On indoor wireless channel characterization and the design of interference -aware medium -access control protocols for packet switched networks.

摘要

This dissertation addresses two distinct topics. The first one involves the characterization of the indoor wireless channel. A good understanding of the propagation laws and the statistics obeyed by the indoor wireless channel is very important, especially in view of the rapidly emerging market for home and office wireless network products. The finite difference time domain method (FDTD), very well known in the field of microwave engineering, is used to predict the channel inside a residence. The validity and usability of the method is demonstrated by comparing our predictions against measurements for the same residence. Motivated from the good agreement between the two, we re-formulate FDTD to reduce its memory requirement by 33%. We present the new formulation and discuss experimental results that verify its equivalence to the original FDTD.;The second topic addressed by the dissertation has to do with interference adaptive medium access control (MAC) protocols for packet switched networks. This is also a very important topic for wireless transmission, because new wireless networks will be designed primarily for Internet services, with voice traffic also running on top of the Internet Protocol. First, we study the co-channel interference statistics created by a simple MAC for micro-cellular environments, and demonstrate that it can be modeled very accurately as Markovian. We present a Markov analysis for the packet dropping probability of voice traffic for this MAC, when co-channel interference becomes the dominant impairment. Subsequently, motivated by this analysis we extend the simple MAC protocol to include dynamic channel allocation (DCA) schemes that adapt resource allocation based on interference measurements. We present two different DCA schemes and study their performance via simulations. We demonstrate that a single frequency reuse factor is possible when the MAC can do channel assignment on a packet by packet basis, and has the ability to utilize interference measurements and power control. Finally, in the context of an infrastructure-less, network, we present a MAC protocol that allows for the multicasting of real-time traffic. We solve the problem of concurrent bandwidth reservation and route formation for the multicast mesh. We present a distributed protocol that uses one-hop neighborhood information and study its performance in terms of throughput via simulations.