CN104022987B - Interference elimination method in MIMO alternating relay system on basis of decoding forwarding - Google Patents

Abstract

The invention discloses an interference elimination method in an MIMO alternating relay system on the basis of decoding forwarding. The method mainly solves the problem of interference among relays of the MIMO system. The method comprises the realizing steps that (1), the system is set; (2), according to the set system, vectors of mixed signals sent to the relays from source nodes at different time slots and processed through a precoding matrix are constructed; (3), the relays receive the signals sent from the source nodes and decode the signals; (4), the precoding matrix is designed; (5) target nodes receive the vectors of interference-free signals sent by the relays. According to the method, the limitation to parity of the number of antennas of the system nodes can be avoided, the system complexity is reduced, and the maximum freedom degree of the system can be achieved.

Description

MIMO replaces the interference elimination method forwarding in relay system based on decoding

Technical field

The invention belongs to communication technical field, particularly to a kind of relay well interference elimination method, can be used for multi input Multi output MIMO replaces relay system.

Background technology

Multiple-input and multiple-output mimo system can improve spectrum efficiency.Additionally, relaying auxiliary transmission is expanded the coverage area With the ability providing space diversity.Therefore, more people are attracted to enter by the hybrid system that multiple-input and multiple-output MIMO and relaying form Row in-depth study.

In the hybrid system of multiple-input and multiple-output MIMO and relaying composition, relaying is divided in full duplex relaying and half-duplex Continue.Full duplex relaying can be transmitted signal and receipt signal simultaneously, and half-duplex relay system is relaying at the same time Can only sending signal or receipt signal.Because full duplex relaying system implements relatively difficult, thus half-duplex relay obtains To broader applications.But in half-duplex relay system, in the case that signal to noise ratio is higher, the capacity loss of system is than larger. A lot of schemes are proposed the method recovering capacity loss, and in these schemes, alternately trunking plan has attracted more people to carry out Research.It can make two relayings be forwarded successively from transmitting terminal to receiving terminal.However, for alternately trunking plan, one Intrinsic shortcoming is that there is relay well interference IRI, and it reduces the performance of system to a great extent.

Relay system is replaced for multiple-input and multiple-output MIMO, it is already proposed that the scheme of interference alignment IA, that is, exists Interference signal is snapped to an interference space by signal receiving end, and so orthogonal with interference space subspace just can be used To receive useful signal.But this with based on interference alignment IA scheme deficiency be：

1. system can only obtain the degree of freedom of 3/4M, and wherein, M is the antenna number of each node and be only idol in system Number；

2. three repeaters must be configured and just can complete interference alignment IA, system setting is complicated.

Content of the invention

Present invention aims to the deficiency of above-mentioned prior art is it is proposed that a kind of MIMO replaces base in relay system The interference elimination method forwarding in decoding, is limited with the parity avoiding the node antennas number to system, reduces system complexity, Reach system maximum degree of freedom M.

Realization the technical scheme is that：Source node in MIMO alternately relay system sends mixed signal and in source Distinguish the pre-coding matrix of design level connection at node and at relaying, make relay well disturb IRI to be completely eliminated, to realize system Big degree of freedom and low-complexity.Implementation step includes as follows：

1) system setting:

If mimo system includes a source node S, destination node D and two relaying R₁、R₂, they all configure M root sky Line, M>=2, and the transmission means relaying is half-duplex；

When to make time slot be odd number, source node S and the second relaying R2 sending signal, simultaneously destination node D receive the second relaying The signal that R2 sends, the first relaying R1 receives the signal that source node S sends；

When to make time slot be even number, source node S and the first relaying R1 sending signal, simultaneously destination node D receive the first relaying The signal that R1 sends, the second relaying R2 receives the signal that source node S sends；

2) build the mixed signal vector that source node S sends in different time-gap：

2.1) in first time slot, the signal that source node S is sent is expressed as s₁：

s₁=x₁=[x₁₁, x₁₂... x_1i,…x_1M]^T,

Wherein, x_1iIt is i-th component of signal that source node S sends in first time slot, i=1,2 ... M, T representing matrix turns Put；

2.2) in second time slot, the mixed signal vector representation that source node S is sent is s₂：

s₂=A₁B₁(x₂+x₁),

Wherein, A₁B₁It is the cascade pre-coding matrix when time slot is for even number for the source node, A₁And B₁It is M × M dimension matrix, x₂ =[x₂₁,x_22,…x_2i,…x_2M]^T, x_2iIt is i-th useful signal component that source node S sends in the second time slot, i=1,2 ... M；

2.3) in the 3rd time slot, the mixed signal vector representation that source node S is sent is s₃：

s₃=A₂B₂(x₃+x₂),

Wherein, A₂B₂It is the cascade pre-coding matrix when time slot is for odd number for the source node, A₂And B₂It is M × M dimension matrix, x₃ =[x₃₁,x_32,…x_3i,…x_3M]^T, x_3iIt is i-th useful signal component that source node S sends in the 3rd time slot, i=1,2 ... M；

3) according to step 2) mixed signal vector that the source node S that builds sends, obtain the first relaying R₁When first The signal phasor y that gap receives_r1,1For：

y_r1,1=H₁x₁+n_r1,1,

Assume the first relaying R₁Can be by x₁It is correctly decoded and in the second time slot by x₁It is transmitted, i.e. the second time slot first The signal phasor s that relaying sends_r1,2It is expressed as:

s_r1,2=T₁W₁x₁,

Then the second relaying R₂The signal phasor y receiving in second time slot_r2,2For：

y_r2,2=H₂s₂+F₁s_r1,2+n_r2,2

=H₂A₁B₁x₂+(H₂A₁B₁+F₁T₁W₁)x₁+n_r2,2,

Wherein, n_r1,1It is to relay R in the first time slot first₁The additive white Gaussian noise at place, H₁It is source node S in first Continue R₁M × M dimension flat fading channel matrix, n_r2,2It is to relay R in the second time slot second₂The additive white Gaussian noise at place, H₂It is Source node S relays R to second₂M × M dimension flat fading channel matrix, F₁It is to relay R from first₁To the second relaying R₂M × M Dimension flat fading channel matrix, T₁W₁It is first relaying R₁The cascade pre-coding matrix at place, T₁And W₁It is M × M dimension matrix, H₂A₁B₁x₂It is to relay R second₂The useful signal vector at place, (H₂A₁B₁+F₁T₁W₁)x₁It is to relay R second₂The relay well at place Interference；

4) design the pre-coding matrix A when time slot is for even number for the source node₁、B₁, the first relaying R₁The pre-coding matrix at place T₁、W₁, make the second relaying R₂Relay well interference (the H at place₂A₁B₁+F₁T₁W₁)x₁It is completely eliminated；

5) according to step 4) design it is assumed that second relaying R₂Can be by x₂It is correctly decoded and in the 3rd time slot by x₂Carry out Transmission, the signal phasor s that is, the 3rd time slot the second relaying sends_r2,3It is expressed as:

s_r2,3=T₂W₂x₂,

Then the first relaying R₁The signal phasor y receiving in the 3rd time slot_r1,3For：

y_r1,3=H₁s₃+F₂s_r2,3+n_r1,3

=H₁A₂B₂x₃+(H₁A₂B₂+F₂T₂W₂)x₂+n_r1,3

Wherein, n_r1,3It is to relay R in the 3rd time slot first₁The additive white Gaussian noise at place, F₂It is to relay R from second₂To One relaying R₁M × M dimension flat fading channel matrix, T₂W₂It is the second relaying R₂The pre-coding matrix of the cascade at place, T₂And W₂All Tie up matrix, H for M × M₁A₂B₂x₃It is to relay R first₁The useful signal at place, (H₁A₂B₂+F₂T₂W₂)x₂It is to relay R first₁Place Relay well interference；

6) according to step 4) in the pre-coding matrix A when time slot is for even number for the source node₁、B₁, the first relaying R₁That locates is pre- Encoder matrix T₁、W₁Identical method for designing, designs the pre-coding matrix A when time slot is for odd number for the source node₂、B₂, the second relaying R₂The pre-coding matrix T at place₂、W₂, make the first relaying R₁Relay well interference (the H at place₁A₂B₂+F₂T₂W₂)x₂It is completely eliminated；

7) relay well disturb by step 4) and step 6) elimination after, destination node D is in the signal phasor of second time slot y_d,2With the vector y in the 3rd time slot_d,3For：

y_d,2=G₁s_r1,2+n_d,2=G₁T₁W₁x₁+n_d,2,

y_d,3=G₂s_r2,3+n_d,3=G₂T₂W₂x₂+n_d,3,

Wherein, n_d,2It is the additive white Gaussian noise at second time slot destination node D, G₁It is the first relaying R₁To purpose M × M dimension flat fading channel matrix of node D, G₁T₁W₁x₁For receiving from the first relaying R₁Non-relay interference Signal, n_d,3It is the additive white Gaussian noise at the 3rd time slot destination node D, G₂It is the second relaying R₂M to destination node D × M ties up flat fading channel matrix, G₂T₂W₂x₂Relay R for what purpose node received from second₂Non-relay interference Signal.

The present invention compared with prior art, has the advantage that：

1) improve degree of freedom.In the existing scheme based on interference alignment IA, done by interference signal is snapped to one Disturb the degree of freedom of the 3/4M that can only achieve system in subspace, the present invention passes through to pass through to design precoding at source node and relaying Matrix makes system reach maximum degree of freedom M；

2) system setting is simple.It is necessary to three repeaters of configuration just can complete in the existing scheme based on interference alignment IA Interference alignment, the present invention only need to configure two relayings and can complete interference and be completely eliminated；

3) condition restriction is little.Existing based on interference alignment IA scheme can only operate in node antennas number be even number condition Under, the present invention does not require to the parity of system node antenna number, so that the working condition of system is not limited by node antennas number System.

Brief description

The MIMO that Fig. 1 present invention uses replaces relay system schematic diagram；

Fig. 2 is the flowchart of the present invention；

Under conditions of Fig. 3 is given system total node antennas number, use the present invention and existing interference alignment IA method system respectively The degree of freedom comparison diagram that system obtains；

Under conditions of Fig. 4 is each node antennas number of given system, use the present invention and existing interference alignment IA method respectively The degree of freedom comparison diagram that system obtains.

Specific embodiment

Referring to the drawings technical scheme and effect are described in further detail.

According to Fig. 2, the present invention to realize step as follows：

Step 1. system is arranged：

With reference to Fig. 1, the mimo system of present invention setting includes a source node S, destination node D and two relayings R₁、R₂, they all configure M root antenna, M>=2, and the transmission means relaying is half-duplex；

When to make time slot be odd number, source node S and the second relaying R2 sending signal, simultaneously destination node D receive the second relaying The signal that R2 sends, the first relaying R1 receives the signal that source node S sends；

When to make time slot be even number, source node S and the first relaying R1 sending signal, simultaneously destination node D receive the first relaying The signal that R1 sends, the second relaying R2 receives the signal that source node S sends.

Step 2. builds the mixed signal vector that source node S sends in different time-gap：

2.1) in first time slot, the signal that source node S is sent is expressed as s₁：

s₁=x₁=[x₁₁, x₁₂... x_1i... x_1M]^T,

Wherein, x_1iIt is i-th component of signal that source node S sends in first time slot, i=1,2 ... M, T representing matrix turns Put；

2.2) in second time slot, the mixed signal vector representation that source node S is sent is s₂：

s₂=A₁B₁(x₂+x₁),

Wherein, A₁B₁It is the cascade pre-coding matrix when time slot is for even number for the source node, A₁And B₁It is M × M dimension matrix；x₂ =[x₂₁,x₂₂,…x_2i... x_2M]^T, x_2iIt is i-th useful signal component that source node S sends in the second time slot, i=1,2 ... M；

2.3) in the 3rd time slot, the mixed signal vector representation that source node S is sent is s₃：

s₃=A₂B₂(x₃+x₂),

Wherein, A₂B₂It is the cascade pre-coding matrix when time slot is for odd number for the source node, A₂And B₂It is M × M dimension matrix, x₃ =[x₃₁,x₃₂,…x_3i... x_3M]^T, x_3iIt is i-th useful signal component that source node S sends in the 3rd time slot, i=1,2 ... M；

The mixed signal vector that step 3. sends according to the source node S that step 2 builds, obtains the first relaying R₁At first The signal phasor y that time slot receives_r1,1For：

y_r1,1=H₁x₁+n_r1,1,

Assume the first relaying R₁Can be by x₁It is correctly decoded and in the second time slot by x₁It is transmitted, i.e. the second time slot first The signal phasor s that relaying sends_r1,2It is expressed as:

s_r1,2=T₁W₁x₁,

Then the second relaying R₂The signal phasor y receiving in second time slot_r2,2For：

y_r2,2=H₂s₂+F₁s_r1,2+n_r2,2

=H₂A₁B₁x₂+(H₂A₁B₁+F₁T₁W₁)x₁+n_r2,2,

Wherein, n_r1,1It is to relay R in the first time slot first₁The additive white Gaussian noise at place, H₁It is source node S in first Continue R₁M × M dimension flat fading channel matrix, n_r2,2It is to relay R in the second time slot second₂The additive white Gaussian noise at place, H₂It is Source node S relays R to second₂M × M dimension flat fading channel matrix, F₁It is to relay R from first₁To the second relaying R₂M × M Dimension flat fading channel matrix, T₁W₁It is first relaying R₁The cascade pre-coding matrix at place, T₁And W₁It is M × M dimension matrix, H₂A₁B₁x₂It is to relay R second₂The useful signal vector at place, (H₂A₁B₁+F₁T₁W₁)x₁It is to relay R second₂The relay well at place Interference；

Step 4. designs the pre-coding matrix A when time slot is for even number for the source node₁、B₁, the first relaying R₁The precoding square at place Battle array T₁、W₁, make the second relaying R₂Relay well interference (the H at place₂A₁B₁+F₁T₁W₁)x₁It is completely eliminated：

4.1) design matrix A₁、T₁, make H₂A₁And F₁T₁It is aligned in H₂And F₁Common factor SPACE V₁On, that is,

V₁=H₂A₁=F₁T₁,

Above formula is deformed into：

V₁-H₂A₁=0,

V₁-F₁T₁=0,

Wherein A₁Source node time slot for even number pre-coding matrix, T₁It is the first relaying R₁The pre-coding matrix at place, H₂ It is that source node S relays R to second₂M × M dimension flat fading channel matrix, F₁It is to relay R from first₁To the second relaying R₂M × M ties up flat fading channel matrix, V₁It is M × M dimension matrix；

4.2), can be obtained equal to the property of unit matrix this square formation of premultiplication according to a square formation in matrix theory：

V₁=I_MV₁, wherein I_MIt is M × M dimension unit matrix；

4.3) by 4.2) V that obtains₁=I_MV₁Substitute into 4.1) in V₁-H₂A₁=0 and V₁-F₁T₁=0, obtain following two Equation：

I_MV₁-H₂A₁=0,

I_MV₁-F₁T₁=0,

4.4) by 4.3) two equation matrixes obtaining are expressed as follows：

4.5) makeBy 4.4) in matrix equation be expressed as：

U₁X₁=0

Wherein, U₁Be 2M × 3M dimension matrix and order be 2M, X₁It is the matrix of 3M × M dimension, matrix X₁For matrix U₁Zero empty Between；

4.6) in order to eliminate interference, make the relay well distracter H at the second relaying₂A₁B₁+F₁T₁W₁Equal to zero, that is,:H₂A₁B₁ +F₁T₁W₁=0,

4.7) by 4.1) obtain etc. Formula V₁=H₂A₁=F₁T₁Be updated to 4.6) equation in, can obtain：

V₁B₁+V₁W₁=0

Wherein, W₁=α₁I_M,α₁Represent the first relaying R₁Power confinement factor,

B₁=-β₁I_M, β₁Represent the power confinement factor of source node S, I_MIt is M × M dimension unit matrix；

4.8) be make 4.7) in etc. Formula V₁B₁+V₁W₁=0 sets up it is necessary to meet B₁=-W₁：

If the β in 4.7)₁=α₁, then meet B₁=-W₁If, 4.7) in β₁≠α₁, then make W₁=γ₁I_M, B₁=- γ₁I_M, wherein, γ₁=min { α₁, β₁}.

Step 5. is according to the design of step 4 it is assumed that the second relaying R₂Can be by x₂It is correctly decoded and in the 3rd time slot by x₂Enter Row transmission, the signal phasor s that is, the 3rd time slot the second relaying sends_r2,3It is expressed as:

s_r2,3=T₂W₂x₂,

Then the first relaying R₁The signal phasor y receiving in the 3rd time slot_r1,3For：

y_r1,3=H₁s₃+F₂s_r2,3+n_r1,3

=H₁A₂B₂x₃+(H₁A₂B₂+F₂T₂W₂)x₂+n_r1,3

Wherein, n_r1,3It is to relay R in the 3rd time slot first₁The additive white Gaussian noise at place, F₂It is to relay R from second₂To One relaying R₁M × M dimension flat fading channel matrix, T₂W₂It is the second relaying R₂The pre-coding matrix of the cascade at place, T₂And W₂All Tie up matrix, H for M × M₁A₂B₂x₃It is to relay R first₁The useful signal at place, (H₁A₂B₂+F₂T₂W₂)x₂It is to relay R first₁Place Relay well interference；

Step 6. is according to the pre-coding matrix A when time slot is for even number with source node in step 4₁、B₁, the first relaying R₁Place Pre-coding matrix T₁、W₁Identical method for designing, designs the pre-coding matrix A when time slot is for odd number for the source node₂、B₂, second Relaying R₂The pre-coding matrix T at place₂、W₂, make the first relaying R₁Relay well interference (the H at place₁A₂B₂+F₂T₂W₂)x₂It is completely eliminated；

After the interference of step 7. relay well is completely eliminated by step 4 and step 6, destination node D is in the letter of second time slot Number vector y_d,2With the vector y in the 3rd time slot_d,3For：

y_d,2=G₁s_r1,2+n_d,2=G₁T₁W₁x₁+n_d,2,

y_d,3=G₂s_r2,3+n_d,3=G₂T₂W₂x₂+n_d,3,

Wherein, n_d,2It is the additive white Gaussian noise at second time slot destination node D, G₁It is the first relaying R₁To purpose M × M dimension flat fading channel matrix of node D, G₁T₁W₁x₁For receiving from the first relaying R₁Non-relay interference Signal, n_d,3It is the additive white Gaussian noise at the 3rd time slot destination node D, G₂It is the second relaying R₂M to destination node D × M ties up flat fading channel matrix, G₂T₂W₂x₂Relay R for what purpose node received from second₂Non-relay interference Signal.

Due to the first relaying R₁The pre-coding matrix T at place₁Only and source node S relays R to second₂Flat fading channel square Battle array H₂, first relaying R₁To the second relaying R₂Flat fading channel matrix F₁Relevant, and H₂、F₁With the first relaying R₁To purpose section The flat fading channel matrix G of point D₁Linear independence, so G₁T₁W₁Order be also M, second relaying R₂The pre-coding matrix T at place₂ Only and source node S relays R to second₁Flat fading channel matrix H₁, second relaying R₂To the first relaying R₁Flat fading letter Road matrix F₂Relevant, and H₁、F₂With the second relaying R₂Flat fading channel matrix G to destination node D₂Linear independence, so G₂T₂W₂Order be also M, that is, system reaches maximum degree of freedom M.

By the pre-encoder matrix of the source node of above-mentioned design and relaying, the interference of relay well is made to be completely eliminated.In order to The apparent description present invention eliminates the process of relay well interference, with table 1 data that each node sends in different time-gap to system Symbol and its pre-coding matrix are illustrated：

Data symbol and its pre-coding matrix that each node of table 1 system sends in different time-gap

Time slot

1

2

3

4

5

…

The data symbol that source node sends

x1

x2+x1

x3+x2

x4+x3

x5+x4

…

First relaying R1The data symbol sending

x1

x3

…

Second relaying R2The data symbol sending

x2

x4

…

The pre-coding matrix of source node

I

A1B1

A2B2

A1B1

A2B2

…

First relaying R1Pre-coding matrix

T1W1

T1W1

…

Second relaying R2Pre-coding matrix

T2W2

T2W2

…

The effect of the present invention can be further illustrated by following simulation result：

1. simulated conditions：Initialization system all node antennas number is respectively the antenna of 10,20,30,40,50 and each node Number is respectively 2,4,6,8,10.

2. emulation content：

The present invention and existing interference alignment IA method are when all antenna number are respectively 10,20,30,40,50 for emulation 1., The degree of freedom that system is obtained emulates, and result is as shown in Figure 3.

As can be seen from Figure 3：Under the conditions of the antenna number identical of all nodes, the degree of freedom that the present invention is reached is remote Higher than the degree of freedom being reached based on interference alignment IA method.

The present invention and existing interference alignment IA method are when each node antennas number is respectively 2,4,6,8,10 for emulation 2., The degree of freedom that system is obtained emulates, and result is as shown in Figure 4.

As can be seen from Figure 4：Under the conditions of each node antenna number identical, the degree of freedom that the present invention is reached is far above The degree of freedom being reached based on interference alignment IA method.

Claims (2)

1. a kind of MIMO replaces the interference elimination method forwarding in relay system based on decoding, comprises the steps：

1) system setting:

If mimo system includes a source node S, destination node D and two relaying R₁、R₂, they all configure M root antenna, M >=2, and the transmission means relaying is half-duplex；

When to make time slot be odd number, source node S and the second relaying R₂Sending signal, the second relaying R of destination node D reception simultaneously₂Send Signal, first relaying R₁Receive the signal that source node S sends；

When to make time slot be even number, source node S and the first relaying R₁Sending signal, the first relaying R of destination node D reception simultaneously₁Send Signal, second relaying R₂Receive the signal that source node S sends；

2) build the mixed signal vector that source node S sends in different time-gap：

2.1) in first time slot, the signal that source node S is sent is expressed as s₁：

s₁=x₁=[x₁₁, x₁₂... x_1i... x_1M]^T,

Wherein, x_1iIt is i-th component of signal that source node S sends in first time slot, i=1,2 ... M, T representing matrix transposition；

2.2) in second time slot, the mixed signal vector representation that source node S is sent is s₂：

s₂=A₁B₁(x₂+x₁),

Wherein, A₁B₁It is the cascade pre-coding matrix when time slot is for even number for the source node, A₁And B₁It is M × M dimension matrix；x₂= [x₂₁,x₂₂,…x_2i... x_2M]^T, x_2iIt is i-th useful signal component that source node S sends in the second time slot, i=1,2 ... M；

2.3) in the 3rd time slot, the mixed signal vector representation that source node S is sent is s₃：

s₃=A₂B₂(x₃+x₂),

Wherein, A₂B₂It is the cascade pre-coding matrix when time slot is for odd number for the source node, A₂And B₂It is M × M dimension matrix, x₃= [x₃₁,x₃₂,…x_3i... x_3M]^T, x_3iIt is i-th useful signal component that source node S sends in the 3rd time slot, i=1,2 ... M；

3) according to step 2) mixed signal vector that the source node S that builds sends, obtain the first relaying R₁Receive in first time slot Signal phasor y_r1,1For：

y_r1,1=H₁x₁+n_r1,1,

Assume the first relaying R₁Can be by x₁It is correctly decoded and in the second time slot by x₁It is transmitted, that is, the second time slot first relays The signal phasor s sending_r1,2It is expressed as:

s_r1,2=T₁W₁x₁,

Then the second relaying R₂The signal phasor y receiving in second time slot_r2,2For：

y_r2,2=H₂s₂+F₁s_r1,2+n_r2,2

=H₂A₁B₁x₂+(H₂A₁B₁+F₁T₁W₁)x₁+n_r2,2

Wherein, n_r1,1It is to relay R in the first time slot first₁The additive white Gaussian noise at place, H₁It is that source node S relays R to first₁'s M × M ties up flat fading channel matrix, n_r2,2It is to relay R in the second time slot second₂The additive white Gaussian noise at place, H₂It is source node S to second relays R₂M × M dimension flat fading channel matrix, F₁It is to relay R from first₁To the second relaying R₂M × M dimension flat Fading channel matrix, T₁W₁It is first relaying R₁The cascade pre-coding matrix at place, T₁And W₁It is M × M dimension matrix, H₂A₁B₁x₂ It is to relay R second₂The useful signal vector at place, (H₂A₁B₁+F₁T₁W₁)x₁It is to relay R second₂The relay well interference at place；

4) design the pre-coding matrix A when time slot is for even number for the source node₁、B₁, the first relaying R₁The pre-coding matrix T at place₁、W₁, Make the second relaying R₂Relay well interference (the H at place₂A₁B₁+F₁T₁W₁)x₁Eliminate；

5) according to step 4) design it is assumed that second relaying R₂Can be by x₂It is correctly decoded and in the 3rd time slot by x₂It is transmitted, I.e. the 3rd time slot second relays the signal phasor s sending_r2,3It is expressed as:

s_r2,3=T₂W₂x₂,

Then the first relaying R₁The signal phasor y receiving in the 3rd time slot_r1,3For：

y_r1,3=H₁s₃+F₂s_r2,3+n_r1,3

=H₁A₂B₂x₃+(H₁A₂B₂+F₂T₂W₂)x₂+n_r1,3

Wherein, n_r1,3It is to relay R in the 3rd time slot first₁The additive white Gaussian noise at place, F₂It is to relay R from second₂To in first Continue R₁M × M dimension flat fading channel matrix, T₂W₂It is the second relaying R₂The pre-coding matrix of the cascade at place, T₂And W₂Be M × M ties up matrix, H₁A₂B₂x₃It is to relay R first₁The useful signal vector at place, (H₁A₂B₂+F₂T₂W₂)x₂It is to relay R first₁Place Relay well interference；

6) according to step 4) in the pre-coding matrix A when time slot is for even number for the source node₁、B₁, the first relaying R₁The precoding at place Matrix T₁、W₁Identical method for designing, designs the pre-coding matrix A when time slot is for odd number for the source node₂、B₂, the second relaying R₂Place Pre-coding matrix T₂、W₂, make the first relaying R₁Relay well interference (the H at place₁A₂B₂+F₂T₂W₂)x₂Eliminate；

7) relay well disturb by step 4), step 6) elimination after, destination node D is in the signal phasor y of second time slot_d,2With Vector y in the 3rd time slot_d,3For：

y_d,2=G₁s_r1,2+n_d,2=G₁T₁W₁x₁+n_d,2,

y_d,3=G₂s_r2,3+n_d,3=G₂T₂W₂x₂+n_d,3,

Wherein, n_d,2It is the additive white Gaussian noise at second time slot destination node D, G₁It is the first relaying R₁To destination node M × M dimension flat fading channel matrix of D, G₁T₁W₁x₁For receiving from the first relaying R₁Non-relay interference signal, n_d,3It is the additive white Gaussian noise at the 3rd time slot destination node D, G₂It is the second relaying R₂M × M dimension to destination node D Flat fading channel matrix, G₂T₂W₂x₂Relay R for what purpose node received from second₂Non-relay interference signal.

2. method according to claim 1, wherein step 4) in design pre-coding matrix, comprise the steps to carry out：

4a) design matrix A₁、T₁, make H₂A₁And F₁T₁It is aligned in H₂And F₁Common factor SPACE V₁On, that is,

V₁=H₂A₁=F₁T₁,

Above formula is deformed into：

V₁-H₂A₁=0,

V₁-F₁T₁=0,

Wherein A₁Source node time slot for even number pre-coding matrix, T₁It is the first relaying R₁The pre-coding matrix at place, H₂It is source Node S to second relays R₂M × M dimension flat fading channel matrix, F₁It is to relay R from first₁To the second relaying R₂M × M dimension Flat fading channel matrix, V₁It is M × M dimension matrix；

4b), can be obtained equal to the property of unit matrix this square formation of premultiplication according to a square formation in matrix theory：

V₁=I_MV₁, wherein I_MIt is M × M dimension unit matrix；

4c) by 4b) V that obtains₁=I_MV₁Substitute into 4a) in V₁-H₂A₁=0 and V₁-F₁T₁=0, obtain following two equations：

I_MV₁-H₂A₁=0,

I_MV₁-F₁T₁=0,

4d) by 4c) two equation matrixes obtaining are expressed as follows：

$\left[\begin{array}{ccc}{I}_M& -H_2& 0\\ I_M& 0& -F_1\end{array}\right]\left[\begin{array}{c}{V}_1\\ A_1\\ T_1\end{array}\right]=0,$

4e) makeBy 4d) in matrix equation be expressed as：

U₁X₁=0

Wherein, U₁Be 2M × 3M dimension matrix and order be 2M, X₁It is the matrix of 3M × M dimension, matrix X₁For matrix U₁Kernel；

4f) in order to eliminate interference, make the relay well distracter H at the second relaying₂A₁B₁+F₁T₁W₁Equal to zero, that is,:H₂A₁B₁+ F₁T₁W₁=0,

4g) by 4a) obtain etc. Formula V₁=H₂A₁=F₁T₁Be updated to 4f) equation in, can obtain：

V₁B₁+V₁W₁=0

Wherein, W₁=α₁I_M,α₁Represent the first relaying R₁Power confinement factor,

B₁=-β₁I_M, β₁Represent the power confinement factor of source node S, I_MIt is M × M dimension unit matrix；

4h) be make 4g) in etc. Formula V₁B₁+V₁W₁=0 sets up it is necessary to meet B₁=-W₁：

If the β in 4g)₁=α₁, then meet B₁=-W₁If, 4g) in β₁≠α₁, then make W₁=γ₁I_M, B₁=-γ₁I_M, its In, γ₁=min { α₁, β₁}.