Communication systems, programs, and computer-readable recording media containing those programs.

Abstract

To provide a communication system that can cover a wide area without requiring synchronization.SOLUTION: A plurality of base stations 1-5 are arranged so as to have communication ranges covering communication spaces different from each other, in the communication spaces between a terminal device 20 that is a transmission source and the base stations, and receive a packet broadcast from the terminal device 20 without synchronizing with each other. A control device 6 receives packets from the base stations 1-5 by wired communication, generates reception packets by performing reception processing on the received packets, and transmits the generated reception packets to a terminal device 30 that is a transmission destination via a network NW. The reception processing includes decoding coded packets, eliminating duplicate packets, and rearranging packets in order of sequence numbers.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a communication system, a program, and a computer-readable recording medium on which the program is stored. [Background technology]

[0002] There are high expectations for wireless connectivity in various on-site applications, particularly in manufacturing and logistics, as IoT technology is introduced to improve production efficiency. This includes the need to transmit video, audio, and other data in real time from objects and people moving around the site, such as Automated Guided Vehicles (AGVs), mobile trays in logistics warehouses, or workers, for use in image diagnosis and work support.

[0003] From a communication speed perspective, it is not difficult to run these applications using common communication technologies such as IEEE 802.11ax. However, in manufacturing and logistics settings, the downtime of these applications directly impacts production and work throughput, requiring a level of stability beyond simple operation.

[0004] Various communication technologies, such as wide-area communication technologies like LTE (Long Time Revolution) and 5G, as well as broadband communication using millimeter waves, are being attempted to be applied to manufacturing and logistics sites. Among these, wireless LAN (Local Area Network) based on IEEE 802.11, which has become widespread as so-called Wi-Fi, is considered a communication technology that is often considered as a candidate for introduction because it has many advantages that meet the requirements of the site, such as the availability and cost of equipment and the relative ease of self-maintenance.

[0005] Conventionally, in order to operate multiple access points in coordination, experiments have been conducted in actual automated warehouse systems in which signals simulating real-time communication are transmitted from movable parts used for loading and unloading goods, and these signals are simultaneously received at multiple receiving points simulating access points, thereby investigating the practical feasibility of simultaneous reception by multiple access points (Non-Patent Document 1). [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] Yoshihisa Kondo, "Basic Experiments in an Automated Warehouse System for Cooperative Operation of Multiple Wireless LAN Access Points," IEICE RCS Workshop, RCC2018-95. [Overview of the project] [Problems that the invention aims to solve]

[0007] However, as described in Non-Patent Document 1, simultaneous reception by multiple access points has the problem that high-precision synchronization between access points is required.

[0008] Furthermore, Wi-Fi has the problem of having limited coverage, requiring switching between multiple base stations to cover a wide area, resulting in poor communication quality near the network edge, and requiring base stations to be densely packed to improve edge communication quality.

[0009] Therefore, according to this embodiment of the invention, a communication system is provided that does not require synchronization and can cover a wide area.

[0010] Furthermore, according to an embodiment of this invention, a program is provided that can be executed in a communication system that does not require synchronization and can cover a wide area.

[0011] Furthermore, according to an embodiment of this invention, a computer-readable recording medium is provided that stores a program executed in a communication system that does not require synchronization and can cover a wide area. [Means for solving the problem]

[0012] (Composition 1) According to an embodiment of this invention, the communication system comprises a plurality of base stations and a control device. The plurality of base stations are arranged to have a communication range that covers mutually different communication spaces in the communication space with the source, and receive packets broadcast from the source. The control device receives packets from the plurality of base stations, performs reception processing on the received packets to generate received packets, and transmits the generated received packets to the destination via the network.

[0013] (Configuration 2) In Configuration 1, when the packets received from multiple base stations consist of encoded packets, the control device, in the reception process, decodes the encoded packets to obtain multiple individual packets, resolves duplication among the multiple individual packets, and rearranges the multiple individual packets with the duplication resolved so that they are in the order of their sequence numbers to generate a received packet.

[0014] (Composition 3) In configuration 2, the control device solves a system of simultaneous equations representing multiple encoded packets to obtain multiple individual packets.

[0015] (Composition 4) In Configuration 1, when the control device receives packets from multiple base stations and these packets consist of a combined packet formed by adding an encoded packet to a first standalone packet, the control device decodes the encoded packet of the combined packet to obtain multiple second standalone packets, resolves any duplication between the first standalone packet and the multiple second standalone packets, and then rearranges the multiple third standalone packets, which have had the duplication resolved, in the order of their sequence numbers to generate a received packet.

[0016] (Composition 5) In configuration 4, the sequence numbers of the multiple second standalone packets are smaller than the sequence numbers of the first standalone packets.

[0017] (Composition 6) In configuration 5, when the encoded packet contains n (where n is an integer greater than or equal to 1) second individual packets, the control device receives n distinct combined packets and solves a system of n equations representing the n encoded packets contained in the n combined packets to obtain multiple second individual packets.

[0018] (Composition 7) In Configuration 1, when the control device receives packets from multiple base stations, consisting of multiple individual packets, it resolves the duplication of the multiple individual packets during the reception process, rearranges the duplicated individual packets in the order of their sequence numbers, and generates a new received packet.

[0019] (Composition 8) In any of configurations 1 through 7, multiple base stations receive packets broadcast from a source without synchronizing with each other.

[0020] (Composition 9) Furthermore, according to an embodiment of this invention, the communication system comprises a control device and a plurality of base stations. The control device receives packets transmitted from a source via the network, encodes the received packets to generate encoded packets, and performs an allocation process to distribute the generated encoded packets to the plurality of base stations. The plurality of base stations are arranged in the communication space between them and the destination so that they have communication ranges that cover mutually different communication spaces, and each receives the packets allocated by the allocation process from the control device and broadcasts the received packets to the destination.

[0021] (Composition 10) In configuration 9, the control device distributes the encoded packets equally among multiple base stations during the allocation process.

[0022] (Composition 11) In configuration 9, the control device, in the allocation process, allocates coded packets to multiple base stations such that the sum of the number of coded packets transmitted by all of the multiple base stations is minimized.

[0023] (Composition 12) In configuration 9, the control device, in the allocation process, allocates a first number of encoded packets to one base station when the density of base stations around one base station is a first density, and allocates a second number of encoded packets (less than the first number) to one base station when the density of base stations is a second density (higher than the first density), and does this for all of the multiple base stations, thereby allocating encoded packets to multiple base stations.

[0024] (Composition 13) In configuration 12, each of the first and second densities is determined based on the received signal strength when one base station receives a signal from a base station in its vicinity.

[0025] (Composition 14) Furthermore, according to an embodiment of this invention, the program is a program executed in a communication system that receives a packet broadcast from a source and transmits it to a destination, The communication system comprises multiple base stations arranged to have a communication range that covers mutually different communication spaces in the communication space between the source and the system, and which receive packets broadcast from the source. The program is The receiving means performs a first step of receiving the packets from multiple base stations, The processing means performs a reception process on the packet received in the first step to generate a received packet in the second step, The transmission means is a program that causes a computer to perform a third step of sending the received packets generated in the second step to a destination via the network.

[0026] (Composition 15) In configuration 14, when the packets received from multiple base stations in the first step consist of encoded packets, the processing means, in the reception processing of the second step, decodes the encoded packets to obtain multiple individual packets, resolves duplication among the multiple individual packets, and rearranges the multiple individual packets from which duplication has been resolved so that they are in the order of their sequence numbers to generate a received packet.

[0027] (Composition 16) In configuration 15, the processing means, in the reception processing of the second step, solves a system of simultaneous equations representing a plurality of encoded packets to obtain a plurality of individual packets.

[0028] (Composition 17) In configuration 14, when the packets received from multiple base stations in the first step consist of a combined packet obtained by adding an encoded packet to a first standalone packet, the processing means, in the reception processing of the second step, decodes the encoded packet of the combined packet to obtain multiple second standalone packets, eliminates duplication between the first standalone packet and the multiple second standalone packets, and rearranges the multiple third standalone packets obtained from which the duplication has been eliminated so that they are in the order of their sequence numbers to generate a received packet.

[0029] (Composition 18) In configuration 17, the sequence numbers of multiple second standalone packets are smaller than the sequence numbers of the first standalone packets.

[0030] (Composition 19) In configuration 18, when the encoded packet contains n (where n is an integer greater than or equal to 1) second individual packets, the processing means, in the receiving process of the second step, when it receives n mutually distinct combined packets, solves a system of simultaneous equations consisting of n equations representing the n encoded packets contained in the n combined packets to obtain a plurality of second individual packets.

[0031] (Composition 20) In configuration 14, when the packets received from multiple base stations in the first step consist of multiple individual packets, the processing means, in the reception processing of the second step, eliminates duplication among the multiple individual packets and rearranges the multiple individual packets from which the duplication has been eliminated so that they are in the order of their sequence numbers to generate a received packet.

[0032] (Composition 21) In any of configurations 14 to 20, multiple base stations receive packets broadcast from a source without synchronizing with each other.

[0033] (Composition 22) Furthermore, according to an embodiment of this invention, the program is a program executed in a communication system that receives packets from a source and broadcasts them to a destination, The communication system comprises multiple base stations arranged to have communication ranges that cover mutually different communication spaces in the communication space between the system and the destination, and which broadcast packets to the destination. The first step is for the receiving means to receive a packet from the source via the network, The processing means comprises a second step of encoding the packet received in the first step to generate an encoded packet, The processing means performs an allocation process to distribute the encoded packets to multiple base stations, The transmission means is a program that causes a computer to perform a fourth step of sending coded packets, which have been allocated by the allocation process, to multiple base stations.

[0034] (Composition 23) In configuration 22, the processing means distributes the encoded packets equally among multiple base stations in the allocation process of the third step.

[0035] (Composition 24) In configuration 22, the processing means, in the allocation process of the third step, allocates coded packets to multiple base stations such that the sum of the number of coded packets transmitted by all of the multiple base stations is minimized.

[0036] (Composition 25) In configuration 22, the processing means, in the allocation process of the third step, allocates a first number of encoded packets to one base station when the density of base stations around one base station is a first density, and allocates a second number of encoded packets, which is less than the first number, to one base station when the density of base stations is a second density which is higher than the first density, and does this for all of the multiple base stations, thereby allocating the encoded packets to the multiple base stations.

[0037] (Composition 26) In configuration 25, each of the first and second densities is determined based on the received signal strength when one base station receives a signal from a base station in its vicinity.

[0038] (Composition 27) Furthermore, according to an embodiment of this invention, the recording medium is a computer-readable recording medium on which a program described in any of configurations 14 to 26 is recorded. [Effects of the Invention]

[0039] It does not require synchronization and can cover a wide area. [Brief explanation of the drawing]

[0040] [Figure 1] This is a schematic diagram of a communication system according to an embodiment of the present invention. [Figure 2]Figure 1 is a schematic diagram of the control device shown. [Figure 3] Figure 1 is a schematic diagram of the terminal device 20. [Figure 4] This is a conceptual diagram illustrating image transmission. [Figure 5] This is a schematic diagram showing the packet format. [Figure 6] Figure 3 is a schematic diagram of the buffer shown. [Figure 7] This is a diagram illustrating how packets are encoded. [Figure 8] This diagram illustrates how encoded packets are generated when sending MBurst packets PKT_N(1) to PKT_N(MBurst). [Figure 9] This diagram illustrates how packets that make up a burst are transmitted. [Figure 10] This diagram illustrates an alternative method for transmitting packets that make up a burst. [Figure 11] This diagram illustrates yet another method of transmitting the packets that make up a burst. [Figure 12] This diagram illustrates yet another method of transmitting the packets that make up a burst. [Figure 13] Figure 3 is a flowchart illustrating the operation of the terminal device shown. [Figure 14] Figure 13 is a flowchart illustrating the detailed operation of step S8. [Figure 15] Figure 3 is another flowchart illustrating the operation of the terminal device shown. [Figure 16] Figure 1 is a flowchart illustrating the operation of the communication system 10. [Figure 17] Figure 16 is a flowchart illustrating the detailed operation of step S27. [Figure 18] Figure 16 is a flowchart illustrating the detailed operation of step S29. [Figure 19]Figure 16 is a flowchart illustrating the detailed operation of step S30. [Figure 20] This figure shows the changes in the N buffer and C buffer when receiving packets that make up a burst. [Figure 21] This is a schematic diagram of another communication system according to an embodiment of the present invention. [Figure 22] Figure 21 is a schematic diagram of the control device shown. [Figure 23] This is a schematic diagram of the correspondence table TBL1. [Figure 24] This is a schematic diagram of the correspondence table TBL2. [Figure 25] This is a schematic diagram of the correspondence table TBL3. [Figure 26] Figure 21 is a flowchart illustrating the operation of the communication system shown. [Figure 27] Figure 26 is a flowchart illustrating the detailed operation of step S101. [Figure 28] Figure 26 is another flowchart illustrating the detailed operation of step S101. [Figure 29] Figure 26 is a flowchart illustrating the detailed operation of step S103. [Modes for carrying out the invention]

[0041] Embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and their descriptions will not be repeated.

[0042] Figure 1 is a schematic diagram of a communication system according to an embodiment of the present invention. Referring to Figure 1, the communication system 10 according to an embodiment of the present invention comprises base stations 1 to 5 and a control device 6. The base stations 1 to 5 and the control device 6 are arranged in a wireless communication space.

[0043] Base stations 1 to 5 are connected to the control device 6 via wired cables. Furthermore, base stations 1 to 5 are positioned at different locations within the communication space between them and the terminal device 20, which is the source of packets, so as to cover different communication spaces.

[0044] An application (not shown) takes an image using a camera, for example, and transmits a packet containing the image data of the captured image as a payload to the terminal device 20. When the terminal device 20 receives the packet from the application, it broadcasts the received packet using one of the following methods: a single packet PKT_N, an encoded packet PKT_C, or a combined packet (consisting of a single packet PKT_N with an encoded packet PKT_C added to it).

[0045] Base stations 1 to 5 receive packets broadcast from terminal device 20 via wireless communication and transmit the received packets to control device 6 via wired communication.

[0046] The packets received by base stations 1-5 from terminal device 20 consist of either single packets, coded packets, or combined packets.

[0047] The control device 6 receives packets (either single packets, encoded packets, or combined packets) from base stations 1 to 5 via wired communication.

[0048] Then, when the control device 6 receives a packet (either a single packet, an encoded packet, or a combined packet) from base stations 1 to 5, it performs reception processing on the received packet (either a single packet, an encoded packet, or a combined packet).

[0049] More specifically, when the control device 6 receives individual packets from base stations 1 to 5, in the reception process, it eliminates duplicate individual packets, rearranges the individual packets after eliminating the duplicates so that they are in the order of their sequence numbers, and generates a new received packet.

[0050] Furthermore, when the control device 6 receives a combined packet from base stations 1 to 5, in the reception process, it decodes the encoded packet of the combined packet using a method described later to obtain individual packets, resolves any duplication between the obtained individual packets and the individual packets of the combined packet, and rearranges the individual packets with the duplication resolved in the order of their sequence numbers to generate a received packet.

[0051] Furthermore, when the control device 6 receives an encoded packet from base stations 1 to 5, in the reception process, it decodes the encoded packet using a method described later to obtain individual packets, eliminates duplicates in the obtained individual packets, and rearranges the individual packets with the duplicates eliminated in the order of their sequence numbers to generate a received packet.

[0052] When the control device 6 generates a received packet, it sends the received packet to the destination terminal device 30 via the network NW.

[0053] Figure 2 is a schematic diagram of the control device 6 shown in Figure 1. Referring to Figure 2, the control device 6 comprises a receiving means 61, a processing means 62, an N buffer 63, and a C buffer 64.

[0054] The receiving means 61 receives packets PKT (either single packets PKT_N, encoded packets PKT_C, or combined packets PKT_CB) from base stations 1 to 5 via wired communication, and outputs the received packets PKT (either single packets PKT_N, encoded packets PKT_C, or combined packets PKT_CB) to the processing means 62.

[0055] When the processing means 62 receives a single packet PKT_N from the receiving means 61, it performs N-packet reception processing on the single packet PKT_N using a method described later. In this case, if the single packet PKT_N has not been received during the N-packet reception processing, the processing means 62 stores the single packet PKT_N in the N buffer 63. Then, the processing means 62 transmits all the single packets PKT_N stored in the N buffer 63 to the terminal device 30 via the network NW.

[0056] On the other hand, when the processing means 62 receives the combined packet PKT_CB from the receiving means 61, it performs a separation process to separate the encoded packet PKT_C and the individual packet PKT_N from the combined packet PKT_CB. Then, the processing means 62 performs an N-packet reception process on the separated individual packet PKT_N. The processing means 62 also performs a removal process to remove the information of the individual packet PKT_N (i.e., the received individual packet PKT_N) stored in the N buffer 63 from the encoded packet PKT_C. If the encoded packet PKT_C' after the removal process contains multiple individual packets PKT_N, the processed packet PKT_C' is stored in the C buffer 64. Subsequently, the processing means 62 performs a decoding process, described later, on the encoded packet PKT_C' stored in the C buffer 64. In this case, the processing means 62 performs an N-packet reception process on the individual packet PKT_N that was decoded in the decoding process.

[0057] When the processing means 62 receives the encoded packet PKT_C from the receiving means 61, it sequentially performs the removal process and decoding process described above without performing the separation process described above.

[0058] Terminal device 20 receives a single packet PKT_N from the application. Then, terminal device 20 transmits the single packet PKT_N to base stations 1-5 via wireless communication as a packet constituting real-time traffic, using a method described later.

[0059] Figure 3 is a schematic diagram of the terminal device 20 shown in Figure 1. Referring to Figure 3, the terminal device 20 comprises a buffer 21, a processing means 22, a transmission means 23, and an antenna 24.

[0060] Buffer 21 stores multiple packets PKT_N(1) to PKT_N(V) that have arrived from the application (not shown). Each of the multiple packets PKT_N(1) to PKT_N(V) consists of a raw (native) packet generated by the application. V is an integer.

[0061] The processing means 22 has a built-in timer. The processing means 22 determines whether or not a packet has arrived. When the processing means 22 determines that a packet has arrived, it stores a copy of the arrived packet PKT_N(v) (where v is an integer from 1 to V) in the buffer 21 and outputs the original packet PKT_N(v) to the transmission means 23. Also, when the processing means 22 determines that a packet has arrived, if multiple packets are stored in the buffer 21, it takes out multiple packets from the buffer 21, generates an encoded packet PKT_C based on the multiple packets taken out using the method described later, and outputs the generated encoded packet PKT_C to the transmission means 23. Furthermore, the processing means 22 takes out multiple packets from the buffer 21, encodes the multiple packets taken out to generate an encoded packet PKT_C, and adds the generated encoded packet to a single packet PKT_N to generate a combined packet PKT_CB. The processing means 22 then outputs the combined packet PKT_CB to the transmission means 23. The processing means 22, referring to the timer, outputs either a single packet PKT_N(v), an encoded packet PKT_C, or a combined packet PKT_CB to the transmission means 23.

[0062] When the transmitting means 23 receives one of the single packet PKT_N(v), encoded packet PKT_C, or combined packet PKT_CB from the processing means 22, it broadcasts one of the received single packet PKT_N(v), encoded packet PKT_C, or combined packet PKT_CB to base stations 1 to 5 via wireless communication through the antenna 24.

[0063] Figure 4 is a conceptual diagram illustrating image transmission. Referring to Figure 4, the characteristics of real-time video transmission are explained. The I-picture consists of a compressed image that does not use the difference between preceding and succeeding pictures, and is therefore large in size. The P-picture transmits the difference between it and the previous picture, and is therefore small in size.

[0064] I-pictures and P-pictures are transmitted periodically. The number of packets transmitted during periodic transmissions differs, and sometimes packets are sent all at once in bursts. Also, I-pictures are generated and transmitted periodically, like IPPPIPPPIP.

[0065] When transmitting iPictures, bursts occur, and the size of these bursts is not constant. Furthermore, the packets that make up a burst do not arrive all at once, but sequentially.

[0066] Furthermore, in the P-picture, P-picture, P-picture, I-picture, P-picture, P-picture, P-picture, I-picture, and P-picture shown in Figure 4, the time interval between packets containing a P-picture in the payload and packets containing an I-picture in the payload arriving from the application to the terminal device 20 is T interval_1 Therefore, the time interval at which multiple packets containing an I-picture in their payload arrive consecutively from the application to the terminal device 20 is T interval_1 Shorter than T interval_2 That is the case.

[0067] Figure 5 is a schematic diagram showing the packet format. Referring to Figure 5, a packet (PKT) includes a header and a payload. The header includes the destination IP address.

[0068] The payload includes Packet Info, region REG1, Coded Info, and region REG2. Region REG1 contains the payload of one packet PKT_N. Region REG2 contains the coded packet PKT_C obtained by coding N individual packets PKT_N(1) to PKT_N(N). The length of region REG1 is L p and the length of region REG2 is the maximum value of L1 to L n . L p is the data length of one individual packet PKT_N, and L1 to L n are respectively the data lengths of the individual packets PKT_N(1) to PKT_N(N).

[0069] Packet Info includes the identifier N / C, the sequence number SN, and the data length L p . The identifier N / C is an identifier for identifying whether the packet included in region REG1 is an individual packet PKT_N or a coded packet PKT_C, and consists of "N" or "C". "N" represents that it is an individual packet PKT_N, and "C" represents that it is a coded packet PKT_C. The sequence number SN represents the order of arrival of the packet included in region REG1 at the terminal device 20. The data length L p represents the length of region REG1.

[0070] Coded Info includes the identifier N / C, Num coded(N), and Packet Info 1 to Packet Info N. The identifier N / C is an identifier for identifying whether the packet included in region REG2 is an individual packet PKT_N or a coded packet PKT_C, and consists of "N" or "C". Num coded(N) represents the number of individual packets PKT_N that make up the coded packet PKT_C included in region REG2.

[0071] Packet Info 1 includes the sequence number SN, the data length L1, and the code C1. Similarly, hereinafter, Packet Info N includes the sequence number SN, the data length L N and the code CN including the following.

[0072] In Packet Info 1, the sequence number SN represents the arrival order of the individual packet PKT_N(1) that constitutes the encoded packet PKT_C at the terminal device 20, the data length L1 is the data length of the individual packet PKT_N(1) that constitutes the encoded packet PKT_C, and the code C1 is the coefficient of the packet PKT_N(1) when encoding N individual packets PKT_N(1) to PKT_N(N).

[0073] Similarly hereinafter, in Packet Info N, the sequence number SN represents the arrival order of the individual packet PKT_N(N) that constitutes the encoded packet PKT_C at the terminal device 20, the data length L N is the data length of the individual packet PKT_N(N) that constitutes the encoded packet PKT_C, and the code C N is the coefficient of the individual packet PKT_N(N) when encoding N individual packets PKT_N(1) to PKT_N(N).

[0074] One packet PKT_N has a configuration in which the payload includes Packet Info and the region REG1.

[0075] If there are M Burst (M Burst is an integer satisfying 2 ≤ M Burst < V) individual packets PKT_N(1) to PKT_N(M Burst ) that are transmitted burstily at once, then among the M Burst individual packets PKT_N(1) to PKT_N(M Burst ), excluding the first individual packet PKT_N(1) that arrives at the terminal device 20, the other (M Burst - 1) individual packets PKT_N(2) to PKT_N(M BurstWhen each of the a (where a is an integer greater than or equal to 1) predetermined individual packets PKT_N(m) selected from arrives at the terminal device 20, the individual packets PKT_N(1) to PKT_N(m-1) that arrived at the terminal device 20 earlier than the predetermined individual packets PKT_N(m) are encoded to generate encoded packets PKT_C1, and the generated encoded packets PKT_C1 are attached to the predetermined packets PKT_N(m) to generate a combined packet PKT_N / PKT_C1.

[0076] Therefore, the combined packet PKT_N / PKT_C1 consists of a payload that includes [Packet Info / PKT_N data / Coded Info / PKT_N(1) data ~ PKT_N(m-1) data].

[0077] Also, M Burst Individual single packets PKT_N(1)~PKT_N(M Burst When ) arrives at terminal device 20 in succession, M Burst Individual single packets PKT_N(1)~PKT_N(M Burst This will generate an encoded packet PKT_C2 that encodes ).

[0078] Therefore, the encoded packet PKT_C2 is the data of [Coded Info / PKT_N(1) ~PKT_N(M Burst It consists of a configuration that includes data from )

[0079] Figure 6 is a schematic diagram of the buffer 21 shown in Figure 3. Note that Figure 6 shows the number of packets M to be transmitted in burst mode at once. Burst A schematic diagram of buffer 21 is shown for the case where the size of buffer 21 is larger than the specified size.

[0080] Referring to Figure 6, buffer 21 consists of, for example, a ring buffer. Then, buffer 21 is arranged in M ​​in ascending order of sequence number SN (i.e., oldest first). Burst Individual single packets PKT_N(1)~PKT_N(M Burst ) stores a single packet PKT_N(MBurst ) is a packet stored in buffer 21 at the current time, and a single packet PKT_N(1) ~ packet PKT_N(M Burst -1) is a packet that was previously stored in buffer 21.

[0081] Furthermore, buffer 21 is configured to overwrite older packets first when the number of packets exceeds the maximum number. As a result, buffer 21 can always store the maximum number of packets.

[0082] Single packet PKT_N(1), PKT_N(2), ..., PKT_N(M Burst ) stored in M Burst Each of these areas contains, respectively, the sequence number SN1 and data length L1 of a single packet PKT_N(1), the sequence number SN2 and data length L2 of a single packet PKT_N(2), ..., a single packet PKT_N(M Burst Sequence number SN MBurst and data length L MBurst It is also stored.

[0083] That is, a single packet PKT_N(PKT_N(1)~PKT_N(M Burst ) one of the above constitutes the payload, and each region of buffer 21 contains [SN / L p The / payload / padding(all "0")] is stored here. Note that the padding(all "0") is [SN / L p This is added if the length of the [ / payload] does not reach the maximum length.

[0084] Figure 7 is a diagram illustrating how packets are encoded. In Figure 7, packet X i (i is 1, 2, 3, ...) and encoded packet Y i-1 This explains how to encode and.

[0085] Refer to Figure 7, Packet X i L i Since it has a data length of bytes, packet X iis L i ×8 / n components X i,1 , X i,2 , X i,3 , X i,4 , ···, X i,Li×8 / n and padding consisting of "0". Component X i,1 , X i,2 , X i,3 , X i,4 , ···, X i,Li×8 / n each has a length of n (n is a positive integer) bits. Code C i is composed of a random number of n-bit length over the Galois field GF(2 n ). Here, n is, for example, 8.

[0086] Encoded packet Y i-1 is composed of components Y i-1,1 , Y i-1,2 , Y i-1,3 , Y i-1,4 , ···, Y i-1,Li×8 / n , Y i-1,Max×8 / n Each of the components Y i-1,1 , Y i-1,2 , Y i-1,3 , Y i-1,4 , ···, Y i-1,Li×8 / n , Y i-1,Max×8 / n each has a length of n bits.

[0087] Code C i is multiplied by each of the components X i,1 , X i,2 , X i,3 , X i,4 , ···, X i,Li×8 / n to generate multiplication results C i ·X i,1 , C i ·X i,2 , C i ·X i,3 , C i ·X i,4 , ···, C i ·X i,Li×8 / n In this case, code C i and components X i,1 , X i,2 , X i,3 , X i,4 , ···, X i,Li×8 / nThe multiplication with each of them is performed as multiplication over the Galois field GF(2 n ).

[0088] After that, the exclusive OR of the multiplication result C i ·X i,1 and the component Y i-1,1 is computed to generate the component Y i,1 , the exclusive OR of the multiplication result C i ·X i,2 and the component Y i-1,2 is computed to generate the component Y i,2 , the exclusive OR of the multiplication result C i ·X i,3 and the component Y i-1,3 is computed to generate the component Y i,3 , the exclusive OR of the multiplication result C i ·X i,4 and the component Y i-1,4 is computed to generate the component Y i,4 , and subsequently, in the same manner, the exclusive OR of the multiplication result C i ·X i,Li×8 / n and the component Y i-1,Li×8 / n is computed to generate the component Y i,Li×8 / n , and further, the exclusive OR of the padding consisting of "0" and the component Y i-1,Max×8 / n is computed to generate the component Y i,Max×8 / n . Thus, the encoded packet Y i = [Y i,1 , Y i,2 , Y i,3 [[ID=5x]], Y i,4 , ···, Y i,Li×8 / n , ···, Y i,Max×8 / n is generated.

[0089] FIG. 8 is a diagram for explaining a method of generating an encoded packet when transmitting M Burst individual packets PKT_N(1) to PKT_N(M Burst ).

[0090] In FIG. 8, it is assumed that it is determined to transmit an encoded packet to base stations 1 to 5 at the timing when packets P3, P5, P7, and P9 arrive at the terminal device

[0091] Referring to (a) of FIG. 8, M that constitutes a burst Burst individual packets PKT_N(1) to PKT_N(M Burst ) consist of packets P1 to P6. And the maximum number of packets that can be stored in buffer 21 is 6. That is, the number M of packets that constitute a burst Burst is the size M of buffer 21 Buffer is as follows.

[0092] When packet P1 arrives at terminal device 20, processing means 22 of terminal device 20 copies packet P1 to buffer 21 (see (i) of (a) in FIG. 8). Then, processing means 22 extracts packet P1 from buffer 21, and encodes the extracted packet P1 by the method described in FIG. 7 to generate encoded packet C1.

[0093] More specifically, processing means 22 generates encoded packet Y0 = {000···0} consisting of n-bit "0", and generates code C1 consisting of an n-bit random number on Galois field GF(2 n ). Then, processing means 22 generates encoded packet Y1 (= C1) by the method described in FIG. 7 based on packet X1 (= P1), encoded packet Y0 = {000···0}, and code C1.

[0094] After that, when packet P2 arrives at terminal device 20, processing means 22 copies packet P2 to buffer 21 (see (ii) of (a) in FIG. 8). Then, processing means 22 extracts packet P2 from buffer 21. After that, processing means 22 generates code C2 consisting of an n-bit random number on Galois field GF(2 n ). Then, processing means 22 generates encoded packet Y2 (= C2) by the method described in FIG. 7 based on packet X2 (= P2), encoded packet Y1, and code C2.

[0095] Similarly, when packets P3 to P6 arrive at the terminal device 20, encoded packets Y3 to Y6 (=C3 to C6) are generated sequentially (see Figure 8 (a), (iii), to (vi)). In this case, when packet P6 arrives at the terminal device 20 and is copied to buffer 21, buffer 21 has a maximum capacity of M Buffer Stores the packet.

[0096] When packet P3 arrives at terminal device 20, processing means 22 copies packet P3 to buffer 21 (see Figure 8(a)(iii)) and determines to transmit an encoded packet. Then, processing means 22 adds the encoded packet Y2 (=C2) generated at the time packet P2 arrives at terminal device 20 to packet P3 to generate a combined packet P3 / C2, and outputs the generated combined packet P3 / C2 to transmission means 23 to transmit the combined packet P3 / C2 to base stations 1-5. Note that transmitting information using combined packet P3 / C2 is information transmission by piggyback.

[0097] Furthermore, when packet P5 arrives at terminal device 20, processing means 22 copies packet P5 to buffer 21 (see Figure 8(a)(v)) and determines to transmit the encoded packet. Then, processing means 22 adds the encoded packet Y4 (=C4) generated at the time packet P4 arrives at terminal device 20 to packet P5 to generate combined packet P5 / C4, and outputs the generated combined packet P5 / C4 to transmission means 23 to transmit combined packet P5 / C4 to base stations 1-5.

[0098] Then, after packet P6 arrives at terminal device 20 and an encoded packet Y6 (=C6) is generated, processing means 22 determines, by a method described later, that packet P6 is the last packet P6 among packets P1 to P6 that constitute a burst, and then outputs the untransmitted encoded packet Y6 (=C6) to transmission means 23 and transmits the encoded packet Y6 (=C6) to base stations 1 to 5 individually.

[0099] Furthermore, the processing means 22 retrieves packets P1 to P6 from the buffer 21, encodes the retrieved packets P1 to P6, and generates encoded packet Y7 (=C7). Then, the processing means 22 outputs the encoded packet Y7 (=C7) to the transmission means 23 and transmits the encoded packet Y7 (=C7) independently to base stations 1 to 5.

[0100] Thus, the processing means 22 determines the number of packets M that make up the burst. Burst The buffer size is M Buffer When the following conditions are met, an encoded packet Y7 (=C7) containing all packets P1 to P6 that make up the burst is generated and transmitted to base stations 1 to 5.

[0101] Refer to Figure 8(b) and the M that make up the burst Burst Individual single packets PKT_N(1)~PKT_N(M Burst ) is packet P1~P 10 It consists of the following. The maximum number of packets that can be stored in buffer 21 is 6. That is, the number of packets that make up a burst is M. Burst The size of buffer 21 is M Buffer It is larger than that.

[0102] When packets P1 to P6 arrive at the terminal device 20, the processing means 22 executes the processing described in Figure 8(a) (see Figure 8(b)(i) and (ii)).

[0103] Then, when packet P7 arrives at the terminal device 20, the processing means 22 copies packet P7 to buffer 21 (see Figure 8(b)(iii)). As a result, when packet P6 arrives at the terminal device 20, packets P1 to P6 that were stored in buffer 21 are overwritten by packets P2 to P7, respectively.

[0104] Processing means 22 copies packet P7 to buffer 21, and then retrieves packet P7 from buffer 21. Then, processing means 12 processes the Galois field GF(2 nA code C7 consisting of an n-bit random number is generated. Then, the processing means 22 generates an encoded packet Y7 (=C7) based on packet X7 (=P7), encoded packet Y6, and code C7, in the manner described in Figure 7.

[0105] Subsequently, the processing means 22 processes packets P8~P 10 When the packets arrive at terminal device 20, the encoded packets Y8 (=C8) ~ Y are processed in the same manner. 10 (=C 10 This generates (see Figure 8(b),(iv)~(vi)).

[0106] And then, packet P 10 Once it has been copied to buffer 21, buffer 21 contains packets P5~P 10 Store it.

[0107] Processing means 22 processes packet P 10 The encoded packet Y arrives at terminal device 20. 10 (=C 10 After generating ), packet P is generated using the method described later. 10 Packets P1-P that constitute the burst 10 The last packet P 10 After determining that this is the case, the unsent coded packet Y 10 (=C 10 ) is output to the transmission means 23 and encoded packet Y 10 (=C 10 ) is transmitted to base stations 1-5 independently.

[0108] Furthermore, the processing means 22 processes packets P5~P from buffer 21. 10 Extract the extracted packets P5~P 10 Encode and encode packet Y 11 (=C 11 The processing means 22 generates the encoded packet Y. 11 (=C 11 ) is output to the transmission means 23 and encoded packet Y 11 (=C 11 ) is transmitted to base stations 1-5 independently.

[0109] Thus, the processing means 22 determines the number of packets M that make up the burst. Burst The buffer size is M Buffer When it is greater than, packets P1~P make up the burst. 10 Among packets P5~P 10 Encoded packet Y containing 11 (=C 11 Generate a signal and transmit it to base stations 1-5.

[0110] As explained in Figure 8, a single encoded packet is the number of packets M that make up a burst. Burst and buffer size M Buffer It contains different packets depending on their relative size.

[0111] Furthermore, the processing means 22 processes the M that constitute the burst. Burst Individual single packets PKT_N(1)~PKT_N(M Burst ) The last single packet PKT_N(M Burst Whether or not the data has arrived at buffer 21 is determined by the following method.

[0112] The processing means 22 determines the number of bursts M contained in the first single packet that constitutes the burst. Burst Based on this, it is determined whether the last single packet of the burst has arrived in buffer 21.

[0113] More specifically, each time a single packet arrives, the processing means 22 processes the arriving single packet according to the burst size M. Burst Determine whether it contains and the number of bursts M for the incoming single packet. Burst When it includes, the number of bursts M from the arriving single packet Burst The processing means 22 then detects the number of bursts M Burst From a single packet containing M Burst When the first single packet arrives, it is determined that the last single packet of the burst has arrived in buffer 21.

[0114] Further, every time a single packet arrives, the processing means 22 determines whether the arrived single packet includes a flag indicating that it is the last single packet of a burst. When the arrived single packet includes the flag indicating that it is the last single packet of a burst, it is determined that the last single packet of the burst has arrived at the buffer 21.

[0115] In FIG. 8, it was described that the terminal device 20 attaches the encoded packet PKT_C to the single packet PKT_N and transmits it to the base stations 1 to 5. However, in the embodiment of this invention, every time one single packet PKT_N arrives at the buffer 21, the terminal device 20 may encode the single packet PKT_N stored in the buffer 21 to generate an encoded packet PKT_C, and transmit the generated encoded packet PKT_C to the base stations 1 to 5.

[0116] More specifically, when the processing means 22 copies packet P1 to buffer 21, it encodes packet P1 stored in buffer 21 to generate encoded packet C1, and outputs the generated encoded packet C1 to the transmission means 23 to transmit encoded packet C1 to base stations 1-5 independently (see Figure 8(a)(i)). Also, when the processing means 22 copies packet P2 to buffer 21, it encodes packets P1 and P2 stored in buffer 21 to generate encoded packet C2, and outputs the generated encoded packet C2 to the transmission means 23 to transmit encoded packet C2 to base stations 1-5 independently (see Figure 8(a)(ii)). Furthermore, when the processing means 22 copies packet P3 to buffer 21, it encodes packets P1, P2, and P3 stored in buffer 21 to generate encoded packet C3, and outputs the generated encoded packet C3 to the transmission means 23 to transmit encoded packet C3 to base stations 1-5 independently (see Figure 8(a)(iii)). Furthermore, when the processing means 22 copies packet P4 to buffer 21, it encodes packets P1, P2, P3, and P4 stored in buffer 21 to generate encoded packet C4, and outputs the generated encoded packet C4 to the transmission means 23 to transmit encoded packet C4 to base stations 1 to 5 independently (see Figure 8(a)(iv)). Furthermore, when the processing means 22 copies packet P5 to buffer 21, it encodes packets P1, P2, P3, P4, and P5 stored in buffer 21 to generate encoded packet C5, and outputs the generated encoded packet C5 to the transmission means 23 to transmit encoded packet C5 to base stations 1 to 5 independently (see Figure 8(a)(v)). Furthermore, when the processing means 22 copies packet P6 to buffer 21, it encodes packets P1, P2, P3, P4, P5, and P6 stored in buffer 21 to generate encoded packet C6, and outputs the generated encoded packet C6 to the transmission means 23 to transmit the encoded packet C6 to base stations 1 to 5 individually (see Figure 8(a)(vi)).In the case shown in Figure 8(b), the processing means 22 similarly generates an encoded packet PKT_C based on the packet stored in buffer 21 each time a single packet PKT_N arrives, outputs the generated encoded packet PKT_C to the transmission means 23, and transmits the encoded packet PKT_C to base stations 1 to 5 individually.

[0117] Alternatively, the terminal device 20 may transmit single packets PKT_N that do not constitute a burst, and single packets PKT_N that constitute a burst, as they are to base stations 1 to 5. In this case, each time a single packet PKT_N arrives, the processing means 22 copies the arrived single packet PKT_N to buffer 21, outputs the original single packet PKT_N to the transmission means 23, and transmits the original single packet PKT_N to base stations 1 to 5 individually.

[0118] Thus, in this embodiment of the invention, when the terminal device 20 receives a single packet PKT_N from an application, it transmits either the single packet PKT_N, the encoded packet PKT_C, or the combined packet PKT_N / PKT_C to base stations 1 to 5.

[0119] Figure 9 is a diagram illustrating the transmission method of packets that make up a burst. In Figure 9, the M packets that make up the burst Burst The number of packets PKT_N(1)~PKT_N(M Burst When the packets P1 to P6 constitute the burst, Burst The number of packets PKT_N(1)~PKT_N(M Burst The method for transmitting the packets will be explained. In this case, the processing means 22 will determine, for example, to transmit the encoded packet when either packet P3 or P5 arrives at the terminal device 20, and will determine not to transmit the encoded packet when any of packets P1, P2, P4, or P6 arrives at the terminal device 20. It will also be assumed that packets P1 and P3 could not be transmitted to the destination.

[0120] Referring to Figure 9, packets P1 to P6 constitute packets that are transmitted in bursts at once.

[0121] When packet P1 arrives at terminal device 20, processing means 22 processes packet P1 by burst number M Burst It is determined that it contains M packets from packet P1. Burst The system detects this. The processing unit 22 then copies packet P1 to buffer 21 and determines that packet P1 is a packet other than packets P3 and P5 (i.e., packet P1 is a single packet PKT_N(1) with m=1), and therefore does not transmit the encoded packet. The processing unit 22 then outputs the original packet P1 to the transmission unit 23 and transmits packet P1 to base stations 1 to 5. After that, the processing unit 22 retrieves packet P1 from buffer 21 and encodes the retrieved packet P1 using the method described above to generate encoded packet C1. Encoded packet C1 is represented by the following equation.

[0122]

number

[0123] Subsequently, when packet P2 arrives at the terminal device 20, processing means 22 detects that the second packet constituting the burst has arrived. Processing means 22 then copies packet P2 to buffer 21 and determines that since packet P2 is a packet other than packets P3 and P5 (i.e., packet P2 is a single packet PKT_N(2) with m=2), it does not transmit the encoded packet. Processing means 22 then outputs the original packet P2 to transmission means 23 and transmits packet P2 to base stations 1-5. After that, processing means 22 retrieves packets P1 and P2 from buffer 21 and encodes the retrieved packets P1 and P2 using the method described above to generate encoded packet C2. Encoded packet C2 is represented by the following equation.

[0124]

number

[0125] Subsequently, when packet P3 arrives at the terminal device 20, processing means 22 detects that the third packet constituting the burst has arrived. Processing means 22 then copies packet P3 to buffer 21 and determines that packet P3 is a packet corresponding to either packet P3 or P5 (i.e., packet P3 is a single packet PKT_N(3) with m=3), and therefore decides to transmit an encoded packet. Processing means 22 then adds the encoded packet C2 generated when packet P2 arrived at the terminal device 20 to the original packet P3 to generate a combined packet P3 / C2, and outputs the generated combined packet P3 / C2 to transmission means 23 to transmit the combined packet P3 / C2 to base stations 1-5. After that, processing means 22 takes packets P1-P3 out of buffer 21 and encodes the taken packets P1-P3 using the method described above to generate an encoded packet C3. Encoded packet C3 is represented by the following equation.

[0126]

number

[0127] Subsequently, when packet P4 arrives at terminal device 20, processing means 22 detects that the fourth packet constituting the burst has arrived. Processing means 22 then copies packet P4 to buffer 21 and determines that since packet P4 is a packet other than packets P3 and P5 (i.e., packet P4 is a single packet PKT_N(4) with m=4), it does not transmit the encoded packet. Then, processing means 22 outputs the original packet P4 to transmission means 23 and transmits packet P4 to base stations 1 to 5. Processing means 22 then retrieves packets P1 to P4 from buffer 21 and encodes the retrieved packets P1 to P4 using the method described above to generate encoded packet C4. Encoded packet C4 is represented by the following equation.

[0128]

number

[0129] Subsequently, when packet P5 arrives at terminal device 20, processing means 22 detects that the fifth packet constituting the burst has arrived. Processing means 22 then copies packet P5 to buffer 21 and determines that packet P5 is a packet corresponding to either packet P3 or P5 (i.e., packet P5 is a single packet PKT_N(5) with m=5), and therefore decides to send an encoded packet. Processing means 22 then adds the encoded packet C4 generated when packet P4 arrived at terminal device 20 to the original packet P5 to generate a combined packet P5 / C4, and outputs the generated combined packet P5 / C4 to transmission means 23 to send the combined packet P5 / C4 to base stations 1-5. Subsequently, processing means 22 takes packets P1-P5 from buffer 21 and encodes the taken packets P1-P5 using the method described above to generate an encoded packet C5. Encoded packet C5 is represented by the following equation.

[0130]

number

[0131] Subsequently, when packet P6 arrives at the terminal device 20, the processing means 22 detects that the sixth packet constituting the burst (i.e., the last packet constituting the burst) has arrived. The processing means 22 then copies packet P6 to buffer 21 and determines that since packet P6 is a packet other than packets P3 and P5 (i.e., since packet P6 is a single packet PKT_N(6) with m=6), it does not transmit the encoded packet. In that case, the processing means 22 outputs the original packet P6 to the transmission means 23 and transmits packet P6 to base stations 1 to 5. After that, the processing means 22 takes packets P1 to P6 out of buffer 21 and encodes the taken packets P1 to P6 using the method described above to generate the encoded packet C6. The encoded packet C6 is represented by the following equation.

[0132]

number

[0133] The reason why encoded packet C6 is not attached to packet P6 and sent to base stations 1-5 is that the timing for attaching the encoded packet to a standalone packet and sending it to base stations 1-5 is determined to be when either packet P3 or P5 arrives at buffer 21, and the timing when packet P6 arrives at buffer 21 is not the timing for attaching the encoded packet to a standalone packet and sending it to base stations 1-5.

[0134] Subsequently, the processing means 22 determines whether T milliseconds have elapsed since the last packet P6 of the burst packets P1 to P6 arrived at buffer 21. Here, T is T <T _interval_1 This is the time that satisfies the condition, for example, 5 milliseconds.

[0135] When the processing means 22 determines that T milliseconds have elapsed since the last packet P6 arrived at the buffer 21, it outputs the encoded packet C6 to the transmission means 23 and transmits the encoded packet C6 to base stations 1 to 5.

[0136] The processing means 22 then determines whether the number of encoded packets to be transmitted is K. K is, for example, 3. K may also be changed depending on the number of packets stored in buffer 21. In this case, K is determined by K = A + B / M. M is the number of packets stored in buffer 21, and A and B are constants. Each of A, B, and M is a positive integer. If the result of the calculation A + B / M is not a positive integer, the result of the calculation A + B / M is rounded to the first decimal place. According to K = A + B / M, if the number of packets M stored in buffer 21 is large, K becomes small, and if the number of packets M stored in buffer 21 is small, K becomes large. Therefore, by determining the number of encoded packets to be transmitted K using the formula K = A + B / M, when the number of packets M stored in buffer 21 is a first number, the number of encoded packets to be transmitted K is set to the first number, and when the number of packets M stored in buffer 21 is a second number greater than the first number, the number of encoded packets to be transmitted K is set to a second number less than the first number. In other words, if the number of packets M stored in buffer 21 decreases, more encoded packets will be transmitted.

[0137] When the processing means 22 determines that the number of encoded packets to be transmitted is not K, it retrieves packets P1 to P6 stored in the buffer 21, encodes the retrieved packets P1 to P6 using the method described above, and generates encoded packet C7. Encoded packet C7 is represented by the following equation.

[0138]

number

[0139] Then, the processing means 22 outputs the encoded packet C7 to the transmission means 23 and transmits the encoded packet C7 to base stations 1 to 5.

[0140] Subsequently, the processing means 22 determines that the number of encoded packets to be transmitted is not K (=3). Then, the processing means 22 retrieves packets P1 to P6 stored in buffer 21 and encodes the retrieved packets P1 to P6 using the method described above to generate encoded packet C8. Encoded packet C8 is represented by the following equation.

[0141]

number

[0142] Then, the processing means 22 outputs the encoded packet C8 to the transmission means 23 and transmits the encoded packet C8 to base stations 1 to 5.

[0143] Thus, when the processing means 22 transmits an encoded packet individually, it generates encoded packets C6 to C8 using all packets P1 to P6 stored in the buffer 21.

[0144] Subsequently, the processing means 22 determines that the number of encoded packets to be transmitted is K (=3), and clears the buffer 21.

[0145] As shown in equations (6) to (8), encoded packets C6, C7, and C8 contain the same packets P1 to P6, and coefficient C i Only the coefficient C is different in the encoded packets. i is Galois field GF(2 n ) consists of n-bit random numbers, so for example, the coefficient a in equation (6) 62 ,a 64 It can also be zero. In this case, encoded packet C6 will effectively contain packets P1, P3, P5, and P6. The same applies to encoded packets C7 and C8.

[0146] Base stations 1-5 fail to receive packet P1 transmitted from terminal device 20 and receive packet P2 transmitted from terminal device 20. Also, base stations 1-5 fail to receive coupled packet P3 / C2 transmitted from terminal device 20 and sequentially receive packet P4, coupled packet P5 / C4, packet P6, and encoded packets C6, C7, and C8 transmitted from terminal device 20.

[0147] Then, base stations 1-5 transmit the received packets P2, P4, P6, combined packet P5 / C4, and encoded packets C6, C7, C8 to control device 6 via wired communication.

[0148] The control device 6 receives packets P2, P4, P6, combined packet P5 / C4, and encoded packets C6, C7, C8 from base stations 1 to 5.

[0149] Since the control device 6 was unable to receive packets P1, P3 and encoded packet C1, it removes the information of the received packets P2 and P4 from encoded packets C4 and C6 in order to decode the unreceived packets P1 and P3 from encoded packets C4 and C6.

[0150] More specifically, the control device 6 removes the information of received packets P2 and P4 from encoded packet C4 using the following formula.

[0151]

number

[0152] Furthermore, the control device 6 removes the information of the received packets P2, P4, P5, and P6 from the encoded packet C6 using the following formula.

[0153]

number

[0154] As a result, encoded packet C4', obtained by removing the information of received packets P2 and P4 from encoded packet C4, and encoded packet C6', obtained by removing the information of received packets P2, P4, P5, and P6 from encoded packet C6, both contain packets P1 and P3.

[0155] The left-hand side of equation (9) is obtained by performing the exclusive OR operation on encoded packet C4 and packet P2, and then performing the exclusive OR operation on the result of that exclusive OR operation with packet P4. Similarly, the left-hand side of equation (10) is obtained by performing the exclusive OR operation on encoded packet C6 and packet P2, then performing the exclusive OR operation on the result of that exclusive OR operation with packet P4, then performing the exclusive OR operation on the result of that exclusive OR operation with packet P5, and finally performing the exclusive OR operation on the result of that exclusive OR operation with packet P6. Thus, the control device 6 can obtain the values ​​of the left-hand sides of equations (9) and (10).

[0156] Also, the sign a in equation (9) 41 ,a 43 This is included in the "Coded Info" of coded packet C4, and the code a of equation (10) 61 ,a 63 This is known because it is included in the "Coded Info" of encoded packet C6 (see Figure 5).

[0157] Therefore, the control device 6 can decode the unreceived packets P1 and P3 by solving the simultaneous equations in equations (9) and (10).

[0158] Similarly, the control device 6 can decode packets P1 and P3 that could not be received based on two coded packets arbitrarily selected from coded packets C6 to C8.

[0159] Thus, if the two packets P1 and P3 were not received by the control device 6, the terminal device 20 can decode the two unreceived packets P1 and P3 by transmitting an amount equal to or greater than the number of packets that the control device 6 could not receive (=2 packets).

[0160] The following explains how the two unreceived packets can be decoded using the method described above, in the case where the control device 6 fails to receive combined packets P5 / C2 instead of combined packets P3 / C2. In this case, the control device 6 fails to receive the two packets P1 and P5.

[0161] Therefore, the control device 6 calculates encoded packet C2' after removing the information of the received packet P2 from encoded packet C2, and encoded packet C6'' after removing the information of the received packets P2, P3, P4, and P6 from encoded packet C6, using the following formula.

[0162]

number

[0163] Therefore, the control device 6 can decode the two packets P1 and P5 that could not be received by solving the simultaneous equations (11A) and (11B).

[0164] Even if packets P1, P2, and P4, other than packets P3 and P5 to which encoded packets C2 and C4 are assigned respectively, cannot be sent to the control device 6, the control device 6 can still receive the three encoded packets C6, C7, and C8.

[0165] Therefore, the control device 6 removes the information of the received packets P3, P5, and P6 from the encoded packet C6. (3) And, the encoded packet C7 after removing the information of the received packets P3, P5, and P6 from encoded packet C7. (3) And, the encoded packet C8 after removing the information of the received packets P3, P5, and P6.(3) We calculate the following. As a result, we obtain the following equation.

[0166]

number

[0167] The control device 6 can decode packets P1, P2, and P4 by solving the simultaneous equations (12A), (12B), and (12C).

[0168] Furthermore, when the encoded packet C, after removing the information of previously received packets from the encoded packet, contains only one packet, the control device 6 converts the encoded packet C into a single packet PKT_N using the following formula.

[0169]

number

[0170] In this case, the control device 6 substitutes the encoded packet C from which the information of the received packet has been removed into “Y” in equation (13), and substitutes one code C contained in any of the encoded packets C from which the information of the received packet has been removed into “C” in equation (13). Note that the operation in equation (13) is performed on the Galois field GF(2 n This is an operation performed on ).

[0171] Figure 10 is a diagram illustrating another method of transmitting packets that constitute a burst. Referring to Figure 10, the processing means 22 generates encoded packets C1 to C6 each time it copies packets P1 to P6 to buffer 21, as described in Figure 9.

[0172] When packet P2 arrives at terminal device 20, processing means 22 copies packet P2 to buffer 21, adds encoded packet C1 to packet P2 to generate combined packet P2 / C1, and outputs the generated combined packet P2 / C1 to transmission means 23 to transmit combined packet P2 / C1 to base stations 1 to 5.

[0173] Subsequently, the processing means 22 generates encoded packet C2, and when packet P3 arrives at terminal device 20, copies packet P3 to buffer 21, adds encoded packet C2 to packet P3 to generate combined packet P3 / C2, outputs the generated combined packet P3 / C2 to transmission means 23, and transmits combined packet P3 / C2 to base stations 1 to 5.

[0174] Furthermore, the processing means 22 generates an encoded packet C3, and when packet P4 arrives at the terminal device 20, copies packet P4 to buffer 21, adds the encoded packet C3 to packet P4 to generate a combined packet P4 / C3, and outputs the generated combined packet P4 / C3 to the transmission means 23 to transmit the combined packet P4 / C3 to base stations 1 to 5.

[0175] Furthermore, the processing means 22 generates an encoded packet C4, and when packet P5 arrives at the terminal device 20, copies packet P5 to buffer 21, adds the encoded packet C4 to packet P5 to generate a combined packet P5 / C4, and outputs the generated combined packet P5 / C4 to the transmission means 23 to transmit the combined packet P5 / C4 to base stations 1 to 5.

[0176] Furthermore, the processing means 22 generates an encoded packet C5, and when packet P6 arrives at the terminal device 20, copies packet P6 to buffer 21, adds encoded packet C5 to packet P6 to generate a combined packet P6 / C5, and outputs the generated combined packet P6 / C5 to the transmission means 23 to transmit the combined packet P6 / C5 to base stations 1-5. Note that encoded packet C5 includes packets P1-P5 (see equation (5)), but when generating a combined packet by adding encoded packet C to packet P6, which is the last packet P1-P6 to arrive at the terminal device 20 among the packets P1-P6 that constitute the burst, encoded packet C includes all packets P1-P6 stored in buffer 21. Therefore, the encoded packet C5 in the combined packet P6 / C5 includes all packets P1-P6 as shown in Figure 10, rather than equation (5) above.

[0177] Thus, the transmission of coded packets using Piggyback may be performed in each of the packets P2 to P6 among the packets P1 to P6 that constitute the burst.

[0178] After transmitting the combined packet P6 / C5 to base stations 1-5, the processing means 22 transmits the encoded packets C6-C8 individually to base stations 1-5, as explained in Figure 9.

[0179] Figure 11 illustrates yet another method of transmitting packets that make up a burst.

[0180] Referring to Figure 11, the processing means 22 generates encoded packets C1 to C6 each time it copies packets P1 to P6 to buffer 21, as described in Figure 9.

[0181] When packets P2 to P5 arrive at terminal device 20, processing means 22 does not attach encoded packets C1 to C4 to packets P2 to P5, but instead transmits packets P2 to P5 individually to base stations 1 to 5.

[0182] Then, when packet P6 arrives at terminal device 20, processing means 22 adds encoded packet C5 to packet P6 to generate combined packet P6 / C5, and outputs the generated combined packet P6 / C5 to transmission means 23 to transmit combined packet P6 / C5 to base stations 1-5. In this case as well, encoded packet P5 does not consist of the above equation (5), but rather includes all packets P1-P6 as shown in Figure 11.

[0183] Thus, transmission of coded packets using Piggyback may be performed only in the last packet P6 of the burst packets P1 to P6.

[0184] After transmitting the combined packet P6 / C5 to base stations 1-5, the processing means 22 transmits the encoded packets C6-C8 individually to base stations 1-5, as explained in Figure 9.

[0185] As explained in Figures 9 to 11, in this embodiment of the invention, the transmission of encoded packets by combined packets (i.e., transmission of encoded packets by piggyback) only needs to be performed when one or more packets selected from packets P2 to P6, which constitute the burst, arrive at the terminal device 20.

[0186] Figure 12 illustrates yet another method for transmitting packets that make up a burst. In Figure 12, the method for transmitting packets that make up a burst is explained in the case where an encoded packet PKT_C is generated each time a packet that makes up a burst arrives at terminal device 20 and transmitted to base stations 1 to 5.

[0187] Referring to Figure 12, when packet P1 arrives at terminal device 20, processing means 22 copies packet P1 to buffer 21. Then, processing means 22 retrieves packet P1 from buffer 21 and encodes the retrieved packet P1 using the method described above to generate encoded packet C1. After that, processing means 22 outputs encoded packet C1 to transmission means 23 and transmits encoded packet C1 to base stations 1 to 5 individually.

[0188] Furthermore, when packet P2 arrives at terminal device 20, processing means 22 copies packet P2 to buffer 21, retrieves packets P1 and P2 from buffer 21, and encodes the retrieved packets P1 and P2 using the method described above to generate encoded packet C2. Then, processing means 22 outputs encoded packet C2 to transmission means 23 and transmits encoded packet C2 to base stations 1 to 5 individually.

[0189] Furthermore, when packet P3 arrives at terminal device 20, processing means 22 copies packet P3 to buffer 21, retrieves packets P1, P2, and P3 from buffer 21, and encodes the retrieved packets P1, P2, and P3 using the method described above to generate encoded packet C3. Then, processing means 22 outputs encoded packet C3 to transmission means 23 and transmits encoded packet C3 to base stations 1 to 5 individually.

[0190] Furthermore, when packet P4 arrives at terminal device 20, processing means 22 copies packet P4 to buffer 21, retrieves packets P1, P2, P3, and P4 from buffer 21, and encodes the retrieved packets P1, P2, P3, and P4 using the method described above to generate encoded packet C4. Then, processing means 22 outputs encoded packet C4 to transmission means 23 and transmits encoded packet C4 to base stations 1 to 5 individually.

[0191] Furthermore, when packet P5 arrives at terminal device 20, processing means 22 copies packet P5 to buffer 21, retrieves packets P1, P2, P3, P4, and P5 from buffer 21, and encodes the retrieved packets P1, P2, P3, P4, and P5 using the method described above to generate encoded packet C5. Then, processing means 22 outputs encoded packet C5 to transmission means 23 and transmits encoded packet C5 to base stations 1 to 5 individually.

[0192] Furthermore, when packet P6 arrives at terminal device 20, processing means 22 copies packet P6 to buffer 21, retrieves packets P1, P2, P3, P4, P5, and P6 from buffer 21, and encodes the retrieved packets P1, P2, P3, P4, P5, and P6 using the method described above to generate encoded packet C6. Then, processing means 22 outputs encoded packet C6 to transmission means 23 and transmits encoded packet C6 to base stations 1 to 5 individually.

[0193] Subsequently, the processing means 22 generates encoded packets C7 to C9 and transmits each of the generated encoded packets C7 to C9 individually to base stations 1 to 5.

[0194] In this manner, the terminal device 20 generates an encoded packet PKT_C each time a packet constituting the burst arrives, and transmits the generated encoded packet PKT_C to base stations 1 to 5 independently.

[0195] Although not shown in the diagram, terminal device 20 transmits each packet constituting the burst to base stations 1-5 as is (i.e., without generating an encoded packet PKT_C).

[0196] Figure 13 is a flowchart illustrating the operation of the terminal device 20 shown in Figure 3.

[0197] Referring to Figure 13, when the terminal device 20 starts operating, the processing means 22 sets the sequence number SN to SN=0 (step S1). Then, the processing means 22 determines whether or not the packet has arrived at the buffer 21 (step S2).

[0198] In step S2, when it is determined that packet PKT_N has arrived at buffer 21, the processing means 22 sets SN = SN + 1 (step S3), adds the sequence number SN and packet length L to packet PKT_N, and copies the sequence number SN, packet length L, and packet PKT_N to buffer 21 (step S4). As a result of step S3 being executed, the sequence number SN, which indicates the order in which the packets arrived at buffer 21 (i.e., terminal device 20), is stored in buffer 21 along with packet PKT_N and packet length L.

[0199] Subsequently, the processing means 22 determines whether or not to transmit the encoded packet C (step S5). As explained in Figures 9 to 11, the transmission of the encoded packet by concatenation (i.e., transmission of the encoded packet by piggyback) is performed when one or more packets selected from packets P2 to P6, which constitute the burst, arrive at the terminal device 20. Piggyback The packet P is determined in advance, and the determined packet P Piggyback When it arrives at buffer 21 (i.e., terminal device 20), processing means 22 determines to send encoded packet C, and packet P Piggyback If any packet other than the specified one arrives at buffer 21 (i.e., terminal device 20), it is determined that encoded packet C will not be sent.

[0200] In step S5, when it is determined to send encoded packet C, the encoded packet is attached to the N packet PKT_N (step S6) to generate a combined packet.

[0201] Then, in step S5, if it is determined that encoded packet C will not be transmitted, or after step S6, the processing means 22 outputs the packet to the transmitting means 23, and the transmitting means 23 transmits the packet from the processing means 22 to base stations 1 to 5 via the antenna 24 (step S7).

[0202] Subsequently, the processing means 22 generates encoded packet C from the packets stored in buffer 21 using the method described above (step S8).

[0203] Then, the series of operations proceeds to step S2.

[0204] On the other hand, if it is determined in step S2 that the packet did not arrive at buffer 21, the processing means 22 determines whether T milliseconds have elapsed since the last packet arrived at buffer 21 (step S9).

[0205] In step S9, when it is determined that T milliseconds have elapsed since the last packet arrived at buffer 21, the processing means 22 outputs the encoded packet C to the transmitting means 23, and the transmitting means 23 transmits the encoded packet C received from the processing means 22 to base stations 1 to 5 via antenna 24 (step S10).

[0206] Subsequently, the processing means 22 determines whether the number of encoded packets C transmitted is K or not (step S11).

[0207] In step S11, if it is determined that the number of encoded packets C sent is not K, the processing means 22 generates encoded packets C from the packets stored in buffer 21 (step S12). Subsequently, the series of operations proceeds to step S10, and steps S10 to S12 are repeatedly executed until it is determined in step S11 that the number of encoded packets C sent is K.

[0208] Then, in step S11, if it is determined that the number of encoded packets C sent is K, the processing means 22 clears the buffer 21 (step S13). After that, the series of operations proceeds to step S2. Also, in step S9, if it is determined that T milliseconds have not elapsed since the last packet arrived at buffer 21, the series of operations proceeds to step S2.

[0209] Figure 14 is a flowchart illustrating the detailed operation of step S8 shown in Figure 13.

[0210] Referring to Figure 14, after step S7 in Figure 13, the processing means 22 sets i=1 (step S81). Here, i is an argument that indicates the sequence number SN of each packet stored in buffer 21 at the time step S8 in Figure 13 is executed. i=1 represents the oldest packet among the packets stored in buffer 21.

[0211] After step S81, the processing means 22 generates an encoded packet Y0 = {000···0} consisting of "0"s with a length of n bits (step S82).

[0212] Then, the processing means 22 processes packet X from buffer 21. i Obtain (step S83).

[0213] Subsequently, the processing means 22 processes the Galois field (GF(2 n A random number of n bits is generated by )), and the generated random number of n bits is then processed by C i Store in (step S84).

[0214] Then, the processing means 22 processes packet X i Each element X i,1 ~X i,Li×8 / n C i Multiply by C i ·X i and Y i-1 The exclusive OR operation is performed with Y. That is, the processing means 22 performs the following operation: i Calculate (Step S85).

[0215]

number

[0216] Subsequently, the processing means 22 processes packet X i Sequence number SN i , packet length L i and code C i Add this to the Coded info (step S86).

[0217] Then, the processing means 22 determines whether i = I or not (step S87). Here, I represents the maximum value of the sequence number SN of the packets stored in the buffer 21 at the time step S8 in Figure 13 is executed.

[0218] In step S87, if it is determined that i=I is not true, the processing means 22 sets i=i+1 (step S88). The series of operations then proceeds to step S83, and steps S83 to S88 are repeatedly executed until it is determined in step S87 that i=I.

[0219] Then, in step S87, if it is determined that i=I, the processing means 22 will Y i A coded packet consisting of the and coded info is generated (step S89).

[0220] Subsequently, the series of operations proceeds to step S2 in Figure 13.

[0221] Furthermore, the detailed operation of step S12 in Figure 13 is also performed according to the flowchart shown in Figure 14. In this case, if it is determined in step S11 of Figure 13 that the number of encoded packets to be transmitted is not K, steps S81 to S89 are executed sequentially, and after step S89, the series of operations proceeds to step S10 of Figure 13.

[0222] As long as the terminal device 20 is powered, it repeatedly executes steps S1 to S13 (including the flowchart shown in Figure 14) as shown in Figure 13.

[0223] In the flowchart shown in Figure 13 (including the flowchart shown in Figure 14), after step S1 is executed, if the processing means 22 determines in step S2 that a packet PKT_N(1) (a packet showing the P picture shown in Figure 4) that does not constitute a burst has arrived at buffer 21, it sequentially executes steps S3 and S4 described above, then in step S5 determines not to transmit the encoded packet C, and in step S7 transmits the packet PKT_N(1) to base stations 1 to 5 via the transmitting means 23 and antenna 24.

[0224] Subsequently, in step S8, the processing means 22 generates an encoded packet C, and after step S8, the series of operations proceeds to step S2.

[0225] Then, in step S2, whenever the processing means 22 determines that a packet PKT_N (a packet showing the P picture shown in Figure 4) that does not constitute a burst has arrived in buffer 21, it sequentially executes steps S3, S4, step S5 ("NO") and step S7 to transmit the single packet PKT_N to base stations 1-5, and in step S8, it generates an encoded packet C. After that, the series of operations proceeds to step S2.

[0226] In step S8, if a packet PKT_N(1) that does not constitute a burst is encoded to generate an encoded packet, if in step S2 it is determined that no packet has arrived, and in step S9 it is determined that T milliseconds have elapsed since the last packet arrived at buffer 21, then the encoded packet (consisting of approximately N packets) will be sent K times (see steps S10 to S12).

[0227] Furthermore, when the terminal device 20 transmits each packet constituting a burst to base stations 1-5 individually, it sequentially executes steps 3, S4, step S5 ("NO") and step S7, just as when transmitting each packet that does not constitute a burst to base stations 1-5 individually, to transmit each packet constituting a burst to base stations 1-5 individually.

[0228] Next, we will explain the operation of the terminal device 20 when a packet constituting a burst (for example, any of packets P1 to P6 shown in Figure 9) arrives at buffer 21.

[0229] In step S2, the processing means 22 determines that packet P1 has arrived at buffer 21, and after sequentially executing steps S3 and S4 described above, in step S5 it determines not to transmit encoded packet C, and in step S7 it transmits packet P1 to base stations 1 to 5 via the transmitting means 23 and antenna 24.

[0230] Then, in step S8, the processing means 22 generates an encoded packet C1 containing packet P1, and the series of operations then proceeds to step S2.

[0231] Subsequently, in step S2, the processing means 22 determines that packet P2 has arrived at buffer 21, and after sequentially executing steps S3 and S4 described above, it determines in step S5 not to transmit encoded packet C, and in step S7 transmits packet P2 to base stations 1-5 via the transmitting means 23 and antenna 24. Then, in step S8, the processing means 22 generates encoded packet C2 containing packets P1 and P2. After that, the series of operations proceeds to step S2.

[0232] Subsequently, in step S2, the processing means 22 determines that packet P3 has arrived at buffer 21, and after sequentially executing steps S3 and S4 described above, in step S5 it determines to transmit encoded packet C (= encoded packet C1), and in step S6 it adds encoded packet C2 to packet P3 to generate combined packet P3 / C2. Then, in step S7, the processing means 22 transmits combined packet P3 / C2 to base stations 1-5 via the transmission means 23 and antenna 24. After that, in step S8, the processing means 22 generates encoded packet C3 containing packets P1-P3. Then, the series of operations proceeds to step S2.

[0233] After generating encoded packet C3, the processing means 22 determines in step S2 that packet P4 has arrived at buffer 21, and after sequentially executing steps S3 and S4 described above, it determines in step S5 not to transmit encoded packet C, and in step S7 transmits packet P4 to base stations 1-5 via the transmitting means 23 and antenna 24. Then, in step S8, the processing means 22 generates encoded packet C4 containing packets P1-P4. After that, the series of operations proceeds to step S2.

[0234] After generating the encoded packet C4, the processing means 22 determines in step S2 that packet P5 has arrived at buffer 21, and after sequentially executing steps S3 and S4 described above, determines in step S5 to transmit the encoded packet C, and in step S6, adds the encoded packet C4 to packet P5 to generate the combined packet P5 / C4. Then, in step S7, the processing means 22 transmits the combined packet P5 / C4 to base stations 1-5 via the transmitting means 23 and antenna 24.

[0235] Subsequently, in step S8, the processing means 22 generates an encoded packet C5 containing packets P1 to P5. Then, the series of operations proceeds to step S2.

[0236] After generating the encoded packet C5, the processing means 22 determines in step S2 that packet P6 has arrived at buffer 21, and after sequentially executing steps S3 and S4 described above, it determines in step S5 not to transmit the encoded packet C, and in step S7 transmits packet P6 to base stations 1-5 via the transmitting means 23 and antenna 24. Then, in step S8, the processing means 22 generates an encoded packet C6 containing packets P1-P6. After that, the series of operations proceed to step S2.

[0237] Subsequently, in step S2, the processing means 22 determines that no packets have arrived at buffer 21, in step S9, determines that T milliseconds have elapsed since the last packet (=packet P6) arrived at buffer 21, and in step S10, transmits the encoded packet C6 to base stations 1-5 via the transmitting means 23 and antenna 24. Then, in step S11, the processing means 22 determines that the number of encoded packets C transmitted is not K (=3), and in step S12, generates an encoded packet C7 containing packets P1-P6 from packets P1-P6 stored in buffer 21.

[0238] Subsequently, in step S10, the processing means 22 transmits the encoded packet C7 to base stations 1-5 via the transmitting means 23 and antenna 24.

[0239] Subsequently, in step S11, the processing means 22 determines that the number of encoded packets C transmitted is not K (=3), and in step S12, it generates an encoded packet C8 containing packets P1 to P6 from packets P1 to P6 stored in buffer 21.

[0240] Subsequently, in step S10, the processing means 22 transmits the encoded packet C8 to base stations 1-5 via the transmitting means 23 and antenna 24.

[0241] Then, in step S11, the processing means 22 determines that the number of encoded packets C transmitted is K (=3), and in step S13, it clears the buffer 21.

[0242] In the flowchart shown in Figure 13, the number of encoded packets transmitted in step S11 is the number of encoded packets transmitted in step S10, and does not include the number of encoded packets transmitted by the combined packet in step S7.

[0243] Furthermore, as explained in Figure 8(a), the number of packets M that make up a burst Burst The buffer size is M BufferIf, in step S2 of Figure 13, it is determined that no packets arrived, then packets P1 to P6 are stored in buffer 21, and the processing means 22 can generate encoded packets C7 and C8 containing all of packets P1 to P6 in step S12. As a result, even if a combined packet containing an encoded packet (at least one of encoded packets C1 to C5) or a single packet (packets P1, P2, P4, P6, etc. in Figure 9) is not received by base stations 1 to 5 in step S7, base stations 1 to 5 can decode the packets they were unable to receive (some of packets P1 to P6) by determining "K" in step S10 to send more encoded packets (encoded packets C7, C8, etc.) to base stations 1 to 5 than the number of packets that base stations 1 to 5 were unable to receive (some of packets P1 to P6).

[0244] Furthermore, as explained in Figure 8(b), the number of packets M that make up a burst Burst The buffer size is M Buffer If it is greater than, as shown in Figure 10, packets P2~P 10 When each of them arrives at terminal device 20, packets P2~P 10 Combined packets P2 / C1, P3 / C2, P4 / C3, P5 / C4, P6 / C5, P7 / C6, P8 / C7, P9 / C8, P 10 If / C9 is sent to base stations 1-5, the encoded packets C1-C9 are represented by the following equation.

[0245]

number

[0246] In equation (15), the number of packets contained in encoded packets C6 to C9 is 6 because the maximum number of packets M that can be stored in buffer 21 is equal to this number. BufferSince the value is "6", when packet P7 is copied to buffer 21, packets P1-P6 are overwritten by packets P2-P7, when packet P8 is copied to buffer 21, packets P2-P7 are overwritten by packets P3-P8, and when packet P9 is copied to buffer 21, packets P3-P8 are overwritten by packets P4-P9.

[0247] And, individual packets P1 and combined packets P2 / C1, P3 / C2, P4 / C3, P5 / C4, P6 / C5, P7 / C6, P8 / C7, P9 / C8, P 10 / C9 is sent in step S7 of Figure 13.

[0248] Individual packets P1 and combined packets P2 / C1, P3 / C2, P4 / C3, P5 / C4, P6 / C5, P7 / C6, P8 / C7, P9 / C8, P 10 If half of the 10 / C9 packets are not received by base stations 1-5, then the 9 combined packets P2 / C1, P3 / C2, P4 / C3, P5 / C4, P6 / C5, P7 / C6, P8 / C7, P9 / C8, P 10 Of the / C9 packets, at least four coupled packets can be received by base stations 1-5.

[0249] In this case, base stations 1-5 can receive packet P1 and four combined packets P2 / C1, P3 / C2, P4 / C3, P5 / C4, and five combined packets P6 / C5, P7 / C6, P8 / C7, P9 / C8, P 10 If / C9 could not be received, base stations 1-5 will send packets P6-P 10 It failed to receive the first packet, but packets P1 through P5 were received.

[0250] However, the terminal device 20 executes steps S10 to S12 in Figure 13 five times, thereby processing packets P5 to P 10 Five encoded packets C including 10 ~C 14 It can transmit to base stations 1-5. Five encoded packets C 10 ~C14 It can be expressed by the following equation:

[0251]

number

[0252] Then, the control device 6 processes five encoded packets C 10 ~C 14 Remove the information from the received packet P5 and encode packet C. 10 ',C 11 ',C 12 ',C 13 ',C 14 Generates '. Encoded packet C 10 ',C 11 ',C 12 ',C 13 ',C 14 Each of these consists of 5 packets P6~P 10 Since it includes, by solving the following system of equations, packets P6~P 10 It can be decrypted.

[0253]

number

[0254] Furthermore, base stations 1-5 send packet P1 and five combined packets P6 / C5, P7 / C6, P8 / C7, P9 / C8, P 10 If / C9 is received, but the four combined packets P2 / C1, P3 / C2, P4 / C3, and P5 / C4 are not received, then packets P2 through P5 were not received.

[0255] In this case, since the number of packets that could not be received is "4", the control device 6 selects four encoded packets C6 to C9 from encoded packets C5 to C9 in equation (15), removes the information of the received packets P1, P6 to P9 from encoded packets C6 to C9, and solves the system of equations that represent encoded packets C6' to C9' from which the information of the received packets P1, P6 to P9 has been removed, thereby decoding packets P2 to P5.

[0256] Thus, the number of packets M that make up a burst Burst The buffer size is M Buffer Even if the value is greater than that, the control device 6 can decode packets that base stations 1 to 5 could not receive.

[0257] Furthermore, in the flowchart shown in Figure 13 (including the flowchart shown in Figure 14), the terminal device 20 transmits a single packet or a combined packet (including an encoded packet) to base stations 1 to 5 each time a packet P1 to P6 constituting the burst arrives at the terminal device 20, so that multiple packets P1 to P6 constituting the burst can be transmitted to base stations 1 to 5 with low latency.

[0258] After the terminal device 20 transmits the packets constituting the burst (all packets P1 to P6 shown in Figure 9) to base stations 1 to 5, if it determines that packet PKT_N (the packet representing P-picture shown in Figure 4), which does not constitute a burst, has arrived at buffer 21, it transmits packet PKT_N (the packet representing P-picture shown in Figure 4), which does not constitute a burst, to base stations 1 to 5 using the method described above.

[0259] In this manner, the terminal device 20 transmits packets that do not constitute a burst and packets that constitute a burst to base stations 1 to 5 according to the flowchart shown in Figure 13 (including the flowchart shown in Figure 14).

[0260] Figure 15 is another flowchart illustrating the operation of the terminal device 20 shown in Figure 3.

[0261] The flowchart shown in Figure 15 is the same as the flowchart in Figure 13, except that steps S6 to S8 are changed to steps S14 and S15.

[0262] Referring to Figure 15, when the operation of the terminal device 20 begins, steps S1 to S5 described above are executed sequentially.

[0263] Then, in step S5, if it is determined that the encoded packet PKT_C should be sent, the processing means 22 retrieves the packet stored in the buffer 21, encodes the retrieved packet using the method described above, and generates the encoded packet PKT_C (step S14).

[0264] Then, in step S5, if it is determined that the encoded packet PKT_C will not be sent, or after step S14, the processing means 22 outputs the packet to the transmission means 23 and sends the packet to base stations 1 to 5.

[0265] Subsequently, the series of operations proceeds to step S2. In step S2, the processing means 22 repeatedly executes steps S1 to S5, S14, and S15 in sequence each time it determines that a packet has arrived.

[0266] Then, if it is determined in step S2 that no packet arrived, steps S9 to S13 described above are executed sequentially.

[0267] In the flowchart shown in Figure 15, the detailed operations of steps S12 and S14 are performed according to the flowchart shown in Figure 14.

[0268] In the flowchart shown in Figure 15, when a single packet PKT_N that does not constitute a burst arrives at terminal device 20, in step S2 it is determined that the packet has arrived, and then steps S3 and S4 are executed sequentially, in step S5 it is determined that no encoded packet should be sent, and in step S15 the single packet PKT_N that does not constitute a burst is sent to base stations 1 to 5.

[0269] On the other hand, as shown in Figure 12, when packet P1 constituting the burst arrives at terminal device 20, in step S2 it is determined that the packet has arrived, and then steps S3 and S4 are executed sequentially, in step S5 it is determined to send the encoded packet, and in step S14 the packet stored in buffer 21 is encoded by the method described above to generate encoded packet C1.

[0270] Then, in step S15, the encoded packet PKT_C1 is transmitted to base stations 1 to 5.

[0271] Furthermore, when packet P2, which constitutes the burst, arrives at terminal device 20, in step S2, it is determined that the packet has arrived. Subsequently, steps S3 and S4 are executed sequentially, and in step S5, it is determined that the encoded packet should be sent. In step S14, the packet stored in buffer 21 is encoded using the method described above to generate encoded packet C2.

[0272] Then, in step S15, the encoded packet PKT_C2 is transmitted to base stations 1 to 5.

[0273] Furthermore, when packet P3, which constitutes the burst, arrives at terminal device 20, in step S2 it is determined that the packet has arrived, and then steps S3 and S4 are executed sequentially, in step S5 it is determined to send the encoded packet, and in step S14 the packet stored in buffer 21 is encoded using the method described above to generate encoded packet C3.

[0274] Then, in step S15, the encoded packet PKT_C3 is transmitted to base stations 1-5.

[0275] Furthermore, in a similar manner, each time packets P4 to P6 constituting the burst arrive at terminal device 20, steps S2 ("YES"), S3, S4, S5 ("YES"), S14, and S15 are executed sequentially, and the encoded packets PKT_C4 to C6 are transmitted sequentially to base stations 1 to 5.

[0276] Then, in step S15, if it is determined in step S2 that the encoded packet PKT_C6 has been sent to base stations 1-5, then in steps S10-S12, the encoded packets PKT_C7-C9 shown in Figure 12 are sequentially sent to base stations 1-5.

[0277] Thus, in the flowchart shown in Figure 15 (including the flowchart shown in Figure 14), a single packet PKT_N that does not constitute a burst can be transmitted to base stations 1-5 independently, and a single packet PKT_N that constitutes a burst can be encoded and encoded packets C1-C9 can be transmitted to base stations 1-5 independently.

[0278] As described above, the terminal device 20 transmits packets that do not constitute a burst to base stations 1 to 5 individually, and transmits packets that constitute a burst to base stations 1 to 5 using either a single packet PKT_N, an encoded packet PKT_C, or a combined packet PKT_N / PKT_C.

[0279] The terminal device 20 can achieve the following effects by transmitting (broadcasting) packets to base stations 1-5.

[0280] [Improvement of error rate] By having multiple base stations 1-5 receive packets simultaneously, the packet error rate can be reduced.

[0281] Since a packet is considered successfully received if any one of the base stations 1 to 5 receives the packet, the total packet error rate PER_TOTAL is expressed by the following formula.

[0282]

number

[0283] Note that in equation (18), j is an argument that represents each base station, and PER j This represents the packet error rate of base station j.

[0284] From equation (18), the more base stations there are, the lower the total packet error rate per total can be.

[0285] [Resistant to noise and interference] Even if some base stations are affected by noise and interference, packets can be received by other, more distant base stations that are less affected, making the system more resilient to noise and interference.

[0286] [Low latency] This reduces the number of packet retransmissions or the coding rate, resulting in lower latency.

[0287] [No base station switching required] Since there is no base station switching, there is no momentary power outage caused by switching.

[0288] [Easy area expansion] By placing base stations along the work area, the work area can be seamlessly expanded. In other words, the work area can be expanded simply by increasing the number of base stations.

[0289] Figure 16 is a flowchart illustrating the operation of the communication system 10 shown in Figure 1.

[0290] Referring to Figure 16, when the operation of the communication system 10 begins, base stations 1 to 5 receive packets (either single packets, encoded packets, or combined packets) from the terminal device 20 and transmit the received packets (either single packets, encoded packets, or combined packets) to the control device 6 via wired communication (step S21).

[0291] When the receiving means 61 of the control device 6 receives a packet ("YES" in step S22), it outputs the received packet to the processing means 62.

[0292] The processing means 62 receives the packet PKT from the receiving means 61 and determines whether or not the received packet PKT is N packet PKT_N by determining whether or not N packet PKT_N has been received (step S23). In this case, the processing means 23 determines that N packet PKT_N has been received if the identifier N / C of the packet info of the packet PKT consists of "N" and the packet PKT does not contain Coded info and area REG2, and determines that N packet PKT_N has not been received if the identifier N / C of the packet info of the packet PKT consists of "C", or if the identifier N / C of the packet info of the packet PKT consists of "N" and the identifier N / C of the Coded info consists of "C".

[0293] In step S23, if it is determined that the N packet PKT_N was not received, the processing means 62 determines whether or not a combined packet (a packet sent by Piggyback) was received (step S24). In this case, the processing means 62 determines that a combined packet was received if the identifier N / C in the Packet info of the packet PKT consists of "N" and the identifier N / C in the Coded info of the packet PKT consists of "C", and determines that a combined packet was not received if the identifier N / C in the Packet info of the packet PKT consists of "C".

[0294] In step S24, when it is determined that a combined packet has been received, the processing means 62 separates the N packet and the C packet (=encoded packet) (step S25).

[0295] Subsequently, the processing means 62 determines whether or not there are N packets PKT_N (step S26).

[0296] In step S26, if it is determined that there are N packets PKT, or in step S23, if it is determined that N packets PKT_N have been received, the processing means 62 executes the N packet reception process (step S27).

[0297] Subsequently, the processing means 62 determines whether or not there is a C packet (=encoded packet) (step S28).

[0298] Then, in step S24, if it is determined that no combined packet was received, or in step S26, if it is determined that there is no N packet PKT_N, or in step S28, if it is determined that there is a C packet (=encoded packet), the processing means 62 removes the information of the received N packet PKT_N from the C packet (=encoded packet) (step S29).

[0299] Next, the processing means 62 performs the decryption process (step S30). Then, the processing means 62 determines whether or not the decryption was successful (step S31).

[0300] If it is determined in step S31 that decryption was successful, steps S30 and S31 are repeatedly executed until it is determined in step S31 that decryption was unsuccessful.

[0301] Then, if it is determined in step S28 that there are no C packets (=encoded packets), or if it is determined in step S31 that decoding was not possible, the series of operations proceeds to step S21. Thereafter, as long as base stations 1-5 and control device 6 are running, steps 21-S31 are repeatedly executed.

[0302] Furthermore, in step S24, when it is determined that no combined packet was received, the sequence of operations proceeds to step S29 because the packets received by the control device 6 are of three types: N packets PKT_N, encoded packets PKT_C, and combined packets. In step S23, it is determined that no N packets PKT_N were received, and in step S24, it is determined that no combined packets were received. Therefore, the packet received by the control device 6 is an encoded packet PKT_C.

[0303] Figure 17 is a flowchart illustrating the detailed operation of step S27 shown in Figure 16.

[0304] Referring to Figure 17, when it is determined in step S23 of Figure 16 that an N packet PKT_N has been received, or when it is determined in step S26 of Figure 16 that an N packet PKT_N exists, the processing means 62 processes the sequence number SN of the received N packet PKT_N. rx The sequence number SN of the N packet PKT_N that has been received and sent to the application. sent It is determined whether the sequence number is less than or equal to (i.e., the sequence number of the N packets stored in the N buffer 63), or whether the received N packet PKT_N has already been stored in the N buffer 63 (step S271).

[0305] In step S271, the sequence number SN of the received N packet PKT_N rx The sequence number SN of the N packet PKT_N that has been received and sent to the application. sent When it is determined that the following conditions apply, or when it is determined that the received N packet PKT_N has already been stored in the N buffer 63, the processing means 62 discards the received N packet PKT_N (step S272).

[0306] On the other hand, in step S271, the sequence number SN of the received N packet PKT_N rxThe sequence number SN of the N packet PKT_N that has been received and sent to application 30. sent If it is determined that the received N packet PKT_N is not below the specified value and has not been stored in the N buffer 63, the processing means 62 will process the received N packet PKT_N(SN rx ) is stored in N buffer 63 (step S273).

[0307] Then, the processing means 62 sets i=1 (step S274), and the sequence number SN sent It is determined whether a packet PKT_N with +i exists in buffer N 63 (step S275). Note that i is an integer of 1, 2, 3, ...

[0308] In step S275, sequence number SN sent When it is determined that a packet PKT_N with +i exists in buffer N 63, the processing means 62 determines the sequence number SN sent The packet PKT_N with +i is transmitted to the terminal device 30 via the network NW (step S276). Then, the processing means 62 sets i=i+1 (step S277). After that, the series of operations proceed to step S275, in step S275, the sequence number SN sent Steps S275 to S277 are repeatedly executed until it is determined that no packet PKT_N with +i exists in buffer N 63.

[0309] Then, in step S275, sequence number SN sent If it is determined that a packet PKT_N with +i does not exist in the N buffer 63, the processing means 62 will determine that SN sent =SN sent Set +i-1 (step S278).

[0310] Then, after step S272 or step S278, the series of operations proceeds to step S28 in Figure 16.

[0311] Steps S273 to S277 shown in Figure 17 are steps in which the newly received N packet PKT_N is stored in the N buffer 63 and transmitted to the terminal device 30. Then, when i≧2, in step S275, the sequence number SN sent If it is determined that no packet PKT_N with +i exists in N buffer 63, in step S278, the latest sequence number SN of the received N packet PKT_N in N buffer 63 is determined. sent It will be updated.

[0312] Furthermore, in step S271 shown in Figure 17, if it is determined that the received packet has already been stored in the N buffer 63, and the received packet is discarded in step S272, this corresponds to performing a duplicate check on the received packets and resolving the duplicates if they are found to be duplicates.

[0313] Furthermore, executing the steps shown in Figure 17, namely "NO" in step S271, then step S273, then step S274, then "NO" in step S275, and finally step S278, is equivalent to rearranging the N packets (single packets) in the order of their sequence numbers.

[0314] Figure 18 is a flowchart illustrating the detailed operation of step S29 shown in Figure 16.

[0315] Referring to Figure 18, when it is determined in step S24 of Figure 16 that no combined packet was received, or when it is determined in step S26 of Figure 16 that there are no N packets, or when it is determined in step S28 of Figure 16 that there are C packets (encoded packets), the processing means 62 sets i=1 (step S291) and takes packet X from the N buffer 63. i Obtain (step S292). Here, i is each packet X stored in buffer 63. i This represents a packet X stored in N buffer 63. i This is the total number.

[0316] After step S292, the processing means 62 processes packet X i It is determined whether the sequence number SN is included in the Coded info of the encoded packet Y (step S293).

[0317] In step S293, packet X i When it is determined that the sequence number SN is included in the Coded info of encoded packet Y, the processing means 62 processes encoded packet Y and packet X i By performing the exclusive OR operation with encoded packet Y, the received packet X is obtained. i Remove the information (step S294).

[0318] Then, in step S293, packet X i When it is determined that the sequence number SN is not included in the Coded info of the encoded packet Y, or after step S294, the processing means 62 determines whether i=I (step S295).

[0319] In step S295, if it is determined that i=I is not true, the processing means 62 sets i=i+1 (step S296). The series of operations then proceeds to step S292, and steps S292 to S296 are repeatedly executed until it is determined in step S295 that i=I.

[0320] Then, in step S295, if it is determined that i=I, the processing means 62 determines whether or not all of the information contained in the encoded packet Y has been received (step S297). In this case, the processing means 62 determines that all of the information contained in the encoded packet Y has been received when the encoded packet Y is Y={000···0}, and that not all of the information contained in the encoded packet Y has been received when the encoded packet Y is not Y={000···0} (i.e., only a portion of the information contained in the encoded packet Y has been received).

[0321] In step S297, if it is determined that not all of the information contained in encoded packet Y has been received, the processing means 62 determines whether the number of N packets contained in encoded packet Y is "1" (step S298).

[0322] In step S298, if it is determined that the number of N packets contained in the encoded packet Y is not "1", the processing means 62 stores the encoded packet Y in the C buffer 64 (step S299).

[0323] On the other hand, in step S298, when it is determined that the number of N packets contained in encoded packet Y is "1", the processing means 62 converts encoded packet Y into packet X using equation (13), and then executes the "N packet reception processing" (flowchart shown in Figure 17) described above on the converted packet X (step S300).

[0324] Then, in step S297, when it is determined that all the information contained in encoded packet Y has been received, or after step S299, or after step S300, the series of operations proceeds to step S30 in Figure 16.

[0325] In the flowchart shown in Figure 18, steps S292 to S296 are repeatedly executed until it is determined in step S295 that i=I, thereby processing all packets X1 to X received from encoded packet Y. I The information is removed. That is, steps S292 to S296 are repeatedly executed until it is determined in step S295 that i=I, thereby generating an encoded packet C that contains only one or more packets that are not stored in the N buffer 63 (i.e., multiple packets that have not yet been received).

[0326] Figure 19 is a flowchart illustrating the detailed operation of step S30 shown in Figure 16.

[0327] Referring to Figure 19, after step S29 in Figure 16, or when it is determined that decoding has been successful in step S31, the processing means 62 determines whether two or more encoded packets Y exist in the C buffer 64 (step S301).

[0328] If it is determined in step S301 that two or more encoded packets Y do not exist in the C buffer 64, the sequence of operations proceeds to step S21 in Figure 16.

[0329] On the other hand, if it is determined in step S301 that two or more encoded packets Y are present in the C buffer 64, the processing means 62 sets i=1 (step S302). Here, i is each encoded packet Y stored in the C buffer 64. i This represents the encoded packet Y stored in C buffer 64. i This is the total number.

[0330] After step S302, the processing means 62 encodes packet Y from the C buffer 64. i Obtain (step S303).

[0331] Then, the processing means 62 encodes packet Y i For "packet X received from encoded packet" i Remove the information (flowchart in Figure 18) (step S304).

[0332] Subsequently, the processing means 62 encodes packet Y i Determine whether the number of N packets included is "1" or less (step S305).

[0333] In step S305, encoded packet Y i If it is determined that the number of N packets contained in is "1" or less, the processing means 62 processes the encoded packet Y i Remove it from C buffer 64 (step S306).

[0334] Then, in step S305, the encoded packet Y i When it is determined that the number of N packets included is not less than or equal to "1", or after step S306, the processing means 62 determines whether i = I (step S307).

[0335] In step S307, if it is determined that i=I is not true, the processing means 62 sets i=i+1 (step S308). The series of operations then proceeds to step S303, and steps S303 to S308 are repeatedly executed until it is determined in step S307 that i=I.

[0336] Then, in step S307, if it is determined that i=I, the processing means 62 determines whether there are multiple encoded packets C containing multiple N packets in the C buffer 64 (step S309).

[0337] In step S309, when it is determined that there are multiple encoded packets C containing multiple N packets in the C buffer 64, the processing means 62 obtains multiple encoded packets Y from the C buffer 64 and decodes the C packets (encoded packets) by solving the system of equations representing the obtained multiple encoded packets Y (step S310).

[0338] Then, in step S309, if it is determined that there are no multiple encoded packets C containing multiple N packets in the C buffer 64, or after step S310, the processing means 62 sets i=1 (step S311) and determines whether the number of N packets that have been decoded is greater than or equal to "i" (step S312).

[0339] In step S312, if it is determined that the number of N packets that have been decoded is greater than or equal to "i", the processing means 62 performs the "N packet reception processing" (flowchart in Figure 17) on the decoded N packets (step S313). Then, the processing means 62 sets i = i + 1 (step S314). After that, the series of operations proceeds to step S312, and steps S312 to S314 are repeatedly executed until it is determined in step S312 that the number of N packets that have been decoded is not greater than or equal to "i".

[0340] Then, in step S312, if it is determined that the number of N packets that have been decrypted is not equal to or greater than "i", the sequence of operations proceeds to step S31 in Figure 16.

[0341] In the flowchart shown in Figure 19, if it is determined in step S297 of Figure 18 that all the information contained in encoded packet Y has been received, or if the process proceeds to step S301 after step S300, then in step S301 it is determined that there are no more than two encoded packets Y in buffer C 64, and the process proceeds to step S21 of Figure 16.

[0342] On the other hand, if the process proceeds to step S301 after step S299 in Figure 18, and it is determined in step S301 that two or more encoded packets Y exist in the C buffer 64, then steps S302 to S314 described above are executed sequentially. If it is determined in step S301 that two or more encoded packets Y do not exist in the C buffer 64, then the process proceeds to step S21 in Figure 16.

[0343] Furthermore, in the flowchart shown in Figure 19, steps S312 to S314 are repeatedly executed in step S312 until it is determined that the number of N packets that have been decoded is not greater than or equal to i. This is because the "N packet reception process" (flowchart in Figure 17) is executed for all N packets obtained by decoding the encoded packet C.

[0344] According to the operation of the communication system 10 described in Figures 16 to 19, multiple base stations 1 to 5 transmit packets received from the terminal device 20 to the control device 6. The control device 6 performs reception processing on the packets received from base stations 1 to 5 to generate received packets, and then transmits the generated received packets to the terminal device 30. In the reception processing, decoding of the encoded packet PKT_C, removal of duplicate packets, and sorting of packets in sequence number order are performed. Furthermore, the multiple base stations have communication ranges that cover mutually different communication spaces.

[0345] Therefore, it is possible to cover a wide area without requiring synchronization between multiple base stations 1 to 5.

[0346] Figure 20 shows the changes in N buffer 63 and C buffer 64 when receiving packets that make up a burst.

[0347] Figure 20 shows the changes in N buffer 63 and C buffer 64 when receiving packets constituting a burst, in the case where the packets constituting the burst consist of packets P1 to P6 shown in Figure 9.

[0348] Referring to Figure 20, when terminal device 20 transmits packet P1, control device 6 fails to receive packet P1. Therefore, in step S22 of Figure 16, the receiving means 61 of control device 6 does not receive packet P1. As a result, no packets are stored in N buffer 63 and C buffer 64 (see Figure 20(a)).

[0349] Subsequently, when the terminal device 20 transmits packet P2, the receiving means 61 of the control device 6 receives packet P2 (see “YES” in step S22 of Figure 16) and outputs the received packet P2 to the processing means 62.

[0350] When the processing means 62 receives packet P2 from the receiving means 61, it confirms that the identifier N / C in the Packet info of packet P2 is "N" and determines that it has received an N packet (see "YES" in step S23 of Figure 16). Then, the processing means 62 performs N packet reception processing on packet P2 (see step S27 of Figure 16) and the sequence number SN of packet P2 rx The sequence number SN of the N packet PKT_N that has been received and sent to the application. sent The processing means 62 determines that the sequence number of N packets stored in the N buffer 63 is greater than (that is, the sequence number of N packets stored in the N buffer 63) and that the received packet has not already been stored in the N buffer 63 (see "NO" in step S271 of Figure 17), and stores packet P2 in the N buffer 63 and transmits packet P2 to the terminal device 30 (see steps S273 to S276 of Figure 17). Then, when i=2, the processing means 62 determines that SN sent +i(=SN sent It is determined that the packet +2) does not exist in the N buffer 63 (see “NO” in step S275 of Figure 17), SN sent =SN sent +i-1=SN sent +2-1=SN sent The sequence number SN of the N packet PKT_N stored in N buffer 63 by +1 sent The data is updated (see step S278 in Figure 17). Subsequently, the processing means 62 determines that there is no C packet (see "NO" in step S28 in Figure 16), and the operation of the control device 6 proceeds to step S21 in Figure 16. At this stage, packet P2 is stored in the N buffer 63 (see (b) in Figure 20).

[0351] Subsequently, when terminal device 20 transmits the combined packet P3 / C2, control device 6 fails to receive the combined packet P3 / C2. Therefore, in step S22 of Figure 16, the receiving means 61 of control device 6 does not receive the combined packet P3 / C2. As a result, the states of N buffer 63 and C buffer 64 do not change (see Figure 20(c)).

[0352] Subsequently, when terminal device 20 transmits packet P4, control device 6 performs the same operation as described above when receiving packet P2. As a result, packet P4 is stored in N buffer 63 (see Figure 20(d)).

[0353] Then, when the terminal device 20 transmits the combined packet P5 / C4, the receiving means 61 of the control device 6 receives the combined packet P5 / C4 (see “YES” in step S22 of Figure 16), and outputs the received combined packet P5 / C4 to the processing means 62.

[0354] When the processing means 62 receives the combined packet P5 / C4 from the receiving means 61, it confirms that the identifier N / C in the Packet info of the combined packet P5 / C4 consists of "N" and the identifier N / C in the Coded info consists of "C", and determines that it did not receive the N packet PKT_N (see "NO" in step S23 of Figure 16), and determines that it did receive the combined packet (see "YES" in step S24 of Figure 16).

[0355] Subsequently, the processing means 62 separates the N packet P5 and the encoded packet C4 of the combined packet P5 / C4 (see step S25 in Figure 16), determines that there is an N packet (see "YES" in step S26 in Figure 16), and performs the N packet reception process on packet P5 (see step S27 in Figure 16). Then, in the N packet reception process, the processing means 62 determines the sequence number SN of packet P5. rx The sequence number SN of the N packet PKT_N that has been received and transmitted to terminal device 30. sent The processing means 62 determines that the received packet is greater than (i.e., the sequence number of N packets stored in the N buffer 63) and that the received packet is not stored in the N buffer 63 (see "NO" in step S271 of Figure 17), and stores packet P5 in the N buffer 63 and transmits packet P5 to the terminal device 30 (see steps S273 to S276 of Figure 17). Then, when i=2, the processing means 62 puts SN into the N buffer 63. sent +i(=SN sentIt was determined that the packet +2) does not exist (see “NO” in step S275 of Figure 17), SN sent =SN sent +i-1=SN sent +2-1=SN sent The sequence number SN of the N packet PKT_N stored in N buffer 63 by +1 sent The data is updated (see step S278 in Figure 17). Then, the processing means 62 determines that there is a C packet (see "YES" in step S28 in Figure 16) and removes the information of the received N packets from the C packet (see step S29 in Figure 16). At this point, packets P2, P4, and P5 are stored in the N buffer 63 (see (e) in Figure 20), and the encoded packet C4 contains packets P1 to P4, so the processing means 62 sequentially calculates the exclusive OR of the encoded packet C4 and packets P2 and P4 to remove the information of the received packets P2 and P4 from the encoded packet C4 (see steps S292 to S296 in Figure 18).

[0356] The encoded packet C4', after removing the information of the received packets P2 and P4 from the encoded packet C4, is represented by equation (9). As a result, the processing means 62 determines that not all of the information contained in encoded packet C4 has been received (see "NO" in step S297 of Figure 18), determines that the number of N packets contained in encoded packet C4' is not "1" (see "NO" in step S298 of Figure 18), and stores encoded packet C4' in the C buffer 64 (see step S299 of Figure 18). Consequently, three packets P2, P4, and P5 are stored in the N buffer 63, and one encoded packet C4' is stored in the C buffer 64 (see (e) in Figure 20).

[0357] After step S299 in Figure 18, the operation of the control device 6 proceeds to step S30 in Figure 16. In step S301 in Figure 19, which shows the detailed operation of step S30 in Figure 16, the processing means 62 determines that there are no more than two encoded packets Y in the C buffer 64, and the operation of the control device 6 proceeds to step S21 in Figure 16.

[0358] Subsequently, when terminal device 20 transmits packet P6, control device 6 performs the same operation as when packet P2 was received, as described above. As a result, packet P6 is stored in N buffer 63 (see (f) in Figure 20). After packet P6 is stored in N buffer 63, processing means 62 determines that there is no C packet (see "NO" in step S28 in Figure 16), and the operation of control device 6 proceeds to step S21 in Figure 16.

[0359] Subsequently, when the terminal device 20 transmits the encoded packet C6, the receiving means 61 of the control device 6 receives the encoded packet C6 (see “YES” in step S22 of Figure 16) and outputs the received encoded packet C6 to the processing means 62.

[0360] When the processing means 62 receives the encoded packet C6 from the receiving means 61, it determines that it did not receive N packets because the identifier N / C in the Packet info of the encoded packet C6 consists of "C" (see "NO" in step S23 of Figure 16), and determines that it did not receive the combined packet (see "NO" in step S24 of Figure 16).

[0361] Therefore, the processing means 62 removes information about already received packets from the encoded packet C6 (see step S29 in Figure 16). At this stage, the N buffer 63 contains packets P2, P4, P5, and P6, and the encoded packet C6 contains packets P1 to P6 (see equation (6)). Therefore, the processing means 62 sequentially calculates the exclusive OR of the encoded packet C6 and packets P2, P4, P5, and P6 to remove information about already received packets P2, P4, P5, and P6 from the encoded packet C6 (see steps S292 to S296 in Figure 18).

[0362] The encoded packet C6', after removing the information of the received packets P2, P4, P5, and P6 from the encoded packet C6, is represented by equation (10). As a result, the processing means 62 determines that not all of the information contained in encoded packet C6 has been received (see "NO" in step S297 of Figure 18), and determines that the number of N packets contained in encoded packet C6' is not "1" (see "NO" in step S298 of Figure 18), and stores encoded packet C6' in the C buffer 64 (see step S299 of Figure 18). Consequently, four packets P2, P4, P5, and P6 are stored in the N buffer 63, and two encoded packets C4' and C6' are stored in the C buffer 64 (see (g) in Figure 20).

[0363] Then, the processing means 62 determines that there are multiple encoded packets containing multiple N packets (see “YES” in step S309 of Figure 19), and solves the simultaneous equations of equation (9) representing encoded packet C4' and equation (10) representing encoded packet C6' to decode the C packets (see step S310 of Figure 19). This yields two N packets P1 and P3.

[0364] Subsequently, the processing means 62 sets i=1 (see step S311 in Figure 19), determines that the number of N packets that have been decoded is i (=1) or greater (see "YES" in step S312 in Figure 19), and executes the "N packet reception process" (flowchart shown in Figure 17) for the N packets P1 (see step S313 in Figure 19). Then, in the N packet reception process, the processing means 62 determines the sequence number SN of packet P1. rx The sequence number SN of the N packet PKT_N that has been received and sent to the application. sentThe processing means 62 determines that the sequence number of N packets stored in the N buffer 63 is greater than (that is, the sequence number of N packets stored in the N buffer 63) and that the received packet (=packet P1) has not yet been stored in the N buffer 63 (see "NO" in step S271 of Figure 17), and stores packet P1 in the N buffer 63 and transmits packet P1 to the terminal device 30 (see steps S273 to S276 of Figure 17). Then, when i=2, the processing means 62 puts an S&N into the N buffer 63. sent +i(=SN sent It was determined that the packet +2) does not exist (see “NO” in step S275 of Figure 17), SN sent =SN sent +i-1=SN sent +2-1=SN sent The sequence number SN of the N packet PKT_N stored in N buffer 63 by +1 sent Update (see step S278 in Figure 17).

[0365] In step S313 of Figure 19, if the "N packet reception process" (flowchart shown in Figure 17) is executed, after step S278 of Figure 17, the operation of the control device 6 proceeds to step S314 of Figure 19. The processing means 62 sets i=i+1=2 (see step S314 of Figure 19), determines that the number of N packets that have been decoded is i (=2) or greater (see "YES" in step S312 of Figure 19), and executes the "N packet reception process" (flowchart shown in Figure 17) for the N packet P2 (see step S313 of Figure 19). Then, in the N packet reception process, the processing means 62 determines the sequence number SN of packet P2. rx The sequence number SN of the N packet PKT_N that has been received and sent to application 30. sent The processing means 62 determines that the sequence number of N packets stored in the N buffer 63 is greater than (that is, the sequence number of N packets stored in the N buffer 63), and that the received packet (=packet P2) has not yet been stored in the N buffer 63 (see "NO" in step S271 of Figure 17), and stores packet P2 in the N buffer 63 and transmits packet P2 to the terminal device 30 (see steps S273 to S276 of Figure 17). Then, when i=2, the processing means 62 determines that SN sent+i(=SN sent It is determined that the packet +2) does not exist in the N buffer 63 (see “NO” in step S275 of Figure 17), SN sent =SN sent +i-1=SN sent +2-1=SN sent The sequence number SN of the N packet PKT_N stored in N buffer 63 by +1 sent The value is updated (see step S278 in Figure 17). Then, the processing means 62 sets i=i+1=3 (see step S314 in Figure 19) and determines that the number of N packets that have been decoded is not greater than or equal to i (=3) (see "NO" in step S312 in Figure 19). At this point, the operation of the control device 6 moves to step S31 in Figure 16, where the processing means 62 determines that decoding has been successful (see "YES" in step S31 in Figure 16). In step S301 of the flowchart in Figure 19, which shows the detailed operation of step S30 in Figure 16, it determines that there are no more than two coded packets in the C buffer 64 (see "NO" in step S301 in Figure 19), and the operation of the control device 6 moves to step S21 in Figure 16.

[0366] At this stage, no packets are stored in N buffer 63 and C buffer 64 (see Figure 20(h)). This completes the reception process for the packets that make up the burst (packets P1 to P6).

[0367] In the flowchart shown in Figure 16 (including the flowcharts shown in Figures 17 to 19) illustrating the packet reception process, in step S29 of Figure 16, after "removing information of the received N packets from the C packet" is performed, in step S304 of the flowchart in Figure 19, which shows the detailed operation of the decoding process in step S30, "removing information of the received packet X from the encoded packet" is performed. i The reason for performing the action of "removing the information" is as follows:

[0368] In the flowchart of Figure 13 showing the operation of the terminal device 20, in step S9, when it is determined that T milliseconds have elapsed since the last packet arrived at buffer 21, the terminal device 20 transmits encoded packets C to base stations 1-5 in step S11 until it is determined that the number of encoded packets transmitted is K (see steps S10-S12). In this case, as described above, the terminal device 20 transmits encoded packet C6 (=a 61 P1+a 62 P2+a 63 P3+a 64 P4+a 65 P5+a 66 P6) Encoded packet C7(=a 71 P1+a 72 P2+a 73 P3+a 74 P4+a 75 P5+a 76 P6) and coded packet C8 (=a 81 P1+a 82 P2+a 83 P3+a 84 P4+a 85 P5+a 86 P6) is transmitted to base stations 1-5. And here, the code a in coded packet C6 63 Assume that is zero. That is, the encoded packet C6 is essentially C6=a 61 P1+a 62 P2+a 64 P4+a 65 P5+a 66 It shall consist of P6.

[0369] As a result, even if base stations 1 to 5 cannot receive encoded packet C (for example, encoded packet C2) transmitted in step S7 of Figure 13, they can still receive encoded packets C6 to C8 transmitted in step S10.

[0370] Then, the processing means 62 of the control device 6 determines that it did not receive N packets (see "NO" in step S23 of Figure 16), and also determines that it did not receive a combined packet (see "NO" in step S24 of Figure 16), and removes the information of the received N packets P2, P4, P5, and P6 from the encoded packet C6 (see step S29 of Figure 16 (steps S291 to S296 of the flowchart in Figure 18)). As a result, the processing means 62 determines that encoded packet C6'=a 61 Get P1.

[0371] Then, the processing means 62 determines that not all of the information contained in encoded packet Y has been received (see “NO” in step S297 of Figure 18), determines that the number of N packets contained in encoded packet C6' is “1” (see “YES” in step S298 of Figure 18), and encode packet C6'=a 61 P1 is converted to P1 by equation (13) and the "N packet reception process" (flowchart shown in Figure 17) is executed (see step S300 in Figure 18).

[0372] In this case, the "N packet reception processing" is performed for the first time for packet P1, so the processing means 62 receives the sequence number SN of packet P1. rx The sequence number SN of the N packet PKT_N that has been received and sent to the application. sent If the sequence number is greater than (i.e., the sequence number of N packets stored in N buffer 63), and it is determined that the received packet (packet P1) has not yet been stored in N buffer 63 (see "NO" in step S271 of Figure 17), then packet P1 is stored in N buffer 63 (see step S273 of Figure 17). At this stage, packets P1, P2, P4, P5, and P6 are stored in N buffer 63.

[0373] Then, after step S300 in Figure 18, the processing means 62 repeatedly executes steps S303 to S308 multiple times in the flowchart of Figure 19 which shows the detailed operation of the decoding process (see step S30 in Figure 16), thereby in step S304, the encoded packet C4'(=a41 P1+a 43 Remove the information from packet P1 (P3) and encode packet C7 (=a 71 P1+a 72 P2+a 73 P3+a 74 P4+a 75 P5+a 76 Remove the information of packets P1, P2, P4, P5, and P6 from P6) and encode the packet C8 (=a 81 P1+a 82 P2+a 83 P3+a 84 P4+a 85 P5+a 86 Remove the information from packets P1, P2, P4, P5, and P6 from P6.

[0374] Thus, in order to remove the information of the newly acquired packet P1 (N packet) from the encoded packets C4', C7, and C8, in step S29 of Figure 16, the action of "removing the information of the received N packet from the C packet" is performed, and then in step S304 of the flowchart in Figure 19, which shows the detailed operation of the decoding process in step S30, the action of "removing the information of the received packet X from the encoded packet" is performed. i We decided to proceed with "removing the information."

[0375] In this embodiment of the invention, the operation of the terminal device 20 may be implemented by software. In this case, the terminal device 20 includes a CPU (Central Processing Unit), ROM (Read Only Memory), and RAM (Random Access Memory). The ROM stores either program Prog_A, which consists of each step of the flowchart shown in Figure 13 (including the flowchart shown in Figure 14), or program Prog_B, which consists of each step of the flowchart shown in Figure 15 (including the flowchart shown in Figure 14).

[0376] The CPU reads either program Prog_A or program Prog_B from ROM, executes the read program Prog_A or program Prog_B, and then sends packets to base stations 1-5. RAM performs the function of buffer 21 as described above.

[0377] Furthermore, program Prog_A or program Prog_B may be recorded on a recording medium such as a CD or DVD and distributed. When a recording medium containing program Prog_A or program Prog_B is inserted into a computer, the computer reads program Prog_A or program Prog_B from the recording medium, executes it, and performs the operation of sending packets to base stations 1 to 5.

[0378] Therefore, the recording medium on which program Prog_A or program Prog_B is recorded is a computer-readable recording medium.

[0379] Furthermore, in this embodiment of the invention, the operation of the communication system 10 may be implemented by software. In this case, the communication system 10 comprises base stations 1 to 5 and a personal computer. The personal computer comprises a CPU, ROM, and RAM. The ROM stores a program Prog_C consisting of each step of the flowchart shown in Figure 16 (including the flowcharts shown in Figures 17 to 19).

[0380] The CPU reads the program Prog_C from ROM, executes the read program Prog_C, and performs the packet reception process. RAM performs the functions of the N buffer 63 and C buffer 64 described above.

[0381] Furthermore, the program Prog_C may be recorded on a recording medium such as a CD or DVD and distributed. When a recording medium containing the program Prog_C is inserted into a computer, the computer reads the program Prog_C from the recording medium, executes it, and performs packet reception processing.

[0382] Therefore, the recording medium on which the program Prog_C is stored is a computer-readable recording medium.

[0383] Figure 21 is a schematic diagram of another communication system according to an embodiment of the present invention. The communication system according to an embodiment of the present invention may be the communication system 10A shown in Figure 21.

[0384] Referring to Figure 21, the communication system 10A comprises a control device 7 and base stations 11 to 15.

[0385] The control device 7 and base stations 11-15 are arranged in the wireless communication space. The control device 7 is connected to base stations 11-15 via a wired cable. The base stations 11-15 are also arranged at different locations in the communication space between them and the terminal device 50, which is the destination of packets, so as to cover different communication spaces.

[0386] The control device 7 receives individual packets PKT_N that constitute real-time traffic from terminal devices 40 via the network NW. The individual packets PKT_N that constitute real-time traffic consist of packets containing P-pictures and packets containing I-pictures as payloads, as shown in Figure 4. Furthermore, the individual packets PKT_N that constitute real-time traffic consist of broadcasts that transmit the same data simultaneously to multiple terminal devices 50, for example.

[0387] The control device 7 transmits, via wired communication, the single packets PKT_N that do not constitute a burst from the single packets PKT_N received from the terminal device 40 to multiple base stations 11 to 15.

[0388] Furthermore, the control device 7 generates encoded packets by encoding the individual packets PKT_N that constitute a burst from the individual packets PKT_N received from the terminal device 40 using the method described above. Then, the control device 7 allocates the encoded packets PKT_C to base stations 11-15 using the method described later, and transmits the allocated encoded packets PKT_C to base stations 11-15 via wired communication.

[0389] When base stations 11-15 receive a single packet PKT_N from the control device 7, they broadcast the received single packet PKT_N to multiple terminal devices 50. Also, when base stations 11-15 receive an encoded packet PKT_C from the control device 7, they broadcast the received encoded packet PKT_C to multiple terminal devices 50.

[0390] The same effects as those of the communication system 10 described above (improved error rate, low latency, no need to switch base stations, and easy area expansion) can be obtained in the communication system 10A as well.

[0391] Figure 22 is a schematic diagram of the control device 7 shown in Figure 21. Referring to Figure 22, the control device 7 comprises a receiving means 71, a processing means 72, a buffer 73, and a transmitting means 74.

[0392] The receiving means 71 receives a single packet PKT_N from the terminal device 40 via the network NW, and outputs the received single packet PKT_N to the processing means 72.

[0393] The processing means 72 determines the number of packets (either single packets PKT_N, combined packets PKT_N / PKT_C, or encoded packets PKT_C) to be allocated to each base station 11-15, N_ALC, by a method described later, and outputs the determined number N_ALC to the transmission means 74.

[0394] Furthermore, the processing means 72 receives a single packet PKT_N from the receiving means 71. When the received single packet PKT_N is a packet that does not constitute a burst, the processing means 72 copies the single packet PKT_N to the buffer 73 and outputs the original single packet PKT_N to the transmitting means 74.

[0395] On the other hand, if the single packet PKT_N received by the receiving means 71 is a packet that constitutes a burst, the processing means 72 copies the single packet PKT_N to the buffer 73. Then, the processing means 72 reads the single packet PKT_N stored in the buffer 73 and encodes the read single packet PKT_N using the method described above to generate an encoded packet PKT_C. After that, the processing means 72 transmits the encoded packet PKT_C using one of the following two methods.

[0396] [Method for sending encoded packets] (I) The processing means 72 adds the encoded packet PKT_C, which was generated before the single packet PKT_N received from the receiving means 71 was copied to the buffer 73, to the single packet PKT_N received from the receiving means 71 to generate a combined packet PKT_N / PKT_C, and outputs the generated combined packet PKT_N / PKT_C to the transmitting means 74. (II) The processing means 72 copies the single packet PKT_N received from the receiving means 71 to the buffer 73 and then outputs the encoded packet PKT_C generated thereafter to the transmitting means 74.

[0397] The transmission means 74 receives from the processing means 72 the number of packets (N_ALC) to be allocated to each base station 11-15 (either a single packet PKT_N, a combined packet PKT_N / PKT_C, or an encoded packet PKT_C).

[0398] Then, when the transmitting means 74 receives a packet PKT (either a single packet PKT_N, a combined packet PKT_N / PKT_C, or an encoded packet PKT_C) from the processing means 72, it transmits the packet PKT (either a single packet PKT_N, a combined packet PKT_N / PKT_C, or an encoded packet PKT_C) received from the processing means 72 to the base stations 11-15 via wired communication, according to the number of packets PKT to be allocated to each base station 11-15, N_ALC.

[0399] [Packet allocation method] The processing means 72 determines the number of packets (N_ALC) to be allocated to each base station 11-15 (either single packets PKT_N, combined packets PKT_N / PKT_C, or encoded packets PKT_C) by one of the following allocation methods (A) to (C). (A) The number of packets (N_ALC) allocated to each base station 11-15 (either single packets PKT_N, combined packets PKT_N / PKT_C, or encoded packets PKT_C) is made equal. (B) The number of packets (N_ALC) to be allocated to each base station 11-15 (either single packets PKT_N, combined packets PKT_N / PKT_C, or encoded packets PKT_C) is dynamically determined. (C) The number of packets (N_ALC) to be allocated to each base station 11-15 (either single packets PKT_N, combined packets PKT_N / PKT_C, or encoded packets PKT_C) is determined according to the density of surrounding base stations for each base station 11-15.

[0400] [Packet allocation method (A)] Figure 23 is a schematic diagram of the correspondence table TBL1. Referring to Figure 23, the correspondence table TBL1 includes base stations and the number of packets to be allocated. The base stations and the number of packets to be allocated are correlated with each other. The number of packets to be allocated corresponding to base stations 11 to 15 consists of the same number N_ALC.

[0401] When the processing means 72 determines the number N_ALC according to the packet allocation method (A), it creates a correspondence table TBL1 and outputs the created correspondence table TBL1 to the transmission means 74.

[0402] [Packet allocation method (B)] When the processing means 72 determines the number N_ALC by the packet allocation method (B), the packet error rate PER between all terminal devices 50 and all base stations 11-15 j,s Manages the packet error rate (PER). j,s In this configuration, "j" is an argument representing each of the base stations 11-15, and "s" is an argument representing the terminal device 50.

[0403] The receiving means 71 of the control device 7 is a base station AP j (Through one of base stations 11-15) j Number of packets sent by PKT: N_TR j The number of received packets PKT (N_RCV) measured in each terminal device 50 for the most recent period ("most recent" refers to a period of time from 1 to 30 seconds prior to the current time, typically 10 seconds prior) is also measured. s Received and sent N_TR j and the number of received RCVs s The output is sent to the processing unit 72.

[0404] The processing means 72 receives the number of transmissions N_TR from the receiving means 71. j and the number of received RCVs s The processing means 72 receives the number of received RCVs. s Number of transmissions N_TR j By dividing by the packet error rate PER j,s Calculate.

[0405] Then, the processing means 72 allocates the number of packets PKT to each base station 11-15 according to the following formula T j Determine the combination of CBNs.

[0406]

number

[0407] In equation (19), equation (19B) is "the sum of expected receptions in multiple terminal devices 50 E_Total s The condition is that "it must be greater than or equal to the threshold E_Total_Thre". And the threshold E_Total_Thre is, for example, R1·N k And R1 is a real number greater than or equal to 1.0 (for example, 1, 5), and N k This is the number of standalone packets PKT_N contained in the encoded packet PKT_C. Also, in equation (19A), "AP" represents the set of base stations 11 to 15.

[0408] Equation (19) gives the number of packets PKT T j Determining a combination of CBNs is equivalent to distributing packets among multiple base stations 11-15 such that the sum of the number of packets transmitted by all of the multiple base stations 11-15 is minimized.

[0409] Figure 24 is a schematic diagram of the correspondence table TBL2. Referring to Figure 24, the correspondence table TBL2 includes base stations and the number of packets to be allocated. Base stations and the number of packets to be allocated are correlated with each other. Number of packets to be allocated N_ALC 11 ~N_ALC 15 These correspond to base stations 11-15, respectively. And N_ALC 11 ~N_ALC 15 This is the CBN(T) calculated by equation (19). j It consists of a combination of the above.

[0410] The processing means 72 determines the number of packets PKT to be allocated to each base station 11-15 according to equation (19), T. j Once the combination CBN is determined, a correspondence table TBL2 is created and output to the transmission means 74.

[0411] In the packet allocation method (B), the processing means 72 may calculate the packet error rate PER based on the received signal strength RSSI of the signals from each of the base stations 11 to 15 in the terminal device 50. j,s In this case, the processing means 72 calculates the packet error rate PER j,s by the following method.

[0412] The processing means 72 holds threshold values RSSI_THRE_1 and RSSI_THRE_2. The threshold value RSSI_THRE_1 is, for example, -80 dBm, and the threshold value RSSI_THRE_2 is, for example, -60 dBm. The threshold values RSSI_THRE_1 and RSSI_THRE_2 are not limited to these values, as long as the threshold value RSSI_THRE_1 is smaller than the threshold value RSSI_THRE_2 (that is, the relationship RSSI_THRE_1 < RSSI_THRE_2 is satisfied).

[0413] The processing means 72 calculates the packet error rate PER j,s by the formula (20) based on the received signal strength RSSI j,s from the base station j in the terminal device s.

[0414] More specifically, when the received signal strength RSSI j,s is smaller than the threshold value RSSI_THRE_1, the processing means 72 calculates the packet error rate PER j,s by the formula (20A). When the received signal strength RSSI j,s is greater than or equal to the threshold value RSSI_THRE_1 and smaller than the threshold value RSSI_THRE_2, the processing means 72 calculates the packet error rate PERj,s by the formula (20B). When the received signal strength RSSI j,s is greater than or equal to the threshold value RSSI_THRE_2, the processing means 72 calculates the packet error rate PER j,s by the formula (20C).

[0415]

Equation

[0416] [Packet allocation method (C)] Each of the base stations 11 to 15 monitors signals from base stations located in its vicinity and measures the received signal strength RSSI when it receives a signal from a base station located in its vicinity. Then, each of the base stations 11 to 15 transmits the measured received signal strength RSSI to the control device 7.

[0417] The receiving means 71 of the control device 7 receives the received signal strength RSSI from each of the base stations 11 to 15 and outputs the received received signal strength RSSI to the processing means 72.

[0418] When the processing means 72 of the control device 7 receives the received signal strength RSSI of each base station 11 to 15 from the receiving means 71, it calculates the number of surrounding base stations X whose received signal strength is -60 dBm or higher based on the received signal strength RSSI. j And the number of surrounding base stations Y whose received signal strength is between -80 dBm and -60 dBm. j It detects this.

[0419] Then, the processing means 72 determines the number of packets T to be allocated to each base station 11-15 according to the following equation. j Calculate.

[0420]

number

[0421] Equation (21C) is "the number of packets T to be allocated to each base station 11-15". j The condition is that "it must be greater than or equal to the minimum value T_Min," and T_Min is an integer greater than or equal to 1. Also, in equation (21A), a and b are real numbers between 0 and 1, and a > b. Furthermore, R2 in equation (21B) is, for example, 1.2.

[0422] The number of base stations surrounding one base station is N. AP Assume that when one base station receives signals from surrounding base stations, all of the received signal strength RSSIs are -60 dBm or higher, Y jSince = 0, the denominator of equation (21A) is aX j This is the result.

[0423] Furthermore, when one base station receives signals from surrounding base stations, and all of the received signal strength RSSIs are between -80 dBm and -60 dBm, X j Since = 0, the denominator of equation (21A) is bY j This is the result.

[0424] Furthermore, when one base station receives signals from some of the surrounding base stations, the received signal strength RSSI is -60 dBm or higher, and when one base station receives signals from the remaining surrounding base stations, the received signal strength RSSI is between -80 dBm and -60 dBm, then the denominator of equation (21A) is aX j +bY j This is the result.

[0425] The denominator of equation (21A) is aX j In the case where the denominator of equation (21A) is bY j When compared to the case where a > b and X j =Y j =N AP Therefore, aX j >by j Therefore, T j The case where all received signal strength RSSIs when a single base station receives signals from surrounding base stations are -60 dBm or higher is less than the case where all received signal strength RSSIs when a single base station receives signals from surrounding base stations are between -80 dBm and -60 dBm.

[0426] The denominator of equation (21A) is aX j In the case where the denominator of equation (21A) is aX j +bY j Compare this with the case where the denominator of equation (21A) is aX j In that case, the denominator of equation (21A) is aX j =aN AP This is the result.

[0427] On the other hand, the denominator of equation (21A) is aX j+bY j If X j +Y j =N AP Since this holds true, the denominator of equation (21A) is aX j +bY j =aN AP +(ba)Y j Therefore, since a > b, (ba)Y j This will result in a negative value, aX j +bY j is aN AP It will become smaller than that.

[0428] Next, the denominator of equation (21A) is bY j In the case where the denominator of equation (21A) is aX j +bY j Compare this with the case where the denominator of equation (21A) is bY j In that case, the denominator of equation (21A) is bY j =bN AP This is the result.

[0429] On the other hand, the denominator of equation (21A) is aX j +bY j If X j +Y j =N AP Since this holds true, the denominator of equation (21A) is aX j +bY j =bN AP +(ab)X j Therefore, since a > b, (ab)X j aX will be a positive value. j +bY j is, bN AP It will become larger than that.

[0430] Therefore, the denominator of equation (21A) is largest when all of the received signal strength RSSIs when one base station receives signals from surrounding base stations are -60 dBm or higher, second largest when the received signal strength RSSI when one base station receives signals from some of the surrounding base stations is -60 dBm or higher, and the received signal strength RSSI when one base station receives signals from the remaining surrounding base stations is between -80 dBm and -60 dBm, and smallest when all of the received signal strength RSSIs when one base station receives signals from surrounding base stations are between -80 dBm and -60 dBm.

[0431] To summarize, the results are shown in Table 1.

[0432] [Table 1]

[0433] In Table 1, the density of surrounding base stations is the number of base stations where the received signal strength RSSI at a single base station is -80 dBm or higher. The density of surrounding base stations is highest when all received signal strength RSSIs are -60 dBm or higher, and lowest when all received signal strength RSSIs are between -80 and -60 dBm, because a higher received signal strength RSSI means that more surrounding base stations are located near a single base station, and a lower received signal strength RSSI means that fewer surrounding base stations are located near a single base station.

[0434] As shown in Table 1, the density of surrounding base stations is highest when all received signal strength RSSIs when one base station receives signals from surrounding base stations are -60 dBm or higher, second highest when one base station receives signals from some surrounding base stations and the received signal strength RSSI is -60 dBm or higher, AND when one base station receives signals from the remaining surrounding base stations and the received signal strength RSSI is between -80 dBm and -60 dBm, and lowest when all received signal strength RSSIs when one base station receives signals from surrounding base stations are between -80 dBm and -60 dBm.

[0435] And the number of packets to send to a single base station is T. j The lowest value occurs when all received signal strength RSSI values ​​from a single base station receiving signals from surrounding base stations are -60 dBm or higher; the second lowest value occurs when the received signal strength RSSI values ​​from some surrounding base stations receiving signals are -60 dBm or higher, and the received signal strength RSSI values ​​from the remaining surrounding base stations are between -80 dBm and -60 dBm; and the highest value occurs when all received signal strength RSSI values ​​from a single base station receiving signals from surrounding base stations are between -80 dBm and -60 dBm.

[0436] Therefore, when the density of surrounding base stations is the first density, the number of packets transmitted in processing 72 is T. j Determine the first value, and when the density of surrounding base stations is a second density which is lower than the first density, the number of packets transmitted T j Determine that the second value is greater than the first value.

[0437] Figure 25 is a schematic diagram of correspondence table TBL3. Referring to Figure 25, correspondence table TBL3 has the same structure as correspondence table TBL2. And in correspondence table TBL3, N_ALC 11 ~N_ALC 15 Each of these is T calculated by equation (21) j It consists of.

[0438] The processing means 72 determines the number of packets PKT to be allocated to each base station 11-15 according to equation (21), T. j Once determined, a correspondence table TBL3 is created and output to the transmission means 74.

[0439] Figure 26 is a flowchart illustrating the operation of the communication system 10A shown in Figure 21.

[0440] Referring to Figure 26, when the operation of the communication system 10A begins, the control device 7 determines the number of packets to allocate to each base station 11 to 15 (step S101). In this case, the control device 7 determines the number of packets to allocate to each base station 11 to 15 using one of the packet allocation methods (A) to (C) described above.

[0441] Then, after step S101, the control device 7 receives packets from the terminal device 40 via the network NW (step S102). Subsequently, the control device 7 transmits packets to multiple base stations 11-15 via wired communication according to the number of packets determined in step S101 (step S103).

[0442] Multiple base stations 11-15 receive packets from the control device 7 (step S104) and broadcast the received packets to the terminal device 50 (step S105).

[0443] Then, the control device 7 determines whether or not to newly determine the number of packets to allocate to each base station 11 to 15 (step S106). In this case, when the control device 7 determines the number of packets to allocate to each base station 11 to 15 by either of the packet allocation methods (A) or (C) described above, it determines not to newly determine the number of packets to allocate to each base station 11 to 15, and when the control device 7 determines the number of packets to allocate to each base station 11 to 15 by the packet allocation method (B) described above, it determines to newly determine the number of packets to allocate to each base station 11 to 15.

[0444] If, in step S106, it is determined that no new number of packets to be allocated to each base station 11-15 needs to be determined, the series of operations proceeds to step S102, after which steps S102 to S106 are executed sequentially.

[0445] On the other hand, if it is determined in step S106 to newly determine the number of packets to be allocated to each base station 11-15, the series of operations proceeds to step S101, and then steps S101 to S106 are executed sequentially.

[0446] Furthermore, as long as the communication system 10A is running, steps S101 to S106 will be repeatedly executed.

[0447] Figure 27 is a flowchart illustrating the detailed operation of step S101 shown in Figure 26. Note that the flowchart in Figure 27 is a flowchart illustrating the detailed operation of step S101 when using the packet allocation method (B) described above.

[0448] Referring to Figure 27, when it is determined that the number of packets to be allocated to each base station is to be newly determined after the “start” in Figure 26, or in step S106, the processing means 72 of the control device 7 determines the number of packets received from all base stations AP_1 to AP_J in all terminal devices STA_1 to STA_S, N_RCV 1,1 ~N_RCV 1,J ;N_RCV 2,1 ~N_RCV 2,J ;···;N_RCV S,1 ~N_RCV S,J And the total number of packets transmitted by all base stations AP_1~AP_J T 1,1 ~T S,1 ;T 1,2 ~T S,2 ;···;T 1,J ~T S,J The following is received (step S101-1). Here, S is the total number of terminal devices 50, and J is the total number of base stations 11-15.

[0449] Then, the processing means 72 processes the number of encoded packets transmitted by all base stations AP_1 to AP_J T1 to T J Set to the same value T_Min (step S101-2).

[0450] Subsequently, the processing means 72 sets s=1 (step S101-3) and sets j=1 (step S101-4).

[0451] Subsequently, the processing means 72 determines the number of packets received by the terminal device STA_s from the base station AP_j, N_RCV s,j The number of packets T sent from base station AP_j to terminal device STA_s j,s Divide by the packet error rate PER j,s Calculate (Step S101-5).

[0452] Then, the processing means 72 determines the expected number of received packets E that the terminal device STA_s receives from the base station AP_j. j,s (=T j,s ·PER j,s Calculate (Step S101-6).

[0453] Subsequently, the processing means 72 calculates E_Total_j_s=E_Total_j_s+E j,s The expected number of packets received from base station AP_j, E_Total_j_s, in the terminal device STA_s is updated (step S101-7).

[0454] Then, the processing means 72 determines whether j=J or not (step S101-8). If it is determined in step S101-8 that j=J is not true, the processing means 72 sets j=j+1 (step S101-9). After that, the series of operations proceeds to step S101-5, and steps S101-5 to S101-9 are repeatedly executed until it is determined in step S101-8 that j=J.

[0455] Then, in step S101-8, if it is determined that j=J, the processing means 72 obtains the total number of expected packets E_Total_s from all base stations AP_1 to AP_J in the terminal device STA_s (step S101-10).

[0456] Subsequently, the processing means 72 determines whether s = S or not (step S101-11).

[0457] In step S101-11, if it is determined that s=S, the processing means 72 sets s=s+1 (step S101-12). Subsequently, the series of operations proceeds to step S101-4, and steps S101-4 to S101-12 are repeatedly executed until it is determined in step S101-11 that s=S.

[0458] Then, in step S101-11, if it is determined that s=S, the processing means 72 detects the minimum value E_Total_min among the sum of the expected number of packets received from all base stations AP_1-AP_J at all terminal devices STA_1-STA_S, E_Total_1-E_Total_S (step S101-13).

[0459] Then, the processing means 72 determines whether the minimum value E_Total_min is greater than or equal to the threshold E_Total_Thre (step S101-14).

[0460] In step S101-14, if it is determined that the minimum value E_Total_min is not greater than or equal to the threshold E_Total_Thre, the sequence of operations proceeds to step S101-1, and steps S101-1 to S101-14 are repeatedly executed until it is determined that the minimum value E_Total_min is greater than or equal to the threshold E_Total_Thre.

[0461] Then, in step S101-14, if it is determined that the minimum value E_Total_min is greater than or equal to the threshold E_Total_Thre, the processing means 72 calculates the packet error rate PER for the terminal device STA_p when the minimum value E_Total_min is obtained. j,p Select the base station AP_q with the smallest size, and the number of encoded packets transmitted by base station AP_q is T. q Increase it by "1" (T q =Tq +1) (Step S101-15). The series of operations then proceeds to step S102 in Figure 26.

[0462] Note that when step S101-7 is executed for the first time, E_Total_j_s = E_Total_j_s + E j,s T_Min is substituted for “E_Total_j_s” on the right-hand side of the equation.

[0463] Furthermore, by executing steps S101-5 to S101-9 for all base stations AP_1 to AP_J, the total expected number of encoded packets that one terminal device STA_s will receive from all base stations AP_1 to AP_J, E_Total_s, is obtained (see step S101-10).

[0464] Furthermore, steps S101-4 to S101-12 are executed for all terminal devices STA_1 to STA_S to obtain the total sum E_Total_1 to E_Total_S for all terminal devices STA_1 to STA_S (see step S101-13).

[0465] Furthermore, in step S101-13, if there are multiple minimum values ​​among the sums of expected packet receptions E_Total_1~E_Total_S from all base stations AP_1~AP_J to all terminal devices STA_1~STA_S, any of the minimum values ​​among these multiple minimum values ​​is detected as the minimum value E_Total_min.

[0466] Furthermore, in step S101-5, the received signal strength RSSI received by the terminal device STA_s from the base station AP_j j,s Based on this, the packet error rate PER is calculated by equation (20). j,s You may calculate this.

[0467] Figure 28 is another flowchart illustrating the detailed operation of step S101 shown in Figure 26. Note that the flowchart in Figure 28 is a flowchart illustrating the detailed operation of step S101 when using the packet allocation method (C) described above.

[0468] Referring to Figure 28, after the “start” in Figure 26, the processing means 72 of the control device 7 receives the received signal strengths RSSI_1 to RSSI_J (each of RSSI_1 to RSSI_J consists of the received signal strength when each base station receives a signal from a surrounding base station) from all base stations AP_1 to AP_J (step S101-21).

[0469] Then, the processing means 72 sets j=1 (step S101-22) and receives the signal strength RSSI_1_j ~ RSSI_N AP _j(N AP X is the number of base stations with a received signal strength of -60 dBm or higher among the total number of base stations surrounding base station AP_j. j And the number of received signal strengths Y in the range of -80 to -60 dBm. j Count the (step S101-23).

[0470] Subsequently, the processing means 72 processes the number X j ,Y j Based on this, equation (21) determines the number of packets T to be allocated to base station AP_j. j Calculate (Step S101-24).

[0471] Then, the processing means 72 determines whether j=J or not (step S101-25).

[0472] In step S101-25, if it is determined that j=J, the processing means 72 sets j=j+1 (step S101-26). Subsequently, the series of operations proceeds to step S101-23, and steps S101-23 to S101-26 are repeatedly executed until it is determined in step S101-25 that j=J.

[0473] Then, in step S101-25, if it is determined that j=J, the processing means 72 determines the number of packets T1 to T to be allocated to base stations AP_1 to AP_J respectively. J The data is obtained (steps S101-27). The sequence of operations then proceeds to step S102 in Figure 26.

[0474] Figure 29 is a flowchart illustrating the detailed operation of step S103 shown in Figure 26.

[0475] Referring to Figure 29, after step S102 in Figure 26, the processing means 72 of the control device 7 determines whether or not to transmit the encoded packet using piggyback (step S103-1).

[0476] In step S103-1, when it is determined that the encoded packet should be sent via Piggyback, the processing means 72 performs the following steps according to the flowchart shown in Figure 13 (including the flowchart shown in Figure 14): Number T1 to T J The packets are sent to base stations AP_1 to AP_J accordingly (step S103-2).

[0477] On the other hand, if it is determined in step S103-1 that the encoded packet will not be sent via Piggyback, the processing means 72 will, according to the flowchart shown in Figure 15 (including the flowchart shown in Figure 14), determine the number of T1 to T J The packets are sent to base stations AP_1 to AP_J accordingly (step S103-3).

[0478] Then, after step S103-2 or step S103-3, the series of operations proceeds to step S104 in Figure 26.

[0479] In the flowchart shown in Figure 29, when sending packets to base stations AP_1 to AP_J in step S103-2, in step S7 of Figure 13, the number of single packets or combined packets PKT_N / PKT_C is T1 to T JThese packets are transmitted to base stations AP_1 to AP_J accordingly, and in step S10 of Figure 13, the encoded packets PKT_C are numbered T1 to T J The data is transmitted to base stations AP_1 through AP_J accordingly.

[0480] Furthermore, in the flowchart shown in Figure 29, when sending packets to base stations AP_1 to AP_J in step S103-3, in step S15 of Figure 15, if the number of single packets or encoded packets PKT_C is T1 to T J The packets are transmitted to base stations AP_1 to AP_J accordingly, and in step S10 of Figure 15, the number of encoded packets PKT_C is T1 to T J The data is transmitted to base stations AP_1 through AP_J accordingly.

[0481] Each of the multiple terminal devices 50 receives packets broadcast by base stations AP_1 to AP_J, performs reception processing of the received packets (N-packet reception processing, separation processing, removal processing, and decoding processing) according to the flowchart shown in Figure 16 (including the flowcharts shown in Figures 17 to 19), and transmits the processed packets to an application (not shown).

[0482] In the communication system 10A, the control device 7 transmits single packets PKT_N that do not constitute a burst from the single packets PKT_N received from the terminal device 40 to base stations AP_1 to AP_J, encodes the single packets PKT_N that constitute a burst to generate encoded packets PKT_C, transmits the generated encoded packets PKT_C to base stations AP_1 to AP_J either via piggyback or individually, and base stations AP_1 to AP_J broadcast the single packets PKT_N or encoded packets PKT_C received from the control device 7 to multiple terminal devices 50.

[0483] As a result, base stations AP_1 to AP_J broadcast single packets PKT_N or encoded packets PKT_C to multiple terminal devices 50 without synchronizing with each other.

[0484] Therefore, wide-area coverage is possible without synchronization between base stations AP_1 to AP_J.

[0485] In this embodiment of the invention, the operation of the communication system 10A may be implemented by software. In this case, the communication system 10A comprises base stations 11 to 15 and a personal computer. The personal computer comprises a CPU, ROM, and RAM. The ROM stores either program Prog_A or program Prog_B.

[0486] The CPU reads either program Prog_A or program Prog_B from ROM, executes the read program Prog_A or program Prog_B, and then performs the packet transmission process. RAM performs the function of buffer 73 as described above.

[0487] Furthermore, program Prog_A or program Prog_B may be recorded on a recording medium such as a CD or DVD and distributed. When a recording medium containing program Prog_A or program Prog_B is inserted into a computer, the computer reads program Prog_A or program Prog_B from the recording medium, executes it, and performs the packet transmission process.

[0488] Therefore, the recording medium on which program Prog_A or program Prog_B is recorded is a computer-readable recording medium.

[0489] In this embodiment of the invention, N packets constitute a "single packet," each of encoded packets C2 and C4 constitutes a "first encoded packet," each of encoded packets C6 to C8 constitutes a "second encoded packet," and encoded packets such as C4', C6', etc., after removing information of received packets from encoded packets C4 and C6, constitute a "third encoded packet."

[0490] Furthermore, in this embodiment of the invention, each of P2 / C1, P3 / C2, P4 / C3, P5 / C4, and P6 / C5 constitutes a "combined packet".

[0491] Furthermore, in the embodiment of this invention, the process of transmitting N packets constitutes the "first transmission process," the process of transmitting each of P2 / C1, P3 / C2, P4 / C3, P5 / C4, and P6 / C5 constitutes the "second transmission process," and the process of transmitting each of the encoded packets C6 to C8 individually constitutes the "third transmission process."

[0492] Furthermore, in this embodiment of the invention, T milliseconds constitute a "threshold."

[0493] Furthermore, in this embodiment of the invention, the N buffer 63 constitutes a "first receive buffer," and the C buffer 64 constitutes a "second receive buffer."

[0494] Furthermore, in this embodiment of the invention, the processing means 23 that separates P3 / C2 into packet P3 and encoded packet C2, separates P5 / C4 into packet P5 and encoded packet C4, and separates P6 / C5 into packet P6 and encoded packet C5 constitutes the "separation means".

[0495] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than by the description of the embodiments above, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Industrial applicability]

[0496] This invention applies to communication systems, programs, and computer-readable recording media on which the programs are stored. [Explanation of Symbols]

[0497] 1-5, 11-15 Base stations, 6, 7 Control devices, 10, 10A Communication systems, 20, 30, 40, 50 Terminal devices, 21, 73 Buffers, 22, 62, 72 Processing means, 23, 74 Transmitting means, 24 Antenna, 61, 71 Receiving means, 63 N buffer, 64 C buffer.

Claims

1. Multiple base stations are arranged in the communication space between them and the source, having communication ranges that cover mutually different communication spaces, and receiving packets broadcast from the source. The device includes a control unit that receives packets from the aforementioned multiple base stations, performs reception processing on the received packets to generate received packets, and transmits the generated received packets to a destination via the network. A communication system in which the control device receives, as the packet, an encoded packet obtained by encoding a first standalone packet, or a combined packet obtained by adding the encoded packet to a second standalone packet different from the first standalone packet, from the plurality of base stations.

2. The communication system according to claim 1, wherein, when the packet received from the plurality of base stations consists of a plurality of encoded packets, in the reception process, the control device decodes the encoded packets to obtain a plurality of first single packets, and generates the received packet by rearranging a plurality of third single packets, which consist of a plurality of third single packets that are different from the first single packets and have been obtained by eliminating duplication of the plurality of first single packets, in the order of their sequence numbers.

3. The communication system according to claim 2, wherein the control device solves a plurality of simultaneous equations representing the plurality of encoded packets to obtain the plurality of third individual packets.

4. The communication system according to claim 1, wherein when the packet received from the plurality of base stations consists of a plurality of the combined packets, in the reception process, the control device decodes the encoded packet of the combined packet to obtain a plurality of the first individual packets, and generates the received packet by rearranging a plurality of third individual packets, which consist of a plurality of third individual packets that are different from the first individual packets and the second individual packets, obtained by eliminating the duplication of the plurality of first individual packets and the second individual packets of the combined packet, in the order of their sequence numbers.

5. The communication system according to claim 4, wherein the sequence numbers of the plurality of third individual packets are smaller than the sequence number of the first individual packet.

6. The communication system according to claim 5, wherein when the encoded packet contains n (where n is an integer of 1 or more) second individual packets, the control device, upon receiving n mutually distinct combined packets, solves a system of simultaneous equations consisting of n expressions representing the n encoded packets contained in the n combined packets to obtain the plurality of third individual packets.

7. The communication system according to claim 1, wherein when the control device receives a further plurality of individual packets as the packet from the plurality of base stations, in the reception process, it resolves the duplication of the plurality of individual packets, and generates the received packet by rearranging the plurality of fourth individual packets, which consist of a plurality of fourth individual packets that have had the duplication resolved and which are different from the first individual packet and the second individual packet, in the order of their sequence numbers.

8. The communication system according to any one of claims 1 to 7, wherein the plurality of base stations receive packets broadcast from the source without synchronizing with each other.

9. A program that is executed in a communication system that receives a packet broadcast from a source and transmits it to a destination, The communication system comprises a plurality of base stations arranged to have a communication range that covers mutually different communication spaces in the communication space with the source, and which receive packets broadcast from the source. The aforementioned program, The receiving means performs a first step of receiving the packets from the plurality of base stations, The processing means performs a reception process on the packet received in the first step to generate a received packet, The transmitting means causes the computer to perform a third step of transmitting the received packets generated in the second step to the destination via the network, The receiving means is a program to be executed by a computer, which in the first step receives, as packets, encoded packets obtained by encoding a first standalone packet, or combined packets obtained by adding the encoded packet to a second standalone packet different from the first standalone packet, from the plurality of base stations.

10. The processing means, when the packet received from the plurality of base stations in the first step consists of a plurality of coded packets, in the reception processing of the second step, decodes the coded packets to obtain a plurality of first single packets, and generates the received packet by rearranging a plurality of third single packets, which consist of a plurality of third single packets that are different from the first single packets and have been obtained by eliminating duplication of the plurality of first single packets, in order of sequence number. This is a program to be executed by a computer according to claim 9.

11. The processing means is a program to be executed by a computer according to claim 10, which in the receiving process of the second step solves a plurality of simultaneous equations representing the plurality of coded packets to obtain the plurality of third individual packets.

12. The program for a computer to execute according to claim 9, wherein the processing means, when the packets received from the plurality of base stations in the first step consist of a plurality of the combined packets, in the reception processing of the second step, decodes the encoded packets of the combined packets to obtain a plurality of the first individual packets, and generates the received packets by rearranging a plurality of third individual packets, which consist of a plurality of third individual packets that are different from the first individual packets and the second individual packets, in order of sequence number, after eliminating the duplication of the plurality of first individual packets and the second individual packets of the combined packets.

13. The program for a computer to be executed according to claim 12, wherein the sequence numbers of the plurality of third individual packets are smaller than the sequence number of the first individual packet.

14. The processing means is a program to be executed by a computer according to claim 13, wherein, when the encoded packet contains n (where n is an integer of 1 or more) second individual packets, in the receiving process of the second step, at the time when n mutually different combined packets are received, the program solves a system of linear equations consisting of n equations representing the n encoded packets contained in the n combined packets to obtain the plurality of third individual packets.

15. The program for a computer to execute according to claim 9, wherein the processing means, in the first step, receives a further plurality of individual packets as the packets from the plurality of base stations, in the reception processing of the second step, resolves the duplication of the plurality of individual packets, and generates the received packet by rearranging the plurality of fourth individual packets, which consist of a plurality of fourth individual packets from which the duplication has been resolved and which are different from the first individual packet and the second individual packet, in the order of their sequence numbers.

16. A program to be executed by a computer according to any one of claims 9 to 15, wherein the plurality of base stations receive packets broadcast from the source without synchronizing with each other.

17. A computer-readable recording medium having a program described in any one of claims 9 to 16 recorded on it.

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