Optimal Power Allocation for Cooperative Systems Utilizing Quadrature Modulation
QI Lijuan · Xi'an Jiaotong Daxue xuebao · 2009
Since the equal power allocation(EPA) between the local and relayed signals in cooperative system utilizing quadrature modulation results in resource inefficiency,a quadrature modulation optimal power allocation(QM-OPA) algorithm is proposed.An optimal power allocation factor is obtained to minimize the end-to-end bit error rate(BER) of the system using the average signal-to-noise ratios(SNRs) between uplink and inter-user channels,and then the optimal power allocation data is transmitted to cooperative users through feedback channels so that the system resource utilization can be improved.The proposed algorithm is effective in reducing the BER performance and has low implementation complexity.Theoretical and simulation results show that in practical non-ideal cooperation scenarios,the QM-OPA algorithm outperforms the EPA algorithm by a maximum SNR benefit of 7 dB when the BER is in the range [10-4,10-2].