Multi-antenna Signal Transmission System Programs And Detection Technology

By setting multiple antennas in transmitter and/or receiver, the Multi-input Multi-output (MIMO) system can exploit the best channel capacity and realize high rate and reliable communication. Orthogonal Frequency-Division Multiplexing (OFDM) is a fine technique to mitigate the effect of frequency-selective fading. Therefore, the MIMO-OFDM system, which takes advantage of these two techniques, has a very promising prospect. This thesis mainly investigates the detection techniques and the pre-coding techniques in the MIMO system and MIMO-OFDM system.Although the detection algorithms in MIMO systems have been broadly researched, the soft-output detection algorithm in coded MIMO-OFDM system under fast fading channel is still an open question. In Chaper 3, four soft-output detection algorithms are investigated, including joint maximum likelihood detection, simple maximum likelihood detection, decision feedback detection and zero forcing detection. Furthermore, an improved algorithm of decision feedback detection is proposed, which can suppress the error propagation.Chapter 4 investigates the pre-coding techniques, including the power allocation technique and the antenna selection technique with Channel State Information in the Transmitter (CSIT). Three different transmit power allocation (TPA) schemes, including equal power allocation scheme, equal SNR power allocation scheme and Lagrange power allocation scheme, are studied and compared. Simulation results show that Lagrange power allocation scheme has the best performance. However, it has the highest computational complexity. Equal SNR power allocation scheme can approach the same performance of the Lagrange scheme but has lower computational complexity. Furthermore, both the two schemes have better performance than equal power allocation scheme. In the strong correlative channel, only power allocation scheme cannot improve the deteriorative BER performance. Therefore, we investigate the joint scheme of power allocation technique and antenna selection technique. By selecting partial antennas at the transmitter, the effective SNR of the transmitting antennas is increased and the performance will be improved.Chaper 5 investigates the pre-coding scheme which combines space-frequency coding and cyclic delay diversity technology (SFC-CDD) without CSIT. In order to increase the frequency selectivity of the channel, this scheme introduces different cyclic delays into the OFDM symbols. In this approach, the frequency diversity gain and the BER performance of this scheme could be greatly improved. Furthermore, we analyse and compare SFC-CDD scheme and the CDD Pre-coding scheme proposed in 3GPP LTE proposals. Simulation results indicate that the performance of the SFC-CDD scheme is much better than CDD Pre-coding scheme. It can almost approach the performance of classical Alamouti space-time coding technique. However, compared with the Alamouti space-time coding, the SFC-CDD scheme is not limited by the number of transmit antennas and can be realized simply.