Influence of the PAPR of PD-NOMA-OFDM Signals on the Performance of an RF Rectifier for Low-Power Energy Harvesting

Abstract

The combined use of Orthogonal Frequency Division Multiplexing (OFDM) and Non-Orthogonal Multiple Access (NOMA) techniques in Fifth-Generation (5G) wireless communication networks plays an important role in the connectivity of Internet of Things (IoT) devices. However, providing a sustainable energy supply for massive IoT deployments remains challenging. A promising solution to address this problem is Radio Frequency Energy Harvesting (RFEH). Despite its advantages, its efficiency can be significantly compromised if Radio Frequency (RF) signals exhibit a high Peak-to-Average Power Ratio (PAPR). This work investigates the impact of the PAPR of NOMA-OFDM signals on the Power Conversion Efficiency (PCE) of an RF rectifier for RFEH applications. A Power Domain NOMA-OFDM (PD-NOMA-OFDM) system operating in the 3.5 GHz band is developed, based on the Software-Defined Radio (SDR) concept, and an RF rectifier optimized for an input power $P_{in}$ of −20 dBm is manufactured. Experimental results show that, under the design operating condition, the RF rectifier achieves a PCE of 30% with a Continuous Wave (CW) signal, while PD-NOMA-OFDM and OFDM signals exhibit a PCE of 27%. At the point of maximum PCE ($P_{in}$ of −6.7 dBm), the PD-NOMA-OFDM signal reaches a PCE of 51.9%, an 8% reduction compared to the CW, which achieved a PCE of 59.9%. From a communication standpoint, the PD-NOMA-OFDM system achieves a Bit Error Rate (BER) of $4.8 \cdot 10^{-3}$ at −20 dBm and $1.7\cdot 10^{-6}$ at the maximum PCE point, validating the crucial role of PAPR management in the joint optimization of RFEH and communication performance.