On the Performance and Power Optimization of Multihop Multibranch Relaying Networks With Cochannel Interferers

In this paper, we study the performance of opportunistic amplify-and-forward (AF) multihop multibranch relaying networks operating in the presence of cochannel interference (CCI). We obtain exact and upper bound expressions for the end-to-end signal-to-interference-plus-noise ratio (SINR), assuming transmissions over independent nonidentical Rayleigh fading channels. Afterward, the cumulative distribution function (cdf) and the probability density function (pdf) of the upper bound end-to-end SINR are investigated. According to these statistics, we obtain a lower bound closed-form expression for the outage probability. Furthermore, an approximate expression for the pdf of the end-to-end SINR is derived. Subsequently, simple expressions for the approximate error and outage probabilities are provided. These expressions deliver more understanding on the effect of the system parameters. Moreover, we address the optimization of the power allocation among the transmit nodes to enhance the overall system performance. As an optimal solution for the resource-allocation problem at hand, the adaptive power allocation minimizes the error probability under constraint on the aggregate power over the branch with the maximum SINR. It is shown that by applying the energy obtained through the optimization process, the performance of the network is improved significantly. Eventually, the accuracy of the analysis is validated by comparing the numerical results with Monte Carlo simulations, and insightful discussions are provided.