Design and Performance Evaluation of PTS-Based PAPR Reduction Methods for the Downlink of OFDM-NOMA Systems

Advent of new systems, such as the Internet of Things (IoT) and novel communication and broadcasting systems, calls for higher data rates, massive connectivity, better cell coverage, and other improvements. Orthogonal frequency division multiplexing (OFDM) and non-orthogonal multiple access (NOMA) are amongst the promising modulation and multiple access schemes which are candidates to be implemented in the physical layer of the new systems. High data rates are achievable via OFDM which mitigates Inter-Symbol Interference (ISI) caused by the delay spread of the wireless channels. On the other hand, NOMA improves the spectral efficiency of the system by allowing users to share frequency band resources. Therefore, OFDM based NOMA (OFDM-NOMA) techniques have the potential to considerably increase the attainable data rate in novel communication systems. High peak-to-average power ratio (PAPR) is one of the issues in OFDM systems which makes high-power amplifier (HPA) to work in the non-linear region and degrades system performance. Due to the special properties of OFDM-NOMA systems, most of the PAPR reduction methods are not suitable for them. In this paper, we analyze the performance of three PTS-based PAPR reduction methods in OFDM-NOMA systems. Functional block diagram of these schemes is presented. Finally, we will compare their computational complexity, PAPR reduction, and system bit error rate (BER) performance to select the most proper PAPR reduction scheme for OFDM-NOMA systems.