Research On Performance Of Multiple Antennas And Cooperative Base Station With Limited Feedback

How to efficiently improve date transmission stability, speed of wireless communications links and provide a wide range of network coverage has been a challenging problem in the future wireless communication systems. Recently, many communication organizations and research scholar propose that take the MIMO (multiple input multiple input) as the one of the key technology for solving this problem. Space time, space frequency codes, precoding and cooperative communication for MIMO has been researched widely.This dissertation researchs the theory and technology of the space time coding and the cooperation base station deeply. The major research works and contribution are summarized as follows:1、In SFBC (space frequency block codes) MIMO systems, there is a fixed DMT (Diversity Multiplexing Tradeoff) point between diversity and multiplexing in different quanlity of channel. It is difficult to have good performance. We take idea of opportunistic codes into the space-frequency code, and propose a new opportunistic space frequency codes. The proposed codes can get the different DMT point based on different quanlity of channel. If the quanlity of channel is good, the multiplexing is high (diversity is low). If the quanlity of channel is bad, the diversity is high (multiplexing is low). This method can opportunistically use the channel and improve the performance of system.2、For multi-user MIMO and the cooperative multi-cell systems, we study the bit feedback allocation method, a new limited feedback bit allocation scheme is proposed. In this scheme, the bits for local base station (these bits for mitigating multiple user interference) and the bits for adjacent interference base station (these bits for mitigation the interference from adjacent base station) are different. Under limited feedback and fixed bits, we consider the power of two kinds of interference, and allocate feedback bit reasonably for local service base station and adjacent interference bases station (these bits for quantizing channel). Finally, we analyse of rate loss due to the limited feedback. It is shown that our scheme minimizes the rate loss duo to the limited feedback. Comparing with traditional equal bits allocation method, our proposed scheme has better performance.3、For quantization error and channel delay caused by limited feedback, we analyze the rate loss with limited feedback in cooperative base station and obtain the optimal feedback bit based on rate loss. When feedback bits are increased (quantization error is decreased), channel delay is decreased, and rate loss will be decreased. The simulations showns that. Simultaneously, we can get that the channel delay increases gradually, the rate loss can be improved little by the increasing of feedback bits.4、For asynchronous interference duo to different propagation times between the base station and mobile stations in multiple users in cooperative base station, we propse the MMSE (Minimum Mean Square Error)precoding based on limited feedback. This precoding scheme is designed with RVQ (Random Vector Quantization) method and per-base station power constrain. The simulation shows that proposed MMSE scheme achieve an improved performance and decrease the asynchronous interference compared with the conventional MMSE in base station cooperative systems.