Physical Layer Service Integration in 5G: Potentials and Challenges

High transmission rate and secure communication have been identified as the key targets that need to be effectively addressed by fifth generation (5G) wireless systems. In this context, the concept of physical-layer security becomes attractive, as it can establish perfect security using only the characteristics of wireless medium. Nonetheless, to further increase the spectral efficiency, an emerging concept, termed physical-layer service integration (PHY-SI), has been recognized as an effective means. Its basic idea is to combine multiple coexisting services, i.e., multicast/broadcast service and confidential service, into one integral service for one-time transmission at the transmitter side. This article first provides a tutorial on typical PHY-SI models. Furthermore, we propose some state-of-the-art solutions to improve the overall performance of PHY-SI in certain important communication scenarios. In particular, we highlight the extension of several concepts borrowed from conventional single-service communications, such as artificial noise (AN), eigenmode transmission etc., to the scenario of PHY-SI. These techniques are shown to be effective in the design of reliable and robust PHY-SI schemes. Finally, several potential research directions are identified for future work.Comment: 12 pages, 7 figure

Artificial Noise-Aided Biobjective Transmitter Optimization for Service Integration in Multi-User MIMO Gaussian Broadcast Channel

This paper considers an artificial noise (AN)-aided transmit design for multi-user MIMO systems with integrated services. Specifically, two sorts of service messages are combined and served simultaneously: one multicast message intended for all receivers and one confidential message intended for only one receiver and required to be perfectly secure from other unauthorized receivers. Our interest lies in the joint design of input covariances of the multicast message, confidential message and artificial noise (AN), such that the achievable secrecy rate and multicast rate are simultaneously maximized. This problem is identified as a secrecy rate region maximization (SRRM) problem in the context of physical-layer service integration. Since this bi-objective optimization problem is inherently complex to solve, we put forward two different scalarization methods to convert it into a scalar optimization problem. First, we propose to prefix the multicast rate as a constant, and accordingly, the primal biobjective problem is converted into a secrecy rate maximization (SRM) problem with quality of multicast service (QoMS) constraint. By varying the constant, we can obtain different Pareto optimal points. The resulting SRM problem can be iteratively solved via a provably convergent difference-of-concave (DC) algorithm. In the second method, we aim to maximize the weighted sum of the secrecy rate and the multicast rate. Through varying the weighted vector, one can also obtain different Pareto optimal points. We show that this weighted sum rate maximization (WSRM) problem can be recast into a primal decomposable form, which is amenable to alternating optimization (AO). Then we compare these two scalarization methods in terms of their overall performance and computational complexity via theoretical analysis as well as numerical simulation, based on which new insights can be drawn.Comment: 14 pages, 5 figure

Comparative Analysis of NOMA and OMA Schemes: GSVD-based NOMA Systems and the Role of Mobile Edge Computing, Journal of Telecommunications and Information Technology, 2023, nr 3

This paper presents a comprehensive study that examines the fundamental concept of the non-orthogonal multiple access (NOMA) scheme and provides its detailed comparison with the orthogonal multiple access (OMA) technique. Furthermore, the paper explores the application of the generalized singular value decomposition (GSVD) method in conjunction with NOMA, accompanied by a detailed review of GSVD-based NOMA systems. This study also introduces the concept of mobile edge computing (MEC) and extensively discusses its key parameters. Furthermore, a comprehensive analysis of NOMA MEC is presented, shedding light on its potential advantages and challenges. The aims of this study are to provide a comprehensive understanding of the aforementioned topics and contribute to the advancement of MIMO-NOMA systems

Physical Layer Security for Visible Light Communication Systems:A Survey

Due to the dramatic increase in high data rate services and in order to meet the demands of the fifth-generation (5G) networks, researchers from both academia and industry are exploring advanced transmission techniques, new network architectures and new frequency spectrum such as the visible light spectra. Visible light communication (VLC) particularly is an emerging technology that has been introduced as a promising solution for 5G and beyond. Although VLC systems are more immune against interference and less susceptible to security vulnerabilities since light does not penetrate through walls, security issues arise naturally in VLC channels due to their open and broadcasting nature, compared to fiber-optic systems. In addition, since VLC is considered to be an enabling technology for 5G, and security is one of the 5G fundamental requirements, security issues should be carefully addressed and resolved in the VLC context. On the other hand, due to the success of physical layer security (PLS) in improving the security of radio-frequency (RF) wireless networks, extending such PLS techniques to VLC systems has been of great interest. Only two survey papers on security in VLC have been published in the literature. However, a comparative and unified survey on PLS for VLC from information theoretic and signal processing point of views is still missing. This paper covers almost all aspects of PLS for VLC, including different channel models, input distributions, network configurations, precoding/signaling strategies, and secrecy capacity and information rates. Furthermore, we propose a number of timely and open research directions for PLS-VLC systems, including the application of measurement-based indoor and outdoor channel models, incorporating user mobility and device orientation into the channel model, and combining VLC and RF systems to realize the potential of such technologies

Journal of Telecommunications and Information Technology, 2022, nr 3

kwartalni

Network Management and Decision Making for 5G Heterogeneous Networks

Heterogeneous networks (HetNets) will form an integral part of future cellular communications. With the proper management of network resources and decisions, the coexistence of small cells with macro base stations will improve coverage, data rate and quality of service for users. This thesis investigates critical issues that will arise in HetNets. The first half of this thesis studies major consequences of the disparity between HetNet tier transmit powers, namely that of interference and load balancing. To reduce the effects of harmful interference to small cell users arising from powerful macro transmissions, we first design a precoding matrix in the form of a generalized inverse, which, unlike conventional precoding methods, allows the base station to target a user specifically to reduce its own interference to that user. Even with a transmit power constraint, the affected user can achieve significant improvement in its interference reduction at the slightly compromise of existing macro users. Next, we study load balancing by showing the benefits of a dynamic biasing function for cell range expansion over a static bias value. Our findings indicate that a dynamic bias is a more intuitive way to prevent small cell overloading, and that associating closest users first is a preferred association order. We conclude our study into load balancing by proposing a new notion of network balance. We describe how network balance is different to user fairness, and subsequently define a new metric called the network balance index which measures the deviation of the actual base station load distribution with the expected load distribution. We show using an algorithm that the network balance index is more useful than fairness in improving sum rate for clustered networks. The second half of this thesis explores more advanced user-centric issues for HetNets. Chapter 5 proposes a user association scheme that achieves high fairness, and considers user association behaviour with network dynamics. In order to reduce the computation needed to re-associate a large network, we study the probabilities that each user will have to switch associations when a user or base station enters or leaves. In the process, we find that a shrinking network has more effect on user association than a growing one. Finally, Chapter 6 extends the conventional idea of HetNets to include device-to-device (D2D) communications. We propose a D2D decision making framework that more suitably selects D2D modes for potential D2D pairs by using a two-stage criteria that leads to fewer incorrect D2D mode selections. Once a suitable D2D mode is selected, we demonstrate how to determine optimal or near-optimal power and resource parameters for each mode in order to maximize sum rate. We present a geometric approach to solving the co-channel power control problem, and closed form expressions where possible for orthogonal frequency allocation. Our comprehensive study validates the potential for D2D integration in future cellular communications. The proposed techniques and insights gained from this thesis aims to illustrate how networks can be better managed and improve their decision making processes in order to successfully serve future users