CN105680984A - Alternating group iterative detection method for broadband multiuser MIMO-OFDM (Multiple Input Multiple Output-Orthogonal Frequency Division Multiplexing) system - Google Patents

Abstract

The invention discloses an alternating group iterative detection method for a broadband multiuser MIMO-OFDM (Multiple Input Multiple Output-Orthogonal Frequency Division Multiplexing) system. The method comprises the following steps: averagely dividing subcarriers into I groups on a base station; performing intra-group detection on each group of signals received by the base station through a positive semi-definite relaxation detection algorithm; calculating inter-group interference by using the detected signals; subtracting the inter-group interference from the signals received by the base station to form new received signals; returning the signals to an input end of a detector to perform next detection; and repeating iteration in sequence till initially-set iteration times are reached.

Description

A kind of packet alternating iteration detection method of broadband multiuser MIMO-OFDM system

Technical field

The present invention relates to wireless communication field, particularly to the packet alternating iteration detection method of a kind of broadband multiuser MIMO-OFDM system.

Background technology

In MIMO-OFDM system, receiving terminal detection algorithm can remove multi-user, multiple antennas and inter-sub-carrier interference, thus recovering primary signal, therefore the performance of detection algorithm is to weigh a major criterion of systematic function. Compared with linear detection algorithm, many nonlinear detection algorithms are obtained in that more excellent detection performance. Maximum likelihood multiuser detection algorithm is obtained in that the performance of optimum, but due to the method that have employed traversal, its computation complexity is higher, and in MIMO-OFDM system can the sharp increase along with the growth of antenna number and sub-carrier number, this makes it very infeasible in the actual environment of multi-user's load. A kind of low complex degree that globular decoding is maximum likelihood algorithm realizes, and it is by to receive signal phasor for the search of point in the ball of the centre of sphere, finally converging to maximum likelihood solution. In addition maximum likelihood problem is changed into a convex optimization problem that can solve in polynomial time by extending feasible zone, relaxed constraints condition by positive semidefinite relaxed algorithm. The Interference Cancellation detection algorithm complexity of many suboptimums is lower than Maximum Likelihood Detection simultaneously, but it also is able to obtain good performance, such as based on the multiuser detection algorithm of counteracting serial interference, parallel interference cancellation algorithm, both the above algorithm is different from linear detection algorithm, they are not followed and first detect the order demodulated afterwards, but detection and demodulating process alternating iteration are carried out, namely signal back detection obtained is demodulated, and demodulation result feeds back to the input of detector for next iteration. PIC and SIC detector all removes inter-user interference at each detection-phase, and previous step detection performance will influence whether the detection performance in this stage. But, no matter it is linear algorithm or nonlinear algorithm, in MIMO-OFDM system, along with the increase of system antenna number Yu sub-carrier number, channel matrix dimension increases therewith so that the complexity of detection algorithm steeply rises.

Accordingly, it would be desirable to a kind of new method solves the problem that multi-user MIMO-OFDM system detection algorithm complexity is higher.

Summary of the invention

The purpose of the present invention aims to provide the packet alternating iteration detection method of a kind of broadband multiuser MIMO-OFDM up-link, to obtain the good compromise of detection performance and algorithm complex.

The present invention solves above-mentioned technical problem by the following technical solutions:

Assuming iteration M time, when iterating to the t time (t≤M), i-th group, base station receives signal and is expressed asRepeat the steps of until t > M. The transmitting signal that often group detects is obtained first by positive semidefinite slack detectorInterference and noise between group are all used as noise, then i-th group of signal that base station receives isWhereinDetected by positive semidefinite relaxed algorithm and often to organizeSecond step, utilizes the often group detectedCalculate and disturb between all groups, from often organizing reception signalDisturb between middle elimination group, obtain newNamely3rd step, by often groupUpdate correspondenceNamelyFinally, t=t+1, iteration are made; Until t > M, stop iteration.

Wherein, G_iiIt is the equivalent channel matrix that i-th group of signal is corresponding, G_ii'Be i-th ' equivalent channel matrix that group signal is corresponding to the interference of i-th group of signal,It is i-th group and launches signal,Be i-th ' group launches signal,It is i-th group of noise received.

The present invention adopts above technical scheme compared with prior art, has following technical effect that

A () adopts high performance positive semidefinite Relaxation detecting algorithm antagonism group internal interference, it is possible to obtain accurate testing result, and reduce the computation complexity that positive semidefinite is lax due to packet;

B () method by parallel interference canceller, disturbs between continuous reduction group in each iterative process, along with the increase of iterations, disturbs and continue to be reduced between group, thus improving detection performance further.

Aspect and advantage that the present invention adds will part provide in the following description, and these will become apparent from the description below, or is recognized by the practice of the present invention.

Accompanying drawing explanation

Fig. 1 is according to one system schematic of the present invention.

Fig. 2 is the flow chart of packet alternating iteration detection algorithm.

Detailed description of the invention

Below in conjunction with the drawings and specific embodiments, it is further elucidated with the present invention, it should be understood that these embodiments are merely to illustrate the present invention rather than restriction the scope of the present invention, after having read the present invention, the amendment of the various equivalent form of values of the present invention is all fallen within the application claims limited range by those skilled in the art.

The packet alternating iteration detection method of a kind of broadband multiuser MIMO-OFDM system of the present invention includes: utilize the thought of subcarrier grouping to reduce algorithm complex, utilizes the positive semidefinite method of Parallel Interference Cancellation between detection and group that relaxes in group to obtain the good compromise of performance and complexity simultaneously.

Preferably, the thought according to packet, first the signal that base station receives is divided into the I group that sub-carrier number is equal, then carries out packet alternating iteration detection. It comprises the following steps that.

Assuming iteration M time, as iteration the t time (t≤M), i-th group, base station receives signal and is expressed asRepeat the steps of, until t > M then stops iteration.

Step 1), use positive semidefinite slack detector to obtain the transmitting signal that often group detectsAll be used as noise by interference and noise between group, then i-th group of signal that base station receives isWhereinDetected by Sphere Decoding Algorithm and often to organize

Wherein, G_iiIt is the equivalent channel matrix that i-th group of signal is corresponding, G_ii'Be i-th ' equivalent channel matrix that group signal is corresponding to the interference of i-th group of signal,It is i-th group and launches signal,Be i-th ' group launches signal,It is i-th group of noise received.

Step 2), interference between utilizing the often group signal detected to calculate all groups, from often organizing reception signalDisturb between middle elimination group, obtain newNamely ${\tilde{y}}_i^t=y_i^t-\underset{i^{\′}\≠i}{\overset{I}{\underset{i^{\′}=1}{\mathrm{\Σ}}}}{G}_{{\mathrm{ii}}^{\′}}{s}_{i^{\′}}^t;$

Step 3), by often groupUpdate correspondenceNamely

Step 4), make t=t+1, iteration step 1), 2) and 3).

As it is shown in figure 1, the signal received base station is divided into the I group that sub-carrier number is equal, answer the detection signal of user in pairs to often organizing the signals revivification that obtains after signal carries out packet alternating iteration detection.

As shown in Figure 2, in group, between detection and group, interference elimination alternating iteration carries out, carry out organizing interior detection first with positive semidefinite Relaxation detecting algorithm, utilize interference between the signal calculating group detected, and in base station received signal, deduct the reception signal that between this group, interference formation is new, then it is repeated in iteration, along with the increase of iterations, disturb between group and be constantly reduced, improve constantly detection performance.

Present invention employs the thought of subcarrier grouping, the often group signal received base station first with positive semidefinite Relaxation detecting algorithm carries out organizing interior detection, utilize interference between the signal calculating group detected, and in base station received signal, deduct the reception signal that between this group, interference formation is new, the input that new reception signal returns to detector is detected next time, then it is repeated in iteration, until reaching the iterations just set, increase along with iterations, between group, interference is gradually reduced, thus obtaining the good compromise of performance and complexity.

Claims (3)

1. the packet alternating iteration detection method of a broadband multiuser MIMO-OFDM system, it is characterized in that: first base station received signal is grouped, utilize the detection method of alternating iteration when detecting signal, along with the increase of iterations, improve constantly detection performance.

2. broadband multiuser MIMO-OFDM nested design alternating iteration detection method according to claim 1, it is characterised in that: specifically comprising the following steps that of packet alternating iteration detection method

Assume iteration M time, as iteration the t time (t≤M), repeat:

Step 1), use positive semidefinite slack detector to obtain the transmitting signal that often group detects, namely interference and noise between group are all used as noise, are detected the detection signal often organized by Sphere Decoding Algorithm;

Step 2), interference between utilizing the often group signal detected to calculate all groups, then from often organizing interference between elimination group reception signal, obtain new reception signal;

Step 3), the new signal that receives obtained by often group replaces reception signal originally;

Step 4), make t=t+1, iteration step 1), 2) and 3);

Until t > M, stop iteration.

3. broadband multiuser MIMO-OFDM nested design alternating iteration detection method according to claim 2, it is characterized in that: the frequency-region signal that MIMO-OFDM system base-station receives is divided into the I group that sub-carrier number is identical, positive semidefinite Relaxation detecting algorithm is adopted to detect to often organizing signal, disturb and adopt interference between the method elimination group of Parallel Interference Cancellation between calculating group subsequently, thus constituting packet alternating iteration detection structure.