate

[0541] 19 and 20, in step S25, the switching capacity s sw is greater than "zero (=0)", it corresponds to determining that there is available switching capacity of the switch 1, and the switching capacity s sw Determining that is not greater than "zero (=0)" corresponds to determining that there is no available switching capacity of switch 1.

[0542] Furthermore, in the flowcharts shown in Figures 19 and 20, in step S26, when the index F1 of equation (5) is greater than "zero (=0)", it is determined that joint transmission JT is to be executed. This is because the "transmission time when transmission data is transmitted to the wireless device 4-1 by joint transmission JT" represented by the second term on the right side of equation (5) is shorter than the "transmission time when only the master base station 2-1A transmits transmission data to the wireless device 4-1" represented by the first term on the right side of equation (5), and therefore the transmission data is transmitted to the wireless device 4-1 in a shorter transmission time.

[0543] Then, in step S26, when the index F1 of equation (5) is not greater than "zero (=0)", it is determined that the joint transmission JT will not be executed because the "transmission time when only the master base station 2-1A transmits transmission data to the wireless device 4-1" represented by the first term on the right side of equation (5) is shorter than the "transmission time when transmission data is transmitted to the wireless device 4-1 by the joint transmission JT" represented by the second term on the right side of equation (5).

[0544] Therefore, step S26 corresponds to determining whether or not to execute joint transmission JT based on the transmission time when transmitting the transmission data to the wireless device 4-1.

[0545] Furthermore, in the flowcharts shown in FIGS. 19 and 20, in step S11 of FIG. 19, the execution notification E of the joint transmission JT is sent from the cooperating base station group other than the cooperating base station group AP_G′1. X-NOTF 19. When it is determined that the joint transmission JT is not received, or when it is determined in step S12 of FIG. 19 that the occupation time T OCCUPY If it is determined that the timing is not within the range, it means that the joint transmission JT is not being executed by the cooperating base station groups other than the cooperating base station group AP_G'1 at the timing when the cooperating base station group AP_G'1 executes the joint transmission JT.

[0546] As a result, in step S25 of FIG. 20, the switching capacity ssw is determined to be greater than "zero (=0)", and in step S26, the transmission method that can achieve the shorter transmission time (joint transmission JT or transmission by only the master base station 2-1A) is selected.

[0547] On the other hand, if the process proceeds to step S24 of FIG. 19 after step S13 of FIG. 19, when the joint transmission JT is being performed by the cooperating base station groups other than the cooperating base station group AP_G′1, the switching capacity s occupied by the cooperating base station group AP_G′1 is calculated in step S25. sw is greater than "zero (=0)", so in step S25, the switching capacity s sw When it is determined that the switching capacitance s is greater than "zero (=0)" sw is the switching capacity s occupied by the cooperating base station group AP_G'1 in step S25 after "NO" in step S11 or "NO" in step S12 of FIG. sw When it is determined that the switching capacitance s is greater than "zero (=0)" sw It will be less than.

[0548] As a result, in the cooperating base station group AP_G'1, the communication speed for distributing transmission data from the master base station 2-1A to the q1 slave base stations via the backhaul 4 and switch 1 becomes slower, so the transmission time of the joint transmission JT becomes longer than the transmission time by the master base station 2-1A alone, and in step S26, it is determined that the joint transmission JT will not be executed.

[0549] Therefore, in step S25, the switching capacitance s sw Determining that is greater than "zero (=0)" is a prerequisite for determining whether or not to execute joint transmission JT in step S26.

[0550] The rest of the description of the flowcharts shown in FIGS. 19 and 20 is the same as the description of the flowcharts shown in FIGS.

[0551] FIG. 21 is a flowchart for explaining the detailed operation of step S14A in FIG.

[0552] The flowchart shown in Fig. 21 is the same as the flowchart shown in Fig. 15, except that steps S143 and S146 in the flowchart shown in Fig. 15 are replaced with steps S143A and S146A, respectively. However, since this is an explanation of the master base station 2-1A, i=1.

[0553] Referring to FIG. 21, in step S25 of FIG. 20, the switching capacitance s sw If it is determined that is greater than "zero (=0)", the above-mentioned steps S141 and S142 are executed in sequence.

[0554] After step S142, the calculation unit 18A calculates the i-th cooperating base station group AP_G i The transmission rate s of the data distribution communication on the backhaul 4 side between the master base station 2-iA and the j-th slave base station 3-1j in the cooperating base station group AP_G′1 * i,j is calculated (step S143A).

[0555] Then, the above-mentioned step S144 is executed. In step S144, j=q i If it is determined that this is not the case, step S145 described above is executed.

[0556] Then, in step S144, j=q i Steps S143A, S144, and S145 are repeatedly executed until it is determined that the above condition is met.

[0557] In step S144, j=q i If it is determined that the q i Amount of data d i,1 ~d i,qi , q i Link capacity s* i,1 ~s * i,qi , the i-th cooperative base station group AP_G i q in i Slave base stations 3-i1 to 3-iq i The transmission frame generation processing time t i,1 ~t i,qi , transmission time T and SIFS time T SIFS Substituting into equation (7), q i padding time T * padding(i)_1 ~T * padding(i)_qi Calculate the calculated q i padding time T * padding(i)_1 ~T * padding(i)_qi The maximum value of the padding time T * padding(i) (Step S146A).

[0558] After step S146A, the operation of the communication system 10A proceeds to step S26 in FIG.

[0559] In the flowchart shown in FIG. 21, in step S25 of FIG. 20, the cooperating base station group AP_G i (=AP_G'1) occupies switching capacity s for data distribution. sw is determined to be greater than "zero (=0)", in step S143A, the calculation unit 18A calculates the transmission rate s * i,j can be calculated.

[0560] As a result, the calculation unit 18A calculates the padding time T * padding(i) can be calculated.

[0561] In the second embodiment, the operation of the master base station 2-1A may be performed by software.

[0562] In this case, the master base station 2-1A includes a CPU, a ROM, and a RAM.

[0563] The ROM stores a program Prog_B including steps S1, S5, S6, S9 to S12, S23, S13, S24, S25, S14A, S26, S15 to S17, S20, and S21 shown in Figures 19 and 20 (including the flowchart shown in Figure 21).

[0564] The CPU reads and executes the program Prog_B from the ROM, determines whether the joint transmission JT conflicts with the joint transmission JT of other cooperating base station groups, and when it determines that the joint transmission JT does not conflict with the joint transmission JT of other cooperating base station groups, or when it determines that the joint transmission JT is executable even if it conflicts with the joint transmission JT of other cooperating base station groups, it allocates q1 pieces of transmission data to q1 slave base stations and transmits (q1+1) pieces of transmission data to the wireless device 4-1 by the joint transmission JT with the q1 slave base stations, and receives a block Ack from the wireless device 4-1.

[0565] In this case, the RAM stores (q1+1) pieces of transmission data, notification of transmission timing, and switching capacity s sw and padding T * padding(1) ~T * padding(q1) etc. are temporarily stored.

[0566] (Example) Assume that the cooperating base station group AP_G'1 transmits data to the wireless device 4-1 using one slave base station 3-11, and the cooperating base station group AP_G2 transmits data to the wireless device 4-2 using one slave base station 3-21, and the cooperating base station group AP_G2 attempts to execute the joint transmission JT while the cooperating base station group AP_G'1 has already executed the joint transmission JT.

[0567] The parameters are shown in Table 2.

[0568] [Table 2]

[0569] Focusing on the cooperating base station group AP_G'1, the amount of transmission data allocated to the slave base station 3-11, d 11 When calculated, it becomes the following formula:

[0570]

number

[0571] On the other hand, the transmission data d1 of the master base station 2-1A of the associated base station group AP_G'1 is expressed by the following equation.

[0572]

number

[0573] From equation (9), the switching capacity s1 sw is expressed as follows:

[0574]

number

[0575] Therefore, from equation (8), the following equation is obtained.

[0576]

number

[0577] Furthermore, from equation (7), the padding time is expressed as follows:

[0578]

number

[0579] The transmission time of the data frame T PPDU(1) When calculated, it becomes the following formula:

[0580]

number

[0581] When the index F1 is calculated using the formula (5), it is expressed as follows:

[0582]

number

[0583] Therefore, the master base station 2-1A of the associated base station group AP_G'1 determines to execute the joint transmission JT.

[0584] Next, focusing on the cooperating base station group AP_G'2, the amount of transmission data to be allocated to the slave base station 3-21 is calculated using equation (1), as follows:

[0585]

number

[0586] On the other hand, the amount of transmission data d2 of the master base station 2-2 is expressed by the following equation.

[0587]

number

[0588] Then, from equation (9), the switching capacitance s sw 1 is expressed as follows:

[0589]

number

[0590] Therefore, from equation (8), the transmission rate s' of data distribution to the slave base station 3-21 is 21 is expressed as follows:

[0591]

number

[0592] From equation (7), the padding time T * padding(2) is expressed as follows:

[0593]

number

[0594] Then, from equation (6), the transmission time of the data frame T PPDU(2) When calculated, it becomes the following formula:

[0595]

number

[0596] Furthermore, from equation (5), the index F2 is expressed as follows:

[0597]

number

[0598] Therefore, the master base station 2-2A determines not to execute the joint transmission JT.

[0599] Other aspects of the second embodiment are the same as those of the first embodiment.

[0600] In the above-described first and second embodiments, it has been explained that there is one channel for wireless communication, but the present invention is not limited to this, and there may be a plurality of channels for wireless communication.

[0601] In addition, when a plurality of channels are used, for example, m cooperating base station groups AP_G1 to AP_G m Each of the channels uses a different channel Ch1 to Chm.

[0602] The communication system 10 according to the above-described first embodiment and the communication system 10A according to the second embodiment are common in that they execute steps S1 to S22 of the flowcharts shown in FIGS. 13 and 14 (including the flowchart shown in FIG. 15).

[0603] As described above, the execution of "YES" in step S10 of the flowchart shown in FIG. 11 and FIG. 12, followed by "YES" in step S11, followed by S12, means that the joint transmission JT of the cooperating base station group AP_G1 is transmitted to the cooperating base station group AP_G2 to the cooperating base station group AP_G3, which is different from the cooperating base station group AP_G1. m This corresponds to determining whether or not there is a conflict with the joint transmission JT of at least one of the cooperating base station groups.

[0604] Therefore, according to an embodiment of the present invention, the communication method is: A communication system including: a first cooperating base station group having a star configuration in which a master base station and a slave base station are directly connected to a switch via a backhaul, the first cooperating base station group including a first master base station and n1 (n1 is an integer equal to or greater than 1) first slave base stations; and a second cooperating base station group having a star configuration and including a second master base station, the second master base station and n2 (n2 is an integer equal to or greater than 1) second slave base stations, the system comprising ... transmitting transmission data D_trsm to a wireless device using joint transmission in which the master base station and the slave base stations jointly transmit data to the wireless device by wireless communication of a CSMA / CA system using a communication channel consisting of one or a plurality of channels; a first step of determining whether joint transmission by a first cooperating base station group is possible when a first master base station receives transmission data D_trsm from a transmission source; a second step of calculating, when it is determined in the first step that joint transmission is possible, q1 data amounts of q1 pieces of transmission data to be allocated to q1 (q1 is an integer satisfying 1≦q1≦n1) first slave base stations that are capable of joint transmission among the n1 first slave base stations; a third step in which the first master base station calculates padding having a length consisting of a padding time; a fourth step in which the first master base station transmits a notification of execution of joint transmission to the second cooperating base station group; a fifth step in which the first master base station, after the fourth step, transmits a transmission timing notification, which notifies the wireless device of the timing to transmit the transmission frame, and padding, to the q first slave base stations via the wireless communication; a sixth step in which, after the second step, the first master base station transmits q1 pieces of transmission data, each having q1 data amounts, to the q1 first slave base stations via the backhaul via the switch; a seventh step in which the first master base station and each of the q1 first slave base stations perform a transmission frame generation process, which is a process of generating a transmission frame based on the transmission data, after the second step; an eighth step of, when a transmission timing arrives, transmitting (q1+1) transmission frames to the wireless device by wireless communication through joint transmission by the first master base station and the q1 first slave base stations; The method may further comprise a ninth step of the first master base station receiving, after the eighth step, a block Ack from the wireless device, which sends a block Ack to confirm reception of the frames.

[0605] This is because if the communication method includes the first to ninth steps, it is possible to transmit data from an access point to a wireless device while avoiding contention among multiple cooperating base station groups.

[0606] Furthermore, according to an embodiment of the present invention, the communication system includes: a first cooperating base station group having a star configuration in which a master base station and a slave base station are directly connected to a switch via a backhaul, the first cooperating base station group including a first master base station and n1 (n1 is an integer equal to or greater than 1) first slave base stations; a second cooperating base station group having a star configuration, the second cooperating base station group including a second master base station and n2 (n2 is an integer equal to or greater than 1) second slave base stations; a switch that receives data transmitted from either the first or second master base station via a backhaul and transmits the received data via the backhaul to a slave base station in the same cooperating base station group as the data transmission source; a first cooperating base station group; and a wireless device that receives (q1+1) transmission frames through joint transmission by q1 (q1 is an integer satisfying 1≦q1≦n1) slave base stations among n1 first slave base stations, in which the master base station and the slave base station jointly transmit data to the wireless device by wireless communication of a CSMA / CA system using a communication channel consisting of one or a plurality of channels, or that receives a transmission frame including transmission data D_trsm transmitted only by the first master base station; The first master base station of the first cooperating base station group performs a first receiving process when receiving a notification of execution of joint transmission from a second master base station of a second cooperating base station group; a first calculation process for calculating q1 data amounts of the q1 transmission data to be assigned to each of the q1 first slave base stations when determining that joint transmission is possible; a second calculation process for calculating padding having a length consisting of a padding time; a first transmitting process for transmitting a notification of execution of joint transmission to the second cooperating base station group after the first and second calculation processes; and a transmission timing notification and padding notification for notifying a timing of transmitting a transmission frame to a wireless device after the first and second calculation processes. a second transmission process for transmitting the q1 transmission data, each having q1 data amounts allocated to the q1 first slave base stations, to the q1 first slave base stations by wireless communication; a transmission frame generation process for generating a transmission frame based on its own transmission data after the first and second calculation processes; and a second reception process for transmitting (q1+1) transmission frames to the wireless device by joint transmission with the q1 first slave base stations and then receiving a block Ack from the wireless device that collectively sends an Ack to acknowledge reception of the frames; the q1 first slave base stations perform a second reception process of receiving a notification of a transmission timing from the first master base station and a third reception process of receiving the q1 pieces of transmission data from the first master base station via the switch and the backhaul, and perform a transmission frame generation process of generating q1 transmission frames based on the q1 pieces of transmission data received in the third reception process; When a transmission timing arrives, the first master base station and the q1 first slave base stations transmit (q1+1) transmission frames to the wireless device through joint transmission; The wireless device may receive (q1+1) transmission frames transmitted by joint transmission between the first master base station and q1 first slave base stations, and may transmit a block acknowledgment to the first master base station.

[0607] This is because if a communication system has such a configuration, it is possible to transmit data from an access point to a wireless device while avoiding contention among multiple cooperating base station groups.

[0608] Furthermore, according to an embodiment of the present invention, the master base station A first cooperating base station group has a star configuration in which a master base station and a slave base station are directly connected to a switch via a backhaul, the first cooperating base station group including n1 (n1 is an integer equal to or greater than 1) first slave base stations, a determination unit that determines whether or not joint transmission is possible, in which the master base station and q1 (q1 is an integer satisfying 1≦q1≦n1) slave base stations among n1 (n1 is an integer equal to or greater than 1) first slave base stations jointly transmit data to a wireless device by CSMA / CA wireless communication using a communication channel consisting of one or more channels; a calculation unit that calculates padding having a length equal to a padding time and a data amount of each of the q1 transmission data to be allocated to each of the q1 first slave base stations when the determination unit determines that joint transmission is possible; q1 transmission data d each having q1 data amounts from q1 first slave base stations are transmitted via the switch via backhaul. 1_trsm ~d q1_trsm a wired unit that transmits the above signals to the q1 first slave base stations and transmits a joint transmission capability execution notification to cooperating base station groups other than the first cooperating base station group; Transmission frame F of the master base station of the first cooperating base station group mst_trsm a generation unit that performs a process of generating a transmission frame, which is a process of generating a transmission frame; A notification of transmission timing for notifying the wireless device of the timing for transmitting the transmission frame and padding are transmitted to the q1 first slave base stations by wireless communication, and when the transmission timing for the transmission frame arrives, a transmission frame F is transmitted by joint transmission. mst_trsmand a wireless unit that transmits the frame to the wireless device by wireless communication and receives a block Ack from the wireless device, which transmits an Ack in bulk to confirm reception of the frames.

[0609] This is because if the master base station is equipped with a wired unit, a determination unit, a calculation unit, a generation unit, and a wireless unit, data can be transmitted from the access point to the wireless device while avoiding contention among multiple base station groups.

[0610] Furthermore, according to an embodiment of the present invention, the program to be executed by a computer includes: A program for causing a computer to execute transmission of transmission data D_trsm in a master base station of a first cooperating base station group having a star configuration in which a master base station and a slave base station are directly connected to a switch via a backhaul, the first cooperating base station group including n1 (n1 is an integer equal to or greater than 1) first slave base stations, a first step in which a determination unit determines whether or not joint transmission is possible in which a master base station and q1 slave base stations jointly transmit data to a wireless device by wireless communication in a CSMA / CA system using a communication channel consisting of one or more channels; a second step in which, when it is determined in the first step that joint transmission is possible, the calculation unit calculates padding having a length equal to q1 data amounts of the q1 transmission data to be assigned to each of the q1 first slave base stations and a padding time; The wired unit transmits q1 pieces of transmission data d each having q1 amounts of data from q1 (q1 is an integer satisfying 1≦q1≦n1) first slave base stations among the n1 first slave base stations via a backhaul through a switch. 1_trsm ~d q1_trsm a third step of transmitting the q first slave base stations to the q first slave base stations and transmitting a notification of execution of joint transmission to cooperating base station groups other than the first cooperating base station group; The generating unit generates a transmission frame F of the master base station of the first cooperating base station group.mst_trsm a fourth step of performing a process of generating a transmission frame, which is a process of generating a The wireless unit transmits a notification of transmission timing, which notifies the wireless device of the timing of transmitting the transmission frame, and padding to the q1 first slave base stations by wireless communication, and when the transmission timing of the transmission frame arrives, the wireless unit transmits the transmission frame F by joint transmission. mst_trsm to the wireless device via wireless communication, and a fifth step of receiving a Block Ack from the wireless device, which is an Ack that collectively acknowledges reception of the frames.

[0611] This is because if the program causes a computer to execute the first to fifth steps, data can be transmitted from an access point to a wireless device while avoiding contention among multiple base station groups.

[0612] In an embodiment of the present invention, a conflict in a joint transmission JT means that a period of transmission data allocation communication in which a master base station of a first cooperating base station group that executes the joint transmission JT allocates transmission data to a slave base station of the first cooperating base station group via a switch 1 using a backhaul 4 overlaps at least partially with a period of transmission data allocation communication in which a master base station of a second cooperating base station group that executes the joint transmission JT allocates transmission data to a slave base station of the second cooperating base station group via a switch 1 using a backhaul 4.

[0613] In the embodiment of the present invention, the cooperating base station group AP_G1 constitutes a "first cooperating base station group," and the cooperating base station groups AP_G2 to AP_G m At least one of the cooperating base station groups constitutes a "second cooperating base station group."

[0614] Furthermore, in an embodiment of the present invention, determining "YES" in step S10 of the flowchart shown in Figures 11 and 12 corresponds to "satisfying the first condition that joint transmission by the first group of cooperating base stations can be initiated."

[0615] Furthermore, in the embodiment of the present invention, determining "YES" in step S11 of the flowchart shown in FIG. 11 and FIG. 12 means that "a joint transmission execution notification E is received from the second master base station of the second cooperating base station group." X-NOTF This corresponds to "satisfying the second condition, which consists of receiving

[0616] Furthermore, in the embodiment of the present invention, determining "NO" in step S12 of the flowchart shown in FIG. 11 and FIG. 12 means that the occupied time T OCCUPY This corresponds to "satisfying the third condition, namely that the

[0617] Furthermore, in an embodiment of the present invention, determining "NO" in step S11 of the flowchart shown in Figures 11 and 12 corresponds to "satisfying the fourth condition, which consists of not receiving a substantial notification of joint transmission from the second master base station of the second cooperating base station group."

[0618] Furthermore, in an embodiment of the present invention, executing step S23 of the flowcharts shown in Figures 19 and 20 corresponds to "satisfying the sixth condition, which consists of the first master base station of the first cooperating base station group obtaining from the second master base station the backhaul switching capacity to be occupied in data distribution to n2 second slave base stations, in place of the third and fourth conditions."

[0619] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the description of the above embodiments, and is intended to include all modifications within the meaning and scope of the claims. [Industrial Applicability]

[0620] The present invention is applied to a communication method, a communication system, a master base station, and a program to be executed by a computer. [Explanation of symbols]

[0621] 1 Switch, 2-1 to 2-m, 2-1A Master base station, 3-11 to 3-1n1, 3-1m to 3-1n m Slave base station, 4-1~4-m wireless device, 4 backhaul, 10,10A communication system, 11,21,31 antenna, 12 receiving unit, 13,13A,24,33 control unit, 14,22 wireless unit, 15,16,25 generation unit, 17,17A,23 wired unit, 18,18A calculation unit, 34 application.

Claims

1. A first cooperating base station group having a star configuration in which a master base station and a slave base station are directly connected to a switch by a backhaul, the first master base station and n １ (n １ a first cooperating base station group including n first slave base stations and a second cooperating base station group having the star configuration and including a second master base station, the second master base station and n ２ (n ２ a communication system including a first cooperating base station group including a first slave base station and a second cooperating base station group including a first slave base station and a second slave base station, the first cooperating base station group transmitting transmission data D_trsm to a wireless device using joint transmission in which a master base station and a slave base station jointly transmit data to the wireless device by wireless communication in a CSMA / CA system using a communication channel consisting of one or more channels, a first step of determining, when the first master base station receives the transmission data D_trsm from a transmission source, whether the joint transmission by the first cooperating base station group is possible; When the first master base station determines that the joint transmission is possible in the first step, １ q of the first slave base stations capable of the joint transmission １ (q １ is 1≦q １ ≦n １ (an integer satisfying １ q pieces of transmitted data １ a second step of calculating the amount of data; a third step in which the first master base station calculates padding having a length consisting of a padding time; a fourth step of transmitting, by the first master base station, a notification of execution of the joint transmission to the second cooperating base station group; After the fourth step, the first master base station notifies the wireless device of a timing for transmitting a transmission frame and the padding via wireless communication. １ a fifth step of transmitting to the first slave base stations; After the second step, the first master base station transmits the q １ q each having data amounts １ The q pieces of transmission data are １ a sixth step of transmitting to the first slave base stations; the first master base station and the q １ a seventh step in which each of the first slave base stations performs a transmission frame generation process, which is a process of generating a transmission frame based on the transmission data, after the second step; the first master base station and the q １ When the transmission timing arrives, the first slave base stations transmit (q １ an eighth step of transmitting the (+1) transmission frames to the wireless device by wireless communication; A communication method comprising: a ninth step in which the first master base station receives, after the eighth step, a block ACK from the wireless device, which collectively sends an ACK to confirm reception of the frame.

2. 2. The communication method according to claim 1, wherein the first master base station determines that the joint transmission by the first cooperating base station group is possible when the first master base station determines in the first step that the joint transmission by the first cooperating base station group does not conflict with the joint transmission by the second cooperating base station group.

3. 3. The communication method according to claim 2, wherein, in the first step, the first master base station determines that the joint transmission is possible when a first condition is satisfied, which is that the first cooperating base station group is able to start the joint transmission, a second condition is satisfied, which is that a notification of execution of the joint transmission has been received from the second master base station of the second cooperating base station group, and a third condition is satisfied, which is that the time is not within an occupied time of the joint transmission by the second cooperating base station group, or when a fourth condition is satisfied, which is that a notification of execution of the joint transmission has not been received from the second master base station of the second cooperating base station group, and the first condition is satisfied.

4. In the first step, the first master base station satisfies a fifth condition that the joint transmission is within an occupied time of the second cooperating base station group and that the second master base station of the second cooperating base station group is the nth cooperating base station. ２ q of the second slave base stations ２ (q ２ is 1≦q ２ ≦n ２ and a sixth condition, which is that the switching capacity of the switch to be occupied in data allocation to a number (an integer satisfying (a) above) of second slave base stations is obtained from the second master base station, in place of the third and fourth conditions, and the first and second conditions are satisfied, the communication method according to claim 3, wherein the method determines that the joint transmission is possible when the third and fourth conditions are satisfied and the first and second conditions are satisfied.

5. 2. The communication method according to claim 1, further comprising a tenth step, instead of the second to eighth steps, of transmitting a transmission frame including the transmission data D_trsm to the wireless device by wireless communication only by the first master base station when the first master base station determines in the first step that the first cooperating base station group cannot start the joint transmission, or when the first master base station receives a notification of execution of the joint transmission from the second master base station of the second cooperating base station group and determines that it is within an occupied time for the joint transmission by the second cooperating base station group.

6. The first master base station transmits the (q １ +1) the transmission frames to the wireless device and a second transmission time when only the first master base station transmits a transmission frame including the transmission data D_trsm to the wireless device, the first master base station and the q １ When it is determined in the first step that the first slave base stations will perform the joint transmission based on the first transmission time and the second transmission time, in the eighth step, when the transmission timing arrives, the first slave base stations perform the joint transmission by (q １ +1) the transmission frames to the wireless device via wireless communication.

7. 2. The communication method according to claim 1, wherein the sixth step and the seventh step are performed in parallel with the fifth step.

8. When the joint transmission by the first cooperating base station group and the joint transmission by the second cooperating base station group conflict with each other, in the sixth step, the first master base station １ The q pieces of transmission data are sent from the switch via the backhaul. １ The transmission rate when transmitting to the q first slave base stations is adjusted using the switching capacity occupied by the first cooperating base station group, and the adjusted transmission rate is used to １ The q pieces of transmission data are １ 2. The communication method according to claim 1, wherein the first slave base station transmits the first slave base station.

9. A first cooperating base station group having a star configuration in which a master base station and a slave base station are directly connected to a switch by a backhaul, the first master base station and n １ (n １ a first cooperating base station group including first slave base stations (wherein the first slave base station group is an integer equal to or greater than 1); a second cooperating base station group having the star configuration, the second master base station and n ２ (n ２ a second cooperating base station group including second slave base stations (wherein the second slave base station group is an integer equal to or greater than 1); a switch that receives data transmitted from either the first or second master base station via the backhaul and transmits the received data via the backhaul to a slave base station in the same cooperating base station group as the data transmission source; the first master base station of the first cooperating base station group, and １ q of the first slave base stations １ (q １ is 1≦q １ ≦n １ (q) first slave base stations, in which the master base station and the slave base stations transmit data to the wireless device in cooperation by wireless communication using one or more communication channels in accordance with the CSMA / CA method. １ +1) transmission frames or a wireless device that receives a transmission frame including the transmission data D_trsm transmitted only by the first master base station; The first master base station of the first cooperated base station group performs a first reception process when receiving a notification of execution of the joint transmission from the second master base station of the second cooperated base station group, and when determining that the joint transmission is possible, performs a first reception process when receiving a notification of execution of the joint transmission from the second master base station of the second cooperated base station group. １ q first slave base stations, respectively. １ q pieces of transmitted data １ a first calculation process for calculating the amount of data; a second calculation process for calculating padding having a length equal to a padding time; a first transmission process for transmitting a notification of execution of the joint transmission to the second cooperating base station group after the first and second calculation processes; and a transmission timing notification for notifying a timing of transmitting a transmission frame to a wireless device and the padding via wireless communication to the q data amounts. １ a second transmission process for transmitting to the q first slave base stations; １ q assigned to the first slave base stations respectively １ q each having data amounts １ The q pieces of transmission data are １ a third transmission process for transmitting to the q first slave base stations; a transmission frame generation process for generating a transmission frame based on its own transmission data after the first and second calculation processes; １ By joint transmission with the first slave base stations (q １ +1) transmit frames to the wireless device, and then receive a block ACK from the wireless device, which is an ACK that collectively acknowledges reception of the frames; The q １ The first slave base stations perform a third reception process of receiving the notification of the transmission timing from the first master base station, and a third reception process of transmitting the notification of the transmission timing from the first master base station via the switch and the backhaul. １ and a fourth receiving process of receiving the q pieces of transmission data from the first master base station, and １ Based on the transmitted data, １ executes a transmission frame generation process which is a process of generating transmission frames; the first master base station and the q １ When the transmission timing arrives, the first slave base stations transmit the (q １ +1) transmission frames to the wireless device; The wireless device communicates with the first master base station and the q １ The (q １ +1) transmission frames and transmit the Block Ack to the first master base station.

10. 10. The communication system according to claim 9, wherein the first master base station determines that the joint transmission by the first cooperating base station group is possible when it determines that the joint transmission by the first cooperating base station group does not conflict with the joint transmission by the second cooperating base station group.

11. 11. The communication system according to claim 10, wherein the first master base station determines that the joint transmission is possible when a first condition is satisfied, which is that the first cooperating base station group is able to start the joint transmission, a second condition is satisfied, which is that a notification of execution of the joint transmission has been received from the second master base station of the second cooperating base station group, and a third condition is satisfied, which is that the time is not within an occupied time of the joint transmission by the second cooperating base station group, or when a fourth condition is satisfied, which is that a notification of execution of the joint transmission has not been received from the second master base station of the second cooperating base station group, and the first condition is satisfied.

12. The first master base station satisfies a fifth condition that the joint transmission is within an occupied time of the second cooperating base station group, and the second master base station of the second cooperating base station group is in the nth ２ q of the second slave base stations ２ (q ２ is 1≦q ２ ≦n ２ 12. The communication system according to claim 11, wherein the joint transmission is determined to be possible when a sixth condition, which is that the switching capacity of the switch to be occupied in data allocation to a number of second slave base stations (an integer satisfying (a) above) is obtained from the second master base station, is satisfied in place of the third and fourth conditions, and the first and second conditions are satisfied.

13. 10. The communication system according to claim 9, wherein when the first master base station determines that the first cooperating base station group cannot start the joint transmission, or when the first master base station receives a notification of execution of the joint transmission from the second master base station of the second cooperating base station group and determines that the time is within an occupied time for the joint transmission by the second cooperating base station group, only the first master base station transmits a transmission frame including the transmission data D_trsm to the wireless device via the wireless communication.

14. The first master base station transmits the (q １ +1) the transmission frames to the wireless device and a transmission time when only the first master base station transmits a transmission frame including the transmission data D_trsm to the wireless device, and when it is determined that the joint transmission should not be performed, transmits a transmission frame including the transmission data D_trsm to the wireless device only by the first master base station; the first master base station and the q １ When the first master base station determines that the joint transmission is to be performed, the first slave base stations transmit (q １ +1) the transmission frames to the wireless device via wireless communication.

15. The communication system according to claim 9 , wherein the first master base station executes the second transmission process and the process of generating the transmission frame in parallel with the first transmission process.

16. When the joint transmission by the first cooperating base station group and the joint transmission by the second cooperating base station group conflict with each other, the first master base station determines whether or not the q １ The q pieces of transmission data are sent from the switch via the backhaul. １ The transmission rate when transmitting to the q first slave base stations is adjusted using the switching capacity occupied by the first cooperating base station group, and the adjusted transmission rate is used to １ The q pieces of transmission data are １ 10. The communication system of claim 9, wherein the first slave base station transmits to the first slave base station.

17. a first cooperating base station group having a star configuration in which a master base station and a slave base station are directly connected to a switch via a backhaul; １ (n １ is a master base station in a first cooperating base station group including first slave base stations (wherein The master base station and the n base station communicate with each other by wireless communication using a CSMA / CA method using a communication channel consisting of one or more channels. １ (n １ is an integer equal to or greater than 1) of the first slave base stations １ (q １ is 1≦q １ ≦n １ a determination unit for determining whether joint transmission is possible in which a number of slave base stations (an integer satisfying When the determination unit determines that the joint transmission is possible, １ q first slave base stations, respectively. １ Each of the q transmitted data １ a calculation unit for calculating padding having a length of the data amount and a padding time; The q １ The q first slave base stations １ q each having data amounts １ pieces of transmitted data d １＿ｔｒｓｍ ~d ｑ１＿ｔｒｓｍ Each of the q １ a wired unit configured to transmit a notification of execution of the joint transmission to the first slave base station and to transmit a notification of execution of the joint transmission to cooperating base station groups other than the first cooperating base station group; A transmission frame F of the master base station of the first cooperating base station group ｍｓｔ＿ｔｒｓｍ a generation unit that performs a process of generating a transmission frame, which is a process of generating a transmission frame; A notification of a transmission timing for notifying the timing of transmitting a transmission frame to the wireless device and the padding are transmitted to the wireless device via the wireless communication. １ When the transmission timing of the transmission frame arrives, the transmission frame F is transmitted to the first slave base station by the joint transmission. ｍｓｔ＿ｔｒｓｍ and a wireless unit that transmits the frame to the wireless device by wireless communication and receives a block Ack from the wireless device that collectively sends an Ack to confirm reception of the frame.

18. The cooperating base station group having the star configuration includes a second master base station and n ２ (n ２ is an integer equal to or greater than 1), and 18. The master base station according to claim 17, wherein the determination unit determines that the joint transmission by the first cooperating base station group is possible when it determines that the joint transmission by the first cooperating base station group does not conflict with the joint transmission by the second cooperating base station group.

19. 19. The master base station according to claim 18, wherein the determination unit determines that the joint transmission is possible when a first condition is satisfied, which is that the first cooperating base station group is able to start the joint transmission, a second condition is satisfied, which is that a notification of execution of the joint transmission has been received from the second master base station, and a third condition is satisfied, which is that the time is not within an occupied time of the joint transmission by the second cooperating base station group, or when a fourth condition is satisfied, which is that a notification of execution of the joint transmission has not been received from the second master base station, and the first condition are satisfied.

20. The determination unit determines a fifth condition that the second master base station of the second cooperating base station group is within an occupied time of the joint transmission by the second cooperating base station group and that the second master base station of the second cooperating base station group is within the occupied time of the joint transmission by the second cooperating base station group. ２ q of the second slave base stations ２ (q ２ is 1≦q ２ ≦n ２ 20. The master base station according to claim 19, wherein the master base station determines that the joint transmission is possible when it satisfies, instead of the third and fourth conditions, a sixth condition consisting of obtaining from the second master base station the switching capacity of the switch to be occupied in data allocation to a number (an integer satisfying

21. The master base station according to claim 17 , wherein the wireless unit transmits a transmission frame F_trsm including the transmission data D_trsm to the wireless device when the determination unit determines that the joint transmission is not possible.

22. When the joint transmission by the first cooperating base station group and the joint transmission by the second cooperating base station group conflict with each other, the wired unit １ pieces of transmitted data d １＿ｔｒｓｍ ~d ｑ１＿ｔｒｓｍ from the switch to the q １ The transmission rate when transmitting to the q first slave base stations is adjusted using the switching capacity occupied by the first cooperating base station group, and the adjusted transmission rate is used to １ pieces of transmitted data d １＿ｔｒｓｍ ~d ｑ１＿ｔｒｓｍ Each of the q １ 20. The master base station of claim 17, wherein the master base station transmits to the first slave base stations.

23. a first cooperating base station group having a star configuration in which a master base station and a slave base station are directly connected to a switch via a backhaul; １ (n １ a program for causing a computer to execute transmission of transmission data D_trsm at the master base station of a first cooperating base station group including first slave base stations (where D_trsm is an integer equal to or greater than 1), A determination unit communicates with the master base station by wireless communication using a communication channel consisting of one or more channels in accordance with CSMA / CA. １ a first step of determining whether joint transmission is possible in which the slave base stations jointly transmit data to the wireless device; When it is determined in the first step that the joint transmission is possible, the calculation unit １ q first slave base stations, respectively. １ q pieces of transmitted data １ a second step of calculating padding having a length consisting of the amount of data and a padding time; a third step in which the wired unit transmits a notification of execution of the joint transmission to the second cooperating base station group via the switch; The wireless unit transmits the padding and a transmission timing notification for notifying the timing of transmitting the transmission frame to the wireless device to the wireless device by wireless communication. １ a fourth step of transmitting to the first slave base stations; The wired unit transmits the n １ q of the first slave base stations １ (q １ is 1≦q １ ≦n １ (an integer satisfying １ The q data amounts each １ pieces of transmitted data d １＿ｔｒｓｍ ~d ｑ１＿ｔｒｓｍ Each of the q １ a fifth step of transmitting the execution notification of the joint transmission to the first slave base stations and transmitting the execution notification of the joint transmission to cooperating base station groups other than the first cooperating base station group; A generating unit generates a transmission frame F of the master base station of the first cooperating base station group. ｍｓｔ＿ｔｒｓｍ a sixth step of performing a process of generating a transmission frame, which is a process of generating a The wireless unit transmits the padding and a notification of a transmission timing for notifying the timing of transmitting the transmission frame to the wireless device to the wireless device by wireless communication. １ When the transmission timing of the transmission frame arrives, the transmission frame F is transmitted to the first slave base station by the joint transmission. ｍｓｔ＿ｔｒｓｍ a seventh step of transmitting the frame data to the wireless device via wireless communication, and receiving a block acknowledgment from the wireless device, the block acknowledgment being a batch of acknowledgments that confirm reception of the frames.

24. The cooperating base station group having the star configuration includes a second master base station and n ２ (n ２ is an integer equal to or greater than 1), and 24. The program for causing a computer to execute the program according to claim 23, wherein the determination unit determines that the joint transmission by the first cooperating base station group is possible when it determines in a first step that the joint transmission by the first cooperating base station group does not conflict with the joint transmission by the second cooperating base station group.

25. 25. The program for causing a computer to execute the program according to claim 24, wherein the determination unit determines that the joint transmission is possible when, in a first step, a first condition is satisfied that the first cooperating base station group is able to start the joint transmission, a second condition is satisfied that a notification of execution of the joint transmission has been received from the second master base station, and a third condition is satisfied that the second cooperating base station group is not within an occupied time for the joint transmission, or when a fourth condition is satisfied that a notification of execution of the joint transmission has not been received from the second master base station and the first condition are satisfied.

26. In the first step, the determination unit determines whether the second master base station of the second cooperating base station group is within an occupied time of the joint transmission by the second cooperating base station group and whether the second master base station of the second cooperating base station group is within the occupied time of the joint transmission by the second cooperating base station group. ２ q of the second slave base stations ２ (q ２ is 1≦q ２ 26. A program for causing a computer to execute the program described in claim 25, which determines that the joint transmission is possible when the third and fourth conditions are satisfied, and a sixth condition is satisfied in place of the third and fourth conditions, that is, the switching capacity of the switch to be occupied in data distribution to a number of second slave base stations (an integer satisfying ≦) is obtained from the second master base station, and the first and second conditions are satisfied.

27. 24. The program for causing a computer to execute the program according to claim 23, wherein, when the determination unit determines in the first step that the joint transmission is not possible, the wireless unit transmits a transmission frame F_trsm including the transmission data D_trsm to the wireless device in the seventh step.

28. When the joint transmission by the first cooperating base station group and the joint transmission by the second cooperating base station group conflict with each other, in the fifth step, the wired unit １ pieces of transmitted data d １＿ｔｒｓｍ ~d ｑ１＿ｔｒｓｍ from the switch to the q １ The transmission rate when transmitting to the q first slave base stations is adjusted using the switching capacity occupied by the first cooperating base station group, and the adjusted transmission rate is used to １ pieces of transmitted data d １＿ｔｒｓｍ ~d ｑ１＿ｔｒｓｍ Each of the q １ 24. The program for causing a computer to execute the program according to claim 23, wherein the program transmits the first slave base station to the first slave base station.

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