Impact Of Physical Layer Techniques On Wireless Networks

This thesis provides frameworks for evaluating the impact of diferent physical layer techniqueson the network performance. The emphasis of the framework is on how to analytically char-acterize various performance metrics as functions of diferent parameters. By analyzing thosefunctions, insights for design and optimization over diferent parameters can be obtained. Twophysical layer techniques are considered separately in this thesis, because of their potential forimproving network throughput. They are two-way relaying and multi-user MIMO (MU-MIMO).Each of them corresponds to a research topic.In the frst research topic, we consider routing path selection in a two-way relay network.Information theoretical analysis is carried out to derive bandwidth efciency and energy ef-ciency of a linear multi-hop network with transmission through two-way relay channels. Suchanalysis provides a framework of routing path selection by considering bandwidth efciency,energy efciency, and latency subject to physical layer constraints such as the transmission rate,processing power, path length, and the number of relays. This framework provides insightfulguidelines for future routing protocol design in a two-way relay network.In the second research topic, we develop an analytical model to investigate the saturationthroughput and mean access delay performance of a recently proposed CSMA/CA-based MU-MIMO wireless LAN. We propose and model a distributed opportunistic transmission scheme,where clients are able to contend for the concurrent transmission opportunities only whentheir concurrent rates exceed a threshold. Comparisons with simulation results show that ouranalytical model provides a close estimation of the network performance. By means of theproposed model, we evaluate the throughput and delay performance with respect to diferentnetwork parameters, including the backof window sizes, the number of antennas at the AP,the network size, and the threshold of the opportunistic transmission scheme. The analyticalmodel and performance analysis provide optimization over various parameters and an in-depthunderstanding of the random access MU-MIMO transmission scheme.