CN103731243A - Power control factor selecting method in space modulating system - Google Patents

Abstract

The invention belongs to the field of communication technologies and particularly relates to an MIMO system based on space modulation. A receiving end receives a best power control factor combination and feeds a modulating symbol proportion shrinking method to an emitting end. The selecting method gives full consideration to the difference of channels corresponding to emitting antennas, adjusts the transmission mode of data according to channel states, namely, a best self-adaptation transmission scheme suitable for the present channel is selected. Following traditional space modulation, the strategy that the same modulating mode is adopted for all the antennas is adopted, so that the bit position dislocation condition is avoided. Meanwhile, the power control factor is properly selected according to the present channel information and transmission symbols on the antennas, and star maps corresponding to different antennas are shrunk according to a certain proportion, so that the purpose of enabling a smallest Euclidean distance between equivalent constellation points to be maximized is achieved, and performance is improved.

Description

Power control factor system of selection in a kind of spatial modulation system

Technical field

The invention belongs to communication technical field, particularly a kind of for the power control factor system of selection based on spatial modulation system.

Background technology

The spatial multiplexing gain of traditional multi-antenna technology is serious depends on the orthogonality between transmitting antenna and reception antenna.A kind of new multi-antenna technology spatial modulation (SM, Spatial Modulation) technology has been avoided inter-carrier interference (Inter-Carrier Interference completely, ICI), and do not require the orthogonality of transmitting antenna and reception antenna, while receiving terminal compares traditional V-PLAST and Alamouti algorithm has reduced the complexity detecting widely.At transmitting terminal, bit information is mapped to certain modulation constellation points and special antenna index, and send data symbol by clue initiation on another day, and at receiving terminal, according to receiving Signal estimation, goes out to send data symbol and antenna sequence number, recovers transmission information., spatial modulation is combined (SM-OFDM) with OFDM technology meanwhile, can obtains the higher availability of frequency spectrum.

From traditional constellation modulation, the minimum Eustachian distance between constellation point increases, and the error rate reduces.Thereby consider that receiving terminal chooses best power control factor combination, and and feed back to transmitting terminal modulation symbol is carried out to ratio scaling, to increase the minimum Eustachian distance between constellation point, thus further improving performance.

Summary of the invention

The present invention for the modulation symbol power factor solving in the existing mimo system different antennae based on spatial modulation identical, thereby performance is subject to certain restrictions, the power control factor system of selection having proposed in a kind of spatial modulation system is promoted performance.

In order to describe easily content of the present invention, first make term definition:

Spatial modulation: refer to utilize the antenna index of mimo system and modulation symbol as a kind of modulation system of the carrier that carries data message, in spatial modulation, message bit stream is divided to be mapped to antenna index and modulation symbol, be that each time slot only has a transmit antennas to be activated, and with the antenna transmission modulation signal of this activation.

Mimo system: refer to that transmitting terminal and receiving terminal are used respectively many antennas, signal is transmitted and received by a plurality of antennas of transmitting terminal and receiving terminal.

FroPenius norm, is also 2-norm, if vector x=[x ₁, x ₂..., x _n], its FroPenius mould value may be calculated so

║x║ _F＝(|x ₁| ²+|x ₂| ²+...+|x _n| ²) ^(1/2)，

Wherein | x ₁| represent to ask x ₁order of magnitude.

Inner product: a kind of vector calculus, suppose vector A=[a ₁, a ₂..., a _n], P=[p ₁, p ₂..., p _n], the inner product of vector is expressed as:

＜A,P＞＝a ₁×p ₁＋a ₂×p ₂＋...＋a _n×p _n。

N _tthe number that represents transmitting antenna, N _rthe number that represents reception antenna, M is order of modulation, N is subcarrier number; Q is P * (N-N _t) binary bit stream matrix, P=log ₂(N _tm);

for the spatial modulation matrix of Q after spatial modulation,

for initialization matrix,

for spatial modulation signal matrix, by U and T matrix, formed front N _t* N _tdimension is T matrix, rear N _t* (N-N _t) tie up as U matrix.S _i(i=1,2 ..., be M) that the i of S is capable, represent the vector that all subcarriers on i root antenna form, S _i(l) be S _il non-zero sub-carriers;

for the non-zero element of the every row of S is carried out to the difference matrix that differential coding obtains, the non-zero sub-carriers on every root antenna is carried out to the matrix obtaining after differential coding, X _ifor the i of X is capable, represent N the vector that subcarrier forms after differential coding on i root antenna, X _i(l) represent X _il non-zero sub-carriers, D ∈ C ^{m * 1}for the constellation point set under M-QAM modulation.P ∈ C ^{k * N} _tfor candidate's power control matrix, k ^*∈ C ^{1 * N} _tfor the optimal proportion zoom factor of selecting in candidate combinations.

Character from spatial modulation: each row of matrix S and X all only have a nonzero element; Transmission matrix

the m row that represent X, i.e. m transmitting vector constantly; m reception vector constantly;

with

refer to respectively transmission matrix and 0 average Gaussian noise.

Implementation method of the present invention is as follows:

A power control factor system of selection in spatial modulation system, specific as follows:

S1, default candidate's power control factor matrix P ^{k * N} _t, the corresponding N of every a line of P _tindividual scale factor (power control factor, power is constant), initialization input information bits stream obtains N _t* N _tdimension initialization matrix T, j (j=1,2 ..., N _t) the individual moment only has on j root antenna data, other antenna data is zero;

S2, the incoming bit stream matrix Q of log2 (NT * M) * (N-NT) is carried out to spatial modulation obtain N _t* (N-N _t) dimension spatial modulation matrix U;

The spatial modulation matrix U that S3, the initialization matrix Q that S1 is obtained and S2 obtain combines and obtains N _tthe spatial modulation signal matrix S of * N dimension, here N _tall subcarriers on the corresponding antenna of the every a line of spatial modulation signal matrix of * N dimension, then N subcarrier carried out respectively to OFDM modulation;

S4, utilize channel estimation methods to obtain channel condition information H, calculating is adapted to the preferred plan of current channel condition, it is the optimum power control factor of candidate's power control factor matrix P, and feed back to transmitting terminal by feedback channel, and then transmission matrix is carried out to equivalence, obtain the best transmission scheme of estimating channel information H;

S5, the modulation symbol under the best transmission scheme of channel condition information H described in S4 is carried out to OFDM demodulation, and spatial modulation inverse mapping, in conjunction with the maximum likelihood detection algorithm of spatial modulation system, recover original information bits stream, wherein, the x that transmits is through equivalent channel H_sub,

k wherein ^*as the optimal power controlling elements of selecting, the signal that receiving terminal receives is y, the data of the estimation obtaining with maximum likelihood detection algorithm transmitting

for: $\hat{x}=\underset{x\∈\mathrm{\Ψ}}{\arg \max }{p}_y\left(y\right|x,H\_\mathrm{sub})=\underset{x\∈\mathrm{\Ψ}}{\arg \min }{\left|\right|y-H\_\mathrm{sub}\·x\left|\right|}_F^2,,p_y\left(y\right|x,H)$ Be illustrated in channel condition information H when known, the likelihood function of the signal y that the x that transmits receives, the Ψ possible set of all transmittings of x that represents to transmit, thus obtain transmit antenna index position and transmission symbol.

Further, the method that obtains estimating channel information H described in S4 is: by the minimum Eustachian distance d between (K combination altogether) equivalent constellation point under each combination of candidate's power gating matrix relatively _min(k), choose minimum euclidean distance d _min(k) one group of maximum corresponding power control factor k ^*as best of breed.

Further, described in S4, calculate d _min(k) concrete grammar is as follows:: due to the particularity of spatial modulation system, two different x that transmit _iand x _jbe expressed as: $x_i=[0,...,x_i^m,...,0]$ With $x_j=[0,...,x_j^n,0,...,0],$ Wherein

with

represent respectively the m from constellation and n constellation point on i root and j root antenna, every of each transmission time activates day power control factor p of line options _k,l, k=1,2 ..., K; L=1,2..., N _t, and guarantee that average transmission power is constant, meet

, in spatial modulation, the minimum euclidean distance that receives equivalent constellation is:

Wherein Re{} represents that plural number gets its real part, m ₁, m ₂, m ₃as follows:

$\left\{\begin{array}{c}{m}_1={\left|h_{1,i}\right|}^2+{\left|h_{2,i}\right|}^2+...+{\left|h_{N_R,i}\right|}^2=<H_{:,i},H_{:,i}>\\ m_2={\left|h_{1,j}\right|}^2+{\left|h_{2,j}\right|}^2+...+{\left|h_{N_R,j}\right|}^2=<H_{:,j},H_{:,j}>\\ m_3=h_{1,i}{h}_{1,j}^{*}+h_{2,i}{h}_{2,j}^{*}+...+h_{N_R,i}{h}_{N_R,j}^{*}=<H_{:,i},H_{:,i}>\end{array}\right.$ H _{:, j}and H _{:, i}the j row and the i row that represent respectively channel condition information H, h _{1, j}represent the element that channel condition information H the 1st row j lists, h _{2, j}represent the element that channel condition information H the 2nd row j lists,

represent channel condition information H N _rthe element that row j lists, < c, d > represents the inner product between vectorial c and d, D ∈ C ^{m * 1}for all constellation point set under M-QAM modulation.Wherein the optimum power control factor is d in K candidate combinations _min(k) one group of maximum k ^*, that is:

k ^*＝argmax{d _min(k)},k＝1,2,...K。

The invention has the beneficial effects as follows: the receiving terminal for spatial modulation system carries out the selection of the optimum power control factor, by the non-zero sub-carriers on every antenna of transmitting terminal initialization, obtain initialization matrix, bit information on every antenna is carried out after spatial modulation and OFDM modulation, at receiving terminal, utilize candidate's power control factor matrix to carry out equivalence to modulation constellation points, and obtain thus under each group power control factor, minimum Eustachian distance between equivalence constellation point, therefrom select the maximum combination of minimum Eustachian distance as best power control factor and feed back to transmitting terminal, utilize this optimum power control factor that transmission matrix is carried out to equivalence, it is the best transmission scheme of H.Receiving terminal in conjunction with the maximum likelihood detection algorithm of spatial modulation system, is determined transmitting antenna sequence number again, and modulation symbol, further recovers transmitting information.The present invention selects the optimum power control factor by receiving terminal, and feeds back to transmitting terminal transmission channel matrix H is carried out to equivalence, has reduced the error rate of transfer of data, has further improved the performance of system.

Accompanying drawing explanation

Fig. 1 is that the present invention is for the structural representation of spatial modulation system

Embodiment

Below in conjunction with accompanying drawing, the specific embodiment of the present invention is described:

As shown in Figure 1:

S1, default candidate's power control factor matrix

at transmitting terminal, the non-zero sub-carriers on every antenna is carried out to initialization, first non-zero sub-carriers of j root antenna is positioned on j subcarrier of this antenna;

After first non-zero sub-carriers on S2, initial complete every antenna, start to carry out spatial modulation, every P=log ₂(N _tm) individual bit shines upon, front log ₂(N _t) bit selection antenna, remaining log ₂(M) bit carries out by the antenna index of selecting, being transmitted after M-PSK modulation;

S3, the non-zero sub-carriers on every antenna is carried out to differential coding, after coding, carry out OFDM modulation;

S4, receiving terminal are modulated complete constellation symbol and are carried out equivalence with candidate's power control factor matrix P described in S1, and calculate thus Euclidean distance d minimum between equivalent constellation point _min(k), relatively each combines the minimum Eustachian distance between lower equivalent constellation point, chooses one group of power control factor k of minimum Eustachian distance maximum ^*as best of breed, i.e. k ^*=argmax{d _min(k) }, k=1,2 ..., k, wherein, calculates minimum Eustachian distance d _min(k) step is as follows:

Two different x that transmit _iand x _jbe expressed as: $x_i=[0,...,x_i^m,...,0]$ With $x_j=[0,...,x_j^n,0,...,0],$ Wherein,

the m constellation point from constellation that represents i root antenna, the n constellation point from constellation that represents j root antenna, every of every time slot activates day power control factor p of line options _k,l, k=1,2 ..., K; L=1,2..., N _t, and guarantee that average transmission power is constant, meet

, in spatial modulation, the minimum euclidean distance of receiving terminal equivalence constellation is:

Wherein Re{} represents that plural number gets its real part, m ₁, m ₂, m ₃as follows:

$\left\{\begin{array}{c}{m}_1={\left|h_{1,i}\right|}^2+{\left|h_{2,i}\right|}^2+...+{\left|h_{N_R,i}\right|}^2=<H_{:,i},H_{:,i}>\\ m_2={\left|h_{1,j}\right|}^2+{\left|h_{2,j}\right|}^2+...+{\left|h_{N_R,j}\right|}^2=<H_{:,j},H_{:,j}>\\ m_3=h_{1,i}{h}_{1,j}^{*}+h_{2,i}{h}_{2,j}^{*}+...+h_{N_R,i}{h}_{N_R,j}^{*}=<H_{:,i},H_{:,i}>\end{array}\right.,$ Wherein, H _{:, j}and H _{:, i}the j row and the i row that represent respectively channel condition information H, h _{1, j}represent the element that channel condition information H the 1st row j lists, h _{2, j}represent the element that channel condition information H the 2nd row j lists,

represent channel condition information H N _rthe element that row j lists, < c, d > represents the inner product between vectorial c and d, D ∈ C ^{m * 1}for all constellation point set under M-QAM modulation;

S5, by k described in S4 ^*feed back to transmitting terminal, further transmission matrix is carried out to equivalence, with the combination of optimal power controlling elements, channel matrix H is carried out to ratio scaling, again the modulation symbol under the best transmission scheme of channel condition information H is carried out to OFDM demodulation, and spatial modulation inverse mapping, detection algorithm in conjunction with spatial modulation system estimates transmit antenna index and sends symbol, thereby recovers original information bits stream.

Below by an object lesson, illustrate:

The rate of information throughput of supposing transmitting terminal be m=3 bit/time, transmitting terminal antenna number N _t=2, receiving terminal antenna number N _rthe frame length of=2, OFDM is 16, and consideration modulation system is QPSK, and modulation constellation points set is: D={-0.7071-0.7071i, and-0.7071+0.7071i, 0.7071-0.7071i, 0.7071+0.7071i}, candidate's power control factor matrix P is as follows:

$p=\left[\begin{array}{cc}1.1547& 0.8165\\ 1& 1\\ 1.2910& 0.5774\\ 0.5774& 1.2910\\ 0.8165& 1.1547\end{array}\right]$

, for each combination of candidate's power control factor matrix P, be the every a line in P, corresponding have at most 28 different Euclidean distances, and all Euclidean distances under this combination must a corresponding minimum value.

For example,, if transmit the 3rd modulation symbol 0.7071-0.707i in modulation constellation points set on two antennas, second modulation symbol-0.7071+0.707i in the set of second antenna transmission modulation constellation points, a corresponding Euclidean distance value, for all modulation symbols, compares the value of 4 minimum euclidean distances under the combination of candidate's power control factor, chooses minimum euclidean distance d _minmaximum one group corresponding combination as the optimum power control factor of selecting.

Known channel matrix H=[0.4545-0.0070i-0.3036-0.8158i;-0.4137+0.4642i-0.5101-1.3203i] time, receiving terminal, by said method, compares the minimum Eustachian distance between the constellation point under five combinations, d _min=[1.2578 1.0892 1.0549 0.6289 0.8893], the optimum power control factor is the 1st group in candidate matrices, i.e. k ^*=[1.1547 0.8165], to transmitting terminal, obtain current optimum channel transmission matrix H_suP by the result feedback of choosing:

$\begin{array}{c}H\_\mathrm{sub}=H\&CenterDot;(I_{N_T}\&CenterDot;k^{*})\\ =\left[\begin{array}{cc}-0.4545-0.0070i& -0.3036-0.8158i\\ -0.4137+0.4642i& -0.5101-1.3203i\end{array}?\right]\&times;\left[\begin{array}{cc}1.1547& 0\\ 0& 0.8165\end{array}\right]\\ =\left[\begin{array}{cc}0.5248-0.0081i& -0.2479-0.6661i\\ -0.4777+0.5360i& -0.4165-1.0780i\end{array}\right]\end{array}$

At receiving terminal, carry out restituted signal, and estimate original transmitting information in conjunction with maximum likelihood detection mode.

From analysis above, be not difficult to know, the method for this each antenna separate modulation, in the advantage of original spatial modulation system, had both guaranteed efficiency of transmission, had further reduced again the error rate.

Existing spatial modulation system, is all the position of the modulation symbol between fixed antenna, and this is unfavorable for further reducing and disturbing.The present invention has proposed this under the constant prerequisite of the average transmission rate that guarantees system, the power having changed between antenna is controlled, and when the power control of choosing is uniformly distributed, be conducive to increase the minimum Eustachian distance between constellation point, thereby the error rate that has further reduced system, is improved performance.

Claims (3)

1. the power control factor system of selection in spatial modulation system, is characterized in that: comprise the steps:

S1, default candidate's power control factor matrix P ^{k * N} _t, the corresponding N of every a line of P _tindividual scale factor (power control factor, power is constant), initialization input information bits stream obtains N _t* N _tdimension initialization matrix T, j (j=1,2 ..., N _t) the individual moment only has on j root antenna data, other antenna data is zero;

S2, the incoming bit stream matrix Q of log2 (NT * M) * (N-NT) is carried out to spatial modulation obtain N _t* (N-N _t) dimension spatial modulation matrix U;

The spatial modulation matrix U that S3, the initialization matrix Q that S1 is obtained and S2 obtain combines and obtains N _tthe spatial modulation signal matrix S of * N dimension, here N _tall subcarriers on the corresponding antenna of the every a line of spatial modulation signal matrix of * N dimension, then N subcarrier carried out respectively to OFDM modulation;

S4, utilize channel estimation methods to obtain channel condition information H, calculating is adapted to the preferred plan of current channel condition, it is the optimum power control factor of candidate's power control factor matrix P, and feed back to transmitting terminal by feedback channel, and then transmission matrix is carried out to equivalence, obtain the best transmission scheme of estimating channel information H;

S5, the modulation symbol under the best transmission scheme of channel condition information H described in S4 is carried out to OFDM demodulation, and spatial modulation inverse mapping, in conjunction with the maximum likelihood detection algorithm of spatial modulation system, recover original information bits stream, wherein, the x that transmits is through equivalent channel H_sub,

k wherein ^*as the optimal power controlling elements of selecting, the signal that receiving terminal receives is y, the data of the estimation obtaining with maximum likelihood detection algorithm transmitting for: $\hat{x}=\underset{x\&Element;\mathrm{\&Psi;}}{\arg \max }{p}_y\left(y\right|x,H\_\mathrm{sub})=\underset{x\&Element;\mathrm{\&Psi;}}{\arg \min }{\left|\right|y-H\_\mathrm{sub}\&CenterDot;x\left|\right|}_F^2,,p_y\left(y\right|x,H)$ Be illustrated in channel condition information H when known, the likelihood function of the signal y that the x that transmits receives, the Ψ possible set of all transmittings of x that represents to transmit, thus obtain transmit antenna index position and transmission symbol.

2. the power control factor system of selection in a kind of spatial modulation system according to claim 1, is characterized in that: the method that obtains estimating channel information H described in S4 is: by comparing the minimum Eustachian distance d between (K combination altogether) equivalent constellation point under each combination of candidate's power gating matrix _min(k), choose minimum euclidean distance d _min(k) one group of maximum corresponding power control factor k ^*as best of breed.

3. the power control factor system of selection in a kind of spatial modulation system according to claim 1, is characterized in that: described in S4, calculate d _min(k) concrete grammar is as follows:: due to the particularity of spatial modulation system, two different x that transmit _iand x _jbe expressed as: $x_i=[0,...,x_i^m,...,0]$ With $x_j=[0,...,x_j^n,0,...,0],$ Wherein

with

represent respectively the m from constellation and n constellation point on i root and j root antenna, every of each transmission time activates day power control factor p of line options _k,l, k=1,2 ..., K; L=1,2..., N _t, and guarantee that average transmission power is constant, meet

, in spatial modulation, the minimum euclidean distance that receives equivalent constellation is:

Wherein Re{} represents that plural number gets its real part, m ₁, m ₂, m ₃as follows:

$\left\{\begin{array}{c}{m}_1={\left|h_{1,i}\right|}^2+{\left|h_{2,i}\right|}^2+...+{\left|h_{N_R,i}\right|}^2=<H_{:,i},H_{:,i}>\\ m_2={\left|h_{1,j}\right|}^2+{\left|h_{2,j}\right|}^2+...+{\left|h_{N_R,j}\right|}^2=<H_{:,j},H_{:,j}>\\ m_3=h_{1,i}{h}_{1,j}^{*}+h_{2,i}{h}_{2,j}^{*}+...+h_{N_R,i}{h}_{N_R,j}^{*}=<H_{:,i},H_{:,i}>\end{array}\right.$ H _{:, j}and H _{:, i}the j row and the i row that represent respectively channel condition information H, h _{1, j}represent the element that channel condition information H the 1st row j lists, h _{2, j}represent the element that channel condition information H the 2nd row j lists,

represent channel condition information H N _rthe element that row j lists, < c, d > represents the inner product between vectorial c and d, D ∈ C ^{m * 1}for all constellation point set under M-QAM modulation, wherein the optimum power control factor is d in K candidate combinations _min(k) one group of maximum k ^*, that is:

k ^*＝argmax{d _min(k)},k＝1,2,...K。