PPM-based relay communication schemes for wireless body area networks

This paper investigates cooperative communication schemes based on a single relay with pulse-position modulation (PPM) signaling, for enhancing energy efficiency of wireless body area networks (WBANs) in noncoherent channel settings. We explore cooperation between the source and the relay such that they do not send pulses simultaneously. Our study demonstrates that a full-duplex relay scheme can be realized by just using a ‘cheap’ relay that can either transmit or receive. Information-theoretic investigations indicate that such full-duplex relay schemes under a total transmit power constraint achieve a higher transmission rate compared to the corresponding half-duplex relay transmission that is typically used in current WBANs. According to these findings, a simple trellis encoding-and-decoding strategy based on PPM signaling is proposed for realizing a practical full-duplex relay scheme. This scheme has the additional advantage that the transmission protocol at the source remains the same regardless whether the relay is used or not. Bit-error-rate simulations illustrate the superiority of the proposed scheme.