Fundamentals of Circular QAM for Wireless Information and Power Transfer

In this work, circular quadrature amplitude modulation (CQAM) is investigated for simultaneous wireless information and power transfer (SWIPT). Both coded and uncoded cases are considered, under which the flexibility of CQAM for SWIPT is presented. Specifically, for uncoded transmission, CQAM is designed to achieve a controllable tradeoff between energy harvesting and information transfer performance. In the coded case, bit-interleaved coded-CQAM are designed based on the maximization of the discrete-input capacity. Our results show, in both cases, the superiority of CQAM compared to known modulation schemes (i.e. QAM, PSK, and PAM) in terms of error rate and energy harvesting.