Distributed transmission power control method based on soft FFR for cellular downlink

We propose a distributed transmission power control method based on soft fractional frequency reuse (SFR) for cellular downlink orthogonal frequency division multiple access (OFDMA). The proposed method adaptively controls the transmission power density in the protected and non-protected bands of SFR depending on the user distribution within a cell in order to maximize the geometric mean of the user throughput (in other words, log sum of user throughput). Thus, it is based on the proportional fair (PF) criteria. The proposed method assumes a decentralized approach, in which complicated inter-base station (BS) cooperation is not required. Since the optimal power allocation to the protected and non-protected bands is dependent on the resource allocation of the protected and non-protected bands to the respective users, the proposed method jointly optimizes the power allocation and resource allocation by using an iterative algorithm. Computer simulation results show the effectiveness of the proposed method compared to conventional universal frequency reuse (UFR) and non-adaptive SFR.