PAPR Reduction in OFDM-Based NOMA using Trellis Shaping

Abstract

Wireless communication networks are expanding exponentially which makes challenging requirements for 5-generation (5G) and beyond 5G wireless technology. Different solutions have been proposed by the researchers to fulfil these demanding challenges. One of such technique which is making its way into 5G communication technologies is non-orthogonal multiple access (NOMA). NOMA has been considered as possible radio access mechanism for the next-generation of cellular networks. The system performance can further be enhanced using OFDM-Based NOMA. However, a major drawback of multicarrier NOMA is its inherited high peak-to-average power ratio (PAPR). OFDM-based NOMA systems with a high PAPR are inefficient in terms of energy use. Herein, we propose Trellis for PAPR reduction in OFDM-based NOMA systems. Trellis shaping is a distortion-free techniques which provides promising gains in terms of PAPR reduction. The metric used to search for a sequence of symbols (shaped symbols) in the trellis of the shaping code is based on minimization of the auto-correlation of the side lobes. This method’s performance is based on constellation mapping. Simulation results obtained shows that a promising gain in terms of PAPR can be obtained with our proposed solution for OFDM-based NOMA systems. To boost the system’s performance in terms of PAPR, we further propose the use of higherdepth shaping codes. Using shaping codes with higher trellis depths improves the PAPR reduction. As second part of this thesis, we propose a hybrid PAPR reduction algorithm: active constellation extension based trellis shaping for PAPR reduction in OFDM-based NOMA systems. Extending the constellation points provides additional gains in terms of PAPR.