Maximizing Transmission Rates for Pairwise Multiway Relay Channel

Abstract

In this dissertation, we study the effect of users' transmission ordering on the common rate and sum rate of pairwise multiway relay channels (MWRCs). As an extension for two-way relay channel (TWRC), MWRC has been proposed to improve the spectral efficiency in wireless networks. In a pairwise scheme, a set of pairs, known as ordering, is defined that represents the users' transmission schedule. Each pair of users form a TWRC and simultaneously send their data to the relay in an uplink phase. There are different strategies for the relay to form the downlink message. We consider decode-and-forward and functional-decode-forward relaying strategies for our study. We find the ordering that achieves the maximum efficiency of the pairwise MWRC. To find transmission orderings that maximize the common rate and sum rate of the system, we first develop a graphical model for the data transmission in a pairwise MWRC. Using the proposed graphical model, we, then, find the necessary and sufficient conditions for an ordering to be feasible (i.e., allows for successful decoding). Using this model, we finally find the optimal orderings that achieve the maximum common rate and sum rate of the system, respectively. Closed form expressions for the maximum achievable common rate and sum rate are also found. Computer simulations are presented for better illustration and comparison between the rate metrics of the proposed optimal orderings and random orderings.