Boosting Spatial Reuse via Multiple-Path Multihop Scheduling for Directional mmWave WPANs

With huge unlicensed bandwidth available in most parts of the world, millimeter-wave (mmWave) communications in the 60-GHz band has been considered as one of the most promising candidates to support multigigabit wireless services. Due to high propagation loss of mmWave channels, beamforming is likely to be adopted as an essential technique. Consequently, transmission in the 60-GHz band is inherently directional. Directivity enables concurrent transmissions (spatial reuse), which can be fully exploited to improve network capacity. In this paper, we propose a multipath multihop scheduling scheme, which is known as multipath multihop (MPMH), for mmWave wireless personal area networks (WPANs), where the traffic across links of low channel quality is transmitted through multiple paths of multiple hops to unleash the potential of spatial reuse. We formulate the problem of MPMH as a mixed-integer linear program (MILP), which is generally NP-hard. To enable the implementation of the multipath multihop transmission in practice, we propose a heuristic scheme including path selection, traffic distribution, and MPMH to efficiently solve the formulated problem. Finally, through extensive simulations, we demonstrate that MPMH achieves near-optimal network performance in terms of transmission delay and throughput and enhances network performance significantly, compared with existing protocols.