On the optimal power allocation for coordinated wireless backhaul in OFDM-based relay systems

Recently, two cooperative transmission strategies, Coordinated Multi-Point (CoMP) and wireless relaying, are widely expected to be deployed in future LTE-Advanced (LTE-A) systems to improve the coverage of high data rates and cell-edge throughput. Motivated by the common cooperative diversity feature, in this paper we propose a novel OFDM-based relay system with coordinated wireless backhaul (CoMP backhaul), in which two cooperative base stations (CBS) simultaneously transmit information to an infrastructure-based cell-edge relay node (RN), so as to enhance the rate of backhaul link, as well as improve the end to end (e2e) throughput. In order to maximize the achievable e2e rate, a new Co-Phasing waterfilling power allocation scheme is developed for the multi-carrier CoMP backhaul. Meanwhile, with Taylor series expansion, a simplified iterative Co-Phasing waterfilling (ICPWF) algorithm is proposed to seek the optimal power allocation solutions. Numerical results are presented to verify the optimality of the derived scheme and to show e2e throughput gains over non-coordinated schemes.