Research On MIMO System Downlink Precoding Algorithms Based On Limited Feedback

Multiple-input multiple-output (MIMO) technology equipped with multiple antennas inthe sending and receiving sides, without increasing any spectrum and transmission power, thesystem capacity can be doubled, and it is a breakthrough in the design of the wirelesscommunication system. In particular, space division multiple access technology(SDMA)significantly improves data transmission rate and reliability of the wireless fading channelthrough the spatial multiplexing information transmitting, at the same time division and of thesame frequency. In MIMO wireless communication systems, information is precoded at thetransmit side in order to reduce the channel interference, through users selection to increasedata rate, the transmitting terminal precode and select users through partial channel stateinformation that users feedback. Therefore, a reasonable choice of precoding algorithm anduser option strategy with limited feedback can improve system performance.This paper researches multi-user MIMO wireless communication system downlinkprecoding technology based on limited feedback, including the random beam forming(RBF),the enhanced random beam forming(ERBF), combined random beam forming andzero-forcing beam forming(ORBF-ZFBF), analyze and summarize precoding, feedback ofchannel state information and greedy user selection algorithm. Simulation results show thatunder the same amount of feedback, capacity of the ORBF-ZFBF algorithm performance isbetter than the ERBF. Under the condition of low users’ quantity, ORBF-ZFBF needs littleadditional feedback and achieves better capacity than RBF.We also propose an improved algorithm that is based on the joint of random beamforming and zero forcing beam forming, which joints linear combination technique ofconfiguring multiple antennas per user, and compare this improved strategy with the originalalgorithm. Simulation results show that the improved algorithm has lower computingcomplexity and hardly increases the amount of feedback, moreover, it can achieve highersystem capacity with few users.