Research On Interference Mitigation And Performance Enhancement In MIMO System

Multi-input multi-output （MIMO） technology can improve spectrum efficiency, servicequality and subscribers performance without extra transmission power or system bandwidth. Ithas become a core support technology of the new network system. The poor performance of celledge subscribers has been a technical bottleneck of the cellular system. The related techniques ofthe interference suppression and performance enhancement can greatly improve cell edgesubscriber performance in MIMO system, and have attracted scholars’ attention, at home andabroad. Based on all of this, the thesis lucubrates on interference suppression and packetscheduling in uncooperative system, cooperative system and cooperative system with limitedfeedback, main work as follows:1. This paper derived subscribers data rate expression in MIMO system, and analyzed theinfluence of inter-cell interference（ICI）and frequency resource scheduling on subscribers datarate, and expounded the methods of the interference suppression in uncooperative system and thealgorithms of linear precoding in cooperative system, and discussed packet scheduling modeland classic scheduling algorithm.2. The related technical problems of interference suppression and performanceenhancement were discussed in uncooperative system. Soft frequency reuse （SFR） theory waslucubrated, a proportional fairness （PF） scheduling algorithm based on priority of subscribersaimed at that cell edge subscribers performance that could not be guaranteed caused by the lossof frequency resource in cell edge. The proposed algorithm allocated resource to cell edgesubscribers through assigning priority factor to subscribers in order to ensure the transmissionquality of cell edge subscribers. Simulation demonstrated that the proposed algorithm, at the costof certain throughout, could improve the fairness between cell edge and cell center subscribers,and the data rate of cell edge subscribers, enhance performance of cell edge subscriberobviously.3. The related technical problems of interference suppression and performanceenhancement were discussed in cooperative system. Considering the poor performance of celledge subscribers in zero-forcing （ZF） precoding, an interference cancellation based onprecoding algorithm is proposed. The proposed algorithm leads in SFR technology to improvethe degree of zero space and combines PF to schedule algorithm with subscriber fairness.Simulation showed that the proposed algorithm, in the cost of certain fairness, could improve thethroughout and the data rate of cell edge subscribers. Aimed at weight value’ hostile competitionso that cell edge subscribers performance could not be guaranteed in the signal to leakage andnoise ratio （SLNR） precoding algorithm, a PF scheduling algorithm maximizing SLNR ispresented. The algorithm aims at maximizing SLNR and remit pressure of value competition bySFR, meanwhile introduces PF algorithm to protect cell edge subscriberss’ fairness. The finalsimulation validated the practicality of the algorithm that it could improve system throughputand enhance cell edge user performance at the cost of certain fairness of subscribers. 4. The related technical problems of interference suppression and performanceenhancement were discussed in cooperative system with limited feedback. A precodingalgorithm based on codebook was proposed in order that CSI could not be guaranteed. Thealgorithm quantizes the precoding matrix by codebook, and brings in codebook to interferencesuppression precoding algorithm, in this way, the number of codebook is only needed to restoreprecoding matrix. Simulation demonstrated that the algorithm could ensure the performance ofsystem and edge subscribers, but performance descended a little compared to that withoutcodebook at the cost of the reduction of feedback.