Power Allocation Based on SEP Minimization in Two-Hop Decode-and-Forward Relay Networks

TL;DR

This paper proposes a new power allocation scheme for two-hop relay networks that minimizes average symbol error probability using statistical channel information, with a practical approximate closed-form solution validated by simulations.

Contribution

It introduces a novel closed-form expression for SEP and develops a convex optimization-based power allocation method with a simplified approximate solution.

Findings

The proposed scheme reduces symbol error probability compared to existing methods.

The approximate solution offers a good trade-off between complexity and accuracy.

Simulation results confirm the effectiveness of the new power allocation approach.

Abstract

The problem of optimal power allocation among the relays in a two-hop decode-and-forward cooperative relay network with independent Rayleigh fading channels is considered. It is assumed that only the relays that decode the source message correctly contribute in data transmission. Moreover, only the knowledge of statistical channel state information is available. A new simple closed-form expression for the average symbol error probability is derived. Based on this expression, a new power allocation method that minimizes the average symbol error probability and takes into account the constraints on the total average power of all the relay nodes and maximum instant power of each relay node is developed. The corresponding optimization problem is shown to be a convex problem that can be solved using interior point methods. However, an approximate closed-form solution is obtained and shown to be practically more appealing due to significant complexity reduction. The accuracy of the approximation is discussed. Moreover, the so obtained closed-form solution gives additional insights into the optimal power allocation problem. Simulation results confirm the improved performance of the proposed power allocation scheme as compared to other schemes.