This book is intended for designers and would-be designers of wireless communications systems. To limit the scope of this book to manageable proportions, the number of topics covered and the depth of coverage on some of those topics had to be limited. In the case of the computer simulation results for the MAC and PHY layers of the SWL system, for example, only representative results were given which allow for the reader to make their own conclusions as general as possible. For example, simulation results were given which as closely as possible related to the scenarios used in the experiments, to demonstrate how well the simulation results agreed with the experimental results, which both validated the results and allowed for conclusions to be drawn from their differences. Thus, simulation results which were too specific for the SWL or any specific smart antenna system were limited, as their usefulness to a reader desiring a different application would be limited. As another example, the discussion of the IEEE 802.11 standard is restricted to just providing the major details which influence the design of a wireless LAN system, since giving a complete description of the standard would require too much space and further information on the standard is readily available to anyone who wishes to learn more. The information provided about the standard should be sufficient for anyone seeking to acquire a general idea of how those systems work and are being implemented today, but this book is concerned about a potential future application for 802.11 and other wireless LAN systems.