Abstract
Non-Orthogonal Multiple Access (NOMA) has been recently proposed as a good alternative to meet 5G and beyond requirements in terms of high spectral efficiency, massive connectivity, and low latency. It has been demonstrated that the use of NOMA in downlink has superior performance in terms of throughput, whereas the use in uplink outperforms OMA techniques in terms of fairness. A distinctive feature of NOMA is the presence of excessive multiple-access interference due to the case of usage of power domain to multiplex signals, thus the functional implementation of NOMA implies Successive Interference Cancelation (SIC) to combat this interference. Therefore, SIC design becomes the main point in the effectiveness of NOMA systems. On the other hand, hybrid schemes, NOMA/OMA, have been recently proposed to reduce the drawbacks of pure NOMA systems. However, in these schemes, it becomes necessary to distinguish NOMA and OMA users. Cognitive Radio techniques turn to be a good option to effectively separate NOMA/OMA users as well as to distinguish NOMA users. In this chapter, a brief overview of NOMA techniques related to Cognitive Radio technology (CR-NOMA) and SIC design reported in the literature is presented. Also, new findings about NOMA/OMA users’ recognition are described.
Highlights
To cover 5G and Generation Networks (NGN) main requirements, such as better coverage, bandwidth, reliability, and spectrum efficiency, many techniques have been proposed
We explore how effective the Extended Kalman Filter (EKF)-based non-linear filtering (IMM and 2MM) can be, when it is applied to OFDMA(OMA) signals under the influence of AWGN and Non-Orthogonal Multiple Access (NOMA) interference
It was shown earlier that because of the numerous impairments and distortions that take place in Double Selective channels, it is rather “hard” to obtain high values for characteristics, such as noise immunity and spectral efficiency in Doubly Selective Channels which usually appears in 5G and beyond networks for information transmission from High -Speed -Vehicles (HSV) terminals
Summary
To cover 5G and Generation Networks (NGN) main requirements, such as better coverage, bandwidth, reliability, and spectrum efficiency, many techniques have been proposed. After user’s decoding, they are directed to corresponding demodulation blocks of the different services to whom they correspond Both methods are shown to be essentially invariant to the CSI and their processing algorithms are fast and quasioptimum Extended Kalman Filter (EKF) might give additional “benefits” for the Chaos-based filtering approach [11] (see below). The physical nature of the Doubly Selective Channels (high selectivity in both domains) shifts signals to an “almost” Gaussian random process, no matter what service they belong to This matter gives additional “degrees of freedom” in choosing the concrete filtering algorithms for filtering: Standard Kalman Filtering (SKF), EKF, etc. The rest of the chapter is organized as follows: In Section 1 a brief overview of SIC-NOMA techniques reported in the literature is presented, Section 2 is entirely dedicated to explain Chaos-based filtering algorithms applied both to OMA signals and for the set of multiuser interferers. The way of the calculus of the characteristics of the hypothesis testing is presented as well
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