Improvement in Performance of Wireless Relay Nodes Using Physical Layer Network Coding

Abstract

Recent advancements in high data rate networks have led to a growing interest in improving performance of wireless relay networks through the use of Physical Layer Network Coding (PLNC) technique. In the PLNC technique, the relay node exploits the network coding operation that occurs naturally when the two electromagnetic (EM) waves are superimposed on one another to directly decode the modulo-2 sum of the transmitted symbols.

In this thesis, we will present an optimal power control algorithm for performance improvement in wireless relay nodes implementing physical layer network coding. We shall also present a sub-optimal power control algorithm and compare its performance with the optimal power control algorithm. Our approach will first derive the probability of error for the amplitude-controlled system using Maximum Likelihood detection and then minimize the probability of error using amplitude control functions as variables to derive the optimal power control functions. We shall start by considering the thresholds of the system to be the maximum of the independent received amplitudes to derive the probability of error equations and then extend it to a variable threshold system, where the threshold is a function of independent received amplitudes. We then derive an optimal power control algorithm for a single channel Rayleigh system and implement this power control algorithm independently on the terminals to achieve a sub-optimal power control algorithm.

Our results show that the proposed optimal power control algorithm boosts the performance of the PLNC system significantly compared to the no power control system. We also show that there are no significant differences between the performances of optimal power control and the sub-optimal power control algorithms. We further show that the performance of the system is not degraded much when the amplitudes of the terminals deviate from the optimal amplitudes.