Energy-Efficient Downlink NOMA Transmission Enabled by Continuous Phase Modulation

In this letter, we present a power-efficient downlink non-orthogonal multiple access (NOMA) enabled by continuous phase modulation (CPM), which improves the efficiency of the transmitter’s power amplifier (PA) by exploiting a low peak-to-average power ratio (PAPR), thereby achieving power-efficient downlink transmission. First, the system model is established. Then, we investigate the PAPR, spectral efficiency, bit-error-rate (BER) performance with/without nonlinear distortions and computational complexity, and the conventional scheme is also provided as a benchmark. The numerical results show that CPM-NOMA can achieve about <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3\sim 6$ </tex-math></inline-formula> (dB) PAPR performance gain compared to conventional schemes. In the absence of nonlinear distortions, CPM-NOMA can obtain comparable or even better BER performance than conventional schemes with similar computational complexity. In the presence of nonlinear distortions, CPM-NOMA can offer robust and power-efficient downlink transmission with smaller PAPR and BER performance losses, and is also suitable for efficient PAs, but not for conventional schemes. Finally, CPM-NOMA can also achieve the trade-off between spectral efficiency, power efficiency and BER.