CN105704079A

CN105704079A - Physical layer network coding (PLNC)-based combined subcarrier suppression and relay selection method in bidirectional orthogonal frequency division multiplexing (OFDM) multi-relay system

Info

Publication number: CN105704079A
Application number: CN201610006171.4A
Authority: CN
Inventors: 许魁; 马文峰; 谢威; 吴连国; 徐友云
Original assignee: PLA University of Science and Technology
Current assignee: PLA University of Science and Technology
Priority date: 2016-01-04
Filing date: 2016-01-04
Publication date: 2016-06-22
Anticipated expiration: 2036-01-04
Also published as: CN105704079B

Abstract

The invention discloses a joint subcarrier suppression and relay selection method in a PLNC-based two-way OFDM multi-relay system, and proposes two joint subcarrier suppression and relay selection methods: joint subcarrier suppression and relay selection with a fixed suppression threshold A relay selection method and a joint subcarrier suppression and relay selection method with a fixed number of subcarriers. The joint subcarrier suppression and relay selection method with a fixed suppression threshold uses a fixed suppression threshold for subcarrier suppression in a two-way information exchange process; the joint subcarrier suppression and relay selection method with a fixed number of subcarriers performs a two-way information exchange During the process, the number of suppressed subcarriers is kept constant, that is, the number of active subcarriers is constant and the suppression threshold changes dynamically. Simulation results show that, compared with traditional subcarrier suppression, the two joint subcarrier suppression and relay selection methods proposed by the present invention not only enhance system reliability, but also improve system effectiveness.

Description

Joint Subcarrier Suppression and Relay Selection Method in Bidirectional OFDM Multi-Relay System Based on PLNC

技术领域technical field

本发明属于无线通信技术领域，涉及双向无线多中继系统的高效传输技术，为一种基于PLNC的双向OFDM多中继系统中的高效传输技术，尤其涉及一种基于PLNC的双向OFDM多中继系统中的联合子载波抑制与中继选择方法。The invention belongs to the technical field of wireless communication, relates to a high-efficiency transmission technology of a two-way wireless multi-relay system, is a high-efficiency transmission technology in a PLNC-based two-way OFDM multi-relay system, and particularly relates to a PLNC-based two-way OFDM multi-relay system Joint subcarrier suppression and relay selection method in the system.

背景技术Background technique

随着移动互联网的蓬勃发展，移动通信对高速数据传输的需求越来越高。作为宽带需求最基本的支撑，频谱资源稀缺问题愈加突出和严重。因此，在频谱资源受限的条件下，如何进一步提高移动通信系统的频谱利用率和吞吐量是下一代移动通信系统设计中亟需解决的重要问题之一。With the vigorous development of the mobile Internet, the demand for high-speed data transmission in mobile communications is getting higher and higher. As the most basic support for broadband demand, the problem of scarcity of spectrum resources has become more prominent and serious. Therefore, under the condition of limited spectrum resources, how to further improve the spectrum utilization and throughput of the mobile communication system is one of the important issues to be solved urgently in the design of the next generation mobile communication system.

正交频分复用(OrthogonalFrequencyDivisionMultiplexing,OFDM)技术，由于其具有高频谱利用率以及很好的抗多径衰落能力等特点，已经成为第四代移动通信标志性的物理层传输承载技术“A.Doufexi,andS.Armour.Designconsiderationsandphysicallayerperformanceresultsfora4GOFDMsystememployingdynamicsubcarrierallocation.Proc.IEEEPIMRC,Sept.2005:357-361.”。为了扩大基站覆盖范围、获得分集增益，协同中继技术“RoyaArabLoodaricheh,ShankhanaadMallick,andVijayK.Bhargava.DistributedsubcarrierPairingandrelayselectionforOFDMbasedcooperativerelaynetworks.Proc.IEEEWCNC,Apri2013:3557-3562.”作为下一代无线通信系统中的关键技术之一引起了学术界和业界的广泛关注。中继节点通过放大转发或者译码转发方式将源节点的信息转发给目的节点。在双向无线中继网络中，与传统的多跳传输相比，物理层网络编码(PhysicalLayerNetworkCoding,PLNC)“S.Zhang,S.C.Liew,andP.P.Lam.Hottopic:physical-layernetworkcoding.Proc.Int.Conf.MobileComputingandNetworking,2006:358-365”，“S.Katti,S.Gollakota,andD.Katabi.Embracingwirelessinterference:analognetworkcoding.Proc.Conf.Applicat,Technol,ArchitandProtocolsforComput.Commun.,2007:397-408.”能够成倍提高系统的吞吐量性能。目前，在协同中继系统中，PLNC技术已成为研究的热点问题之一。Orthogonal Frequency Division Multiplexing (OFDM) technology, due to its high spectrum utilization rate and good anti-multipath fading ability, has become the symbolic physical layer transmission bearer technology of the fourth generation mobile communication "A. Doufexi, and S. Armour. Design considerations and physical layer performance results for a 4GOFDM system employing dynamic subcarrier allocation. Proc. IEE PIMRC, Sept. 2005: 357-361.". In order to expand base station coverage and obtain diversity gain, cooperative relay technology "RoyaArabLoodaricheh, ShankhanaadMallick, andVijayK.Bhargava.DistributedsubcarrierPairingandrelayselectionforOFDMbasedcooperativerelaynetworks.Proc.IEEEWCNC,Apri2013:3557-3562. Widespread attention from academia and industry. The relay node forwards the information of the source node to the destination node through amplification and forwarding or decoding and forwarding. In a two-way wireless relay network, compared with traditional multi-hop transmission, Physical Layer Network Coding (PhysicalLayerNetworkCoding, PLNC) "S. Zhang, S. C. Liew, and P. P. Lam. Hottopic: physical-layer network coding. Proc. Int. Conf. Mobile Computing and Networking, 2006: 358-365", "S. Katti, S. Gollakota, and D. Katabi. Embracing wireless interference: analog network coding. Proc. Conf. Applicat, Technol, Archit and Protocols for Comput. Commun., 2007: 397-408." Doubling the throughput performance of the system. At present, in the cooperative relay system, PLNC technology has become one of the hot issues of research.

在双向多中继系统中，受限于信道最差的中继，利用所有中继进行信息转发的方式不一定能够提高系统性能。利用中继选择技术“XiaochenXia,KuiXu,WenfengMa,andYouyunXu.OntheDesignofRelaySelectionStrategyforTwo-WayAmplify-and-ForwardMobileRelaying.IETCommu.2013,Vol.7(17):1948-1957.”通过在多个中继中选择一个或多个信道条件好的中继转发信息，能够获得分集增益从而提高系统误比特率性能。文献“J.leithon,S.Sumei,andY.Chau.RelaySelectionAlgorithmsforAnalogNetworkCodingOFDMSystems.IEEECommunicationLetters,2012,vol.16(9):1442-1445.”提出一种基于模拟网络编码的OFDM系统最小最大中继选择方法。该方法选择最小信道增益最大的中继来转发信息。仿真结果表明，与双向OFDM单中继系统相比，最小最大中继选择方法可以大幅提高系统的误码率和吞吐量性能。In a two-way multi-relay system, limited by the relay with the worst channel, using all relays for information forwarding may not necessarily improve system performance. Using relay selection technology "XiaochenXia, KuiXu, WenfengMa, and YouyunXu.OntheDesignofRelaySelectionStrategyforTwo-WayAmplify-and-ForwardMobileRelaying. IETCommu.2013, Vol.7(17):1948-1957." By selecting one or more relays Relay forwarding information with good channel conditions can obtain diversity gain and improve system bit error rate performance. The literature "J.leithon, S.Sumei, and Y.Chau. RelaySelection Algorithms for Analog Network Coding OFDM Systems. IEEE Communication Letters, 2012, vol. 16(9): 1442-1445." proposes a minimum and maximum relay selection method for OFDM systems based on analog network coding. This method selects the relay with the largest minimum channel gain to forward information. The simulation results show that compared with the bidirectional OFDM single-relay system, the minimum-maximum relay selection method can greatly improve the bit error rate and throughput performance of the system.

为了进一步提高PLNC-OFDM双向多中继系统的传输可靠性，文献“G.Bartoli,R.Fantacci,D.Marabissi,andR.Simoni.SubcarriersSuppressionMethodsforOFDMSystemswithDecode-and-ForwardNetworkCoding.IEEETrans.,WirelessCommunication,2013,vol.12(12):6034-6042.”提出两种子载波抑制方法。“子载波抑制”即在OFDM系统中放弃使用信道条件差的子载波而仅使用信道条件好的子载波来进行信息传输。信息传输之前，系统给定一个抑制门限值，信道增益的绝对值高于该门限值的子载波被用来传输信息而信道增益的绝对值低于该门限值的子载波则被放弃不用。子载波抑制能够大幅提高系统误比特率性能。在多径瑞利衰落信道条件下，子载波抑制在降低系统误比特率的同时，也会带来一定的系统吞吐量损失。In order to further improve the transmission reliability of the PLNC-OFDM two-way multi-relay system, the literature "G.Bartoli, R.Fantacci, D.Marabissi, and R.Simoni. (12):6034-6042." proposed two subcarrier suppression methods. "Subcarrier suppression" means giving up subcarriers with poor channel conditions and only using subcarriers with good channel conditions for information transmission in the OFDM system. Before information transmission, the system gives a suppression threshold value, the subcarrier whose absolute value of channel gain is higher than the threshold value is used to transmit information, and the subcarrier whose absolute value of channel gain is lower than the threshold value is discarded No need to. Subcarrier suppression can greatly improve system bit error rate performance. Under the condition of multipath Rayleigh fading channel, subcarrier suppression can reduce the bit error rate of the system, but also bring a certain loss of system throughput.

通过将网络编码的思想应用在无线广播通信中，能够有效的提高广播的效率，现阶段已有的专利成果如下：By applying the idea of network coding to wireless broadcast communication, the efficiency of broadcast can be effectively improved. The existing patent achievements at this stage are as follows:

通过将网络编码的思想应用在无线中继通信中，能够有效的提高中继通信的传输效率，现阶段已有的专利成果如下：By applying the idea of network coding to wireless relay communication, the transmission efficiency of relay communication can be effectively improved. The existing patent achievements at this stage are as follows:

1.上海交通大学提出的无线网络模拟网络编码方法，本发明公开了一种无线网络模拟网络编码方法，包括以下步骤：对接收到的重叠数据帧通过互相关运算检测出已知帧和目标帧的起始点和结束点；对数据进行频率偏移检测和补偿；再进行信道参数估计；再根据得到的信道参数，去除重叠数据帧中的已知帧，对目标帧进行恢复和重采样，重新获取采样点；对采样后的数据进行解码。本发明可以扩展模拟网络编码的应用范围，提高无线网络中的频谱利用率。1. The wireless network simulation network coding method proposed by Shanghai Jiaotong University, the present invention discloses a wireless network simulation network coding method, comprising the following steps: detecting known frames and target frames through cross-correlation operations on received overlapping data frames The starting point and the end point of the data frame; frequency offset detection and compensation for the data; then channel parameter estimation; and then according to the obtained channel parameters, remove the known frame in the overlapping data frame, restore and resample the target frame, and re- Obtain sampling points; decode the sampled data. The invention can expand the application scope of the analog network coding and improve the frequency spectrum utilization rate in the wireless network.

2.中国计量学院提出的双向中继信道模型的正交差分空时网络编码方法，本发明公开了一种双向中继信道模型的正交差分空时网络编码方法，所述模型包括两个信源和，一个中继R，信源引入多天线机制，配备有多个天线；包括如下步骤：信号传输过程分为两个阶段：信源传输阶段，比特流通过星座映射、Alamouti编码、差分空时调制，得到发射信号矩阵；中继广播阶段，实现信号的接收、检测、解调，然后实现两信源信息的异或网络编码、差分调制，并映射为发送符号，广播给两信源；其中信号接收时采用多分组处理，采用多符号差分球形译码完成信号检测，对上行链路中继和下行链路信源的接收信号译码都适用。2. The orthogonal difference space-time network coding method of the two-way relay channel model proposed by the China Metrology Institute. The present invention discloses a method for the orthogonal difference space-time network coding of the two-way relay channel model. The model includes two signal The source and a relay R, the source introduces a multi-antenna mechanism and is equipped with multiple antennas; it includes the following steps: the signal transmission process is divided into two stages: the source transmission stage, the bit stream is mapped through constellation mapping, Alamouti coding, and differential space time modulation to obtain the transmit signal matrix; in the relay broadcast stage, signal reception, detection, and demodulation are realized, and then the XOR network coding and differential modulation of the information of the two sources are realized, and mapped to transmit symbols, and broadcast to the two sources; Among them, multi-group processing is adopted for signal reception, and multi-symbol differential spherical decoding is used to complete signal detection, which is applicable to both uplink relay and downlink signal source decoding.

3.西安交通大学提出的一种双向中继系统中自适应变时隙模拟网络编码策略，本发明提供一种双向中继系统中自适应变时隙模拟网络编码策略，该策略基于瞬时信道信息，在不改变系统平均功率与协作周期的条件下，以最大化瞬时互信息量的原则动态调整传输时隙数，理论分析和仿真结果表明，与固定时隙的模拟网络编码策略相比，本发明所提出的策略在获得分集增益的同时降低了中断概率，另外，本发明方法采用简单的等功率分配方案能够获得近似最优的性能。3. An adaptive variable time slot analog network coding strategy in a two-way relay system proposed by Xi'an Jiaotong University. The present invention provides an adaptive variable time slot analog network coding strategy in a two-way relay system. The strategy is based on instantaneous channel information , under the condition of not changing the average power of the system and the cooperation cycle, dynamically adjust the number of transmission slots based on the principle of maximizing the amount of instantaneous mutual information. Theoretical analysis and simulation results show that, compared with the analog network coding strategy of fixed slots, The strategy proposed by the invention reduces the probability of interruption while obtaining diversity gain. In addition, the method of the invention adopts a simple equal power allocation scheme to obtain approximately optimal performance.

4.哈尔滨工业大学深圳研究生院提出的基于FQPSK调制的物理层网络编码系统及方法，本发明提供了一种基于FQPSK调制的物理层网络编码方法及系统，该基于FQPSK调制的物理层网络编码方法，发射端单元包括执行如下步骤：A.两个信号源分别发射原始信息x_A和x_B；B.将两个原始信息x_A和x_B分别调制之后调制到高频载波上面变成发射信号z_A和z_B；C.中继模块接收到混合后的信号表示为：Y_R(t)＝[z_A(t)+n(t)]+[z_B(t)+n'(t)]，Y_R(t)表示接收到的混合波形信号。本发明的有益效果是使用FQPSK调制对物理层网络编码信号进行恒包络保护，成功解决了在中继处对叠加信号的检测与分类问题，使用波形簇分类准则代替已有的星座分类准则，避开了FQPSK调制星座无规则这一缺点。4. The physical layer network coding system and method based on FQPSK modulation proposed by the Shenzhen Graduate School of Harbin Institute of Technology, the present invention provides a physical layer network coding method and system based on FQPSK modulation, the physical layer network coding method based on FQPSK modulation , the transmitter unit includes the following steps: A. Two signal sources transmit original information x _A and x _B respectively; B. Modulate the two original information x _A and x _B respectively and then modulate them onto a high-frequency carrier to become a transmission signal z _A and z _B ; C. The mixed signal received by the relay module is expressed as: Y _R (t)=[z _A (t)+n(t)]+[z _B (t)+n'(t )], Y _R (t) represents the received mixed waveform signal. The beneficial effect of the present invention is that FQPSK modulation is used to perform constant envelope protection on physical layer network coded signals, and the problem of detection and classification of superimposed signals at the relay is successfully solved, and the waveform cluster classification criterion is used to replace the existing constellation classification criterion, This avoids the shortcoming of irregular FQPSK modulation constellation.

5.中国空间技术研究院和深圳大学提出的在中继系统中通过信道量化进行物理层网络编码的方法，本发明涉及在中继系统中通过信道量化进行物理层网络编码的方法，包括如下步骤：将表示所述两个端节点到所述中继节点的信道矩阵进行QR分解，并对接收向量乘以Q矩阵，得到分别表示第一端节点和第二端节点发送到所述中继节点信号的第一中间层信号和第二中间层信号；利用所述第二中间层信号对所述第二端节点发送的编码信号进行估值，得到所述第二端节点发送的信号估值；利用第一中间层信号和第二中间层信号估值，对所述第一端节点和第二端节点发送的编码信号进行估值，得到所述中继节点收到的复合信号的估值，得到网络编码；其中，所述估值步骤包括根据所述第一中间层信号表达式中不同的参数值，对其进行量化和映射。实施本发明的一种中继系统上行信道的量化方法，具有以下有益效果：其计算简单、效率较高。5. The method for carrying out physical layer network coding through channel quantization in a relay system proposed by China Academy of Space Technology and Shenzhen University, the present invention relates to a method for carrying out physical layer network coding through channel quantization in a relay system, comprising the following steps : QR decomposition is performed on the channel matrix representing the two end nodes to the relay node, and the receiving vector is multiplied by the Q matrix to obtain the signals respectively representing that the first end node and the second end node send to the relay node The first intermediate layer signal and the second intermediate layer signal of the signal; using the second intermediate layer signal to estimate the coded signal sent by the second end node to obtain the signal estimate sent by the second end node; Estimate the coded signal sent by the first end node and the second end node by using the first intermediate layer signal and the second intermediate layer signal estimate to obtain an estimate of the composite signal received by the relay node, Obtaining network coding; wherein, the estimating step includes performing quantization and mapping according to different parameter values in the expression of the first intermediate layer signal. A method for quantifying the uplink channel of a relay system implemented in the present invention has the following beneficial effects: the calculation is simple and the efficiency is high.

6.哈尔滨工业大学提出的基于MQAM调制方式的物理层网络编码的无线通信方法，基于MQAM调制方式的物理层网络编码的无线通信方法，涉及一种无线通信领域。本发明解决了现有的传输方式在双向中继信道中需要的三个时隙、四个时隙导致系统性能低的问题。具体方法为，对用户N₁、N₂的编码比特信息S₁、S₂进行MQAM调制，得到调制后的信号s₁(t)、s₂(t)并同时向中继节点NR发送，中继节点NR将其直接相加得到和信号r_R(t)并对r_R(t)进行判决，将判决结果进一步映射为S₁和S₂的网络编码信息S_R；之后中继节点N_R对S_R重新进行MQAM调制，并将已调信号s_R(t)向用户节点N₁和N₂广播，N₁、N₂分别对接收到的s_R(t)进行解调，将得到网络编码信息S_R与保存在该用户的本地缓存中的发送信息进行按位比特异或运算，以获得另一用户的比特信息，从而实现一次信息交换过程。本发明适用于无线通信。6. The wireless communication method based on the physical layer network coding of the MQAM modulation method proposed by Harbin Institute of Technology, the wireless communication method of the physical layer network coding based on the MQAM modulation method, relates to a wireless communication field. The invention solves the problem that the system performance is low due to three time slots and four time slots required in the two-way relay channel in the existing transmission mode. The specific method is to perform MQAM modulation on the coded bit information S ₁ and S ₂ of users N ₁ and N ₂ to obtain modulated signals s ₁ (t) and s ₂ (t) and send them to the relay node NR at the same time. The successor node NR directly adds it to obtain the sum signal r _R (t) and judges r _R (t), and further maps the judgment result to the network coding information S _R of S ₁ and S ₂ ; then the relay node _NR Perform MQAM modulation on _SR again, and broadcast the modulated signal s _R (t) to user nodes N ₁ and N ₂ , N ₁ and N ₂ respectively demodulate the received s _R (t), and the network will be obtained The coded information _SR and the transmission information stored in the user's local buffer perform a bit-wise XOR operation to obtain the bit information of another user, thereby realizing an information exchange process. The invention is applicable to wireless communication.

7.哈尔滨工业大学提出的基于MFSK调制方式的物理层网络编码的无线通信方法，本发明涉及无线通信领域。它是通过压缩数据通信的时隙数目进而实现提高无线通信系统的性能。其方法：分别将两个用户节点发送的编码后的比特信息进行MFSK调制，并同时发送给中继节点；中继节点进行相加获得和信号；并进行判决后映射为网络编码的比特信息；然后进行MFSK调制后向两个用户节点广播；两个用户分别对广播的调制信号进行解调，并分别将与保存在本地缓存中的对应的调制信号进行按位进行比特异或运算后输出，从而实现基于MFSK调制方式的物理层网络编码的无线通信。本发明适用于基于MFSK调制方式的物理层网络编码的无线通信。7. The wireless communication method based on the physical layer network coding of the MFSK modulation mode proposed by Harbin Institute of Technology, the present invention relates to the field of wireless communication. It improves the performance of the wireless communication system by compressing the number of time slots for data communication. The method: respectively perform MFSK modulation on the coded bit information sent by two user nodes, and send it to the relay node at the same time; the relay node performs summing to obtain the sum signal; and maps it to network coded bit information after making a judgment; Then perform MFSK modulation and broadcast to two user nodes; the two users respectively demodulate the broadcast modulated signal, and perform bit-by-bit XOR operation with the corresponding modulated signal stored in the local buffer, and then output it. In this way, the wireless communication based on the physical layer network coding of the MFSK modulation mode is realized. The invention is applicable to the wireless communication of physical layer network coding based on MFSK modulation mode.

8.哈尔滨工业大学提出的一种基于双向中继模型的平坦频选衰落信道中物理层网络编码的无线通信方法，该方法涉及无线通信方法。本发明消除了调制信号实部和虚部之间干扰，降低了中继接收机的复杂度。本发明中两个信源节点将信息数据进行QPSK调制、预编码、载波调制、再载波调制后发送给中继节点，中继节点将接收的信号相加，再对和信号进行载波解调后，判决映射求得广播数据；再对广播数据进行QPSK调制、载波调制后广播发送；信源节点将接收到广播的载波调制信号进行载波解调，信源节点S1和信源节点S2分别对载波解调后和信号进行信号处理，信源节点S1获得信源节点S2发送信号的估计值，信源节点S2获得信源节点S1发送信号的估计值完成通信。本发明用于无线通信。8. A wireless communication method of physical layer network coding in a flat frequency-selective fading channel based on a two-way relay model proposed by Harbin Institute of Technology, which relates to wireless communication methods. The invention eliminates the interference between the real part and the imaginary part of the modulation signal, and reduces the complexity of the relay receiver. In the present invention, the two source nodes send the information data to the relay node after performing QPSK modulation, precoding, carrier modulation and re-carrier modulation, and the relay node adds the received signals, and then performs carrier demodulation on the sum signal , the broadcast data is obtained by decision mapping; then the broadcast data is QPSK modulated and carrier modulated, and then broadcast and sent; the source node performs carrier demodulation on the received broadcast carrier modulation signal, and the source node S1 and source node S2 respectively After demodulation and signal processing, the source node S1 obtains the estimated value of the signal sent by the source node S2, and the source node S2 obtains the estimated value of the signal sent by the source node S1 to complete the communication. The present invention is used for wireless communication.

9.北京邮电大学提出的用于双向中继通信系统的基于符号的物理层网络编码方法，本发明方法操作步骤如下：第一时隙是中继接收信息：两个源节点分别向中继发送各自已调信号，中继对接收的叠加信号做自相关运算，得到自相关矩阵，再用最大似然ML检测算法从该矩阵中检测出待广播的网络编码符号，使得网络编码符号的检测空间缩小，从而降低信号检测难度，同时获得接收分集增益，保证系统误码性能。第二时隙是中继广播信息：中继将检测到的网络编码符号广播出去，两个源节点分别采用自干扰消除方法对接收信号解码获得对方信息，完成通信过程。本发明利用M阶移相键控MPSK信号特点降低中继处理信号的运算复杂度，获得接收分集增益，适用于双向中继信道下对称和不对称速率的MPSK调制系统。9. The symbol-based physical layer network coding method for the two-way relay communication system proposed by Beijing University of Posts and Telecommunications. The operation steps of the method of the present invention are as follows: the first time slot is for the relay to receive information: two source nodes send respectively to the relay Each modulated signal, the relay performs autocorrelation operation on the received superposition signal to obtain an autocorrelation matrix, and then uses the maximum likelihood ML detection algorithm to detect the network coding symbols to be broadcast from the matrix, so that the detection space of the network coding symbols Reduced, thereby reducing the difficulty of signal detection, while obtaining receive diversity gain, ensuring system bit error performance. The second time slot is the relay broadcast information: the relay broadcasts the detected network coding symbols, and the two source nodes respectively use the self-interference cancellation method to decode the received signal to obtain the information of the other party, and complete the communication process. The invention utilizes the characteristics of the M-order phase-shift keying MPSK signal to reduce the computational complexity of the relay processing signal and obtain the receiving diversity gain, and is suitable for MPSK modulation systems with symmetric and asymmetric rates under the two-way relay channel.

10.中国人民解放军理工大学提出的具有频偏的双向OFDM系统的联合信道网络编码方法，该方法第一阶段源节点广播OFDM符号，中继节点接收到的信号是两个源节点广播的具有不同频偏的OFDM符号的叠加，第二阶段为中继节点根据接收到的叠加OFDM符号估计出两个源节点与中继节点之间不同的载波频偏和信道信息，并进行联合信道网络编码，之后将网络编码后的信息广播给两个源节点，两个源节点利用接收到的联合信道网络编码后的OFDM符号进行联合信道网络译码，完成双向中继。本发明在载波频偏存在的条件下，能够在获得更高传输效率的同时实现可靠的双向信息传输。10. A joint channel network coding method for a two-way OFDM system with frequency offset proposed by the Chinese People's Liberation Army University of Science and Technology. In the first stage of the method, the source node broadcasts OFDM symbols, and the signal received by the relay node is the signal broadcast by the two source nodes with different In the superposition of frequency offset OFDM symbols, the second stage is that the relay node estimates different carrier frequency offsets and channel information between the two source nodes and the relay node based on the received superimposed OFDM symbols, and performs joint channel network coding. Afterwards, the network-encoded information is broadcast to two source nodes, and the two source nodes use the received OFDM symbols encoded by the joint channel network to perform joint channel network decoding to complete two-way relay. Under the condition that the carrier frequency deviation exists, the present invention can realize reliable two-way information transmission while obtaining higher transmission efficiency.

11.天津大学提出的利用相关网络编码实现非相关接收的收发方法，本发明涉及无线多跳网络技术。具体讲，利用相关网络编码实现非相关接收的收发方法。为提高无线多跳通信传输效率，降低技术复杂度，降低通信误码率，本发明采用的技术方案是：在源端物理层进行相关网络PCNC编码；中继利用信道衰减系数，检测并利用唯一性映射关系将检测到的信号映射成去噪后的混合信号，并对混合信号进行差分调制发送给两个相互通信的源端；源端接收时，利用混合信号所反映前后时刻的信号的差分关系，实现不需要知道任何信道特性情况下的非相关接收，以恢复出所述的两个连续时隙的信号和，并减去本端的信号得到对端的信号。本发明主要用于需要中继的无线协作通信中的传输、没有直线传播线路的基站和移动终端之间的传输。11. A method for transmitting and receiving non-correlated reception by using correlated network coding proposed by Tianjin University. The present invention relates to wireless multi-hop network technology. Specifically, a method for transmitting and receiving non-correlated reception is realized by using correlation network coding. In order to improve wireless multi-hop communication transmission efficiency, reduce technical complexity, and reduce communication bit error rate, the technical solution adopted in the present invention is: perform relevant network PCNC coding at the source end physical layer; relay uses channel attenuation coefficient to detect and utilize unique Map the detected signal into a mixed signal after denoising, and differentially modulate the mixed signal and send it to two sources that communicate with each other; when the source receives it, it uses the difference between the signals before and after the time reflected by the mixed signal relationship, to achieve non-correlated reception without knowing any channel characteristics, to recover the signal sum of the two consecutive time slots, and subtract the signal at the local end to obtain the signal at the opposite end. The present invention is mainly used for the transmission in the wireless cooperative communication requiring relay, and the transmission between the base station and the mobile terminal without straight-line propagation lines.

现有的网络编码广播方法很少考虑在物理层利用OFDM传输技术。在OFDM广播系统中，由于信道所具有的频率选择性衰落，因此，每个子载波的信道容量是不同的。需要将有限的能量资源在具有不同信道容量的子载波上进行分配，从而最优化系统的传输速率性能。在多中继系统中，由于终端与中继之间的链路状态各不相同，需要从所有中选择最优性能的中继进行信号转发，从而获得最优性能。因此，在双向OFDM多中继系统中，需要将OFDM调制方式中由多个子载波提供的自由度与多个中继提供的自由度进行有效利用，从而提高系统性能。Existing network-coded broadcast methods seldom consider utilizing OFDM transmission technology at the physical layer. In the OFDM broadcasting system, due to the frequency selective fading of the channel, the channel capacity of each subcarrier is different. It is necessary to allocate limited energy resources on subcarriers with different channel capacities, so as to optimize the transmission rate performance of the system. In a multi-relay system, since the link states between the terminal and the relay are different, it is necessary to select the relay with the best performance from all the relays for signal forwarding, so as to obtain the best performance. Therefore, in a two-way OFDM multi-relay system, it is necessary to effectively utilize the degree of freedom provided by multiple subcarriers and the degree of freedom provided by multiple relays in OFDM modulation, so as to improve system performance.

发明内容Contents of the invention

本发明的目的是针对上述现有技术的不足，提供一种基于PLNC的双向OFDM多中继系统中的联合子载波抑制与中继选择方法，本基于PLNC的双向OFDM多中继系统中的联合子载波抑制与中继选择方法不仅提高了系统有效性，而且增强了系统可靠性。The purpose of the present invention is to address the above-mentioned deficiencies in the prior art, providing a joint subcarrier suppression and relay selection method in a PLNC-based two-way OFDM multi-relay system. The method of subcarrier suppression and relay selection not only improves system effectiveness, but also enhances system reliability.

为解决上述技术问题，本发明的技术方案为：基于PLNC的双向OFDM多中继系统中的联合子载波抑制与中继选择方法，其特征在于包括以下步骤：For solving the problems of the technologies described above, the technical solution of the present invention is: joint subcarrier suppression and relay selection method in the two-way OFDM multi-relay system based on PLNC, it is characterized in that comprising the following steps:

基于TDMA的双向多中继系统由N个中继节点{R₁,R₂,…R_N}和两个源节点S₁,S₂构成，所有节点均配备单根天线并工作在半双工模式；S₁知道S₁到每一个中继节点之间的信道状态信息；S₂知道S₂到每一个中继节点之间的信道状态信息；所述基于TDMA的双向多中继系统采用OFDM传输方式，子载波个数用K表示；S₁,S₂到中继节点的信道是多径瑞利衰落信道，用向量h_i表示：A two-way multi-relay system based on TDMA consists of N relay nodes {R ₁ , R ₂ ,…R _N } and two source nodes S ₁ , S ₂ , all nodes are equipped with a single antenna and work in half-duplex mode; S ₁ knows the channel state information between S ₁ and each relay node; S ₂ knows the channel state information between S ₂ and each relay node; the two-way multi-relay system based on TDMA adopts OFDM Transmission mode, the number of subcarriers is represented by K; the channel from S ₁ and S ₂ to the relay node is a multipath Rayleigh fading channel, represented by vector h _i :

h_i＝[h_i[0],h_i[1],…,h_i[L-1]]^Ti＝1,2(1)h _i ＝[h _i [0],h _i [1],...,h _i [L-1]] ^T i=1,2(1)

其中，L表示路径数；S₁,S₂到中继节点的信道独立同分布，在第k个子载波上的频域信道为H_i[k]：in, L represents the number of paths; the channels from S ₁ and S ₂ to the relay node are independently and identically distributed, and the frequency domain channel on the kth subcarrier is H _i [k]:

${H h}_{i i} [[k k]] = = {Σ Σ}_{l l = = 00}^{L L - - 11} {h h}_{i i} {[[l l]]}^{- - 22 j j π π \frac{k k}{K K} l l},, i i = = 11,, 22 - - - - - - ((22))$

每一次的信息交换可以分为两个阶段：多址接入阶段和广播阶段：Each information exchange can be divided into two phases: the multiple access phase and the broadcast phase:

多址接入阶段：首先，S₁,S₂在第k个子载波上分别需要发送信息然后，信息经过调制后可以表示成最后，S₁,S₂把信息发送给所有的中继节点；第m个中继的第k个子载波上的接收信号可以表示为：Multiple access stage: First, S ₁ and S ₂ need to send information on the kth subcarrier respectively Then, the information After modulation, it can be expressed as Finally, S ₁ , S ₂ put the information Sent to all relay nodes; the received signal on the kth subcarrier of the mth relay can be expressed as:

${Y Y}_{{R R}_{m m}}^{[[k k]]} = = {H h}_{11 m m}^{[[k k]]} {X x}_{11}^{[[k k]]} + + {H h}_{22 m m}^{[[k k]]} {X x}_{22}^{[[k k]]} + + {N N}_{{R R}_{m m}}^{[[k k]]} - - - - - - ((33))$

表示从S_i到R_m之间多径瑞利衰落信道在第k个子载波上的增益，m∈{1,…N}，k∈{1,…K}，i∈{1,2}，且从S₁,S₂到中继节点和中继节点到S₁,S₂的信道是相同的；表示加性高斯白噪声； Represents the gain of the multipath Rayleigh fading channel from S _i to R _m on the kth subcarrier, m∈{1,…N}, k∈{1,…K}, i∈{1,2}, And the channels from S ₁ , S ₂ to the relay node and from the relay node to S ₁ , S ₂ are the same; Represents additive white Gaussian noise;

广播阶段：首先，S₁,S₂在所有中继中选择一个信道状态最好的中继；然后，选定的中继利用译码转发的方式将接收到的信息广播给S₁,S₂；最后，S₁,S₂接收到的信息可以表示如下：Broadcast stage: first, S ₁ and S ₂ select a relay with the best channel state among all relays; then, the selected relay broadcasts the received information to S ₁ and S ₂ by means of decoding and forwarding ; Finally, the information received by S ₁ and S ₂ can be expressed as follows:

${r r}_{{S S}_{11}}^{[[k k]]} = = {H h}_{11 m m}^{[[k k]]} {X x}_{{R R}_{m m}}^{[[k k]]} + + {N N}_{11}^{[[k k]]} - - - - - - ((44))$

${Y Y}_{{S S}_{22}}^{[[k k]]} = = {H h}_{22 m m}^{[[k k]]} {X x}_{{R R}_{m m}}^{[[k k]]} + + {N N}_{22}^{[[k k]]} - - - - - - ((55))$

表示中继节点网络编码得到的信息经过调制后得到的信息，表示源节点S_i接收到的信息，表示加性高斯白噪声，i∈{1,2}。 Indicates the information obtained by the network encoding of the relay node The information obtained after modulation, Indicates the information received by the source node S _i , Denotes additive white Gaussian noise, i ∈ {1,2}.

进一步的，子载波抑制包括以下步骤：Further, subcarrier suppression includes the following steps:

由于无线信道的多径传输特性会导致频率选择性衰落，在基于TDMA的双向多中继系统中，信道的频率选择性衰落会造成不同的子载波具有不同的信道增益，子载波抑制是仅利用信道条件好的子载波传输信息，而信道条件差的子载波放弃不用，用表示抑制门限，当子载波的信道增益高于时，定义该子载波为“活跃子载波”；反之，当子载波的信道增益低于时，定义该子载波为“抑制子载波”；每一个子载波是否是活跃可以用子载波状态表示如下：Since the multipath transmission characteristics of the wireless channel will lead to frequency selective fading, in the two-way multi-relay system based on TDMA, the frequency selective fading of the channel will cause different subcarriers to have different channel gains, and subcarrier suppression is only used The subcarriers with good channel conditions transmit information, and the subcarriers with poor channel conditions are discarded. Indicates the suppression threshold, when the channel gain of the subcarrier is higher than When , the subcarrier is defined as an "active subcarrier"; otherwise, when the channel gain of the subcarrier is lower than , define the subcarrier as "suppressed subcarrier"; whether each subcarrier is active and available subcarrier status Expressed as follows:

${F f}_{i i m m}^{[[k k]]} = = \{\begin{matrix} 11,, & i i f f & | | {\overset{^^}{H h}}_{i i m m}^{[[k k]]} | | &GreaterEqual; &Greater Equal; {λ λ}_{00}^{i i} \\ 00,, & i i f f & | | {\overset{^^}{H h}}_{i i m m}^{[[k k]]} | | < < {λ λ}_{00}^{i i} \end{matrix},, i i = = 11,, 22 - - - - - - ((66))$

“1”表示该子载波是活跃子载波；“0”表示该子载波是抑制子载波；表示从S_i到R_m之间多径瑞利衰落信道在第k个子载波上增益的估计值；只有在两个源节点之间都是“活跃子载波”时，该子载波才被中继用来传输信息，定义为“使用的子载波”；系统仅使用“使用的子载波”来传输信息而不使用被抑制的子载波；因此，第k个子载波是否被第m个中继使用可以用状态表示："1" indicates that the subcarrier is an active subcarrier; "0" indicates that the subcarrier is a suppressed subcarrier; Represents the estimated value of the gain of the multipath Rayleigh fading channel from S _i to R _m on the kth subcarrier; the subcarrier is only relayed if both source nodes are "active subcarriers" Used to transmit information, defined as "used subcarriers"; the system only uses "used subcarriers" to transmit information and does not use suppressed subcarriers; therefore, whether the kth subcarrier is used by the mth relay can be use status express:

${F f}_{{R R}_{m m}}^{[[k k]]} = = {F f}_{11 m m}^{[[k k]]} {F f}_{22 m m}^{[[k k]]} - - - - - - ((77))$

若则该子载波是“使用的子载波”，被中继R_m使用；若则该子载波被放弃不用。like Then this subcarrier is the "used subcarrier" and is used by relay R _m ; if Then the subcarrier is discarded.

进一步的，中继选择方法包括以下步骤：Further, the relay selection method includes the following steps:

在基于TDMA的双向多中继系统中选择信道条件最好的一个中继来进行传输信息，根据最小最大原则选择一个中继：In the two-way multi-relay system based on TDMA, a relay with the best channel condition is selected to transmit information, and a relay is selected according to the minimum and maximum principle:

${R R}^{* *} = = arg arg \underset{m m}{max max} {{\underset{k k &Element; &Element; I I}{min min} {{\underset{i i}{min min} {{| | {H h}_{i i m m}^{[[k k]]} | |}}}}}} - - - - - - ((88))$

R^*表示选定的中继，m表示第m个中继，m∈{1,…N}；i对应两个源节点的编号，i∈{1,2}；k表示第k个子载波，k∈{1,…K}；I表示使用的子载波集合，表示从S_i到R_m之间多径瑞利衰落信道在第k个子载波上增益的模值；R ^* represents the selected relay, m represents the mth relay, m∈{1,…N}; i corresponds to the number of two source nodes, i∈{1,2}; k represents the kth subcarrier, k∈{1,…K}; I represents the set of subcarriers used, Represents the modulus value of the gain on the kth subcarrier of the multipath Rayleigh fading channel from S _i to R _m ;

根据子载波抑制方法不同，结合最小最大中继选择，所述联合子载波抑制与中继选择方法包括：FT-J和FNS-J，FT-J为固定抑制门限的JSSRS方法、FNS-J为固定子载波个数的JSSRS方法。According to different subcarrier suppression methods, combined with minimum and maximum relay selection, the joint subcarrier suppression and relay selection method includes: FT-J and FNS-J, FT-J is the JSSRS method with a fixed suppression threshold, and FNS-J is A JSSRS method with a fixed number of subcarriers.

进一步的，固定抑制门限的JSSRS方法(FixThresholdbasedJSSRS,FT-J)方法包括以下步骤：Further, the JSSRS method (FixThresholdbasedJSSRS, FT-J) method of fixing the suppression threshold comprises the following steps:

FT-J首先进行子载波抑制，然后在所有中继中选择一个信道条件最好的中继进行信息传输；在子载波抑制之前，S₁,S₂需要确定抑制门限λ₀；FT-J的λ₀值是S₁,S₂直接确定的一个常数，该常数在多址接入和广播两个时隙期间保持不变；S₁,S₂根据上述的子载波抑制方法对所有子载波进行抑制操作：FT-J performs subcarrier suppression first, and then selects a relay with the best channel condition among all relays for information transmission; before subcarrier suppression, S ₁ and S ₂ need to determine the suppression threshold λ ₀ ; FT-J The value of λ ₀ is a constant directly determined by S ₁ and S ₂ , which remains unchanged during the _two time slots of multiple access and broadcast _; Inhibit operation:

${F f}_{11 i i m m}^{[[k k]]} = = \{\begin{matrix} 11,, & i i f f & | | {\overset{^^}{H h}}_{i i m m}^{[[k k]]} | | &GreaterEqual; &Greater Equal; {λ λ}_{00} \\ 00,, & i i f f & | | {\overset{^^}{H h}}_{i i m m}^{[[k k]]} | | < < {λ λ}_{00} \end{matrix},, i i = = 11,, 22 - - - - - - ((99))$

${F f}_{11 {R R}_{m m}}^{[[k k]]} = = {F f}_{1111 m m}^{[[k k]]} {F f}_{1212 m m}^{[[k k]]} - - - - - - ((1010))$

${H h}_{11 i i m m}^{[[k k]]} = = {F f}_{11 {R R}_{m m}}^{[[k k]]} \times \times {H h}_{i i m m}^{[[k k]]} - - - - - - ((1111))$

表示S_i到中继之间的子载波状态，“1”表示该子载波是活跃子载波；“0”表示该子载波是抑制子载波；表示中继左右两边的子载波是否是“使用的子载波”，表示该子载波是“使用的子载波”，表示该子载波被放弃不用；表示经过子载波抑制之后各子载波的信道是否被使用；表示“使用的子载波”信道被使用，表示抑制子载波的信道放弃不用； Indicates the subcarrier status between S _i and the relay, "1" indicates that the subcarrier is an active subcarrier; "0" indicates that the subcarrier is a suppressed subcarrier; Indicates whether the subcarriers on the left and right sides of the relay are "used subcarriers", Indicates that the subcarrier is the "used subcarrier", Indicates that the subcarrier is abandoned; Indicates whether the channel of each subcarrier is used after subcarrier suppression; Indicates that the "subcarrier used" channel is used, Indicates that the channel of the suppressed subcarrier is abandoned;

最后在所有中继中选择一个信道条件最好的中继进行信息传输；Finally, select a relay with the best channel condition among all relays for information transmission;

${R R}^{* *} = = arg arg \underset{m m}{max max} {{\underset{k k &Element; &Element; {I I}_{11}}{min min} {{\underset{i i}{min min} {{| | {H h}_{11 i i m m}^{[[k k]]} | |}}}}}} - - - - - - ((1212))$

R^*表示选定的中继，m表示第m个中继，m∈{1,…N}；i对应两个源节点，i∈{1,2}；k表示第k个子载波，k∈{1,…K}；I₁表示FT-J方法中使用的子载波集合，表示从S_i到R_m之间使用的子载波信道在第k个子载波上增益的模值。R ^* represents the selected relay, m represents the mth relay, m∈{1,…N}; i corresponds to two source nodes, i∈{1,2}; k represents the kth subcarrier, k∈ {1,...K}; I ₁ represents the set of subcarriers used in the FT-J method, Indicates the modulus of the gain of the subcarrier channel used from S _i to R _m on the kth subcarrier.

如果λ₀比较小，则有些中继有被抑制子载波而有些中继没有被抑制子载波，这样，所有中继使用的子载波的最小信道增益是不同的，与最小最大中继选择进行联合设计后，系统性能会得到较大提升。然而，如果λ₀比较大，所有中继的子载波都经历子载波抑制，他们使用的子载波的最小信道增益几乎是相同的，在这种情况下，再进行最小最大中继选择后，系统性能不能得到改善。If λ ₀ is small, some relays have suppressed subcarriers and some relays do not. In this way, the minimum channel gain of subcarriers used by all relays is different, combined with minmax relay selection After the design, the system performance will be greatly improved. However, if λ ₀ is relatively large, all subcarriers of relays undergo subcarrier suppression, and the minimum channel gains of the subcarriers they use are almost the same. In this case, after min-max relay selection, the system Performance cannot be improved.

进一步的，固定子载波个数的JSSRS方法(FixNumberofSubcarriersbasedJSSRS,FNS-J)方法包括以下步骤：Further, the JSSRS method (FixNumberofSubcarriersbasedJSSRS, FNS-J) method of fixing the number of subcarriers includes the following steps:

与FT-J类似，FNS-J首先进行子载波抑制，然后在所有中继中选择一个信道条件最好的中继进行信息传输；在子载波抑制之前，S₁,S₂需要确定抑制门限λ₀；与FT-J不同的是，FNS-J需要S₁,S₂首先确定使用的子载波的个数Q，Q是常数；根据常数Q来确定临时抑制门限，即S₁,S₂在所有K个子载波中选择信道条件最好的Q个子载波来传输信息(0＜Q≤K)，把第Q好的信道增益模制作为临时抑制门限，即对所有子载波进行抑制操作：Similar to FT-J, FNS-J performs subcarrier suppression first, and then selects a relay with the best channel conditions among all relays for information transmission; before subcarrier suppression, S ₁ and S ₂ need to determine the suppression threshold λ ₀ ; Different from FT-J, FNS-J needs S ₁ , S ₂ to first determine the number of subcarriers Q used, Q is a constant; determine the temporary suppression threshold according to the constant Q, that is, S ₁ , S ₂ in Among all the K subcarriers, select the Q subcarriers with the best channel conditions to transmit information (0<Q≤K), and model the Qth best channel gain as the temporary suppression threshold, that is Suppress all subcarriers:

${F f}_{22 i i m m}^{[[k k]]} = = \{\begin{matrix} 11,, & i i f f & | | {\overset{^^}{H h}}_{i i m m}^{[[k k]]} | | &GreaterEqual; &Greater Equal; | | {H h}_{i i m m}^{[[Q Q]]} | | \\ 00,, & i i f f & | | {\overset{^^}{H h}}_{i i m m}^{[[k k]]} | | < < | | {H h}_{i i m m}^{[[Q Q]]} | | \end{matrix},, i i = = 11,, 22 - - - - - - ((1313))$

${F f}_{22 {R R}_{m m}}^{[[k k]]} = = {F f}_{21 twenty one m m}^{[[k k]]} {F f}_{22 twenty two m m}^{[[k k]]} - - - - - - ((1414))$

${H h}_{22 i i m m}^{[[k k]]} = = {F f}_{22 {R R}_{m m}}^{[[k k]]} \times \times {H h}_{i i m m}^{[[k k]]} - - - - - - ((1515))$

表示S_i到中继之间的子载波状态，“1”表示该子载波是活跃子载波；“0”表示该子载波是抑制子载波；表示该子载波是否是“使用的子载波”，表示该子载波是“使用的子载波”，表示该子载波被放弃不用；表示经过子载波抑制各子载波的信道是否被使用；表示“使用的子载波”信道被使用，表示抑制子载波的信道放弃不用； Indicates the subcarrier status between S _i and the relay, "1" indicates that the subcarrier is an active subcarrier; "0" indicates that the subcarrier is a suppressed subcarrier; Indicates whether this subcarrier is a "used subcarrier", Indicates that the subcarrier is the "used subcarrier", Indicates that the subcarrier is abandoned; Indicates whether the channel of each subcarrier suppressed by the subcarrier is used; Indicates that the "subcarrier used" channel is used, Indicates that the channel of the suppressed subcarrier is abandoned;

在多址接入和广播两个时隙期间，Q固定不变，而抑制门限动态变化；因此，同一个中继的两个抑制门限不相同；不同的中继这一门限值也不相同；最后在所有中继中选择一个信道条件最好的中继传输信息：During the two time slots of multiple access and broadcast, Q is fixed, while the suppression threshold changes dynamically; therefore, the two suppression thresholds of the same relay Not the same; different relays have different thresholds; finally select a relay with the best channel conditions among all relays to transmit information:

${R R}^{* *} = = arg arg \underset{m m}{max max} {{\underset{k k &Element; &Element; {I I}_{22}}{min min} {{\underset{i i}{min min} {{| | {H h}_{22 i i m m}^{[[k k]]} | |}}}}}} - - - - - - ((1616))$

R^*表示选定的中继，m表示第m个中继，m∈{1,…N}；i对应两个源节点，i∈{1,2}；k表示第k个子载波，k∈{1,…K}；I₂表示FNS-J方法使用的子载波集合，表示从S_i到R_m使用的子载波信道在第k个子载波上增益的模值。R ^* represents the selected relay, m represents the mth relay, m∈{1,…N}; i corresponds to two source nodes, i∈{1,2}; k represents the kth subcarrier, k∈ {1,...K}; I ₂ represents the set of subcarriers used by the FNS-J method, Indicates the modulus of the gain of the subcarrier channel used from S _i to R _m on the kth subcarrier.

FNS-J中，不论Q值是大还是小，每个中继都要进行子载波抑制，所以每个中继使用的子载波的最小的信道增益是不同的。在这种情况下进行中继选择，系统的性能得到明显改善。In FNS-J, regardless of whether the Q value is large or small, each relay must perform subcarrier suppression, so the minimum channel gain of each subcarrier used by each relay is different. In this case, relay selection is carried out, and the performance of the system is obviously improved.

进一步的，中继物理层网络编码方法包括以下步骤：Further, the relay physical layer network coding method includes the following steps:

根据译码转发方式，采用最大似然译码；选定的中继首先要计算在多址接入时隙X₁是c,X₂是d的概率对于BPSK调制，c∈{+1,-1},d∈{+1,-1}：According to the decoding and forwarding method, the maximum likelihood decoding is adopted; the selected relay first needs to calculate the probability that X ₁ is c and X ₂ is d in the multiple access time slot For BPSK modulation, c∈{+1,-1},d∈{+1,-1}:

${P P}_{m m}^{[[k k]]} ((+ + 11,, + + 11)) &Proportional; &Proportional; exp exp ((- - \frac{| | {Y Y}_{{R R}_{m m}} [[k k]] - - {\overset{^^}{H h}}_{11 m m}^{[[k k]]} - - {\overset{^^}{H h}}_{22 m m}^{[[k k]]} {| |}^{22}}{{σ σ}^{22}}))$

${P P}_{m m}^{[[k k]]} ((- - 11,, - - 11)) &Proportional; &Proportional; exp exp ((- - \frac{| | {Y Y}_{{R R}_{m m}} [[k k]] + + {\overset{^^}{H h}}_{11 m m}^{[[k k]]} + + {\overset{^^}{H h}}_{22 m m}^{[[k k]]} {| |}^{22}}{{σ σ}^{22}}))$

(17)(17)

${P P}_{m m}^{[[k k]]} ((+ + 11,, - - 11)) &Proportional; &Proportional; exp exp ((- - \frac{| | {Y Y}_{{R R}_{m m}} [[k k]] - - {\overset{^^}{H h}}_{11 m m}^{[[k k]]} + + {\overset{^^}{H h}}_{22 m m}^{[[k k]]} {| |}^{22}}{{σ σ}^{22}}))$

${P P}_{m m}^{[[k k]]} ((- - 11,, + + 11)) &Proportional; &Proportional; exp exp ((- - \frac{| | {Y Y}_{{R R}_{m m}} [[k k]] + + {\overset{^^}{H h}}_{11 m m}^{[[k k]]} - - {\overset{^^}{H h}}_{22 m m}^{[[k k]]} {| |}^{22}}{{σ σ}^{22}}$

其中，表示的估计值，σ²表示噪声方差；然后，选定的中继接收到S₁,S₂发送的信息后对其进行网络编码，用来表示进行网络编码后得到的信息，则有：in, express The estimated value of , σ ² represents the noise variance; then, the selected relay receives the information sent by S ₁ , S ₂ Then network encode it with To represent The information obtained after network coding is:

${A A}_{{R R}_{m m}}^{[[k k]]} = = \{\begin{matrix} 00,, & i i f f & {P P}_{m m}^{[[k k]]} ((+ + 11,, + + 11)) + + {P P}_{{R R}_{m m}} [[k k]] ((- - 11,, - - 11)) &GreaterEqual; &Greater Equal; {P P}_{m m}^{[[k k]]} ((+ + 11,, - - 11)) + + {P P}_{{R R}_{m m}} [[k k]] ((- - 11,, + + 11)) \\ 11,, & i i f f & {P P}_{m m}^{[[k k]]} ((+ + 11,, + + 11)) + + {P P}_{{R R}_{m m}} [[k k]] ((- - 11,, - - 11)) < < {P P}_{m m}^{[[k k]]} ((+ + 11,, - - 11)) + + {P P}_{{R R}_{m m}} [[k k]] ((- - 11,, + + 11)) \end{matrix} - - - - - - ((1818))$

经过BPSK调制后可以写成选定的中继再把广播给S₁,S₂；第三步，S₁,S₂接收选定的中继广播来的信息，用表示；均衡后的结果用表示， After BPSK modulation, it can be written as selected relay broadcast to S ₁ , S ₂ ; in the third step, S ₁ , S ₂ receive the information broadcast by the selected relay, and use express; The result after equalization is express,

则有：Then there are:

${M m}_{{S S}_{11}}^{[[k k]]} = = {Y Y}_{{S S}_{11}}^{[[k k]]} / / {H h}_{11 m m}^{[[k k]]} - - - - - - ((1919))$

${M m}_{{S S}_{22}}^{[[k k]]} = = {Y Y}_{{S S}_{22}}^{[[k k]]} / / {H h}_{22 m m}^{[[k k]]} - - - - - - ((2020))$

最后，S₁,S₂根据如下方法解调接收到的信息：Finally, S ₁ and S ₂ demodulate the received information according to the following method:

${B B}_{{S S}_{11}}^{[[k k]]} = = \{\begin{matrix} 00,, & i i f f & {M m}_{{S S}_{11}}^{[[k k]]} < < 00 \\ 11,, & i i f f & {M m}_{{S S}_{11}}^{[[k k]]} &GreaterEqual; &Greater Equal; 00 \end{matrix} - - - - - - ((21 twenty one))$

${B B}_{{S S}_{22}}^{[[k k]]} = = \{\begin{matrix} 00,, & i i f f & {M m}_{{S S}_{22}}^{[[k k]]} < < 00 \\ 11,, & i i f f & {M m}_{{S S}_{22}}^{[[k k]]} &GreaterEqual; &Greater Equal; 00 \end{matrix} - - - - - - ((22 twenty two))$

其中，表示S_i解调后的结果，i∈{1,2}；综上，S₁的接收信号S₂的接收信号为：in, Indicates that S _i demodulates The final result, i∈{1,2}; in summary, the received signal of S ₁ Received signal of S ₂ for:

${A A}_{22}^{[[k k]]} = = {A A}_{11}^{[[k k]]} &CirclePlus; &CirclePlus; {B B}_{{S S}_{11}}^{[[k k]]} - - - - - - ((23 twenty three))$

${A A}_{11}^{[[k k]]} = = {A A}_{22}^{[[k k]]} &CirclePlus; &CirclePlus; {B B}_{{S S}_{22}}^{[[k k]]} - - - - - - ((24 twenty four)) . .$

本发明研究了PLNC-OFDM双向多中继系统中的联合子载波抑制与中继选择(JointSubcarriersSuppressionandRelaySelection，JSSRS)问题，实现了既降低系统误比特率又提高系统吞吐量的目标。本发明核心思想即将子载波抑制技术应用到OFDM双向多中继系统中，结合中继选择技术，提出了两种JSSRS方法：固定抑制门限的JSSRS(FixThresholdbasedJSSRS,FT-J)和固定子载波个数的JSSRS(FixNumberofSubcarriersbasedJSSRS,FNS-J)。FT-J在一次双向信息交换过程中采用固定的抑制门限进行子载波抑制；FNS-J在一次双向信息交换过程中保持抑制的子载波个数恒定不变，即活跃子载波个数恒定不变而抑制门限动态变化。The invention studies the Joint Subcarrier Suppression and Relay Selection (JSSRS) problem in the PLNC-OFDM two-way multi-relay system, and realizes the goal of reducing the system bit error rate and improving the system throughput. The core idea of the present invention is to apply the subcarrier suppression technology to the OFDM two-way multi-relay system. Combined with the relay selection technology, two JSSRS methods are proposed: JSSRS (FixThresholdbasedJSSRS, FT-J) with a fixed suppression threshold and a fixed number of subcarriers JSSRS (FixNumber of Subcarriers based JSSRS, FNS-J). FT-J uses a fixed suppression threshold for subcarrier suppression during a two-way information exchange; FNS-J keeps the number of suppressed subcarriers constant during a two-way information exchange, that is, the number of active subcarriers remains constant And the suppression threshold changes dynamically.

本发明将子载波抑制技术和中继选择技术结合，提出FT-J和FNS-J两种方法。与传统的子载波抑制相比，本发明提出的FT-J和FNS-J不仅进一步提高系统的吞吐量性能还提高系统误比特率性能。在误比特率性能方面，FT-J在抑制门限比较高时，增加中继个数并不能进一步降低系统误比特率；而FNS-J在使用的子载波个数比较少时，增加中继个数仍然能够进一步降低系统误比特率。在吞吐量性能方面，随着中继个数的增多，FNS-J的吞吐量增加，但不会超过使用的子载波个数Q；而FT-J的吞吐量随着中继个数增加不断增加，在中继个数足够多的情况下可以逼近系统的极限吞入量。The invention combines the subcarrier suppression technology and the relay selection technology, and proposes two methods, FT-J and FNS-J. Compared with the traditional subcarrier suppression, the FT-J and FNS-J proposed by the present invention not only further improve the throughput performance of the system but also improve the bit error rate performance of the system. In terms of bit error rate performance, when the suppression threshold of FT-J is relatively high, increasing the number of relays cannot further reduce the system bit error rate; while FNS-J uses a relatively small number of subcarriers, increasing the number of relays It is still possible to further reduce the system bit error rate. In terms of throughput performance, as the number of relays increases, the throughput of FNS-J increases, but will not exceed the number of subcarriers Q used; while the throughput of FT-J increases continuously with the number of relays. Increase, when the number of relays is large enough, it can approach the limit throughput of the system.

综上所述，与传统的子载波抑制相比，本发明提出的FT-J和FNS-J不仅增强了系统可靠性，而且提高了系统有效性。在系统可靠性和有效性方面FT-J和FNS-J各有优势。在实际应用场景中，使用哪种方法更合适，取决于系统的要求。当系统要求较高的数据速率时，可选用FT-J；当系统的主要目标是可靠性时，可选用FNS-J。In summary, compared with traditional subcarrier suppression, FT-J and FNS-J proposed by the present invention not only enhance system reliability, but also improve system effectiveness. FT-J and FNS-J have their own advantages in terms of system reliability and effectiveness. In actual application scenarios, which method is more appropriate depends on the requirements of the system. When the system requires a higher data rate, FT-J can be selected; when the main goal of the system is reliability, FNS-J can be selected.

附图说明Description of drawings

图1是本发明的实现框图。Fig. 1 is a realization block diagram of the present invention.

图2是本发明的双向OFDM多中继系统示意图。Fig. 2 is a schematic diagram of the bidirectional OFDM multi-relay system of the present invention.

图3是本发明的子载波抑制示意图。Fig. 3 is a schematic diagram of subcarrier suppression in the present invention.

图4是本发明的FT-J和FNS-J的误比特率性能图Q＝55，λ＝0.0758。Fig. 4 is a bit error rate performance diagram of FT-J and FNS-J of the present invention Q=55, λ=0.0758.

图5是本发明的FNS-J随使用的子载波个数变化的误比特率性能图，SNR＝10dB。Fig. 5 is a bit error rate performance diagram of the FNS-J of the present invention as the number of subcarriers used changes, SNR = 10dB.

图6是本发明的FT-J随抑制门限变化的误比特率性能图，SNR＝10dB。Fig. 6 is a bit error rate performance diagram of the FT-J of the present invention as the suppression threshold changes, SNR=10dB.

图7是本发明的FT-J和FNS-J随中继个数变化的误比特率性能图，SNR＝10dB。Fig. 7 is a bit error rate performance diagram of FT-J and FNS-J according to the present invention as the number of relays changes, SNR=10dB.

图8是本发明的FT-J和FNS-J的吞吐量性能图，Q＝55，λ＝0.0758。Fig. 8 is the throughput performance diagram of FT-J and FNS-J of the present invention, Q=55, λ=0.0758.

图9是本发明的FNS-J随使用的子载波个数变化的吞吐量性能图，SNR＝10dB。Fig. 9 is a graph of the throughput performance of FNS-J according to the present invention as the number of subcarriers used changes, SNR=10dB.

图10是本发明的FT-J随抑制门限变化的吞吐量性能图，SNR＝10dB。Fig. 10 is a graph of the throughput performance of the FT-J of the present invention as the suppression threshold changes, SNR=10dB.

图11是本发明的FT-J和FNS-J随中继个数变化的吞吐量性能图，SNR＝10dB。Fig. 11 is a throughput performance diagram of FT-J and FNS-J according to the present invention as the number of relays changes, SNR=10dB.

下面结合附图及具体实施例对本发明的具体实施方式作进一步描述。The specific implementation manner of the present invention will be further described below in conjunction with the accompanying drawings and specific examples.

具体实施方式detailed description

为了使本发明的目的、技术方案及优点更加清楚明白，以下结合实施例，对本发明进行进一步详细说明。应当理解，此处所描述的具体实施例仅仅用以解释本发明，并不用于限定本发明。In order to make the object, technical solution and advantages of the present invention more clear, the present invention will be further described in detail below in conjunction with the examples. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

实施例1Example 1

本基于PLNC的双向OFDM多中继系统中的联合子载波抑制与中继选择方法，包括以下步骤：The joint subcarrier suppression and relay selection method in the bidirectional OFDM multi-relay system based on PLNC comprises the following steps:

基于TDMA的双向多中继系统由N个中继节点{R₁,R₂,…R_N}和两个源节点S₁,S₂构成，所有节点均配备单根天线并工作在半双工模式，如图1所示。S₁知道S₁到每一个中继节点之间的信道状态信息；S₂知道S₂到每一个中继节点之间的信道状态信息。基于TDMA的双向多中继系统采用OFDM传输方式，子载波个数用K表示，子载波调制方式为BPSK。S₁,S₂到中继节点的信道是多径瑞利衰落信道，用向量h_i表示：A two-way multi-relay system based on TDMA consists of N relay nodes {R ₁ , R ₂ ,…R _N } and two source nodes S ₁ , S ₂ , all nodes are equipped with a single antenna and work in half-duplex mode, as shown in Figure 1. S ₁ knows the channel state information between S ₁ and each relay node; S ₂ knows the channel state information between S ₂ and each relay node. The two-way multi-relay system based on TDMA adopts the OFDM transmission mode, the number of subcarriers is represented by K, and the subcarrier modulation method is BPSK. The channel from S ₁ , S ₂ to the relay node is a multipath Rayleigh fading channel, represented by vector h _i :

h_i＝[h_i[0],h_i[1],…,h_i[L-1]]^Ti＝1,2h _i ＝[h _i [0],h _i [1],…,h _i [L-1]] ^T i=1,2

其中，L表示路径数。S₁,S₂到中继节点的信道独立同分布，在第k个子载波上的频域信道为H_i[k]：in, L represents the number of paths. The channel from S ₁ , S ₂ to the relay node is independent and identically distributed, and the frequency domain channel on the kth subcarrier is H _i [k]:

${H h}_{i i} [[k k]] = = {Σ Σ}_{l l = = 00}^{L L - - 11} {h h}_{i i} {[[l l]]}^{- - 22 j j π π \frac{k k}{K K} l l},, i i = = 11,, 22$

每一次的信息交换可以分为两个阶段：多址接入阶段和广播阶段。Each information exchange can be divided into two phases: the multiple access phase and the broadcast phase.

多址接入阶段：首先，S₁,S₂在第k个子载波上分别需要发送信息然后，信息经过BPSK调制后可以表示成最后，S₁,S₂把信息发送给所有的中继节点。第m个中继的第k个子载波上的接收信号可以表示为：Multiple access stage: First, S ₁ and S ₂ need to send information on the kth subcarrier respectively Then, the information After BPSK modulation, it can be expressed as Finally, S ₁ , S ₂ put the information sent to all relay nodes. The received signal on the kth subcarrier of the mth relay can be expressed as:

${Y Y}_{{R R}_{m m}}^{[[k k]]} = = {H h}_{11 m m}^{[[k k]]} {X x}_{11}^{[[k k]]} + + {H h}_{22 m m}^{[[k k]]} {X x}_{22}^{[[k k]]} + + {N N}_{{R R}_{m m}}^{[[k k]]}$

表示从S_i到R_m之间多径瑞利衰落信道在第k个子载波上的增益，m∈{1,…N}，k∈{1,…K}，i∈{1,2}，且从S₁,S₂到中继节点和中继节点到S₁,S₂的信道是相同的。表示加性高斯白噪声。 Represents the gain of the multipath Rayleigh fading channel from S _i to R _m on the kth subcarrier, m∈{1,…N}, k∈{1,…K}, i∈{1,2}, And the channels from S ₁ , S ₂ to the relay node and from the relay node to S ₁ , S ₂ are the same. Represents additive white Gaussian noise.

${Y Y}_{{S S}_{11}}^{[[k k]]} = = {H h}_{11 m m}^{[[k k]]} {X x}_{{R R}_{m m}}^{[[k k]]} + + {N N}_{11}^{[[k k]]}$

${Y Y}_{{S S}_{22}}^{[[k k]]} = = {H h}_{22 m m}^{[[k k]]} {X x}_{{R R}_{m m}}^{[[k k]]} + + {N N}_{22}^{[[k k]]}$

表示中继节点网络编码得到的信息经过BPSK调制后得到的信息，表示源节点S_i接收到的信息，表示加性高斯白噪声，i∈{1,2}。 Indicates the information obtained by the network encoding of the relay node The information obtained after BPSK modulation, Indicates the information received by the source node S _i , Denotes additive white Gaussian noise, i ∈ {1,2}.

作为优选方案，PLNC的双向OFDM多中继系统中的联合子载波抑制与中继选择方法中的子载波抑制特征在于：As a preferred solution, the joint subcarrier suppression in the two-way OFDM multi-relay system of PLNC and the subcarrier suppression in the relay selection method are characterized by:

无线信道的多径传输特性会导致频率选择性衰落。在OFDM双向中继系统中，信道的频率选择性衰落会造成不同的子载波具有不同的信道增益。子载波抑制是仅利用信道条件好的子载波传输信息，而信道条件差的子载波放弃不用。用表示抑制门限，当子载波的信道增益高于时，我们定义该子载波为“活跃子载波”；反之，当子载波的信道增益低于时，我们定义该子载波为“抑制子载波”。每一个子载波是否是活跃可以用子载波状态表示如下：The multipath transmission characteristics of wireless channels can cause frequency selective fading. In the OFDM two-way relay system, the frequency selective fading of the channel will cause different subcarriers to have different channel gains. Subcarrier suppression is to use only subcarriers with good channel conditions to transmit information, while subcarriers with poor channel conditions are discarded. use Indicates the suppression threshold, when the channel gain of the subcarrier is higher than When , we define the subcarrier as an "active subcarrier"; otherwise, when the channel gain of the subcarrier is lower than , we define this subcarrier as a "suppressed subcarrier". Whether each subcarrier is active and available subcarrier status Expressed as follows:

${F f}_{i i m m}^{[[k k]]} = = \{\begin{matrix} 11,, & i i f f & | | {\overset{^^}{H h}}_{i i m m}^{[[k k]]} | | &GreaterEqual; &Greater Equal; {λ λ}_{00}^{i i} \\ 00,, & i i f f & | | {\overset{^^}{H h}}_{i i m m}^{[[k k]]} | | < < {λ λ}_{00}^{i i} \end{matrix},, i i = = 11,, 22$

“1”表示该子载波是活跃子载波；“0”表示该子载波是抑制子载波。表示从S_i到R_m之间多径瑞利衰落信道在第k个子载波上增益的估计值。只有在两个源节点之间都是“活跃子载波”时，该子载波才被中继用来传输信息，定义为“使用的子载波”。系统仅使用“使用的子载波”来传输信息而不使用被抑制的子载波。如图3所示，因此，第k个子载波是否被第m个中继使用可以用状态表示："1" indicates that the subcarrier is an active subcarrier; "0" indicates that the subcarrier is a suppressed subcarrier. Represents the estimated value of the gain on the kth subcarrier of the multipath Rayleigh fading channel from S _i to R _m . Only when there are "active subcarriers" between the two source nodes, the subcarriers are used by the relay to transmit information, which is defined as "used subcarriers". The system uses only "used subcarriers" to transmit information and not suppressed subcarriers. As shown in Figure 3, therefore, whether the kth subcarrier is used by the mth relay can be used express:

${F f}_{{R R}_{m m}}^{[[k k]]} = = {F f}_{11 m m}^{[[k k]]} {F f}_{22 m m}^{[[k k]]}$

作为优选方案，一种基于PLNC的双向OFDM多中继系统中的联合子载波抑制与中继选择方法中联合子载波抑制与中继选择方法特征在于：As a preferred solution, a joint subcarrier suppression and relay selection method in a PLNC-based two-way OFDM multi-relay system is characterized in that:

中继选择即在多中继系统中选择信道条件最好的一个中继来进行传输信息，本文根据最小最大原则选择一个中继：Relay selection is to select a relay with the best channel conditions to transmit information in a multi-relay system. In this paper, a relay is selected according to the minimum and maximum principle:

${R R}^{* *} = = arg arg \underset{m m}{max max} {{\underset{k k &Element; &Element; I I}{min min} {{\underset{i i}{min min} {{| | {H h}_{i i m m}^{[[k k]]} | |}}}}}}$

R^*表示选定的中继，m表示第m个中继，m∈{1,…N}；i对应两个源节点的编号，i∈{1,2}；k表示第k个子载波，k∈{1,…K}；I表示使用的子载波集合，表示从S_i到R_m之间多径瑞利衰落信道在第k个子载波上增益的模值。R ^* represents the selected relay, m represents the mth relay, m∈{1,…N}; i corresponds to the number of two source nodes, i∈{1,2}; k represents the kth subcarrier, k∈{1,…K}; I represents the set of subcarriers used, Indicates the modulus value of the gain on the kth subcarrier of the multipath Rayleigh fading channel from S _i to R _m .

根据子载波抑制方法不同，结合最小最大中继选择，本发明提出两种联合子载波抑制与中继选择方法：固定抑制门限的JSSRS方法(FT-J)、固定子载波个数的JSSRS方法(FNS-J)。According to different subcarrier suppression methods, combined with the minimum and maximum relay selection, the present invention proposes two joint subcarrier suppression and relay selection methods: the JSSRS method (FT-J) with a fixed suppression threshold, and the JSSRS method with a fixed number of subcarriers ( FNS-J).

作为优选方案，本基于PLNC的双向OFDM多中继系统中的联合子载波抑制与中继选择方法中固定抑制门限的JSSRS方法(FixThresholdbasedJSSRS,FT-J)特征在于：As a preferred solution, the JSSRS method (FixThresholdbasedJSSRS, FT-J) of the fixed suppression threshold in the joint subcarrier suppression and relay selection method in this PLNC-based two-way OFDM multi-relay system is characterized in that:

FT-J首先进行子载波抑制，然后在所有中继中选择一个信道条件最好的中继进行信息传输。在子载波抑制之前，S₁,S₂需要确定抑制门限λ₀。FT-J的λ₀值是S₁,S₂直接确定的一个常数，该常数在多址接入和广播两个时隙期间保持不变。S₁,S₂根据上述的子载波抑制方法对所有子载波进行抑制操作：FT-J performs subcarrier suppression first, and then selects a relay with the best channel conditions among all relays for information transmission. Before subcarrier suppression, S ₁ and S ₂ need to determine the suppression threshold λ ₀ . The λ ₀ value of FT-J is a constant directly determined by S ₁ and S ₂ , and the constant remains unchanged during the two time slots of multiple access and broadcast. S ₁ and S ₂ perform suppression operations on all subcarriers according to the above subcarrier suppression method:

${F f}_{11 i i m m}^{[[k k]]} = = \{\begin{matrix} 11,, & i i f f & | | {\overset{^^}{H h}}_{i i m m}^{[[k k]]} | | &GreaterEqual; &Greater Equal; {λ λ}_{00} \\ 00,, & i i f f & | | {\overset{^^}{H h}}_{i i m m}^{[[k k]]} | | < < {λ λ}_{00} \end{matrix},, i i = = 11,, 22$

${F f}_{11 {R R}_{m m}}^{[[k k]]} = = {F f}_{1111 m m}^{[[k k]]} {F f}_{1212 m m}^{[[k k]]}$

${H h}_{11 i i m m}^{[[k k]]} = = {F f}_{11 {R R}_{m m}}^{[[k k]]} \times \times {H h}_{i i m m}^{[[k k]]}$

表示S_i到中继之间的子载波状态，“1”表示该子载波是活跃子载波；“0”表示该子载波是抑制子载波。表示中继左右两边的子载波是否是“使用的子载波”，表示该子载波是“使用的子载波”，表示该子载波被放弃不用。表示经过子载波抑制之后各子载波的信道是否被使用。表示“使用的子载波”信道被使用，表示抑制子载波的信道放弃不用。 Indicates the subcarrier status between S _i and the relay, "1" indicates that the subcarrier is an active subcarrier; "0" indicates that the subcarrier is a suppressed subcarrier. Indicates whether the subcarriers on the left and right sides of the relay are "used subcarriers", Indicates that the subcarrier is the "used subcarrier", Indicates that the subcarrier is abandoned. Indicates whether the channel of each subcarrier is used after subcarrier suppression. Indicates that the "subcarrier used" channel is used, Indicates that the channel of the suppressed subcarrier is abandoned.

最后在所有中继中选择一个信道条件最好的中继进行信息传输。Finally, a relay with the best channel condition is selected among all relays for information transmission.

${R R}^{* *} = = arg arg \underset{m m}{max max} {{\underset{k k &Element; &Element; {I I}_{11}}{min min} {{\underset{i i}{min min} {{| | {H h}_{11 i i m m}^{[[k k]]} | |}}}}}}$

作为优选方案，本基于PLNC的双向OFDM多中继系统中的联合子载波抑制与中继选择方法中固定子载波个数的JSSRS(FixNumberofSubcarriersbasedJSSRS,FNS-J)方法特征在于：As a preferred solution, the JSSRS (FixNumberofSubcarriersbasedJSSRS, FNS-J) method of the fixed number of subcarriers in the joint subcarrier suppression and relay selection method in this PLNC-based two-way OFDM multi-relay system is characterized in that:

与FT-J类似，FNS-J首先进行子载波抑制，然后在所有中继中选择一个信道条件最好的中继进行信息传输。在子载波抑制之前，S₁,S₂需要确定抑制门限λ₀。与FT-J不同的是，FNS-J需要S₁,S₂首先确定使用的子载波的个数Q，Q是常数。根据常数Q来确定临时抑制门限，即S₁,S₂在所有K个子载波中选择信道条件最好的Q个子载波来传输信息(0＜Q≤K)，把第Q好的信道增益模制作为临时抑制门限，即对所有子载波进行抑制操作：Similar to FT-J, FNS-J performs subcarrier suppression first, and then selects a relay with the best channel conditions among all relays for information transmission. Before subcarrier suppression, S ₁ and S ₂ need to determine the suppression threshold λ ₀ . Different from FT-J, FNS-J requires S ₁ and S ₂ to first determine the number Q of subcarriers used, and Q is a constant. The temporary suppression threshold is determined according to the constant Q, that is, S ₁ and S ₂ select the Q subcarriers with the best channel conditions among all K subcarriers to transmit information (0<Q≤K), and model the Qth best channel gain as the temporary suppression threshold, that is Suppress all subcarriers:

${F f}_{22 i i m m}^{[[k k]]} = = \{\begin{matrix} 11,, & i i f f & | | {\overset{^^}{H h}}_{i i m m}^{[[k k]]} | | &GreaterEqual; &Greater Equal; | | {H h}_{i i n no}^{[[Q Q]]} | | \\ 00,, & i i f f & | | {\overset{^^}{H h}}_{i i m m}^{[[k k]]} | | < < | | {H h}_{i i m m}^{[[Q Q]]} | | \end{matrix},, i i = = 11,, 22$

${F f}_{22 {R R}_{m m}}^{[[k k]]} = = {F f}_{21 twenty one m m}^{[[k k]]} {F f}_{22 twenty two m m}^{[[k k]]}$

${H h}_{22 i i m m}^{[[k k]]} = = {F f}_{22 {R R}_{m m}}^{[[k k]]} \times \times {H h}_{i i m m}^{[[k k]]}$

表示S_i到中继之间的子载波状态，“1”表示该子载波是活跃子载波；“0”表示该子载波是抑制子载波。表示该子载波是否是“使用的子载波”，表示该子载波是“使用的子载波”，表示该子载波被放弃不用。表示经过子载波抑制各子载波的信道是否被使用。表示“使用的子载波”信道被使用，表示抑制子载波的信道放弃不用。 Indicates the subcarrier status between S _i and the relay, "1" indicates that the subcarrier is an active subcarrier; "0" indicates that the subcarrier is a suppressed subcarrier. Indicates whether this subcarrier is a "used subcarrier", Indicates that the subcarrier is the "used subcarrier", Indicates that the subcarrier is abandoned. Indicates whether the channel of each subcarrier is used through subcarrier suppression. Indicates that the "subcarrier used" channel is used, Indicates that the channel of the suppressed subcarrier is abandoned.

在多址接入和广播两个时隙期间，Q固定不变，而抑制门限动态变化。因此，同一个中继的两个抑制门限不相同；不同的中继这一门限值也不相同。最后在所有中继中选择一个信道条件最好的中继传输信息。During the two time slots of multiple access and broadcast, Q is fixed, while the suppression threshold changes dynamically. Therefore, two suppression thresholds for the same trunk Not the same; different relays have different thresholds. Finally, select a relay with the best channel condition to transmit information among all relays.

${R R}^{* *} = = arg arg \underset{m m}{max max} {{\underset{k k &Element; &Element; {I I}_{22}}{min min} {{\underset{i i}{min min} {{| | {H h}_{22 i i m m}^{[[k k]]} | |}}}}}}$

FNS-J中，不论Q值是大还是小，每个中继都要进行子载波抑制，所以每个中继使用的子载波的最小的信道增益是不同的。在这种情况下进行中继选择，系统的性能得到明显改善。In FNS-J, regardless of whether the Q value is large or small, each relay must perform subcarrier suppression, so the minimum channel gain of each subcarrier used by each relay is different. In this case, the relay selection is carried out, and the performance of the system is obviously improved.

作为优选方案，本基于PLNC的双向OFDM多中继系统中的联合子载波抑制与中继选择方法的中继译码方法特征在于：As a preferred solution, the relay decoding method of the joint subcarrier suppression and relay selection method in this PLNC-based two-way OFDM multi-relay system is characterized in that:

根据译码转发方式，采用最大似然译码。选定的中继首先要计算在多址接入时隙X₁是c,X₂是d的概率 $P_{m}^{[k]} (c, d), c &Element; {+ 1, - 1}, d &Element; {+ 1, - 1} :$ According to the decoding and forwarding mode, the maximum likelihood decoding is adopted. The selected relay first calculates the probability that X ₁ is c and X ₂ is d in the multiple access slot $P_{m}^{[k]} (c, d), c &Element; {+ 1, - 1}, d &Element; {+ 1, - 1} :$

其中，表示的估计值，σ²表示噪声方差。然后，选定的中继接收到S₁,S₂发送的信息后对其进行网络编码，用来表示进行网络编码后得到的信息，则有：in, express The estimated value of , σ ² represents the noise variance. Then, the selected relay receives the information sent by S ₁ , S ₂ Then network encode it with To represent The information obtained after network coding is:

${A A}_{{R R}_{m m}}^{[[k k]]} = = \{\begin{matrix} 00,, & i i f f & {P P}_{m m}^{[[k k]]} ((+ + 11,, + + 11)) + + {P P}_{{R R}_{m m}} [[k k]] ((- - 11,, - - 11)) &GreaterEqual; &Greater Equal; {P P}_{m m}^{[[k k]]} ((+ + 11,, - - 11)) + + {P P}_{{R R}_{m m}} [[k k]] ((- - 11,, + + 11)) \\ 11,, & i i f f & {P P}_{m m}^{[[k k]]} ((+ + 11,, + + 11)) + + {P P}_{{R R}_{m m}} [[k k]] ((- - 11,, - - 11)) < < {P P}_{m m}^{[[k k]]} ((+ + 11,, - - 11)) + + {P P}_{{R R}_{m m}} [[k k]] ((- - 11,, + + 11)) \end{matrix}$

经过BPSK调制后可以写成选定的中继再把广播给S₁,S₂。第三步，S₁,S₂接收选定的中继广播来的信息，用表示。均衡后的结果用表示， After BPSK modulation, it can be written as selected relay Broadcast to S ₁ , S ₂ . In the third step, S ₁ and S ₂ receive the information broadcast by the selected relay, and use express. The result after equalization is express,

则有：Then there are:

${M m}_{{S S}_{11}}^{[[k k]]} = = {Y Y}_{{S S}_{11}}^{[[k k]]} / / {H h}_{11 m m}^{[[k k]]}$

${M m}_{{S S}_{22}}^{[[k k]]} = = {Y Y}_{{S S}_{22}}^{[[k k]]} / / {H h}_{22 m m}^{[[k k]]}$

${B B}_{{S S}_{11}}^{[[k k]]} = = \{\begin{matrix} 00,, & i i f f & {M m}_{{S S}_{11}}^{[[k k]]} < < 00 \\ 11,, & i i f f & {M m}_{{S S}_{11}}^{[[k k]]} &GreaterEqual; &Greater Equal; 00 \end{matrix}$

${B B}_{{S S}_{22}}^{[[k k]]} = = \{\begin{matrix} 00,, & i i f f & {M m}_{{S S}_{22}}^{[[k k]]} < < 00 \\ 11,, & i i f f & {M m}_{{S S}_{22}}^{[[k k]]} &GreaterEqual; &Greater Equal; 00 \end{matrix}$

其中，表示S_i解调后的结果，i∈{1,2}。综上，S₁的接收信号S₂的接收信号为：in, Indicates that S _i demodulates The final result, i∈{1,2}. In summary, the received signal of S ₁ Received signal of S ₂ for:

${A A}_{22}^{[[k k]]} = = {A A}_{11}^{[[k k]]} &CirclePlus; &CirclePlus; {B B}_{{S S}_{11}}^{[[k k]]}$

${A A}_{11}^{[[k k]]} = = {A A}_{22}^{[[k k]]} &CirclePlus; &CirclePlus; {B B}_{{S S}_{22}}^{[[k k]]}$

仿真结果Simulation results

包含N个中继的OFDM双向中继系统中两种JSSRS方法在误比特率和吞吐量性能方面的仿真结果。源节点和中继节点的发送功率设为1、子载波个数K＝64、循环前缀长度为16、无线多径信道建模为4径独立同分布的瑞利信道。在整个仿真过程中，抑制门限用λ表示，两个源节点使用的子载波个数相同，为 $Q_{0}^{1} = Q_{0}^{2} = Q .$ Simulation results of two JSSRS methods in terms of bit error rate and throughput performance in an OFDM bidirectional relay system with N relays. The transmit power of the source node and the relay node is set to 1, the number of subcarriers is K=64, the length of the cyclic prefix is 16, and the wireless multipath channel is modeled as a 4-path independent and identically distributed Rayleigh channel. In the whole simulation process, the suppression threshold is denoted by λ, and the number of subcarriers used by the two source nodes is the same, which is $Q_{0}^{1} = Q_{0}^{2} = Q .$

(1)误比特率(BitErrorRate，BER)性能仿真结果(1) Bit Error Rate (BitErrorRate, BER) performance simulation results

图4给出FT-J和FNS-J的误比特率性能曲线。FT-J和FNS-J结合了子载波抑制和中继选择两者的优点，而传统子载波抑制仅仅发挥子载波抑制一个方面的优点。如图4所示，基于PLNC的OFDM双向多中继系统中FT-J和FNS-J的误比特性能都优于传统的子载波抑制。图5给出不同使用的子载波个数条件下FNS-J的误比特率性能曲线。如图5所示，使用的子载波个数越少，使用的子载波的整体信道状态越好，误比特率越低；中继个数越多，选中的中继的信道状态越好，误比特率越低。并且，当使用的子载波个数降低时，中继选择的优越性能够得到更大的发挥，FNS-J系统性能增益升高。图6给出不同抑制门限条件下FT-J的误比特率性能曲线。如图6所示，抑制门限越高，使用的子载波的整体信道状态越好，误比特率越低；中继个数越多，选中的中继的信道状态越好，误比特率越低。并且，当抑制门限升高时，中继选择优越性的发挥受到限制，FT-J系统性能增益降低。图5、图6中，SNR＝10dB。Figure 4 shows the bit error rate performance curves of FT-J and FNS-J. FT-J and FNS-J combine the advantages of subcarrier suppression and relay selection, while traditional subcarrier suppression only takes advantage of one aspect of subcarrier suppression. As shown in Fig. 4, the bit error performance of FT-J and FNS-J in PLNC-based OFDM two-way multi-relay system is better than traditional subcarrier suppression. Fig. 5 shows the bit error rate performance curve of FNS-J under the condition of different numbers of subcarriers used. As shown in Figure 5, the less the number of subcarriers used, the better the overall channel state of the used subcarriers, and the lower the bit error rate; the more the number of relays, the better the channel state of the selected relays, and the lower the bit error rate. The lower the bitrate. Moreover, when the number of sub-carriers used is reduced, the superiority of relay selection can be brought into full play, and the performance gain of the FNS-J system increases. Figure 6 shows the bit error rate performance curve of FT-J under different suppression threshold conditions. As shown in Figure 6, the higher the suppression threshold, the better the overall channel status of the subcarriers used, and the lower the bit error rate; the more the number of relays, the better the channel status of the selected relays, and the lower the bit error rate . Moreover, when the suppression threshold increases, the superiority of relay selection is limited, and the performance gain of the FT-J system decreases. In Fig. 5 and Fig. 6, SNR=10dB.

图7给出不同中继个数条件下FT-J和FNS-J的误比特率性能。图7中，SNR＝10dB。如图7所示，中继个数越多，误比特率越低；使用的子载波个数越少，误比特率越低；抑制门限越高，误比特率越低。并且，FT-J在抑制门限比较高时，增加中继个数并不能进一步降低系统误比特率；在抑制门限比较高时，FT-J方法中所有中继的子载波都经历子载波抑制，他们使用的子载波的最小信道增益几乎是相同的，在这种情况下，再进行最小最大中继选择后，系统性能不能得到改善。而FNS-J在使用的子载波个数比较少时，增加中继个数仍然能够进一步降低系统误比特率。FNS-J不论使用的子载波个数是多还是少，所有中继的子载波都是从上到下选择信道条件最好的子载波，其使用的子载波的最小信道增益依旧不同，故再进行最小最大中继选择后，系统性能仍能得到改善。因此，FNS-J的误比特率性能优于FT-J。Figure 7 shows the bit error rate performance of FT-J and FNS-J under the condition of different relay numbers. In Fig. 7, SNR=10dB. As shown in Figure 7, the larger the number of relays, the lower the bit error rate; the smaller the number of subcarriers used, the lower the bit error rate; the higher the suppression threshold, the lower the bit error rate. Moreover, when the suppression threshold of FT-J is relatively high, increasing the number of relays cannot further reduce the system bit error rate; when the suppression threshold is relatively high, all subcarriers of the relays in the FT-J method undergo subcarrier suppression, The minimum channel gains of the subcarriers they use are almost the same, in this case, the system performance cannot be improved after the min-max relay selection. However, when the number of subcarriers used by FNS-J is relatively small, increasing the number of relays can still further reduce the system bit error rate. Regardless of the number of subcarriers used by FNS-J, all relay subcarriers select the subcarriers with the best channel conditions from top to bottom, and the minimum channel gains of the subcarriers used are still different. System performance can still be improved after min-max relay selection. Therefore, the BER performance of FNS-J is better than that of FT-J.

吞吐量性能仿真结果Throughput Performance Simulation Results

本发明中的吞吐量定义为在一个时隙内能够正确传输的比特数：Throughput in the present invention is defined as the number of bits that can be correctly transmitted in a time slot:

$T T = = \frac{S S u u m m - - Z Z}{22}$

其中，T表示吞吐量，单位为bit/pertimeslot,Sum表示两个时隙内传输的总的比特数，Z表示两个时隙内传输错误的比特数。如果使用的子载波个数Q＝K＝64，即所有子载波全部使用并且没有噪声干扰，则系统的极限吞吐量是：Wherein, T represents the throughput, and the unit is bit/pertimeslot, Sum represents the total number of bits transmitted in two time slots, and Z represents the number of wrong bits transmitted in two time slots. If the number of subcarriers used is Q=K=64, that is, all subcarriers are used without noise interference, then the ultimate throughput of the system is:

${T T}_{m m a a x x} = = \frac{K K}{22} = = 3232$

图8比较FT-J和FNS-J的吞吐量性能。如图8所示，在低信噪比条件下，FT-J和FNS-J结合了子载波抑制和中继选择两者的优点，而传统子载波抑制仅仅发挥子载波抑制一个方面的优点，故FT-J和FNS-J的吞吐量性能都优于传统的子载波抑制；在高信噪比条件下，吞吐量性能达到一个性能增益平台，且FT-J吞吐量性能优于传统的子载波抑制，而FNS-J的吞吐量性能和传统的子载波抑制相同。Figure 8 compares the throughput performance of FT-J and FNS-J. As shown in Figure 8, under low SNR conditions, FT-J and FNS-J combine the advantages of subcarrier suppression and relay selection, while traditional subcarrier suppression only takes advantage of one aspect of subcarrier suppression. Therefore, the throughput performance of FT-J and FNS-J is better than that of traditional subcarrier suppression; under the condition of high SNR, the throughput performance reaches a performance gain platform, and the throughput performance of FT-J is better than that of traditional subcarrier suppression. Carrier suppression, while the throughput performance of FNS-J is the same as conventional subcarrier suppression.

图9给出了不同使用的子载波个数条件下FNS-J的吞吐量性能曲线，图10给出了不同抑制门限条件下FT-J的吞吐量性能曲线。图9、10中，SNR＝10dB。如图9所示，使用的子载波个数增加，每一个时隙传输的总比特数增加，吞吐量增加；中继个数增加，系统误比特率降低，故吞吐量增加。如图10所示，抑制门限增高，使用的子载波个数降低，每一个时隙传输的总比特数降低，故吞吐量降低；中继个数增加，系统误比特率降低，故吞吐量增加。图8中使用的子载波个数和吞吐量之间是线性关系。图10中，随着中继个数增多，抑制门限和使用的子载波个数之间不再是线性关系，故抑制门限和吞吐量之间的线性关系发生改变。Figure 9 shows the throughput performance curve of FNS-J under the condition of different numbers of sub-carriers used, and Figure 10 shows the throughput performance curve of FT-J under the condition of different suppression thresholds. In Figures 9 and 10, SNR=10dB. As shown in FIG. 9 , as the number of subcarriers used increases, the total number of bits transmitted in each time slot increases, and the throughput increases; the number of relays increases, and the bit error rate of the system decreases, so the throughput increases. As shown in Figure 10, the suppression threshold increases, the number of subcarriers used decreases, and the total number of bits transmitted in each time slot decreases, so the throughput decreases; the number of relays increases, the system bit error rate decreases, so the throughput increases . There is a linear relationship between the number of subcarriers used in FIG. 8 and the throughput. In FIG. 10 , as the number of relays increases, the linear relationship between the suppression threshold and the number of subcarriers used is no longer linear, so the linear relationship between the suppression threshold and the throughput changes.

图11给出了在相同信噪比条件下随着中继个数的增加FT-J和FNS-J的吞吐量性能。如图11所示，FNS-J随着使用的子载波个数增加，系统吞吐量增加；FT-J随着抑制门限的降低，系统吞吐量增加。随着中继个数的增多，FNS-J的吞吐量增加，但因为使用的子载波个数固定不变，每一个时隙传输的总比特数不变，故FNS-J的吞吐量最大不会超过使用的子载波个数Q；然而FT-J的吞吐量随着中继个数增加而不断增加，在中继个数足够多的情况下，中继选择的优越性发挥到极致，系统误比特率极低，可以逼近系统的极限吞入量。因此，FT-J的吞吐量性能优于FNS-J。Figure 11 shows the throughput performance of FT-J and FNS-J as the number of relays increases under the same SNR condition. As shown in Figure 11, FNS-J increases the system throughput as the number of subcarriers used increases; FT-J increases the system throughput as the suppression threshold decreases. As the number of relays increases, the throughput of FNS-J increases, but because the number of subcarriers used is fixed and the total number of bits transmitted in each time slot remains unchanged, the maximum throughput of FNS-J is not It will exceed the number Q of subcarriers used; however, the throughput of FT-J increases with the increase of the number of relays. When the number of relays is large enough, the superiority of relay selection is maximized, and the system The bit error rate is extremely low, which can approach the limit throughput of the system. Therefore, the throughput performance of FT-J is better than that of FNS-J.

Claims

1. A joint subcarrier suppression and relay selection method in a bidirectional OFDM multi-relay system based on PLNC is characterized by comprising the following steps:

the TDMA-based bidirectional multi-relay system consists of N relay nodes { R₁,R₂,…R_NAnd two source nodes S₁,S₂All nodes are provided with a single antenna and work in a half-duplex mode; s₁Knowing S₁Channel state information to each relay node; s₂Knowing S₂Channel shape to each relay nodeState information; the TDMA-based bidirectional multi-relay system adopts an OFDM transmission mode, and the number of subcarriers is represented by K; s₁,S₂The channel to the relay node is a multipath Rayleigh fading channel with a vector h_iRepresents:

h_i＝[h_i[0],h_i[1],…,h_i[L-1]]^Ti＝1,2(1)

wherein,l is 0,1, …, L-1, L indicates the number of paths; s₁,S₂The channels to the relay node are independently and equally distributed, and the frequency domain channel on the k sub-carrier is H_i[k]：

H_{i} [k] = Σ_{l = 0}^{L - 1} h_{i} [l] e^{- 2 j π \frac{k}{K} l}, i = 1, 2 - - - (2)

Each information exchange can be divided into two phases: multiple access phase and broadcast phase:

a multiple access stage: first, S₁,S₂Information is required to be transmitted on the k sub-carriers respectivelyThen, the informationAfter modulation can be expressed asFinally, S₁,S₂Handle informationSending the information to all relay nodes; the received signal on the k subcarrier of the mth relay may be represented as:

Y_{R_{m}}^{[k]} = H_{1 m}^{[k]} X_{1}^{[k]} + H_{2 m}^{[k]} X_{2}^{[k]} + N_{R_{m}}^{[k]} - - - (3)

denotes from S_iTo R_mThe gain of the multipath Rayleigh fading channel on the K-th subcarrier, m ∈ {1, … N }, K ∈ {1, … K }, i ∈ {1,2}, and from S₁,S₂To relay node and relay node to S₁,S₂Are the same;representing additive white gaussian noise;

and (3) a broadcasting stage: first, S₁,S₂Selecting a relay with the best channel state from all relays; then, the selected relay broadcasts the received information to S by using a decoding and forwarding mode₁,S₂(ii) a Finally, S₁,S₂The received information may be represented as follows:

Y_{S_{1}}^{[k]} = H_{1 m}^{[k]} X_{R_{m}}^{[k]} + N_{1}^{[k]} - - - (4)

Y_{S_{2}}^{[k]} = H_{2 m}^{[k]} X_{R_{m}}^{[k]} + N_{2}^{[k]} - - - (5)

representing information encoded by a relay node networkThe information obtained after the modulation is used for the modulation,representing a source node S_iThe information received is transmitted to the mobile station by the mobile station,representing additive white gaussian noise, i ∈ {1,2 }.

2. The method of claim 1 for joint subcarrier suppression and relay selection in a PLNC-based bi-directional OFDM multi-relay system, wherein subcarrier suppression comprises the steps of:

in a TDMA-based two-way multi-relay system, the frequency selective fading of the channel causes different subcarriers to have different channel gains, subcarrier suppression is to transmit information by using only subcarriers with good channel conditions, while subcarriers with poor channel conditions are abandoned and usedIndicating a suppression threshold when the channel gain of the subcarrier is aboveThen, the sub-carrier is defined as an "active sub-carrier"; conversely, when the channel gain of the sub-carrier is lower thanThen, the subcarrier is defined as a "suppression subcarrier"; subcarrier status for whether each subcarrier is active or notIs represented as follows:

F_{i m}^{[k]} = \{\begin{matrix} 1, & i f & | {\hat{H}}_{i m}^{[k]} | &GreaterEqual; λ_{0}^{i} \\ 0, & i f & | {\hat{H}}_{i m}^{[k]} | < λ_{0}^{i} \end{matrix}, i = 1, 2 - - - (6)

"1" indicates that the subcarrier is an active subcarrier; "0" indicates that the subcarrier is a suppression subcarrier;denotes from S_iTo R_mThe gain estimation value of the multi-path Rayleigh fading channel on the kth subcarrier; only if there is an "active subcarrier" between two source nodes, that subcarrier is relayed for information, defined as the "used subcarrier"; the system transmits information using only the "used subcarriers" without using the suppressed subcarriers; therefore, the state whether the k-th subcarrier is used by the m-th relay or not is availableRepresents:

F_{R_{m}}^{[k]} = F_{1 m}^{[k]} F_{2 m}^{[k]} - - - (7)

if it isThe subcarrier is the "used subcarrier", which is being centeredR is_mThe use is carried out; if it isThe sub-carrier is discarded from use.

3. The method of claim 1 for joint subcarrier suppression and relay selection in a PLNC-based bi-directional OFDM multi-relay system, wherein the relay selection method comprises the steps of:

in a TDMA-based two-way multi-relay system, one relay with the best channel conditions is selected for transmitting information, and one relay is selected according to the minimum-maximum principle:

R^{*} = \arg \underset{m}{m a x} {\min_{k &Element; I} {\min_{i} | H_{i m}^{[k]} |}}} - - - (8)

R^*representing the selected relay, m representing the mth relay, m ∈ {1, … N }, I numbers corresponding to the two source nodes, I ∈ {1,2}, K representing the kth subcarrier, K ∈ {1, … K }, I representing the set of subcarriers used, denotes from S_iTo R_mThe modulus of the gain of the multi-path Rayleigh fading channel on the kth subcarrier;

according to different subcarrier suppression methods, combined with minimum and maximum relay selection, the joint subcarrier suppression and relay selection method comprises the following steps: FT-J and FNS-J, wherein FT-J is a JSRS method with a fixed suppression threshold, and FNS-J is a JSRS method with a fixed number of subcarriers.

4. The joint subcarrier suppression and relay selection method in a PLNC-based bi-directional OFDM multi-relay system according to claim 3, wherein the JSSRS method of fixing the suppression threshold comprises the steps of:

FT-J carries on the subcarrier to inhibit at first, then choose a relay with the best channel condition to carry on the information transmission in all relays; before subcarrier suppression, S₁,S₂The determination of the suppression threshold lambda is required₀(ii) a Lambda of FT-J₀The value is S₁,S₂A constant directly determined, which is kept constant during both the multiple access and broadcast time slots; s₁,S₂Performing suppression operation on all subcarriers according to the subcarrier suppression method:

F_{1 i m}^{[k]} = \{\begin{matrix} 1, & i f & | {\hat{H}}_{i m}^{[k]} | &GreaterEqual; λ_{0} \\ 0, & i f & | {\hat{H}}_{i m}^{[k]} | < λ_{0} \end{matrix}, i = 1, 2 - - - (9)

F_{1 R_{m}}^{[k]} = F_{11 m}^{[k]} F_{12 m}^{[k]} - - - (10)

H_{1 i m}^{[k]} = F_{1 R_{m}}^{[k]} \times H_{i m}^{[k]} - - - (11)

denotes S_iThe sub-carrier state between the relay and the relay,"1" indicates that the subcarrier is an active subcarrier; "0" indicates that the subcarrier is a suppression subcarrier;indicating whether the subcarriers on the left and right sides of the relay are "used subcarriers",indicating that the subcarrier is a "used subcarrier",indicating that the subcarrier was dropped;indicating whether the channel of each subcarrier is used after subcarrier suppression;the expression "used sub-carrier" channel is used,indicating that the channel dropping of the suppressed sub-carriers is not used;

finally, selecting a relay with the best channel condition from all relays for information transmission;

R^{*} = \arg \max_{m} {\min_{k &Element; I_{1}} {\min_{i} {| H_{1 i m}^{[k]} |}}} - - - (12)

R^*m represents the selected relay, m ∈ {1, … N }, I corresponds to two source nodes, I ∈ {1,2}, K represents the K subcarrier, K ∈ {1, … K }, and I represents the selected relay, m represents the mth relay, m ∈ {1, … N }, I corresponds to two source nodes, I ∈ {1,2}, K represents the kth subcarrier, K represents the K ∈ {1, 38₁Denotes a set of subcarriers used in the FT-J method, denotes from S_iTo R_mThe modulus of the gain of the sub-carrier channel used in between on the k sub-carrier.

5. The joint subcarrier suppression and relay selection method in the PLNC-based bidirectional OFDM multi-relay system according to claim 3, wherein the JSSRS method with a fixed number of subcarriers comprises the steps of:

FNS-J firstly carries out subcarrier suppression, and then selects a relay with the best channel condition from all relays to carry out information transmission; before subcarrier suppression, S₁,S₂The determination of the suppression threshold lambda is required₀(ii) a FNS-J requires S₁,S₂Firstly, determining the number Q of used subcarriers, wherein Q is a constant; determining a temporary suppression threshold, i.e. S, from a constant Q₁,S₂Selecting the Q sub-carriers with the best channel condition from all K sub-carriers to transmit information (0 < Q ≦ K), and modeling the Qth channel gainAs temporary suppression thresholds, i.e.And carrying out suppression operation on all subcarriers:

F_{2 i m}^{[k]} = \{\begin{matrix} 1, & i f & | {\hat{H}}_{i m}^{[k]} | &GreaterEqual; | H_{i m}^{[Q]} | \\ 0, & i f & | {\hat{H}}_{i m}^{[k]} | < | H_{i m}^{[Q]} | \end{matrix}, i = 1, 2 - - - (13)

F_{2 R_{m}}^{[k]} = F_{21 m}^{[k]} F_{22 m}^{[k]} - - - (14)

H_{2 i m}^{[k]} = F_{2 R_{m}}^{[k]} \times H_{i m}^{[k]} - - - (15)

denotes S_iSubcarrier status to relay, "1" indicates that the subcarrier is an active subcarrier; "0" indicates that the subcarrier is a suppression subcarrier;indicating whether the subcarrier is a "used subcarrier",indicating that the subcarrier is a "used subcarrier",indicating that the subcarrier was dropped;indicating whether a channel for each subcarrier is used through subcarrier suppression;the expression "used sub-carrier" channel is used,indicating that the channel dropping of the suppressed sub-carriers is not used;

during the time slots of multiple access and broadcast, Q is fixed and unchanged, and the dynamic change of the threshold is restrained; thus, two rejection thresholds for the same relayDifferent; the threshold values for different relays are also different; and finally, selecting a relay with the best channel condition from all relays to transmit information:

R^{*} = \arg \underset{m}{m a x} {\min_{k &Element; I_{2}} {\min_{i} {| H_{2 i m}^{[k]} |}}} - - - (16)

R^*m represents the selected relay, m ∈ {1, … N }, I corresponds to two source nodes, I ∈ {1,2}, K represents the K subcarrier, K ∈ {1, … K }, and I represents the selected relay, m represents the mth relay, m ∈ {1, … N }, I corresponds to two source nodes, I ∈ {1,2}, K represents the kth subcarrier, K represents the K ∈ {1, 38₂Indicating the set of subcarriers used by the FNS-J method, denotes from S_iTo R_mThe modulus of the gain of the used subcarrier channel on the k subcarrier.

6. The joint subcarrier suppression and relay selection method in the PLNC-based bidirectional OFDM multi-relay system according to claim 1, wherein the relay physical layer network coding method comprises the steps of:

adopting maximum likelihood decoding according to a decoding forwarding mode; the selected relay is first calculated in the multiple access slot X₁Is c, X₂Probability of being dFor BPSK modulation, c ∈ { +1, -1}, d ∈ { +1, -1 }:

\begin{matrix} P_{m}^{[k]} (+ 1, + 1) &Proportional; \exp (- \frac{{| Y_{R_{m}} [k] - {\hat{H}}_{1 m}^{[k]} - {\hat{H}}_{2 m}^{[k]} |}^{2}}{σ^{2}}) \\ P_{m}^{[k]} (- 1, - 1) &Proportional; \exp (- \frac{{| Y_{R_{m}} [k] + {\hat{H}}_{1 m}^{[k]} + {\hat{H}}_{2 m}^{[k]} |}^{2}}{σ^{2}}) \\ P_{m}^{[k]} (+ 1, - 1) &Proportional; \exp (- \frac{{| Y_{R_{m}} [k] + {\hat{H}}_{1 m}^{[k]} + {\hat{H}}_{2 m}^{[k]} |}^{2}}{σ^{2}}) \\ P_{m}^{[k]} (- 1, + 1) &Proportional; \exp (- \frac{{| Y_{R_{m}} [k] + {\hat{H}}_{1 m}^{[k]} + {\hat{H}}_{2 m}^{[k]} |}^{2}}{σ^{2}} \end{matrix} - - - (17)

wherein,to representEstimate of, σ²Representing the variance of the noise; the selected relay then receives S₁,S₂Transmitted informationThen network-coding it withTo representThe information obtained after network coding includes:

A_{R_{m}}^{[k]} = \{\begin{matrix} 0, & i f & P_{m}^{[k]} (+ 1, + 1) + P_{R_{m}} [k] (- 1, - 1) &GreaterEqual; P_{m}^{[k]} (+ 1, - 1) + P_{R_{m}} [k] (- 1, + 1) \\ 1, & i f & P_{m}^{[k]} (+ 1, + 1) + P_{R_{m}} [k] (- 1, - 1) < P_{m}^{[k]} (+ 1, - 1) + P_{R_{m}} [k] (- 1, + 1) \end{matrix} - - - (18)

can be written into after BPSK modulationSelected relay barBroadcast to S₁,S₂(ii) a Third step, S₁,S₂Receiving information from selected relay broadcastsRepresents;result after equalizationThis means that there are:

M_{S_{1}}^{[k]} = Y_{S_{1}}^{[k]} / H_{1 m}^{[k]} - - - (19)

M_{S_{2}}^{[k]} = Y_{S_{2}}^{[k]} / H_{2 m}^{[k]} - - - (20)

finally, S₁,S₂Demodulating the received information according to the following method:

B_{S_{1}}^{[k]} = \{\begin{matrix} 0, & i f & M_{S_{1}}^{[k]} < 0 \\ 1, & i f & M_{S_{1}}^{[k]} &GreaterEqual; 0 \end{matrix} - - - (21)

B_{S_{2}}^{[k]} = \{\begin{matrix} 0, & i f & M_{S_{2}}^{[k]} < 0 \\ 1, & i f & M_{S_{2}}^{[k]} &GreaterEqual; 0 \end{matrix} - - - (22)

wherein,denotes S_iDemodulationThe latter result, i ∈ {1,2 }; in summary, S₁Received signal ofS₂Received signal ofComprises the following steps:

A_{2}^{[k]} = A_{1}^{[k]} &CirclePlus; B_{S_{1}}^{[k]} - - - (23)

A_{1}^{[k]} = A_{2}^{[k]} &CirclePlus; B_{S_{2}}^{[k]} - - - (24)

。