Performance enhancement solutions in wireless communication networks

In this dissertation thesis, we study the new relaying protocols for different wireless network systems. We analyze and evaluate an efficiency of the transmission in terms of the outage probability over Rayleigh fading channels by mathematical analyses. The theoretical analyses are verified by performing Monte Carlo simulations. First, we study the cooperative relaying in the Two-Way Decode-and-Forward (DF) and multi-relay DF scheme for a secondary system to obtain spectrum access along with a primary system. In particular, we proposed the Two-Way DF scheme with Energy Harvesting, and the Two-Way DF Non-orthogonal Multiple Access (NOMA) scheme with digital network coding. Besides, we also investigate the wireless systems with multi-relay; the best relay selection is presented to optimize the effect of the proposed scheme. The transmission protocols of the proposed schemes EHAF (Energy Harvesting Amplify and Forward) and EHDF (Energy Harvesting Decode and Forward) are compared together in the same environment and in term of outage probability. Hence, with the obtained results, we conclude that the proposed schemes improve the performance of the wireless cooperative relaying systems, particularly their throughput. Second, we focus on investigating the NOMA technology and proposing the optimal solutions (protocols) to advance the data rate and to ensure the Quality of Service (QoS) for the users in the next generation of wireless communications. In this thesis, we propose a Two-Way DF NOMA scheme (called a TWNOMA protocol) in which an intermediate relay helps two source nodes to communicate with each other. Simulation and analysis results show that the proposed protocol TWNOMA is improving the data rate when comparing with a conventional Two-Way scheme using digital network coding (DNC) (called a TWDNC protocol), Two-Way scheme without using DNC (called a TWNDNC protocol) and Two-Way scheme in amplify-and-forward(AF) relay systems (called a TWANC protocol). Finally, we considered the combination of the NOMA and physical layer security (PLS) in the Underlay Cooperative Cognitive Network (UCCN). The best relay selection strategy is investigated, which uses the NOMA and considers the PLS to enhance the transmission efficiency and secrecy of the new generation wireless networks.V této dizertační práci je provedena studie nových přenosových protokolů pro různé bezdrátové síťové systémy. S využitím matematické analýzy jsme analyzovali a vyhodnotili efektivitu přenosu z hlediska pravděpodobnosti výpadku přes Rayleighův kanál. Teoretické analýzy jsou ověřeny provedenými simulacemi metodou Monte Carlo. Nejprve došlo ke studii kooperativního přenosu ve dvoucestném dekóduj-a-předej (Two-Way Decode-and-Forward–TWDF) a vícecestném DF schématu s větším počtem přenosových uzlů pro sekundární systém, kdy takto byl získán přístup ke spektru spolu s primárním systémem. Konkrétně jsme navrhli dvoucestné DF schéma se získáváním energie a dvoucestné DF neortogonální schéma s mnohonásobným přístupem (Non-orthogonal Multiple Access–NOMA) s digitálním síťovým kódováním. Kromě toho rovněž zkoumáme bezdrátové systémy s větším počtem přenosových uzlů, kde je přítomen výběr nejlepšího přenosového uzlu pro optimalizaci efektivnosti navrženého schématu. Přenosové protokoly navržených schémat EHAF (Energy Harvesting Amplify and Forward) a EHDF(Energy Harvesting Decode and Forward) jsou společně porovnány v identickém prostředí z pohledu pravděpodobnosti výpadku. Následně, na základě získaných výsledků, jsme dospěli k závěru, že navržená schémata vylepšují výkonnost bezdrátových kooperativních systémů, konkrétně jejich propustnost. Dále jsme se zaměřili na zkoumání NOMA technologie a navrhli optimální řešení (protokoly) pro urychlení datového přenosu a zajištění QoS v další generaci bezdrátových komunikací. V této práci jsme navrhli dvoucestné DF NOMA schéma (nazýváno jako TWNOMA protokol), ve kterém mezilehlý přenosový uzel napomáhá dvěma zdrojovým uzlům komunikovat mezi sebou. Výsledky simulace a analýzy ukazují, že navržený protokol TWNOMA vylepšuje dosaženou přenosovou rychlost v porovnání s konvenčním dvoucestným schématem používajícím DNC (TWDNC protokol), dvoucestným schématem bez použití DNC (TWNDNC protokol) a dvoucestným schématem v zesil-a-předej (amplify-and-forward) přenosových systémech (TWANC protokol). Nakonec jsme zvážili využití kombinace NOMA a zabezpečení fyzické vrstvy (Physical Layer Security–PLS) v podpůrné kooperativní kognitivní síti (Underlay Cooperative Cognitive Network–UCCN). Zde je zde zkoumán výběr nejlepšího přenosového uzlu, který užívá NOMA a bere v úvahu PLS pro efektivnější přenos a zabezpečení nové generace bezdrátových sítí.440 - Katedra telekomunikační technikyvyhově

Secrecy performance of TAS/SC-based multi-hop harvest-to-transmit cognitive WSNs under joint constraint of interference and hardware imperfection

In this paper, we evaluate the secrecy performance of multi-hop cognitive wireless sensor networks (WSNs). In the secondary network, a source transmits its data to a destination via the multi-hop relaying model using the transmit antenna selection (TAS)/selection combining (SC) technique at each hop, in the presence of an eavesdropper who wants to receive the data illegally. The secondary transmitters, including the source and intermediate relays, have to harvest energy from radio-frequency signals of a power beacon for transmitting the source data. Moreover, their transmit power must be adjusted to satisfy the quality of service (QoS) of the primary network. Under the joint impact of hardware imperfection and interference constraint, expressions for the transmit power for the secondary transmitters are derived. We also derive exact and asymptotic expressions of secrecy outage probability (SOP) and probability of non-zero secrecy capacity (PNSC) for the proposed protocol over Rayleigh fading channel. The derivations are then verified by Monte Carlo simulations.Web of Science195art. no. 116

Secrecy outage probability of a NOMA scheme and impact imperfect channel state information in underlay cooperative cognitive networks

Security performance and the impact of imperfect channel state information (CSI) in underlay cooperative cognitive networks (UCCN) is investigated in this paper. In the proposed scheme, relay R uses non-orthogonal multiple access (NOMA) technology to transfer messages e1, e2 from the source node S to User 1 (U-1) and User 2 (U-2), respectively. An eavesdropper (E) is also proposed to wiretap the messages of U-1 and U-2. The transmission's security performance in the proposed system was analyzed and performed over Rayleigh fading channels. Through numerical analysis, the results showed that the proposed system's secrecy performance became more efficient when the eavesdropper node E was farther away from the source node S and the intermediate cooperative relay R. The secrecy performance of U-1 was also compared to the secrecy performance of U-2. Finally, the simulation results matched the Monte Carlo simulations well.Web of Science203art. no. 89

Principles of Physical Layer Security in Multiuser Wireless Networks: A Survey

This paper provides a comprehensive review of the domain of physical layer security in multiuser wireless networks. The essential premise of physical-layer security is to enable the exchange of confidential messages over a wireless medium in the presence of unauthorized eavesdroppers without relying on higher-layer encryption. This can be achieved primarily in two ways: without the need for a secret key by intelligently designing transmit coding strategies, or by exploiting the wireless communication medium to develop secret keys over public channels. The survey begins with an overview of the foundations dating back to the pioneering work of Shannon and Wyner on information-theoretic security. We then describe the evolution of secure transmission strategies from point-to-point channels to multiple-antenna systems, followed by generalizations to multiuser broadcast, multiple-access, interference, and relay networks. Secret-key generation and establishment protocols based on physical layer mechanisms are subsequently covered. Approaches for secrecy based on channel coding design are then examined, along with a description of inter-disciplinary approaches based on game theory and stochastic geometry. The associated problem of physical-layer message authentication is also introduced briefly. The survey concludes with observations on potential research directions in this area.Comment: 23 pages, 10 figures, 303 refs. arXiv admin note: text overlap with arXiv:1303.1609 by other authors. IEEE Communications Surveys and Tutorials, 201

Rateless codes-based secure communication employing transmit antenna selection and harvest-to-jam under joint effect of interference and hardware impairments

In this paper, we propose a rateless codes-based communication protocol to provide security for wireless systems. In the proposed protocol, a source uses the transmit antenna selection (TAS) technique to transmit Fountain-encoded packets to a destination in presence of an eavesdropper. Moreover, a cooperative jammer node harvests energy from radio frequency (RF) signals of the source and the interference sources to generate jamming noises on the eavesdropper. The data transmission terminates as soon as the destination can receive a sufficient number of the encoded packets for decoding the original data of the source. To obtain secure communication, the destination must receive sufficient encoded packets before the eavesdropper. The combination of the TAS and harvest-to-jam techniques obtains the security and efficient energy via reducing the number of the data transmission, increasing the quality of the data channel, decreasing the quality of the eavesdropping channel, and supporting the energy for the jammer. The main contribution of this paper is to derive exact closed-form expressions of outage probability (OP), probability of successful and secure communication (SS), intercept probability (IP) and average number of time slots used by the source over Rayleigh fading channel under the joint impact of co-channel interference and hardware impairments. Then, Monte Carlo simulations are presented to verify the theoretical results.Web of Science217art. no. 70

Vehicle Communication using Secrecy Capacity

We address secure vehicle communication using secrecy capacity. In particular, we research the relationship between secrecy capacity and various types of parameters that determine secrecy capacity in the vehicular wireless network. For example, we examine the relationship between vehicle speed and secrecy capacity, the relationship between the response time and secrecy capacity of an autonomous vehicle, and the relationship between transmission power and secrecy capacity. In particular, the autonomous vehicle has set the system modeling on the assumption that the speed of the vehicle is related to the safety distance. We propose new vehicle communication to maintain a certain level of secrecy capacity according to various parameters. As a result, we can expect safer communication security of autonomous vehicles in 5G communications.Comment: 17 Pages, 12 Figure

Physical Layer Security in Wireless Networks: Design and Enhancement.

PhDSecurity and privacy have become increasingly significant concerns in wireless communication networks, due to the open nature of the wireless medium which makes the wireless transmission vulnerable to eavesdropping and inimical attacking. The emergence and development of decentralized and ad-hoc wireless networks pose great challenges to the implementation of higher-layer key distribution and management in practice. Against this background, physical layer security has emerged as an attractive approach for performing secure transmission in a low complexity manner. This thesis concentrates on physical layer security design and enhancement in wireless networks. First, this thesis presents a new unifying framework to analyze the average secrecy capacity and secrecy outage probability. Besides the exact average secrecy capacity and secrecy outage probability, a new approach for analyzing the asymptotic behavior is proposed to compute key performance parameters such as high signal-to-noise ratio slope, power offset, secrecy diversity order, and secrecy array gain. Typical fading environments such as two-wave with diffuse power and Nakagami-m are taken into account. Second, an analytical framework of using antenna selection schemes to achieve secrecy is provided. In particular, transmit antenna selection and generalized selection combining are considered including its special cases of selection combining and maximal-ratio combining. Third, the fundamental questions surrounding the joint impact of power constraints on the cognitive wiretap channel are addressed. Important design insights are revealed regarding the interplay between two power constraints, namely the maximum transmit at the secondary network and the peak interference power at the primary network. Fourth, secure single carrier transmission is considered in the two-hop decode-andi forward relay networks. A two-stage relay and destination selection is proposed to minimize the eavesdropping and maximize the signal power of the link between the relay and the destination. In two-hop amplify-and-forward untrusted relay networks, secrecy may not be guaranteed even in the absence of external eavesdroppers. As such, cooperative jamming with optimal power allocation is proposed to achieve non-zero secrecy rate. Fifth and last, physical layer security in large-scale wireless sensor networks is introduced. A stochastic geometry approach is adopted to model the positions of sensors, access points, sinks, and eavesdroppers. Two scenarios are considered: i) the active sensors transmit their sensing data to the access points, and ii) the active access points forward the data to the sinks. Important insights are concluded