Study On Multiuser Detection And MAC Protocol For Uplink Multiuser MIMO Systems Based On WLAN

Higher throughput is needed with development of wireless local area network service.The legency IEEE802.11MAC protocol support single point to single point transmission,thethroughput of which is limited by collision and frame spacing, only to improve data transferrate did not have significantly work. In order to improve this problem, we can considermultiple points to single point transimission in WLAN system. Multi-user MIMO canstastisfy the transimission of multiple points to single point, that is to say the multi-user cancommunicate with a access point(AP) with multiple antenna in a same frequency bandthrough the access space division multiple access(SDMA), which can improve the throughputsignificantly. But the legacy IEEE802.11MAC protocol is not enough to realize SDMA inWLAN systems. To sovle this problem, we need to modify MAC protocol. Moreover, thereceived single at AP is composed of the signals from different users. In order to decode thesignals correctly, we need to suitable multiuser detection techology to separate thetransmission data of each user.The paper does the following work for realizing the SDMA in multi-uer MIMO-OFDMsystems based on WLAN:1) MAC protocol for realizing SDMA in WLAN. A distributedMAC protocol named SDMA-MAC is proposed in the paper. Its transfer process is dividedinto two parts: the random access period and data transmission period. Multiple users contendthe channel by the way of RTS/CTS in random access period. AP uses a dual mode responsemechanism of CTS to determine whether the user who sends RTS transmit data immediately.For the users, they just need to identify the types of CTS frame to decide whether to send dataimmediately or wait for a moment. The simulation results show that the throughput and delayperformance of SDMA-MAC protocol are better than that of IEEE802.11MAC protocol.2)Another work is technology of multi-user detection in multi-user MIMO-OFDM systems.First we use the V-BLAST detection algorithm and jonit ransmission-receiving beamformingalgorithm to detection the singnals of the single user MIMO-OFDM system, the simulationresult is provided to show the performance of the algorithms. Then we use the multi-userdetection algorithms based on OBF technology and EBF-V-BLAST algorithm to detect thesingnals of multi-user MIMO-OFDM systems. The similuation results show that the performance of EBF-V-BLAST algorithm is better than algorithm which based on OBFtechnology.