Empirical Discussion on Directional MAC Protocols for Ad hoc Networks using Practice Smart Antennas

Recent studies on directional media access control (MAC) protocols using smart antennas for wireless ad hoc networks have shown that directional MAC protocols outperform traditional omni-directional MAC protocols. Those studies evaluate performance primarily based on a simulations, where antenna beam is assumed to be ideal, i.e., with neither side-lobes nor back-lobes. Propagation conditions are also assumed to be based on a mathematical model without realistic fading. However, for the real application of ad hoc networks those optimistic assumptions do not hold anytime. In this paper, we develop at first a testbed for directional MAC protocols which enables investigation of the performance of MAC protocols in a real environment. It incorporates ESPAR as a practical smart antenna, IEEE802.15.4/ZigBee, GPS and gyro modules to allow easy installation of different MAC protocols. To our knowledge, it is the first compact testbed with a practical smart antenna for directional MAC protocols. We implement a directional MAC protocol called SWAMP to evaluate it in a real environment. The empirical discussion based on the experimental results shows the degradation of the protocol with ideal antennas, and it shows that the protocol still achieves the SDMA effect of spatial reuse and the effect of communication range extension.