The Reduction of PAPR using CPM Mappers and Partial Transmit Sequence (PTS) Scheme in OFDM Systems

High peak-to-average power ratio of the transmit signal is a major drawback of multicarrier transmission such as OFDM. This paper describes Orthogonal Frequency Division Multiplexing (OFDM) system with Continuous Phase Modulation (CPM) mappers is considered. Such a system is known to provide superior bit error rate performance by virtue of the memory introduced by the CPM mapper compared to OFDM systems with conventional memoryless mappers such as BPSK and QPSK. In this paper, the ability of CPM mappers in an OFDM system to reduce Peak-to-Average Power Ratio (PAPR) is examined as a function of modulation parameters of mappers. Firstly, three subclasses of CPM mappers, namely, single-h CPFSK, multi-h CPFSK, and Asymmetric multi-h CPFSK are considered and their PAPR performance is assessed. Next, these mappers in conjunction with PTS technique are considered and their PAPR performance is examined. Partial transmit sequence (PTS) technique can improve the PAPR statistics of OFDM signals. In the PTS technique, the data block to be transmitted is partitioned into disjoint subblocks and the subblocks are combined using phase factors to minimize PAPR. A comparison of the PAPR reduction capability of CPM mappers relative to memoryless BPSK mappers in an OFDM system is presented. It is noted that, in general, CPM mappers offer superior PAPR performance compared to memoryless mappers in an OFDM system. Also, it is shown that CPM mappers with PTS technique in an OFDM system can offer significant improvement in PAPR performance.