Diversity and Spectral Efficiency in Wireless Relay Networks

by Deqiang Chen Motivated by the increasing demand for higher data rate, broader coverage, and lower infrastructure cost in wireless systems, a major effort is being made to study the use of relay stations in wireless networks. In this dissertation, we propose efficient relaying protocols for two types of wireless networks, i.e., networks with one destination, one relay and multiple sources, and networks with one destination, one source and multiple relays. We model the former as a multi-access relay channel (MARC) and refer the latter as a multihop network. For a MARC, we propose the multi-access relay amplify-forward (MAF) protocol. The proposed protocol allows for a low-complexity relay, allows the users to operate as if in a normal (non-cooperative) multi-access channel (MAC), and allows multiple users to achieve significant gains from sharing a single amplify-forward relay in slow fading environments. MAF achieves the optimal diversity-multiplexing trade-off at high multiplexing gains. Analysis of the protocol reveals that it outperforms the compress-forward strategy at low multiplexing gains and further outperforms the dynamic decode-forward protocol at high multiplexing gains. We also propose different routing protocols for wireless multi-hop networks. An information theoretic analysis suggests that there is an optimum number of hops in maximizing the end-to-end spectral efficiency for a multihop network with