Research On MIMO Technologies In COMP System

With the rapid growth of the demand for wireless data services and the introduction of new air interface technologies, the mobile communication system is facing new challenges to support high-speed multimedia services transmission and guarantee seamless coverage. In order to meet the requirement of IMT-Advanced (International Mobile Telecommunications-Advanced) system, including the demand for bandwidth, peak data rate and system throughput, Enhanced MIMO(Multiple Input Multiple Output) technology, CoMP (Coordinated Multi-point Tx/Rx) were written in LTE-Advanced (Long Term Evolution-Advanced) Protocol as a key technologies by3GPP (3rd Generation Partnership). With the rapid development of the next generation mobile communication system and support by laboratory projects, the thesis researches multi-antenna enhancement technology in coordinated multipoint transmission system and focuses on multi-user MEMO (MU-MLMO) precoding technologies and associated power allocation schemes.The thesis gives systematical research and basic classification of coordinated multipoint transmission system. The basic classifications of CoMP downlink transmission technology are joint processing (JP) and collaborative scheduling/beamforming (CS/CB). Joint processing technology includes joint transmission (JT) technology, and dynamic cell selection technology (DCS). Joint transmission is adopted as the main form of joint processing, also the main transmission scheme for multi-point collaboration in intra-eNodeB scenario.For precoding technology for MU-MIMO system, this thesis focuses on non codebook precoding technology. Based on zero forcing (ZF) criteria, the minimum mean square error (MMSE) criteria and maximun signal to leakage and noise ratio (SLNR) criteria, the thesis studies MU-MIMO precoding technologies and gives the analysis and comparison between several precoding schemes. And the main focus is on SLNR precoding technology.To the study on SLNR precoding and power allocation scheme, the thesis researches on the existing power allocation schemes for SLNR precoding from the view of communication transmission reliability and validity. Aiming at improving the transmission quality, minimizing the total system mean square error is used as of the optimization objective for SLNR precoding and power allocation scheme. By constructing the Lagrangian fuctiong and using the convex optimization theory, an optimal power allocation scheme with iterative operation is proposed. By this proposal, locally optimal solution for power allocation factor, precoding matrix and receiver decoding matrix are obtained ain each iterative procedure. This iterative power allocation scheme for SLNR precoding gives BER performance improvement. By considering of the complexity of power allocation algorithm, a suboptimal power allocation scheme for SLNR precoding is proposed. By trading off between BER performance and algorithm complexity, suboptimal power allocation scheme give reduction on computational complexcity with the cost of losing BER performance, still holding the advantage in all SNR regines when comparing the BER performance with equal power allocation algorithm.