MIMO-OFDM系统中跨层媒体接入控制

Cross-layer Medium Access Control in MIMO-OFDM Systems

针对MIMO-OFDM系统,提出了一种基于时隙ALOHA协议的随机接入方案,该方案利用一个简单的中心控制器和物理层的自适应调制技术以及MIMO迫零信号检测算法,在媒体接入控制层提供多包接收能力,解决包冲突问题。在满足用户BER要求的前提下,研究了系统最大化吞吐量时,接入同一子载波的最优用户数,并为此设计最佳的接入请求概率。仿真结果表明,最优接入天线数大约为接收天线数的四分之三,此时可以获取最大的吞吐量。

A random access scheme is proposed based on the conventional slotted ALOHA protocol. With a central controller at access point,the problem of packet collisions can be solved at the PHY layer with multipacket reception （MPR） by using signal processing technique,i, e. adaptive modulation and MIMO zero-forcing signal detection. We study the possible optimal number of users which are likely to transmit at the same subcarrier and slot to maximize the throughput subject to their BER requirements. Then the access probability is designed to achieve the desired number of users. Numerical results show that desired number of transmit antennas is about three quarters of the number of receive antennas. With this setting,the system throughput is maximized.