Non-Orthogonal Multiple Access (NOMA) for 5G Networks

In this chapter, we explore the concept of non-orthogonal multiple access (NOMA) scheme for the future radio access for 5G. We first provide the fundamentals of the technique for both downlink and uplink channels and then discuss optimizing the network capacity under fairness constraints. We further discuss the impacts of imperfect receivers on the performance of NOMA networks. Finally, we discuss the spectral efficiency (SE) of the networks that employ NOMA with its relations with energy efficiency (EE). We demonstrate that the networks with NOMA outperform other multiple access schemes in terms of sum capacity, EE and SE

Unipolar-pulse amplitude modulation frequency division multiplexing for visible light communication systems

Asymmetrically clipped optical orthogonal frequency division multiplexing (ACO-OFDM) has been proposed in visible light communication (VLC) systems to overcome the dc-biased optical OFDM power consumption issue at the cost of the available electrical spectral efficiency. Due to the implementation of inverse fast Fourier transform, all the optical OFDM schemes including ACO-OFDM suffer from large peak-to-average power ratio (PAPR), which degrades the performance in VLC systems as the light-emitting diodes used as the transmitter have a limited optical power-current linear range. To address the PAPR issue in ACO-OFDM, we introduce a unipolar-pulse amplitude modulation frequency division multiplexing by adopting the single carrier frequency division multiple access (SC-FDMA). This is achieved by considering a PAM as an SC-FDMA data symbol and inserting a conjugate copy of the middle and first SC-FDMA FFT output subcarriers after the middle and last subcarriers, respectively. Simulation results show that, for the proposed scheme, the PAPR is 3.6 dB lower compared with ACO-OFDM. The PAPR improvement is further analyzed with the simulation results demonstrating that the proposed scheme offers 2.5 dB more average transmitted power compared to ACO-OFDM

Neuro-Spike Communications with Multiple Synapses under Inter-Neuron Interference [Article]

https://ieeexplore.ieee.org/document/8409926The nervous system is a complex intra-body communication system, called neuro-spike communications, for transferring vital information throughout the body. This system consists of unreliable neural components like axon and synapses. The nervous system can deal with the unreliability of its components by making use of multiple synapses. In this paper, we analyze the performance of neuro-synaptic channels consisting of multiple synapses. It is assumed that synaptic channels are subject to synaptic noise, random vesicle release, and inter-neuron interference. The optimal detection for two cases of multiple cooperative synapses and multiple interfering synapses is investigated. The closed-form expressions of the probability density function of variable quantal amplitude are derived that is used to calculate the probability of detection error

Hard and Soft Switching for Indoor Hybrid VLC/RF Systems [Article]

Article "Hard and Soft Switching for Indoor Hybrid VLC/RF Systems" in pdf formatThe paper is dedicated to analysis of hard switching (HS) and soft switching (SS) methods for hybrid VLC/RF systems. VLC communication is well known for its efficient high data rate service for short range wireless communication, however it relies on the condition of line of sight link. Its counterpart, RF communication, is easy to implement and widely available in most places. In this work, we consider hybrid VLC/RF system which takes advantages of both links by implementing HS and SS methods. In HS, either VLC or RF, whichever has higher throughput, is selected. In SS, on the other hand, data is transmitted though both links simultaneously however the total available electrical power is shared between the links. We demonstrate that SS outperforms HS when the power is optimally shared between the VLC and RF links

GPU accelerated PIC and SIC for OFDM-NOMA

Non-orthogonal multiple access (NOMA) is a candidate multiple access scheme for the fifth-generation (5G) cellular networks. In NOMA systems, all users operate at the same frequency and time, which poses a challenge in the decoding process at the receiver side. In this work, the two most popular receiver structures, successive interference cancellation (SIC) and parallel interference cancellation (PIC) receivers, for NOMA reverse channel are implemented on a graphics processing unit (GPU) and compared. Orthogonal frequency division multiplexing (OFDM) is considered. The high computational complexity of interference cancellation receivers undermines the potential deployment of NOMA systems. GPU acceleration, however, challenges this weakness, and our numerical results show speedups of about from 75–220-times as compared to a multi-thread implementation on a central processing unit (CPU). SIC and PIC multi-thread execution time on different platforms reveals the potential of GPU in wireless communications. Furthermore, the successful decoding rates of the SIC and PIC are evaluated and compared in terms of bit error rate