COMMUNICATION SYSTEM, CONTROL DEVICE, AND COMMUNICATION METHOD

Abstract

To properly process communication requests generated within relay stations that perform non-reproduction relaying by suppressing time delays.SOLUTION: A communication system includes a first communication station, a second communication station, a relay station that relays communication between the first and second communication stations without changing time slots of the communication by time division multiplexing, and a control device. In the case where a communication request occurs from within the relay station to the second communication station during relaying communication at the relay station, when the communication being relayed satisfies a first condition and communication by the communication request satisfies a second condition, the control device permits the relay station the communication by the communication request.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present disclosure relates to a communication system, a control device, and a communication method. [Background technology]

[0002] In wireless communication such as the 5th Generation Mobile Communication System (5G), ultra-low latency communication of sub-milliseconds is expected. On the other hand, from the viewpoint of improving communication services, it is desirable to expand the coverage area of ​​cells, and relay communication via relay stations is effective for this purpose. Meanwhile, as a relay technology with low latency, non-regenerative relay, which does not perform demodulation and decoding at the relay station, is desirable. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] 3GPP TS 38.174 V17.0.0(2022-03) [Non-Patent Document 2] 3GPP TS 38.106 V17.0.0(2022-03) Summary of the Invention [Problem to be solved by the invention]

[0004] However, even in a relay station where non-regenerative relay is performed, a communication request may occur within the relay station. For example, if data to be transmitted to a relay destination occurs within the relay station, the advantage of non-regenerative relay as a relay technology with little delay is reduced if non-regenerative relay is stopped and transmitted. On the other hand, if the relay station does not stop regenerative relay, it is desirable to be able to appropriately determine whether or not wireless communication resources for data transmission from the relay station to the relay destination can be secured in addition to wireless communication resources for non-regenerative relay. An aspect of the disclosed embodiment is to appropriately process a communication request generated within a relay station that performs non-regenerative relay while suppressing time delay. [Means for solving the problem]

[0005] One aspect of the disclosed embodiment is illustrated by a communication system, which includes a first communication station, a second communication station, a relay station that relays communication between the first communication station and the second communication station by time division multiplexing without changing a time slot of the communication, and a control device that, when a communication request to the second communication station is generated from within the relay station while relaying the communication, permits the relay station to communicate according to the communication request when the relayed communication satisfies a first condition and the communication according to the communication request satisfies a second condition. Effect of the Invention

[0006] According to this communication system, it is possible to appropriately process a communication request generated in a relay station that performs non-regenerative relay by suppressing a time delay. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram illustrating a communication system according to an embodiment. [Diagram 2] FIG. 2 is a diagram illustrating another example communication system included in an embodiment. [Diagram 3] FIG. 3 is a diagram illustrating a configuration of the relay station 3. As shown in FIG. [Figure 4] FIG. 4 is a diagram illustrating an example of a hardware configuration of the control device. [Diagram 5] FIG. 5 is a diagram illustrating an example of reception timing and reception power of a received wave when a transmission signal from a base station is received at a terminal station. [Figure 6] FIG. 6 is a diagram illustrating an example of a change in signal power accompanying the propagation of a relay wave and a superimposed wave. [Figure 7] FIG. 7 shows a process flow in this communication system. [Figure 8] FIG. 8 shows a process flow in this communication system. [Figure 9] FIG. 9 shows a process flow in this communication system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, a communication system, a control device, and a communication method according to an embodiment will be described with reference to the drawings. The communication system includes a first communication station, a second communication station, a relay station that relays communication between the first communication station and the second communication station without changing the time slot of the communication by time division multiplexing, and a control device. When a communication request to the second communication station occurs from within the relay station while relaying communication in the relay station, the control device permits the relay station to communicate by the communication request when the relayed communication satisfies a first condition and the communication by the communication request satisfies a second condition. In this communication system, the relay station can transmit data to a relay destination by a communication request generated within the relay station without stopping non-regenerative relay or while maintaining relaying without shifting the time slot of the relayed communication. In addition, the communication system can efficiently use wireless communication resources.

[0009] Here, the first communication station can be called a transmitting station. The second communication station can be called a receiving station. The first condition is a condition that the communication from the first communication station to the second communication station that is relayed is received at the second communication station that is the receiving station with a sufficient signal-to-interference-plus-noise ratio or higher. The second condition is a condition that the communication by the communication request at the relay station is received at the second communication station that is the receiving station with a sufficient power difference compared to the reception power of the communication from the first communication station to the second communication station. In this communication system, the first condition is required that the communication relayed at the relay station can be received at the receiving station with a predetermined communication quality. And the second condition is required that the transmission power at the relay station that can be used for the communication by the communication request, obtained by excluding the transmission power for relaying the communication from the maximum transmission power allowed for the relay station, is a positive value. Furthermore, as the second condition, it is required that there exists a modulation scheme and a coding rate that can be used for the signal-to-interference plus noise power ratio calculated for the received signal at the second communication station when the communication according to the communication request is performed with the transmission power of the positive value. If the first condition and the second condition are satisfied, the communication according to the communication request at the relay station is permitted.

[0010] <Embodiment> (System Configuration) FIG. 1 is a diagram illustrating a communication system 100A according to an embodiment. The communication system 100A includes a control device 1, a base station 2, a relay station 3, and a terminal station 4. The control device 1 is a device on a core network to which the base station 2 is connected. However, the control device 1 may be the core network itself, or may be a system included in the core network. The core network includes, for example, an optical fiber network. The control device 1 controls the base station 2, the relay station 3, and the terminal station 4, and provides communication services to the terminal station 4.

[0011] The base station 2 provides a wireless access network to the terminal station 4. An area where wireless communication is possible in the wireless access network is also called a cell. The base station 2 has one or more antennas (e.g., #0), a radio 21 connected to the one or more antennas, and a control circuit 22. The control circuit 22 has, for example, a processor and a memory. The processor controls communication with the control device 1 and wireless communication with the relay station 3 and the terminal station 4 using a computer program in the memory.

[0012] The terminal station 4 is also called a mobile station. The mobile station connects to a wireless access network within the range of a cell provided by the base station 2. Meanwhile, the relay station 3 relays wireless communication between the base station 2 and the terminal station 4. The relay station 3 includes a fixed station, which is installed at a fixed location, and a mobile station. obtain.

[0013] Like the base station 2, the relay station 3 has one or more antennas (for example, #0), radio devices 31 connected to each of the one or more antennas, and a control circuit 32. Note that the control circuit 32 may be connected to an antenna dedicated to the control circuit 32, independent of the antenna connected to the radio device 31.

[0014] The terminal station 4 has one or more antennas (for example, #0), a radio device 41 connected to each of the one or more antennas, and a control circuit 42. The relay station 3 may be equipped with an antenna. For example, the radio 41 may select an antenna with the highest reception signal level to receive the reception signal. Similarly, one radio 31 of the relay station 3 may be equipped with multiple antennas. A mobile station in a cell requests the base station 2 to connect to the radio access network, and the mobile station operates as a terminal station 4 by being connected. A mobile station in a cell may directly request the base station 2 to connect to the radio access network. A mobile station may also request the base station 2 to connect to the radio access network via a mobile station operating as a relay station 3 in a cell or a fixed station inside or outside the cell. The terminal station 4 can be said to be a station that can communicate with the base station 2 via one or more relay stations 3 or without any of the one or more relay stations 3. In the downlink channel, the first communication station can be the base station 2, and the second communication station can be said to be the terminal station 4. In the uplink channel, the first communication station can be the terminal station 4, and the second communication station can be said to be the base station 2.

[0015] FIG. 2 is a diagram illustrating a communication system 100B, which is another example included in this embodiment. Compared with the communication system 100A in FIG. 1, the communication system 100B has a central base station 2A and one or more distributed base stations 2B instead of the base station 2. When one or more distributed base stations 2B are individually distinguished, a branch number is assigned to each of them, such as distributed base stations 2B-1, . . . , 2B-K. Here, the branch number K is an integer indicating the number of distributed base stations. In FIG. 2, the distributed base stations 2B-1 and 2B-K are illustrated. However, when the distributed base stations 2B-1, . . . , 2B-K are collectively referred to, they are simply described as distributed base station 2B.

[0016] The central base station 2A has a control circuit 22A. Also, the distributed base station 2B has a radio 21B. The control circuit 22A of the central base station 2A and the radio 21B of the distributed base station 2B are connected, for example, by an optical fiber C1 or a wireless network. There is no limitation on the topology of the optical fiber C1 that connects the central base station 2A and the multiple distributed base stations 2B. For example, the topology of the optical fiber C1 may be a one-to-one connection between nodes, a network that branches as it moves away from the central base station 2A, a star network, a ring network, or the like. Also, when connecting the control circuit 22A of the central base station 2A and the radio 21B of the distributed base station 2B by a wireless network, there is no limitation on the standard and protocol of the wireless network.

[0017] The control circuit 22A has a processor and a memory, similar to the control circuit 22 in Fig. 1. The processor controls communication with the control device 1 and wireless communication with the relay station 3 and the terminal station 4 by a computer program on the memory. That is, the control circuit 22A controls wireless communication with the relay station 3 and the terminal station 4 via the radio 21B of one or more distributed base stations 2B. In the downlink channel, the first communication station can be said to be the central base station 2A and the distributed base station 2B, and the second communication station can be said to be the terminal station 4. In the uplink channel, the first communication station can be said to be the terminal station 4, and the second communication station can be said to be the central base station 2A and the distributed base station 2B.

[0018] 3 is a diagram illustrating a configuration of the relay station 3. The relay station 3 includes a radio device 31 and a control circuit 32. The radio device 31 of the relay station 3 includes a transmitter 311, a receiver 312, and a baseband circuit. The circulator 314 has a first port, a second port, and a circulator 313. The transmitter 311 and the receiver 312 are connected to an antenna (#0) via the circulator 314. That is, the transmitter 311, the receiver 312, and the antenna (#0) are connected to three ports of the circulator 314. A transmission signal from the transmitter 311 is input to, for example, the first port of the circulator 314, and is transmitted from the second port to the antenna (#0). A reception signal received by the antenna (#0) is input to the second port of the circulator 314, and is transmitted to the receiver 312 from the third port.

[0019] Here, the power difference between the transmission signal and the reception signal is, for example, about 100 dB. On the other hand, the isolation of the circulator 314 is about 30 dB, and a part of the transmission signal causes self-interference with the reception signal. This self-interference is generated by the Radio Frequency (RF) analog in the receiver 312. This is suppressed by using the filter in combination with the FIR filter 319 in the baseband circuit 313.

[0020] The receiver 312 receives a reception signal from an antenna (#0) via a circulator 314. The receiver 312 has a quadrature detection circuit and an analog-to-digital (AD) converter. The receiver 312 down-converts the reception signal by quadrature detection, and further converts it into digital data by an AD converter to obtain a baseband signal. The receiver 312 outputs the obtained baseband signal to a baseband circuit 313.

[0021] The baseband circuit 313 includes an FIR filter 319, a signal generation circuit 315, amplitude adjustment circuits 316 and 317, and an adder circuit 318. The FIR filter 319 suppresses a transmission signal that is mixed into the received signal and causes self-interference. The amplitude adjustment circuit 316 adjusts the amplitude of the received signal with a baseband waveform filtered by the FIR filter 319. This received signal with a baseband waveform can be called a relayed signal. The relayed signal is added to the superimposed signal from the signal generation circuit 315 by the adder circuit 318, and then converted to an analog signal by an analog-to-digital (DA) converter in the transmitter 311, converted to a high-frequency signal, and amplified by a power amplifier. Here, the relationship between the amplitude value of the baseband waveform (for example, a sequence of complex numbers represented by signed integer values) input to the DA converter in the transmitter 311 and the power value of the high-frequency signal is known. For example, if the gain of the power amplifier is known and the isolation of the isolator is fixed as in the configuration of Figure 3, the relationship between the baseband waveform and the power value of the high-frequency signal can be measured by the receiver. Therefore, the amplitude adjustment circuit 316 adjusts the amplitude of the repeater signal of the baseband waveform, so that the baseband circuit 313 adjusts the transmission power (P R、BS Therefore, the amplitude adjustment circuit 316 outputs the repeater signal having the amplitude-adjusted baseband waveform to the addition circuit 318.

[0022] In response to a command from the control circuit 32, the signal generation circuit 315 generates a superimposed signal of a baseband waveform for transmitting a communication request generated in the relay station 3, i.e., data to be transmitted from the relay station to the relay destination. The amplitude adjustment circuit 317 adjusts the amplitude of the superimposed signal of a baseband waveform generated by the signal generation circuit 315. The superimposed signal is mixed with the relayed signal in the addition circuit 318, then converted into an analog signal by the DA converter of the transmitter 311, converted into a high-frequency signal, and amplified by the power amplifier. As described above, the relationship between the amplitude value of the DA converter in the transmitter 311 and the power value of the high-frequency signal is known. Therefore, by the amplitude adjustment circuit 317 adjusting the amplitude of the superimposed signal of a baseband waveform, the baseband circuit 313 can adjust the high-frequency transmission power (P R、RTherefore, the amplitude adjustment circuit 316 outputs an amplitude-adjusted superimposed signal of a baseband waveform to the addition circuit 318.

[0023] The adder circuit 318 is, for example, a circuit that adds 16-bit signed integers, and adds the signal values ​​of the baseband waveform expressed by the real and imaginary parts of a complex number. The relay station 3 digitally adds and synthesizes the two signals (relayed signal and superimposed signal) to be transmitted. The relay station 3 synthesizes the relayed signal whose amplitude has been adjusted in the baseband waveform and the superimposed signal whose amplitude has been adjusted in the baseband waveform, and outputs the synthesized signal to the transmitter 311. The transmitter 311 converts the synthesized signal in the baseband waveform into analog data using a DA converter, and performs frequency conversion (up-conversion) of the synthesized signal in a modulation circuit. The transmitter 311 uses this to modulate a high-frequency carrier wave, amplifies the modulated high-frequency signal using a power amplifier, and transmits it from the antenna. The amplitudes of the relayed signal and the superimposed signal are adjusted in the baseband waveform. Also, as described above, the relationship between the amplitude value of the DA converter and the power value of the high-frequency signal is known. Therefore, the relay station 3 adjusts the amplitude of the baseband waveform for the relay signal and the superimposed signal, thereby reducing the power P of the relayed signal transmitted from the antenna. R、BS and the power of the superimposed signal P R、R can be controlled.

[0024] The transmitter 311 has a digital-to-analog (DA) converter and a modulation circuit. The transmitter 311 converts a received signal from the baseband circuit 313 into an analog signal, and generates a high-frequency signal by the modulation circuit. The high-frequency signal is a signal obtained by modulating a high-frequency carrier wave with a composite signal from the addition circuit 318. The transmitter 311 then transmits the high-frequency signal as a relay signal from the antenna (#0) via the circulator 314.

[0025] The control circuit 32 controls the relay station 3 and provides the function of the relay station 3. The control circuit 32 controls, for example, communication between the control device 1, the base station 2, and the terminal station 4. For example, the control circuit 32 calculates a propagation delay τ UE->R and propagation characteristic HUE->R The control circuit 32 also sets the settings of the FIR filter 319 and the control parameters of the amplitude adjustment circuits 316, 317, etc. Furthermore, when a communication request occurs in the relay station 3 to a receiving station (the terminal station 4 in the downlink channel, and the base station 2 in the uplink channel), the control circuit 32 inquires of the control device 1 whether or not to accept the communication request.

[0026] FIG. 4 is a diagram illustrating an example of the hardware configuration of the control device 1. The control device 1 has a CPU 11, a main memory device 12, and external devices, and executes communication processing and information processing by computer programs. The CPU 11 is also called a processor. The CPU 11 is not limited to a single processor, and may be configured as a multiprocessor. The CPU 11 may also include a Graphics Processing Unit (GPU), a Digital Signal Processor (DSP), etc. The CPU 11 may also include a Field Programmable Gate Array (FPGA), etc. The external device may be linked to a hardware circuit of the above. The external device may be an external storage device 13, an output device 14, an operation device 15, and a communication device 16.

[0027] The CPU 11 executes a computer program that has been loaded in an executable manner into the main memory device 12, and provides processing for the control device 1. The main memory device 12 stores the computer program executed by the CPU 11, data processed by the CPU 11, etc. The main memory device 12 is a dynamic random access memory (DRAM), a static random access memory (SRAM), a read only memory (ROM), etc. Furthermore, the external memory device 13 is, for example, the main memory device 1 The external storage device 13 is used as a storage area supporting the CPU 2 and stores computer programs executed by the CPU 11, data processed by the CPU 11, etc. The external storage device 13 is a hard disk drive, a solid state drive (SSD), etc. The control device 1 further includes a removable storage medium A drive of the body may be connected to the removable storage medium, for example, a Blu-ray disc, a Digital Versatile Disc (DVD), a Compact Disc (CD), a flash memory card, etc.

[0028] The output device 14 is, for example, a display device such as a liquid crystal display or an electroluminescence panel. However, the output device 14 may also include a speaker or other device for outputting sound. The operation device 15 is, for example, a touch panel in which a touch sensor is superimposed on a display. The communication device 16 is, for example, a device that connects the base station 2 to the Internet or the like via optical fiber. The communication device 16 communicates with an external network. The communication device 16 is, for example, a gateway connected to the base station 2 and a gateway that communicates with an external network such as the Internet. The communication device 16 may be a single device or a combination of multiple devices.

[0029] (signal power) FIG. 5 is a diagram illustrating the reception timing and reception power of a received wave when a transmission signal from a base station 2 as a transmitting station is received by a terminal station 4 as a receiving station. In FIG. 5, the horizontal axis is, for example, the time it takes for a signal emitted from the base station 2 to reach the terminal station 4. The vertical axis is the power of the signal received by the terminal station 4. Three black circles illustrate symbols transmitted in a single time slot in a signal. Of the three black circles, one is an example of a symbol of a direct signal transmitted by a direct wave that directly reaches the terminal station 4 from the base station 2. The second is an example of a symbol of a relayed signal transmitted by a relay wave relayed by the relay station 3. The third is a symbol of a signal corresponding to a transmission request (data) generated in the relay station 3. In this embodiment, the signal corresponding to the transmission request generated in the relay station 3 is called a superimposed signal. The high frequency modulated by the superimposed signal is called a superimposed wave. Each of these symbols is received by the terminal station 4 in the section Tcp of the cyclic prefix after being emitted from the base station 2.

[0030] In the example of Figure 5, the direct wave is τ BS->UEThe relay wave arrives at the terminal station 4 from the base station 2 with a propagation delay of τ BS->R The relay wave arrives at the relay station 3 from the base station 2 with a propagation delay of τ R The signal is non-regeneratively repeated at relay station 3 with a processing delay time of ΔR and then emitted from relay station 3. The relayed wave arrives at terminal station 4 from relay station 3 with a propagation delay of ΔR. The superimposed wave carrying the data signal (superimposed signal) generated within relay station 3 also arrives at terminal station 4 from relay station 3 with a propagation delay of ΔR.

[0031] The control device 1 determines the power of each signal at the time of reception so that the terminal station 4, which is the receiving station of the downlink channel, can separate the signals of the direct wave, the relayed signal of the relayed wave, and the received wave including the superimposed signal of the superimposed wave. The control device 1 then determines the transmission power at the base station 2 and the transmission power at the relay station 3 so that the determined reception powers of the direct wave, relay wave, and superimposed wave are obtained. The control device 1 also determines the transmission power for each of the relay wave and the superimposed wave at the relay station 3. The control device 1 then notifies the base station 2 and the relay station 3 of the determined transmission power. These transmission powers are calculated from the target reception power at the receiving station (terminal station 4) and the propagation loss of the path between the transmitting station (base station 2) and the receiving station (terminal station 4).

[0032] The base station 2 transmits a transmission wave with the notified transmission power. The relay station 3 transmits a relay wave and a superimposed wave with the notified transmission power for each of the relay wave carrying the relayed signal and the carrier wave carrying the superimposed signal. Note that FIG. 5 illustrates a downlink channel signal transmitted from the base station 2 to the terminal station 4. However, the control device 1 processes an uplink channel signal from the terminal station 4 to the base station 2 in the same manner. That is, the control device 1 controls so that the determined reception power of the direct wave, relay wave, and superimposed wave is obtained at the receiving station (base station 2). That is, the control device 1 determines the transmission power at the transmitting station (terminal station 4) and the transmission power at the relay station 3. Also, the control device 1 determines the transmission power for each of the relay wave and the superimposed wave at the relay station 3. Then, the control device 1 notifies the determined transmission power to the terminal station 4 and the relay station 3. These transmission powers are calculated from the target reception power at the receiving station (base station 2) and the propagation loss of the path between the transmitting station (terminal station 4) and the receiving station (base station 2).

[0033] FIG. 6 is a diagram illustrating the change in signal power accompanying the propagation of a relay wave and a superimposed wave. In FIG. 6, the transmission power P BS The attenuation of the transmitted signal due to propagation loss L R->BS The base station 2 receives the reference signal of the control channel transmitted from the relay station 3 through the propagation path of the control channel. R->BS In FIG. 6, the loss of the propagation path from the base station 2 to the relay station 3 is measured as the attenuation L R->BS The signal that arrives at the relay station 3 is non-regeneratively relayed, and the transmission power P R,BS The transmitted signal is attenuated by the propagation loss, L UE->R At this time, the received SINR at the receiving station (terminal station 4) is BS->R->UE On the other hand, the transmission power of the superimposed wave on the relay wave at relay station 3 is P R,R The transmission power of the relay wave (relayed signal) and the superimposed wave (superimposed signal) is subject to the following conditions (Equation 1) to (Equation 5).

[0034] First, the received SINR of the relay wave is required to be equal to or greater than the SINR value required by the modulation scheme and coding rate (MCS) of the received signal. Here, the SINR value required by the MCS of the received signal is defined as S BS->UE Then, the following (Equation 1) is required.

[0035]

number

[0036]

number

[0037]

number

[0038] Therefore, the transmission power of the superimposed wave that satisfies (Equation 3) is PR,R must be a positive value. Here, the transmission power P R,R The superimposed wave transmitted from relay station 3 is attenuated by L UE->R The signal reaches the receiving side (terminal station 4) through the propagation path, and the SINR of the received signal is Γ R->UE As shown in FIG. 6, the SINR of the received signal of the superimposed wave (superimposed signal) is Γ, which is the SINR at the receiving station (e.g., terminal station 4) of the relayed wave (relayed signal). BS->R->UE The second condition is the SINR of the superimposed signal, i.e., Γ R->UE That is, the received SINR required by the available MCS is S R->UE Then, (Equation 4) is required.

[0039]

number

[0040]

number

[0041] In Fig. 6, the conditions of (Equation 2) and (Equation 5) are exemplified as the conditions for the reception SINR of terminal station 4, which is the receiving station. The control device 1 determines whether or not to generate a superimposed signal in relay station 3, depending on whether or not the conditions of (Equation 2) and (Equation 5) illustrated in Fig. 6 are satisfied. Furthermore, when the conditions of (Equation 2) and (Equation 5) are satisfied, the control device 1 determines the MCS of the superimposed wave and the transmission power of the superimposed wave. Note that, although the transmitting station is base station 2 and the receiving station is terminal station 4 in Fig. 6, the same applies if the transmitting station is terminal station 4 and the receiving station is base station 2.

[0042] Here, the base station 2 which is a transmitting station in the downlink channel is an example of a first communication station. Also, the terminal station 4 which is a receiving station in the downlink channel is an example of a second communication station. Also, the terminal station 4 which is a transmitting station in the uplink channel is an example of a first communication station. Also, the base station 2 which is a receiving station in the uplink channel is an example of a second communication station.

[0043] (Processing flow) 7 to 9 show processing flows in the communication system 100. The processing flows in Fig. 7 to 9 are repeated for each radio frame. Here, the processing flows are explained assuming that the base station 2 is a transmitting station (first communication station) and the terminal station 4 is a receiving station (second communication station). First, the terminal station 4 and the relay station 3 transmit a reference signal to the base station 2 on an uplink control channel (S71, S72).

[0044] The relay station 3 receives a reference signal such as a control channel from the terminal station 4 to the base station 2, and transmits the control channel signal with a propagation delay τ UE->R and propagation characteristic H UE->R Furthermore, the relay station 3 notifies the control device 1 of the desire for signal superposition and the measured H UE->R The relay station 3 notifies the control device 1 of the propagation characteristic H from the reference signal of the control channel transmitted from the relay station 3 (S76, S77). Here, the request for signal superposition is transmitted from the relay station 3 to the control device 1 when a request for transmitting data to the terminal station 4, which is the receiving station (relayed station), occurs in the relay station 3. The base station 2 obtains the propagation characteristic H R->BSand notifies the control device 1 (S78). FIG. 7 is continued in FIG. 8 with A1, B1, and C1. The explanation will be continued below with FIG. 8. Note that D1 in FIG. 7 is continued in FIG.

[0045] The control device 1 is H UE->R and H R->BS Based on this, the control device 1 judges whether or not the signal can be superimposed at the relay station 3. UE->R and H R->BS From the attenuation amount L in each section UE->R and L R->BS Calculate the attenuation L UE->R corresponds to the propagation path between the terminal station 4 and the relay station 3. R->BS corresponds to the propagation path between the relay station 3 and the base station 2. The control device 1 then calculates the attenuation amount L UE->R and L R->BS Therefore, the received SINR (signal to interference noise) of the relayed signal at the terminal station 4 is sound power ratio)Γ BS->R->UE is calculated (S81).

[0046] The control device 1 then calculates the received SINR Γ at the terminal station 4 for the signal transmitted from the base station 2. BS->R->UE However, the SINR value S required for the MCS in communication between the base station 2 and the terminal station 4 is BS->UE If the determination in S82 is YES, the control device 1 determines whether the desired transmission power P R,BS At this time, the control device 1 calculates the margin M BS->UE (see Equation 2). That is, the control device 1 sets the desired SINR in the terminal station 4 as S BS->UE + M BS->UE It is also possible to use the following.

[0047] Next, the control device 1 calculates the maximum transmission power P R,max and the transmission power of the relay wave P R,BS From the above, the available transmission power P R,R =10 log 10(10^(P R,max / 10)-10^(P R,BS Calculate P R,R When is positive, the control device 1 sets the transmission power P R,R The received SINR at terminal station 4 when the superimposed wave is transmitted from relay station 3 is Γ R->UE (S83). Then, the control device 1 calculates the received SINR Γ R->UE In other words, the control device 1 determines whether there is an MCS that can be used for communication with the relay station 3 (S84). R,max The transmission power for relaying communication from R,BS The transmission power P available at the relay station 3 for communication based on the communication request obtained by excluding R,R Then, the transmission power P R,R is positive, and the received SINR of the superimposed signal at the terminal station 4 is R->UE It is determined whether there is a modulation scheme and coding rate (MCS) that can be used for communication.

[0048] If the determination in S84 is NO, the control device 1 does not permit the relay station 3 to perform superimposition. Therefore, the control device 1 notifies the relay station 3 via the base station 2 that superimposition is not permitted (S85, S86). Next, FIG. 8 continues to FIG. 9 with A2, B2, and C2. Note that D1 in FIG. 7 continues to FIG. 9. Below, the explanation continues with FIG. 9. If superimposition is not permitted (NO in S91), the relay station 3 non-regeneratively repeats the relayed signal without the superimposed signal (S92).

[0049] On the other hand, if the determination in S84 is YES, the control device 1 allows the relay station 3 to superimpose the superimposed wave on the relay wave. Here, the desired SINR of the MCS is S R->UE (see Equation 4), the control device 1 has a margin M R->UE may be added to the desired SINR for the determination (see equation 5). If it is determined that superimposition is permitted, the control device 1 notifies the relay station 3 and the terminal station 4 of the MCS of the superimposed wave to be superimposed on the relay wave at the relay station 3 from the base station 2 via the control channel together with the superimposition permission (S93, S94). In addition, the control device 1 determines the transmission power PR,BS and the transmission power P of the superimposed wave R,R is notified from the base station 2 to the relay station 3 via a control channel (S95, S96).

[0050] Relay station 3, which has been granted permission to superimpose, transmits the signal with an average power of P R,BS The relay station 3 sets the amplitude of the baseband signal waveform after passing through the FIR filter so that the average power of the superimposed signal is P R,R The amplitude of the baseband signal is adjusted so that: The relay station 3 adds the relay wave and the superimposed wave to a signal having a baseband waveform, converts it to a high-frequency signal, and transmits it (S97). As a result, the relay station 3 transmits the superimposed wave and non-regeneratively repeats the relay wave.

[0051] The terminal station 4 receives data from each station using a process such as successive interference cancellation to separate various superimposed signals (S98).

[0052] (Effects of the embodiment) In this embodiment, the relay station 3 repeats a transmission signal from the base station 2 (or the terminal station 4) which is a transmitting station without changing the time slot of the communication by time division multiplexing. Then, when a request occurs in the relay station 3 to transmit data to the terminal station 4 (or the base station 2) which is a receiving station (relayed station), the relay station 3 determines the request for signal superposition and the propagation characteristic H between the relay station 3 and the receiving station (for example, the terminal station 4) measured by the relay station 3. UE->R The control device 1 is notified of the propagation characteristic H R->BS The control device 1 then measures the received SINR Γ at the receiving station (terminal station 4) for a signal transmitted from a transmitting station (for example, base station 2) as a first condition. BS->R->UE However, the SINR value S required by the MCS in communication between the transmitting station (base station 2) and the receiving station (terminal station 4) is BS->UE Alternatively, the control device 1 determines whether the transmission power PR,BS Next, the control device 1 determines the maximum transmission power P R,max and the transmission power of the relay wave P R,BS From the above, the available transmission power P R,R =10 log 10 (10^(P R,max / 10)-10^(P R,BS / 10)) and the available transmission power P R,R is positive, and the received SINR of the superimposed signal at the terminal station 4 is R->UE If there is a communicable MCS that satisfies the above, the control device 1 permits the relay station 3 to superimpose the superimposed wave onto the relayed wave. The control device 1 then notifies the relay station 3 and the terminal station 4 of the MCS of the superimposed wave to be superimposed onto the relayed wave at the relay station 3, together with the superimposition permission. The control device 1 also determines the transmission power P R,BS and P R,R The relay station 3 is notified of this.

[0053] Therefore, the control device 1 first adjusts the transmission power P of the relay wave at the relay station 3 so that the relay wave can be received by the receiving station (for example, the terminal station 4) by non-regenerative relay. R,BS This is the first condition. Next, the control device 1 determines the maximum transmission power P R,max and the transmission power of the relay wave P R,BS The available transmission power P for transmitting the superimposed signal from R,R =10 log 10 (10^(P R,max / 10)-10^(P R,BS Then, the control device 1 calculates the transmission power P available for transmitting the superimposed signal. R,R The received SINR at the receiving station (terminal station 4) of the superimposed wave transmitted from relay station 3 is Γ R->UEThe control device 1 determines whether there is a modulation scheme and coding rate (MCS) that can be used for communication in the above-mentioned manner. As a result, the relay station 3 can, for example, give sufficient power to the superimposed wave so that the superimposed wave can be separated from the relayed wave, and then superimpose it on the relayed wave and transmit the superimposed wave in response to a transmission request generated by the relay station 3. The above-mentioned determination by the control device 1 and superimposition of the superimposed wave on the relayed wave by the relay station 3 are performed during the repetition of radio frames. In other words, the relay station 3 can perform non-regenerative relay and superimposition of the superimposed wave on the relayed wave, as long as the time slot of the relayed wave is not shifted.

[0054] At this time, as described above, the control device 1 calculates the reception SINR Γ at the terminal station 4 for the relay wave relayed by the relay station 3. BS->R->UE However, the SINR value S required for the MCS in communication between the base station 2 and the terminal station 4 is BS->UE Therefore, the control device 1 can permit the relay station 3 to superimpose the superimposed wave to the extent that the transmission signal from the base station 2 (or terminal station 4) which is the transmitting station can be relayed by the relay station 3 and received by the terminal station 4 (or base station 2) which is the receiving station by non-regenerative relay.

[0055] In addition, the control device 1 determines the transmission power P available for transmitting the superimposed signal for the superimposed wave superimposed at the relay station 3. R,R is positive, and the received SINR of the superimposed signal at the terminal station 4 is R->UE If there is a communicable MCS that satisfies the above, the control device 1 allows the relay station 3 to superimpose the superimposed wave onto the relayed wave. Therefore, the control device 1 can allow the relay station 3 to superimpose the superimposed wave to the extent that the superimposed wave can be received by the terminal station 4 (or base station 2), which is the receiving station.

[0056] At this time, the control device 1 also notifies the relay station 3 of the transmission power available for the superimposed wave. Since the control device 1 notifies the relay station 3, the relay station 3 can transmit the superimposed wave with appropriate power under the control of the control device 1. At this time, the control device 1 also notifies the relay station 3 and the terminal station 4 (or base station 2), which is the receiving station, of a communicable MCS that satisfies the received SINR of the superimposed signal at the terminal station 4. Therefore, the relay station 3 and the receiving station can receive the relay wave and the superimposed wave with a difference in received power that allows the relay wave and the superimposed wave to be separated at the receiving station.

[0057] <Other embodiments> In the above embodiment, the processing of the communication system 100 has been described with the base station 2 as the transmitting station and the terminal station 4 as the receiving station. However, the processing of the communication system 100 is similar with the terminal station 4 as the transmitting station and the base station 2 as the receiving station. That is, the control device 1 requests that the reception SINR of the relay wave in the base station 2, which is the receiving station, be equal to or greater than the SINR value required by the MCS of the received signal. Now, the SINR value required by the MCS is expressed as S UE->BS Then, the transmission power P R,R and the transmission power of the relay wave P R,BS The sum of these is the maximum transmission power P R,max Therefore, the formula (3) is required. This is the same as the above embodiment. Furthermore, the superimposed signal is attenuated by the amount of attenuation L R->BS It is required that there exists an MCS that can be used for communication at the SINR of the signal received at the receiving side (base station 2) via the propagation path of the signal. Therefore, even when the terminal station 4 is the transmitting station and the base station 2 is the receiving station, the same conditions as those in (Formula 1) to (Formula 5) in the embodiment are required. However, when the terminal station 4 is the transmitting station and the base station 2 is the receiving station, the BS and UE in the subscripts in (Formula 1) to (Formula 5) are switched.

[0058] 8 with respect to the received SINR of the relayed wave and the received SINR of the superimposed signal, with the receiving station being the base station 2. Then, in a similar determination as in S84, if the control device 1 permits the relay station 3 to superimpose, it may notify the relay station 3 via the base station 2 and the relay station 3 of the MCS of the superimposed signal to be superimposed on the relay signal from the relay station 3, in a similar procedure to S93. The control device 1 also determines the transmission power P R,BS and P R,R may be notified from the base station 2 to the relay station 3 via a control channel.

[0059] When the relay station 3 has multiple antennas, the relay station 3 can change the transmission timing for each antenna to obtain a diversity effect. However, the relay station 3 ensures that the arrival time at the receiving station (e.g., terminal station 4) does not exceed the cyclic prefix length, which is the allowable propagation delay. In other words, the relay station 3 transmits the relay signal and the signal superimposed on the relay signal from multiple antennas so that the time slots of the received signal received from the transmitting station (e.g., base station 2) do not shift for the relay signal and the signal superimposed on the relay signal.

[0060] In the above embodiment, the processes described as being performed by one device may be shared and executed by multiple devices. Alternatively, the processes described as being performed by different devices may be executed by one device. In a computer system, the hardware configuration (server configuration) by which each function is realized can be flexibly changed.

[0061] In the above embodiment, the control device 1 is a device on a core network to which the base station 2 is connected. Alternatively, the control device 1 is the core network itself, or a system included in the core network. However, the control device 1 is not limited to such a device on a core network. For example, the control device 1 may be a device included in the base station 2. For example, the control device 1 may be a device that communicates with the relay station 3 or the terminal station 4 through the wireless device 21 within the base station 2. In that case, in the processes of Figures 7 to 9, the control device 1 and the base station 2 may execute the processes as an integrated device. Therefore, the processes described in the two series of sequences of A1, B1, A2, B2, A3, B3 can be executed as one series. This will be a good sequence.

[0062] The present disclosure can also be realized by supplying a computer program implementing the functions described in the above embodiments to a computer, and having one or more processors of the computer read and execute the program. Such a computer program may be provided to the computer by a non-transitory computer-readable storage medium connectable to the system bus of the computer, or may be provided to the computer via a network. The non-transitory computer-readable storage medium includes any type of medium suitable for storing electronic instructions, such as, for example, a magnetic disk (e.g., a floppy disk, a hard disk drive (HDD), etc.), an optical disk (e.g., a CD-ROM, a DVD disk, a Blu-ray disk, etc.), a read-only memory (ROM), a random access memory (RAM), an EPROM, an EEPROM, a magnetic card, a flash memory, or an optical card. [Explanation of symbols]

[0063] 1 Control device 2 base station 2A central base station 2B distributed base station 3. Relay Station 4 Terminal Station 11 CPU 12 Main storage 13 External storage device 16 Communication equipment 21, 21B, 31, 41 Radio 22, 22A, 32, 42 Control circuit 311 Transmitter 312 Receiver 313 Baseband Circuit 314 Circulator 315 Signal generation circuit 316, 317 Amplitude adjustment circuit 318 Addition Circuit 319 FIR Filters

Claims

1. a first communication station; a second communication station; a relay station that relays communication between the first communication station and the second communication station by time division multiplexing without changing a time slot of the communication; a control device that, when a communication request to the second communication station is generated from within the relay station while the relay station is relaying the communication, permits the relay station to communicate based on the communication request when the relayed communication satisfies a first condition and the communication based on the communication request satisfies a second condition.

2. 2. The communication system according to claim 1, wherein the first condition is that, in the relayed communication, a signal-to-interference plus noise power ratio of a received signal at the second communication station is equal to or greater than a signal-to-interference plus noise power ratio required for a modulation method and a coding rate of the received signal.

3. 2. The communication system according to claim 1, wherein the second condition is that a transmission power at the relay station available for communication based on the communication request, obtained by subtracting the transmission power of the communication to be relayed from the maximum transmission power allowed for the relay station, is a positive value, and that a modulation scheme and a coding rate that can be used for the communication based on the communication request exist based on a signal-to-interference-plus-noise power ratio calculated for a received signal at the second communication station.

4. The communication system according to claim 3 , wherein the control device notifies the relay station of transmission power available for communication in response to the communication request that satisfies the second condition.

5. The communication system according to claim 3 , wherein the control device notifies the relay station and the second communication station of the modulation scheme and the coding rate that satisfy the second condition.

6. The communication system according to claim 1 , wherein the control device is included in the first communication station or the second communication station.

7. a first communication station; a second communication station; a relay station that relays communication between the first communication station and the second communication station by time division multiplexing without changing a time slot of the communication, a control device that, when a communication request to the second communication station is generated from within the relay station while the relay station is relaying the communication, permits the relay station to communicate based on the communication request if the relayed communication satisfies a first condition and the communication based on the communication request satisfies a second condition.

8. The control device according to claim 7, wherein the first condition is that in the relayed communication, a signal-to-interference plus noise power ratio of the received signal at the second communication station is equal to or greater than a signal-to-interference plus noise power ratio required for a modulation method and coding rate of the received signal.

9. 8. The control device according to claim 7, wherein the second condition is that a transmission power at the relay station available for communication according to the communication request, obtained by subtracting a transmission power of the communication to be relayed from a maximum transmission power allowed for the relay station, is a positive value, and that a modulation scheme and a coding rate that can be used for the communication according to the communication request exist based on a signal-to-interference plus noise power ratio calculated for a received signal at the second communication station.

10. The relay station determines the transmission power available for communication based on the communication request that satisfies the second condition. The control device according to claim 9, wherein the control device notifies the

11. The control device according to claim 9 , wherein the control device notifies the relay station and the second communication station of the modulation scheme and the coding rate that satisfy the second condition.

12. The control device according to claim 7 , which is included in the first communication station or the second communication station.

13. a first communication station; a second communication station; a relay station that relays communication between the first communication station and the second communication station by time division multiplexing without changing a time slot of the communication; and a control device that controls the relay station, a communication method in which, when a communication request to a second communication station is generated from within the relay station while the relay station is relaying the communication, the relay station is permitted to communicate based on the communication request if the relayed communication satisfies a first condition and the communication based on the communication request satisfies a second condition.

14. The communication method according to claim 13, wherein the first condition is that, in the relayed communication, a signal-to-interference plus noise power ratio of a received signal at the second communication station is equal to or greater than a signal-to-interference plus noise power ratio required for a modulation scheme and a coding rate of the received signal.

15. 14. The communication method according to claim 13, wherein the second condition is that a transmission power at the relay station available for communication according to the communication request, obtained by subtracting a transmission power of the communication to be relayed from a maximum transmission power allowed for the relay station, is a positive value, and that a modulation scheme and a coding rate that can be used for the communication according to the communication request exist based on a signal-to-interference plus noise power ratio calculated for a received signal at the second communication station.

16. The communication method according to claim 15 , wherein the control device notifies the relay station of transmission power available for communication in response to the communication request that satisfies the second condition.

17. The communication method according to claim 15 , wherein the control device notifies the relay station and the second communication station of the modulation scheme and the coding rate that satisfy the second condition.

18. The communication method according to claim 13 , wherein the control device is included in the first communication station or the second communication station.

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