Parallel relay-assisted three-phase MIMO space division multiple access transmission for multi-hop throughput improvement

SUMMARY Multi-hop communications equipped with parallel relay nodes is an emerging network scenario visible in environments with high node density. Conventional interference-free medium access control (MAC) has little capability in utilizing such parallel relays because it essentially prohibits the existence of co-channel interference and limits the feasibility of concurrent communications. This paper aims at presenting a cooperative multi-input multi-output (MIMO) space division multiple access (SDMA) design that uses each hop's parallel relay nodes to improve multi-hop throughput performance. Specifically, we use MIMO and SDMA to enable concurrent transmissions (from multiple Tx nodes to single/multiple Rx nodes) and suppress simultaneous links' co-channel interference. As a joint physical layer (MAC/PHY) solution, our design has multiple MAC modules including load balancing that uniformly splits traffic packets at parallel relay nodes and multi-hop scheduling taking co-channel interference into consideration. Meanwhile, our PHY layer modules include distributive channel sounding that exchanges channel information in a decentralized manner and link adaptation module estimating instantaneous link rate per time frame. Simulation results validate that compared with interference-free MAC or existing Mitigating Interference using Multiple Antennas (MIMA-MAC), our proposed design can improve end-to-end throughput by around 30% to 50%. In addition, we further discuss its application on extended multi-hop topology. Copyright © 2012 John Wiley & Sons, Ltd.