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

Abstract

The present invention discloses a PLNC-based combined subcarrier suppression and relay selection method in a bidirectional OFDM multi-relay system, and provides two combined subcarrier suppression and relay selection methods of a combined subcarrier suppression and relay selection method with fixed suppression threshold and a combined subcarrier suppression and relay selection method with fixed subcarrier number. The combined subcarrier suppression and relay selection method with the fixed suppression threshold adopts the fixed suppression threshold to suppress the subcarriers during one bidirectional information exchange process, and the combined subcarrier suppression and relay selection method with the fixed subcarrier number keeps the suppressed subcarrier number to be constant during the bidirectional information exchange process, namely, the active subcarrier number is constant while the threshold dynamic change is suppressed. A simulation result shows that compared with the conventional subcarrier suppression, the two combined subcarrier suppression and relay selection methods provided by the present invention enables the system reliability to be enhanced and also the system validity to be improved.

Description

Suppress and relay selection method based on the joint subcarrier in the many relay systems of two-way OFDM of PLNC

Technical field

The invention belongs to wireless communication technology field, relate to the effective transmission technique of the many relay systems of double-direction radio, for a kind of based on the effective transmission technique in the many relay systems of two-way OFDM of PLNC, particularly relate to a kind of based on the joint subcarrier suppression in the many relay systems of two-way OFDM of PLNC and relay selection method。

Background technology

Flourish along with mobile Internet, mobile communication is more and more higher to the demand of high speed data transfer。As the support that wideband requirements is most basic, frequency spectrum resource scarcity problem is further prominent and serious。Therefore, when frequency spectrum resource is limited, the availability of frequency spectrum and the handling capacity that how to improve mobile communication system further are one of major issues needing solution badly in next generation mobile communication system design。

OFDM (OrthogonalFrequencyDivisionMultiplexing, OFDM) technology, owing to it has the feature such as high spectrum utilization and good anti-multipath fading ability, have become as the significant physical layer transmission bearing technology of forth generation mobile communication " A.Doufexi; andS.Armour.Designconsiderationsandphysicallayerperforma nceresultsfora4GOFDMsystememployingdynamicsubcarrierallo cation.Proc.IEEEPIMRC, Sept.2005:357-361. "。In order to expand base station range, obtain diversity gain, cooperative relaying technology " RoyaArabLoodaricheh; ShankhanaadMallick; andVijayK.Bhargava.DistributedsubcarrierPairingandrelays electionforOFDMbasedcooperativerelaynetworks.Proc.IEEEWC NC, Apri2013:3557-3562. " causes the extensive concern of academia and industry as one of key technology in Next-Generation Wireless Communication Systems。The information of source node is transmitted to destination node by amplification forwarding or decoding pass-through mode by via node。In double-direction radio junction network, compared with traditional multi-hop transmission, physical-layer network coding (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:analognetworkc oding.Proc.Conf.Applicat, Technol, ArchitandProtocolsforComput.Commun., 2007:397-408. " throughput performance of system can be significantly improved。At present, in collaboration relay system, one of PLNC technology hot issue becoming research。

In two-way many relay systems, it is limited to the relaying that channel is worst, utilizes the mode that all relayings carry out information forwarding not necessarily can improve systematic function。Utilize relay selection technology " XiaochenXia; KuiXu; WenfengMa; andYouyunXu.OntheDesignofRelaySelectionStrategyforTwo-Wa yAmplify-and-ForwardMobileRelaying.IETCommu.2013; Vol.7 (17): 1948-1957. " by selecting the relay forwarding information that one or more channel condition is good in multiple relayings, it is possible to obtain diversity gain thus improving system performance of BER。Document " J.leithon; S.Sumei; andY.Chau.RelaySelectionAlgorithmsforAnalogNetworkCoding OFDMSystems.IEEECommunicationLetters; 2012, vol.16 (9): 1442-1445. " proposes a kind of ofdm system minimax relay selection method based on analog network coding。The relaying that the method selects minimum channel gain maximum carrys out forwarding information。Simulation result shows, compared with the mono-relay system of two-way OFDM, minimax relay selection method can be greatly improved the bit error rate and the throughput performance of system。

In order to improve the transmission reliability of the two-way many relay systems of PLNC-OFDM further, document " G.Bartoli; R.Fantacci; D.Marabissi; andR.Simoni.SubcarriersSuppressionMethodsforOFDMSystemsw ithDecode-and-ForwardNetworkCoding.IEEETrans.; WirelessCommunication, 2013, vol.12 (12): 6034-6042. " proposes two sub-carrier suppressing method。" subcarrier suppression " is namely abandoned using the subcarrier of bad channel conditions only to use the subcarrier that channel condition is good to carry out information transmission in an ofdm system。Before information transmission, system give a suppression threshold value, the absolute value of channel gain be higher than the subcarrier of this threshold value be used to that the absolute value of transmission information channel gain is then abandoned lower than the subcarrier of this threshold value need not。Subcarrier suppresses system performance of BER is greatly improved。When multi-path Fading Channel, subcarrier suppresses while reducing system bit error rate, also brings along certain throughput of system loss。

By being applied in wireless broadcast communication by the thought of network code, it is possible to the effective efficiency improving broadcast, present stage, existing patent achievement was as follows:

By being applied in wireless relay communication by the thought of network code, it is possible to the effective efficiency of transmission improving trunking traffic, present stage, existing patent achievement was as follows:

1. the wireless network analog network coding method that Shanghai Communications University proposes, the invention discloses a kind of wireless network analog network coding method, comprise the following steps: the overlapped data frame received is detected by computing cross-correlation starting point and the end point of given frame and target frame；Data are carried out frequency offset detection and compensation；Carry out channel parameter estimation again；Further according to the channel parameter obtained, remove the given frame in overlapped data frame, target frame is recovered and resampling, reacquire sampled point；To the decoding data after sampling。The present invention can the range of application of growth simulation network code, improve the availability of frequency spectrum in wireless network。

2. network coding method during the orthogonal differential sky of bidirectional relay channel model that the China Measures Institute proposes, the invention discloses network coding method during the orthogonal differential sky of a kind of bidirectional relay channel model, described model include two information sources and, one relaying R, information source introduces multiple antennas mechanism, equipped with multiple antennas；Comprising the steps: that signals transmission is divided into two stages: the information source transmission stage, bit stream, by constellation mapping, Alamouti coding, Differential space-time modulation, obtains launching signal matrix；In the repeat broadcast stage, it is achieved the reception of signal, detection, demodulation, then realize the exclusive-OR network coding of two information source information, differential modulation, and be mapped as transmission symbol, be broadcast to two information sources；Wherein signal adopts many packet transaction when receiving, and adopts many signatures to divide globular decoding to complete signal detection, the reception signal interpretation of uplink relay and downlink information source is all suitable for。

3. adaptive strain time slot analog network coding strategy in a kind of bidirectional relay system that Xi'an Communications University proposes, the present invention provides adaptive strain time slot analog network coding strategy in a kind of bidirectional relay system, this strategy is based on transient channel information, do not change system mean power with cooperate the cycle when, principle to maximize instantaneous mutual information dynamically adjusts transmission time slot number, theory analysis and simulation result show, compared with the analog network coding strategy of fixing time slot, strategy proposed by the invention reduces outage probability while obtaining diversity gain, additionally, the inventive method adopts simple constant power allocative decision to be obtained in that the performance of near-optimization。

4. the physical-layer network coding system and method based on FQPSK modulation that Harbin Institute of Technology Shenzhen Graduate School proposes, the invention provides a kind of physical-layer network coding method and system based on FQPSK modulation, should based on the physical-layer network coding method of FQPSK modulation, transmitting terminal unit includes performing two signal sources of following steps: A. and launches raw information x respectively_AAnd x_B；B. by two raw information x_AAnd x_BModulate after modulation respectively and above high frequency carrier, become transmitting signal z_AAnd z_B；C. trunk module receives mixed signal and is expressed as: Y_R(t)=[z_A(t)+n(t)]+[z_B(t)+n'(t)], Y_RT () represents the hybrid waveform signal received。The invention has the beneficial effects as follows that physical-layer network coding signal is carried out permanent envelope protection by use FQPSK modulation; successfully solve at relaying place the detection to superposed signal and classification problem; use waveform bunch sorting criterion to replace existing constellation sorting criterion, avoid FQPSK modulation constellation this shortcoming random。

5. the method carrying out physical-layer network coding by channel quantitative in relay system that the Chinese Academy of Space Technology and Shenzhen University propose, the present invention relates to the method carrying out physical-layer network coding by channel quantitative in relay system, comprise the steps: to would indicate that said two end node carries out QR decomposition to the channel matrix of described via node, and it is multiplied by Q matrix to receiving vector, represented that the first end node and the second end node are sent to the first intermediate layer signal and the second intermediate layer signal of described via node signal respectively；Utilize the coding signal that described second end node is sent by described second intermediate layer signal to carry out valuation, obtain the signal estimation that described second end node sends；Utilizing the first intermediate layer signal and the second intermediate layer signal estimation, the coding signal that described first end node and the second end node are sent carries out valuation, obtains the valuation of the composite signal that described via node receives, obtains network code；Wherein, described valuation step includes, according to parameter values different in described first intermediate layer signal expression, it being quantified and mapping。Implement the quantization method of a kind of relay system up channel of the present invention, have the advantages that its calculating is simple, efficiency is higher。

6. the wireless communications method of the physical-layer network coding based on MQAM modulation system that Harbin Institute of Technology proposes, based on the wireless communications method of the physical-layer network coding of MQAM modulation system, relates to a kind of wireless communication field。The invention solves three time slots that existing transmission means needs in bidirectional relay channel, problem that four time slots cause systematic function low。Concrete grammar is, to user N₁、N₂Coded-bit information S₁、S₂Carry out MQAM modulation, the signal s after being modulated₁(t)、s₂T () also sends to via node NR simultaneously, it is directly added and obtains and signal r by via node NR_R(t) to r_RT () makes decisions, court verdict is mapped as S further₁And S₂Network code information S_R；Via node N afterwards_RTo S_RRe-start MQAM modulation, and by modulated signal s_RT () is to user node N₁And N₂Broadcast, N₁、N₂Respectively to the s received_RT () is demodulated, will obtain network code information S_RStep-by-step bit XOR is carried out, to obtain the bit information of another user, thus realizing primary information exchange process with the transmission information in the local cache being saved in this user。The present invention is applicable to radio communication。

7. the wireless communications method of the physical-layer network coding based on MFSK modulation system that Harbin Institute of Technology proposes, the present invention relates to wireless communication field。It is by compressing the number of time slot of data communication and then realizing improving the performance of wireless communication system。Its method: the bit information after the coding sent by two user nodes respectively carries out MFSK modulation, and is sent simultaneously to via node；Via node carries out being added acquisition and signal；And after making decisions, it is mapped as the bit information of network code；Then backward two user nodes broadcast of MFSK modulation is carried out；The modulation signal of broadcast is demodulated by two users respectively, and export carrying out with the corresponding modulation signal being saved in local cache after step-by-step carries out bit XOR respectively, thus realizing the radio communication of the physical-layer network coding based on MFSK modulation system。The present invention is applicable to the radio communication of the physical-layer network coding based on MFSK modulation system。

8. what Harbin Institute of Technology proposed is a kind of based on the wireless communications method of physical-layer network coding in the smooth frequency selective fading channel of two-way relay model, and the method relates to wireless communications method。This invention removes interference between modulation signal real part and imaginary part, reduce the complexity of link receiver。In the present invention, two information source node are sent to via node after information data is carried out QPSK modulation, precoding, carrier modulation, again carrier modulation, and the signal received is added by via node, then to after carrying out carrier wave demodulation with signal, broadcast data is tried to achieve in judgement mapping；Broadcast data is carried out broadcast transmission after QPSK modulation, carrier modulation again；The carrier (boc) modulated signals receiving broadcast is carried out carrier wave demodulation by information source node, information source node S1 and information source node S2 respectively to after carrier wave demodulation and signal carry out signal processing, information source node S1 obtains information source node S2 and sends the estimated value of signal, and information source node S2 obtains the estimated value of information source node S1 transmission signal and completes communication。The present invention is used for radio communication。

9. the physical-layer network coding method based on symbol for two-way relay communication system that Beijing University of Post & Telecommunication proposes, the inventive method operating procedure is as follows: the first time slot is relay reception information: two source nodes send respective modulated signal to relaying respectively, relay the superposed signal to receiving and do auto-correlation computation, obtain autocorrelation matrix, from this matrix, network code symbol to be broadcast is detected again with maximum likelihood ML detection algorithm, make the detection reduced space of network code symbol, thus reducing signal detection difficulty, obtain simultaneously and receive diversity gain, guarantee system error performance。Second time slot is repeat broadcast information: the network code symbol detected is broadcasted by relaying, and two source nodes are respectively adopted self-interference removing method and decode acquisition counter-party information to received signal, complete communication process。The present invention utilizes phase-shift keying mpsk signal feature in M rank to reduce the computational complexity of relay process signal, it is thus achieved that receive diversity gain, it is adaptable to the MPSK modulating system of symmetrical and asymmetric speed under bidirectional relay channel。

10. the combined channel network coding method of the two-way ofdm system with frequency deviation that Univ. of Science and Engineering, PLA proposes, the method first stage source node broadcast OFDM symbol, the signal that via node receives is the superposition of the OFDM symbol with different frequency deviation of two source node broadcast, second stage is that via node estimates two carrier wave frequency deviations different between source node from via node and channel information according to the superposition OFDM symbol received, and carry out combined channel network code, afterwards the information after network code is broadcast to two source nodes, two source nodes utilize the combined channel network code received after OFDM symbol carry out combined channel network decoding, complete bi-directional relaying。The present invention is under carrier wave frequency deviation existent condition, it is possible to more realize reliable bidirectional transfer of information while high-transmission efficiency obtaining。

11. the relevant network code that utilizes that University Of Tianjin proposes realizes the receiving/transmission method of irrelevant reception, the present invention relates to wireless multi-hop network technology。Specifically, relevant network code is utilized to realize the receiving/transmission method of irrelevant reception。For improving wireless multi-hop communication efficiency of transmission, reducing technical sophistication degree, reduce communication bit error rates, the technical solution used in the present invention is: carry out network of relation PCNC coding in source physical layer；E-mail relay utilization channel fading coefficient, detects and mixed signal after utilizing uniqueness mapping relations that the signal detected is mapped to denoising, and mixed signal carries out differential modulation is sent to two sources intercomed mutually；When source receives, mixed signal is utilized to be reflected the differential relationship of signal in front and back moment, be implemented without knowing the irrelevant reception in any characteristic of channel situation, with recover described two continuous slot signal and, and the signal deducting local terminal obtains the signal of opposite end。Present invention is mainly used for needing the transmission in the wireless co-operative communication of relaying, the transmission between the base station not having straightline propagation circuit and mobile terminal。

Existing network code broadcasting method seldom considers to utilize OFDM transmission technology in physical layer。In OFDM broadcast system, due to the frequency selective fading that channel has, therefore, the channel capacity of each subcarrier is different。Need on the subcarrier with different channels capacity, be allocated limited energy resource, thus the transfer rate performance of optimization system。In many relay systems, owing to the Link State between terminal and relaying is different, it is necessary to carry out signal forwarding from the relaying of all middle selection optimal performances, thus obtaining optimal performance。Therefore, in the many relay systems of two-way OFDM, it is necessary to the degree of freedom that the degree of freedom provided by multiple subcarriers in OFDM modulation system and multiple relayings provide effectively is utilized, thus improving systematic function。

Summary of the invention

It is an object of the invention to for above-mentioned the deficiencies in the prior art, there is provided a kind of to suppress and relay selection method based on the joint subcarrier in the many relay systems of two-way OFDM of PLNC, this suppresses to not only increase system effectiveness with relay selection method based on the joint subcarrier in the many relay systems of two-way OFDM of PLNC, and enhances system reliability。

For solving above-mentioned technical problem, the technical scheme is that and suppress and relay selection method based on the joint subcarrier in the many relay systems of two-way OFDM of PLNC, it is characterised in that comprise the following steps:

Based on two-way many relay systems of TDMA by N number of via node { R₁,R₂,…R_NAnd two source node S₁,S₂Constituting, all nodes are equipped with single antenna and are operated in semiduplex mode；S₁Know S₁Channel condition information between each via node；S₂Know S₂Channel condition information between each via node；Described two-way many relay systems based on TDMA adopt OFDM transmission mode, and subcarrier number K represents；S₁,S₂Channel to via node is multi-path Fading Channel, with vector h_iRepresent:

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

Wherein,L represents number of path；S₁,S₂To the channel independent same distribution of via node, the frequency domain channel on kth subcarrier is H_i[k]:

$H_i\[k\]=\underset{l=0}{\overset{L-1}{\Σ}}{h}_i{\[l\]}^{-2j\mathrm{\π}\frac{k}{K}l},i=1,2---\left(2\right)$

Information exchange each time can be divided into two stages: multiple access access phase and broadcast phase:

Multiple access access phase: first, S₁,S₂Kth subcarrier is respectively necessary for transmission informationThen, informationCan be expressed as after ovennodulationFinally, S₁,S₂InformationIt is sent to all of via node；Reception signal on the kth subcarrier of m-th relaying can be expressed as:

$Y_{R_m}^{\[k\]}=H_{1m}^{\[k\]}{X}_1^{\[k\]}+H_{2m}^{\[k\]}{X}_2^{\[k\]}+N_{R_m}^{\[k\]}---\left(3\right)$

Represent from S_iTo R_mBetween multi-path Fading Channel gain on kth subcarrier, m ∈ 1 ... N}, k ∈ 1 ... K}, i ∈ { 1,2}, and from S₁,S₂To via node and via node to S₁,S₂Channel be identical；Represent additive white Gaussian noise；

Broadcast phase: first, S₁,S₂All relayings select the relaying that a channel status is best；Then, the information received is broadcast to S by the mode that selected E-mail relay utilization decoding forwards₁,S₂；Finally, S₁,S₂The information received can be expressed as follows:

$r_{S_1}^{\[k\]}=H_{1m}^{\[k\]}{X}_{R_m}^{\[k\]}+N_1^{\[k\]}---\left(4\right)$

$Y_{S_2}^{\[k\]}=H_{2m}^{\[k\]}{X}_{R_m}^{\[k\]}+N_2^{\[k\]}---\left(5\right)$

Represent the information that via node network code obtainsThe information obtained after ovennodulation,Represent source node S_iThe information received,Represent additive white Gaussian noise, i ∈ { 1,2}。

Further, subcarrier suppresses to comprise the following steps:

Owing to the Multipath Transmission characteristic of wireless channel can cause frequency selective fading, based in two-way many relay systems of TDMA, the frequency selective fading of channel can cause different subcarriers to have different channel gains, subcarrier suppression is the subcarrier transmission information good merely with channel condition, and the subcarrier of bad channel conditions abandon need not, useRepresent suppression threshold, when the channel gain of subcarrier is higher thanTime, define this subcarrier for " active sub-carriers "；Otherwise, when subcarrier channel gain lower thanTime, define this subcarrier for " suppression subcarrier "；Whether each subcarrier is enliven to use subcarrier statusIt is expressed as follows:

$F_{im}^{\&lsqb;k\&rsqb;}=\left\{\begin{array}{ccc}1,& if& \left|{\hat{H}}_{im}^{\&lsqb;k\&rsqb;}\right|\&GreaterEqual;{\mathrm{\&lambda;}}_0^i\\ 0,& if& \left|{\hat{H}}_{im}^{\&lsqb;k\&rsqb;}\right|<{\mathrm{\&lambda;}}_0^i\end{array}\right.,i=1,2---\left(6\right)$

" 1 " represents that this subcarrier is active sub-carriers；" 0 " represents that this subcarrier is to suppress subcarrier；Represent from S_iTo R_mBetween multi-path Fading Channel estimated value of gain on kth subcarrier；When being only all " active sub-carriers " between two source nodes, this subcarrier just is used for transmitting information by relaying, is defined as " subcarrier of use "；System only uses " subcarrier of use " to transmit information and do not use repressed subcarrier；Therefore, whether kth subcarrier is relayed use by m-th and can use stateRepresent:

$F_{R_m}^{\&lsqb;k\&rsqb;}=F_{1m}^{\&lsqb;k\&rsqb;}{F}_{2m}^{\&lsqb;k\&rsqb;}---\left(7\right)$

IfThen this subcarrier is " subcarrier of use ", by relaying R_mUse；IfThen be abandoned need not for this subcarrier。

Further, relay selection method comprises the following steps:

Select best one relaying of channel condition to be transmitted information in based on two-way many relay systems of TDMA, select a relaying according to minimax principle:

$R^{*}=\arg \underset{m}{\max }\left\{\underset{k\&Element;I}{\min }\right\{\underset{i}{\min }\left\{\right|H_{im}^{\&lsqb;k\&rsqb;}\left|\right\}\left\}\right\}---\left(8\right)$

R^*Representing selected relaying, m represents that m-th relays, m ∈ 1 ... N}；The numbering of corresponding two source nodes of i, i ∈ { 1,2}；K represents kth subcarrier, k ∈ 1 ... K}；I represents the t easet ofasubcarriers of use, Represent from S_iTo R_mBetween multi-path Fading Channel modulus value of gain on kth subcarrier；

Different according to subcarrier suppressing method, in conjunction with minimax relay selection, described joint subcarrier suppresses to include with relay selection method: FT-J and FNS-J, FT-J are the fixing JSSRS method of suppression threshold, FNS-J is the JSSRS method of stator variable number。

Further, JSSRS method (FixThresholdbasedJSSRS, the FT-J) method of fixing suppression threshold comprises the following steps:

First FT-J carries out subcarrier suppression, and the relaying that then one channel condition of selection is best in all relayings carries out information transmission；Before subcarrier suppresses, S₁,S₂It needs to be determined that suppression threshold λ₀；The λ of FT-J₀Value is S₁,S₂The constant directly determined, this constant accesses at multiple access and remains unchanged during two time slots of broadcast；S₁,S₂Carry out suppressing operation to all subcarriers according to above-mentioned subcarrier suppressing method:

$F_{1im}^{\&lsqb;k\&rsqb;}=\left\{\begin{array}{ccc}1,& if& \left|{\hat{H}}_{im}^{\&lsqb;k\&rsqb;}\right|\&GreaterEqual;{\mathrm{\&lambda;}}_0\\ 0,& if& \left|{\hat{H}}_{im}^{\&lsqb;k\&rsqb;}\right|<{\mathrm{\&lambda;}}_0\end{array}\right.,i=1,2---\left(9\right)$

$F_{1R_m}^{\&lsqb;k\&rsqb;}=F_{11m}^{\&lsqb;k\&rsqb;}{F}_{12m}^{\&lsqb;k\&rsqb;}---\left(10\right)$

$H_{1im}^{\&lsqb;k\&rsqb;}=F_{1R_m}^{\&lsqb;k\&rsqb;}\&times;H_{im}^{\&lsqb;k\&rsqb;}---\left(11\right)$

Represent S_iSubcarrier status between relaying, " 1 " represents that this subcarrier is active sub-carriers；" 0 " represents that this subcarrier is to suppress subcarrier；Represent whether the subcarrier relaying the right and left is " subcarrier of use ",Represent that this subcarrier is " subcarrier of use ",Representing that this subcarrier is abandoned need not；Represent whether the channel of each subcarrier is used after subcarrier suppresses；Represent that " subcarrier of use " channel is used,Expression suppresses the channel of subcarrier to abandon need not；

The last relaying that one channel condition of selection is best in all relayings carries out information transmission；

$R^{*}=\arg \underset{m}{\max }\left\{\underset{k\&Element;I_1}{\min }\right\{\underset{i}{\min }\left\{\right|H_{1im}^{\&lsqb;k\&rsqb;}\left|\right\}\left\}\right\}---\left(12\right)$

R^*Representing selected relaying, m represents that m-th relays, m ∈ 1 ... N}；Corresponding two source nodes of i, i ∈ { 1,2}；K represents kth subcarrier, k ∈ 1 ... K}；I₁Represent the t easet ofasubcarriers used in FT-J method, Represent from S_iTo R_mBetween use sub-carrier channels modulus value of gain on kth subcarrier。

If λ₀Smaller, then some relaying has a suppressed subcarrier and some relaying is suppressed subcarrier, and so, the minimum channel gains of the subcarriers that all relayings use are different, after carrying out co-design with minimax relay selection, systematic function can be highly improved。But, if λ₀Relatively larger, the subcarrier of all relayings all experiences subcarrier to be suppressed, and the minimum channel gain of subcarrier that they use is almost identical, and in this case, then after carrying out minimax relay selection, systematic function can not improve。

Further, JSSRS method (FixNumberofSubcarriersbasedJSSRS, the FNS-J) method of stator variable number comprises the following steps:

Similar with FT-J, first FNS-J carries out subcarrier suppression, and the relaying that then one channel condition of selection is best in all relayings carries out information transmission；Before subcarrier suppresses, S₁,S₂It needs to be determined that suppression threshold λ₀；With FT-J the difference is that, FNS-J needs S₁,S₂First determine that number Q, the Q of the subcarrier of use are constants；Interim suppression threshold is determined, i.e. S according to constant Q₁,S₂Q the subcarrier selecting channel condition best in all K subcarriers transmits information (0 < Q≤K), channel gain molding good for QAs interim suppression threshold, namelyCarry out all subcarriers suppressing operation:

$F_{2im}^{\&lsqb;k\&rsqb;}=\left\{\begin{array}{ccc}1,& if& \left|{\hat{H}}_{im}^{\&lsqb;k\&rsqb;}\right|\&GreaterEqual;\left|H_{im}^{\&lsqb;Q\&rsqb;}\right|\\ 0,& if& \left|{\hat{H}}_{im}^{\&lsqb;k\&rsqb;}\right|<\left|H_{im}^{\&lsqb;Q\&rsqb;}\right|\end{array}\right.,i=1,2---\left(13\right)$

$F_{2R_m}^{\&lsqb;k\&rsqb;}=F_{21m}^{\&lsqb;k\&rsqb;}{F}_{22m}^{\&lsqb;k\&rsqb;}---\left(14\right)$

$H_{2im}^{\&lsqb;k\&rsqb;}=F_{2R_m}^{\&lsqb;k\&rsqb;}\&times;H_{im}^{\&lsqb;k\&rsqb;}---\left(15\right)$

Represent S_iSubcarrier status between relaying, " 1 " represents that this subcarrier is active sub-carriers；" 0 " represents that this subcarrier is to suppress subcarrier；Represent whether this subcarrier is " subcarrier of use ",Represent that this subcarrier is " subcarrier of use ",Representing that this subcarrier is abandoned need not；Represent and suppress whether the channel of each subcarrier is used through subcarrier；Represent that " subcarrier of use " channel is used,Expression suppresses the channel of subcarrier to abandon need not；

During multiple access accesses and broadcasts two time slots, Q immobilizes, and suppression threshold dynamically changes；Therefore, two suppression thresholds of same relayingDiffer；This threshold value of different relayings also differs；The last relay transmission information selecting a channel condition best in all relayings:

$R^{*}=\arg \underset{m}{\max }\left\{\underset{k\&Element;I_2}{\min }\right\{\underset{i}{\min }\left\{\right|H_{2im}^{\&lsqb;k\&rsqb;}\left|\right\}\left\}\right\}---\left(16\right)$

R^*Representing selected relaying, m represents that m-th relays, m ∈ 1 ... N}；Corresponding two source nodes of i, i ∈ { 1,2}；K represents kth subcarrier, k ∈ 1 ... K}；I₂Represent the t easet ofasubcarriers that FNS-J method uses, Represent from S_iTo R_mThe sub-carrier channels modulus value of gain on kth subcarrier used。

In FNS-J, no matter Q-value is big or little, each relaying will carry out subcarrier suppression, so the minimum channel gain of the subcarrier of each relaying use is different。Carry out relay selection in this case, the performance of system be improved significantly。

Further, relaying physical-layer network coding method comprises the following steps:

According to decoding pass-through mode, adopt maximum-likelihood decoding；Selected relaying first has to calculate at multiple access access slot X₁It is c, X₂It it is the probability of dBPSK is modulated, c ∈+1 ,-1}, d ∈+1 ,-1}:

$P_m^{\&lsqb;k\&rsqb;}(+1,+1)\&Proportional;\exp (-\frac{|Y_{R_m}\&lsqb;k\&rsqb;-{\hat{H}}_{1m}^{\&lsqb;k\&rsqb;}-{\hat{H}}_{2m}^{\&lsqb;k\&rsqb;}{|}^2}{{\mathrm{\&sigma;}}^2})$

$P_m^{\&lsqb;k\&rsqb;}(-1,-1)\&Proportional;\exp (-\frac{|Y_{R_m}\&lsqb;k\&rsqb;+{\hat{H}}_{1m}^{\&lsqb;k\&rsqb;}+{\hat{H}}_{2m}^{\&lsqb;k\&rsqb;}{|}^2}{{\mathrm{\&sigma;}}^2})$

(17)

$P_m^{\&lsqb;k\&rsqb;}(+1,-1)\&Proportional;\exp (-\frac{|Y_{R_m}\&lsqb;k\&rsqb;-{\hat{H}}_{1m}^{\&lsqb;k\&rsqb;}+{\hat{H}}_{2m}^{\&lsqb;k\&rsqb;}{|}^2}{{\mathrm{\&sigma;}}^2})$

$P_m^{\&lsqb;k\&rsqb;}(-1,+1)\&Proportional;\exp (-\frac{|Y_{R_m}\&lsqb;k\&rsqb;+{\hat{H}}_{1m}^{\&lsqb;k\&rsqb;}-{\hat{H}}_{2m}^{\&lsqb;k\&rsqb;}{|}^2}{{\mathrm{\&sigma;}}^2}$

Wherein,RepresentEstimated value, σ²Represent noise variance；Then, selected relay reception is to S₁,S₂The information sentAfterwards it is carried out network code, useRepresentThe information obtained after carrying out network code, then have:

$A_{R_m}^{\&lsqb;k\&rsqb;}=\left\{\begin{array}{ccc}0,& if& P_m^{\&lsqb;k\&rsqb;}(+1,+1)+P_{R_m}\&lsqb;k\&rsqb;(-1,-1)\&GreaterEqual;P_m^{\&lsqb;k\&rsqb;}(+1,-1)+P_{R_m}\&lsqb;k\&rsqb;(-1,+1)\\ 1,& if& P_m^{\&lsqb;k\&rsqb;}(+1,+1)+P_{R_m}\&lsqb;k\&rsqb;(-1,-1)<P_m^{\&lsqb;k\&rsqb;}(+1,-1)+P_{R_m}\&lsqb;k\&rsqb;(-1,+1)\end{array}\right.---\left(18\right)$

Can be write as after BPSK modulatesSelected relaying againIt is broadcast to S₁,S₂；3rd step, S₁,S₂Receive the information that selected repeat broadcast comes, useRepresent；Result after equilibrium is usedRepresent,

Then have:

$M_{S_1}^{\&lsqb;k\&rsqb;}=Y_{S_1}^{\&lsqb;k\&rsqb;}/H_{1m}^{\&lsqb;k\&rsqb;}---\left(19\right)$

$M_{S_2}^{\&lsqb;k\&rsqb;}=Y_{S_2}^{\&lsqb;k\&rsqb;}/H_{2m}^{\&lsqb;k\&rsqb;}---\left(20\right)$

Finally, S₁,S₂The information received is demodulated according to following method:

$B_{S_1}^{\&lsqb;k\&rsqb;}=\left\{\begin{array}{ccc}0,& if& M_{S_1}^{\&lsqb;k\&rsqb;}<0\\ 1,& if& M_{S_1}^{\&lsqb;k\&rsqb;}\&GreaterEqual;0\end{array}\right.---\left(21\right)$

$B_{S_2}^{\&lsqb;k\&rsqb;}=\left\{\begin{array}{ccc}0,& if& M_{S_2}^{\&lsqb;k\&rsqb;}<0\\ 1,& if& M_{S_2}^{\&lsqb;k\&rsqb;}\&GreaterEqual;0\end{array}\right.---\left(22\right)$

Wherein,Represent S_iDemodulationAfter result, i ∈ { 1,2}；To sum up, S₁Reception signalS₂Reception signalFor:

$A_2^{\&lsqb;k\&rsqb;}=A_1^{\&lsqb;k\&rsqb;}\&CirclePlus;B_{S_1}^{\&lsqb;k\&rsqb;}---\left(23\right)$

$A_1^{\&lsqb;k\&rsqb;}=A_2^{\&lsqb;k\&rsqb;}\&CirclePlus;B_{S_2}^{\&lsqb;k\&rsqb;}---\left(24\right).$

The present invention have studied the joint subcarrier in the two-way many relay systems of PLNC-OFDM and suppresses and relay selection (JointSubcarriersSuppressionandRelaySelection, JSSRS) problem, it is achieved that not only reduce system bit error rate but also improve the target of throughput of system。Core concept of the present invention is applied in the two-way many relay systems of OFDM by subcarrier suppression technology, in conjunction with relay selection technology, propose two kinds of JSSRS methods: the JSSRS (FixThresholdbasedJSSRS of fixing suppression threshold, and the JSSRS of stator variable number (FixNumberofSubcarriersbasedJSSRS, FNS-J) FT-J)。FT-J adopts fixing suppression threshold to carry out subcarrier suppression in a bi-directional exchanges of information process；FNS-J keeps the subcarrier number suppressed invariable in a bi-directional exchanges of information process, and namely active sub-carriers number is invariable and suppression threshold dynamically changes。

Subcarrier suppression technology and relay selection technology are combined by the present invention, it is proposed to two kinds of methods of FT-J and FNS-J。Compared with suppressing with traditional subcarrier, FT-J and the FNS-J that the present invention proposes not only improves the throughput performance of system further and also improves system performance of BER。In performance of BER, FT-J, when suppression threshold is higher, increases relaying number and can not reduce system bit error rate further；And FNS-J is when the subcarrier number used is fewer, increases relaying number and remain able to reduction system bit error rate further。In throughput performance, along with increasing of relaying number, the handling capacity of FNS-J increases, but not over the subcarrier number Q used；And the handling capacity of FT-J is continuously increased along with relaying number increase, can the limit amount of swallowing of approximation system when relaying number and being abundant。

In sum, compared with suppressing with traditional subcarrier, FT-J and the FNS-J that the present invention proposes not only increases system reliability, and improves system effectiveness。In system reliability and effectiveness, FT-J and FNS-J respectively has superiority。In practical application scene, use which kind of method more suitable, depend on the requirement of system。When the data rate that system requirements is higher, can be selected for FT-J；When the main target of system is reliability, can be selected for FNS-J。

Accompanying drawing explanation

Fig. 1 be the present invention realize block diagram。

Fig. 2 is two-way OFDM many relay systems schematic diagram of the present invention。

The subcarrier that Fig. 3 is the present invention suppresses schematic diagram。

Fig. 4 is performance of BER figure Q=55, the λ=0.0758 of FT-J and the FNS-J of the present invention。

Fig. 5 is the FNS-J performance of BER figure, the SNR=10dB with the subcarrier number change used of the present invention。

Fig. 6 is the FT-J of present invention performance of BER figure, the SNR=10dB changed with suppression threshold。

Fig. 7 is FT-J and the FNS-J performance of BER figure, the SNR=10dB with relaying number change of the present invention。

Fig. 8 is throughput performance figure, Q=55, the λ=0.0758 of FT-J and the FNS-J of the present invention。

Fig. 9 is the FNS-J throughput performance figure, the SNR=10dB with the subcarrier number change used of the present invention。

Figure 10 is the FT-J of present invention throughput performance figure, the SNR=10dB changed with suppression threshold。

Figure 11 is FT-J and the FNS-J throughput performance figure, the SNR=10dB with relaying number change of the present invention。

Below in conjunction with drawings and the specific embodiments, the specific embodiment of the present invention is further described。

Detailed description of the invention

In order to make the purpose of the present invention, technical scheme and advantage clearly understand, below in conjunction with embodiment, the present invention is further elaborated。Should be appreciated that specific embodiment described herein is only in order to explain the present invention, is not intended to limit the present invention。

Embodiment 1

This suppresses and relay selection method based on the joint subcarrier in the many relay systems of two-way OFDM of PLNC, comprises the following steps:

Based on two-way many relay systems of TDMA by N number of via node { R₁,R₂,…R_NAnd two source node S₁,S₂Constituting, all nodes are equipped with single antenna and are operated in semiduplex mode, as shown in Figure 1。S₁Know S₁Channel condition information between each via node；S₂Know S₂Channel condition information between each via node。Two-way many relay systems based on TDMA adopt OFDM transmission mode, and subcarrier number K represents, subcarrier modulation modes is BPSK。S₁,S₂Channel to via node is multi-path Fading Channel, with vector h_iRepresent:

h_i=[h_i[0],h_i[1],…,h_i[L-1]]^TI=1,2

Wherein,L represents number of path。S₁,S₂To the channel independent same distribution of via node, the frequency domain channel on kth subcarrier is H_i[k]:

$H_i\&lsqb;k\&rsqb;=\underset{l=0}{\overset{L-1}{\&Sigma;}}{h}_i{\&lsqb;l\&rsqb;}^{-2j\mathrm{\&pi;}\frac{k}{K}l},i=1,2$

Information exchange each time can be divided into two stages: multiple access access phase and broadcast phase。

Multiple access access phase: first, S₁,S₂Kth subcarrier is respectively necessary for transmission informationThen, informationCan be expressed as after BPSK modulatesFinally, S₁,S₂InformationIt is sent to all of via node。Reception signal on the kth subcarrier of m-th relaying can be expressed as:

$Y_{R_m}^{\&lsqb;k\&rsqb;}=H_{1m}^{\&lsqb;k\&rsqb;}{X}_1^{\&lsqb;k\&rsqb;}+H_{2m}^{\&lsqb;k\&rsqb;}{X}_2^{\&lsqb;k\&rsqb;}+N_{R_m}^{\&lsqb;k\&rsqb;}$

Represent from S_iTo R_mBetween multi-path Fading Channel gain on kth subcarrier, m ∈ 1 ... N}, k ∈ 1 ... K}, i ∈ { 1,2}, and from S₁,S₂To via node and via node to S₁,S₂Channel be identical。Represent additive white Gaussian noise。

Broadcast phase: first, S₁,S₂All relayings select the relaying that a channel status is best；Then, the information received is broadcast to S by the mode that selected E-mail relay utilization decoding forwards₁,S₂；Finally, S₁,S₂The information received can be expressed as follows:

$Y_{S_1}^{\&lsqb;k\&rsqb;}=H_{1m}^{\&lsqb;k\&rsqb;}{X}_{R_m}^{\&lsqb;k\&rsqb;}+N_1^{\&lsqb;k\&rsqb;}$

$Y_{S_2}^{\&lsqb;k\&rsqb;}=H_{2m}^{\&lsqb;k\&rsqb;}{X}_{R_m}^{\&lsqb;k\&rsqb;}+N_2^{\&lsqb;k\&rsqb;}$

Represent the information that via node network code obtainsThe information obtained after BPSK modulates,Represent source node S_iThe information received,Represent additive white Gaussian noise, i ∈ { 1,2}。

Preferably, the joint subcarrier in the many relay systems of two-way OFDM of PLNC suppresses to be in that with the subcarrier inhibitory character in relay selection method:

The Multipath Transmission characteristic of wireless channel can cause frequency selective fading。In OFDM bidirectional relay system, the frequency selective fading of channel can cause different subcarriers to have different channel gains。Subcarrier suppresses to be the subcarrier transmission information good merely with channel condition, and the subcarrier of bad channel conditions abandon need not。WithRepresent suppression threshold, when the channel gain of subcarrier is higher thanTime, we define this subcarrier for " active sub-carriers "；Otherwise, when subcarrier channel gain lower thanTime, we define this subcarrier for " suppression subcarrier "。Whether each subcarrier is enliven to use subcarrier statusIt is expressed as follows:

$F_{im}^{\&lsqb;k\&rsqb;}=\left\{\begin{array}{ccc}1,& if& \left|{\hat{H}}_{im}^{\&lsqb;k\&rsqb;}\right|\&GreaterEqual;{\mathrm{\&lambda;}}_0^i\\ 0,& if& \left|{\hat{H}}_{im}^{\&lsqb;k\&rsqb;}\right|<{\mathrm{\&lambda;}}_0^i\end{array}\right.,i=1,2$

" 1 " represents that this subcarrier is active sub-carriers；" 0 " represents that this subcarrier is to suppress subcarrier。Represent from S_iTo R_mBetween multi-path Fading Channel estimated value of gain on kth subcarrier。When being only all " active sub-carriers " between two source nodes, this subcarrier just is used for transmitting information by relaying, is defined as " subcarrier of use "。System only uses " subcarrier of use " to transmit information and do not use repressed subcarrier。As it is shown on figure 3, therefore, whether kth subcarrier is relayed use by m-th can be used stateRepresent:

$F_{R_m}^{\&lsqb;k\&rsqb;}=F_{1m}^{\&lsqb;k\&rsqb;}{F}_{2m}^{\&lsqb;k\&rsqb;}$

IfThen this subcarrier is " subcarrier of use ", by relaying R_mUse；IfThen be abandoned need not for this subcarrier。

Preferably, a kind of joint subcarrier based in the many relay systems of two-way OFDM of PLNC suppresses to suppress to be characterised by with relay selection method with joint subcarrier in relay selection method:

Namely relay selection selects best one relaying of channel condition to be transmitted information in many relay systems, selects a relaying herein according to minimax principle:

$R^{*}=\arg \underset{m}{\max }\left\{\underset{k\&Element;I}{\min }\right\{\underset{i}{\min }\left\{\right|H_{im}^{\&lsqb;k\&rsqb;}\left|\right\}\left\}\right\}$

R^*Representing selected relaying, m represents that m-th relays, m ∈ 1 ... N}；The numbering of corresponding two source nodes of i, i ∈ { 1,2}；K represents kth subcarrier, k ∈ 1 ... K}；I represents the t easet ofasubcarriers of use, Represent from S_iTo R_mBetween multi-path Fading Channel modulus value of gain on kth subcarrier。

Different according to subcarrier suppressing method, in conjunction with minimax relay selection, the present invention proposes two kinds of joint subcarrier and suppresses and relay selection method: fix the JSSRS method (FNS-J) of the JSSRS method (FT-J) of suppression threshold, stator variable number。

Preferably, this based on the joint subcarrier in the many relay systems of two-way OFDM of PLNC suppress with relay selection method in fix the JSSRS method (FixThresholdbasedJSSRS, FT-J) of suppression threshold and be characterised by:

First FT-J carries out subcarrier suppression, and the relaying that then one channel condition of selection is best in all relayings carries out information transmission。Before subcarrier suppresses, S₁,S₂It needs to be determined that suppression threshold λ₀。The λ of FT-J₀Value is S₁,S₂The constant directly determined, this constant accesses at multiple access and remains unchanged during two time slots of broadcast。S₁,S₂Carry out suppressing operation to all subcarriers according to above-mentioned subcarrier suppressing method:

$F_{1im}^{\&lsqb;k\&rsqb;}=\left\{\begin{array}{ccc}1,& if& \left|{\hat{H}}_{im}^{\&lsqb;k\&rsqb;}\right|\&GreaterEqual;{\mathrm{\&lambda;}}_0\\ 0,& if& \left|{\hat{H}}_{im}^{\&lsqb;k\&rsqb;}\right|<{\mathrm{\&lambda;}}_0\end{array}\right.,i=1,2$

$F_{1R_m}^{\&lsqb;k\&rsqb;}=F_{11m}^{\&lsqb;k\&rsqb;}{F}_{12m}^{\&lsqb;k\&rsqb;}$

$H_{1im}^{\&lsqb;k\&rsqb;}=F_{1R_m}^{\&lsqb;k\&rsqb;}\&times;H_{im}^{\&lsqb;k\&rsqb;}$

Represent S_iSubcarrier status between relaying, " 1 " represents that this subcarrier is active sub-carriers；" 0 " represents that this subcarrier is to suppress subcarrier。Represent whether the subcarrier relaying the right and left is " subcarrier of use ",Represent that this subcarrier is " subcarrier of use ",Representing that this subcarrier is abandoned need not。Represent whether the channel of each subcarrier is used after subcarrier suppresses。Represent that " subcarrier of use " channel is used,Expression suppresses the channel of subcarrier to abandon need not。

The last relaying that one channel condition of selection is best in all relayings carries out information transmission。

$R^{*}=\arg \underset{m}{\max }\left\{\underset{k\&Element;I_1}{\min }\right\{\underset{i}{\min }\left\{\right|H_{1im}^{\&lsqb;k\&rsqb;}\left|\right\}\left\}\right\}$

R^*Representing selected relaying, m represents that m-th relays, m ∈ 1 ... N}；Corresponding two source nodes of i, i ∈ { 1,2}；K represents kth subcarrier, k ∈ 1 ... K}；I₁Represent the t easet ofasubcarriers used in FT-J method, Represent from S_iTo R_mBetween use sub-carrier channels modulus value of gain on kth subcarrier。

If λ₀Smaller, then some relaying has a suppressed subcarrier and some relaying is suppressed subcarrier, and so, the minimum channel gains of the subcarriers that all relayings use are different, after carrying out co-design with minimax relay selection, systematic function can be highly improved。But, if λ₀Relatively larger, the subcarrier of all relayings all experiences subcarrier to be suppressed, and the minimum channel gain of subcarrier that they use is almost identical, and in this case, then after carrying out minimax relay selection, systematic function can not improve。

Preferably, this suppresses to be in that with JSSRS (FixNumberofSubcarriersbasedJSSRS, the FNS-J) method feature of stator variable number in relay selection method based on the joint subcarrier in the many relay systems of two-way OFDM of PLNC:

Similar with FT-J, first FNS-J carries out subcarrier suppression, and the relaying that then one channel condition of selection is best in all relayings carries out information transmission。Before subcarrier suppresses, S₁,S₂It needs to be determined that suppression threshold λ₀。With FT-J the difference is that, FNS-J needs S₁,S₂First determine that number Q, the Q of the subcarrier of use are constants。Interim suppression threshold is determined, i.e. S according to constant Q₁,S₂Q the subcarrier selecting channel condition best in all K subcarriers transmits information (0 < Q≤K), channel gain molding good for QAs interim suppression threshold, namelyCarry out all subcarriers suppressing operation:

$F_{2im}^{\&lsqb;k\&rsqb;}=\left\{\begin{array}{ccc}1,& if& \left|{\hat{H}}_{im}^{\&lsqb;k\&rsqb;}\right|\&GreaterEqual;\left|H_{in}^{\&lsqb;Q\&rsqb;}\right|\\ 0,& if& \left|{\hat{H}}_{im}^{\&lsqb;k\&rsqb;}\right|<\left|H_{im}^{\&lsqb;Q\&rsqb;}\right|\end{array}\right.,i=1,2$

$F_{2R_m}^{\&lsqb;k\&rsqb;}=F_{21m}^{\&lsqb;k\&rsqb;}{F}_{22m}^{\&lsqb;k\&rsqb;}$

$H_{2im}^{\&lsqb;k\&rsqb;}=F_{2R_m}^{\&lsqb;k\&rsqb;}\&times;H_{im}^{\&lsqb;k\&rsqb;}$

Represent S_iSubcarrier status between relaying, " 1 " represents that this subcarrier is active sub-carriers；" 0 " represents that this subcarrier is to suppress subcarrier。Represent whether this subcarrier is " subcarrier of use ",Represent that this subcarrier is " subcarrier of use ",Representing that this subcarrier is abandoned need not。Represent and suppress whether the channel of each subcarrier is used through subcarrier。Represent that " subcarrier of use " channel is used,Expression suppresses the channel of subcarrier to abandon need not。

During multiple access accesses and broadcasts two time slots, Q immobilizes, and suppression threshold dynamically changes。Therefore, two suppression thresholds of same relayingDiffer；This threshold value of different relayings also differs。The last relay transmission information selecting a channel condition best in all relayings。

$R^{*}=\arg \underset{m}{\max }\left\{\underset{k\&Element;I_2}{\min }\right\{\underset{i}{\min }\left\{\right|H_{2im}^{\&lsqb;k\&rsqb;}\left|\right\}\left\}\right\}$

R^*Representing selected relaying, m represents that m-th relays, m ∈ 1 ... N}；Corresponding two source nodes of i, i ∈ { 1,2}；K represents kth subcarrier, k ∈ 1 ... K}；I₂Represent the t easet ofasubcarriers that FNS-J method uses, Represent from S_iTo R_mThe sub-carrier channels modulus value of gain on kth subcarrier used。

In FNS-J, no matter Q-value is big or little, each relaying will carry out subcarrier suppression, so the minimum channel gain of the subcarrier of each relaying use is different。Carry out relay selection in this case, the performance of system be improved significantly。

Preferably, this suppresses the relaying interpretation method with relay selection method to be characterised by based on the joint subcarrier in the many relay systems of two-way OFDM of PLNC:

According to decoding pass-through mode, adopt maximum-likelihood decoding。Selected relaying first has to calculate at multiple access access slot X₁It is c, X₂It it is the probability of d $P_m^{\&lsqb;k\&rsqb;}(c,d),c\&Element;\{+1,-1\},d\&Element;\{+1,-1\}:$

$P_m^{\&lsqb;k\&rsqb;}(+1,+1)\&Proportional;\exp (-\frac{|Y_{R_m}\&lsqb;k\&rsqb;-{\hat{H}}_{1m}^{\&lsqb;k\&rsqb;}-{\hat{H}}_{2m}^{\&lsqb;k\&rsqb;}{|}^2}{{\mathrm{\&sigma;}}^2})$

$P_m^{\&lsqb;k\&rsqb;}(-1,-1)\&Proportional;\exp (-\frac{|Y_{R_m}\&lsqb;k\&rsqb;+{\hat{H}}_{1m}^{\&lsqb;k\&rsqb;}+{\hat{H}}_{2m}^{\&lsqb;k\&rsqb;}{|}^2}{{\mathrm{\&sigma;}}^2})$

$P_m^{\&lsqb;k\&rsqb;}(+1,-1)\&Proportional;\exp (-\frac{|Y_{R_m}\&lsqb;k\&rsqb;-{\hat{H}}_{1m}^{\&lsqb;k\&rsqb;}+{\hat{H}}_{2m}^{\&lsqb;k\&rsqb;}{|}^2}{{\mathrm{\&sigma;}}^2})$

$P_m^{\&lsqb;k\&rsqb;}(-1,+1)\&Proportional;\exp (-\frac{|Y_{R_m}\&lsqb;k\&rsqb;+{\hat{H}}_{1m}^{\&lsqb;k\&rsqb;}-{\hat{H}}_{2m}^{\&lsqb;k\&rsqb;}{|}^2}{{\mathrm{\&sigma;}}^2}$

Wherein,RepresentEstimated value, σ²Represent noise variance。Then, selected relay reception is to S₁,S₂The information sentAfterwards it is carried out network code, useRepresentThe information obtained after carrying out network code, then have:

$A_{R_m}^{\&lsqb;k\&rsqb;}=\left\{\begin{array}{ccc}0,& if& P_m^{\&lsqb;k\&rsqb;}(+1,+1)+P_{R_m}\&lsqb;k\&rsqb;(-1,-1)\&GreaterEqual;P_m^{\&lsqb;k\&rsqb;}(+1,-1)+P_{R_m}\&lsqb;k\&rsqb;(-1,+1)\\ 1,& if& P_m^{\&lsqb;k\&rsqb;}(+1,+1)+P_{R_m}\&lsqb;k\&rsqb;(-1,-1)<P_m^{\&lsqb;k\&rsqb;}(+1,-1)+P_{R_m}\&lsqb;k\&rsqb;(-1,+1)\end{array}\right.$

Can be write as after BPSK modulatesSelected relaying againIt is broadcast to S₁,S₂。3rd step, S₁,S₂Receive the information that selected repeat broadcast comes, useRepresent。Result after equilibrium is usedRepresent,

Then have:

$M_{S_1}^{\&lsqb;k\&rsqb;}=Y_{S_1}^{\&lsqb;k\&rsqb;}/H_{1m}^{\&lsqb;k\&rsqb;}$

$M_{S_2}^{\&lsqb;k\&rsqb;}=Y_{S_2}^{\&lsqb;k\&rsqb;}/H_{2m}^{\&lsqb;k\&rsqb;}$

Finally, S₁,S₂The information received is demodulated according to following method:

$B_{S_1}^{\&lsqb;k\&rsqb;}=\left\{\begin{array}{ccc}0,& if& M_{S_1}^{\&lsqb;k\&rsqb;}<0\\ 1,& if& M_{S_1}^{\&lsqb;k\&rsqb;}\&GreaterEqual;0\end{array}\right.$

$B_{S_2}^{\&lsqb;k\&rsqb;}=\left\{\begin{array}{ccc}0,& if& M_{S_2}^{\&lsqb;k\&rsqb;}<0\\ 1,& if& M_{S_2}^{\&lsqb;k\&rsqb;}\&GreaterEqual;0\end{array}\right.$

Wherein,Represent S_iDemodulationAfter result, i ∈ { 1,2}。To sum up, S₁Reception signalS₂Reception signalFor:

$A_2^{\&lsqb;k\&rsqb;}=A_1^{\&lsqb;k\&rsqb;}\&CirclePlus;B_{S_1}^{\&lsqb;k\&rsqb;}$

$A_1^{\&lsqb;k\&rsqb;}=A_2^{\&lsqb;k\&rsqb;}\&CirclePlus;B_{S_2}^{\&lsqb;k\&rsqb;}$

Simulation result

Comprise in the OFDM bidirectional relay system of N number of relaying two kinds of JSSRS methods simulation result in bit error rate and throughput performance。The transmit power of source node and via node is set to 1, subcarrier number K=64, circulating prefix-length are 16, wireless multi-path channels is modeled as the 4 independent identically distributed Rayleigh channels in footpath。In whole simulation process, it is suppressed that thresholding λ represents, the subcarrier number of two source node uses is identical, for $Q_0^1=Q_0^2=Q.$

(1) bit error rate (BitErrorRate, BER) Performance Simulation Results

Fig. 4 provides the performance of BER curve of FT-J and FNS-J。FT-J and FNS-J combines subcarrier and suppresses the advantage with relay selection, and tradition subcarrier suppresses only to play the advantage that subcarrier suppresses an aspect。As shown in Figure 4, it is better than traditional subcarrier based on the error bit ability of FT-J and FNS-J in the two-way many relay systems of the OFDM of PLNC to suppress。Fig. 5 provides the performance of BER curve of FNS-J under different subcarrier the said conditions used。As it is shown in figure 5, the subcarrier number used is more few, the overall channel state of the subcarrier of use is more good, and bit error rate is more low；Relaying number is more many, and the channel status of the relaying chosen is more good, and bit error rate is more low。Further, when the subcarrier number used reduces, the superior function of relay selection accesses bigger performance, and FNS-J system performance gain raises。Fig. 6 provides the performance of BER curve of FT-J when different suppression threshold。As shown in Figure 6, it is suppressed that thresholding is more high, the overall channel state of the subcarrier of use is more good, and bit error rate is more low；Relaying number is more many, and the channel status of the relaying chosen is more good, and bit error rate is more low。Further, when suppression threshold raises, the performance of relay selection superiority is restricted, and FT-J system performance gain reduces。In Fig. 5, Fig. 6, SNR=10dB。

Fig. 7 provides the performance of BER of FT-J and FNS-J under different relaying said conditions。In Fig. 7, SNR=10dB。As it is shown in fig. 7, relaying number is more many, bit error rate is more low；The subcarrier number used is more few, and bit error rate is more low；Suppression threshold is more high, and bit error rate is more low。Further, FT-J, when suppression threshold is higher, increases relaying number and can not reduce system bit error rate further；When suppression threshold is higher, in FT-J method, the subcarrier of all relayings all experiences subcarrier suppression, and the minimum channel gain of the subcarrier that they use is almost identical, in this case, after carrying out minimax relay selection again, systematic function can not improve。And FNS-J is when the subcarrier number used is fewer, increases relaying number and remain able to reduction system bit error rate further。No matter the subcarrier number that FNS-J uses is many or few, the subcarrier of all relayings is all the subcarrier selecting channel condition best from top to bottom, the minimum channel gain of the subcarrier of its use is difference still, therefore after carrying out minimax relay selection again, systematic function remains to improve。Therefore, the performance of BER of FNS-J is better than FT-J。

Throughput performance simulation result

Handling capacity in the present invention is defined as the bit number that can correctly transmit in a time slot:

$T=\frac{Sum-Z}{2}$

Wherein, T represents handling capacity, and unit is that bit/pertimeslot, Sum represent total bit number of transmission in two time slots, and Z represents the bit number of error of transmission in two time slots。If the subcarrier number Q=K=64 used, namely all subcarriers all use and do not have noise jamming, then the ultimate throughput of system is:

$T_{max}=\frac{K}{2}=32$

Fig. 8 compares the throughput performance of FT-J and FNS-J。As shown in Figure 8, under Low SNR, FT-J and FNS-J combines subcarrier and suppresses the advantage with relay selection, and tradition subcarrier suppresses only to play subcarrier and suppresses the advantage of an aspect, therefore the throughput performance of FT-J and FNS-J is better than traditional subcarrier suppression；When high s/n ratio, throughput performance reaches a performance gain platform, and FT-J throughput performance is better than traditional subcarrier and suppresses, and the throughput performance of FNS-J suppresses identical with traditional subcarrier。

Fig. 9 gives the throughput performance curve of FNS-J under different subcarrier the said conditions used, and Figure 10 gives the throughput performance curve of FT-J when different suppression threshold。Fig. 9, in 10, SNR=10dB。As it is shown in figure 9, the subcarrier number used increases, total bit number of each slot transmission increases, and handling capacity increases；Relaying number increases, and system bit error rate reduces, therefore handling capacity increases。As shown in Figure 10, it is suppressed that thresholding increases, the subcarrier number of use reduces, and total bit number of each slot transmission reduces, therefore handling capacity reduces；Relaying number increases, and system bit error rate reduces, therefore handling capacity increases。It is linear relationship between the subcarrier number and the handling capacity that use in Fig. 8。In Figure 10, along with relaying number increases, it is suppressed that be no longer linear relationship between the subcarrier number of thresholding and use, therefore the linear relationship between suppression threshold and handling capacity changes。

Figure 11 gives when identical signal to noise ratio along with the throughput performance increasing FT-J and FNS-J of relaying number。As shown in figure 11, FNS-J increases along with the subcarrier number used, and throughput of system increases；FT-J is along with the reduction of suppression threshold, and throughput of system increases。Along with increasing of relaying number, the handling capacity of FNS-J increases, but because the subcarrier number used immobilizes, total bit number of each slot transmission is constant, therefore the handling capacity of FNS-J is maximum not over the subcarrier number Q used；But the handling capacity of FT-J increases along with relaying number and is continuously increased, when relaying number and being abundant, the superiority of relay selection performs to ultimate attainment, and system bit error rate is extremely low, it is possible to the limit amount of swallowing of approximation system。Therefore, the throughput performance of FT-J is better than FNS-J。

Claims (6)

1. one kind is suppressed and relay selection method based on the joint subcarrier in the many relay systems of two-way OFDM of PLNC, it is characterised in that comprise the following steps:

Based on two-way many relay systems of TDMA by N number of via node { R₁,R₂,…R_NAnd two source node S₁,S₂Constituting, all nodes are equipped with single antenna and are operated in semiduplex mode；S₁Know S₁Channel condition information between each via node；S₂Know S₂Channel condition information between each via node；Described two-way many relay systems based on TDMA adopt OFDM transmission mode, and subcarrier number K represents；S₁,S₂Channel to via node is multi-path Fading Channel, with vector h_iRepresent:

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

Wherein,L=0,1 ..., L-1, L represents number of path；S₁,S₂To the channel independent same distribution of via node, the frequency domain channel on kth subcarrier is H_i[k]:

$H_i\&lsqb;k\&rsqb;=\underset{l=0}{\overset{L-1}{\&Sigma;}}{h}_i\&lsqb;l\&rsqb;e^{-2j\mathrm{\&pi;}\frac{k}{K}l},i=1,2---\left(2\right)$

Information exchange each time can be divided into two stages: multiple access access phase and broadcast phase:

Multiple access access phase: first, S₁,S₂Kth subcarrier is respectively necessary for transmission informationThen, informationCan be expressed as after ovennodulationFinally, S₁,S₂InformationIt is sent to all of via node；Reception signal on the kth subcarrier of m-th relaying can be expressed as:

$Y_{R_m}^{\&lsqb;k\&rsqb;}=H_{1m}^{\&lsqb;k\&rsqb;}{X}_1^{\&lsqb;k\&rsqb;}+H_{2m}^{\&lsqb;k\&rsqb;}{X}_2^{\&lsqb;k\&rsqb;}+N_{R_m}^{\&lsqb;k\&rsqb;}---\left(3\right)$

Represent from S_iTo R_mBetween multi-path Fading Channel gain on kth subcarrier, m ∈ 1 ... N}, k ∈ 1 ... K}, i ∈ { 1,2}, and from S₁,S₂To via node and via node to S₁,S₂Channel be identical；Represent additive white Gaussian noise；

Broadcast phase: first, S₁,S₂All relayings select the relaying that a channel status is best；Then, the information received is broadcast to S by the mode that selected E-mail relay utilization decoding forwards₁,S₂；Finally, S₁,S₂The information received can be expressed as follows:

$Y_{S_1}^{\&lsqb;k\&rsqb;}=H_{1m}^{\&lsqb;k\&rsqb;}{X}_{R_m}^{\&lsqb;k\&rsqb;}+N_1^{\&lsqb;k\&rsqb;}---\left(4\right)$

$Y_{S_2}^{\&lsqb;k\&rsqb;}=H_{2m}^{\&lsqb;k\&rsqb;}{X}_{R_m}^{\&lsqb;k\&rsqb;}+N_2^{\&lsqb;k\&rsqb;}---\left(5\right)$

Represent the information that via node network code obtainsThe information obtained after ovennodulation,Represent source node S_iThe information received,Represent additive white Gaussian noise, i ∈ { 1,2}。

2. according to claim 1 based on the joint subcarrier suppression in the many relay systems of two-way OFDM of PLNC and relay selection method, it is characterised in that subcarrier suppresses to comprise the following steps:

Owing to the Multipath Transmission characteristic of wireless channel can cause frequency selective fading, based in two-way many relay systems of TDMA, the frequency selective fading of channel can cause different subcarriers to have different channel gains, subcarrier suppression is the subcarrier transmission information good merely with channel condition, and the subcarrier of bad channel conditions abandon need not, useRepresent suppression threshold, when the channel gain of subcarrier is higher thanTime, define this subcarrier for " active sub-carriers "；Otherwise, when subcarrier channel gain lower thanTime, define this subcarrier for " suppression subcarrier "；Whether each subcarrier is enliven to use subcarrier statusIt is expressed as follows:

$F_{im}^{\&lsqb;k\&rsqb;}=\left\{\begin{array}{ccc}1,& if& \left|{\hat{H}}_{im}^{\&lsqb;k\&rsqb;}\right|\&GreaterEqual;{\mathrm{\&lambda;}}_0^i\\ 0,& if& \left|{\hat{H}}_{im}^{\&lsqb;k\&rsqb;}\right|<{\mathrm{\&lambda;}}_0^i\end{array}\right.,i=1,2---\left(6\right)$

" 1 " represents that this subcarrier is active sub-carriers；" 0 " represents that this subcarrier is to suppress subcarrier；Represent from S_iTo R_mBetween multi-path Fading Channel estimated value of gain on kth subcarrier；When being only all " active sub-carriers " between two source nodes, this subcarrier just is used for transmitting information by relaying, is defined as " subcarrier of use "；System only uses " subcarrier of use " to transmit information and do not use repressed subcarrier；Therefore, whether kth subcarrier is relayed use by m-th and can use stateRepresent:

$F_{R_m}^{\&lsqb;k\&rsqb;}=F_{1m}^{\&lsqb;k\&rsqb;}{F}_{2m}^{\&lsqb;k\&rsqb;}---\left(7\right)$

IfThen this subcarrier is " subcarrier of use ", by relaying R_mUse；IfThen be abandoned need not for this subcarrier。

3. according to claim 1 based on the joint subcarrier suppression in the many relay systems of two-way OFDM of PLNC and relay selection method, it is characterised in that relay selection method comprises the following steps:

Select best one relaying of channel condition to be transmitted information in based on two-way many relay systems of TDMA, select a relaying according to minimax principle:

$R^{*}=\arg \underset{m}{max}\left\{\underset{k\&Element;I}{\min }\right\{\underset{i}{\min }\left|H_{im}^{\&lsqb;k\&rsqb;}\right|\left\}\right\}\}---\left(8\right)$

R^*Representing selected relaying, m represents that m-th relays, m ∈ 1 ... N}；The numbering of corresponding two source nodes of i, i ∈ { 1,2}；K represents kth subcarrier, k ∈ 1 ... K}；I represents the t easet ofasubcarriers of use, Represent from S_iTo R_mBetween multi-path Fading Channel modulus value of gain on kth subcarrier；

Different according to subcarrier suppressing method, in conjunction with minimax relay selection, described joint subcarrier suppresses to include with relay selection method: FT-J and FNS-J, FT-J are the fixing JSSRS method of suppression threshold, FNS-J is the JSSRS method of stator variable number。

4. according to claim 3 based on the joint subcarrier suppression in the many relay systems of two-way OFDM of PLNC and relay selection method, it is characterised in that the JSSRS method of fixing suppression threshold comprises the following steps:

First FT-J carries out subcarrier suppression, and the relaying that then one channel condition of selection is best in all relayings carries out information transmission；Before subcarrier suppresses, S₁,S₂It needs to be determined that suppression threshold λ₀；The λ of FT-J₀Value is S₁,S₂The constant directly determined, this constant accesses at multiple access and remains unchanged during two time slots of broadcast；S₁,S₂Carry out suppressing operation to all subcarriers according to above-mentioned subcarrier suppressing method:

$F_{1im}^{\&lsqb;k\&rsqb;}=\left\{\begin{array}{ccc}1,& if& \left|{\hat{H}}_{im}^{\&lsqb;k\&rsqb;}\right|\&GreaterEqual;{\mathrm{\&lambda;}}_0\\ 0,& if& \left|{\hat{H}}_{im}^{\&lsqb;k\&rsqb;}\right|<{\mathrm{\&lambda;}}_0\end{array}\right.,i=1,2---\left(9\right)$

$F_{1R_m}^{\&lsqb;k\&rsqb;}=F_{11m}^{\&lsqb;k\&rsqb;}{F}_{12m}^{\&lsqb;k\&rsqb;}---\left(10\right)$

$H_{1im}^{\&lsqb;k\&rsqb;}=F_{1R_m}^{\&lsqb;k\&rsqb;}\&times;H_{im}^{\&lsqb;k\&rsqb;}---\left(11\right)$

Represent S_iSubcarrier status between relaying, " 1 " represents that this subcarrier is active sub-carriers；" 0 " represents that this subcarrier is to suppress subcarrier；Represent whether the subcarrier relaying the right and left is " subcarrier of use ",Represent that this subcarrier is " subcarrier of use ",Representing that this subcarrier is abandoned need not；Represent whether the channel of each subcarrier is used after subcarrier suppresses；Represent that " subcarrier of use " channel is used,Expression suppresses the channel of subcarrier to abandon need not；

The last relaying that one channel condition of selection is best in all relayings carries out information transmission；

$R^{*}=\arg \underset{m}{\max }\left\{\underset{k\&Element;I_1}{\min }\right\{\underset{i}{\min }\left\{\right|H_{1im}^{\&lsqb;k\&rsqb;}\left|\right\}\left\}\right\}---\left(12\right)$

R^*Representing selected relaying, m represents that m-th relays, m ∈ 1 ... N}；Corresponding two source nodes of i, i ∈ { 1,2}；K represents kth subcarrier, k ∈ 1 ... K}；I₁Represent the t easet ofasubcarriers used in FT-J method, Represent from S_iTo R_mBetween use sub-carrier channels modulus value of gain on kth subcarrier。

5. according to claim 3 based on the joint subcarrier suppression in the many relay systems of two-way OFDM of PLNC and relay selection method, it is characterised in that the JSSRS method method of stator variable number comprises the following steps:

First FNS-J carries out subcarrier suppression, and the relaying that then one channel condition of selection is best in all relayings carries out information transmission；Before subcarrier suppresses, S₁,S₂It needs to be determined that suppression threshold λ₀；FNS-J needs S₁,S₂First determine that number Q, the Q of the subcarrier of use are constants；Interim suppression threshold is determined, i.e. S according to constant Q₁,S₂Q the subcarrier selecting channel condition best in all K subcarriers transmits information (0 < Q≤K), channel gain molding good for QAs interim suppression threshold, namelyCarry out all subcarriers suppressing operation:

$F_{2im}^{\&lsqb;k\&rsqb;}=\left\{\begin{array}{ccc}1,& if& \left|{\hat{H}}_{im}^{\&lsqb;k\&rsqb;}\right|\&GreaterEqual;\left|H_{im}^{\&lsqb;Q\&rsqb;}\right|\\ 0,& if& \left|{\hat{H}}_{im}^{\&lsqb;k\&rsqb;}\right|<\left|H_{im}^{\&lsqb;Q\&rsqb;}\right|\end{array}\right.,i=1,2---\left(13\right)$

$F_{2R_m}^{\&lsqb;k\&rsqb;}=F_{21m}^{\&lsqb;k\&rsqb;}{F}_{22m}^{\&lsqb;k\&rsqb;}---\left(14\right)$

$H_{2im}^{\&lsqb;k\&rsqb;}=F_{2R_m}^{\&lsqb;k\&rsqb;}\&times;H_{im}^{\&lsqb;k\&rsqb;}---\left(15\right)$

Represent S_iSubcarrier status between relaying, " 1 " represents that this subcarrier is active sub-carriers；" 0 " represents that this subcarrier is to suppress subcarrier；Represent whether this subcarrier is " subcarrier of use ",Represent that this subcarrier is " subcarrier of use ",Representing that this subcarrier is abandoned need not；Represent and suppress whether the channel of each subcarrier is used through subcarrier；Represent that " subcarrier of use " channel is used,Expression suppresses the channel of subcarrier to abandon need not；

During multiple access accesses and broadcasts two time slots, Q immobilizes, and suppression threshold dynamically changes；Therefore, two suppression thresholds of same relayingDiffer；This threshold value of different relayings also differs；The last relay transmission information selecting a channel condition best in all relayings:

$R^{*}=\arg \underset{m}{max}\left\{\underset{k\&Element;I_2}{\min }\right\{\underset{i}{\min }\left\{\right|H_{2im}^{\&lsqb;k\&rsqb;}\left|\right\}\left\}\right\}---\left(16\right)$

R^*Representing selected relaying, m represents that m-th relays, m ∈ 1 ... N}；Corresponding two source nodes of i, i ∈ { 1,2}；K represents kth subcarrier, k ∈ 1 ... K}；I₂Represent the t easet ofasubcarriers that FNS-J method uses, Represent from S_iTo R_mThe sub-carrier channels modulus value of gain on kth subcarrier used。

6. according to claim 1 based on the joint subcarrier suppression in the many relay systems of two-way OFDM of PLNC and relay selection method, it is characterised in that relaying physical-layer network coding method comprises the following steps:

According to decoding pass-through mode, adopt maximum-likelihood decoding；Selected relaying first has to calculate at multiple access access slot X₁It is c, X₂It it is the probability of dBPSK is modulated, c ∈+1 ,-1}, d ∈+1 ,-1}:

$\begin{array}{c}{P}_m^{\&lsqb;k\&rsqb;}(+1,+1)\&Proportional;\exp (-\frac{{\left|Y_{R_m}\&lsqb;k\&rsqb;-{\hat{H}}_{1m}^{\&lsqb;k\&rsqb;}-{\hat{H}}_{2m}^{\&lsqb;k\&rsqb;}\right|}^2}{{\mathrm{\&sigma;}}^2})\\ P_m^{\&lsqb;k\&rsqb;}(-1,-1)\&Proportional;\exp (-\frac{{\left|Y_{R_m}\&lsqb;k\&rsqb;+{\hat{H}}_{1m}^{\&lsqb;k\&rsqb;}+{\hat{H}}_{2m}^{\&lsqb;k\&rsqb;}\right|}^2}{{\mathrm{\&sigma;}}^2})\\ P_m^{\&lsqb;k\&rsqb;}(+1,-1)\&Proportional;\exp (-\frac{{\left|Y_{R_m}\&lsqb;k\&rsqb;+{\hat{H}}_{1m}^{\&lsqb;k\&rsqb;}+{\hat{H}}_{2m}^{\&lsqb;k\&rsqb;}\right|}^2}{{\mathrm{\&sigma;}}^2})\\ P_m^{\&lsqb;k\&rsqb;}(-1,+1)\&Proportional;\exp (-\frac{{\left|Y_{R_m}\&lsqb;k\&rsqb;+{\hat{H}}_{1m}^{\&lsqb;k\&rsqb;}+{\hat{H}}_{2m}^{\&lsqb;k\&rsqb;}\right|}^2}{{\mathrm{\&sigma;}}^2}\end{array}---\left(17\right)$

Wherein,RepresentEstimated value, σ²Represent noise variance；Then, selected relay reception is to S₁,S₂The information sentAfterwards it is carried out network code, useRepresentThe information obtained after carrying out network code, then have:

$A_{R_m}^{\&lsqb;k\&rsqb;}=\left\{\begin{array}{ccc}0,& if& P_m^{\&lsqb;k\&rsqb;}(+1,+1)+P_{R_m}\&lsqb;k\&rsqb;(-1,-1)\&GreaterEqual;P_m^{\&lsqb;k\&rsqb;}(+1,-1)+P_{R_m}\&lsqb;k\&rsqb;(-1,+1)\\ 1,& if& P_m^{\&lsqb;k\&rsqb;}(+1,+1)+P_{R_m}\&lsqb;k\&rsqb;(-1,-1)<P_m^{\&lsqb;k\&rsqb;}(+1,-1)+P_{R_m}\&lsqb;k\&rsqb;(-1,+1)\end{array}\right.---\left(18\right)$

Can be write as after BPSK modulatesSelected relaying againIt is broadcast to S₁,S₂；3rd step, S₁,S₂Receive the information that selected repeat broadcast comes, useRepresent；Result after equilibrium is usedRepresent, then have:

$M_{S_1}^{\&lsqb;k\&rsqb;}=Y_{S_1}^{\&lsqb;k\&rsqb;}/H_{1m}^{\&lsqb;k\&rsqb;}---\left(19\right)$

$M_{S_2}^{\&lsqb;k\&rsqb;}=Y_{S_2}^{\&lsqb;k\&rsqb;}/H_{2m}^{\&lsqb;k\&rsqb;}---\left(20\right)$

Finally, S₁,S₂The information received is demodulated according to following method:

$B_{S_1}^{\&lsqb;k\&rsqb;}=\left\{\begin{array}{ccc}0,& if& M_{S_1}^{\&lsqb;k\&rsqb;}<0\\ 1,& if& M_{S_1}^{\&lsqb;k\&rsqb;}\&GreaterEqual;0\end{array}\right.---\left(21\right)$

$B_{S_2}^{\&lsqb;k\&rsqb;}=\left\{\begin{array}{ccc}0,& if& M_{S_2}^{\&lsqb;k\&rsqb;}<0\\ 1,& if& M_{S_2}^{\&lsqb;k\&rsqb;}\&GreaterEqual;0\end{array}\right.---\left(22\right)$

Wherein,Represent S_iDemodulationAfter result, i ∈ { 1,2}；To sum up, S₁Reception signalS₂Reception signalFor:

$A_2^{\&lsqb;k\&rsqb;}=A_1^{\&lsqb;k\&rsqb;}\&CirclePlus;B_{S_1}^{\&lsqb;k\&rsqb;}---\left(23\right)$

$A_1^{\&lsqb;k\&rsqb;}=A_2^{\&lsqb;k\&rsqb;}\&CirclePlus;B_{S_2}^{\&lsqb;k\&rsqb;}---\left(24\right)$ 。