Mimo Precoding. Wcdma System

WCDMA HSPA+ which supports MIMO is transition phase from 3G to 4G. In this period, through introducing MIMO, it transforms original serial code to parallel multichannel sub-streams, and scents them from different antennas in the same frequency band. MIMO which is the peculiarly technology in 4G makes frequency resource reuse to achieve high-speed transmission in original frequency band.Although MIMO offers high-speed transmission, WCDMA with MIMO imports more inter-symbol interference (ISI) in the base of multi-path interference. The basic reasons of ISI are constrained strip width and time-delay spreading, equalization in the receiving end which is traditional method can handle it. This paper cite some common equalization method and discuss their complexity which is master key in the downlink, because if we can't cut down the complexity, the phone behaved as receiving end must enlarge its size. However special with portable feature, the phone can't accept the reality. To simplify the complexity of the receiving end, precoding technology developed by and by.Precoding includes linear and nonlinear. With simple realization, linear precoding is adopted generally. Although nonlinear precoding can approach the upper limit of channel capacity, it's defeated because of the implement's complexity.This paper summarized the criterion of precoding designing by research SVD precoding and the method of codebook which is adopted by communication protocol. And the paper attempted at importing the codebook into SVD precoding.Also the paper put forward a synthetic phase precoding. The idea of designing is that the receiving end detect orthotropic signal with dot product between real and imaginary part. So the precoding needs to remove the phase interference of the channel, and orthogonalize the signals from two antennas. Compare with common precoding, it aims at simplified detecting process instead of modify resultful channel thoroughly.