CN104158778A - Pre-coding method for use in spatial phase modulation - Google Patents

Abstract

The invention belongs to the technical field of communication interference resistance, and particularly relates to a pre-coding method for use in spatial phase modulation. The pre-coding method disclosed by the invention is mainly characterized in that a pre-coding vector is obtained through a receiving end according to an estimated channel matrix H. The method comprises the following specific steps: determining the serial numbers m and n of transmitting antennae corresponding to two constellation points according to the minimum distance between any two points in the constellation diagram of an SM-PSK (Spatial Modulation-Phase Shifting Keying) system; if m is equal to n, directly using theta which is selected at last as an initial vector without adopting remaining algorithms in the step; and if m is unequal to n, setting an angle deviation value deltatheta as 2pi/N, and selecting an optimal vector as a pre-coding vector from a set of alternative pre-coding vectors. The method has the beneficial effects that the minimum Euclidean distance between adjacent constellation points can be expanded, and the BER (Bit Error Rate) performance of the system is improved remarkably under the condition that minimal feedback quantity is introduced into the system and the complexity is increased slightly. The invention is particularly suitable for the pre-coding method for use in the spatial phase modulation.

Description

A kind of method for precoding for space phase modulation

Technical field

The invention belongs to Communication Anti-Jamming Techniques field, relate to spatial modulation (Spatial Modulation, SM) technology, the precoding technique (Transmit Precoding) of transmitting terminal, phase rotating technology (Phase Rotation, PR), phase shift keying (Phase Shifting Keying, PSK) modulation technique, and relevant MIMO (Multiple Input Multiple Output) technology.

Background technology

MIMO modulation technique is the high speed transmission technology under a kind of wireless environment, it configures more antenna element at transmitting terminal and/or receiving terminal, and in conjunction with advanced Space Time Coding modulation scheme, by making full use of spatial degrees of freedom, can bring extra diversity, multiplexing and beam forming gain.

Recently, SM technology is suggested as a kind of new modulation technique as a kind of new MIMO modulation scheme.The general principle of this technology is by activating different antennas, and antenna index value is carried out to transmission information bit for modulation.The essence of this transmission plan is to utilize the independence of different channels in mimo system.Because only have an antenna to be activated at every turn, and then only need a radio frequency unit and this process energy hop bit at transmitting terminal, so this scheme has improved transmission rate, and reduced cost and the complexity of mimo system.

Under a lot of transmission plans, under same message transmission rate, based on PSK modulation technique SM systematic function be better than based on QAM modulation technique SM system.But, based on PSK modulation technique SM system in, the angle of channel column vectors is larger to the performance impact of system.

Summary of the invention

Object of the present invention, is exactly for the problem existing in above-mentioned prior art, and a kind of method for precoding for space phase modulation is provided.

Technical scheme of the present invention: a kind of method for precoding for space phase modulation, it is characterized in that, comprise the following steps:

A. receiving terminal, according to the channel matrix H of estimating to obtain, obtains precoding vector θ; Concrete steps are:

A1. obtain the minimum range d between any two points in planisphere _min(H, θ), concrete grammar is for adopting formula:

$\begin{array}{c}{d}_{\min }(H,\mathrm{\θ})=\underset{x_i\≠x_j}{\underset{x_i,x_j\∈\mathrm{\Λ},}{\min }}{\left|\right|\mathrm{H\θ}(x_i-x_j)\left|\right|}_F\\ =\underset{e_{\mathrm{ij}}\∈E}{\min }{\left|\right|\mathrm{H\θ}{e}_{\mathrm{ij}}\left|\right|}_F\end{array}$

Wherein, H is channel matrix, and θ is that length is N _t, initial value is 1 precoding vector entirely, Λ represents the set of PSK modulation symbol, x _i, x _jfor the symbol in Λ;

A2. can a corresponding transmit antennas for the each element in Λ, we can be according to minimum range d _min(H, θ) determines close two nearest constellation point, finds out sequence number m and the n of their corresponding transmitting antenna simultaneously, judges whether m equals n, if so, adopts initial θ value as precoding vector, if not, enters step a3;

A3. establish angular misalignment Δ θ=2 π/N, the set of alternative precoding vector is:

θ _k＝diag{1,…,kΔθ,…,1},k＝1,…,N

↑mth

According to formula

${\mathrm{\θ}}_{\mathrm{opt}}=\underset{\mathrm{\θ}={\mathrm{\θ}}_k,k=1,\·\·\·,N}{\arg \max }{d}_{\min }(H,\mathrm{\θ})$

Choose optimum θ vector as precoding vector;

B. produce m=m by digitlization information source ₁+ m ₂position information bit, wherein front m ₁position is as the antenna index bit of SM modulation, rear m ₂m-QAM modulation is done according to the value of M in position, and wherein M is order of modulation; This m position information bit is carried out to SM modulation; Obtain, after the symbolic vector x after modulation, it being carried out to precoding, i.e. x '=θ x.X ' is sent through radio frequency;

C. modulation signal is after channel, and receiving terminal obtains receiving signal y;

D. receiving terminal in conjunction with precoding vector and channel information to the received signal y detect.

Beneficial effect of the present invention is, the invention provides a kind of based on a kind of new precoding algorithm of SM-PSK system proposition, this technology is carried out phase rotating by the symbol that wherein antenna of two of correlation maximum antennas is launched, can make minimum euclidean distance between constellation point become large, making system introduce minimum feedback quantity and increase very little complexity, the BER performance of system is significantly improved.

Brief description of the drawings

Fig. 1 is traditional SM system block diagram.

Fig. 2 is the SM system block diagram of the phase place precoding algorithm that proposes of the present invention.

Embodiment

Below in conjunction with accompanying drawing, the present invention is described in detail

Below in conjunction with accompanying drawing, the specific embodiment of the present invention is described, so that those skilled in the art understands the present invention better.Requiring particular attention is that, in the following description, in the time that perhaps the detailed description of known function and design can desalinate main contents of the present invention, these are described in here and say and be left in the basket.

For the present invention will be described better, first introduce technical solution of the present invention term used and spatial modulation system transmitter structure.

Spatial modulation: as Fig. 1, b is the Bit data that needs transmission, can be regarded as the matrix of a L × T, wherein L=log2 (M)+log2 (Mary) is an amount of bits that SM modulation symbol is entrained, Mary is quadrature amplitude modulation (Quadrature Amplitude Modulation, QAM) exponent number.Can find out, the amount of bits that SM modulation symbol can carry is determined jointly by QAM order of modulation and number of transmission antennas.SM modulation criterion is the matrix x that according to SM translation table, b is transformed into a M × T.In x, row represent the data that moment sends, and any row only have a non-zero, mean that any time only has an antenna to send data.Fig. 2, has given a four transmit antennas, the example that modulation symbol is BPSK.

Specific embodiment of the invention scheme system diagram as shown in Figure 2.

Transmitter architecture is roughly divided into following a few step:

Step 1: determine the parameter of the system that will select, determine number of transmit antennas nTx, reception antenna number nRx, the exponent number M of modulation.

Step 2: then calculate the amount of bits of a frame, these frame data are divided into two groups, one group is antenna index bit, for the transmitting antenna of selecting to be activated, one group is modulation bit, for carrying out PSK modulation.Again the transmission vector obtaining is carried out to SM modulation; Obtain, after the symbolic vector after modulation, it being carried out to precoding, the precoding vector in this processing procedure is obtained by receiving terminal feedback.

For receiver section, receiver, according to the order of modulation of channel information and system, calculates suitable precoding vector: concrete grammar is:

1, obtain the minimum range d between any two points in planisphere _min(H, θ), concrete grammar is for adopting formula:

$\begin{array}{c}{d}_{\min }(H,\mathrm{\θ})=\underset{x_i\≠x_j}{\underset{x_i,x_j\∈\mathrm{\Λ},}{\min }}{\left|\right|\mathrm{H\θ}(x_i-x_j)\left|\right|}_F\\ =\underset{e_{\mathrm{ij}}\∈E}{\min }{\left|\right|\mathrm{H\θ}{e}_{\mathrm{ij}}\left|\right|}_F\end{array}$

Wherein, H is channel matrix, and θ is that length is N _t, initial value is 1 precoding vector entirely, Λ represents the PSK modulation symbol set through spatial modulation, x _i, x _jfor the element in Λ;

2, can a corresponding transmit antennas due to the each element in Λ, we can be according to minimum range d _min(H, θ) determines close two nearest constellation point, finds out sequence number m and the n of their corresponding transmitting antenna simultaneously, judges whether m equals n, if so, adopts initial θ value as precoding vector, if not, enters step 3;

3, establish angular misalignment Δ θ=2 π/N, the set of alternative precoding vector is:

θ _k＝diag{1,…,kΔθ,…,1},k＝1,…,N

↑mth

According to formula

${\mathrm{\θ}}_{\mathrm{opt}}=\underset{\mathrm{\θ}={\mathrm{\θ}}_k,k=1,\·\·\·,N}{\arg \max }{d}_{\min }(H,\mathrm{\θ})$

Choose optimum θ vector as precoding vector, and feed back to transmitting terminal.

Receiver receives after signal y, through Maximum Likelihood Detection module, in testing process, will use above-mentioned precoding vector.

Claims (1)

1. for a method for precoding for space phase modulation, it is characterized in that, comprise the following steps:

A. receiving terminal, according to the channel matrix H of estimating to obtain, obtains precoding vector θ; Concrete steps are:

A1. obtain the minimum range d between any two points in planisphere _min(H, θ), concrete grammar is for adopting formula:

$\begin{array}{c}{d}_{\min }(H,\mathrm{\θ})=\underset{x_i\≠x_j}{\underset{x_i,x_j\∈\mathrm{\Λ},}{\min }}{\left|\right|\mathrm{H\θ}(x_i-x_j)\left|\right|}_F\\ =\underset{e_{\mathrm{ij}}\∈E}{\min }{\left|\right|\mathrm{H\θ}{e}_{\mathrm{ij}}\left|\right|}_F\end{array}$

Wherein, H is channel matrix, and θ is that length is N _t, initial value is 1 precoding vector entirely, Λ represents the set of PSK modulation symbol;

A2. can a corresponding transmit antennas for the each element in Λ, we can be according to minimum range d _min(H, θ) determines close two nearest constellation point, finds out sequence number m and the n of their corresponding transmitting antenna simultaneously, judges whether m equals n, if so, adopts initial θ value as precoding vector, if not, enters step a3;

A3. establish angular misalignment Δ θ=2 π/N, the set of alternative precoding vector is:

θ _k＝diag{1,…,kΔθ,…,1},k＝1,…,N

↑mth

According to formula

${\mathrm{\θ}}_{\mathrm{opt}}=\underset{\mathrm{\θ}={\mathrm{\θ}}_k,k=1,\·\·\·,N}{\arg \max }{d}_{\min }(H,\mathrm{\θ})$

Choose optimum θ vector as precoding vector;

B. produce m=m by digitlization information source ₁+ m ₂position information bit, wherein front m ₁position is as the antenna index bit of SM modulation, rear m ₂m-QAM modulation is done according to the value of M in position, and wherein M is order of modulation; This m position information bit is carried out to SM modulation; Obtain, after the symbolic vector x after modulation, it being carried out to precoding, i.e. x '=θ x, sends x ' through radio frequency;

C. modulation signal is after channel, and receiving terminal obtains receiving signal y;

D. receiving terminal in conjunction with precoding vector and channel information to the received signal y detect.