  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 multi-gigabit wireless
services. Due to high propagation loss of mmWave channels, beamforming is
likely to become adopted as an essential technique. Consequently, transmission
in 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 multiple paths multi-hop scheduling
scheme, termed MPMH, for mmWave wireless personal area networks, 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 multiple paths multi-hop scheduling as a mixed integer linear
program (MILP), which is generally NP-hard. To enable the implementation of the
multiple paths multi-hop transmission in practice, we propose a heuristic
scheme including path selection, traffic distribution, and multiple paths
multi-hop scheduling to efficiently solve the formulated problem. Finally,
through extensive simulations, we demonstrate MPMH achieves near-optimal
network performance in terms of transmission delay and throughput, and enhances
the network performance significantly compared with existing protocols.
