Multiplexing-Diversity Medium Access for Multi-User MIMO Networks

摘要

While MIMO technologies are rapidly adopted in 802.11, mobile devices increasingly have different numbers of antennas. Several multiuser MIMO (MU-MIMO) MAC protocols have recently been proposed to allow concurrent transmissions across different links. Though those protocols better utilize the available degrees of freedom, they however do not provide each data stream any receive diversity. This paper introduces multiplexing-diversity medium access (MDMA), a distributed MU-MIMO MAC protocol that achieves both the multiplexing and receive diversity gains at the same time. Instead of letting a node pair use its full degrees of freedom, MDMA allows as many contending node pairs as possible to transmit concurrently and share all the available degrees of freedom. By doing this, MDMA exploits more antennas equipped at different receiving nodes to provide concurrent streams more receive diversity, without sacrificing the multiplexing gain. We show via testbed experiments and simulations that MDMA achieves a similar multiplexing gain, but extracts more diversity gains as the number of antennas at any nodes increases. It hence improves the throughput by up to 48.8 percent as compared to the protocol enabling only spatial multiplexing.