Outage probability improvement of a two-way relay network with MABC DF protocol by joint relay selection and optimal power allocation

In this paper, we focus on improving the performance of a two-way relay network consisting of two end nodes and multiple relays. It is assumed that the system utilizes multiple access broadcast as the transmission protocol and decode and forward as the relaying protocol. The performance metric of the system is outage probability and we try to improve it by creating diversity gain and coding gain. Our approach is relay selection that yields diversity gain, jointed with optimal power allocation that results in coding gain. Four methods for joint relay selection and power allocation are introduced. Among them, three techniques known as OPA-OS, OPA-MMS and OPA-HS result in full diversity gain (equal to number of relays) and 1.5 dB coding gain in the outage probability. One remaining technique i.e. OPA-MSS although provides no diversity gain, but can yield coding gain in lower SNRs.