CN105827289A - Limited feedback pre-coding method of generalized spatial modulation system - Google Patents

Abstract

The invention provides a limited feedback pre-coding method of a generalized spatial modulation system. The method comprises a first step of codebook design and a second step of code word selection. Codebook design is shared in transmitting and receiving ends, a training channel matrix is classified, corresponding code words are updated, and a pre-coding library is provided for different channels. During code word selection, proper code words are selected from a designed codebook according to present channel information at the reception end, and are back fed to the transmitting end to carry out signal pre-coding. According to the invention, signal pre-coding design in realized in the generalized spatial modulation system, and under the condition of limited feedback cost, the error rate is effectively reduced, and further the signal detection performance is improved.

Description

A kind of limited feedback precoding method of generalized spatial modulation system

Technical field:

The present invention relates to wireless communication technology field, be specifically related to a kind of limited feedback precoding method at generalized spatial modulation system.

Background technology:

Along with being gradually improved of wireless communication technology, " green, energy-conservation, sustainable " has become a most important developing direction in following 5G mobile communication.Spatial modulation (SM), as a kind of novel multiple antennas modulation technique, only activates a transmission antenna by each time slot, can effectively reduce system energy consumption, and thoroughly eliminate interchannel interference (ICI).For improving spectrum efficiency further, activation antenna number is expanded to many from one by generalized space modulation (GSM), significant increase signal transmission rate.Precoding technique carries out pretreatment to sending signal, can effectively reduce the detection bit error rate thus improve systematic function, but the research for spatial modulation system is less.

For ensureing the special construction of spatial modulation signal, some are suggested for the pre-coding scheme of SM/GSM system, it is broadly divided into based on mutual information maximization and maximizes, based on free distance, the diagonal angle pre-coding scheme that two classes, such as XinrongGuan proposed in 2015 in MISO precoding and the WeiWang of proposition in 2013.But existing scheme needs the known complete channel information (CSIT) of transmitting terminal mostly, its huge feedback overhead does not possess actual operability for especially frequency division multiplexing (FDD) system.The limited feedback precoding model that D.J.Love proposed under conventional MIMO system in 2003, utilizes sending and receiving end to share portion code book only feedback code sequence number together, reduces feedback overhead largely." LimitedFeedbackPrecoderDesignforSpatialModulationinMIMOS ystem " that Ming-ChunLee delivered on IEEECommunicationLetter in 2015 (IEEE is organized in the SCI periodical of the communications field, " the limited feedback precoding design of spatial modulation in mimo system "), proposing the method utilizing D.J.Love Limited Feedback model to carry out design space modulation precoding, the research having filled up SM-MIMO limited feedback precoding is blank.But the substantial amounts of higher dimensional matrix calculating of this method needs and convex Optimization Solution, computational complexity is high；And the popularization for GSM-MIMO system still has limitation.This means that the limited feedback precoding scheme under a kind of effective generalized spatial modulation system that designs need exploitation.

Summary of the invention:

The problem that it is an object of the invention to overcome above-mentioned prior art to exist, for generalized spatial modulation system, a kind of limited feedback precoding method at generalized spatial modulation system is proposed, use the Limited Feedback model of D.J.Love, utilize iteration that training matrix is sorted out and update code word based on maximum free distance and obtain code book, and selected suitable code word by receiving terminal according to current channel information and feed back sequence number and carry out precoding to transmitting terminal, thus effectively reduce the bit error rate of signal detection, improve the systematic function of generalized space modulation.

The present invention realizes according to techniques below scheme:

A kind of limited feedback precoding method of generalized spatial modulation system, including the first step, codebook design and second step, codeword selection；Codebook design is that sending and receiving end is shared, and utilizes training channel matrix classify and update corresponding codewords, provides precoding storehouse for different channels；Codeword selection according to current receiving terminal channel information, selects suitable code word from the code book of design, and feeds back to transmitting terminal and carry out signal precoding.Specific as follows:

Step A codebook design: training channel matrix is classified based on neighbouring criterion, and solve maximum free distance problem to update corresponding codewords, this process iteration until convergence thus obtain final code book

Iterative process comprises the steps: every time

Step A1: according to current code book(or initial codebook), channel matrix collection will be trained in a large number based on neighbouring criterion:It is classified as K class, wherein

$f(p_q,H)=\frac{1}{\left|C\right|{\log }_2\left|C\right|}\underset{i=1}{\overset{\left|C\right|}{\Σ}}\underset{j\≠i}{\overset{\left|C\right|}{\Σ}}B(i,j)Q\left(\sqrt{\frac{\mathrm{\ρ}}{2}{d}_{ij}^2\left(p_q\right)}\right)$

For the bit error rate upper bound under Maximum Likelihood Detection, (i, j) for sending signal x for B_iWith x_jBetween error bit number,For receiving the Euclidean distance between signal, x '_iWith x '_jFor based on p_qTransmission signal after precoding, ρ is signal to noise ratio, and | C | is for sending the size of signal collection, and Q () is the Q function in mathematical statistics；

Step A2: to each class channel matrix subsetSolve maximum free distance problem:

Update code word p of correspondence_qThus obtain new code bookWherein P is for always transmitting energy constraint.

The renewal process solving corresponding every class code word in described step A2 comprises the steps:

Step A21: to channel matrix H and transmission signal x, be reconstructed with R-TAC method, i.e. according to activating antenna combination sequence sets

$H^{\left(new\right)}=\[H_{L_1},H_{L_2},...,H_{L_N}\]$

$x^{\left(new\right)}={\[x_{L_1}^T,x_{L_2}^T,...,x_{L_N}^T\]}^T$

Wherein L_nFor activation sequence subscript, N is total activation composite sequence collection size；

Step A22: according to the channel matrix H of reconstruct^(new)With transmission signal x^(new), calculate the expectation of channel matrixAnd according to current code word(initial code word) solve the convex optimization problem of the approximation (P2) of (P1):

Update code wordWherein(⊙ is that matrix Hadamard is amassed), until meeting the condition of convergenceIteration stopping.

Step B codeword selection: according to current channel information, receiving terminal is from code bookIn select suitable code word p based on neighbouring criterion_q, and sequence number q is fed back to transmitting terminal, modulated signal is carried out precoding and sends by the latter.Specifically include following steps:

Step B1: according to current channel matrix H, receiving terminal with following criterion from code bookMiddle selection code word

$p_q=\arg \underset{p_l}{\min }(p_l,H),l=1,...,K$

And by sequence number q with log₂The expense of K bit feeds back to transmitting terminal；

Step B2: after transmitting terminal receives sequence number q, from code bookMiddle by p_qTaking-up also carries out precoding processing to modulated signal x:

$x_{L_n}^{\′}=diag\left(p_I\right)x_I^{\left(new\right)}$

Wherein I={n_t·(n-1)+1,…,n_tN} is for sending signal x after reconstruct^(new)Nonzero digit subscripting collection, subsequently willVia corresponding activation antenna (subscript) send.

Compared with prior art, there is advantages that

Present invention achieves the limited feedback precoding under generalized spatial modulation system.On the basis of the characteristics of signals ensureing generalized spatial modulation system, by considering the pretreatment of institute's likely planisphere modulated signal, effectively reduce the bit error rate detected thus improve systematic function.Meanwhile, utilize sending and receiving end to share the Limited Feedback model of code book, efficiently solve the problem that under especially Frequency Division Multiplexing system, feedback overhead is limited, have broad application prospects in practical wireless communication systems.

Accompanying drawing illustrates:

Fig. 1 is the generalized spatial modulation system block diagram of limited feedback precoding

Fig. 2 is limited feedback precoding method flow diagram of the present invention.

Detailed description of the invention:

The present invention will be described in detail with embodiment below in conjunction with the accompanying drawings.The present embodiment is implemented under premised on technical solution of the present invention, gives detailed embodiment and concrete operating process, but protection scope of the present invention is not limited to following embodiment.

Embodiment

Under Rayleigh fading and additive white Gaussian noise (AWGN) environment, the signal with the generalized spatial modulation system of limited feedback precoding sends reception process as shown in Figure 1.Using 5 transmission antennas, 2 reception antennas, activating in the case of antenna number is 2, total activate antenna sets amount to 8 kinds may, under BPSK modulates, its transmission code rate is 5bit/Hz/s.To each time slot, front 3 bits determining to activate antenna sequence, the corresponding constellation symbols of rear 2 each bits of bit also carries out precoding processing, is sent to wireless channel by activation antenna subsequently.The code word of this precoding updates the sequence number fed back by receiving terminal and determines, its sending and receiving end is shared with a codebook information.The limited feedback precoding method of the present invention is mainly for codebook design and codeword selection, and the flow chart of method is as shown in Figure 2.Specifically comprise the following steps that

1. the multiple Gaussian matrix of stochastic generation 6000As training channel matrix, initialize code bookFor set { p₀,p₀,p₀,p₀(i.e. K=4), wherein p₀=1¹⁶Complete 1 vector for length 16.It is iteratively repeated: a) based on code book6000 training channel matrixes are sorted out (being classified as 4 classes):

Wherein p_q(q=1 ..., 4) it is code bookIn q-th precoding vector；

And the code book that acquisition of b) more newly arriving every class code word is newInitiallyAnd solve

ObtainAs newEnter next iteration, untilIteration stopping also obtains final p_q, whereinH^(new)=[h₁,h₂,h₁,h₃,h₁,h₄,h₁,h₅,h₂,h₃,h₂,h₄,h₂,h₅,h₃,h₄], x^(new)=[x₁,x₂,x₁,x₃,x₁,x₄,x₁,x₅,x₂,x₃,x₂,x₄,x₂,x₅,x₃,x₄].To p₁,…,p₄After all having updated, i.e. obtain new code book

Repeat process a) and b), until it reaches the iteration upper limit or classification no longer change, and obtain final code book

2. according to currently training channel matrix H, receiving terminal according toFrom code bookThe suitable code word of middle selection also feeds back to transmitting terminal with the expense of 2 bits ({ 00,01,10,11}), and the latter updates code word according to this and carries out signal precoding.

Pass through above step, can realize BPSK modulation under (5,2) precoding of multiple antennas generalized spatial modulation system, in the case of receiving terminal uses maximum likelihood (ML) to detect and be decoded as 5 bit information flow, effectively reduce the bit error rate of signal detection thus improve systematic function.

Claims (4)

1. the limited feedback precoding method of a generalized spatial modulation system, it is characterised in that comprise the steps:

Step A codebook design: classify training channel matrix based on neighbouring criterion, solves maximum free distance problem to update corresponding codewords, this process iteration until convergence thus obtain final code book

Step B codeword selection: according to currently training channel matrix, receiving terminal is from final code bookIn select suitable code word p based on neighbouring criterion_q, and sequence number q is fed back to transmitting terminal, modulated signal is carried out precoding and sends by transmitting terminal.

The limited feedback precoding method of generalized spatial modulation system the most according to claim 1, it is characterized in that, training channel matrix is classified by described step A based on neighbouring criterion, and solves maximum free distance problem to update corresponding codewords, specific as follows:

Step A1: according to current code bookChannel matrix will be trained in a large number based on neighbouring criterion:It is classified as K class, whereinRepresent q class channel matrix subset,

For the bit error rate upper bound under Maximum Likelihood Detection, (i, j) for sending signal x for B_iWith x_jBetween error bit number,For receiving the Euclidean distance between signal, x '_iWith x '_jFor based on p_qTransmission signal after precoding, ρ is signal to noise ratio, and | C | is for sending the size of signal collection, and Q () is the Q function in mathematical statistics；

Step A2: to each class channel matrix subsetSolve maximum free distance problem:

Update code word p of correspondence_qThus obtain new code bookWherein E{ } it is expectation function, P is for always transmitting energy constraint.

The limited feedback precoding method of generalized spatial modulation system the most according to claim 2, it is characterised in that to each class channel matrix subsetSolve maximum free distance problem and update corresponding code word, specific as follows:

Step A21: training channel matrix H and transmission signal x are reconstructed with R-TAC method, i.e. according to activating antenna combination sequence sets

Wherein L_nFor activation sequence subscript, N is total activation composite sequence collection size；

Step A22: according to the training channel matrix H of reconstruct^(new)With transmission signal x^(new), calculate the expectation of channel matrixAnd according to current code wordSolve the convex optimization problem of approximation of maximum free distance problem:

Update code wordWherein

⊙ is that matrix Hadamard is amassed, until meeting the condition of convergenceIteration stopping.

The limited feedback precoding method of generalized spatial modulation system the most according to claim 1, it is characterised in that described step B, receiving terminal is from code bookIn select suitable code word p based on neighbouring criterion_q, and sequence number q is fed back to transmitting terminal, transmitting terminal carries out precoding to modulated signal and sends, specific as follows:

Step B1: according to currently training channel matrix H, receiving terminal with following criterion from code bookMiddle selection code word

And by sequence number q with log₂The expense of K bit feeds back to transmitting terminal；

Step B2: after transmitting terminal receives sequence number q, from code bookMiddle by p_qTaking-up also carries out precoding processing to modulated signal x:

Wherein I={n_t·(n-1)+1,…,n_tN} is for sending signal x after reconstruct^(new)Nonzero digit subscripting collection, subsequently by pretreatedRespectively it is worth via activation sequence subscriptEach antenna correspondence send.