The Researchon Linear Pecodingin MIMO System

MIMO (Multiple Input Multiple Output) is a technique which implemented withmultiple transmit antennas and multiple receive antennas and without losing spectrumbandwidth and power of transmission. The linear precoding technology makes use of somekinds of signal processing methods in the transmitters so that the receiver can be simplified.The system performance can be advanced with the feed-back channel information, avoidingthe complicated decoding algorithms. Linear precoding technology has been a researchhotspot in the telecommunication field recently because of its great potential in futurebroadband wireless communication systems.In the traditional linear precoding technique, singular value decomposition(SVD)linearprecoding, geometric mean decomposition(GMD)linear precoding and uniform channeldecomposition(UCD)linear precoding are the three most extensive coding schemes.UCDscheme can better adapt to the channel correlation and the impact of feedback error which hasbest prospects. The traditional VBLAST system requires the number of receiving antennasgreater than the number of transmitting antennas, but in the practical application, the numberof base station antennas are often greater than the mobile terminal. This situation increasedthe difficulty of system design.In response, this paper combines space-time block code (STBC) and UCD coding gives aSTBC-UCD linear precoding scheme. Compared to STBC, STBC-UCD also has such merit:good anti-fading performance, simple structure, easy to implement and can achieve fulltransmit diversity gain and so on. Moreover, STBC-UCD improved the shortcomings ofSTBC which the rate is limited by the number of transmitting antennas, and can meet theactual needs that the number of base station antennas greater than mobile terminals. Thesimulation results verify the proposed that BER performance of STBC-UCD scheme betterthan STBC scheme.UCD scheme for single-user MIMO system has a very superior optimization results, while in multi-user MIMO system, due to interference between users and different users cannot obtain inter-channel information, UCD scheme can not be used directly. This papercombines block diagonalization (BD) and UCD coding gives a BD-UCD linear precodingscheme. We first started with block diagonalization method to eliminate interference betweenusers, and then use the UCD decompose feedback algorithm for each user. Compared with theZF scheme,the simulation shows that this scheme has received good results.