Asympotic capacity bounds for ad-hoc networks revisited: the directional and smart antenna cases

Directional and smart antennas can be useful in increasing the capacity of wireless ad hoc networks. A number of media access and routing protocols have been recently proposed for use with such antennas, and have shown significant performance improvements over the omni-directional case. However, it is important to explore if and how different directional and smart antenna designs affect the asymptotic capacity bounds, derived by Kumar and Gupta (2000). These bounds are inherent to specific ad-hoc network characteristics, like the shared nature of the wireless media and multihop connectivity, and may pose major scalability limitations for such networks. In this paper, we look into how directional and smart antennas can affect the asymptotic behavior of an ad-hoc network´s capacity. Specifically, we perform a capacity analysis for an ideal flat-topped antenna, a linear phased-array antenna, and a fully adaptive array antenna model. Finally, we explain how an ad-hoc network designer can manipulate different antenna parameters to mitigate the scalability problem of ad-hoc networks.