CN104506478A - Time-variant multi-user MIMO-OFDM uplink linear iteration detector based on grouping - Google Patents

Abstract

The invention discloses a time-varying multi-user MIMO-OFDM uplink group-based linear iterative detector. For the MIMO-OFDM system uplink, when the base station detects the signal, the received signal is first divided into I with the same number of subcarriers. group, and then when detecting each group of signals, the interference of the detected previous group of signals to the group is eliminated. The present invention first uses the minimum mean square error detection algorithm for each group of signals after grouping to detect within the group, and then uses the algorithm of serial interference cancellation to detect the previous group of signals to the group of signals when detecting each group of signals Interference cancellation. The detection algorithm after interference cancellation can improve the detection performance of each group, thereby improving the performance of the overall detector.

Description

Time-varying multiuser MIMO-OFDM uplink packet-based linear iterative detector

technical field

The invention relates to the field of wireless communication, in particular to a group-based linear iterative detector for a time-varying multi-user MIMO-OFDM uplink.

Background technique

Signal detection is a key technology to realize wireless communication system. Whether the transmitted signal can be detected correctly at the receiving end is an important index to measure the performance of a wireless communication system. The detection algorithm can be equivalent to beamforming at the receiving end, which can reduce the interference between multiple antennas and multiple users, thereby restoring the original signal. Detection algorithms can be divided into linear detection algorithms and nonlinear detection algorithms. The more classic linear detection methods include linear least squares (LS), minimum mean square error (MMSE), etc. These two detectors can be applied to MIMO and MIMO -In the OFDM system, although the calculation process of the two is simple, the performance is very limited, and as the number of antennas in the MIMO system increases or the number of subcarriers in the OFDM system increases, the computational complexity of the two linear detection algorithms will increase accordingly. In contrast, the idea of interference cancellation detection can achieve superior performance, such as serial interference cancellation (SIC) multi-user detection algorithm, parallel interference cancellation (PIC) detection algorithm, etc., they do not follow the order of first detection and then demodulation , but the detection and demodulation process is iteratively carried out alternately, that is, the signal obtained by the previous step is demodulated, and the demodulation result is fed back to the input terminal of the detector for the next detection, so the detection performance of the previous step will affect Detection performance up to the current stage. However, in the MIMO-OFDM system, as the number of antennas and the total number of subcarriers increase, the dimension of the channel matrix increases, which makes the complexity of the detection algorithm rise sharply, and the complexity of both the linear detection algorithm and the interference cancellation algorithm will increase. .

Therefore, a new approach is needed to solve the signal detection problem.

Contents of the invention

The purpose of the present invention is to provide a time-varying multi-user MIMO-OFDM uplink packet-based linear iterative detector to obtain a good compromise between detector performance and complexity.

The present invention adopts the following technical solutions for solving the problems of the technologies described above:

First, the frequency domain signals received by the base station of the MIMO-OFDM system are divided into I groups with the same number of subcarriers, according to Calculate the within-group minimum mean square error detector for each group, and initialize y ₀ =y, The number of initialization cycles n=1. Then calculate ||G _ii || ² , and sort from large to small, and record the group label set φ of the sorting result. This step aims to preferentially detect groups with better channel conditions. The third step is to detect the φ(n)th group of signals, namely When detecting the φ(n+1)th received signal, the interference of the φ(n)th group signal is subtracted, that is, Let n=n+1. Finally, the above detection steps are repeated until all signals are detected.

Compared with the prior art, the present invention adopts the above technical scheme and has the following technical effects:

The time-varying multi-user MIMO-OFDM uplink packet-based linear iterative detector used, because it uses the detection idea of serial interference cancellation, the interference of the previous group of signals detected before each group of signals is detected , so compared with the linear detection algorithm, its detection performance has been improved. At the same time, in view of the high complexity of the broadband system, the idea of group detection for the received signal is proposed, which effectively reduces the detection complexity and achieves a good compromise between detection performance and complexity.

Additional aspects and advantages of the invention will be set forth in part in the description which follows, and will become apparent from the description, or may be learned by practice of the invention.

Description of drawings

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

Figure 2 is a flowchart of the serial interference cancellation algorithm.

Detailed ways

Below in conjunction with accompanying drawing and specific embodiment, further illustrate the present invention, should be understood that these embodiments are only for illustrating the present invention and are not intended to limit the scope of the present invention, after having read the present invention, those skilled in the art will understand various aspects of the present invention Modifications in equivalent forms all fall within the scope defined by the appended claims of this application.

A time-varying multi-user MIMO-OFDM uplink linear iterative detector based on grouping of the present invention includes: effectively reducing the complexity by using the idea of grouping, and improving the performance of the detector by using the detection method of serial interference cancellation.

As a preferred solution, according to the idea of grouping, the frequency domain signals received by the MIMO-OFDM system base station are first divided into I groups with the same number of subcarriers.

As a preferred option, according to Calculate the within-group minimum mean square error detector for each group, and initialize y ₀ =y, The number of initialization cycles n=1. Then calculate ||G _ii || ² , and sort from large to small, and record the group label set φ of the sorting result. This step aims to preferentially detect groups with better channel conditions. The third step is to detect the φ(n)th group of signals, namely When detecting the φ(n+1)th received signal, the interference of the φ(n)th group signal is subtracted, that is, Let n=n+1. Finally, the above detection steps are repeated until all signals are detected.

As shown in Figure 1, after the frequency domain signals received by the MIMO-OFDM system base station are divided into I groups with the same number of subcarriers, each group of signals is detected by the minimum mean square error within the group, and then serial interference cancellation is used The method restores the obtained signal to the original signal corresponding to the user.

As shown in Figure 2, the detection and demodulation process is carried out alternately and iteratively, that is, the signal detected in the previous step is demodulated, and the demodulation result is fed back to the input terminal of the detector for the next detection. When detecting this signal The interference of the previous group of signals is subtracted, which improves the performance of the detector.

The present invention adopts the detection idea of serial interference cancellation, alternately and iteratively performs the detection and demodulation process, that is, demodulates the signal obtained in the previous step detection, and feeds back the demodulation result to the input terminal of the detector for use in the next detection. It can effectively reduce the interference and improve the performance of the detector. Since the overall subcarrier detection method has high complexity, the present invention introduces the idea of subcarrier group detection to obtain a good compromise between detection performance and algorithm complexity.

Claims (3)

1. one kind time become multi-user MIMO-OFDM up link packet-based linear iteraction detector, it is characterized in that: first base station received signal is divided into groups, adopt when detecting and often organizing signal in minimum mean-squared error algorithm algorithm suppression group and disturb, the upper one group of signal detected is eliminated the interference of this group by recycling counteracting serial interference method, the detection perform often organized can be improved, thus improve the performance of whole detection device.

2. become multi-user MIMO-OFDM up link packet-based linear iteraction detector time according to claim 1, it is characterized in that: the concrete steps that the counteracting serial interference based on subcarrier grouping detects are as follows:

Step 1), first the signal received is divided into the identical I group of sub-carrier number, according to mean square error detector is minimized in the group that calculating is often organized, and initialization y ₀=y, loop initialization frequency n=1.

Wherein, G _iibe the equivalent channel matrix that i-th group of signal is corresponding, G _ii'be i-th ' group signal is to the equivalent channel matrix of the interference correspondence of i-th group of signal.W _ibe the monitoring matrix of i-th group, y is the signal received, σ ²for noise variance.

Step 2), calculate || G _ii|| ², and sort from big to small, and the deck label set φ of record ordering result, this step is intended to preferentially detect good group of channel conditions.

Step 3), detect φ (n) and organize signal, namely

Step 4), in φ (n+1) Received signal strength, deduct φ (n) organize the interference of signal to it, even

$y_{\mathrm{\φ}(n+1)}=y_{\mathrm{\φ}\left(n\right)}-G_{\mathrm{\φ}(n+1)\mathrm{\φ}\left(n\right)}{\hat{s}}_{\mathrm{\φ}\left(n\right)},$ Make n=n+1.

Step 5), repeat step 3 and 4, until n=I, stop circulation.

3. become multi-user MIMO-OFDM up link packet-based linear iteraction detector time according to claim 1, 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.