Research On LTE Downlink Physical Layer Closed-loop MIMO Technology

At the end of 2004, to cope with market competition from WiMAX and keep pace with the trend of mobile communication's combing with Broadband Wireless Access technology, 3PrdP Generation Partnership Project started Long Term Evolution, the aim of which is improving UMTS. With OFDM and MIMO as its key technologies, LTE is of certain characteristics of 4G mobile communication; even it can be regarded as"quasi-4G"technology.This thesis lays emphasis on the precoding technology for Layered Space Frequency encoding architecture adopted by Closed-loop MIMO when using 4×2 multi-antenna array, involving closed-loop feedback mechanism, off-line codebook construction needed by precoding operation and codebook matching criterion. Codebooks related to the problem of subspace packing in the Grassmann manifold have been designed, which is based on Household transform; a codebook construction formula has been deduced to maximize the minimum chordal distance, and codebook matching criterion adopting MMSE has been deduced.According to LTE TS36 serial protocols on LTE downlink physical layer and channel estimation algorithms based on reference signal in frequency domain, LTE downlink physical layer Closed-loop MIMO technology has been simulated with application of off-line codebook construction method and codebook matching criterion developed in this thesis.