A subcarrier-phase control based peak power reduction method for coded space division multiplexed OFDM systems

In this paper, we propose a sub-carrier phase control based peak power reduction (PPR) method for a turbo-coded space division multiplexed orthogonal frequency division multiplexing (SDM-OFDM) system. The PPR method is an extended version of the existing partial-transmit sequence (PTS), where the same numbered cluster signals at different antenna elements are weighted by the same weighting factors (WFs) and PAPR of OFDM signal is reduced by adjusting the phase of each cluster signal by multiplying WFs so as to minimize PAPR of OFDM signals. On the receiver side, WF estimation and error correction are jointly performed with turbo decoding, where WFs are estimated by exploiting the decoding results of two data streams passing through different channel in SDM-OFDM systems. When the PPR method using 9 clusters is applied to 64-QAM OFDM signal, instantaneous power of the transmit signal at the CCDF of 10^-4 can be reduced by about 1.9 dB. In addition, when a peak limiter is applied to 64QAM-OFDM system using the PPR method, instantaneous power at the CCDF of 10^-4 is reduced by about 3.1 dB as compared to case without any peak power reduction, while the proposed method achieves almost the same block error rate (BLER) performance in attenuated 12-path Rayleigh fading condition.