Recent Advances in Joint Wireless Energy and Information Transfer

In this paper, we provide an overview of the recent advances in microwave-enabled wireless energy transfer (WET) technologies and their applications in wireless communications. Specifically, we divide our discussions into three parts. First, we introduce the state-of-the-art WET technologies and the signal processing techniques to maximize the energy transfer efficiency. Then, we discuss an interesting paradigm named simultaneous wireless information and power transfer (SWIPT), where energy and information are jointly transmitted using the same radio waveform. At last, we review the recent progress in wireless powered communication networks (WPCN), where wireless devices communicate using the power harvested by means of WET. Extensions and future directions are also discussed in each of these areas.Comment: Conference submission accepted by ITW 201

Power allocation and signal labelling on physical layer security

PhD ThesisSecure communications between legitimate users have received considerable attention recently. Transmission cryptography, which introduces secrecy on the network layer, is heavily relied on conventionally to secure communications. However, it is theoretically possible to break the encryption if unlimited computational resource is provided. As a result, physical layer security becomes a hot topic as it provides perfect secrecy from an information theory perspective. The study of physical layer security on real communication system model is challenging and important, as the previous researches are mainly focusing on the Gaussian input model which is not practically implementable. In this thesis, the physical layer security of wireless networks employing finite-alphabet input schemes are studied. In particular, firstly, the secrecy capacity of the single-input single-output (SISO) wiretap channel model with coded modulation (CM) and bit-interleaved coded modulation (BICM) is derived in closed-form, while a fast, sub-optimal power control policy (PCP) is presented to maximize the secrecy capacity performance. Since finite-alphabet input schemes achieve maximum secrecy capacity at medium SNR range, the maximum amount of energy that the destination can harvest from the transmission while satisfying the secrecy rate constraint is computed. Secondly, the effects of mapping techniques on secrecy capacity of BICM scheme are investigated, the secrecy capacity performances of various known mappings are compared on 8PSK, 16QAM and (1,5,10) constellations, showing that Gray mapping obtains lowest secrecy capacity value at high SNRs. We propose a new mapping algorithm, called maximum error event (MEE), to optimize the secrecy capacity over a wide range of SNRs. At low SNR, MEE mapping achieves a lower secrecy rate than other well-known mappings, but at medium-to-high SNRs MEE mapping achieves a significantly higher secrecy rate over a wide range of SNRs. Finally, the secrecy capacity and power allocation algorithm (PA) of finite-alphabet input wiretap channels with decode-and-forward (DF) relays are proposed, the simulation results are compared with the equal power allocation algorithm

Transmitter Optimization Techniques for Physical Layer Security

Information security is one of the most critical issues in wireless networks as the signals transmitted through wireless medium are more vulnerable for interception. Although the existing conventional security techniques are proven to be safe, the broadcast nature of wireless communications introduces different challenges in terms of key exchange and distributions. As a result, information theoretic physical layer security has been proposed to complement the conventional security techniques for enhancing security in wireless transmissions. On the other hand, the rapid growth of data rates introduces different challenges on power limited mobile devices in terms of energy requirements. Recently, research work on wireless power transfer claimed that it has been considered as a potential technique to extend the battery lifetime of wireless networks. However, the algorithms developed based on the conventional optimization approaches often require iterative techniques, which poses challenges for real-time processing. To meet the demanding requirements of future ultra-low latency and reliable networks, neural network (NN) based approach can be employed to determine the resource allocations in wireless communications. This thesis developed different transmission strategies for secure transmission in wireless communications. Firstly, transmitter designs are focused in a multiple-input single-output simultaneous wireless information and power transfer system with unknown eavesdroppers. To improve the performance of physical layer security and the harvested energy, artificial noise is incorporated into the network to mask the secret information between the legitimate terminals. Then, different secrecy energy efficiency designs are considered for a MISO underlay cognitive radio network, in the presence of an energy harvesting receiver. In particular, these designs are developed with different channel state information assumptions at the transmitter. Finally, two different power allocation designs are investigated for a cognitive radio network to maximize the secrecy rate of the secondary receiver: conventional convex optimization framework and NN based algorithm

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

Secure Two-Way Transmission via Wireless-Powered Untrusted Relay and External Jammer

In this paper, we propose a two-way secure communication scheme where two transceivers exchange confidential messages via a wireless powered untrusted amplify-and-forward (AF) relay in the presence of an external jammer. We take into account both friendly jamming (FJ) and Gaussian noise jamming (GNJ) scenarios. Based on the time switching (TS) architecture at the relay, the data transmission is done in three phases. In the first phase, both the energy-starved nodes, the untrustworthy relay and the jammer, are charged by non-information radio frequency (RF) signals from the sources. In the second phase, the two sources send their information signals and concurrently, the jammer transmits artificial noise to confuse the curious relay. Finally, the third phase is dedicated to forward a scaled version of the received signal from the relay to the sources. For the proposed secure transmission schemes, we derive new closed-form lower-bound expressions for the ergodic secrecy sum rate (ESSR) in the high signal-to-noise ratio (SNR) regime. We further analyze the asymptotic ESSR to determine the key parameters; the high SNR slope and the high SNR power offset of the jamming based scenarios. To highlight the performance advantage of the proposed FJ, we also examine the scenario of without jamming (WoJ). Finally, numerical examples and discussions are provided to acquire some engineering insights, and to demonstrate the impacts of different system parameters on the secrecy performance of the considered communication scenarios. The numerical results illustrate that the proposed FJ significantly outperforms the traditional one-way communication and the Constellation rotation approach, as well as our proposed benchmarks, the two-way WoJ and GNJ scenarios.Comment: 14 pages, 6 figures, Submitted to IEEE Transactions on Vehicular Technolog

Transmit optimization techniques for physical layer security

PhD ThesisOver the last several decades, reliable communication has received considerable attention in the area of dynamic network con gurations and distributed processing techniques. Traditional secure communications mainly considered transmission cryptography, which has been developed in the network layer. However, the nature of wireless transmission introduces various challenges of key distribution and management in establishing secure communication links. Physical layer security has been recently recognized as a promising new design paradigm to provide security in wireless networks in addition to existing conventional cryptographic methods, where the physical layer dynamics of fading channels are exploited to establish secure wireless links. On the other hand, with the ever-increasing demand of wireless access users, multi-antenna transmission has been considered as one of e ective approaches to improve the capacity of wireless networks. Multi-antenna transmission applied in physical layer security has extracted more and more attentions by exploiting additional degrees of freedom and diversity gains. In this thesis, di erent multi-antenna transmit optimization techniques are developed for physical layer secure transmission. The secrecy rate optimization problems (i.e., power minimization and secrecy rate maximization) are formulated to guarantee the optimal power allocation. First, transmit optimization for multiple-input single-output (MISO) secrecy channels are developed to design secure transmit beamformer that minimize the transmit power to achieve a target secrecy rate. Besides, the associated robust scheme with the secrecy rate outage probability constraint are presented with statistical channel uncertainty, where the outage probability constraint requires that the achieved secrecy rate exceeds certain thresholds with a speci c probability. Second, multiantenna cooperative jammer (CJ) is presented to provide jamming services that introduces extra interference to assist a multiple-input multipleoutput (MIMO) secure transmission. Transmit optimization for this CJaided MIMO secrecy channel is designed to achieve an optimal power allocation. Moreover, secure transmission is achieved when the CJ introduces charges for its jamming service based on the amount of the interference caused to the eavesdropper, where the Stackelberg game is proposed to handle, and the Stackelberg equilibrium is analytically derived. Finally, transmit optimization for MISO secure simultaneous wireless information and power transfer (SWIPT) is investigated, where secure transmit beamformer is designed with/without the help of arti - cial noise (AN) to maximize the achieved secrecy rate such that satisfy the transmit power budget and the energy harvesting (EH) constraint. The performance of all proposed schemes are validated by MATLAB simulation results