Relay system, and relay method

Abstract

To provide a relay system capable of expanding the coverage area of signals related to wireless communication from a base station.SOLUTION: The relay system includes: a relay donor that performs wireless communication by using a base station and a first frequency band; and multiple relay nodes that perform wireless communication by using at least one terminal and the first frequency band. The relay donor performs wireless communication by using multiple relay nodes and a second frequency band different from the first frequency band.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a relay system and a relay method. [Background technology]

[0002] Non-Patent Document 1 discloses the use of a repeater to extend the transmission distance of a signal related to wireless communication of a base station. The repeater receives one of the beams transmitted from the base station and forwards the signal of the received beam. The terminal receives the signal forwarded by the repeater. The repeater also receives a signal transmitted from the terminal and forwards the received signal to the base station. The base station receives the signal forwarded by the repeater. The repeater extends the transmission distance of the signal by relaying the signal transmitted and received between the base station and the terminal. Hereinafter, the signal relayed by the repeater is referred to as a relayed signal. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] 3GPP TS 38.106,NR Repeater Radio Transmission and Reception V18.0.0(2023-03) Summary of the Invention [Problem to be solved by the invention]

[0004] However, the repeater disclosed in Non-Patent Document 1 has a limited beam when transferring a relay signal, so although it can extend the transmission distance, it is difficult to expand the coverage area in which a terminal can transmit and receive a relay signal. Also, the repeater disclosed in Non-Patent Document 1 has a limited beam when transferring a relay signal, so if there is an obstruction in that direction, it is difficult to transmit and receive signals to and from a terminal that is beyond the obstruction.

[0005] Therefore, an object of the present disclosure is to provide a relay system and a relay method capable of expanding the coverage area of ​​a signal related to wireless communication of a base station. [Means for solving the problem]

[0006] The relay system according to the present disclosure includes a relay donor that performs wireless communication with a base station using a first frequency band, and a plurality of relay nodes that perform wireless communication with at least one terminal using the first frequency band, and the relay donor performs wireless communication with the plurality of relay nodes using a second frequency band different from the first frequency band.

[0007] In the relay method of the present disclosure, a relay donor and a base station perform wireless communication using a first frequency band, the relay donor and a plurality of relay nodes perform wireless communication using a second frequency band different from the first frequency band, and the plurality of relay nodes and at least one terminal perform wireless communication using the first frequency band.

[0008] Furthermore, these comprehensive or specific aspects may be realized by a system, an apparatus, a method, an integrated circuit, a computer program, or a recording medium, or may be realized by any combination of a system, an apparatus, a method, an integrated circuit, a computer program, and a recording medium. Effect of the Invention

[0009] According to the technology of the present disclosure, it is possible to expand the coverage area of ​​signals related to wireless communication of a base station. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram showing an example of a configuration of a communication system according to a first embodiment; [Diagram 2] FIG. 1 is a block diagram showing an example of a configuration of a relay donor according to the first embodiment. [Diagram 3] FIG. 1 is a block diagram showing an example of a configuration of a relay node according to a first embodiment; [Figure 4]FIG. 1 is a diagram showing an example of arrangement of relay signals and control signals between a relay donor and each relay node in a second frequency band according to the first embodiment; [Diagram 5] FIG. 1 is a diagram for explaining the relationship between a propagation delay time and a guard interval time according to the first embodiment; [Figure 6] A flowchart showing an example of a transition process between a dormant state and an operational state of a relay node according to the first embodiment. [Figure 7] A flowchart showing an example of a process for adjusting the transmission power of a relay node according to the first embodiment. [Figure 8] FIG. 1 is a diagram for explaining a first method for estimating the location of a terminal according to a first embodiment; [Figure 9] FIG. 1 is a diagram for explaining a second method for estimating the position of a terminal according to the first embodiment; [Figure 10] A flowchart showing an example of a process for estimating the position of a terminal according to the first embodiment. [Figure 11] 11 is a flowchart showing the continuation of the process shown in FIG. 10. [Figure 12] FIG. 1 is a diagram for explaining a method for determining a radio frequency of a signal between a relay node and a terminal according to a first embodiment. [Figure 13] FIG. 1 is a diagram for explaining a method for determining a radio frequency of a signal between a relay node and a terminal according to a first embodiment, and a radio frequency of a relay signal between a relay donor and the relay node; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, the embodiments of the present disclosure will be described in detail with reference to the drawings as appropriate. However, more detailed description than necessary may be omitted. For example, detailed description of already well-known matters and duplicated description of substantially the same configuration may be omitted. This is to avoid the following description becoming unnecessarily redundant and to facilitate understanding by those skilled in the art. Note that the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

[0012] (Embodiment 1) <System configuration> FIG. 1 is a schematic diagram showing an example of a configuration of a communication system 1 according to the first embodiment.

[0013] As shown in FIG. 1, a communication system 1 includes a base station 2, a relay system 3, and terminals 4 (4A, 4B, 4C).

[0014] The relay system 3 is a system for relaying signals related to wireless communication between the base station 2 and the terminal 4, and includes a relay donor 10 and a plurality of relay nodes 50 (50A, 50B, 50C, 50D). Note that, in the present embodiment, a case where four relay nodes 50 are installed will be described as an example, but any number of relay nodes 50 may be installed as long as it is two or more.

[0015] The base station 2 transmits radio waves carrying signals related to wireless communication with the terminal 4. The base station 2 and the terminal 4 may perform wireless communication conforming to 3GPP (registered trademark) standards such as LTE, 4G, 5G, or 6G, which is currently under consideration. The base station 2 performs wireless communication using a first frequency band. The first frequency band may be, for example, a millimeter wave band including the 28 GHz band. However, the first frequency band is not limited to 28 GHz or the millimeter wave band. The base station 2 may transmit signals by beamforming to ensure a transmission distance. Note that the base station 2 may be read as a gNB.

[0016] The relay donor 10 receives a signal transmitted from the base station 2 using a first frequency band, and transfers (transmits) the received signal to each of the relay nodes 50A, 50B, 50C, and 50D using a second frequency band different from the first frequency band. The relay donor 10 may be configured to receive one beam out of multiple beams transmitted by the base station 2 through beamforming. This ensures a transmission distance between the base station 2 and the relay donor 10. The second frequency band may be, for example, the 60 GHz band. However, the second frequency band is not limited to the 60 GHz band. The relay donor 10 may be read as a repeater donor.

[0017] The multiple relay nodes 50A, 50B, 50C, and 50D receive a signal transferred (transmitted) from the relay donor 10 using the second frequency band, and transfer (transmit) the received signal to each terminal 4 using the first frequency band. By appropriately installing the multiple relay nodes 50A, 50B, 50C, and 50D, it is possible to expand the coverage area 6, which is an area in which the terminal 4 can receive a signal transmitted from the base station 2, compared to the case where the base station 2 is installed alone. Also, by separating the relay donor 10 and the multiple relay nodes 50 as in this embodiment, it is possible to expand the coverage area 6 compared to the case where one integrated repeater is installed between the base station 2 and the terminal 4 as in Non-Patent Document 1.

[0018] When the terminal 4 is present within the coverage area 6, it can receive a signal transmitted from the relay node 50 using the first frequency band (i.e., a signal transmitted from the base station 2). The terminal 4 may perform reception between the relay node 50 and the terminal 4 using beamforming. The terminal 4 may also enhance the diversity effect by receiving and combining signals transmitted from each of the multiple relay nodes 50. The terminal 4 may be read as a UE.

[0019] In the above, the downlink direction in which a signal is transmitted from the base station 2 to the terminal 4 via the relay donor 10 and the relay node 50 has been described. In the uplink direction in which a signal is transmitted from the terminal 4 to the base station 2 via the relay node 50 and the relay donor 10, the signal flows in the opposite direction to the downlink direction described above. That is, in the uplink direction, the terminal 4 transmits a signal to the relay node 50 using a first frequency band. The relay node 50 transfers (transmits) the signal received in the first frequency band to the relay donor 10 using a second frequency band. The relay donor 10 transfers (transmits) the signal received in the second frequency band to the base station 2 using the first frequency band. The base station 2 receives the signal in the first frequency band.

[0020] <Composition of relay donors> FIG. 2 is a block diagram showing an example of the configuration of the relay donor 10 according to the first embodiment.

[0021] As shown in FIG. 2, the relay donor 10 includes a first communication unit 20, a distribution / combination unit 42, a second communication unit 30, a control unit 40, and a storage unit 41.

[0022] First, downstream signal processing will be described.

[0023] The first communication unit 20 performs processing for performing wireless communication with the base station 2 in the first frequency band. The first communication unit 20 includes a first antenna 21, a first transceiver unit 22, and a first intermediate frequency conversion unit 23. Note that the first transceiver unit 22 and the first intermediate frequency conversion unit 23 may be realized as hardware in a dedicated integrated circuit, or may be realized as software executed in a general-purpose integrated circuit.

[0024] The first antenna 21 receives radio waves in the first frequency band transmitted from the base station 2. The first antenna 21 may be an array antenna. In this case, the first antenna 21 (array antenna) may be set to receive one beam out of multiple beams transmitted from the base station 2 by beamforming.

[0025] The first transceiver 22 extracts a signal from the radio wave received by the first antenna 21 (that is, the signal transmitted from the base station 2).

[0026] The first intermediate frequency converter 23 converts the signal extracted by the first transmitter / receiver 22 into a predetermined intermediate frequency. In this case, 0 Hz may be used as the intermediate frequency (in this case, the baseband signal may be separated into an in-phase component and a quadrature component).

[0027] The distributor / synthesizer 42 distributes and transmits the signal converted by the first intermediate frequency converter 23 to each of the relay nodes 50A, 50B, 50C, and 50D.

[0028] The second communication unit 30 performs processing for performing wireless communication with each of the relay nodes 50A, 50B, 50C, and 50D in the second frequency band.

[0029] The second communication unit 30 includes a set of a second antenna 31, a second transceiver unit 32, and a second intermediate frequency converter unit 33 for each of the relay nodes 50A, 50B, 50C, and 50D. That is, the number of sets may be the same as the number of relay nodes 50 to be installed. Also, it may be set as to which set performs wireless communication with which relay node 50. The second transceiver unit 32 and the second intermediate frequency converter unit 33 may be realized as hardware in a dedicated integrated circuit, or may be realized as software executed in a general-purpose integrated circuit.

[0030] The second intermediate frequency converter 33 converts the intermediate frequency signal for the relay node 50 targeted by the set, which is output from the distributor / synthesizer 42, into a signal in the second frequency band.

[0031] The second transceiver 32 transmits the signal converted into the second frequency band by the second intermediate frequency converter 33 over radio waves from the second antenna 31 to the relay node 50 targeted by the set.

[0032] The second antenna 31 transmits radio waves in the second frequency band carrying a signal from the second transceiver 32. The second antenna 31 may be an array antenna. In this case, the second antenna 31 (array antenna) may be set to perform beamforming toward the relay node 50 targeted by the set.

[0033] Next, the upstream signal processing will be described.

[0034] The second antenna 31 receives radio waves in the second frequency band from the relay node 50 .

[0035] The second transceiver 32 extracts a signal (i.e., a signal transmitted by the terminal 4) from the radio wave received by the second antenna 31. The second intermediate frequency converter 33 converts the signal extracted by the second transceiver 32 into a predetermined intermediate frequency. In this case, 0 Hz may be used as the intermediate frequency (in this case, the baseband signal may be separated into an in-phase component and a quadrature component).

[0036] The distribution / combination unit 42 combines the signals output from the second intermediate frequency conversion units 33 corresponding to each relay node 50. In this way, when a signal transmitted from the terminal 4 is received by a plurality of relay nodes 50, the signals received by each of the plurality of relay nodes 50 are combined by the distribution / combination unit 42, so that the relay donor 10 can obtain a signal with high communication quality (e.g., with less noise) due to the diversity effect. As a combining method, for example, selective combining, maximum ratio combining, equal gain combining, or other combining methods may be used.

[0037] The first intermediate frequency converter 23 converts the intermediate frequency signal combined by the distributor / combiner 42 into a signal in the first frequency band.

[0038] The first transceiver 22 transmits the signal converted into the first frequency band by the first intermediate frequency converter 23 over radio waves from the first antenna 21 to the base station 2.

[0039] The first antenna 21 transmits radio waves in the first frequency band carrying a signal from the first transceiver 22. The first antenna 21 may be set to perform beamforming toward the base station 2.

[0040] The control unit 40 performs processing for implementing the functions of the relay donor 10. The control unit 40 also performs processing for controlling the behavior of the first communication unit 20, the distribution / combining unit 42, and the second communication unit 30. The control unit 40 may be interpreted as a processor, a controller, a Central Processing Unit (CPU), a Field Programmable Gate Array (FPGA), an Application Specific Integrated Circuit (ASIC), or the like. Details of the processing performed by the control unit 40 will be described later.

[0041] The storage unit 41 stores programs and data used in processing by the control unit 40. The storage unit 41 may be configured with a volatile storage medium, a non-volatile storage medium, or a combination thereof. The control unit 40 may realize the functions of the relay donor 10 by reading and executing the programs from the storage unit 41.

[0042] <Relay node configuration> FIG. 3 is a block diagram showing an example of the configuration of the relay node 50 according to the first embodiment.

[0043] The relay node 50 includes a third communication unit 60, a fourth communication unit 70, a control unit 80, and a storage unit 81.

[0044] First, downstream signal processing will be described.

[0045] The third communication unit 60 performs processing for performing wireless communication with the relay donor 10 in the second frequency band. The third communication unit 60 includes a third antenna 61, a third transceiver unit 62, and a third intermediate frequency conversion unit 63. Note that the third transceiver unit 62 and the third intermediate frequency conversion unit 63 may be realized as hardware in a dedicated integrated circuit, or may be realized as software executed in a general-purpose integrated circuit.

[0046] The third antenna 61 receives radio waves in the second frequency band transmitted from the relay donor 10. The third antenna 61 may be an array antenna. In this case, the third antenna 61 (array antenna) may be set to receive the relay donor 10 by beamforming.

[0047] The third transceiver 62 extracts a signal from the radio wave received by the third antenna 61 (that is, the signal transmitted from the base station 2).

[0048] The third intermediate frequency converter 63 converts the signal extracted by the third transceiver 62 to a predetermined intermediate frequency. In this case, 0 Hz may be used as the intermediate frequency (in this case, the baseband signal may be separated into an in-phase component and a quadrature component).

[0049] The fourth communication unit 70 performs processing for performing wireless communication with the terminal 4 in the first frequency band. The fourth communication unit 70 includes a fourth intermediate frequency conversion unit 73, a fourth transceiver unit 72, and a fourth antenna 71. Note that the fourth transceiver unit 72 and the fourth intermediate frequency conversion unit 73 may be realized as hardware in a dedicated integrated circuit, or may be realized as software executed in a general-purpose integrated circuit.

[0050] The fourth intermediate frequency converter 73 converts the signal converted to a predetermined intermediate frequency by the third intermediate frequency converter 63 into a signal in the first frequency band.

[0051] The fourth transceiver 72 transmits the signal converted into the first frequency band by the fourth intermediate frequency converter 73 over radio waves from the fourth antenna 71 to the terminal 4 .

[0052] The fourth antenna 71 transmits radio waves in the first frequency band carrying a signal from the fourth transceiver 72. The fourth antenna 71 may be an array antenna. In this case, the fourth antenna 71 (array antenna) may be set to perform beamforming toward the terminal 4.

[0053] Next, the upstream signal processing will be described.

[0054] The fourth antenna 71 receives radio waves in the first frequency band from the terminal 4 .

[0055] The fourth transceiver 72 extracts a signal from the radio wave received by the fourth antenna 71 (that is, the signal transmitted by the terminal 4).

[0056] The fourth intermediate frequency converter 73 converts the signal extracted by the fourth transceiver 72 into a predetermined intermediate frequency. In this case, 0 Hz may be used as the intermediate frequency (in this case, the baseband signal may be separated into an in-phase component and a quadrature component).

[0057] The third intermediate frequency converter 63 converts the signal converted to an intermediate frequency by the fourth intermediate frequency converter 73 into a signal in the second frequency band.

[0058] The third transceiver 62 transmits the signal converted into the second frequency band by the third intermediate frequency converter 63 via radio waves from the third antenna 61 to the relay donor 10 .

[0059] The third antenna 61 transmits radio waves in the second frequency band carrying the signal from the second transceiver 32. The third antenna 61 may be set to perform beamforming toward the relay donor .

[0060] The control unit 80 performs processing for implementing the functions of the relay node 50. The control unit 80 also performs processing for controlling the behavior of the third communication unit 60 and the fourth communication unit 70. The control unit 80 may be interpreted as a processor, a controller, a CPU, an FPGA, an ASIC, or the like. Details of the processing performed by the control unit 80 will be described later.

[0061] The storage unit 81 stores programs and data used in processing by the control unit 80. The storage unit 81 may be configured with a volatile storage medium, may be configured with a non-volatile storage medium, or may be configured with a combination of them. The control unit 80 may realize the functions of the relay node 50 by reading and executing a program from the storage unit 81.

[0062] <Signal arrangement in the second frequency band> FIG. 4 is a diagram showing an example of allocation of relay signals and control signals between the relay donor 10 and each of the relay nodes 50A, 50B, 50C, and 50D in the second frequency band according to the first embodiment.

[0063] The relay donor 10 and the relay node 50 transmit and receive relay signals for relaying signals from the base station 2 to the terminal 4 and signals from the terminal 4 to the base station 2, and control signals for exchanging control information between the relay donor 10 and the relay node 50.

[0064] As shown in Fig. 4, the relay signal and the control signal may be arranged at different radio frequencies for each of the relay nodes 50A, 50B, 50C, and 50D. Also, as shown in Fig. 4, the radio frequencies of the relay signal and the control signal for one relay node 50 may be arranged to be adjacent to each other in the frequency domain. This allows the relay donor 10 and the multiple relay nodes 50A, 50B, 50C, and 50D to simultaneously transmit and receive the relay signal and the control signal.

[0065] <Relationship between propagation delay time and guard interval time> FIG. 5 is a diagram for explaining the relationship between the propagation delay time and the guard interval time according to the first embodiment.

[0066] As shown in FIG. 5, the relay donor 10 can simultaneously transmit a relay signal to each of the relay nodes 50A, 50B, 50C, and 50D, but there may be a time lag in the timing at which the terminal 4 receives the relay signals transmitted from each of the relay nodes 50A, 50B, 50C, and 50D.

[0067] In this embodiment, each relay node 50 is installed so that the maximum time difference between relay signals received from each relay node 50 by a terminal 4 present within a coverage area 6 is equal to or less than the guard interval time in Orthogonal Frequency Division Multiplexing (OFDM).

[0068] For example, as shown in FIG. 5, let the time when one symbol of OFDM transmitted from relay node 50A reaches terminal 4 be t1, the time when the same one symbol transmitted from relay node 50B reaches the same terminal 4 be t2, the time when the same one symbol transmitted from relay node 50C reaches the same terminal 4 be t3, and the time when the same one symbol transmitted from relay node 50D reaches the same terminal 4 be t4. And, as shown in FIG. 5, assume that t1 < t3 < t2 < t4. In this case, the maximum value of the time shift between the relay signals is |t4 - t1|. Therefore, the relay nodes 50A, 50B, 50C, and 50D are arranged so that for terminal 4 within coverage area 6, "|t4 - t1| ≤ guard interval time".

[0069] That is, when M and N are the identification numbers of relay nodes 50, and tM and tN are the times when one symbol reaches terminal 4 from relay nodes M and N, the relay nodes 50 are arranged so that for terminal 4 existing within coverage area 6, "max|tM - tN| ≤ guard interval time".

[0070] Thereby, terminal 4 existing within coverage area 6 can combine the relay signals received from each of relay nodes 50A, 50B, 50C, and 50D without interfering with each other, and can obtain a diversity effect.

[0071] <Rest of Relay Node> Terminal 4 can receive signals from each of relay nodes 50A, 50B, 50C, and 50D. However, when receiving a signal with a reception signal level of 0 or extremely low (for example, less than a predetermined threshold), such a signal becomes noise for terminal 4. Also, each relay node 50 can receive signals transmitted from terminal 4. However, when receiving a signal with a reception signal level of 0 or extremely low (for example, less than a predetermined threshold), such a signal becomes noise in the combination in distribution combining unit 42.

[0072] Therefore, in this embodiment, the operation of the relay node 50 that transmits and / or receives a signal with a received signal level below a predetermined threshold between the relay node 50 and the terminal 4 is suspended. The suspended relay node 50 suspends the transmission and / or reception of signals between the relay node 50 and the terminal 4. As a result, the terminal 4 does not receive a signal with a received signal level below the predetermined threshold from the relay node 50, and can obtain a signal with less noise. Similarly, the relay node 50 does not receive a signal with a received signal level below the predetermined threshold from the terminal 4, and the distribution / combining unit 42 can obtain a signal with less noise. An example of the process of the relay node 50 for achieving the above content will be described below.

[0073] FIG. 6 is a flowchart showing an example of a transition process between the hibernation state and the operation state of the relay node 50 according to the first embodiment.

[0074] The control unit 80 of the relay node 50 receives the reception signal level from the terminal 4 via the fourth transceiver unit 72, and determines whether the reception signal level is below a predetermined threshold value (S101).

[0075] If the received signal level is equal to or higher than the predetermined threshold (S101: NO), the control unit 80 of the relay node 50 repeats the process of step S101. In other words, the relay node 50 continues the operating state.

[0076] If the received signal level is below the predetermined threshold (S101: YES), the control unit 80 of the relay node 50 puts the fourth communication unit 70 into a suspended state (S102). That is, the control unit 80 of the relay node 50 prevents the fourth communication unit 70 from performing wireless communication with the terminal 4. As a result, the relay node 50 will no longer transmit or receive a signal whose received signal level is below the predetermined threshold to or from the terminal 4, and therefore the communication quality of the signal in the distribution / combining unit 42 may improve.

[0077] The control unit 80 of the relay node 50 notifies the relay donor 10 of state information indicating that the fourth communication unit 70 of the relay node 50 has entered a dormant state via the third communication unit 60 (S103), and proceeds to step S111. When the control unit 40 of the relay donor 10 receives the notification of step S103, it stores in the storage unit 41 and manages the information that the relay node 50 that sent the notification is in a dormant state.

[0078] The control unit 80 of the relay node 50 judges whether or not a request for transition to an operational state has been received from the relay donor 10 through the third communication unit 60 (S111). When the relay node 50 managed as being in a dormant state in the storage unit 41 satisfies a predetermined condition (for example, when a predetermined period has elapsed or when the terminal 4 has moved), the control unit 40 of the relay donor 10 may transmit a request for transition to an operational state to the relay node 50.

[0079] When the control unit 80 of the relay node 50 has not received a request to transition to the active state from the relay donor 10 (S111: NO), the control unit 80 repeats the process of step S111. In other words, the relay node 50 continues the dormant state.

[0080] When the control unit 80 of the relay node 50 receives a request to transition to the active state from the relay donor 10 (S111: YES), it puts the fourth communication unit 70 into the active state (S112).

[0081] The control unit 80 of the relay node 50 notifies the relay donor 10 of state information indicating that the fourth communication unit 70 of the relay node 50 has entered an operational state via the third communication unit 60 (S113), and returns the process to step S101. When the control unit 40 of the relay donor 10 receives the notification of step S113, it stores in the storage unit 41 and manages the fact that the relay node 50 that is the sender of the notification is in an operational state.

[0082] By the above process, the relay donor 10 can switch the relay node 50 between a dormant state and an active state according to the reception signal level of the terminal 4.

[0083] <Adjustment of transmission power of relay nodes> The total power value of signals transmitted from the multiple relay nodes 50A, 50B, 50C, and 50D constituting the coverage area 6 is specified not to exceed a certain level. Therefore, when one or more of the multiple relay nodes 50A, 50B, 50C, and 50D constituting the coverage area 6 are put into a dormant state by the above-mentioned method, the power value of signals transmitted from the relay node 50 in operation may be increased within a range in which the total power value of signals transmitted from the remaining relay nodes 50 in operation does not exceed a certain level. This makes it possible to maintain the communication quality of the terminal 4 in the coverage area 6 even if one or more relay nodes 50 in the coverage area 6 are put into a dormant state by the above-mentioned method. An example of the process of the relay node 50 for realizing the above content will be described below.

[0084] FIG. 7 is a flowchart showing an example of a transmission power adjustment process of the relay node 50 according to the first embodiment.

[0085] The control unit 80 of the relay node 50 determines whether or not a request to increase transmission power has been received from the relay donor 10 (S201).

[0086] When a request to increase transmission power has been received (S201: YES), the control unit 80 of the relay node 50 controls the fourth transceiver unit 72 to increase the power value of the signal to be transmitted to the terminal 4 (S202). The amount of increase in the power value may be instructed by the request to increase transmission power. Then, the control unit 80 of the relay node 50 returns the process to step S201.

[0087] If a request to increase transmission power has not been received (S201: NO), the control unit 80 of the relay node 50 determines whether a request to decrease transmission power has been received from the relay donor 10 (S211).

[0088] When the request to reduce transmission power is received (S211: YES), the control unit 80 of the relay node 50 controls the fourth transceiver unit 72 to reduce the power value of the signal to be transmitted to the terminal 4 (S212). The amount of reduction in the power value may be instructed by the request to reduce transmission power. Then, the control unit 80 of the relay node 50 returns the process to step S201.

[0089] If a transmission power reduction request has not been received (S211: NO), the control unit 80 of the relay node 50 returns the process to step S201.

[0090] The control unit 40 of the relay donor 10 may transmit a request to increase or decrease transmission power to the relay nodes 50 in operation using a control signal. At this time, the control unit 40 of the relay donor 10 determines the amount of increase or decrease in the power value at each relay node 50 so that the total power value of the signals transmitted from the relay nodes 50 in operation does not exceed a certain level.

[0091] For example, when one or more relay nodes 50 are put into a dormant state, the control unit 40 of the relay donor 10 determines an amount of increase in the power value of each relay node 50 in an operational state such that the sum of the power values ​​of signals transmitted from the remaining relay nodes 50 in an operational state is at a constant level. The amount of increase in the power value may be constant for each relay node 50 in an operational state, or may be different for each relay node 50 in an operational state. In other words, when there is a relay node 50 that has been put into a dormant state, at least one of the remaining relay nodes 50 in an operational state may have a higher power value (level) of a signal transmitted to the terminal 4 compared to when all relay nodes 50 are in an operational state.

[0092] For example, when one or more relay nodes 50 are changed from a dormant state to an operational state, the control unit 40 of the relay donor 10 determines the amount of reduction in the power value of each relay node 50 in the operational state so that the sum of the power values ​​of signals transmitted from the relay nodes 50 in the operational state is at a constant level. The amount of reduction in the power value may be constant among the relay nodes 50 in the operational state, or may be different among the relay nodes 50 in the operational state.

[0093] <Device location estimation> FIG. 8 is a diagram for explaining a first method for estimating the position of terminal 4 according to the first embodiment.

[0094] As shown in FIG. 8, when the antenna of the terminal 4 is an omni-pattern, the signal transmitted by the terminal 4 can reach each of the relay nodes 50A, 50B, 50C, and 50D constituting the coverage area 6. The control unit 80 of each of the relay nodes 50A, 50B, 50C, and 50D measures the signal strength of the signal received from the terminal 4 and transmits it to the relay donor 10. Examples of the measured value of the signal strength include Received Signal Strength Indicator (RSSI) or Reference Signal Received Power (RSRP). The signal strength is inversely proportional to the square of the propagation distance of the signal. Therefore, the control unit 40 of the relay donor 10 can estimate the distance from each of the relay nodes 50A, 50B, 50C, and 50D to the terminal 4 and the position of the terminal 4 in the coverage area 6 based on the signal strength measured by each of the relay nodes 50A, 50B, 50C, and 50D.

[0095] FIG. 9 is a diagram for explaining a second method for estimating the position of terminal 4 according to the first embodiment.

[0096] As shown in Fig. 9, when the antenna of the terminal 4 has a beam pattern, a signal transmitted from the terminal 4 can reach multiple relay nodes 50A, 50B, and 50C that are in the direction of the beam. The control unit 80 of each relay node 50A, 50B, and 50C that the beam reaches measures the time at which the signal from the terminal 4 is received (hereinafter referred to as the reception time) and transmits it to the relay donor 10. The reception time is delayed in proportion to the propagation distance of the signal. Therefore, the control unit 40 of the relay donor 10 can estimate the distance from each relay node 50A, 50B, and 50C to the terminal 4 and the position of the terminal 4 in the cover area 6 based on the reception time measured by each relay node 50A, 50B, and 50C.

[0097] Hereinafter, information transmitted from each relay node 50 to the relay donor 10, including at least one of the above-mentioned signal strength and reception time, is referred to as positioning information. Note that the positioning information is not limited to the above-mentioned signal strength and reception time, as long as it can be used for positioning the terminal 4. An example of the process of the relay system 3 for estimating the position of the terminal 4 will be described below.

[0098] FIG. 10 is a flowchart showing an example of a process for estimating the position of the terminal 4 according to the first embodiment.

[0099] The control unit 40 of the relay donor 10 controls the second transceiver unit 32 to request all relay nodes 50 in an operational state to report positioning information (S301).

[0100] The control unit 80 of the relay node 50 determines whether or not a request for reporting positioning information has been received from the relay donor 10 via the third communication unit 60 (S302).

[0101] If a request for reporting positioning information has not been received (S302: NO), the control unit 80 of the relay node 50 repeats the process of step S302.

[0102] When a request for reporting positioning information has been received (S302: YES), the control unit 80 of the relay node 50 controls the fourth communication unit 70 to measure the positioning information with the terminal 4 (S303).

[0103] The control unit 80 of the relay node 50 transmits (reports) the positioning information measured in step S303 to the relay donor 10 through the third communication unit 60 (S304).

[0104] The control unit 40 of the relay donor 10 judges whether or not reports of positioning information have been received from all relay nodes 50 in an operational state (S305).

[0105] If there remains a relay node 50 in operation that has not reported the positioning information (S305: NO), the control unit 40 of the relay donor 10 repeats the process of step S305.

[0106] When the control unit 40 of the relay donor 10 receives reports of positioning information from all relay nodes 50 in operation (S305: YES), the control unit 40 estimates the position of the terminal 4 based on the received positioning information (S306) as described above. The control unit 40 of the relay donor 10 records the estimated position of the terminal 4 and the time at that time in the storage unit 41.

[0107] The control unit 40 of the relay donor 10 predicts the future location of the terminal 4 using the past and current locations of the terminal 4 recorded in the memory unit 41 (S307). For example, the control unit 40 of the relay donor 10 estimates the moving direction and moving speed of the terminal 4 based on the past and current locations and time of the terminal 4, and predicts the future location of the terminal 4 from the estimated moving direction and moving speed.

[0108] The control unit 40 of the relay donor 10 determines which relay nodes 50 are to be in an operational state and which relay nodes 50 are to be in a dormant state based on the estimated current location of the terminal 4 and the predicted future location of the terminal 4 (S308). For example, when a relay node 50 covering the future location of the terminal 4 is in a dormant state, the control unit 40 of the relay donor 10 determines to put the relay node 50 in an operational state. For example, when a relay node 50 covering a location where the terminal 4 is not currently present is in an operational state, the control unit 40 of the relay donor 10 determines to put the relay node 50 in a dormant state. Then, the process proceeds to the next process A shown in FIG. 11.

[0109] FIG. 11 is a flowchart showing a continuation of the process shown in FIG.

[0110] As a continuation of the process A, the control unit 40 of the relay donor 10 transmits a request to transition to the operational state to the relay nodes 50 that have been determined to be in the operational state in step S308 out of the relay nodes 50 in the inactive state (S311).

[0111] The control unit 80 of the relay node 50 in the dormant state determines whether or not a request for transition to the active state has been received from the relay donor 10 through the third communication unit 60 (S312).

[0112] If a request to transition to the active state has not been received (S312: NO), the control unit 80 of the relay node 50 in the dormant state repeats the process of step S312. That is, the relay node 50 continues in the dormant state.

[0113] When a request to transition to the active state is received (S312: YES), the control unit 80 of the relay node 50 in the inactive state sets the fourth communication unit 70 to the active state (S313) and ends this process. As a result, the relay node 50 transitions to the active state.

[0114] Furthermore, the control unit 40 of the relay donor 10 transmits a request to transition to the dormant state to the relay nodes 50 that have been determined to be in the dormant state in step S308 among the relay nodes 50 in the operating state (S314).

[0115] The control unit 80 of the relay node 50 in the operating state determines whether or not a request for transition to the dormant state has been received from the relay donor 10 through the third communication unit 60 (S315).

[0116] If a request to transition to the dormant state has not been received (S315: NO), the control unit 80 of the relay node 50 in the active state repeats the process of step S315. In other words, the relay node 50 continues in the active state.

[0117] When a request to transition to the hibernation state is received (S315: YES), the control unit 80 of the relay node 50 in the operation state sets the fourth communication unit 70 to the hibernation state (S316) and ends this process. As a result, the relay node 50 transitions to the hibernation state.

[0118] Then, the control unit 40 of the relay donor 10 returns the process to process B (that is, step S301) shown in FIG.

[0119] Through the above process, the relay donor 10 can estimate the current location and future location of the terminal 4 in the coverage area 6. In addition, the relay donor 10 can put the relay node 50 covering an area where the terminal 4 does not exist into a dormant state, thereby realizing power saving of the relay node 50. Furthermore, the relay donor 10 can put the relay node 50 covering an area where the terminal 4 is predicted to exist in the future into an operational state in advance, thereby maintaining the communication quality of the terminal 4.

[0120] <How to determine the radio frequency of a signal> FIG. 12 is a diagram for explaining a method for determining the radio frequency of a signal between the relay node 50 and the terminal 4 according to the first embodiment.

[0121] 12, the radio frequency of the relay signal in the second frequency band between the relay donor 10 and the relay node 50 is f2, and the radio frequency of the control signal is f3. The radio frequency of the signal in the first frequency band between the relay node 50 and the terminal 4 is f1. For example, the relay donor 10 and the relay node 50 define integers m and n so that the radio frequencies are f1, f2, and f3 in accordance with the relationship shown in the following formula 1, and share the integers m and n. The integers m and n may be different for each relay node 50.

[0122] f2-f1=(m / n)×(f3-f2)…(Formula 1)

[0123] The control unit 40 of the relay donor 10 determines radio frequencies f2 and f3 corresponding to the relay node 50, and controls the second communication unit 30 to generate a relay signal of radio frequency f2 and a control signal of radio frequency f3. The control unit 80 of the relay node 50 determines a radio frequency f1 by substituting the radio frequency f2 of the relay signal and the radio frequency f3 of the control signal received from the relay donor 10, and the integers m and n shared in advance, into the above formula 1. Then, the control unit 80 of the relay node 50 controls the fourth communication unit 70 to generate a signal to the terminal 4 of the determined radio frequency f1.

[0124] This allows the relay node 50 to set the radio frequency f1 in the first frequency band of the signal to the terminal 4 with high accuracy.

[0125] FIG. 13 is a diagram for explaining a method for determining the radio frequency of a signal between the relay node 50 and the terminal 4 according to the first embodiment, and the radio frequency of a relay signal between the relay donor 10 and the relay node 50.

[0126] 13, the control unit 40 of the relay donor 10 determines the period T0 of the reference signal based on the reference signal included in the signal of the radio frequency f1 in the first frequency band received from the base station 2. The control unit 80 of the relay node 50 determines the period T0 of the reference signal based on the reference signal included in the relay signal of the radio frequency f2 in the second frequency band received from the relay donor 10.

[0127] For example, as shown in the following formula 2, it is assumed that a radio frequency f1 is determined by integers m1, n1 and a period T0. Also, as shown in the following formula 3, it is assumed that a radio frequency f2 is determined by integers m2, n2 and a period T0. The integers m1, n1, m2, and n2 may be different for each relay node 50. Also, the relay donor 10 and each relay node 50 share the integers m1, n1, m2, and n2 in advance.

[0128] f1=(m1 / n1)×(1 / T0)…(Formula 2) f2=(m2 / n2)×(1 / T0)…(Equation 3)

[0129] The control unit 40 of the relay donor 10 substitutes the integers m2 and n2 corresponding to the relay node 50 and the period T0 into Equation 3 to determine the radio frequency f2 of the relay node 50. Then, the control unit 40 of the relay donor 10 controls the second communication unit 30 to generate a relay signal of the determined radio frequency f2. Note that the radio frequency f3 (not shown in FIG. 13) of the control signal may be determined to be a predetermined frequency shift from the radio frequency f2 of the relay signal.

[0130] This allows the relay donor 10 to set the radio frequency f2 in the second frequency band of the relay signal to the relay node 50 with high accuracy.

[0131] Furthermore, the control unit 80 of the relay node 50 determines the radio frequency f1 by substituting the integers m1, n1 and period T0 corresponding to the relay node 50 into Equation 2. Then, the control unit 80 of the relay node 50 controls the fourth communication unit 70 to generate a signal to the terminal 4 at the determined radio frequency f1.

[0132] This allows the relay node 50 to set the radio frequency f1 in the first frequency band of the signal to the terminal 4 with high accuracy.

[0133] Summary of the Disclosure The above description of the first embodiment discloses the following techniques.

[0134] <Technology 1> The relay system (3) includes a relay donor (10) that performs wireless communication with a base station (2) using a first frequency band, and a plurality of relay nodes (50) that perform wireless communication with at least one terminal (4) using the first frequency band, and the relay donor performs wireless communication with the plurality of relay nodes using a second frequency band different from the first frequency band. As a result, a signal transmitted from a base station is transferred to multiple relay nodes via the relay donor, and is then transmitted to the terminal by the multiple relay nodes. Therefore, by appropriately arranging multiple relay nodes, it is possible to expand the coverage area (6) in which wireless communication with the base station is possible.

[0135] <Technology 2> In the relay system described in Technique 1, the relay donor distributes a signal received from the base station to each of the multiple relay nodes and transmits the distributed signal. This allows the terminal to receive the same signal from multiple relay nodes, and therefore allows the terminal to obtain high quality signals due to the diversity effect.

[0136] <Technology 3> In the relay system according to Technique 1 or 2, the relay donor combines signals received from each of the multiple relay nodes and transmits the combined signals to the base station. This allows the relay donor to combine the same signal received from the terminal by each of the multiple relay nodes, thereby obtaining a high quality signal.

[0137] <Technology 4> In the relay system according to any one of Techniques 1 to 3, the multiple relay nodes are arranged so that a maximum delay time between signals received by the terminal from each of the multiple relay nodes is equal to or less than a predetermined guard interval. This allows the terminal to receive the same signal from multiple relay nodes and combine them, making it possible to obtain a high quality signal due to the diversity effect.

[0138] <Technology 5> In the relay system according to any one of the first to fourth techniques, the relay node in which the level of the signal received from the terminal is less than a predetermined threshold value suspends operation. As a result, the terminal does not receive a signal whose level is below a predetermined threshold from the relay node, and can obtain a signal with less noise.

[0139] <Technology 6> In the relay system described in Technology 5, when there is a relay node that has ceased operation, at least one of the remaining relay nodes that is in operation transmits a signal with a higher level to the terminal compared to when all of the relay nodes are in operation. This makes it possible to maintain the communication quality of terminals in a coverage area even if one or more relay nodes in the coverage area are put into a dormant state.

[0140] <Technology 7> In the relay system according to any one of the first to sixth techniques, the relay donor estimates the location of the terminal based on the signal strength or the reception time of a signal received from the terminal by each of the plurality of relay nodes. This allows the relay donor to estimate the location of the terminal.

[0141] <Technology 8> In the relay system described in Technology 7, the relay donor predicts the future location of the terminal based on the past locations of the terminal, and determines the relay node to operate based on the predicted future location of the terminal. This allows the relay donor to put into operation in advance relay nodes that cover areas where terminals are predicted to be present in the future, thereby enabling the communication quality of the terminals to be maintained.

[0142] <Technology 9> In the relay system described in any one of Techniques 1 to 8, the relay donor transmits a relay signal including a predetermined control signal and a signal from the base station to the relay node using the second frequency band, and the relay node determines a radio frequency in the first frequency band of a signal to be transmitted to the terminal based on the radio frequency of the control signal received from the relay donor and the radio frequency of the relay signal. This makes it possible to set with high accuracy the radio frequency in the first frequency band of the signal that the relay node transmits to the terminal.

[0143] <Technology 10> In the relay system described in any one of Techniques 1 to 8, the relay donor transmits a relay signal including a signal from a base station to the relay node using the second frequency band, the relay signal including a reference signal at a predetermined period, and the relay node determines a radio frequency in the first frequency band of a signal to be transmitted to the terminal based on the period of the reference signal included in the relay signal received from the relay donor. This makes it possible to set with high accuracy the radio frequency in the first frequency band of the signal that the relay node transmits to the terminal.

[0144] <Technology 11> As a relay method, a relay donor (10) and a base station (2) perform wireless communication using a first frequency band, the relay donor and a plurality of relay nodes (50) perform wireless communication using a second frequency band different from the first frequency band, and the plurality of relay nodes and at least one terminal (4) perform wireless communication using the first frequency band. As a result, a signal transmitted from a base station is transferred to multiple relay nodes via the relay donor, and is then transmitted to the terminal by the multiple relay nodes. Therefore, by appropriately arranging multiple relay nodes, it is possible to expand the coverage area (6) in which wireless communication with the base station is possible.

[0145] Although the embodiments have been described above with reference to the accompanying drawings, the present disclosure is not limited to such examples. It is clear that a person skilled in the art can conceive of various modifications, corrections, substitutions, additions, deletions, and equivalents within the scope of the claims, and it is understood that these also belong to the technical scope of the present disclosure. In addition, the components in the above-mentioned embodiments may be arbitrarily combined within the scope of the invention. [Industrial Applicability]

[0146] The techniques of this disclosure are useful for relaying signals in wireless communication systems. [Explanation of symbols]

[0147] 1. Communication Systems 2 base station 3. Relay System 4, 4A, 4B, 4C Terminal 6 Coverage Area 10 Relay Donor 20 First Communications Department 21 First Antenna 22 First transmitter / receiver 23 First intermediate frequency conversion section 30 2nd Communications Department 31 Second Antenna 32 Second transmitter / receiver 33 Second intermediate frequency conversion section 40 Control section 41 Storage section 42 Distribution synthesis section 50, 50A, 50B, 50C, 50D Relay nodes 60 3rd Communications Department 61 Third Antenna 62 Third Transmitter / Receiver 63 Third intermediate frequency conversion section 70 4th Communications Department 71 4th Antenna 72 4th Transmitter / Receiver 73 4th intermediate frequency conversion section 80 Control section 81 Storage section

Claims

1. a relay donor that wirelessly communicates with a base station using a first frequency band; a plurality of relay nodes that perform wireless communication with at least one terminal using the first frequency band; the relay donor performs wireless communication with the plurality of relay nodes using a second frequency band different from the first frequency band; Relay system.

2. The relay donor distributes the signal received from the base station to each of the plurality of relay nodes and transmits the distributed signal. The relay system according to claim 1 .

3. The relay donor combines the signals received from each of the plurality of relay nodes and transmits the combined signals to the base station. The relay system according to claim 1 .

4. the plurality of relay nodes are arranged such that a maximum delay time between signals received by the terminal from each of the plurality of relay nodes is equal to or less than a predetermined guard interval; The relay system according to claim 1 .

5. The relay node, in which the level of the signal received from the terminal is less than a predetermined threshold, suspends operation. The relay system according to claim 1 .

6. When there is a relay node that has been suspended, at least one of the remaining relay nodes that are in operation transmits a signal with a higher level to the terminal compared to a case in which all of the relay nodes are in operation. The relay system according to claim 5.

7. The relay donor estimates a location of the terminal based on a signal strength or a reception time of a signal received from the terminal by each of the plurality of relay nodes. The relay system according to claim 1 .

8. The relay donor is predicting a future location of the terminal based on a past location of the terminal; determining a relay node to be operated based on the predicted future location of the terminal; The relay system according to claim 7.

9. The relay donor transmits a relay signal including a predetermined control signal and a signal from the base station to the relay node using the second frequency band; The relay node determines a radio frequency in the first frequency band of a signal to be transmitted to the terminal based on a radio frequency of the control signal received from the relay donor and a radio frequency of the relay signal. The relay system according to claim 1 .

10. the relay donor transmits a relay signal including a signal from a base station to the relay node using the second frequency band, the relay signal including a reference signal at a predetermined period; The relay node determines a radio frequency in the first frequency band of a signal to be transmitted to the terminal based on a period of the reference signal included in the relay signal received from the relay donor. The relay system according to claim 1 .

11. The relay donor and the base station perform wireless communication using a first frequency band; the relay donor and the plurality of relay nodes perform wireless communication using a second frequency band different from the first frequency band; the plurality of relay nodes and at least one terminal perform wireless communication using the first frequency band; Relay method.

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