51 research outputs found
A survey and taxonomy on nonorthogonal multiple-access schemes for 5G networks
Copyright © 2017 John Wiley & Sons, Ltd. The intensity in the requirements of Internet of Things and mobile internet makes the efficiency of fifth-generation (5G) wireless communications very challenging to achieve. Accomplishing the drastically increasing demand of massive connectivity and high spectral efficiency is a strenuous task. Because of the very large number of devices, 5G wireless communication systems are inevitable to satisfy the traffic requirements. Recently, nonorthogonal multiple-access (NOMA) schemes are immensely being explored to address the challenges in 5G, which include effective bandwidth utilization, support for a massive number of devices, and low latency. This paper provides the reader with a holistic view of multiple-access schemes, methods, and strategies for optimization in NOMA. First, we discuss the taxonomy of multiple-access schemes in the literature; then, we provide a detailed discussion of objectives, constraints, problem types, and solution approaches for NOMA. This paper also discusses the decoding methods and key performance indicators used in NOMA. Finally, we outline future research directions
Waveform Design for 5G and Beyond
5G is envisioned to improve major key performance indicators (KPIs), such as
peak data rate, spectral efficiency, power consumption, complexity, connection
density, latency, and mobility. This chapter aims to provide a complete picture
of the ongoing 5G waveform discussions and overviews the major candidates. It
provides a brief description of the waveform and reveals the 5G use cases and
waveform design requirements. The chapter presents the main features of cyclic
prefix-orthogonal frequency-division multiplexing (CP-OFDM) that is deployed in
4G LTE systems. CP-OFDM is the baseline of the 5G waveform discussions since
the performance of a new waveform is usually compared with it. The chapter
examines the essential characteristics of the major waveform candidates along
with the related advantages and disadvantages. It summarizes and compares the
key features of different waveforms.Comment: 22 pages, 21 figures, 2 tables; accepted version (The URL for the
final version:
https://onlinelibrary.wiley.com/doi/abs/10.1002/9781119333142.ch2
State of the Art, Taxonomy, and Open Issues on Cognitive Radio Networks with NOMA
The explosive growth of mobile devices and the rapid increase of wideband
wireless services call for advanced communication techniques that can achieve
high spectral efficiency and meet the massive connectivity requirement.
Cognitive radio (CR) and non-orthogonal multiple access (NOMA) are envisioned
to be important solutions for the fifth generation wireless networks.
Integrating NOMA techniques into CR networks (CRNs) has the tremendous
potential to improve spectral efficiency and increase the system capacity.
However, there are many technical challenges due to the severe interference
caused by using NOMA. Many efforts have been made to facilitate the application
of NOMA into CRNs and to investigate the performance of CRNs with NOMA. This
article aims to survey the latest research results along this direction. A
taxonomy is devised to categorize the literature based on operation paradigms,
enabling techniques, design objectives and optimization characteristics.
Moreover, the key challenges are outlined to provide guidelines for the domain
researchers and designers to realize CRNs with NOMA. Finally, the open issues
are discussed.Comment: This paper has been accepted by IEEE Wireless Communications
Magazine. Pages 16, Figures
Secure transmission via joint precoding optimization for downlink MISO NOMA
Non-orthogonal multiple access (NOMA) is a prospective technology for radio resource constrained future mobile networks. However, NOMA users far from base station (BS) tend to be more susceptible to eavesdropping because they are allocated more transmit power. In this paper, we aim to jointly optimize the precoding vectors at BS to ensure the legitimate security in a downlink multiple-input single-output (MISO) NOMA network. When the eavesdropping channel state information (CSI) is available at BS, we can maximize the sum secrecy rate by joint precoding optimization. Owing to its non-convexity, the problem is converted into a convex one, which is solved by a second-order cone programming based iterative algorithm. When the CSI of the eavesdropping channel is not available, we first consider the case that the secure user is not the farthest from BS, and the transmit power of the farther users is maximized via joint precoding optimization to guarantee its security. Then, we consider the case when the farthest user from BS requires secure transmission, and the modified successive interference cancellation order and joint precoding optimization can be adopted to ensure its security. Similar method can be exploited to solve the two non-convex problems when the CSI is unknown. Simulation results demonstrate that the proposed schemes can improve the security performance for MISO NOMA systems effectively, with and without eavesdropping CSI
Subcarrier Filtering For Spectrally Efficient Multicarrier Modulation Schemes and Its Impact on PAPR: A Unified Approach
Multicarrier modulation (MCM) based schemes have been a major contributing factor in revolutionizing cellular networks due to their ability to overcome fading. One of the popular scheme orthogonal frequency division multiple access (OFDMA), having been part of 4G, is also adapted as part of 5G enhanced mobile broadband (eMBB). Though it has several advantages, spectral efficiency (SE) and peak to average power ratio (PAPR) have been two major concerns which have attracted lot of attention resulting in proposals of several other MCM schemes. But most of these studies have treated the two issues independently. This paper in particular studies the subcarrier filtering approach to improve the spectral efficiency of MCM scheme and its impact on the overall PAPR of such schemes. The analysis shows that the PAPR improvement is also achieved by such filters meant for spectral confinement and the simulation results validate the same provoking a unified research direction less explored till now
Performance Analysis of 5G Cooperative-NOMA for IoT-Intermittent Communication
Non-orthogonal multiple Access (NOMA) is a potential 5G era multiple-access scheme that is proposed for the future mobile Internet and IoT applications which will require enormous increase in data traffic, massive-number of devices connectivity, high spectral efficiency, low-overhead and low-latency. It utilizes the same time-slots, frequency and spreading-codes for all the users. It uses the power-domain and assign different power levels to users for multiple access. The uplink (UL) communication in the present 4G-Networks is performed by the base station (BS) that uses a request-grant mechanism in which a large-overhead and latency is produced. This issue will get more severe in upcoming 5G-Networks. For this purpose, a grant-free NOMA for UL communication, in which dynamic compressed-sensing (DCS) algorithm will perform multi-user detection (MUD) as well as data-detection is proposed. It deploys the temporal-correlation of active-user sets (AUS) in adjacent time-slots from which the estimated AUS is used as the prior-knowledge to estimate AUS in the next time-slot. For the downlink (DL) communication, the proposed system performance evaluation is performed using Rician fading-channels for Cooperative Relaying System (CRS) NOMA. The simulations results show that the proposed DCS-MUD and CRS NOMA over Rician fading-channels perform much better than the conventional CS-MUD and traditional-CRS
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