| Recent technology advances are poised to enable low-cost, low-power communications in the 7 GHz of unlicensed spectrum at 60 GHz millimeter wave (mmW) frequencies. However, mmW systems that meet the Gb/s data rate demands of wireless multimedia applications must overcome severe propagation effects, including high path loss and high diffraction loss. Consequently, nodes in the network will have to use directional antennas. The narrow main beam widths of directional antennas introduce design challenges for Medium Access Control (MAC) protocols but, at the same time, provide opportunities for routing protocols to improve the network capacity through better spatial reuse. The small wavelength of a 60 GHz signal can help to achieve high directional antenna gain, but it also precludes diffraction around humans, furniture, and similarly-sized objects. These obstacles penalize a 60 GHz link budget by 20-30dB. Therefore, when people are in motion, 60 GHz network links go on and off frequently due to human body blockage; this introduces new design challenges for both routing and transport protocols.;In this dissertation, we propose solutions at the MAC and network layer to address the above challenges. In particular, we first propose an enhanced directional MAC (EDMAC) to resolve the unfairness and low channel utilization issues of deafness in directional MAC protocols for 60 GHz networks. We then study single path routing and find that shortest path routing often fails to exploit the high spatial reuse properties of directional antennas. We propose two heuristic routing algorithms, namely HOP-FP and FP-HOP, which combine the fattest-path (FP) and minimum-hop (HOP) metrics, with and without the consideration of interference. We then employ multipath routing for 60 GHz networks to fully utilize the high spatial reuse property of directional antennas. We develop an online node-disjoint path discovery process to find multiple node-disjoint paths between the source and the destination without knowledge of the global topology. In addition, we model the characteristics of link outages that are induced by pedestrian blockage. Based on analytic models and MATLAB simulation results, we show that link blockages can be mitigated by multipath routing schemes with blockage timers for broken paths. We use the ns-2 simulator to validate all proposed protocols in this dissertation. |
