On the Use of Smart Antennas in Multi-Hop Wireless Networks

Smart antennas include a broad range of antenna technologies ranging from the simple switched beam to the more sophisticated adaptive arrays and multiple input multiple output (MIMO) links. Their ability to exploit multiple degrees of freedom helps them operate in different strategies to achieve different objectives ranging from rate increase, range increase, transmission power reduction, and higher link reliability. While these antennas have been significantly researched at the PHY layer leading to results that are easily translatable to single-hop wireless networks, very little is understood about their use in multi-hop wireless ad-hoc networks. Specific unanswered questions in this context include: (i) what kind of performance improvements can the different technologies and their strategies provide? (ii) for each technology, which of the different possible strategies is the optimal strategy to employ for a given network condition? and (iii) for a given network setting, which of the different smart antenna technologies will deliver the best performance? In this paper, we systematically answer these questions by comprehensively evaluating the relative benefits of the different smart antenna technologies.