Lte Link Receiver Interference Elimination Technology Research

There is interference from other users with the same frequency when the desireduser transmits data to the base station in the LTE uplink. The two users with the samefrequency constitute a virtual MIMO system when the configuration is single-antennafor users and multi-antenna for base station. There is interference between different laysin MIMO system. Also there is interference between different users in virtual MIMOsystem. In this thesis, the iterative soft interference cancellation detection algorithm andinterference rejection combing (IRC) algorithm are studied to improve the performanceof the system.Firstly, the virtual MIMO structure is analyzed. And the V-BLAST detectionalgorithms are studied, such as the zero-forcing (ZF) detection algorithm, the minimummean square error (MMSE) detection algorithm based on linear detection method, theserial interference cancellation detection algorithm and the parallel interferencecancellation detection algorithm based on the feedback method. Then, the concepts ofsoft decoding and soft information are intruced, and the soft interference cancellationMMSE-SIC structure and interference cancellation structure based on received data areanalyzed.Regular receive combing algorithms including the selection combining method, theequal gain combining method, and the maximum ratio combining method (MRC) arestudied in the thesis. Then, the interference rejection combining (IRC) method isintruced, and the differences between MRC and IRC are compared. For the problem ofinterference estimation in the IRC algorithm, algorithms based on the received signaland based on pilot are analyzed.Finally, the performances of different methods are compared by simulations. It isfound that the detection algorithm based on the feedback interference cancellation hasbetter performance than the linear detection algorithm. The interference cancellationdetection with the iterative soft information has better performance than the detectionwith hard decision, and the performance of the detection with soft information will beimproved correspondingly with the increase in the number of iterations. By the simulations of the two interference covariance estimation methods, it isfound that the pilot-based estimation method is more accurate, and has betterperformance. In the LTE uplink, the method of combing IRC with SIC is better thanusing IRC technique separately, and the performance will be improved with the increasein the number of iterations.