A two stage PAPR reduction method on frequency redundant OFDM system

Adding frequency diversity, through subcarrier redundancy, in orthogonal frequency-division multiplexing (OFDM) is a popular approach to improve the robustness of the system. However, frequency redundant OFDM system is prone to high peak-to-average power ratio (PAPR), due to the fact that the same source information is transmitted on multiple subcarriers. Existing schemes such as Selective Mapping (SLM) and partial transmit sequence (PTS) are effective but difficult to implement due to the high computation complexity. In this paper, we propose a two stage PAPR reduction method. We analyze the computational complexity and extensive simulations on the PAPR and show that our scheme considerably reduces the computational complexity while achieving similar PAPR reduction as SLM and better PAPR reduction than PTS. For instance, in an OFDM system with 2048 subcarriers and diversity of 8, which is the most complicated system simulated, the proposed scheme with 16 random trials can reduce the complex number multiplications by 15.55% with only 1.6 dB PAPR degradation compared to the SLM scheme. In simpler systems with fewer subcarriers and less diversity, the reduction in computational complexity by our scheme is more significant.