Selected Mapping Without Side Information for PAPR Reduction in Modified Walsh-Hadamard Code Division Multiplexing

Modified Walsh-Hadamard code division multiplexing (MWHCDM) is effective for helicopter satellite communications, where the rotor blades block the transmission channel pe-riodically. This paper addresses reducing peak-to-average power ratio (PAPR) for MWHCDM, applying a selected mapping (SLM) method without side information, proposed for orthogonal frequecy division multiplexing (OFDM) previously, to MWHCDM. The SLM method is especially suitable for the primary modu-lation of quaternary phase-shift keying (QPSK), although the primary modulation of MWHCDM is binary phase-shift keying (BPSK). A novel multiplexing processing based on the structure of MWHCDM signals resolves this mismatch. In addition, introducing amplitude information to the evaluation function employed for blind estimation of phase sequence enhances the estimation performance. Computer simulation shows that the proposed SLM method achieves excellent PAPR reduction and phase sequence estimation performance, causing no degradation in bit error rate (BER) performance.