CN104158778B - 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 spatial phase modulation

Technical field

The invention belongs to Communication Anti-Jamming Techniques field, is related to spatial modulation (Spatial Modulation, SM) technology, The precoding technique (Transmit Precoding) of transmitting terminal, phase place technology (Phase Rotation, PR), phase shift key Control (Phase Shifting Keying, PSK) modulation technique, and its MIMO (the Multiple Input Multiple of correlation Output) technology.

Background technology

MIMO modulation techniques are the high speed transmission technologies under a kind of wireless environment, and it is configured in transmitting terminal and/or receiving terminal More antenna elements, and with reference to advanced Space Time Coding modulation scheme, by making full use of to spatial degrees of freedom, can band Come extra diversity, multiplexing and beam forming gain.

Recently, SM technologies are proposed as a kind of new modulation technique as a kind of new MIMO modulation schemes.The skill The ultimate principle of art is by activating different antennas, antenna index value being come into transmission information bit for modulation.This transmission The essence of scheme is the independence using different channels in mimo system.Because every time an only antenna is activated, Jin Er Transmitting terminal only needs to a radio frequency unit and this process energy hop bit, so transfer rate is this approach increases, and Reduce the cost and complexity of mimo system.

Under many transmission plans, under same message transmission rate, the SM systematic functions based on PSK modulation techniques will Better than the SM systems based on QAM modulation technology.However, in the SM systems based on PSK modulation techniques, channel column vectors Angle is larger to the performance impact of system.

The content of the invention

The purpose of the present invention, the problem for being aiming at existing in above-mentioned prior art, there is provided a kind of for space phase tune The method for precoding of system.

Technical scheme：A kind of method for precoding for spatial phase modulation, it is characterised in that including following Step：

A. the channel matrix H that receiving terminal is obtained according to estimation, obtains precoding vector θ；Concretely comprise the following steps：

A1. minimum range d in planisphere between any two points is obtained_min(H, θ), concrete grammar is to adopt formula：

Wherein, H is channel matrix, and it is N that θ is length_t, initial value be all 1 precoding vector, Λ represent PSK modulation symbol Number set, x_i, x_jFor the symbol in Λ；

A2. for each element in Λ can correspond to a transmitting antenna, we can be according to minimum range d_min(H, Close two nearest constellation points θ) are determined, while finding out sequence number m and n of the transmitting antenna corresponding to them, whether m is judged Equal to n, if so, then using initial θ values as precoding vector, if it is not, then entering step a3；

A3. angular misalignment △ θ=2 π/N is set, the collection of alternative precoding vector is combined into：

θ_k=diag 1 ..., k Δ θ ..., 1 }, k=1 ..., N

Wherein N is positive integer；

According to formula

Optimum θ vectors are chosen as precoding vector；

B. m=m is produced by digitized information source₁+m₂Position information bit, wherein front m₁Antenna index ratio of the position as SM modulation Spy, rear m₂M-QAM modulation is done in position according to the value of M, and wherein M is order of modulation；SM modulation is carried out to this m positions information bit； After symbolic vector x to after modulation, precoding, i.e. x '=θ x are carried out to it.X ' Jing radio frequencies are sent；

C. after channel, receiving terminal obtains receiving signal y modulated signal；

D. receiving terminal is detected with reference to precoding vector and channel information to the signal y for receiving.

Beneficial effects of the present invention are, the invention provides a kind of propose that a kind of new precoding is calculated based on SM-PSK systems Method, the technology carries out phase place, energy by the symbol that wherein one antenna of two antennas to correlation maximum is launched Enough make minimum euclidean distance between constellation point become big, make system in the feelings for introducing minimum feedback quantity and the complexity for increasing very little Under condition, the BER performances for making system are significantly improved.

Description of the drawings

Fig. 1 is traditional SM system block diagrams.

Fig. 2 is the SM system block diagrams of phase place precoding algorithms proposed by the present invention.

Specific embodiment

The present invention is described in detail below in conjunction with the accompanying drawings

The specific embodiment of the present invention is described below in conjunction with the accompanying drawings, so as to those skilled in the art preferably Understand the present invention.Requiring particular attention is that, in the following description, when known function and design detailed description perhaps When can desalinate the main contents of the present invention, these descriptions are said be ignored here.

For preferably the present invention will be described, the term used in technical solution of the present invention and spatial modulation system are first introduced System transmitter architecture.

Spatial modulation：If Fig. 1, b are the bit datas for needing transmission, the matrix of a L × T, wherein L=can be considered Log2 (M)+log2 (Mary) is the amount of bits entrained by a SM modulation symbol, and Mary is quadrature amplitude modulation (Quadrature Amplitude Modulation, QAM) exponent number.As can be seen that the ratio that a SM modulation symbol is carried by Special quantity is together decided on by QAM modulation exponent number and number of transmission antennas.SM modulation criterions are to be transformed into b according to SM translation tables The matrix x of one M × T.In x, string represents the data for sending at a moment, any string only one of which non-zero, meaning Taste any time and only has an antenna to send data.Fig. 2, gives four transmitting antennas, and modulation symbol is the example of BPSK Son.

Specific embodiments of the present invention system diagram as shown in Figure 2.

Transmitter architecture is roughly divided into following several steps：

Step 1：It is determined that the parameter of the system to be selected, that is, determine transmitting antenna number nTx, reception antenna number nRx is adjusted The exponent number M of system.

Step 2：Then the amount of bits of a frame is calculated, this frame data is divided into into two groups, one group is antenna index bit, For the transmitting antenna for selecting to be activated, one group is modulation bit, for carrying out PSK modulation.Again the transmission vector to obtaining enters Row SM is modulated；After symbolic vector after being modulated, precoding is carried out to it, the precoding vector in the processing procedure is by connecing Receiving end feedback is obtained.

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

1st, minimum range d in planisphere between any two points is obtained_min(H, θ), concrete grammar is to adopt formula：

Wherein, H is channel matrix, and it is N that θ is length_t, initial value be all 1 precoding vector, Λ represent through space adjust The PSK modulation symbol set of system, x_i, x_jFor the element in Λ；

2nd, because each element in Λ can correspond to a transmitting antenna, we can be according to minimum range d_min(H,θ) Close two nearest constellation points are determined, while find out sequence number m and n of the transmitting antenna corresponding to them, judges m whether etc. In n, if so, then using initial θ values as precoding vector, if it is not, then entering step 3；

3rd, angular misalignment △ θ=2 π/N is set, the collection of alternative precoding vector is combined into：

θ_k=diag 1 ..., k Δ θ ..., 1 }, k=1 ..., N

According to formula

Optimum θ vectors are chosen as precoding vector, and feeds back to transmitting terminal.

Receiver is received after signal y, above-mentioned using arriving in detection process through Maximum Likelihood Detection module Precoding vector.

Claims (1)

1. a kind of method for precoding for spatial phase modulation, it is characterised in that comprise the following steps：

A. the channel matrix H that receiving terminal is obtained according to estimation, obtains precoding vector θ；Concretely comprise the following steps：

A1. minimum range d in planisphere between any two points is obtained_min(H, θ), concrete grammar is to adopt formula：

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

Wherein, H is channel matrix, and it is N that θ is length_t, initial value be all 1 precoding vector, Λ represents PSK modulation symbol collection Close；

A2. for each element in Λ can correspond to a transmitting antenna, we can be according to minimum range d_min(H, θ) is true Close two nearest constellation points are made, while finding out sequence number m and n of the transmitting antenna corresponding to them, judges whether m is equal to N, if so, then using initial θ values as precoding vector, if it is not, then entering step a3；

A3. angular misalignment △ θ=2 π/N is set, the collection of alternative precoding vector is combined into：

θ_k=diag 1 ..., k Δ θ ..., 1 }, k=1 ..., N

Wherein N is positive integer；

According to formula

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

Optimum θ vectors are chosen as precoding vector；

B. m=m is produced by digitized information source₁+m₂Position information bit, wherein front m₁The antenna index bit that position is modulated as SM, after m₂M-QAM modulation is done in position according to the value of M, and wherein M is order of modulation；SM modulation is carried out to this m positions information bit；Modulated After symbolic vector x afterwards, precoding, i.e. x '=θ x are carried out to it, x ' Jing radio frequencies are sent；

C. after channel, receiving terminal obtains receiving signal y modulated signal；

D. receiving terminal is detected with reference to precoding vector and channel information to the signal y for receiving.