CN102142874A - Physical layer network coding-based joint antenna selection space multiplexing method - Google Patents

Abstract

The invention relates to a physical layer network coding-based joint antenna selection space multiplexing method, and belongs to the technical field of wireless communication. The method comprises the following steps that: a relay selects an antenna set which participates in communication; two users which perform bidirectional communication transmit pre-coded information to the relay at the same time; the relay performs physical layer network coding maximum likelihood detection on superimposed signals from different users to directly obtain network coding symbols; the relay broadcasts the network coding symbols back to the users; and the users decode the pre-coded information and extract the information of the other user by utilizing self-information. By the method, the frequency spectrum utilization efficiency and the energy utilization efficiency of a bidirectional delay network are improved effectively, multi-stream high-speed transmission is realized, and relay decoding complexity is reduced.

Description

A kind of joint antenna based on physical-layer network coding is selected method for spacial multiplex

Technical field

The present invention relates to a kind of joint antenna and select method for spacial multiplex, belong to wireless communication technology field based on physical-layer network coding.

Background technology

Two-way communication is the common means in the communication, and such as real-time interactive document between the user, business such as video calling, special-purpose supervisory control system etc. all need reliable two-way communication.Because the interval, geographical position or the channel quality that direct transfers are abominable, expectation realizes user's networking realization reliable communication voluntarily of two-way communication, at this time can utilize relaying to assist to finish two-way communication.Physical-layer network coding utilizes the broadcasting of transmission of wireless signals and superimposed characteristics and advanced signal detecting method, can for these users that expect interactive information to information transmission reliably at a high speed is provided.Simultaneously, the application of physical-layer network coding can effectively improve the availability of frequency spectrum and the capacity usage ratio of network integral body, thereby realizes two-way communication efficient, environmental protection, meets the demand of following green communications.

At present physical-layer network coding has received the concern of academia and industrial circle gradually, wherein is applied in physical-layer network coding that physical-layer network coding in the two-way communication comprises that mainly decoding is transmitted based on part and based on amplifying the analog network coding of transmitting.Wherein, the communication protocol of physical-layer network coding is as follows: the user that two-way communication is carried out in two hope finishes its uplink to utilizing identical running time-frequency resource, the base station end with overlapping or mutually interference signals directly be mapped as the symbol of network code, it is right that symbol after utilizing frequency resource when certain with this network code then is broadcast to this user, the user is after receiving the symbol of network code, after utilizing own existing information to carry out interference eliminated, obtain useful information from the other side.In addition, the communication protocol of analog network coding is as follows: the user that two-way communication is carried out in two hope finishes its uplink to utilizing identical running time-frequency resource, the base station end is with overlapping or to be broadcast to this user after interference signals is directly amplified mutually right, the user is after receiving the symbol of network code, after utilizing own existing information to carry out interference eliminated, obtain useful information from the other side.In two kinds of physical-layer network codings, physical-layer network coding has higher capacity usage ratio, more meets the demand of future communications.

Spatial reuse utilizes many antenna transmitter/receiver apparatus and advanced signal processing technology effectively to utilize the degree of freedom that multi-antenna channel brings to improve the availability of frequency spectrum.Especially, for the auxiliary collaborative network of relaying, relaying and user terminal have many antennas usually, and at the method for spacial multiplex of physical-layer network coding, also rarely have report at present.Practical space division multiplexing method uses linear receiver usually; Though linear receiver has comparatively simple implementation complexity, often can't utilize the many days potential diversity gains of receiver based on the SDM system of linear receiver, a little less than this makes the anti-channel fading ability of system.

Summary of the invention

The objective of the invention is to propose a kind of joint antenna and select method for spacial multiplex based on physical-layer network coding, employing is selected and the receiving and transmitting signal processing method based on the efficient two-way communication strategy of physical-layer network coding with at the joint antenna of multithread transmission, to improve the anti-fading ability of system channel.

The joint antenna based on physical-layer network coding that the present invention proposes is selected method for spacial multiplex, may further comprise the steps:

(1) establish two users that carry out the full rate interactive communication, each user has N root antenna, and a relay station with M antenna is set between two users, and user and relay station constitute a communication network, wherein M＞N 〉=2;

(2) relay station in the communication network sends training data respectively to two users, and the user estimates to obtain channel information between this user antenna and the relay station antenna according to the training data that receives, and then obtains the channel matrix between relay station antenna and the user antenna

K=1,2;

(3) two channel matrixes that the user obtains according to above-mentioned steps (2) respectively calculate all candidate pre-coding matrixes relevant with candidate channel, and respectively the set of the Frobenius norm of candidate's pre-coding matrix are fed back to relay station, and concrete steps are as follows:

(3-1) tag set of establishing the relay station antenna be Φ=1,2 ..., M}, random choose goes out relay station candidate antenna set of N root antenna composition from relay station M root antenna, is expressed as

And set φ _lIn element number be | φ _l|=N, according to permutation and combination rule, wherein φ _lBe variable, total

Plant the mode of selecting,

(3-2) channel matrix that obtains according to above-mentioned steps (2) The relay station candidate antenna set φ that obtains and select _lCorresponding candidate channel

Wherein

In element obey the multiple Gaussian Profile of independent identically distributed zero-mean unit variance;

(3-3) k user obtains according to above-mentioned steps (3-2)

Employing calculates based on the linear pre-coding method of ZF

Candidate's pre-coding matrix be And calculated candidate pre-coding matrix

The Frobenius norm

(3-4) repeating step (3-2) and (3-3) is according to different relay station candidate antenna set φ _l, constitute the set of candidate's pre-coding matrix norm

C wherein _kThe element number that comprises is

K user will gather C by feedback channel _kSend to relay station;

(4) the set C that obtains according to step (3) of relay station _k, to carry out the antenna set and select, and notify two users selection result, detailed process is as follows:

(4-1) relay station obtains according to step (3-3) Calculate and select measure value

(4-2) relay station is from the relay station candidate antenna set φ of above-mentioned steps (3) _lIn select optimum antenna candidate collection φ ^*The antenna that participates in two user interactions communications as relay station is gathered,

The criterion of selecting is:

${\mathrm{\φ}}^{*}=\arg \underset{{\mathrm{\φ}}_l\⋐\mathrm{\Φ}}{\max }\left(\min ({\mathrm{\β}}_{{\mathrm{\φ}}_l,1},{\mathrm{\β}}_{{\mathrm{\φ}}_l,2})\right);$

(4-3) relay station is gathered φ with antenna ^*Be broadcast to two users;

(5) two users respectively by the two-phase PSK modulation system to needing interactive information x separately ₁And x ₂Modulate x _k=[x _{K, 1}, x _{K, 2}..., x _{K, i}X _{K, N}] ^T, k=1,2, i=1,2 ... N, and utilize respectively and φ ^*Corresponding pre-coding matrix

Need interactive information after the modulation is carried out sending by user's sky alignment relay station separately after the precoding;

(6) relay station receives the signal that above-mentioned two users send, and obtains two users' multiple-input and multiple-output transmitted in both directions superposed signal y=[y ₁, y ₂..., y _N] ^T

(7) relay station according in the above-mentioned steps (3-3) with φ ^*The Frobenius norm of corresponding pre-coding matrix is carried out physical-layer network coding to the transmitted in both directions superposed signal that receives and is detected, and obtains the network code symbol Detailed process is as follows:

(7-1) relay station obtains two users' equivalent channel gain according to the Frobenius norm calculation of the pre-coding matrix of two user feedbacks in the step (3-3)

With

(7-2) relay station utilizes above-mentioned equivalent channel gain to i superposed signal y _iCarry out Maximum Likelihood Detection, obtain i network code symbol

The detection expression formula is:

${\hat{x}}_i=\left\{\begin{array}{cc}1& e^{\left(\frac{\widetilde{\mathrm{\&Lambda;}}\left(\mathrm{1,1}\right)}{{\mathrm{\&sigma;}}_r}\right)}+e^{\left(\frac{\widetilde{\mathrm{\&Lambda;}}(-1,-1)}{{\mathrm{\&sigma;}}_r}\right)}\&GreaterEqual;e^{\left(\frac{\widetilde{\mathrm{\&Lambda;}}(-\mathrm{1,1})}{{\mathrm{\&sigma;}}_r}\right)}+e^{\left(\frac{\widetilde{\mathrm{\&Lambda;}}(1,-1)}{{\mathrm{\&sigma;}}_r}\right)}\\ -1& e^{\left(\frac{\widetilde{\mathrm{\&Lambda;}}\left(\mathrm{1,1}\right)}{{\mathrm{\&sigma;}}_r}\right)}+e^{\left(\frac{\widetilde{\mathrm{\&Lambda;}}(-1,-1)}{{\mathrm{\&sigma;}}_r}\right)}<e^{\left(\frac{\widetilde{\mathrm{\&Lambda;}}(-\mathrm{1,1})}{{\mathrm{\&sigma;}}_r}\right)}+e^{\left(\frac{\widetilde{\mathrm{\&Lambda;}}(1,-1)}{{\mathrm{\&sigma;}}_r}\right)}\end{array}\right.,$

Wherein

σ _rIt is the noise variance of relay station;

(8) relay station is with above-mentioned network code symbol

Send to two users, the transmission signal is E wherein _{B, r}It is the transmission energy of every antenna of relay station;

(9) two users receive the transmission signal s of relay station respectively, utilize the pre-coding matrix of above-mentioned steps (3) to make up decoding matrix, to send that signal is decoded and demodulation after, obtain respectively separately for the restituted signal that sends signal K=1,2;

(10) two users are respectively according to the need interactive information x of above-mentioned steps (5) ₁And x ₂, restituted signal is separately deciphered, obtain the other user's data message

K=1,2, wherein ⊙ is that Hadamard is long-pending.

The joint antenna based on physical-layer network coding that the present invention proposes is selected method for spacial multiplex, has effectively improved the availability of frequency spectrum and the energy utilization efficiency of two-way junction network; Effectively utilize the degree of freedom of multiwire channel, realized the multithread high-speed transfer of communication network; The inventive method has been utilized the symmetrical characteristics of two-way channel, has reduced the complexity of relay station decoding by the precoding design of transmitting terminal; This method provides diversity gain by the multithread information that antenna is chosen as two-way interactive.

Description of drawings

Fig. 1 implements in the distributing antenna system of the inventive method the user to the two-way communication schematic diagram.

Fig. 2 is the FB(flow block) of day line options in the inventive method.

Fig. 3 is the FB(flow block) of signal transmission in the inventive method.

Embodiment

The joint antenna based on physical-layer network coding that the present invention proposes is selected method for spacial multiplex, and its FB(flow block) may further comprise the steps as shown in Figure 3:

(1) establishes two users that carry out the full rate interactive communication, each user has N root antenna, relay station with M antenna is set between two users, user and relay station constitute a communication network, as shown in Figure 1, the half-duplex relay station R that forms of selected user S_1 that carries out information interaction and S_2 and spaced antenna together constitutes communication network.

(2) relay station in the communication network sends training data respectively to two users, and the user estimates to obtain channel information between this user antenna and the relay station antenna according to the training data that receives, and then obtains the channel matrix between relay station antenna and the user antenna

K=1,2; Set

Be falt fading channel, obey the multiple Gaussian random variable of independent identically distributed 0 average and unit variance, promptly

I wherein _MIt is the unit vector of M * N.

(3) two channel matrixes that the user obtains according to above-mentioned steps (2) respectively calculate all candidate pre-coding matrixes relevant with candidate channel, and respectively the set of the Frobenius norm of pre-coding matrix are fed back to relay station.Concrete steps are as follows:

(3-1) tag set of establishing the relay station antenna be Φ=1,2 ..., M}, random choose goes out N root antenna and forms a relay station candidate antenna set from relay station M root antenna, is expressed as

And set φ _lIn element number be | φ _l|=N, according to permutation and combination rule, wherein φ _lBe variable, total

Plant the mode of selecting,

(3-2) channel matrix that obtains according to above-mentioned steps (2)

The relay station candidate antenna set φ that obtains and select _lCorresponding candidate channel

Wherein

In element obey the multiple Gaussian Profile of independent identically distributed zero-mean unit variance;

(3-3) k user obtains according to above-mentioned steps (3-2) Employing calculates based on the linear pre-coding method of ZF

Candidate's pre-coding matrix be

And calculated candidate pre-coding matrix

The Frobenius norm

(3-4) repeating step (3-2) and (3-3) is according to different relay station candidate antenna set φ _l, constitute the set of candidate's pre-coding matrix norm

C wherein _kThe element number that comprises is

K user will gather C by feedback channel _kSend to relay station;

(4) the set C that obtains according to step (3) of relay station _k, to carry out the antenna set and select, and notify two users selection result, its FB(flow block) is shown in soil, and detailed process is as follows:

(4-1) relay station obtains according to step (3-3)

Calculate and select measure value

(4-2) relay station is from the relay station candidate antenna set φ of above-mentioned steps (3) _lIn select optimum antenna candidate collection φ ^*The antenna that participates in two user interactions communications as relay station is gathered, The criterion of selecting is:

${\mathrm{\&phi;}}^{*}=\arg \underset{{\mathrm{\&phi;}}_l\&Subset;\mathrm{\&Phi;}}{\max }\left(\min ({\mathrm{\&beta;}}_{{\mathrm{\&phi;}}_l,1},{\mathrm{\&beta;}}_{{\mathrm{\&phi;}}_l,2})\right);$

(4-3) relay station is gathered φ with antenna ^*Be broadcast to two users.

(5) two users pass through the two-phase PSK modulation system respectively to need interactive information x ₁And x ₂Modulate x _k=[x _{K, 1}, x _{K, 2}..., x _{K, i}X _{K, N}] ^T, k=1,2, i=1,2 ... N, and utilize respectively and φ ^*Corresponding pre-coding matrix

Need interactive information after the modulation is carried out sending by user's sky alignment relay station separately after the precoding.User S_k to the transmission signal of relay station R is Wherein, x _k=[x _{K, 1}, x _{K, 2}..., x _{K, N}] ^TFor user S_k sends to the other user's data message, Be the ZF pre-coding matrix of user S_k to relay station R,

Being the average energy normalization factor, is E with the average transmission energy of guarantor unit's symbol _{B, k}, E _{B, k}Be the transmission energy of every antenna of user S_k, unfinished being convenient to set forth, and supposes E _{B, 1}=E _{B, 2}=E _b

(6) relay station receives the signal that above-mentioned two users send, and obtains two users' multiple-input and multiple-output transmitted in both directions superposed signal y=[y ₁, y ₂..., y _N] ^TThe received signal of relay station R is

$Y=H_1{s}_1+H_2{s}_2+n$

$={\mathrm{\&alpha;}}_1{H}_1{T}_{{\mathrm{\&phi;}}^{*},1}{x}_1+{\mathrm{\&alpha;}}_2{H}_2{T}_{{\mathrm{\&phi;}}^{*},2}{x}_2+n$

${=I}_N({\mathrm{\&alpha;}}_1{x}_1+{\mathrm{\&alpha;}}_2{x}_2)+n$

N=[n wherein ₁, n ₂..., n _i..., n _N] ^TBe noise vector,

I=1,2 ..., N is independent identically distributed multiple Gaussian random variable.Be N parallel single input single output (SISO) data flow from two users through the equivalence of multiple-input and multiple-output (MIMO) transmitted in both directions signal by what following formula obtained that relay station R receives.

(7) relay station according in the above-mentioned steps (3-3) with φ ^*The Frobenius norm of corresponding pre-coding matrix is carried out physical-layer network coding to the parallel single output of single input (SISO) data flow of the equivalence that receives and is detected, and obtains the network code symbol

Detailed process is as follows:

(7-1) relay station obtains two users' equivalent channel gain according to the Frobenius norm calculation of the pre-coding matrix of two user feedbacks in the step (3-3)

With

I the superposed signal that relay station R receives is expressed as y _i=α ₁x _{1, i}+ α ₂x _{2, i}+ n _i, x wherein _{K, i}, k=1,2, be i interactive information of user S_k transmission.

(7-2) relay station R utilizes above-mentioned equivalent channel gain to i superposed signal y _iCarry out Maximum Likelihood Detection, obtain i network code symbol

The detection expression formula is:

${\hat{x}}_i=\left\{\begin{array}{cc}1& e^{\left(\frac{\widetilde{\mathrm{\&Lambda;}}\left(\mathrm{1,1}\right)}{{\mathrm{\&sigma;}}_r}\right)}+e^{\left(\frac{\widetilde{\mathrm{\&Lambda;}}(-1,-1)}{{\mathrm{\&sigma;}}_r}\right)}\&GreaterEqual;e^{\left(\frac{\widetilde{\mathrm{\&Lambda;}}(-\mathrm{1,1})}{{\mathrm{\&sigma;}}_r}\right)}+e^{\left(\frac{\widetilde{\mathrm{\&Lambda;}}(1,-1)}{{\mathrm{\&sigma;}}_r}\right)}\\ -1& e^{\left(\frac{\widetilde{\mathrm{\&Lambda;}}\left(\mathrm{1,1}\right)}{{\mathrm{\&sigma;}}_r}\right)}+e^{\left(\frac{\widetilde{\mathrm{\&Lambda;}}(-1,-1)}{{\mathrm{\&sigma;}}_r}\right)}<e^{\left(\frac{\widetilde{\mathrm{\&Lambda;}}(-\mathrm{1,1})}{{\mathrm{\&sigma;}}_r}\right)}+e^{\left(\frac{\widetilde{\mathrm{\&Lambda;}}(1,-1)}{{\mathrm{\&sigma;}}_r}\right)}\end{array}\right.,$

Wherein

σ _rIt is the noise variance of relay station.

Concrete derivation is as follows:

Detect judgement based on following basic binary system hypothesis testing after the superposed signal that relaying R reception two users S_1 and S_2 send:

H ₀：x ₁＝x _1，1x _2，1＝1，

H ₁：x ₁＝x _1，1x _2，1＝-1.

Wherein, x _iIt is the network code symbol that the relaying expectation recovers.It is right to introduce check character for ease of mark

Wherein Ω={ ± 1} * { ± 1} is a signal space.Y then _iThe condition joint probability density function be:

$p(y_i/H_0,A)=C_1(e^{\left(\frac{\widetilde{\mathrm{\&Lambda;}}\left(\mathrm{1,1}\right)}{{\mathrm{\&sigma;}}_r}\right)}+e^{\left(\frac{\widetilde{\mathrm{\&Lambda;}}(-1,-1)}{{\mathrm{\&sigma;}}_r}\right)}),$

$p(y_i/H_1,A)=C_1(e^{\left(\frac{\widetilde{\mathrm{\&Lambda;}}(-\mathrm{1,1})}{{\mathrm{\&sigma;}}_r}\right)}+e^{\left(\frac{\widetilde{\mathrm{\&Lambda;}}(1,-1)}{{\mathrm{\&sigma;}}_r}\right)}).$

C wherein ₁Be constant,

Be to receive waveform y _iWith the check waveform Distance measure, A=[α ₁, α ₂] ^T, σ _rBe the noise variance of relay station, ‖ ‖ _FIt is the Frobenius norm of vector or matrix.Suppose that information source etc. is general, the maximum-likelihood criterion of physical-layer network coding provides with following form:

$x_i=\left\{\begin{array}{cc}1& p(y_i/H_0,A)\&GreaterEqual;p(y_i/H_1,A)\\ -1& p(y_i/H_0,A)<p(y_i/H_1,A)\end{array}\right.,$

Abbreviation obtains

$x_i=\left\{\begin{array}{cc}1& e^{\left(\frac{\widetilde{\mathrm{\&Lambda;}}\left(\mathrm{1,1}\right)}{{\mathrm{\&sigma;}}_r}\right)}+e^{\left(\frac{\widetilde{\mathrm{\&Lambda;}}(-1,-1)}{{\mathrm{\&sigma;}}_r}\right)}\&GreaterEqual;e^{\left(\frac{\widetilde{\mathrm{\&Lambda;}}(-\mathrm{1,1})}{{\mathrm{\&sigma;}}_r}\right)}+e^{\left(\frac{\widetilde{\mathrm{\&Lambda;}}(1,-1)}{{\mathrm{\&sigma;}}_r}\right)}\\ -1& e^{\left(\frac{\widetilde{\mathrm{\&Lambda;}}\left(\mathrm{1,1}\right)}{{\mathrm{\&sigma;}}_r}\right)}+e^{\left(\frac{\widetilde{\mathrm{\&Lambda;}}(-1,-1)}{{\mathrm{\&sigma;}}_r}\right)}<e^{\left(\frac{\widetilde{\mathrm{\&Lambda;}}(-\mathrm{1,1})}{{\mathrm{\&sigma;}}_r}\right)}+e^{\left(\frac{\widetilde{\mathrm{\&Lambda;}}(1,-1)}{{\mathrm{\&sigma;}}_r}\right)}\end{array}\right..$

(8) relay station is with above-mentioned network code symbol

Send to two users, the transmission signal is

E wherein _{B, r}It is the transmission energy of every antenna of relay station.

(9) two users receive the transmission signal s of relay station respectively, utilize the pre-coding matrix of above-mentioned steps (3-3) to make up decoding matrix, to send that signal is decoded and demodulation after, obtain respectively separately for the restituted signal that sends signal

K=1,2, i=1,2 ... N.The received signal of user S_k is

Obtain decoding according to broken zero pre-coding matrix in the step (3)

User S_k obtains decoded signal Wherein

Decoded signal is carried out two-phase PSK BPSK demodulation, and user S_k is to i decoded signal

The judgement form be

Sign () is-symbol polarity function wherein finally obtains the restituted signal of user S_k

(10) two users need interactive information x separately according to above-mentioned steps (5) respectively ₁And x ₂, restituted signal is separately deciphered, obtain the other user's data message

K=1,2, wherein ⊙ is that Hadamard is long-pending.

Claims (1)

1. the joint antenna based on physical-layer network coding is selected method for spacial multiplex, it is characterized in that this method may further comprise the steps:

(1) establish two users that carry out the full rate interactive communication, each user has N root antenna, and a relay station with M antenna is set between two users, and user and relay station constitute a communication network, wherein M＞N 〉=2;

(2) relay station in the communication network sends training data respectively to two users, and the user estimates to obtain channel information between this user antenna and the relay station antenna according to the training data that receives, and then obtains the channel matrix between relay station antenna and the user antenna

K=1,2;

(3) two channel matrixes that the user obtains according to above-mentioned steps (2) respectively calculate all candidate pre-coding matrixes relevant with candidate channel, and respectively the set of the Frobenius norm of candidate's pre-coding matrix are fed back to relay station, and concrete steps are as follows:

(3-1) tag set of establishing the relay station antenna be Φ=1,2 ..., M}, random choose goes out relay station candidate antenna set of N root antenna composition from relay station M root antenna, is expressed as

And set φ _lIn element number be | φ _l|=N, according to permutation and combination rule, wherein φ _lBe variable, total Plant the mode of selecting,

(3-2) channel matrix that obtains according to above-mentioned steps (2)

The relay station candidate antenna set φ that obtains and select _lCorresponding candidate channel

Wherein

In element obey the multiple Gaussian Profile of independent identically distributed zero-mean unit variance;

(3-3) k user obtains according to above-mentioned steps (3-2)

Employing calculates based on the linear pre-coding method of ZF

Candidate's pre-coding matrix be

And calculated candidate pre-coding matrix

The Frobenius norm

(3-4) repeating step (3-2) and (3-3) is according to different relay station candidate antenna set φ _l, constitute the set of candidate's pre-coding matrix norm

C wherein _kThe element number that comprises is K user will gather C by feedback channel _kSend to relay station;

(4) the set C that obtains according to step (3) of relay station _k, to carry out the antenna set and select, and notify two users selection result, detailed process is as follows:

(4-1) relay station obtains according to step (3-3)

Calculate and select measure value

(4-2) relay station is from the relay station candidate antenna set φ of above-mentioned steps (3) _lIn select optimum antenna candidate collection φ ^*The antenna that participates in two user interactions communications as relay station is gathered,

The criterion of selecting is:

${\mathrm{\&phi;}}^{*}=\arg \underset{{\mathrm{\&phi;}}_l\&Subset;\mathrm{\&Phi;}}{\max }\left(\min ({\mathrm{\&beta;}}_{{\mathrm{\&phi;}}_l,1},{\mathrm{\&beta;}}_{{\mathrm{\&phi;}}_l,2})\right);$

(4-3) relay station is gathered φ with antenna ^*Be broadcast to two users;

(5) two users respectively by the two-phase PSK modulation system to needing interactive information x separately ₁And x ₂Modulate x _k=[x _{K, 1}, x _{K, 2}, x _{K, i}... x _{K, N}] ^T, k=1,2, i=1,2 ... N, and utilize respectively and φ ^*Corresponding pre-coding matrix

Need interactive information after the modulation is carried out sending by user's sky alignment relay station separately after the precoding;

(6) relay station receives the signal that above-mentioned two users send, and obtains two users' multiple-input and multiple-output transmitted in both directions superposed signal y=[y ₁, y ₂..., y _N] ^T

(7) relay station according in the above-mentioned steps (3-3) with φ ^*The Frobenius norm of corresponding pre-coding matrix is carried out physical-layer network coding to the transmitted in both directions superposed signal that receives and is detected, and obtains the network code symbol

Detailed process is as follows:

(7-1) relay station obtains two users' equivalent channel gain according to the Frobenius norm calculation of the pre-coding matrix of two user feedbacks in the step (3-3)

With

(7-2) relay station utilizes above-mentioned equivalent channel gain to i superposed signal y _iCarry out Maximum Likelihood Detection, obtain i network code symbol

The detection expression formula is:

${\hat{x}}_i=\left\{\begin{array}{cc}1& e^{\left(\frac{\widetilde{\mathrm{\&Lambda;}}\left(\mathrm{1,1}\right)}{{\mathrm{\&sigma;}}_r}\right)}+e^{\left(\frac{\widetilde{\mathrm{\&Lambda;}}(-1,-1)}{{\mathrm{\&sigma;}}_r}\right)}\&GreaterEqual;e^{\left(\frac{\widetilde{\mathrm{\&Lambda;}}(-\mathrm{1,1})}{{\mathrm{\&sigma;}}_r}\right)}+e^{\left(\frac{\widetilde{\mathrm{\&Lambda;}}(1,-1)}{{\mathrm{\&sigma;}}_r}\right)}\\ -1& e^{\left(\frac{\widetilde{\mathrm{\&Lambda;}}\left(\mathrm{1,1}\right)}{{\mathrm{\&sigma;}}_r}\right)}+e^{\left(\frac{\widetilde{\mathrm{\&Lambda;}}(-1,-1)}{{\mathrm{\&sigma;}}_r}\right)}<e^{\left(\frac{\widetilde{\mathrm{\&Lambda;}}(-\mathrm{1,1})}{{\mathrm{\&sigma;}}_r}\right)}+e^{\left(\frac{\widetilde{\mathrm{\&Lambda;}}(1,-1)}{{\mathrm{\&sigma;}}_r}\right)}\end{array}\right.,$

Wherein σ _rIt is the noise variance of relay station;

(8) relay station is with above-mentioned network code symbol Send to two users, the transmission signal is E wherein _{B, r}It is the transmission energy of every antenna of relay station;

(9) two users receive the transmission signal s of relay station respectively, utilize the pre-coding matrix of above-mentioned steps (3) to make up decoding matrix, to send that signal is decoded and demodulation after, obtain respectively separately for the restituted signal that sends signal

K=1,2;

(10) two users are respectively according to the need interactive information x of above-mentioned steps (5) ₁And x ₂, restituted signal is separately deciphered, obtain the other user's data message

K=1,2, wherein ⊙ is that Hadamard is long-pending.

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