An Improved SLM Algorithm for OFDMA System with Implicit Side Information

Selected mapping (SLM) is an efficient peak-to-average-power-ratio (PAPR) reduction algorithm for orthogonal frequency division multiplexing (OFDM) systems. Conventional SLM requires extra resources for side information transmission. If the side information is transmitted implicitly, significantly high computation overhead is imposed to the receiver at the user equipment (UE) side. In the orthogonal frequency division multiple access (OFDMA) system, the SLM can not be directly applied since the UE does not have access to the signal of other UEs. In this paper, we propose a novel SLM algorithm for the OFDMA system that requires no explicit side information transmission. In the OFDMA system, we assume that the data transmitted to different UEs are assigned in groups of resource units (RUs). Pilots are available in each RU for channel estimation. We design phase rotation sequences in segments of RUs. The side information is embedded in the pilot transmission. With carefully chosen phase rotations, the proposed algorithm can achieve near the theoretical PAPR performance. More importantly, with the proposed SLM algorithm, each UE can detect its own data without the knowledge of other UEs. Besides, detection of the implicit side information with the proposed algorithm is more robust than that with existing SLM algorithms. Numerical results validate the performance of the proposed algorithm.