CN103929385B - Interference suppression method based on signal subspace alignment for multi-source heterogeneous signals - Google Patents

Abstract

The invention relates to an interference suppression method based on signal subspace alignment for multi-source heterogeneous signals. The interference suppression method based on the signal subspace alignment for the multi-source heterogeneous signals comprises the steps that the precoding vectors of private signals and public signals in the heterogeneous signals sent by each communication node are determined respectively; each communication nodes sends three paths of private signals and three paths of public signals according to the corresponding determined precoding vectors in the multiple access stage; a relay node receives and decodes the mixed heterogeneous signals sent by all the communication nodes, and a coding estimated value generated after subspace alignment is obtained; the relay node sends broadcast signals after conducting physical-layer network coding on the coding estimated value and conducting weighting on a precoding transmission vector; the communication nodes conduct interference suppression on the received broadcast signals by means of the received precoding vectors, network codes of equivalent received signals of the communication nodes with interference signals eliminated are decoded, and then an estimated value of a signal expected to be received is obtained. By the adoption of the interference suppression method based on the signal subspace alignment for the multi-source heterogeneous signals, interference between the private signals and the public signals of multiple communication users can be eliminated, and the interference suppression complexity can also be lowered.

Description

Multi-source heterogeneous signal interference suppression method based on signal subspace alignment

Technical Field

The invention relates to the field of multi-user relay cooperative transmission, in particular to a multi-source heterogeneous signal interference suppression method based on signal subspace alignment.

Background

A Two-way Relay Network (TWR) technology represented by Physical-layer Network Coding (PNC) is one of the technologies that have the potential to improve the spectrum efficiency of a Relay Network. Currently, research schemes combining PNC and Multiple-Input Multiple-Output (MIMO) technology are emerging, and an important research direction in these schemes is to "reform" a MIMO-based wireless bidirectional relay channel (TWRC) at a source node by using a precoding technology so that bidirectional signals can have the same channel gain and phase in the relay. After the signals are aligned, the relay only needs to detect the superposed signals of the bidirectional signals, and does not need to detect the individual information of two superposed components respectively, so that the number of independent streams received by the relay is reduced, the complexity of signal processing at the relay end is simplified, and the research of MIMO multi-directional relay channels based on PNC is not in the way.

In recent years, an Interference Alignment concept (IA) has been introduced into the research of MIMO multi-directional relay channels based on PNC, and a "signal space Alignment" (SSA) theory for network coding has been deduced. The SSA theory does not "blindly" directly suppress interference, but "intelligently" utilizes interference to form meaningful information flow, and achieves the effect of interference suppression through a joint signal processing algorithm of a source node and a relay node (or called a relay station).

The invention patent of China applied to the university of electronic technology of Western 'common-channel multi-user interference suppression method based on signal space alignment' (patent number CN201110066539.3, granted announcement date: 2013, 26.06.3) mainly provides a multidirectional relay information transmission method based on MIMO Y channels, and the method comprises the following steps: each communication node (or called communication user or user node) sends vector weighted independent information to other communication nodes through the relay station; the relay station receives the superposed signals after signal space alignment; the relay station carries out network coding on the information after the communication users are aligned and broadcasts and sends the information to the user nodes; each user node suppresses the received interference signal and acquires the desired signal using the null space principle.

The co-channel multi-user interference suppression method disclosed in chinese patent CN201110066539.3 can be well performed under the condition of a small number of communication users, but the method still has some disadvantages: when the number of communication users increases, in order to reduce the constraint of the number of communication users and relay station antennas and eliminate the interference of signals among multiple users to ensure that the null space suppression method can be successfully realized during interference suppression, an antenna selection algorithm must be used, which undoubtedly increases the calculation complexity and the interference suppression complexity.

Disclosure of Invention

The technical problem to be solved by the present invention is to provide a multi-source heterogeneous signal interference suppression method based on signal subspace alignment, which can eliminate the interference between the private signals and the public signals of a plurality of communication users and can reduce the interference suppression complexity, aiming at the above prior art.

The technical scheme adopted by the invention for solving the technical problems is as follows: a multi-source heterogeneous signal interference suppression method based on signal subspace alignment is characterized by comprising the following steps:

(1) respectively determining the precoding vector of the private signal and the precoding vector of the public signal in the heterogeneous signals sent by each communication node:

(1-1) four communication nodes and a relay node are arranged, each communication node sends three paths of independent private signals to other communication nodes, the first communication node and the fourth communication node send a path of public signals, the second communication node and the third communication node send two paths of same public signals, and heterogeneous signals sent by a certain communication node are formed by mixing the private signals and the public signals sent by the communication node; respectively determining a private signal combination of which the private signals need to be spatially aligned and a public signal combination of which the public signals need to be spatially aligned according to whether the heterogeneous signals need to be network-encoded in the relay node;

(1-2) determining a precoding vector which can align a pair of private signals of a desired combination in the private signals to the same signal subspace according to formula (1) and determining a precoding vector which can align a pair of common signals of the desired combination in the common signals to the same signal subspace according to formula (2) by using the principle of intersecting subspaces:

wherein, the private signal sent by the ith communication node to the jth communication node and the private signal sent by the jth communication node to the ith communication node are called a pair of private signals expected to be combined, the pair of private signals expected to be combined is called a private signal combination, the second path of public signal sent by the ith communication node and the first path of public signal sent by the (i + 1) th communication node are called a pair of public signals expected to be combined, the pair of public signals expected to be combined is called a public signal combination, H^[R,i]Representing the channel transmission matrix from the ith communication node to the relay node R, H^[R,j]Representing the channel transmission matrix from the jth communication node to the relay node R,a precoding vector representing the need for a private signal from the ith communication node to the jth communication node,a precoding vector representing the need for a private signal from the jth communication node to the ith communication node,a precoding vector required by a second path of common signals transmitted by the ith communication node is represented,representing the precoding vector required by the first public signal sent by the (i + 1) th communication node, and span (X) representing anyThe space spanned by the column vectors of matrix X;

(2) in the first time slot-multiple access stage, each communication node simultaneously sends three private signals and a public signal by using the pre-coding vector of the private signal and the pre-coding vector of the public signal determined in the step (1-2), the relay node receives a mixed heterogeneous signal sent to the relay node by each communication node, the mixed heterogeneous signal is a signal obtained by pre-coding the heterogeneous signal of each communication node and then mixing and adding noise, and the relay node receives a mixed heterogeneous signal y sent to the relay node by each communication node^[R]Comprises the following steps:

wherein H^[R,i]Representing the channel transmission matrix from the ith communication node to the relay node R,a precoding vector representing the need for a private signal from the ith communication node to the jth communication node,representing a private signal sent by the ith communication node to the jth communication node,representing a common signal transmitted by the ith communication node,a precoding vector required by the first common signal sent by the ith communication node is represented,a precoding vector required for a second common signal sent by the ith communication node is represented, andm represents the number of communication node antennas, n^[R]A noise vector representing the relay node R;

(3) converting a receiving transmission channel of the relay node into an equivalent independent channel, decoding the mixed heterogeneous signal received in the step (2), and obtaining a decoding estimation value after the mixed heterogeneous signal subspace is aligned:

(3-1) respectively obtaining a subspace alignment equation of the private signal and a subspace alignment equation of the public signal according to the network coding signal subspace alignment condition:

the subspace alignment equation for the private signal is:

the subspace alignment equation for the common signal is:

wherein H^[R,i]Representing the channel transmission matrix from the ith communication node to the relay node R,a precoding vector, H, representing the need for a private signal from the ith communication node to the jth communication node^[R,j]Representing the channel transmission matrix from the jth communication node to the relay node R,a precoding vector representing the need for a private signal from the jth communication node to the ith communication node,equivalent transmission message for expressing private information between ith communication node and jth communication nodeLane, π (i, j) denotes sequentially increasing numbers,indicating the precoding vector, H, required by the second path of common signal sent by the ith communication node^[R,i+1]Represents the channel transmission matrix from the i +1 th communication node to the relay node R,represents the precoding vector needed by the first path of common signal sent by the (i + 1) th communication node,an equivalent transmission channel for representing common information between the ith communication node and the (i + 1) th communication node;

(3-2) the relay node performs signal transformation on the mixed heterogeneous signal received in the step (2), and obtains a decoding estimation value after the subspace alignment of the mixed heterogeneous signal according to a subspace alignment equation of the private signal and a subspace alignment equation of the public signal:

wherein, U_pRepresenting the private signal equivalent channel transmission matrix sent by all communication nodes,U_crepresenting the common signal equivalent channel transmission matrix transmitted by all communication nodes,U_pand U_cAre all non-singular arrays;andrespectively obtained from the subspace alignment equation of the private signal and the subspace alignment equation of the public signal in the step (3-1),representing a private signal sent by the ith communication node to the jth communication node,representing a common signal transmitted by the i-th communication node, n^[R]A noise vector representing the relay node R;whereinThe equivalent private signals after the 12 private signals sent by the 4 communication nodes are subjected to signal subspace alignment are represented,m is any natural number from 1 to 6;the equivalent common signal after the 6 common signals sent by the 4 communication nodes are subjected to signal subspace alignment is shown,n ∈ {1,2,3}, the relay node R respectively obtains decoding estimated values by using a zero forcing decoding algorithm:

(4) and (3) carrying out physical layer network coding on the decoding estimation value obtained in the step (3-2) by the relay node to obtain a network coding signal, and carrying out broadcast transmission after carrying out precoding transmission vector weighting on the network coding signal in a second time slot-broadcast transmission stage:

(4-1) the relay node performs physical layer network coding modulation on the decoding estimation value obtained in the step (3-2) to obtain a network coding signal:wherein Represents a private signal in the network coded signal,represents the common signal in the network coded signal,represents an exclusive or operation;

(4-2) the relay node aligns the user signal directions receiving the same network coding signal to the same signal subspace by using the intersecting subspace principle, determines a precoding vector which can align the private signal direction in the network coding signal to the same signal subspace according to the formula (3), and determines a precoding vector which can align the public signal direction in the network coding signal to the same signal subspace according to the formula (4):

wherein H^[i,R]Representing the channel transmission matrix from the relay node R to the i-th communication node, H^[j,R]Representing relay nodes R to jth communication nodeThe channel transmission matrix of a point is,indicating that the ith communication node receives the precoding vectors required by the private signals in the network coding signals of the communication node i and the communication node j,indicating that the jth communication node receives precoding vectors required by private signals in the network coding signals of the communication node i and the communication node j,indicating that the ith communication node receives a precoding vector required by a common signal in the network coded signals of the communication node i and the communication node j,representing a precoding vector required by a j-th communication node for receiving a common signal in network coding signals of a communication node i and a communication node j, and span (X) representing a space formed by column vectors of an arbitrary matrix X;

(4-3) respectively obtaining a subspace alignment equation of a private signal in the network coding signal and a subspace alignment equation of a public signal in the network coding signal according to the subspace alignment condition of the network coding signal:

the subspace alignment equation for the private signal in the network coded signal is:

the subspace alignment equation for the common signal in the network coded signal is:

wherein,an equivalent transmission channel representing a private signal between the ith communication node and the jth communication node,an equivalent transmission channel for common signals between the ith communication node and the jth communication node, wherein π p (i, j) and π c (i, j) respectively represent sequentially increasing numbers according toAndconstructing a receive precoding matrix for an ith communication nodeI.e. all communication nodes are as follows:

(4-4) obtaining equivalent channels by utilizing subspace alignment:

removing private signal equivalent channel vectors from equivalent channelsThe equivalent channel obtained isFromMedium erasure common signal equivalent channel vectorAndthe equivalent channel obtained is

(4-5) respectively acquiring the precoded transmission vector of the private signal and the precoded transmission vector of the public signal through the following formulas:

precoded transmission vector of private signal:

precoding transmission vector of common signal:

wherein, null (X) tableShowing the null space of an arbitrary matrix X,a precoded transmission vector representing the private signal in the pi p (i, j) th network coding combination,a precoded transmit vector representing the common signal in the π c (i, j) th and π c (m, n) th network coding combinations;

(4-6), in the second time slot, namely the broadcast transmission phase, the relay node transmits the broadcast signal to the communication node:

wherein, the relay node R sends the broadcast signal of Andrespectively, the precoded transmission vectors of the private signals and the precoded transmission vectors of the public signals determined in step (4-5),the mth transmission signal representing the relay node R network-encoded private signal,the nth transmission signal represents the relay node R after network coding the public signal;

(5) and the communication node receives the broadcast signals sent by the relay node, and performs interference suppression on the broadcast signals broadcast and sent by the relay node by using the precoding transmitting vector and the precoding receiving vector:

(5-1) making the communication node receive the precoded transmission vector of the private signal obtained in the step (4-5)Jamming private signalsThe equivalent transmission channel of (a) satisfies:

transforming the interference signal in the broadcast signal into the null space of the desired private signal space in the broadcast signal to eliminate the interference signal in the signal received by the communication node, wherein H^[i,R]Representing the channel transmission matrix of the relay node R to the ith communication node,precoding a transmission vector for the private signal determined in step (4-5);

precoding a transmitting vector by using the common signal obtained in the step (4-5) to enable the received interference common signalThe equivalent transmission channel of (a) satisfies:

transforming the interference signal in the broadcast signal into the null space of the desired common signal space in the broadcast signal to eliminate the interference signal in the signal received by the communication node, wherein H^[i,R]Representing the channel transmission matrix of the relay node R to the ith communication node,precoding a transmission vector for the common signal determined in step (4-5);

(5-2) the equivalent received signal of the ith communication node obtained after the interference signal is eliminated is:

wherein,is the received precoding matrix, H, of the communication node i^[i,R]Representing the channel transmission matrix of the relay node R to the ith communication node,andrespectively, the precoded transmission vectors of the private signals and the precoded transmission vectors of the public signals determined in step (4-5),the mth transmission signal representing the relay node R network-encoded private signal,represents the nth transmission signal after the relay node R network-encodes the common signal,indicating the expected received signal of the communication node i,a noise vector representing the communication node i,is a reception equivalent transmission matrix of the ith communication node and is a diagonal matrix;

(6) and decoding the equivalent received signal of a certain communication node from which the interference signal is eliminated by network coding to obtain an estimated value of the mixed heterogeneous signal expected to be received by the communication node:

(6-1), reception equivalent transmission matrix of ith communication nodeThe method comprises the steps that a diagonal matrix is used, and a zero forcing decoding algorithm is used for obtaining a decoding signal of the ith communication node;

(6-2) performing network coding decoding operation by using the signal sent by the ith communication node and the decoded signal in the step (6-1) to obtain an estimated value of the private signal and an estimated value of the public signal expected to be received by the ith communication node, wherein the formulas of the estimated values of the private signal and the public signal are as follows:

wherein,an estimated value of a private signal sent by the jth communication node to the ith communication node, an estimated value of a public signal expected to be received by the ith communication node comprises estimated values of public signals sent by the other three communication nodes, andan estimated value of a common signal sent by a jth communication node, wherein the jth communication node is one of three other communication nodes except the ith communication node, and i is not equal to j;representing a private signal sent by the ith communication node to the jth communication node,representing a private signal sent by the jth communication node to the ith communication node,representing a common signal transmitted by the ith communication node,representing the common signal transmitted by the jth communication node.

Further, the physical layer network coding in step (4) includes the following steps: first, for private signalsAnd private signalsPerforming exclusive-or operation to obtain a private signal in the network coding signalSecondly, for common signalsAnd a common signalPerforming exclusive-or operation to obtain common signal in network coding signalWherein,representing a private signal sent by the jth communication node to the ith communication node,representing a private signal sent by the ith communication node to the jth communication node,representing a common signal transmitted by the ith communication node,indicating a common signal transmitted by the jth communication node, i ≠ j.

Compared with the prior art, the invention has the advantages that: on one hand, the cooperative transmission based on signal subspace alignment-physical layer network coding is adopted, so that the capability of the communication node for simultaneously sending the private signal and the public signal is realized; on the other hand, compared with the prior art, because the signal subspace alignment technology is simultaneously used in the multiple access phase and the broadcast transmission phase, when the communication node transmits the same number of independent signals, the requirement on the number configuration of the communication node and the relay node antennas is reduced. In addition, the invention can be directly popularized to any user condition without additionally adding other special processing mechanisms, thereby reducing the realization complexity.

Drawings

Fig. 1 is a schematic diagram of a relay channel model for cooperative transmission of multi-source heterogeneous signals in an embodiment of the present invention;

FIG. 2 is a flowchart illustrating an implementation of a multi-source heterogeneous signal interference suppression method according to an embodiment of the present invention;

fig. 3 is a schematic diagram of multi-source heterogeneous signal precoding transmission in fig. 2.

Detailed Description

The invention is described in further detail below with reference to the accompanying examples.

As shown in fig. 1, the multi-source heterogeneous signal cooperative transmission relay channel model in the embodiment of the present invention includes a communication node 1, a communication node 2, a communication node 3, a communication node 4, and a relay node R, where the communication node 1 to the communication node 4 respectively have M antennas, and the relay node R has N antennas; the multi-source heterogeneous signal cooperative transmission process comprises a first time slot-multiple access stage and a second time slot-broadcast sending stage.

As shown in fig. 2 and fig. 3, the multi-source heterogeneous signal interference suppression method based on signal subspace alignment in the embodiment of the present invention includes the following steps:

(1) respectively determining the precoding vector of the private signal and the precoding vector of the public signal in the heterogeneous signals sent by each communication node:

(1-1), the communication node 1 to the communication node 4 respectively send three independent private signals to the other three communication nodes, for example, the communication node 1 respectively sends three independent private signals to the communication node 2, the communication node 3 and the communication node 4, similarly, the communication node 2 respectively sends three independent private signals to the communication node 1, the communication node 3 and the communication node 4, and the communication node 3 and the communication node 4 are analogized in sequence; the communication node 1 and the communication node 4 send a public signal, the communication node 2 and the communication node 3 send two identical public signals, wherein a heterogeneous signal sent by a certain communication node i is a three-way independent private signal sent by the communication node iAnd a common signalMixing to form a mixture; respectively determining a private signal combination of which the private signals need to be spatially aligned and a public signal combination of which the public signals need to be spatially aligned according to whether the heterogeneous signals need to be network-encoded in the relay node R;

(1-2) determining a precoding vector which can align a pair of private signals of a desired combination in the private signals to the same signal subspace according to formula (1) and determining a precoding vector which can align a pair of common signals of the desired combination in the common signals to the same signal subspace according to formula (2) by using the principle of intersecting subspaces:

wherein, the private signal sent by the ith communication node to the jth communication node and the private signal sent by the jth communication node to the ith communication node are called a pair of private signals expected to be combined, for example, the private signal sent by the communication node 1 to the communication node 2And a private signal from the communication node 2 to the communication node 1A pair of private signals of a desired combination; a pair of private signals of the desired combination is called a private signal combination; the second path of common signals sent by the ith communication node and the first path of common signals sent by the (i + 1) th communication node are called a pair of expected combined common signals, and the pair of expected combined common signals are called a common signal combination; for example, the second common signal sent by the communication node 1 and the first common signal sent by the communication node 2 are referred to as a pair of common signals to be combined; h^[R,i]Representing the channel transmission matrix from the ith communication node to the relay node R, H^[R,j]Representing the channel transmission matrix from the jth communication node to the relay node R,a precoding vector representing the need for a private signal from the ith communication node to the jth communication node,a precoding vector representing the need for a private signal from the jth communication node to the ith communication node,a precoding vector required by a second path of common signals transmitted by the ith communication node is represented,representing a precoding vector required by a first path of public signal sent by the (i + 1) th communication node, and span (X) representing a space formed by column vectors of any matrix X;

(2) the communication node i utilizes the precoding vector of the private signal determined in the step (1-2) in the first time slot-multiple access stageAnd precoding vector of common signalThree paths of private signals and public signals are sent simultaneously, the relay node R receives the mixed heterogeneous signal sent by each communication node i (i ∈ {1,2, 3}) to the relay node as y^[R]：

Wherein H^[R,i]Representing the channel transmission matrix from the ith communication node to the relay node R,a precoding vector representing the need for a private signal from the ith communication node to the jth communication node,representing a private signal sent by the ith communication node to the jth communication node,representing a common signal transmitted by the ith communication node,a precoding vector required by the first common signal sent by the ith communication node is represented,a precoding vector required for a second common signal sent by the ith communication node is represented, andn^[R]a noise vector representing the relay node R;

(3) converting the receiving transmission channel of the relay node R into an equivalent independent channel, and carrying out the step (2) on the received mixed heterogeneous signal y^[R]Decoding to obtain mixed heterogeneous signal y^[R]Estimation of decoding after subspace alignment:

(3-1) respectively obtaining a subspace alignment equation of the private signal and a subspace alignment equation of the public signal according to the network coding signal subspace alignment condition:

the subspace alignment equation for the private signal is:

the subspace alignment equation for the common signal is:

wherein H^[R,i]Representing the channel transmission matrix from the ith communication node to the relay node R,a precoding vector, H, representing the need for a private signal from the ith communication node to the jth communication node^[R,j]Indicating channel transmission from jth communication node to relay node RThe matrix is a matrix of a plurality of matrices,a precoding vector representing the need for a private signal from the jth communication node to the ith communication node,an equivalent transmission channel for private information between the ith communication node and the jth communication node, pi (i, j) represents a sequentially increasing number,indicating the precoding vector, H, required by the second path of common signal sent by the ith communication node^[R,i+1]Represents the channel transmission matrix from the i +1 th communication node to the relay node R,represents the precoding vector needed by the first path of common signal sent by the (i + 1) th communication node,an equivalent transmission channel for representing common information between the ith communication node and the (i + 1) th communication node;

(3-2) the relay node R receives the mixed heterogeneous signal y^[R]Performing signal transformation and aligning equation according to subspace of private signalSubspace alignment equation with common signalObtaining a decoding estimation value after hybrid heterogeneous signal subspace alignment:

wherein, U_pRepresenting the private signal equivalent channel transmission matrix sent by all communication nodes,U_crepresenting the common signal equivalent channel transmission matrix transmitted by all communication nodes,U_pand U_cAre all non-singular arrays;andrespectively obtained from the subspace alignment equation of the private signal and the subspace alignment equation of the public signal in the step (3-1),representing a private signal sent by the ith communication node to the jth communication node,representing a common signal transmitted by the i-th communication node, n^[R]A noise vector representing the relay node R;whereinThe equivalent private signals after the 12 private signals sent by the 4 communication nodes are subjected to signal subspace alignment are represented,m is any natural number from 1 to 6;the equivalent common signal after the 6 common signals sent by the 4 communication nodes are subjected to signal subspace alignment is shown,n ∈ {1,2,3}, the relay node R respectively obtains decoding estimated values by using a zero forcing decoding algorithm:

(4) and (3) the relay node R performs physical layer network coding on the decoding estimation value obtained in the step (3-2) to obtain a network coding signal, and performs broadcast transmission after performing precoding transmission vector weighting on the network coding signal in a second time slot-broadcast transmission stage:

(4-1) the relay node R carries out decoding estimation value obtained in the step (3-2) And carrying out physical layer network coding modulation, wherein the physical layer network coding modulation process comprises the following steps:

first, for private signalsAnd private signalsPerforming exclusive-or operation to obtain a private signal in the network coding signalSecondly, for common signalsAnd a common signalPerforming exclusive-or operation to obtain common signal in network coding signalWherein,representing a private signal sent by the jth communication node to the ith communication node,representing a private signal sent by the ith communication node to the jth communication node,representing a common signal transmitted by the ith communication node,indicating a common signal transmitted by the jth communication node, i ≠ j.

Obtaining a network coding signal by carrying out physical layer network coding modulation on the decoding estimated value obtained in the step (3-2)Wherein, represents a private signal in the network coded signal,represents the common signal in the network coded signal,represents an exclusive or operation;

(4-2), the relay node R aligns the user signal directions receiving the same network coding signal to the same signal subspace by using the intersecting subspace principle, determines a precoding vector which can align the private signal direction in the network coding signal to the same signal subspace according to the formula (3), and determines a precoding vector which can align the public signal direction in the network coding signal to the same signal subspace according to the formula (4):

wherein H^[i,R]Representing the channel transmission matrix from the relay node R to the i-th communication node, H^[j,R]Representing the channel transmission matrix of the relay node R to the jth communication node,indicating that the ith communication node receives the precoding vectors required by the private signals in the network coding signals of the communication node i and the communication node j,indicating that the jth communication node receives precoding vectors required by private signals in the network coding signals of the communication node i and the communication node j,indicating that the ith communication node receives a precoding vector required by a common signal in the network coded signals of the communication node i and the communication node j,representing a precoding vector required by a j-th communication node for receiving a common signal in network coding signals of a communication node i and a communication node j, and span (X) representing a space formed by column vectors of an arbitrary matrix X;

(4-3) respectively obtaining a subspace alignment equation of a private signal in the network coding signal and a subspace alignment equation of a public signal in the network coding signal according to the subspace alignment condition of the network coding signal:

the subspace alignment equation for the private signal in the network coded signal is:

the subspace alignment equation for the common signal in the network coded signal is:

wherein,an equivalent transmission channel representing a private signal between the ith communication node and the jth communication node,an equivalent transmission channel for common signals between the ith communication node and the jth communication node, wherein π p (i, j) and π c (i, j) respectively represent sequentially increasing numbers according toAndconstructing a receive precoding matrix for an ith communication nodeThat is, the case of the reception precoding matrix of the communication node 1, the communication node 2, the communication node 3, and the communication node 4 is as follows:

(4-4) obtaining equivalent channels by utilizing subspace alignment:

removing the private signal equivalent channel vector from the equivalent channel ZThe equivalent channel obtained isFromMedium erasure common signal equivalent channel vectorAndthe equivalent channel obtained is

(4-5) respectively acquiring the precoded transmission vector of the private signal and the precoded transmission vector of the public signal through the following formulas:

precoded transmission vector of private signal:

precoding transmission vector of common signal:

where null (X) denotes the null space of an arbitrary matrix X,a precoded transmission vector representing the private signal in the pi p (i, j) th network coding combination,a precoded transmit vector representing the common signal in the π c (i, j) th and π c (m, n) th network coding combinations;

(4-6), in the second time slot, the broadcast transmission phase, the relay node R transmits the broadcast signal to the correspondent node:

wherein, the relay node R sends the broadcast signal of Andrespectively, the precoded transmission vectors of the private signals and the precoded transmission vectors of the public signals determined in step (4-5),the mth transmission signal representing the relay node R network-encoded private signal,the nth transmission signal represents the relay node R after network coding the public signal;

(5) the communication node receives the broadcast signal sent by the relay node RAnd utilizing the precoding transmitting vector and the precoding receiving vector to carry out interference suppression on the broadcast signal broadcast and sent by the relay node R:

(5-1) precoding transmission vectors by using the private signals obtained in the step (4-5)Interfering private signal for reception by a communication nodeThe equivalent transmission channel of (a) satisfies:

transforming the interference signal in the broadcast signal into the null space of the desired private signal space in the broadcast signal to eliminate the interference signal in the signal received by the communication node, wherein H^[i,R]Representing a channel transmission matrix from the relay node R to the ith communication node;

utilizing the public obtained in step (4-5)Signal precoding transmit vectorMaking the received interfering common signalThe equivalent transmission channel of (a) satisfies:

transforming the interference signal in the broadcast signal into the null space of the desired common signal space in the broadcast signal to eliminate the interference signal in the signal received by the communication node, wherein H^[i,R]Representing a channel transmission matrix from the relay node R to the ith communication node;

(5-2) obtaining an equivalent received signal of the ith communication node after eliminating the interference signalComprises the following steps:

wherein,is the received precoding matrix, H, of the communication node i^[i,R]Representing the channel transmission matrix of the relay node R to the ith communication node,andrespectively, the precoded transmission vectors of the private signals and the precoded transmission vectors of the public signals determined in step (4-5),the mth transmission signal representing the relay node R network-encoded private signal,represents the nth transmission signal after the relay node R network-encodes the common signal,indicating the expected received signal of the communication node i,a noise vector representing the communication node i,is a reception equivalent transmission matrix of the ith communication node and is a diagonal matrix;

(6) an equivalent received signal to a certain communication node i from which the interference signal has been removedDecoding the network code to obtain an estimated value of a mixed heterogeneous signal expected to be received by the communication node i:

(6-1), reception equivalent transmission matrix of ith communication nodeThe method comprises the steps that a diagonal matrix is used, and a zero forcing decoding algorithm is used for obtaining a decoding signal of the ith communication node;

(6-2) carrying out decoding operation of network coding by using the signal sent by the ith communication node and the decoded signal in the step (6-1) to obtain an estimated value of the private signal expected to be received by the ith communication nodeAnd an estimated value of the common signalWherein:

wherein,an estimated value of a private signal sent by the jth communication node to the ith communication node, an estimated value of a public signal expected to be received by the ith communication node comprises estimated values of public signals sent by the other three communication nodes, andan estimated value representing a common signal transmitted by a jth communication node, wherein the jth communication node is one of three other communication nodes except the ith communication node;representing a private signal sent by the ith communication node to the jth communication node,representing a private signal sent by the jth communication node to the ith communication node,representing a common signal transmitted by the ith communication node,representing the common signal transmitted by the jth communication node.

Claims (2)

1. A multi-source heterogeneous signal interference suppression method based on signal subspace alignment is characterized by comprising the following steps:

(1) respectively determining the precoding vector of the private signal and the precoding vector of the public signal in the heterogeneous signals sent by each communication node:

(1-1) four communication nodes and a relay node are arranged, each communication node sends three paths of independent private signals to other communication nodes, the first communication node and the fourth communication node send a path of public signals, the second communication node and the third communication node send two paths of same public signals, and heterogeneous signals sent by a certain communication node are formed by mixing the private signals and the public signals sent by the communication node; respectively determining a private signal combination of which the private signals need to be spatially aligned and a public signal combination of which the public signals need to be spatially aligned according to whether the heterogeneous signals need to be network-encoded in the relay node;

(1-2) determining a precoding vector which can align a pair of private signals of a desired combination in the private signals to the same signal subspace according to formula (1) and determining a precoding vector which can align a pair of common signals of the desired combination in the common signals to the same signal subspace according to formula (2) by using the principle of intersecting subspaces:

wherein, the private signal sent by the ith communication node to the jth communication node and the private signal sent by the jth communication node to the ith communication node are called a pair of private signals expected to be combined, the pair of private signals expected to be combined is called a private signal combination, the second path of public signal sent by the ith communication node and the first path of public signal sent by the (i + 1) th communication node are called a pair of public signals expected to be combined, the pair of public signals expected to be combined is called a public signal combination, H^[R,i]Representing the channel transmission matrix from the ith communication node to the relay node R, H^[R,j]Representing the channel transmission matrix from the jth communication node to the relay node R,a precoding vector representing the need for a private signal from the ith communication node to the jth communication node,a precoding vector representing the need for a private signal from the jth communication node to the ith communication node,a precoding vector required by a second path of common signals transmitted by the ith communication node is represented,representing a precoding vector required by a first path of public signal sent by the (i + 1) th communication node, and span (X) representing a space formed by column vectors of any matrix X;

(2) in the first time slot-multiple access stage, each communication node simultaneously sends three private signals and a public signal by using the pre-coding vector of the private signal and the pre-coding vector of the public signal determined in the step (1-2), the relay node receives a mixed heterogeneous signal sent to the relay node by each communication node, the mixed heterogeneous signal is a signal obtained by pre-coding the heterogeneous signal of each communication node and then mixing and adding noise, and the relay node receives a mixed heterogeneous signal y sent to the relay node by each communication node^[R]Comprises the following steps:

$y^{\[R\]}=\underset{i=1}{\overset{4}{\Σ}}{H}^{\[R,i\]}(\underset{j\≠i}{\Σ}{v}_p^{\[j,i\]}{s}_p^{\[j,i\]}+\underset{t=1}{\overset{2}{\Σ}}{v}_{c,t}^{\[i\]}{s}_c^{\[i\]})+n^{\[R\]}$

wherein H^[R,i]Representing the channel transmission matrix from the ith communication node to the relay node R,a precoding vector representing the need for a private signal from the ith communication node to the jth communication node,representing a private signal sent by the ith communication node to the jth communication node,representing a common signal transmitted by the ith communication node,a precoding vector required by the first common signal sent by the ith communication node is represented,a precoding vector required for a second common signal sent by the ith communication node is represented, andm represents the number of communication node antennas, n^[R]A noise vector representing the relay node R;

(3) converting a receiving transmission channel of the relay node into an equivalent independent channel, decoding the mixed heterogeneous signal received in the step (2), and obtaining a decoding estimation value after the mixed heterogeneous signal subspace is aligned:

(3-1) respectively obtaining a subspace alignment equation of the private signal and a subspace alignment equation of the public signal according to the network coding signal subspace alignment condition:

the subspace alignment equation for the private signal is:

the subspace alignment equation for the common signal is:

$H^{\[R,i\]}{v}_{c,2}^{\[i\]}=H^{\[R,i+1\]}{v}_{c,1}^{\[i+1\]}=u_c^i,i\∈\{1,2,3\};$

wherein H^[R,i]Representing the channel transmission matrix from the ith communication node to the relay node R,a precoding vector, H, representing the need for a private signal from the ith communication node to the jth communication node^[R,j]Representing the channel transmission matrix from the jth communication node to the relay node R,a precoding vector representing the need for a private signal from the jth communication node to the ith communication node,an equivalent transmission channel for private information between the ith communication node and the jth communication node, pi (i, j) represents a sequentially increasing number,indicating the precoding vector, H, required by the second path of common signal sent by the ith communication node^[R,i+1]Represents the channel transmission matrix from the i +1 th communication node to the relay node R,represents the precoding vector needed by the first path of common signal sent by the (i + 1) th communication node,an equivalent transmission channel for representing common information between the ith communication node and the (i + 1) th communication node;

(3-2) the relay node performs signal transformation on the mixed heterogeneous signal received in the step (2), and obtains a decoding estimation value after the subspace alignment of the mixed heterogeneous signal according to a subspace alignment equation of the private signal and a subspace alignment equation of the public signal:

wherein, U_pRepresenting the private signal equivalent channel transmission matrix sent by all communication nodes,U_crepresenting the common signal equivalent channel transmission matrix transmitted by all communication nodes,U_pand U_cAre all non-singular arrays;andrespectively obtained from the subspace alignment equation of the private signal and the subspace alignment equation of the public signal in the step (3-1),representing a private signal sent by the ith communication node to the jth communication node,representing a common signal transmitted by the i-th communication node, n^[R]Representing relay nodesA noise vector of R;whereinThe equivalent private signals after the 12 private signals sent by the 4 communication nodes are subjected to signal subspace alignment are represented,m is any natural number from 1 to 6;the equivalent common signal after the 6 common signals sent by the 4 communication nodes are subjected to signal subspace alignment is shown,the relay node R respectively obtains decoding estimated values by using a zero forcing decoding algorithm:

(4) and (3) carrying out physical layer network coding on the decoding estimation value obtained in the step (3-2) by the relay node to obtain a network coding signal, and carrying out broadcast transmission after carrying out precoding transmission vector weighting on the network coding signal in a second time slot-broadcast transmission stage:

(4-1) the relay node performs physical layer network coding modulation on the decoding estimation value obtained in the step (3-2) to obtain a network coding signal:wherein Represents a private signal in the network coded signal,represents the common signal in the network coded signal,represents an exclusive or operation;

(4-2) the relay node aligns the user signal directions receiving the same network coding signal to the same signal subspace by using the intersecting subspace principle, determines a precoding vector which can align the private signal direction in the network coding signal to the same signal subspace according to the formula (3), and determines a precoding vector which can align the public signal direction in the network coding signal to the same signal subspace according to the formula (4):

wherein H^[i,R]Representing the channel transmission matrix from the relay node R to the i-th communication node, H^[j,R]Representing the channel transmission matrix of the relay node R to the jth communication node,indicating that the ith communication node receives the precoding vectors required by the private signals in the network coding signals of the communication node i and the communication node j,indicating that the jth communication node receives precoding vectors required by private signals in the network coding signals of the communication node i and the communication node j,indicating that the ith communication node receives a precoding vector required by a common signal in the network coded signals of the communication node i and the communication node j,representing a precoding vector required by a j-th communication node for receiving a common signal in network coding signals of a communication node i and a communication node j, and span (X) representing a space formed by column vectors of an arbitrary matrix X;

(4-3) respectively obtaining a subspace alignment equation of a private signal in the network coding signal and a subspace alignment equation of a public signal in the network coding signal according to the subspace alignment condition of the network coding signal:

the subspace alignment equation for the private signal in the network coded signal is:

the subspace alignment equation for the common signal in the network coded signal is:

wherein,an equivalent transmission channel representing a private signal between the ith communication node and the jth communication node,representing an equivalent transmission channel, pi, for a common signal between an ith communication node and a jth communication nodep (i, j) and π c (i, j) each represent a number that increases sequentially according toAndconstructing a receive precoding matrix for an ith communication nodeI.e. all communication nodes are as follows:

$Q^{\[1\]}={\[q_p^{\[1,2\]}{q}_p^{\[1,3\]}{q}_p^{\[1,4\]}{q}_c^{\[1,2\]}{q}_c^{\[1,3\]}{q}_c^{\[1,4\]}\]}^T$

$Q^{\[2\]}={\[q_p^{\[2,1\]}{q}_p^{\[2,3\]}{q}_p^{\[2,4\]}{q}_c^{\[2,1\]}{q}_c^{\[2,3\]}{q}_c^{\[2,4\]}\]}^T$

$Q^{\[3\]}={\[q_p^{\[3,1\]}{q}_p^{\[3,2\]}{q}_p^{\[3,4\]}{q}_c^{\[3,1\]}{q}_c^{\[3,2\]}{q}_c^{\[3,4\]}\]}^T$

$Q^{\[4\]}={\[q_p^{\[4,1\]}{q}_p^{\[4,2\]}{q}_p^{\[4,3\]}{q}_c^{\[4,1\]}{q}_c^{\[4,2\]}{q}_c^{\[4,3\]}\]}^T$

(4-4) obtaining equivalent channels by utilizing subspace alignment:

$Z={\[z_p^{\mathrm{\π}p(1,2)}{z}_p^{\mathrm{\π}p(1,3)}{z}_p^{\mathrm{\π}p(1,4)}{z}_p^{\mathrm{\π}p(2,3)}{z}_p^{\mathrm{\π}p(2,4)}{z}_p^{\mathrm{\π}p(3,4)}{z}_c^{\mathrm{\π}c(1,2)}{z}_c^{\mathrm{\π}c(1,3)}{z}_c^{\mathrm{\π}c(1,4)}{z}_c^{\mathrm{\π}c(2,3)}{z}_c^{\mathrm{\π}c(2,4)}{z}_c^{\mathrm{\π}c(3,4)}\]}^H$

removing private signal equivalent channel vectors from equivalent channelsThe equivalent channel obtained isFromMedium erasure common signal equivalent channel vectorAnd(m ≠ n ≠ i ≠ j) the equivalent channel obtained is

(4-5) respectively acquiring the precoded transmission vector of the private signal and the precoded transmission vector of the public signal through the following formulas:

precoded transmission vector of private signal:

$T_p^1\∈null\left({\tilde{Z}}_p^{\mathrm{\π}p(1,2)}\right),T_p^2\∈null\left({\tilde{Z}}_p^{\mathrm{\π}p(1,3)}\right),T_p^3\∈null\left({\tilde{Z}}_p^{\mathrm{\π}p(1,4)}\right),$

$T_p^4\∈null\left({\tilde{Z}}_p^{\mathrm{\π}p(2,3)}\right),T_p^5\∈null\left({\tilde{Z}}_p^{\mathrm{\π}p(2,4)}\right),T_p^6\∈null\left({\tilde{Z}}_p^{\mathrm{\π}p(3,4)}\right),$

precoding transmission vector of common signal:

$T_c^1\∈null\left({\tilde{Z}}_c^{\mathrm{\π}c(1,2),\mathrm{\π}c(3,4)}\right),T_c^2\∈null\left({\tilde{Z}}_c^{\mathrm{\π}c(1,3),\mathrm{\π}c(2,4)}\right),T_c^3\∈null\left({\tilde{Z}}_c^{\mathrm{\π}c(1,4),\mathrm{\π}c(2,3)}\right)$

where null (X) denotes the null space of an arbitrary matrix X,a precoded transmission vector representing the private signal in the pi p (i, j) th network coding combination,a precoded transmit vector representing the common signal in the π c (i, j) th and π c (m, n) th network coding combinations;

(4-6), in the second time slot, namely the broadcast transmission phase, the relay node transmits the broadcast signal to the communication node:

wherein, the relay node R sends the broadcast signal of And T_c ⁿRespectively, the precoded transmission vectors of the private signals and the precoded transmission vectors of the public signals determined in step (4-5),the mth transmission signal representing the relay node R network-encoded private signal,the nth transmission signal represents the relay node R after network coding the public signal;

(5) and the communication node receives the broadcast signals sent by the relay node, and performs interference suppression on the broadcast signals broadcast and sent by the relay node by using the precoding transmitting vector and the precoding receiving vector:

(5-1) utilizing the precoding emission vector of the private signal obtained in the step (4-5) to enable the communication node to receive the interference private signalThe equivalent transmission channel of (a) satisfies:

$q_p^{\[i,j\]}{H}^{\[i,R\]}{T}_p^m=0,q_p^{\[j,i\]}{H}^{\[j,R\]}{T}_p^m=0,$

transforming the interference signal in the broadcast signal into the null space of the desired private signal space in the broadcast signal to eliminate the interference signal in the signal received by the communication node, wherein H^[i,R]Representing the channel transmission matrix of the relay node R to the ith communication node,precoding a transmission vector for the private signal determined in step (4-5);

precoding a transmitting vector by using the common signal obtained in the step (4-5) to enable the received interference common signalThe equivalent transmission channel of (a) satisfies:

$q_c^{\[i,j\]}{H}^{\[i,R\]}{T}_c^n=0,q_c^{\[j,i\]}{H}^{\[j,R\]}{T}_c^n=0,$

transforming the interference signal in the broadcast signal into the null space of the desired common signal space in the broadcast signal to eliminate the interference signal in the signal received by the communication node, wherein H^[i,R]Representing the channel transmission matrix, T, from the relay node R to the ith communication node_c ⁿPrecoding a transmission vector for the common signal determined in step (4-5);

(5-2) the equivalent received signal of the ith communication node obtained after the interference signal is eliminated is:

$\begin{array}{c}{\hat{y}}^{\[i\]}=Q^{\[i\]}{H}^{\[i,R\]}\left(\underset{m=1}{\overset{6}{\Σ}}{T}_p^m{s}_{R,p}^m+\underset{n=1}{\overset{3}{\Σ}}{T}_c^n{s}_{R,c}^n\right)+{\hat{n}}^{\[i\]}\\ ={\hat{H}}^{\[i,R\]}{S}_R^i+{\hat{n}}^{\[i\]}\end{array}$

wherein,is the received precoding matrix, H, of the communication node i^[i,R]Representing the channel transmission matrix of the relay node R to the ith communication node,andrespectively, the precoded transmission vectors of the private signals and the precoded transmission vectors of the public signals determined in step (4-5),the mth transmission signal representing the relay node R network-encoded private signal,represents the nth transmission signal after the relay node R network-encodes the common signal,indicating the expected received signal of the communication node i,a noise vector representing the communication node i,is a reception equivalent transmission matrix of the ith communication node and is a diagonal matrix;

(6) and decoding the equivalent received signal of a certain communication node from which the interference signal is eliminated by network coding to obtain an estimated value of the mixed heterogeneous signal expected to be received by the communication node:

(6-1), reception equivalent transmission matrix of ith communication nodeThe method comprises the steps that a diagonal matrix is used, and a zero forcing decoding algorithm is used for obtaining a decoding signal of the ith communication node;

(6-2) performing network coding decoding operation by using the signal sent by the ith communication node and the decoded signal in the step (6-1) to obtain an estimated value of the private signal and an estimated value of the public signal expected to be received by the ith communication node, wherein the formulas of the estimated values of the private signal and the public signal are as follows:

${\hat{s}}_p^{\[i,j\]}=(s_p^{\[i,j\]}\⊕s_p^{\[j,i\]})\⊕s_p^{\[j,i\]},{\hat{s}}_c^{\[j\]}=(s_c^{\[i\]}\⊕s_c^{\[j\]})\⊕s_c^{\[i\]},$

wherein,an estimated value of a private signal sent by the jth communication node to the ith communication node, an estimated value of a public signal expected to be received by the ith communication node comprises estimated values of public signals sent by the other three communication nodes, andan estimate representing a common signal transmitted by a jth communication node, where the jth communication node is other than the ith communication nodeOne of his three communication nodes;representing a private signal sent by the ith communication node to the jth communication node,representing a private signal sent by the jth communication node to the ith communication node,representing a common signal transmitted by the ith communication node,representing the common signal transmitted by the jth communication node.

2. The multi-source heterogeneous signal interference suppression method based on signal subspace alignment according to claim 1, wherein the physical layer network coding in the step (4) comprises the following steps:

first, for private signalsAnd private signalsPerforming exclusive-or operation to obtain a private signal in the network coding signalSecondly, for common signalsAnd a common signalCarry out XOROperate to obtain a common signal in the network coded signalWherein,representing a private signal sent by the jth communication node to the ith communication node,representing a private signal sent by the ith communication node to the jth communication node,representing a common signal transmitted by the ith communication node,indicating a common signal transmitted by the jth communication node, i ≠ j.