Performance Analysis of Downlink NOMA and OFDM-IM For Wireless Communication Systems

Abstract

h the exponential rise of mobile data traffic, Multiple Access (MA) techniques played an im portant role in the development of wireless communication generations to fulfill the demand for high SE and vast connection. These techniques have been utilized in a variety of domains like time, frequency, code, space, patterns, polarization, and various combinations thereof. The orthog onal frequency division MA (OFDMA) technique is the most commonly used approach in down link transmission. However, NOMA has sparked the curiosity of researchers as an enhancement to orthogonal multiple access (OMA) due to its capacity to accommodate and enhance more mo bile devices and provide improved spectrum efficiency. The OFDM-IM concept was influenced by the spatial modulation (SM) concept; index modulation techniques are applied to the indices of an OFDM system's accessible subcarriers. Unlike traditional OFDM, the number of active subcar riers in the OFDM-IM scheme can be modified, resulting in superior bit error rate (BER) perfor mance. The objectives of this study are to investigate the impact of active subcarriers and the M ary constellation scheme on the BER performance of OFDM-IM. To accomplish these goals and validate the system's performance an experimental method using MATLAB software was used. The simulation results indicated that changing the number of active subcarriers and the number of constellations affects system performance. According to the results, at 𝑀 = 4, OFDM-IM with 𝑘 = 3 outperforms OFDM by 10 dB at BER values of 10−3 . At a BER of 10−2 , 𝑀 = 4 gains 6 dB over 𝑀 = 16 for a given value of 𝑘 = 4. It is seen and concluded that employing smaller values of subcarrier activation ratio and lower M-ary constellation results in higher system performance.