JP6532832B2 - Communication system, communication method and communication apparatus - Google Patents

Description

  The present invention relates to a communication system, a communication method, and a communication apparatus.

  In recent years, with the diversification of wireless communication services, mobile communication terminals such as smartphones performing wireless communication using various wireless communication methods and base stations such as access points of wireless LAN (Local Area Network) have been increasing. For example, in a wireless communication system using signals which are radio waves of the same modulation scheme in the same frequency band, with an increase in the number of communication devices such as mobile communication terminals and base stations, each communication device performs Signal (hereinafter also referred to as communication signal) and signals from other communication devices (hereinafter also referred to as interference signal). As a result, in each communication device, the probability of occurrence of interference between the communication signal and the interference signal increases, and the frequency utilization efficiency is degraded.

  Therefore, some non-orthogonal multiple access (NOMA) systems use SPC (superposition coding) and SIC (successive interference canceller).

  For example, by using the SIC, the communication apparatus sequentially demodulates from the received signal indicating the maximum received power, and removes the interference signal from the received signal when the demodulated signal is an interference signal. A technique for demodulating communication signals has been proposed (see, for example, Non-Patent Document 1).

  FIG. 7 shows an example of NOMA wireless communication using SPC and SIC.

  As shown in FIG. 7, for example, the communication devices Ta and Tb respectively transmit signals 1 and 2 which are communication signals to the communication device Ra in the same modulation method as the communication device Ta. The communication device Ra receives the signals 1 and 2 and demodulates the signal with the highest received power. For example, if the power of signal 1 is greater than the power of signal 2, the communication device Ra demodulates signal 1 with the highest received power. Then, the communication device Ra demodulates the signal 2 whose received power is smaller than the signal 1. In this case, the communication device Ra generates a replica signal of the signal 1 in the wireless section using the demodulated signal 1 based on the SIC technology, and removes the signal 1 by subtracting the replica signal from the received signal. The communication device Ra demodulates the received signal from which the signal 1 is removed (that is, the signal 2), and ends the reception process. When three or more signals are superimposed, the communication device Ra demodulates the signal by repeatedly executing the SIC technique.

  In addition, in communication standards such as IEEE 802.11ac, a MU-MIMO technique has also been proposed in which wireless communication is performed between a base station having a plurality of antennas and a plurality of mobile communication terminals having at least one antenna. In addition, IEEE is an abbreviation for Institute of Electrical and Electronics Engineers, and MU-MIMO is an abbreviation for Multi User Multi-Input Multi-Output.

  FIG. 8 illustrates an example of MU-MIMO wireless communication.

  As shown in FIG. 8, for example, the communication device Rc such as a base station transmits the signals 3 and 4 including data to the communication device Rc to the communication device Rc such as a mobile communication terminal at time t1. And a synchronization signal including information indicating transmission timing to each of the communication devices Tc and Td. Then, the communication devices Tc and Td start transmission of the signals 3 and 4 at time t3 of the transmission timing indicated by the synchronization signal. The communication device Rc receives and demodulates each of the signals 3 and 4 simultaneously. Time t2 indicates the time at which the communication devices Tc and Td have completed reception of the synchronization signal, and time t4 and t5 indicate the times at which the communication devices Tc and Td have completed transmission of the signals 3 and 4, respectively.

Souvik Sen et al., “Successive interference cancellation: a back-of-the-envelope perspective”, 9th ACM SIGCOMM Workshop on Hot Topics in Networks, Article No. 17, 2010

  The communication device Ra illustrated in FIG. 7 can not demodulate the signal 2 smaller than the reception power of the signal 1 when the signal 1 having a large reception power can not be demodulated. That is, in NOMA wireless communication, the probability of successful transmission of a signal with low received power is lower than the probability of successful transmission of a signal with high received power. Therefore, in an environment where a plurality of signals having the same received power exist, the signal may not be demodulated, and the throughput may be reduced.

  Further, in the MU-MIMO wireless communication illustrated in FIG. 8, the communication device Rc transmits, to the communication devices Tc and Td, a synchronization signal for controlling the timing of transmission, and the communication devices Tc and Td receive the synchronization signal. Signals 3 and 4 are transmitted to the communication device Rc at the timing of transmission indicated by the synchronization signal. Therefore, in the MU-MIMO wireless communication, the communication devices Tc and Td transmit signals 3 and 4 during a period (synchronization signal transmission time) from time t1 to time t2 when the communication device Rc is transmitting a synchronization signal. There is a blank period in which data is not transmitted / received from the time t2 to the time t3 until the start (transmission standby time). That is, in MU-MIMO wireless communication, it may be difficult to improve the overall system throughput by having a blank period.

  An object of the present invention is to provide a communication system, a communication method, and a communication apparatus capable of improving the throughput of the entire system.

A first invention relates to a communication system including a first communication device and a plurality of second communication devices, wherein the first communication device has a plurality of antennas, and a first communication method or MU-MIMO communication which is a NOMA communication method. In the first communication unit that executes communication with each of the plurality of second communication devices based on the second communication method that is the method, and the total number of antennas included in the plurality of second communication devices is less than a predetermined threshold value In this case, the first communication method is selected as a common communication method for each of the plurality of second communication devices, and the second communication method is selected when the total number of antennas included in the plurality of second communication devices is equal to or greater than the threshold. select a common communication method to each of a plurality of second communication apparatuses, and a control unit for notifying the communication method selected in each of the plurality of second communication apparatuses, each of the plurality of the second communication device, at least One antenna and the first pass Based on the notified communication method from the device, obtain Preparations and a second communication unit for executing communication with the first communication device.

A second invention is a communication system having a first communication device and a plurality of second communication devices , wherein the first communication device has a plurality of antennas, and a first communication method or MU-MIMO communication which is a NOMA communication method. In the first communication unit that executes communication with each of the plurality of second communication devices based on the second communication method that is the method, and the total number of antennas included in the plurality of second communication devices is less than a predetermined threshold value In the case where the first communication method is selected as the communication method common to each of the plurality of second communication devices, and the total number of antennas included in the plurality of second communication devices is equal to or more than the threshold, If the total number of antennas in the plurality of second communication devices is less than the number of antennas in the first communication device, the total number of antennas in the communication device is compared with the number of antennas in the first communication device. Second communication method Select each of the second communication device having a common communication system, the total number of antenna having a plurality of second communication apparatuses, in the case of more than the number of antennas with the first communication apparatus includes a first communication scheme A control unit that selects a third communication method combining the second communication method as a common communication method for each of the plurality of second communication devices, and notifies the selected communication method to each of the plurality of second communication devices Each of the plurality of second communication devices includes at least one antenna and a second communication unit that executes communication with the first communication device based on the communication scheme notified from the first communication device .

A third invention is a communication method in a communication system having a first communication device and a plurality of second communication devices, wherein the first communication device is a NOMA communication method or a first communication method or MU-MIMO communication. A communication step of executing communication with each of a plurality of second communication devices using a plurality of antennas and a total number of antennas included in the plurality of second communication devices are predetermined based on a second communication method which is a method If it is less than the threshold, the first communication scheme is selected as the communication scheme common to each of the plurality of second communication devices, and if the total number of antennas included in the plurality of second communication devices is equal to or more than the threshold, the second communication method is selected as a common communication method to each of a plurality of second communication devices, it performs a control step of notifying the communication method selected in each of the plurality of the second communication device.

The communication apparatus of the fourth invention executes communication with each of the plurality of terminal devices based on the plurality of antennas and the first communication scheme which is the NOMA communication scheme or the second communication scheme which is the MU-MIMO communication scheme. If the total number of antennas included in the communication unit and the plurality of terminal devices is less than a predetermined threshold, the first communication method is selected as a common communication method for each of the plurality of terminal devices, and the plurality of terminal devices are selected. And a control unit which selects the second communication method as a common communication method for each of the plurality of terminal devices and notifies each of the plurality of terminal devices of the selected communication method when the total number of antennas possessed by is greater than or equal to the threshold. obtain Bei the.

  The present invention can improve the throughput of the entire system.

FIG. 1 illustrates an embodiment of a wireless communication system. It is a figure which shows an example of the relationship between the total of the antenna of the user terminal in the radio | wireless communications system shown in FIG. 1, and the through-put of the radio | wireless communications system for every communication system. It is a figure which shows an example of the setting process in the base station shown in FIG. FIG. 7 illustrates another embodiment of a wireless communication system. It is a figure which shows an example of the relationship between the total of the antenna of the user terminal in the radio | wireless communications system shown in FIG. 4, and the through-put of the radio | wireless communications system for every communication system. It is a figure which shows an example of the setting process in the base station shown in FIG. It is a figure which shows an example of the wireless communication using SPC and SIC. It is a figure which shows an example of the radio | wireless communication of MU-MIMO.

  Hereinafter, embodiments will be described using the drawings.

  FIG. 1 illustrates one embodiment of a wireless communication system.

  The radio communication system SYS shown in FIG. 1 has a base station AP and n user terminals UT (UT1-UTn). The base station AP is an example of a first communication device, and the user terminal UT is an example of a second communication device.

  The user terminal UT is a mobile communication terminal such as a smart phone or a tablet type terminal, and based on the communication method selected by the base station AP, the signal sig (sig (1) -sig (n) with the base station AP. Send and receive Each of the user terminals UT1 to UTn transmits a signal sig with the same frequency and the same communication scheme. Also, each of the user terminals UT1-UTn may transmit with the same transmission power as each other, and may transmit the signal sig with different transmission powers from each other.

  The user terminal UT1 has an antenna ANT, a communication unit 10 and a control unit 20. User terminal UT2-UTn has the same elements as user terminal UT1. The user terminal UT may also have a plurality of antennas ANT.

  The communication unit 10 transmits and receives a signal sig (1) to and from the base station AP via the antenna ANT based on the NOMA or MU-MIMO communication scheme selected by the base station AP. For example, the communication unit 10 receives, from the base station AP, a signal sig (1) of a data signal including data addressed to the user terminal UT1. In addition, the communication unit 10 may be a control signal including information indicating the communication method selected by the base station AP, or a control signal (ACK (Acknowledgement)) indicating that the demodulation of the signal sig (1) in the base station AP is successful. Signal (1) is received from the base station AP. Then, the communication unit 10 outputs the signal sig (1) of the received data signal and control signal to the control unit 20.

  Further, the communication unit 10 transmits the signal sig (1) to the base station AP with the transmission power instructed by the control unit 20 in the communication system selected by the base station AP. Note that the communication unit 10 re-transmits the signal sig (1) when transmission of the signal sig (1) fails (that is, the ACK signal is not received from the base station AP) due to a collision due to interference between the signals sig. Send.

  The transmission power at which the communication unit 10 transmits the signal sig (1) may be randomly designated by the control unit 20 executing predetermined random number processing, or may be fixed to a predetermined power in advance. Alternatively, the communication unit 10 may transmit the signal sig (1) with the transmission power with the smallest collision rate.

  The control unit 20 is a processor or the like, and controls each element of the user terminal UT1 by executing a program stored in a storage unit such as a memory included in the user terminal UT1. For example, when the control unit 20 receives a control signal including information on the communication scheme selected by the base station AP, the control unit 20 sets the communication scheme of the received control signal in the communication unit 10.

  If the control unit 20 fails to transmit the signal sig (1) (that is, does not receive an ACK signal from the base station AP) due to a collision due to interference between the signals sig, the communication unit 10 transmits a signal during a predetermined period. Based on the number of times sig (1) has been retransmitted, the collision rate of the signal sig (1) (ie, the rate of retransmissions) is calculated. Then, the control unit 20 generates a control signal including the calculated collision rate of the signal sig (1) as the signal sig (1), and the communication unit 10 generates the signal sig (1) of the generated control signal as a base station. Send to AP.

  The base station AP is an access point or the like, and includes m antennas AT (AT1-ATm), a communication unit 40, a monitoring unit 50, a control unit 60, and a storage unit 70.

  The communication unit 40 transmits / receives a signal sig to / from each user terminal UT via m antennas AT based on, for example, the NOMA or MU-MIMO communication scheme selected by the control unit 60. The communication unit 40 outputs the received signal sig to the monitoring unit 50.

  For example, the communication unit 40 performs demodulation processing based on the communication scheme selected by the control unit 60 on the received signal sig. For example, when the communication method is set to NOMA, the communication unit 40 measures the received power of the received signal sig, and demodulates the signal sig using SIC. Further, when the communication scheme is set to MU-MIMO, the communication unit 40 demodulates each of the simultaneously received signals sig. Then, the communication unit 40 outputs the demodulated signal sig to the monitoring unit 50.

  On the other hand, when the communication unit 40 receives data addressed to the user terminal UT from the outside through the interface included in the base station AP, the communication unit 40 modulates the received data based on the communication method set by the control unit 60. To generate a signal sig of the data signal. Further, when the communication unit 40 receives a control instruction for the user terminal UT from the control unit 50, the communication unit 40 modulates the received control instruction based on the set communication method, and generates a signal sig of the control signal. Then, the communication unit 40 transmits the generated signal sig to the user terminal UT via the m antennas AT.

  The monitoring unit 50 executes, for example, measurement of the reception power of the signal sig received by the communication unit 40, determination as to whether or not demodulation of the signal sig in the communication unit 40 has succeeded, and so on. Monitor communications. The monitoring unit 50 also measures the amount of data included in the signal sig exchanged in communication with each user terminal UT. Then, the monitoring unit 50 outputs the monitoring result to the control unit 60. Also, when the signal sig is a data signal, the monitoring unit 50 transmits the data demodulated by the communication unit 40 to an external transmission destination via the interface of the base station AP, and when the signal sig is a control signal, The control signal demodulated by the communication unit 40 is output to the control unit 60.

  The control unit 60 is, for example, a processor, and controls each element of the base station AP by executing a program stored in the storage unit 70 such as a memory. For example, based on the monitoring result received from the monitoring unit 50, the control unit 60 determines whether a collision due to interference between the signals sig has occurred. Then, when determining that a collision has occurred, the control unit 60 calculates, for each user terminal UT, a demodulation failure rate due to the collision between the signals sig. Then, the control unit 60 stores, for example, the calculated demodulation failure rate for each user terminal UT in the storage unit 70. Further, when the demodulation of the signal sig is successful, the control unit 60 generates a control signal (ACK signal) indicating the success of the demodulation, and transmits an ACK signal to the user terminal UT that has transmitted the signal sig via the communication unit 40. Send.

  When the control unit 60 receives a control signal including a collision rate in the user terminal UT from the signal sig transmitted by the user terminal UT, the control unit 60 stores the received collision rate in the storage unit 70 for each user terminal UT.

  Furthermore, based on the monitoring result by the monitoring unit 50, the control unit 60 selects either NOMA or MU-MIMO as the communication method with n user terminals UT, and sets the selected communication method in the communication unit 40. . Then, the control unit 60 generates a control signal of the selected communication scheme, and transmits the signal sig of the control signal through the communication unit 40 to notify each of the n user terminals UT of the selected communication scheme. Do.

  When the selected communication scheme is MU-MIMO, control unit 60 generates a synchronization signal including information indicating MU-MIMO as a control signal, and transmits the generated synchronization signal to each of user terminals UT. Good. As a result, the base station AP does not transmit the signal sig of the control signal for setting MU-MIMO to the user terminal UT and the synchronization signal for transmitting the signal sig by MU-MIMO. That is, the base station AP can set MU-MIMO to the user terminal UT with one synchronization signal, and transmit the signal sig to the user terminal UT.

  The storage unit 70 is a memory, a hard disk drive or the like, and stores information such as a demodulation failure rate for each user terminal UT and a collision rate of the signal sig together with a program executed by the control unit 60.

  FIG. 2 shows an example of the relationship between the total number of antennas ANT of user terminals UT in the wireless communication system SYS shown in FIG. 1 and the throughput of the wireless communication system SYS for each communication method. The horizontal axis of FIG. 2 shows the total number of antennas ANT of all user terminals UT, and the vertical axis of FIG. 2 shows throughput. Moreover, in FIG. 2, the throughput in case a communication system is NOMA is shown by a continuous line, and the throughput in the case of MU-MIMO is shown by a broken line.

  As shown in FIG. 2, in NOMA, the total number of antennas ANT increases to increase the number of signals to be transmitted, thereby increasing the throughput of the wireless communication system SYS. However, in NOMA, as the number of signals sig increases, the collision rate of signals sig also increases. For this reason, the throughput in NOMA is maximized and saturated when the total number of antennas ANT is a predetermined number N, and decreases as the total number of antennas ANT is larger than the predetermined number N. The predetermined number N is determined according to the number of transmission powers used for transmission of the signal sig and the number of signals sig that can be transmitted by one transmission power.

  On the other hand, in MU-MIMO, when the total number of antennas ANT is smaller than the total number m of antennas AT of the base station AP, the throughput of the wireless communication system SYS increases. In MU-MIMO, the base station AP can not simultaneously transmit and receive signals sig of the total number m or more of the antennas AT of the base station AP. Therefore, when the total number of antennas ANT is equal to or more than the total number m of antennas AT of the base station AP, the throughput of MU-MIMO becomes a constant value.

  In addition, when the total number of antennas ANT is smaller than the value k, the throughput of MU-MIMO is smaller than the throughput of NOMA because it has the blank period of the synchronization signal transmission time and the transmission waiting time shown in FIG. The value k indicates the total number of antennas ANT when the throughput of NOMA and the throughput of MU-MIMO become equal. The synchronization signal transmission time and transmission waiting time shown in FIG. 8 are constant regardless of the total number of antennas ANT of the user terminal UT. For this reason, when the total number of antennas ANT is equal to or more than the value k, the throughput of MU-MIMO becomes larger than the throughput of NOMA by increasing the number of signals sig that can be transmitted simultaneously.

  That is, in FIG. 2, in order to improve the throughput of the wireless communication system SYS, the control unit 60 of the base station AP selects an appropriate communication scheme according to the total number of antennas ANT of all user terminals UT to communicate. Show that it is important to do.

  FIG. 3 shows an example of setting processing in the base station AP shown in FIG. In addition, in starting the process shown in FIG. 3, the control part 60 selects either NOMA or MU-MIMO, and sets the selected communication system to the communication part 40 and the user terminal UT.

  In step S100, control unit 60 uses NOMA and MU-MIMO using the monitoring result of monitoring unit 50, the collision rate acquired from each of user terminals UT, and the demodulation failure rate of signal sig of user terminal UT. Each throughput in the communication method is calculated. For example, the control unit 60 calculates the throughput Tp (NOMA) in NOMA in the predetermined period T, using Expression (1).

なお、ＤＡ（ｓｉｇ（ｉ））は、信号ｓｉｇ（ｉ）に含まれるデータのデータ量を示す。ＲＡｃ（ＵＴｉ）は、ユーザ端末ＵＴｉが送信する信号ｓｉｇ（ｉ）の衝突率を示す。ＲＡｆ（ＵＴｉ）は、ユーザ端末ＵＴｉからの信号ｓｉｇ（ｉ）の復調失敗率を示す。また、所定の期間Ｔは、任意に設定されもよく、無線通信システムＳＹＳに要求される通信品質等に応じて設定されてもよい。

DA (sig (i)) indicates the data amount of data included in the signal sig (i). RAc (UTi) indicates the collision rate of the signal sig (i) transmitted by the user terminal UTi. RAf (UTi) indicates the demodulation failure rate of the signal sig (i) from the user terminal UTi. The predetermined period T may be set arbitrarily, or may be set according to the communication quality and the like required of the wireless communication system SYS.

  Further, the control unit 60 calculates throughput Tp (MU-MIMO) of MU-MIMO using Expression (2).

なお、Ｔｓは、同期信号送信時間（例えば、図８に示した時刻ｔ１から時刻ｔ２までの時間）を示す。Ｔｔは、送信待機時間（例えば、図８に示した時刻ｔ１から時刻ｔ２までの時間）を示す。Ｔｍａｘは、同時に送信される信号ｓｉｇのうち、最も送信に時間がかかった（すなわち、データ量が最も大きい）信号ｓｉｇの送信時間、例えば図８に示した時刻ｔ３から時刻ｔ５までの時間を示す。

Ts indicates a synchronization signal transmission time (for example, the time from time t1 to time t2 shown in FIG. 8). Tt indicates a transmission standby time (for example, the time from time t1 to time t2 shown in FIG. 8). Tmax represents the transmission time of the signal sig which took the longest time to be transmitted (that is, the largest amount of data) among the simultaneously transmitted signals sig, for example, the time from time t3 to time t5 shown in FIG. .

  In step S110, the control unit 60 determines whether the NOMA throughput Tp (NOMA) calculated in step S100 is larger than the MU-MIMO throughput Tp (MU-MIMO). If the throughput Tp (NOMA) is larger than the throughput Tp (MU-MIMO), the control unit 60 selects NOMA as the communication scheme. In this case, the process of the base station AP proceeds to step S120. On the other hand, when the throughput Tp (NOMA) is equal to or less than the throughput Tp (MU-MIMO), the control unit 60 selects MU-MIMO as the communication scheme. In this case, the process of the base station AP proceeds to step S130.

  In step S120, the control unit 60 sets, for the communication unit 40, the communication method of NOMA selected in step S110. Then, the base station AP ends the setting process.

  In step S130, the control unit 60 sets, for the communication unit 40, the MU-MIMO communication scheme selected in step S110. Then, the base station AP ends the setting process.

  The base station AP repeatedly executes the processing from step S100 to step S130 at predetermined time intervals. Alternatively, when starting communication with a new user terminal UT, the base station AP may execute the processing from step S100 to step S130.

  In addition, in step S100, the control unit 60 may calculate a value k such that the throughput Tp (NOMA) and the throughput Tp (MU-MIMO) become equal instead of calculating the throughput Tp. Then, in step S110, the control unit 60 may determine whether the total number of antennas ANT of all user terminals UT is smaller than the value k. That is, when the total number of antennas ANT is smaller than the value k, the control unit 60 may select NOMA, and the process of the base station AP may shift to step S120. Further, when the total number of antennas ANT is equal to or larger than the value k, the control unit 60 may select MU-MIMO, and the process of the base station AP may shift to step S130.

  As described above, in the embodiment illustrated in FIGS. 1 to 3, the control unit 60 calculates the throughputs of the wireless communication system SYS in NOMA and MU-MIMO. The control unit 60 selects the communication scheme by comparing the calculated NOMA throughput with the MU-MIMO throughput. That is, the control unit 60 calculates the throughput of the wireless communication system SYS in NOMA and MU-MIMO, and determines the communication method that can obtain the largest throughput at the time of calculation, thereby improving the throughput of the entire system. it can.

  FIG. 4 shows another embodiment of a wireless communication system. Elements having the same or similar functions as the elements described in FIG. 1 are assigned the same or similar reference numerals, and detailed descriptions thereof will be omitted.

  The radio communication system SYS2 shown in FIG. 4 has a base station AP2 and n user terminals UT.

  The base station AP2 is an access point or the like, and includes m antennas AT, a communication unit 40, a monitoring unit 50, a control unit 60a, and a storage unit 70.

  The control unit 60a is, for example, a processor or the like, and controls each element of the base station AP2 by executing a program stored in the storage unit 70. Similar to the control unit 60 shown in FIG. 1, the control unit 60 a determines whether a collision due to interference between the signals sig has occurred based on the monitoring result received from the monitoring unit 50. Then, when determining that a collision has occurred, the control unit 60a calculates, for each user terminal UT, a demodulation failure rate due to the collision between the signals sig. The control unit 60a also calculates a demodulation failure rate for each user terminal UT in the MU-MIMO communication system. The control unit 60a stores the calculated demodulation failure rate for each user terminal UT in the storage unit 70. Further, when the demodulation of the signal sig is successful, the control unit 60a generates an ACK signal, and transmits the ACK signal to the user terminal UT that has transmitted the signal sig through the communication unit 40.

  When the control unit 60a receives a control signal including a collision rate in the user terminal UT from the signal sig transmitted by the user terminal UT, the control unit 60a stores the received collision rate in the storage unit 70 for each user terminal UT.

  Furthermore, based on the monitoring result by the monitoring unit 50, the control unit 60a performs third communication in which NOMA, MU-MIMO, and NOMA and MU-MIMO are combined as a communication scheme with each of n user terminals UT. Select one of the methods. The control unit 60a sets the selected communication method in the communication unit 40. Further, the control unit 60a generates a control signal of the selected communication scheme, and transmits the signal sig of the control signal to the n user terminals UT through the communication unit 40.

  When the selected communication scheme is MU-MIMO or the third communication scheme, control unit 60a generates a synchronization signal including information indicating MU-MIMO or the third communication scheme as a control signal, and generates the generated synchronization signal. It may be transmitted to each of the user terminals UT. Thereby, the base station AP2 transmits a control signal for setting the MU-MIMO or the third communication method to the user terminal UT, and a signal of a synchronization signal for transmitting the signal sig in the MU-MIMO or the third communication method. There is no need to send each sig. That is, the base station AP2 can set the MU-MIMO or the third communication scheme in the user terminal UT with one synchronization signal, and can cause the user terminal UT to transmit the signal sig.

  In the third communication scheme combining NOMA and MU-MIMO, the control unit 60a groups each of n user terminals UT based on the transmission power used for transmitting the signal sig in the case of NOMA. For example, when the transmission power in NOMA is three different transmission powers PW1, PW2, and PW3 (for example, PW1> PW2> PW3), the control unit 60a selects the third communication method, the transmission power PW1. The n user terminals UT are distributed to any of the group to be transmitted, the group to be transmitted by the transmission power PW2, and the group to be transmitted by the transmission power PW3. The control unit 60a may randomly distribute the user terminals UT to each of the three groups, or may distribute the user terminals UT such that the number of user terminals UT included in each of the three groups is equal. . Alternatively, the control unit 60a first distributes the user terminals UT to one group, and distributes the user terminals UT to another group if the number of distributed user terminals UT reaches a predetermined number of terminals. It is also good.

  Then, the control unit 60a transmits, to each of the user terminals UT, a control signal including information indicating the selected third communication method and the distributed group (that is, transmission power). The control unit 20 of each user terminal UT sets the third communication scheme and the transmission power in the communication unit 10 based on the information included in the received control signal. When the communication unit 10 of each user terminal UT receives a synchronization signal from the base station AP2, similarly to MU-MIMO, the communication unit 10 of the signal sig at the transmission timing indicated by the received synchronization signal and with the set transmission power. It transmits simultaneously to the base station AP.

  That is, in the third communication scheme, the signals sig transmitted by the user terminals UT of the same transmission power group are superimposed on each other with the same power and received by the base station AP2, as in the MU-MIMO. Further, in the third communication scheme, the signals sig of the user terminals UT between groups having different transmission powers are superimposed on different powers and received by the base station AP2, as in NOMA. Then, the communication unit 40 of the base station AP2 is, for example, a superimposed signal in which the signals sig of each group are superimposed in the order of highest received power (that is, in each group having the highest transmission power) based on the NOMA demodulation method. Take out. Then, the communication unit 40 extracts each of the signals sig from the superimposed signal of each group based on the MU-MIMO demodulation scheme.

  FIG. 5 shows an example of the relationship between the total number of antennas ANT of the user terminal UT in the wireless communication system SYS2 shown in FIG. 4 and the throughput of the wireless communication system SYS2 for each communication method. The horizontal axis of FIG. 5 shows the total number of antennas ANT of all user terminals UT, and the vertical axis of FIG. 5 shows throughput. Further, in FIG. 5, the throughput when the communication method is NOMA is indicated by a solid line, the throughput when MU-MIMO is indicated by a broken line, and the throughput when the communication method is a third communication method is indicated by a dotted line. Note that the throughput of NOMA and the throughput of MU-MIMO shown in FIG. 5 are the same as those shown in FIG.

  As shown in FIG. 5, in the third communication scheme, the number of signals sig increases as the total number of antennas ANT increases, so the throughput of the wireless communication system SYS2 increases. However, in the third communication method, as in the case of NOMA, the collision rate of the signal sig also increases as the number of the signal sig increases. Also, the third communication scheme has synchronization signal transmission time and transmission waiting time, as in MU-MIMO. Therefore, the throughput of the third communication scheme is smaller than the throughputs of NOMA and MU-MIMO when the total number of antennas ANT is small.

  On the other hand, in the third communication scheme, the signals sig of the user terminals UT between the groups having different transmission powers overlap with each other at different powers, as in NOMA. Therefore, the throughput of the third communication scheme does not reach a ceiling like the throughput of MU-MIMO even when the total number of antennas ANT is equal to or more than the total number m of antennas AT of base station AP, and the total number of antennas ANT increases. It can be increased according to

  FIG. 6 shows an example of setting processing in the base station AP2 shown in FIG. When starting the process shown in FIG. 6, control unit 60a selects one of NOMA, MU-MIMO or the third communication method, and sets the selected communication method in communication unit 40 and user terminal UT. ing. Further, among the processes of the steps shown in FIG. 6, those showing the same or similar processes as the steps shown in FIG. 3 have the same step numbers, and the detailed description will be omitted.

  In step S105, the control unit 60a performs NOMA, MU-MIMO, and NO using the monitoring result of the monitoring unit 50, the collision rate obtained from each of the user terminals UT, and the demodulation failure rate of the signal sig of the user terminal UT. The throughputs in the third communication method are respectively calculated. For example, the control unit 60a calculates the throughput Tp (NOMA) of NOMA using equation (1), and calculates the throughput Tp (MU-MIMO) of MU-MIMO using equation (2). Further, the control unit 60a calculates the throughput Tp (third communication method) of the third communication method using Expression (3).

なお、Ｒｆ（ＭＵ−ＭＩＭＯ）は、通信方式がＭＵ−ＭＩＭＯの場合の復調失敗率を示す。

Rf (MU-MIMO) indicates a demodulation failure rate when the communication scheme is MU-MIMO.

  After executing step S105, the base station AP2 executes the processes of steps S110 and S120. If the throughput Tp (NOMA) is less than or equal to the throughput Tp (MU-MIMO) in step S110, the processing of the base station AP2 proceeds to step S140.

  In step S140, the control unit 60a determines whether the throughput Tp (MU-MIMO) of MU-MIMO calculated in step S105 is larger than the throughput Tp (third communication method) of the third communication method. When the throughput Tp (MU-MIMO) is larger than the throughput Tp (third communication method), the control unit 60a selects MU-MIMO as the communication method. In this case, the process of the base station AP2 proceeds to step S130. Then, the base station AP2 executes the process of step S130.

  On the other hand, when the throughput Tp (MU-MIMO) is equal to or less than the throughput Tp (third communication method), the control unit 60a selects the third communication method as the communication method. In this case, the process of the base station AP2 proceeds to step S150.

  In step S150, the control unit 60a sets, for the communication unit 40, the communication method of the third communication method selected in step S140. Then, the base station AP2 ends the setting process.

  The base station AP2 repeatedly executes the processing from step S105 to step S150 at predetermined time intervals. Alternatively, when starting communication with a new user terminal UT, the base station AP2 may execute the processing from step S105 to step S150.

  In addition, in step S105, the control unit 60a may calculate a value k in which the throughput Tp (NOMA) and the throughput Tp (MU-MIMO) become equal instead of calculating the throughput Tp. Then, in step S110, the control unit 60a may determine whether the total number of antennas ANT of all user terminals UT is smaller than the value k. That is, when the total number of antennas ANT is smaller than the value k, the control unit 60a may select NOMA, and the process of the base station AP2 may shift to step S120. When the total number of antennas ANT is equal to or larger than the value k, the control unit 60a may select MU-MIMO, and the process of the base station AP2 may move to step S140.

  In addition, in step S140, the control unit 60a may determine whether the total number of antennas ANT of all user terminals UT is smaller than the total number m of antennas AT of the base station AP2 instead of the throughput Tp. That is, when the total number of antennas ANT is smaller than the total number m of antennas AT of the base station AP2, the control unit 60a may select MU-MIMO, and the processing of the base station AP2 may shift to step S130. When the total number of antennas ANT is equal to or more than the total number m of antennas AT of the base station AP2, the control unit 60a may select the third communication scheme, and the process of the base station AP2 may shift to step S150.

  As described above, in the embodiments illustrated in FIGS. 4 to 6, the control unit 60a calculates the throughputs of the wireless communication system SYS2 in the NOMA, MU-MIMO, and the third communication scheme. The control unit 60a selects the communication scheme by comparing the calculated throughputs of the NOMA, MU-MIMO, and the third communication scheme with one another. That is, the control unit 60a can improve the throughput of the entire system by calculating the throughput of the wireless communication system SYS2 in each communication method and determining the communication method that can obtain the maximum throughput at the time of calculation.

  Also, by using the third communication method combining NOMA and MU-MIMO, the wireless communication system SYS2 can achieve throughput in MU-MIMO even when the total number of antennas ANT is equal to or greater than the total number m of antennas AT of the base station AP. It is possible to avoid a headshot. Thereby, the radio communication system SYS2 can improve the throughput as the total number of antennas ANT increases.

  The features and advantages of the embodiments will be apparent from the foregoing detailed description. This is intended to cover the features and advantages of the embodiments as described above without departing from the spirit and scope of the claims. Also, all modifications and variations should be readily apparent to those skilled in the art. Accordingly, there is no intention to limit the scope of the embodiments having the invention to those described above, and it is also possible to rely on appropriate modifications and equivalents included in the scope disclosed in the embodiments.

1, 2, sig (1)-sig (n) ... signal; 10, 40 ... communication unit; 20, 60, 60a ... control unit; 50 ... monitoring unit; 70 ... storage unit; ANT, AT 1-ATm ... antenna AP, AP2: base station; Ra, Rc, Ta, Tb, Tc, Td: communication device; SYS, SYS2: wireless communication system; UT1-UTn: user terminal

Claims (4)

In a communication system having a first communication device and a plurality of second communication devices,
The first communication device is
With multiple antennas,
A first communication unit that executes communication with each of the plurality of second communication devices based on a first communication method that is a NOMA communication method or a second communication method that is a MU-MIMO communication method ;
If the total number of antennas included in the plurality of second communication devices is less than a predetermined threshold, the first communication method is selected as a common communication method for each of the plurality of second communication devices, If the total number of antennas included in the second communication device is equal to or greater than the threshold value, the second communication method is selected as a common communication method for each of the plurality of second communication devices, and the plurality of selected communication methods are selected. A controller for notifying each of the second communication devices of
Each of the plurality of second communication devices is
With at least one antenna,
Communication system the first on the basis of the notified communication method from the communication device, and wherein the obtaining Bei and a second communication unit for performing communication with the first communication device. In a communication system having a first communication device and a plurality of second communication devices ,
The first communication device is
With multiple antennas,
A first communication unit that executes communication with each of the plurality of second communication devices based on a first communication method that is a NOMA communication method or a second communication method that is a MU-MIMO communication method;
If the total number of antennas included in the plurality of second communication devices is less than a predetermined threshold, the first communication method is selected as a common communication method for each of the plurality of second communication devices, If the total number of antennas possessed by the second communication device is equal to or greater than the threshold value, the total number of antennas possessed by the plurality of second communication devices is further compared with the number of antennas possessed by the first communication device, If the total number of antennas included in the second communication device is less than the number of antennas included in the first communication device, the second communication method is selected as a common communication method for each of the plurality of second communication devices. and the total number of antennas by the plurality of second communication device included in the in the case of more than the number of antennas the first communication device has the third communication a combination of the second communication scheme from the first communication scheme the system Serial selected as a common communication method to each of a plurality of second communication apparatuses, and a control unit for notifying the communication method selected in each of the plurality of second communication device
Equipped with
Each of the plurality of second communication devices is
With at least one antenna,
A second communication unit that executes communication with the first communication device based on the communication method notified from the first communication device;
Communication system comprising: a. A communication method in a communication system having a first communication device and a plurality of second communication devices, the communication method comprising:
The first communication device is
A communication step of executing communication with each of the plurality of second communication devices using a plurality of antennas based on a first communication method which is a NOMA communication method or a second communication method which is a MU-MIMO communication method ;
If the total number of antennas included in the plurality of second communication devices is less than a predetermined threshold, the first communication method is selected as a common communication method for each of the plurality of second communication devices, If the total number of antennas included in the second communication device is equal to or greater than the threshold value, the second communication method is selected as a common communication method for each of the plurality of second communication devices, and the plurality of selected communication methods are selected. the second communication method for a control step of notifying each of the communication device, wherein the you execute the. With multiple antennas,
A communication unit that executes communication with each of a plurality of terminal devices based on a first communication scheme that is a NOMA communication scheme or a second communication scheme that is a MU-MIMO communication scheme ;
If the total number of antennas included in the plurality of terminal devices is less than a predetermined threshold, the first communication method is selected as a common communication method for each of the plurality of terminal devices, and the plurality of terminal devices When the total number of antennas included is equal to or more than the threshold value, the second communication method is selected as a common communication method for each of the plurality of terminal devices, and the selected communication method is notified to each of the plurality of terminal devices communication apparatus characterized by obtaining Bei and a control unit.

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