scholarly journals On the Achievable Max-Min User Rates in Multi-Carrier Centralized NOMA-VLC Networks

Sensors ◽  
2021 ◽  
Vol 21 (11) ◽  
pp. 3705
Author(s):  
Omar Maraqa ◽  
Umair F. Siddiqi ◽  
Saad Al-Ahmadi ◽  
Sadiq M. Sait
Keyword(s):  
Power Allocation ◽  
Orthogonal Frequency Division Multiplexing ◽  
Multiple Access ◽  
Low Complexity ◽  
Subcarrier Allocation ◽  
Visible Light Communications ◽  
User Pairing ◽  
High Data ◽  
Access Scheme ◽  
Optimal Resource

Visible light communications (VLC) is gaining interest as one of the enablers of short-distance, high-data-rate applications, in future beyond 5G networks. Moreover, non-orthogonal multiple-access (NOMA)-enabled schemes have recently emerged as a promising multiple-access scheme for these networks that would allow realization of the target spectral efficiency and user fairness requirements. The integration of NOMA in the widely adopted orthogonal frequency-division multiplexing (OFDM)-based VLC networks would require an optimal resource allocation for the pair or the cluster of users sharing the same subcarrier(s). In this paper, the max-min rate of a multi-cell indoor centralized VLC network is maximized through optimizing user pairing, subcarrier allocation, and power allocation. The joint complex optimization problem is tackled using a low-complexity solution. At first, the user pairing is assumed to follow the divide-and-next-largest-difference user-pairing algorithm (D-NLUPA) that can ensure fairness among the different clusters. Then, subcarrier allocation and power allocation are solved iteratively through both the Simulated Annealing (SA) meta-heuristic algorithm and the bisection method. The obtained results quantify the achievable max-min user rates for the different relevant variants of NOMA-enabled schemes and shed new light on both the performance and design of multi-user multi-carrier NOMA-enabled centralized VLC networks.

The Use of Orthogonal Frequency Code Division (OFCD) Multiplexing in Wireless Mesh Network (WMN)

2010 ◽  
pp. 565-581
Author(s):  
Syed S. Rizvi ◽  
Khaled M. Elleithy ◽  
Aasia Riasat
Keyword(s):  
Orthogonal Frequency Division Multiplexing ◽  
Multiple Access ◽  
Mesh Networks ◽  
Network Capacity ◽  
Network Throughput ◽  
High Data ◽  
Wireless Mesh ◽  
Frequency Code ◽  
Access Scheme ◽  
Potential Use

In the present scenario, improvement in the data rate, network capacity, scalability, and the network throughput are some of the most serious issues in wireless mesh networks (WMN). Specifically, a major obstacle that hinders the widespread adoption of WMN is the severe limits on throughput and the network capacity. This chapter presents a discussion on the potential use of a combined orthogonal-frequency code-division (OFCD) multiple access scheme in a WMN. The OFCD is the combination of orthogonal frequency division multiplexing (OFDM) and the code division multiple access (CDMA). Since ODFM is one of the popular multi-access schemes that provide high data rates, combining the OFDM with the CDMA may yield a significant improvement in a WMN in terms of a comparatively high network throughput with the least error ration. However, these benefits demand for more sophisticated design of transmitter and receiver for WMN that can use OFCD as an underlying multiple access scheme. In order to demonstrate the potential use of OFCD scheme with the WMN, this chapter presents a new transmitter and receiver model along with a comprehensive discussion on the performance of WMN under the new OFCD multiple access scheme. The purpose of this analysis and experimental verification is to observe the performance of new transceiver with the OFCD scheme in WMN with respect to the overall network throughput, bit error rate (BER) performance, and network capacity. Moreover, in this chapter, the authors provide an analysis and comparison of different multiple access schemes such as FDMA, TDMA, CDMA, OFDM, and the new OFCD.

scholarly journals An Efficient Resource Allocation for Massive MTC in NOMA-OFDMA Based Cellular Networks

Electronics ◽  
2020 ◽  
Vol 9 (5) ◽  
pp. 705
Author(s):  
Yali Wu ◽  
Shuang Zhang ◽  
Zhengxuan Liu ◽  
Xiaoshuang Liu ◽  
Jianfeng Li
Keyword(s):  
Resource Allocation ◽  
Energy Efficiency ◽  
Power Allocation ◽  
Multiple Access ◽  
Random Access ◽  
Iterative Algorithms ◽  
Low Complexity ◽  
Access Scheme ◽  
Efficient Resource ◽  
Resource Allocation Scheme

To alleviate random access congestion and support massive-connections with less energy consumption for machine-type communications (MTC) in the 5G cellular network, we propose an efficient resource allocation for massive MTC (mMTC) with hybrid non-orthogonal multiple access (NOMA)-orthogonal frequency division multiple access (OFDMA). First, a hybrid multiple access scheme, including the NOMA-based congestion-alleviating access scheme (NCAS) and OFDMA-based congestion-alleviating access scheme (OCAS), is proposed, in which the NOMA based devices coexist with OFDMA based ones. Then, aiming at maximizing the system access capacity, a traffic-aware resource blocks (RBs) allocation is investigated to optimize RBs allocation for preamble transmission and data packets transmission, as well as to optimize the RBs allocation between NCAS and OCAS for the RBs usage efficiency improvement. Next, aiming at the problem of high computational complexity and improving energy efficiency in hybrid NOMA-OFDMA based cellular M2M communications, this paper proposes an improved low complexity power allocation algorithm. The feasibility conditions of power allocation solution under the maximum transmit power constraints and quality of service (QoS) requirements of the devices is investigated. The original non-convex optimization problem is solved under the feasibility conditions by two iterative algorithms. Finally, a device clustering scheme is proposed based on the channel gain difference and feasible condition of power allocation solution, by which NOMA based devices and OFDMA based devices can be determined. Simulation results show that compared with non-orthogonal random access and transmission (NORA-DT), the proposed resource allocation scheme for hybrid NOMA-OFDMA systems can efficiently improve the performance of access capacity and energy efficiency.

Mobility aware of WDM-based CMO OFDM communication system

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Saad M. Hardan ◽  
Ayad A. Abdulkafi ◽  
Saadi Hamad Thalij ◽  
Sherine S. Jumaah
Keyword(s):  
Wavelength Division Multiplexing ◽  
Orthogonal Frequency Division Multiplexing ◽  
High Speed ◽  
Light Emitting Diode ◽  
Access Point ◽  
Mobile Users ◽  
Visible Light Communications ◽  
Optical Wireless Communications ◽  
High Data ◽  
The Impact

Abstract The continued increase in several mobile applications forces to replace existing limited spectrum indoor radio frequency wireless connections with high-speed ones. Visible light communications (VLC) technology has gained prominence in the development of high data rate transmission for fifth-generation networks. In optical wireless communications, light-emitting diode (LED) transmitters are used in applications that desire mobility as LED divergence enables larger coverage. Since each VLC access point covers a small area, handovers of mobile users are inevitable. Wavelength division multiplexing (WDM) can be used in VLC systems to tackle the above issue and to meet the increasing demand for indoor connectivity with high bit rates. In this paper, a new system architecture for WDM with coded modulated optical in orthogonal frequency division multiplexing (OFDM) VLC system in conjunction with red, green, blue, and yellow (RGBY) LEDs is proposed to reduce the impact of random receiver orientation of indoor mobile users over VLC downlink channels and improves the system’s bit-error-rate (BER) performance. Simulation results show that the proposed method is not affected by the user’s mobility and hence it performs better than other approaches, in terms of BER for all scenarios and at all positions. This study reveals that using WDM-OFDM-VLC with RGBY LEDs to construct a VLC system is very promising.

User Pairing and Power Allocation for Downlink Non-Orthogonal Multiple Access

2016 ◽  
Author(s):  
Jingrui Guo ◽  
Xiangyang Wang ◽  
Jingwen Yang ◽  
Jianhai Zheng ◽  
Bingqiang Zhao
Keyword(s):  
Power Allocation ◽  
Multiple Access ◽  
User Pairing

scholarly journals Novel Resource Allocation Techniques for Downlink Non-Orthogonal Multiple Access Systems

2020 ◽  
Vol 10 (17) ◽  
pp. 5892 ◽  
Author(s):  
Zuhura J. Ali ◽  
Nor K. Noordin ◽  
Aduwati Sali ◽  
Fazirulhisyam Hashim ◽  
Mohammed Balfaqih
Keyword(s):  
Resource Allocation ◽  
Energy Efficiency ◽  
Power Allocation ◽  
Multiple Access ◽  
High Capacity ◽  
Kkt Conditions ◽  
Optimal Power Allocation ◽  
User Pairing ◽  
Optimal Power ◽  
Sum Rate

Non-orthogonal multiple access (NOMA) plays an important role in achieving high capacity for fifth-generation (5G) networks. Efficient resource allocation is vital for NOMA system performance to maximize the sum rate and energy efficiency. In this context, this paper proposes optimal solutions for user pairing and power allocation to maximize the system sum rate and energy efficiency performance. We identify the power allocation problem as a nonconvex constrained problem for energy efficiency maximization. The closed-form solutions are derived using Karush–Kuhn–Tucker (KKT) conditions for maximizing the system sum rate and the Dinkelbach (DKL) algorithm for maximizing system energy efficiency. Moreover, the Hungarian (HNG) algorithm is utilized for pairing two users with different channel condition circumstances. The results show that with 20 users, the sum rate of the proposed NOMA with optimal power allocation using KKT conditions and HNG (NOMA-PKKT-HNG) is 6.7% higher than that of NOMA with difference of convex programming (NOMA-DC). The energy efficiency with optimal power allocation using DKL and HNG (NOMA-PDKL-HNG) is 66% higher than when using NOMA-DC.

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