A Comparative Study on Power Allocation for Cooperative Systems Over Rayleigh Fading Channels

Transmit diversity generally requires more than one antenna at the transmitter. However, many wireless devices are limited by size or hardware complexity to one antenna. Cooperative communications has been shown to enable single antenna mobiles in a multi user environment to share their antennas and generate a virtual multiple antenna transmitter that allows them to achieve transmit diversity. However, with the availability of a number of relaying nodes in a system, power management and allocation must be addressed. In this paper, an optimum power allocation technique is employed, with the main aim of improving the quality of service (QoS) in terms of the e2e BER. Furthermore, the power allocation technique is applied on a number of forwarding protocols: amplify and forward (AF), adaptive decode and forward (ADF), LLR symbol selective transmission (LLR SST) [12], SNR and LLR based hybrid forwarding [16]. The performance improvement for each of the forwarding protocols is investigated and a comparison between them is carried out. The computations are carried out using Mathematica.