Generalized Newton's Method based on Graphical Derivatives

This paper concerns developing a numerical method of the Newton type to solve systems of nonlinear equations described by nonsmooth continuous functions. We propose and justify a new generalized Newton algorithm based on graphical derivatives, which have never been used to derive a Newton-type method for solving nonsmooth equations. Based on advanced techniques of variational analysis and generalized differentiation, we establish the well-posedness of the algorithm, its local superlinear convergence, and its global convergence of the Kantorovich type. Our convergence results hold with no semismoothness assumption, which is illustrated by examples. The algorithm and main results obtained in the paper are compared with well-recognized semismooth and $B$-differentiable versions of Newton's method for nonsmooth Lipschitzian equations

Performance analysis of power-splitting relaying protocol in SWIPT based cooperative NOMA systems

This paper investigates a relay assisted simultaneous wireless information and power transfer (SWIPT) for downlink in cellular systems. Cooperative non-orthogonal multiple access (C-NOMA) is employed along with power splitting protocol to enable both energy harvesting (EH) and information processing (IP). A downlink model consists of a base station (BS) and two users is considered, in which the near user (NU) is selected as a relay to forward the received signal from the BS to the far user (FU). Maximum ratio combining is then employed at the FU to combine both the signals received from the BS and NU. Closed form expressions of outage probability, throughput, ergodic rate and energy efficiency (EE) are firstly derived for the SWIPT based C-NOMA considering both scenarios of with and without direct link between the BS and FU. The impacts of EH time, EH efficiency, power-splitting ratio, source data rate and distance between different nodes on the performance are then investigated. The simulation results show that the C-NOMA with direct link achieves an outperformed performance over C-NOMA without direct link. Moreover, the performance of C-NOMA with direct link is also higher than that for OMA. Specifically, (1) the outage probability for C-NOMA in both direct and relaying link cases is always lower than that for OMA. (2) the outage probability, throughput and ergodic rate vary according to β, (3) the EE of both users can obtain in SNR range of from -10 to 5 dB and it decreases linearly as SNR increases. Numerical results are provided to verify the findings

On the power-splitting relaying protocol for SWIPT with multiple UAVs in downlink NOMA-IoT networks

Unmanned aerial vehicle (UAV) communication and non-orthogonal multiple access (NOMA) are two promising technologies for wireless 5G networks and beyond. The UAVs can be used as flying base stations to form line-of-sight communication links to the Internet of things devices (IDs) and to enhance the performance of usual terrestrial cellular networks. Moreover, the UAVs can also be deployed as flying relay nodes for forwarding data from a base station (BS) to the IDs. On the other hand, non-orthogonal resource sharing for many concurrent users is exploited in NOMA, thus improving spectrum efficiency (SE) and supporting massive connections. The NOMA combined with energy harvesting (EH) in an amplify-and-forward (AF) with cooperative UAV systems is researched. Specifically, the UAVs act as rotary-wing relays to forward data from the BSs to two IDs. This paper focuses on the analysis of outage probabilities (OPs), system throughput, and energy efficiency (EE) for two IDs. Besides, we also do the asymptotic analysis of OPs at high signal-to-noise ratios (SNRs). Furthermore, this paper also inspects the impacts of the UAV-based relaying on the OP, system throughput, and EE of the proposed NOMA scheme. The derived asymptotic expansions show that the suggested model can enhance user fairness and the analytical results match the simulation results

Power splitting versus time switching based cooperative relaying protocols for SWIPT in NOMA systems

Non-orthogonal multiple access (NOMA) along with wireless power transfer have recently been adapted to cooperative communications for 5G and beyond wireless networks. This paper investigates NOMA based cooperative relaying wireless- powered networks (CRWPNs) where, decode-and-forward (DF) relaying and successive interference cancellation are both employed at a wireless-powered intermediate node. For simultaneous wireless information and power transfer (SWIPT), power-splitting relaying (PSR) and time switching-based relaying (TSR) protocols are considered in the NOMA based CRWPN. As a result, the combination of cooperative relaying power domain NOMA network and PSR and TSR protocols is proposed in this paper. The outage performance and ergodic rate of both protocols are analysed for evaluation of the impacts of energy harvesting (EH) time, EH efficiency, power splitting ratio, source data rate, and the distance between the nodes. In addition, two delay limited transmission (DLT) and delay tolerant transmission (DTT) modes are considered in this network model to investigate the throughput and ergodic rate of the system according to the source transmission rate. It is shown that the cooperative relaying NOMA (CRNOMA) scheme achieves a lower outage probability when compared to the conventional orthogonal multiple access (OMA) schemes. Additionally, the PSR outperforms the TSR in both low and high signal-to-noise ratio (SNR) regions in terms of throughput, ergodic rate and energy efficiency. For instance, the outage probability of CRNOMA for both PSR and TSR in SNR range of from -10 dB to +20 dB (i.e. a low SNR region) decreases gradually but not linearly. However, in SNR range of from +20 dB to +40 dB (i.e. a high SNR region), the outage probability of CRNOMA for both PSR and TSR decreases quickly. Furthermore, the energy efficiency is shown to be considerably enhanced with the employment of EH for CRNOMA. Finally, the impacts of the distance between the nodes on the performance and a comparison between two scenarios of having and without having direct links are evaluated

An overview of 5G technologies

Since the development of 4G cellular networks is considered to have ended in 2011, the attention of the research community is now focused on innovations in wireless communications technology with the introduction of the fifth-generation (5G) technology. One cycle for each generation of cellular development is generally thought to be about 10 years; so the 5G networks are promising to be deployed around 2020. This chapter will provide an overview and major research directions for the 5G that have been or are being deployed, presenting new challenges as well as recent research results related to the 5G technologies. Through this chapter, readers will have a full picture of the technologies being deployed toward the 5G networks and vendors of hardware devices with various prototypes of the 5G wireless communications systems

On the performance of regenerative relaying for SWIPT in NOMA Systems

As a potential access strategy in 5G mobile communication systems, non-orthogonal multiple access (NOMA) has been proposed as a supplement to the traditional orthogonal multiple access (OMA). This paper investigates simultaneous wireless information and power transfer (SWIPT) in a NOMA relaying system. The data is transferred from a source to two end terminals among which the one close to the source acts as a relay employing decode-and-forward protocol to assist the far-end one. In order to simultaneously harvest the energy and information processing at relay node, power-splitting relaying (PSR) and time switching-based relaying (TSR) protocols are sequentially considered. Outage probability and ergodic rate of both protocols are firstly analyzed to realize the impacts of various parameters including energy harvesting time, power splitting ratio, energy harvesting efficiency, source data rate, and the distance between the source and the relay node. Numerical results are then provided to validate the analytical findings. It is shown that the PSR outperforms the TSR at normal SNR regime in terms of throughput and ergodic rate

Optimizing energy efficiency for supporting near-cloud access region of UAV based NOMA networks in IoT systems

Non-orthogonal multiple access (NOMA) and unmanned aerial vehicle (UAV) are two promising technologies for wireless the fifth generation (5G) networks and beyond. On one hand, UAVs can be deployed as flying base stations to build line-of-sight (LoS) communication links to two ground users (GUs) and to improve the performance of conventional terrestrial cellular networks. On the other hand, NOMA enables the share of an orthogonal resource to multiple users simultaneously, thus improving the spectral efficiency and supporting massive connectivities. This paper presents two protocols namely cloud-base central station (CCS) based power-splitting protocol (PSR) and time-switching protocol (TSR), for simultaneously wireless information and power transmission (SWIPT) at UAV employed in power domain NOMA based multi-tier heterogeneous cloud radio access network (H-CRAN) of internet of things (IoT) system. The system model with k types of UAVs and two users in which the CCS manages the entire H-CRAN and operates as a central unit in the cloud is proposed in our work. Closed-form expressions of throughput and energy efficiency (EE) for UAVs are derived. In particular, the EE is determined for the impacts of power allocation at CCS, various UAV types and channel environment. The simulation results show that the performance for CCS-based PSR outperforms that for CCS-based TSR for the impacts of power allocation at the CCS. On contrary, the TSR protocol has a higher EE than the PSR in cases of the impact of various UAV types and channel environment. The analytic results match Monte Carlo simulations

A power-splitting relaying protocol for wireless energy harvesting and information processing in NOMA systems

Non-orthogonal multiple access (NOMA) along with cooperative communications have been recognized as promising candidates for the fifth generation (5G) wireless networks and have attracted many researchers. Every networked device however has its own limited power supply. To this extent, this paper investigates a power-splitting relaying (PSR) protocol for wireless energy harvesting and information processing in the NOMA systems to prolong the lifetime of the energy-constrained relay nodes in wireless networks so as to avail the ambient radio-frequency (RF) signal as well as to simultaneously harvest the energy and process the information. Decode-and-forward relaying is employed at the relay node where the energy from the received RF signal is harvested and exploited to forward the information to the destination. Specifically, the outage probability and ergodic rate of the PSR protocol are derived to realize the impacts of energy harvesting time, energy harvesting efficiency, power splitting ratio, source data rate, and the distance between nodes. It is also shown that an increased energy harvesting efficiency results in an enhanced performance and an outperformance in terms of the energy efficiency is achieved with the employment of the NOMA when compared to the conventional orthogonal multiple access. Numerical results are provided to verify the findings

On the performance of NOMA in SWIPT systems with power-splitting relaying

This paper presents a decode-and-forward (DF) relaying protocol, namely power-splitting relaying (PSR), employed at relay nodes in NOMA technique. The PSR is considered for simultaneous wireless information and power transfer (SWIPT) systems. The relaying node is both energy harvesting from the received radio frequency (RF) signal and information forwarding to the destination. The outage performance and ergodic rate of the PSR are analyzed to realize the impacts of energy harvesting time, energy harvesting efficiency, power splitting ratio, source data rate, and the distance between the source and relay nodes. The simulation results show that NOMA schemes have the lower outage probability compared to the that of the conventional orthogonal multiple access (OMA) schemes at the destination node. Numerical results are provided to verify the findings

On the energy efficiency of NOMA for wireless backhaul in multi-tier heterogeneous CRAN

This paper addresses the problem of wireless backhaul in a multi-tier heterogeneous cellular network coordinated by a cloud-based central station (CCS), namely heterogeneous cloud radio access network (HCRAN). A non-orthogonal multiple access (NOMA) is adopted in the power domain for improved spectral efficiency and network throughput of the wireless downlink in the HCRAN. We first develop a power allocation for multiple cells of different tiers taking account of the practical power consumption of different cell types and wireless backhaul. By analysing the energy efficiency (EE) of the NOMA for the practical HCRAN downlink, we show that the power available at the cloud, the propagation environment and cell types have significant impacts on the EE performance. In particular, in a large network, the cells located at the cloud edge are shown to suffer from a very poor performance with a considerably degraded EE, which accordingly motivates us to propose an iteration algorithm for determining the maximal number of cells that can be supported in the HCRAN. The results reveal that a double number of cells can be covered in the urban environment compared to those in the shadowed urban environment and more than 1.5 times of the number of microcells can be deployed over the macrocells, while only a half number of cells can be supported when the distance between them increases threefol