Mimo Mc-cdma System, Channel Estimation In Detection Technology Research

CDMA is an important technique in 3G, and orthogonal frequency division multiplexing (OFDM) modulation will be a key technique in future wideband wireless transmission, because it provides a good solution for high data rates transmission in a mobile environment which makes a highly hostile radio channel. So, combining OFDM and CDMA to forming a MC-CDMA system is one of the important developing directions of future mobile communication. MC-CDMA is considered as the most promising scheme between the three multicarrier techniques because it can achieve frequency diversity and excellent performance. Multiple input multiple output (MIMO) transmit multiple data streams in parallel subchannels in spatial, thus greatly increasing the system throughput without additional bandwidth and power requirements. Applying MIMO technique in conventional MC-CDMA scheme to form MIMO MC-CDMA system will enhance the system performance of MC-CDMA. In this thesis, we focus on the design of the V-BLAST detection, multiuser detection, iterative detection and decoding and channel estimation techniques for MIMO MC-CDMA system.Firstly,a joint V-BLAST(Vertical-Bell Labs Layered Space-Time)and multiuser detection algorithm for MIMO MC-CDMA system is proposed in this paper. Based on a modified iterative interference cancellation V-BLAST detection with minimum mean squared error(MMSE), two groups of detection data are obtained for each user, then maximum-likelihood(ML)scheme is applied on the iterative output of all users to select the better group of data to optimize system performance. Simulation results show that the proposed algorithm improves the BER performance of the system significantly.Then,channel encoding is added to the system and a turbo receiver structure with MMSE is proposed in an uplink turbo-coded MIMO MC-CDMA system and the extrinsic information of the detector is computed. The receiver is achieved by using V-BLAST detection and multiuser detection with MMSE technique. Simulation results show that the iterative cancellation receiver in turbo coded system can gain much better performance than conventional receiver in uncoded system. A low-complexity scheme is also presented, the performance of the partial interference cancellation scheme in iterative detection and decoding is analyzed by simulation.The channel estimation technique is also discussed in this paper. The Least Square (LS) channel estimation algorithm in time domain and the designing technique of...