Abstract
The orthogonal frequency division multiplexing (OFDM) and the non-orthogonal multiple access (NOMA) scheme are presented as promising techniques to meet the requirement of fifth-generation (5G) communication systems. Although much attention has recently been devoted to study these techniques, some scenarios have still been less explored. Considering that a fundamental part of any communication system is the use of power amplifiers, this paper presents an analytical evaluation of the bit error rate (BER) of NOMA-OFDM systems in the presence of a high power amplifier (HPA) with memory. Considering that the non-linear distortions generated by the HPA can be modeled using a polynomial model with memory, new theoretical expressions are developed to obtain the BER of the system. Specifically, exact BER expressions for a downlink NOMA-OFDM system with two users are presented and verified by Monte Carlo simulation results. The obtained numerical results demonstrate that the performance degradation of both users is highly dependent on the non-linear distortions, even when the successive interference cancellation (SIC) technique is performed perfectly.
Highlights
The Non-Orthogonal Multiple Access (NOMA) is a promising communication technique, which will satisfy the performance requirements for fifth-generation (5G) communications systems for both uplink and downlink scenarios [1,2,3,4,5]
Unlike conventional orthogonal multiple access (OMA) techniques including frequency division multiple access (FDMA), time division multiple access (TDMA), code division multiple access (CDMA) and orthogonal frequency division multiple access (OFDMA), that serve a single user in each orthogonal resource block, the NOMA can increase the number of users, improve spectrum efficiency, ensure massive connectivity, high performance, and low latency [6,7,8,9,10,11]
This performance can be measured based on the bit or symbol error rate (SER or bit error rate (BER)); having exact expressions for these error rates is very significant since it will facilitate the design of the power allocation
Summary
The Non-Orthogonal Multiple Access (NOMA) is a promising communication technique, which will satisfy the performance requirements for fifth-generation (5G) communications systems for both uplink and downlink scenarios [1,2,3,4,5]. In downlink NOMA scenarios, all the individual information signals are superimposed on a single signal transmitted by the base station (BS) to the equipment users. Studies in the literature indicate that a key parameter for good NOMA performance is the correct power allocation per user [4, 15]. This performance can be measured based on the bit or symbol error rate (SER or BER); having exact expressions for these error rates is very significant since it will facilitate the design of the power allocation. Some works can be found in the literature that aim to obtain closed-form BER expressions for different numbers of users and types of digital modulations [16, 17]
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