CN103763072A - MIMO link self-adaptive transmission method - Google Patents

Abstract

The invention discloses a link self-adaptive transmission method suitable for iteration receiving under limited character input signals. Firstly, under all modulation code schemes, the relation of handling capacity and the frame error rate under the iteration receiving condition is obtained, and the threshold value of handling capacity is calculated according to the requirement of the frame error rate; secondly, the average speed of different codebooks under Gaussian input signals and multiple channel samples is calculated, and then a modulation code scheme is preliminarily selected when the requirement of the frame error rate is met and the handling capacity is maximized; finally, the average mutual information of all precoding codons under limited character input signals and multiple channel samples is calculated, and precoding codons and modulation code schemes meeting the requirement of the frame error rate are selected according to the average mutual information. The link self-adaptive transmission method is suitable for MIMO link self-adaptive control under the iteration receiving condition, calculated amount and transmission delay are lowered, and the method is easy to achieve.

Description

A kind of MIMO link self-adaption transmission method

Technical field

The present invention relates to the link self-adaption transmission method under a kind of limited character input signal, especially relate to the link self-adaption transmission method that is suitable for iterative receiver in multiple input multiple output (MIMO) wireless communication system under limited character input signal.

Background technology

For meeting future mobile communication system to the demand of high data rate more, mimo wireless communication system improves and has strengthened air interface technologies.In actual wireless propagation environment, along with subscriber equipment (UE, User Equipment) movement, UE and base station (BS, Base Station) channel between may experience different types, thereby has caused the decline of open-loop transmission systematic function, therefore, in mimo wireless communication system, adopt closed loop transmission technology to be adaptive to the variation of channel circumstance.

Under mimo wireless communication system closed loop transmission pattern and limited character input signal, UE realizes link circuit self-adapting by parameters such as feeding back precoding matrix, modulation system and code rates and transmits.Optimum link adaptive transmission method, be characterized in the feedback parameter of UE to complete by Syndicating search: calculate the optimum pre-coding matrix under each modulation system, the maximization equivalent channel mutual information of take is criterion, in the system of assurance frame error rate, be no more than under the prerequisite of default thresholding, select optimum modulation system and corresponding code rate thereof.Generally speaking, under each modulation system and each code rate, the mutual information of restraining by the method acquisition iterative receiver of emulation contrasts figure with frame error rate, according to frame error rate, require to obtain mutual information thresholding.Iterative receiver mutual information just can guarantee that when being not less than mutual information thresholding frame error rate is no more than default thresholding.

Iterative receiver is raising wireless communication system receptivity, realizes the effective ways that approach the transmission of channel mutual information.In conjunction with take the precoding technique that channel mutual information maximization is criterion, the achievable rate of iterative receiver approaches channel maximum mutual information.Utilize this feature, the mutual information under limited character input signal just can be used as the achievable rate of iterative receiver.According to gained mutual information, can be in link circuit self-adapting transmission technology selecting modulation mode and code rate.And the amount of calculation of optimum link adaptive approach is very large, under limited character input signal, the traversal search of pre-coding matrix increases computing time, and the delay causing is unfavorable to link circuit self-adapting transmission.The present invention provides a kind of efficient chain circuit self-adaptive method, and it is more much lower than the computation complexity of optimum link adaptive approach, and spectrum efficiency is approached the spectrum efficiency of optimum link adaptive approach.

Summary of the invention

Goal of the invention: for problems of the prior art and deficiency, the invention provides the link self-adaption transmission method that is suitable for iterative receiver under a kind of limited character input signal, the method is utilized and is tentatively determined modulation system with speed expression formula under Gauss's input signal, carry out on this basis the selection of the search of optimal transmission pre-encoding codeword and code modulating method, the method proposing has reduced amount of calculation and propagation delay time, and spectrum efficiency is approached the spectrum efficiency of optimum link adaptive transmission method.

Technical scheme: a kind of MIMO link self-adaption transmission method, comprises the steps:

Step 1, under each Modulation and Coding Scheme, the method by emulation obtains throughput and the frame error rate relation of iterative receiver convergence, according to frame error rate requirement calculate throughput threshold value;

Step 2, employing Gauss input signal hypothesis, calculate the average and speed of different code books under a plurality of channel samples;

Step 3, take maximize throughput as criterion initial option Modulation and Coding Scheme meeting when frame error rate requires;

Step 4, calculate and under limited character input signal, use the Average Mutual of each pre-encoding codeword under a plurality of channel samples.

Step 5, according to Average Mutual, select to meet pre-encoding codeword and the Modulation and Coding Scheme that frame error rate requires.

In described link self-adaption transmission method step 3, utilize to obtain the preliminary scope of limited input signal modulated mode with speed expression formula under Gauss's input signal.

In described link self-adaption transmission method step 4, after preliminary selected modulation system, utilize the mutual information computing formula under limited character input signal to calculate the Average Mutual of each pre-encoding codeword under selected modulation system and a plurality of channel samples.

In described link self-adaption transmission method step 5, select to make the maximized pre-encoding codeword of Average Mutual, and utilize throughput and frame error rate relation, select to meet under this pre-encoding codeword the Modulation and Coding Scheme of frame error rate requirement.

Beneficial effect: compared with prior art, the link self-adaption transmission method under limited character input signal provided by the invention, has the following advantages:

1) pre-coding matrix of design can be applicable to the transfer of data between a plurality of channel samples, has good versatility and practicality.

2) link self-adaption transmission method proposing has reduced operand and memory space in original system resource, and has reduced propagation delay time, is easy to realize in practical communication system.

3) link self-adaption transmission method proposing is suitable for receiving terminal and adopts iterative receiver, approaches optimum link adaptive transmission method in throughput, has efficient efficiency of transmission.

Accompanying drawing explanation

Fig. 1 is MIMO transmission system block diagram;

Fig. 2 is link circuit self-adapting structured flowchart.

Embodiment

Below in conjunction with specific embodiment, further illustrate the present invention, should understand these embodiment is only not used in and limits the scope of the invention for the present invention is described, after having read the present invention, those skilled in the art all fall within the application's claims limited range to the modification of the various equivalent form of values of the present invention.

Fig. 1 has provided MIMO transmission system block diagram.Consider that a number of transmit antennas is N _t, reception antenna number is N _rlink, signal input/output relation can be expressed as:

y _n＝H _nWx _n+z _n,n＝1,2,...,N

Wherein, N represents channel samples number,

be n receiving symbol vector;

be n channel matrix sample; x _nbe n and send symbolic vector, have unit energy, the modulation symbol generating after its each element coded modulation, takes from modulation symbol collection; Suppose total K kind modulation symbol collection, large I sequence is: M ₁< M ₂< ... < M _k; z _nthat average is zero, variance is σ ²additivity white complex gaussian noise; W is pre-coding matrix, from codebook set

middle generation.

Fig. 2 is link circuit self-adapting structured flowchart of the present invention.

Step 1, under each Modulation and Coding Scheme, the method by emulation obtains throughput and the frame error rate relation in iterative receiver situation, according to frame error rate requirement calculate throughput threshold value.

At additive white Gaussian noise channel, by the method for demodulator and decoder emulation being obtained to the functional relation of frame error rate and throughput of system under various Modulation and Coding Scheme

FER＝LUT(R,I _MCS)

In formula, R represents throughput of system; I _mCS∈ 1,2 ..., N _mCS, N _mCSbe the total number of Modulation and Coding Scheme, function LUT can be stored in look-up table.Thus, computation index is I _mCSmodulation and Coding Scheme meet link error code word rate and be less than or equal to FER ₀the throughput threshold value requiring:

$R_{\mathrm{th},{\mathrm{FER}}_0}\left(I_{\mathrm{MCS}}\right)={\mathrm{LUT}}^{-1}(\mathrm{FER}={\mathrm{FER}}_0,I_{\mathrm{MCS}})$

Step 2, for different code books, calculate the average and speed of the system of a plurality of channel samples under Gauss's input signal hypothesis.

1. for code book W _twith channel samples H _n, calculate system and speed under Gauss's input signal hypothesis:

$R_{\mathrm{sum}}(n,t)={\log }_2\det (I_{N_T}+{W_t}^H{H}_n^H{H}_n{W}_t)$

Wherein:

for N _t* N _tidentity matrix.

2. calculate code book W _taverage and speed for N channel samples:

$R_{\mathrm{sum},\mathrm{avg}}\left(t\right)=\frac{1}{N}\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}{R}_{\mathrm{sum}}(n,t)$

3. calculate the maximum of average and speed

$R_{\mathrm{sum},\mathrm{avg}}^{\mathrm{final}}=\underset{t\&Element;[\mathrm{1,2},...,T]}{\max }{R}_{\mathrm{sum},\mathrm{avg}}\left(t\right)$

Step 3, take maximize throughput as criterion initial option modulation system meeting when frame error rate requires.Particularly, according to frame error rate, be less than or equal to FER ₀and the criterion selecting modulation mode of maximize throughput:

$m^{*}\text{=arg}\underset{I_{\mathrm{MCS}}\&Element;\{\mathrm{1,2},...,N_{\mathrm{MCS}}\}}{\max }\left\{R_{\mathrm{th},{\mathrm{FER}}_0}\left(I_{\mathrm{MCS}}\right)\right|R_{\mathrm{sum},\mathrm{avg}}^{\mathrm{final}}\&GreaterEqual;R_{\mathrm{th},{\mathrm{FER}}_0}\left(I_{\mathrm{MCS}}\right)\}$

Consider because the selection under Gauss's input signal hypothesis may bring performance error, tentatively by m ^*-1 and m ^*two kinds of modulation systems are as possible modulation system under limited character input signal.

Step 4, at codebook set

in determine optimal transmission pre-encoding codeword, and calculate the Average Mutual of this pre-encoding codeword under a plurality of channel samples.

1. for code book W _t, obtain equivalent channel

t=1,2 ..., T.

2. for code book W _twith two kinds of modulation system m ^*-1 and m ^*, calculate respectively the Average Mutual of N channel samples under limited character input hypothesis:

$I_{\mathrm{finite},m^{*}-1,t}(x,y)=N_T{\log }_2{M}_{m^{*}-1}-\frac{1}{{\mathrm{NN}}_{m^{*}-1}^{N_T}}\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}\underset{a=1}{\overset{M_{m^{*}-1}^{N_T}}{\mathrm{\&Sigma;}}}{E}_z\left\{{\log }_2\underset{b=1}{\overset{M_{m^{*}-1}^{N_T}}{\mathrm{\&Sigma;}}}{e}^{{-d}_{a,b,n,m^{*}-1,t}}\right\}$

$I_{\mathrm{finite},m^{*},t}(x,y)=N_T{\log }_2{M}_{m^{*}}-\frac{1}{{\mathrm{NN}}_{m^{*}}^{N_T}}\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}\underset{a=1}{\overset{M_{m^{*}}^{N_T}}{\mathrm{\&Sigma;}}}{E}_z\left\{{\log }_2\underset{b=1}{\overset{M_{m^{*}}^{N_T}}{\mathrm{\&Sigma;}}}{e}^{{-d}_{a,b,n,m^{*},t}}\right\}$

Wherein $d_{a,b,n,m,t}={\mathrm{\&sigma;}}^{-2}({\left|\right|{\tilde{H}}_{n,t}(x_{n,a,m}-x_{n,b,m})+z_n\left|\right|}^2-{\left|\right|z_n\left|\right|}^2),$ X _{n, a, m}expression is by M _mthe constellation set x that unit's modulation signal forms _nin a element.

Step 5, according to Average Mutual, select to meet pre-encoding codeword and the Modulation and Coding Scheme that frame error rate requires.

1. calculate maximum and the optimum code word of the lower Average Mutual of limited character input signal hypothesis:

$\begin{array}{c}{I}_{\mathrm{finite},\mathrm{final}}(x,y)=\underset{t\&Element;[\mathrm{1,2},...,T]}{\max }\{I_{m^{*}-1,t}(x,y),I_{m^{*},t}(x,y)\}\\ t^{*}\text{=arg}\underset{t\&Element;[\mathrm{1,2},...,T]}{\max }\{I_{m^{*}-1,t}(x,y),I_{m^{*},t}(x,y)\}\end{array}$

2. for optimum code word, according to error code word rate, be less than or equal to FER ₀and the criterion of maximize throughput is selected modulation coding mode:

$\{m^{*},c^{*}\}=\arg \underset{I_{\mathrm{MCS}}\&Element;\{\mathrm{1,2},...,N_{\mathrm{MCS}}\}}{\max }\left\{R_{\mathrm{th},{\mathrm{FER}}_0}\left(I_{\mathrm{MCS}}\right)\right|I_{\mathrm{finite},\mathrm{final}}(x,y)\&GreaterEqual;R_{\mathrm{th},{\mathrm{FER}}_0}\left(I_{\mathrm{MCS}}\right)\}$

Claims (4)

1. a MIMO link self-adaption transmission method, is characterized in that, comprises the steps:

Step 1, under each Modulation and Coding Scheme, the method by emulation obtains throughput and the frame error rate relation of iterative receiver convergence, according to frame error rate requirement calculate throughput threshold value;

Step 2, employing Gauss input signal hypothesis, calculate the average and speed of different code books under a plurality of channel samples;

Step 3, take maximize throughput as criterion initial option Modulation and Coding Scheme meeting when frame error rate requires;

Step 4, calculate and under limited character input signal, use the Average Mutual of each pre-encoding codeword under a plurality of channel samples;

Step 5, according to Average Mutual, select to meet pre-encoding codeword and the Modulation and Coding Scheme that frame error rate requires.

2. MIMO link self-adaption transmission method according to claim 1, is characterized in that, in described step 3, utilizes to obtain the preliminary scope of limited input signal modulated mode with speed expression formula under Gauss's input signal.

3. MIMO link self-adaption transmission method according to claim 1, it is characterized in that, in described step 4, after preliminary selected modulation system, utilize the mutual information computing formula under limited character input signal to calculate the Average Mutual of each pre-encoding codeword under selected modulation system and a plurality of channel samples.

4. MIMO link self-adaption transmission method according to claim 1, it is characterized in that, in described step 5, select to make the maximized pre-encoding codeword of Average Mutual, and utilize throughput and frame error rate relation, select to meet under this pre-encoding codeword the Modulation and Coding Scheme of frame error rate requirement.

Images