Design Of Vehicular Communication Systems Employing Physical Layer Network Coding Over Cascaded Fading Channels

Tez (Doktora) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2017Thesis (Ph.D.) -- İstanbul Technical University, Institute of Science and Technology, 2017İnsandan insana ses taşıma odaklı ikinci nesil (2nd Generation, 2G) mobil haberleşme teknolojilerinin kaydettiği başarıdan sonra telsiz iletişim alanındaki eğilimler insandan-makinaya olarak adlandırılan veri taşıma odaklı telsiz iletişim teknolojilerine (3rd Generation, 3G) doğru yönelmiştir. Bu veri taşıma odaklı iletişim konsepti ile birlikte son kullanıcılar multi-media mesajlaşma, internet erişimi, e-ticaret ve video paylaşımı gibi çok çeşitli telsiz iletişim servislerine kavuşma imkanı buldular. Telsiz iletişimdeki başarılı ve hızlı ilerlemenin bir sonucu olarak günümüzde bu alanda yapılan araştırma-geliştirme çalışmalarının yönü yüksek veri iletim hızları (>100Mb/s) ve daha yüksek bant-verimliliği (>10b/s) gerektiren makineden-makineye (Mactine-to-Machine, M2M) telsiz iletişime doğru yönelmiş bulunmaktadır. M2M telsiz iletişiminde bir araştırma/uygulama alanı araçtan-nesnelere (Vehicle-to-things, V2X) haberleşmedir. Araçtan araca (Vehicle-to-Vehicle, V2V) ve araçtan yol kenarındaki baz istasyonuna (Vehicle-to-Infrastructure, V2I) olmak üzere iki haberleşme sistemini birlikte içeren V2X haberleşme sistemleri günümüzde özellikle büyük metropollerde günlük hayatı pek çok yönden olumsuz etkileyen trafik kaynaklı problemlere karşı getirdiği çözüm önerileri nedeniyle üniversitlerde teorik çalışmalar yapan araştırmacıların yanı sıra, resmi kurumların, standartları belirleyen organizasyonların ve özellille otomotiv ve bilişim endüstrisindeki şirketlerin gittikçe artan dikkatini çekmeyi başarmıştır. Araçlar arası haberleşme teknolojilerinin gelişimine ivme kazandıran önemli gelişmelere bakılacak olursa; 1999 yılında ABD’de Federal Communication Comission (FCC) 5.9GHz frekans bandında 75MHz’lik bir frekans bandının V2X haberleşme için kullanımını onaylamıştır. 2008 yılında ise Avrupa haberleşme standardları enstitüsü (European Telecommunication Standards Institute) yine 5.9GHz frekans bandında 30Mhz’lik bir bandın bu amaçla kullanılmasını önermiştir. FCC’nin 2003 yılında ITS (Intelligent Transportation Systems) uygulamalarında kullanılacak haberleşme birimleri için yayımladığı rapor ve talebin ardından DSRC (Dedicated Short Range Communication) olarak adlandırılan V2X haberleşme sistemlerinin standardizasyonu için çalışmalar başlamış ve 2004 yılında IEEE 802.11standardı temel alınarak geliştirilen IEEE 802.11p standardı WAVE (Wireless Access in Vehicular Environments) olarak da bilinen adıyla 2010 yılında kabul edilmiştir. Bugün artık pek çok üniversitede çeşitli araştırma grupları V2X haberleşme üzerine akademik çalışmalar yürütürken endüstriyel seviyede ise Avrupa’da örneğin büyük ölçekli Avrupa Birliği projeleri olarak CAR2CAR Communication Corsortium, Secure Vehicular Communication ve NEARCTIS yürütülmektedir. Amerika’da ise ulaştırma bakanlığının desteklediği IntelliDrive projesi ile güvenlik, mobil iletişim ve çevre koruma amaçlı hedefler doğrultusunda trafik altyapısı, araçlar ve yolcuların mobil haberleşme cihazları arasında haberleşmeyi sağlayacak bir telsiz iletişim ağı alt yapısı kurma çalışmaları sürdürülmektedir. Benzer çalışmalar Japon Otomobil Teknolojileri Araştırma Enstitüsü JARI tarafından da yapılmaktadır. Yine V2V haberleşmenin trafik güvenliğini arttırmadaki öneminin anlaşılmasından sonra lider otomobil üreticisi firmalar “Crash Avoidance Metrics Partnership” adını verdikleri proje için ortak çatı altında biraraya gelmişlerdir. Kısaca belirtilmek istenirse, telsiz iletişim alanında V2X haberleşme yeni ama oldukça önemli bir çalışma alanı olarak görülmektedir. Günümüz telsiz haberleşme teknolojilerinden biri olan araçtan araca haberleşme, trafik verimliliğini arttırma, kazaların azaltılması ve trafikte güvenli sürüş konulara çözümler sağlayacak akıllı taşıma sistemlerinin gerçeklenmesinde çekirdek teknoloji konumundadır. Hücresel haberleşme ile karşılaştırıldığında, V2V haberleşme bazı yeni zorlukları içerir. V2V haberleşme kanallarının istatistiksel özellikleri hücresel telsiz haberleşme kanallarının istatistiksel özelliklerinden farklıdır. Bu nedenle, Rayleigh, Rician ve Nakagami-m gibi iyi bilinen hücresel haberleşme kanal modelleri V2V haberleşme kanallarındaki sönümlemeyi modellemek için uygun değildir. Yapılan saha ölçümlerinden görüldüğü üzere, V2V haberleşme kanallarında kanal kazancı, hareketli kaynaklar etrafında, her biri ayrı bir işaret kaynağı gibi davranan birbirinden bağımsız saçıcı gupların oluşturduğu sanal kanalların kanal kazançlarının çarpımından meydana gelmektedir. Kanal kazancının bu çarpımsallık niteliğinden dolayı V2V haberleşme kanalları kaskad sönümlemeli kanal modeli olarak adlandırılan bir grup kanal modeli ile modellenmelidirler. V2V haberleşmede karşılaşılan zorlukların bir nedeni, gerek haberleşen araçların gerekse onların etrafındaki diğer araçların yüksek hızlardaki hareketliliği nedeniyle haberleşme ortamının çevresel olarak çok hızlı değişmesidir. Bunun yanısıra araç antenlerinin görece düşük yükseklikte olmasının da etkisiyle, özellikle yerleşim birimleri içindeki yoğun trafik şartları düşünüldüğünde, haberleşen araçlar arasında çoğu zaman doğrudan görüş olmayacaktır. Bu da iletişimin sürekliliği ve güvenilirliği açısından işbirlikli haberleşmeyi kaçınılmaz kılmaktadır. Ancak doğrudan haberleşmeye nazaran daha fazla zaman dilimi gereksinimi işbirlikli sistemlerin temel dezavantajıdır. Veri iletim hızında kayba neden olan bu dezavantajı yok etmenin bir yolu, iki haberleşme biriminin aynı zaman aralığında aynı röle üzerinden veri aktarmasına imkan tanıyan fiziksel katman ağ kodlama (Physical Layer Network Coding, PLNC) tekniğidir. Ani gelişen durumların çok sayıda kullanıcıya kısa sürede bildirilmesini gerektirecek trafik içi haberleşmede PLNC tekniği yüksek başarımlı V2V haberleşme sistemlerinin tasarımında önemli bir rol oynayacaktır. Bu tezde sunulan çalışmalar üç grupta ele alınabilir. Birinci gruptaki ilk çalışmada tek antenli tek röleli ve röle üzerinde sabit kazançlı kuvvetlendir-ve-aktar tekniği kullanılarak PLNC yapılan bir işbirlikli V2V haberleşme sistemi tasarlanmıştır. Sistemin performans analizleri kaskad Nakagami-m kanal modeli varsayımı altında yapılmış olup bu kanal modeli, araçlar arası haberleşmeye uygun olan çift Rayleigh, kaskad Rayleigh, çift Nakagami-m ve genelleştirilmiş-K kanal modellerinin yanı sıra geleneksel hücresel haberleşme kanal modellerini de kapsamaktadır. Dolayısıyla bu çalışmada elde edilen sonuçlar bu kanal modelleri için de geçerlidir. Sistemin hata performans analizleri yapılırken öncelikle uçtan-uca işaret gürültü oranına ait birikimsel olasılık dağılım fonksiyonu kapalı formda elde edilmiş, ardından bu dağılım fonksiyonu kullanılarak sistemin servis kesinti olasılığı ve çeşitli modülasyon tipleri için sembol hata olasılığı ifadeleri kapalı formda bulunmuştur. Bu analizlerin bir devamı olarak, birinci grupta yapılan ikinci çalışmada ise, kaynaklarda öz-girişim işaretinin tam olarak yok edilemediği durumlar için yine tek antenli tek röleli rölede sabit kazançlı kuvvetlendir-ve-aktar tekniği kullanılarak PLNC yapılan sistemin performans analizi kaskad ve hızlı sönümlemeli Rayleigh kanal varsayımı altında yapılmış ve sisteme ait servis kesinti olasılığı ifadesi kapalı formda elde edilerek öz girişimin sistem performansına etkileri incelenmiştir. Tezde yer alan ikinci grup çalışmada, çok girişli çok çıkışlı (multiple input multiple output, MIMO) bir V2V haberleşme sistemi tasarlanmıştır. Sistemde birden çok röle olup kaynaklar ve tüm röleler çok antenlidir. Ayrıca röleler değişken kazançlı kuvvetlendir-ve-aktar tekniği uygulayarak PLNC yapmaktadır. Bu çalışmada da kaskad Nakagami-m kanal modeli kullanıldığından elde edilen sonuçlar yukarıda bahsedilen diğer kaskad veya kaskad olmayan kanal modelleri için de geçerlidir. Burada yapılan analizler ile tüm sistemin servis kesinti performansı kaynakların ortak servis kesinti olasılıkları cinsinden ifade edilerek bu olasılık tek katlı integral formunda bulunmuştur. Ardından servis kesinti olasılığı için alt ve üst sınır ifadeleri kapalı formda elde edilmiştir. Bulunan sınır ifadeleri aracılığıyla sistemde elde edilebilecek çeşitleme derecesi, röle sayısı, kaynak ve rölelerde kullanılan anten sayıları ve kanalların kaskadlık dereceleri ve sönümleme parametrelerinin aldığı değerlere bağlı olarak sistem parametreleri cinsinden ifade edilmiştir. Tasarlanan bu sistem ile ortak anten ve röle seçimi yapılarak V2V haberleşme sistemlerinin performansının daha da iyileştirilebileceği gösterilmiştir. Tezde yapılan üçüncü çalışmada PLNC yapılan bir çok antenli çok röleli V2V haberleşme sisteminde uzay-zaman kafes kodlama tekniği kullanılarak sistem performansının daha da iyileştirilmesi sağlanmıştır. Bu amaçla öncelikle sistemin çiftsel hata olasılığı için bir üst sınır ifadesi çift Rayleigh sönümlemeli kanal varsayımı için elde edilmiştir. Daha sonra bu olasılığı en küçük yapacak kodların inşaası için yeni bir kod tasarım ölçütü türetilmiş ve bu ölçüt kullanılarak çift Rayleigh sönümlemeli kanallarda PLNC tekniği kullanan MIMO V2V haberleşme sistemler için 4 ve 8 durumlu yeni uzay-zaman kafes kodları bulunmuştur.As a current state-of-the-art in wireless communications, Vehicle-to-Vehicle (V2V) communications is the core technology to build the intelligent transportation infrastructures promising the solutions to the issues such as traffic efficiency increasing, accident reduction and safety improvements. In comparison with the cellular wireless communication, there are some new challenges within the V2V communication. The statistical properties of the V2V communication channels differ from those of the cellular channels. Thereby, well known cellular channel models such as Rayleigh, Rician and Nakagami-m are not appropriate to simulate the fading in V2V communication channels. Field measurements reveal that V2V communication channels can be modeled by a class of channel models where the gain is obtained by multiplying the gains of virtual channels produced by each individual scattering group around that behaves as an independent signal source. Due to their multiplicativity nature, V2V communication channels are named as cascaded fading channels. A major challenge in V2V communications is that the physical environment is unsettled due to the mobility of the wireless units and other vehicles around these units. Additionally, the vehicle antennas have relatively lower heights. Therefore, especially considering the traffic in urban areas, most of the time there will be no line-of-sight between the communicating vehicles. This makes cooperative communications inevitable for seamless and reliable communication among the moving vehicles. And yet, compared to non-cooperative communication, the cooperation protocols require more time slots, which results in a decrease in data transmission rate. A method to cope with this drawback is physical layer network coding (PLNC) providing the simultaneous data transmissions of the vehicles via the same relay. The PLNC method will play an important role in the design of the high performance V2V communication systems serving in the heavy traffic conditions when a large number of users need to be notified about suddenly changing situations. Studies presented in this thesis can be divided into three categories. In the first category, a cooperative V2V communication system employing PLNC using fixed gain amplify-and-forward technique is proposed and its outage and error performance analysis is investigated. Analytic results are derived under the cascaded Nakagami-m fading channel model assumption covering double Rayleigh, cascaded Rayleigh, double Nakagami-m, generalized-K and conventional cellular channel models as well. Therefore, the results obtained by this work are also valid for all these channel models. In the error performance investigation of the proposed system, first, exact cumulative density function of the end to end signal to noise ratio is derived. Then, using this cumulative density function, the exact closed-form outage probability is obtained. Then the exact closed-form symbol error rate expression for various modulation types is derived. As a continuation of this work, the performance analysis of the same system is investigated for not only cascaded but also fast fading Rayleigh channels in the presence of the self-interference. Thus the exact closed-form outage probability expression is obtained, and it is shown that the self-interference may cause the error floor in the performance of the network coded communication systems. In the second category, a multiple input multiple output (MIMO) V2V communication system is proposed. In this proposed system, all source and relay vehicles have multiple antennas while the relays employ the PLNC method using variable gain amplify-and-forward technique. The analytic results are derived for the cascaded Nakagami-m fading channels, and therefore the result of this work are held for the cascaded and non-cascaded channels, as mentioned above. Furthermore, the performance of the system is evaluated in terms of joint outage probability of the sources, and the exact outage probability expression is obtained in a single integral form while the upper and the lower bounds of the outage probability are obtained in the closed-form. Moreover, asymptotic diversity order is quantified as a function of the number of the relays, the number of the antennas at the sources and the relays, and the channel parameters which are cascading degree and fading parameter values. Within this system, it is shown that the service outage probability performance can be enhanced by employing joint antenna and relay selection. In the third category, PLNC and space-time trellis coding (STTC) techniques are combined to improve the error performance of a multi-antenna multi-relay V2V system. The upper bound expression of the pairwise error probability of the system is evaluated for double Rayleigh fading channels. Then using the upper bound expression, a novel code-design criterion is derived for cascaded fading channels. Then, by using this new criterion, a novel STTCs with 4 and 8 states are proposed for MIMO V2V PLNC systems.DoktoraPh.D

Contributions to the Performance Analysis of Intervehicular Communications Systems and Schemes

RÉSUMÉ Le but des systèmes de communication intervéhicule (Inter-Vehicle Communication – IVC) est d'améliorer la sécurité de conduite en utilisant des capteurs et des techniques de communication sans fil pour être en mesure de communiquer mutuellement sans aucune intervention extérieure. Avec l'utilisation de ces systèmes, les communications véhicule à véhicule (V2V) peuvent être plus efficaces dans la prévention des accidents et la décongestion de la circulation que si chaque véhicule travaillait individuellement. Une des solutions proposées pour les systèmes IVC est l’utilisation des systèmes de communication coopérative, qui en principe, augmentent l'efficacité spectrale et énergétique, la couverture du réseau, et réduit la probabilité de défaillance. La diversité d'antenne (entrées multiples sorties multiples « Multiple-Input Multiple-Output » ou MIMO) peut également être une alternative pour les systèmes IVC pour améliorer la capacité du canal et la diversité (fiabilité), mais en échange d’une complexité accrue. Toutefois, l'application de telles solutions est difficile, car les communications sans fil entre les véhicules sont soumises à d’importants effets d'évanouissements des canaux appelés (canaux sujets aux évanouissements de n*Rayleigh, « n*Rayleigh fading channels»), ce qui conduit à la dégradation des performances. Par conséquent, dans cette thèse, nous proposons une analyse de la performance globale des systèmes de transmission coopératifs et MIMO sur des canaux sujets aux évanouissements de n*Rayleigh. Cette analyse permettra d’aider les chercheurs pour la conception et la mise en œuvre de systèmes de communication V2V avec une complexité moindre. En particulier, nous étudions d'abord la performance de la sélection du relais de coopération avec les systèmes IVC, on suppose que la transmission via « Amplify-and-Forward» (AF) ou bien «Decode-and-Forward» (DF) est assurée par N relais pour transférer le message de la source à la destination. La performance du système est analysée en termes de probabilité de défaillance, la probabilité d'erreur de symbole, et la capacité moyenne du canal. Les résultats numériques démontrent que la sélection de relais réalise une diversité de l'ordre de (d≈mN/n) pour les deux types de relais, où m est un paramètre évanouissement de Rayleigh en cascade. Nous étudions ensuite la performance des systèmes IVC à sauts multiples avec et sans relais régénératifs. Dans cette étude, nous dérivons des expressions approximatives pour la probabilité de défaillance et le niveau d’évanouissement lorsque la diversité en réception basée sur le ratio maximum de combinaison (MRC) est employée. En outre, nous analysons la répartition de puissance pour le système sous-jacent afin de minimiser la probabilité globale de défaillance. Nous montrons que la performance des systèmes régénératifs est meilleure que celle des systèmes non régénératifs lorsque l’ordre de cascade n est faible, tandis qu’ils ont des performances similaires lorsque n est élevé. Ensuite, nous considérons le problème de la détection de puissance des signaux inconnus aux n* canaux de Rayleigh. Dans ce travail, de nouvelles expressions approximatives sont dérivées de la probabilité de détection moyenne avec et sans diversité en réception MRC. En outre, la performance du système est analysée lorsque la détection de spectre coopérative (CSS) est considérée sous diverses contraintes de canaux (par exemple, les canaux de communication parfaits et imparfaits). Les résultats numériques ont montré que la fiabilité de détection diminue à mesure que l'ordre n augmente et s’améliore sensiblement lorsque CSS emploie le schéma MRC. Il est démontré que CSS avec le schéma MRC maintient la probabilité de fausse alarme minimale dans les canaux d’information imparfaite plutôt que d'augmenter le nombre d'utilisateurs en coopération. Enfin, nous présentons une nouvelle approche pour l'analyse des performances des systèmes IVC sur n*canaux de Rayleigh, en utilisant n_T antennes d'émission et n_R antennes de réception pour lutter contre l'effet d’évanouissement. Dans ce contexte, nous évaluons la performance des systèmes MIMO-V2V basés sur la sélection des antennes d'émission avec un ratio maximum de combinaison (TAS/MRC) et la sélection combinant (TAS/SC). Dans cette étude, nous dérivons des expressions analytiques plus précises pour la probabilité de défaillance, la probabilité d'erreur de symbole, et l’évanouissement sur n*canaux Rayleigh. Il est montré que les deux régimes ont le même ordre de diversité maximale équivalent à (d≈mn_T n_R /n) . En outre, TAS / MRC offre un gain de performance mieux que TAS/ SC lorsque le nombre d'antennes de réception est plus que celle des antennes d’émission, mais l’amélioration de la performance est limitée lorsque n augmente.----------Abstract The purpose of intervehicular communication (IVC) systems is to enhance driving safety, in which vehicles use sensors and wireless communication techniques to talk to each other without any roadside intervention. Using these systems, vehicle-to-vehicle (V2V) communications can be more effective in avoiding accidents and traffic congestion than if each vehicle works individually. A potential solution can be implemented in this research area using cooperative communications systems which, in principle, increase spectral and power efficiency, network coverage, and reduce the outage probability. Antenna diversity (i.e., multiple-input multiple output (MIMO) systems) can also be an alternative solution for IVC systems to enhance channel capacity and diversity (reliability) but in exchange of an increased complexity. However, applying such solutions is challenging since wireless communications among vehicles is subject to harsh fading channels called ‘n*Rayleigh fading channels’, which leads to performance degradation. Therefore, in this thesis we provide a comprehensive performance analysis of cooperative transmission and MIMO systems over n*Rayleigh fading channels that help researchers for the design and implementation of V2V communication systems with lower complexity. Specifically, we first investigate the performance of cooperative IVC systems with relay selection over n*Rayleigh fading channels, assuming that both the decode-and-forward and the amplify-and-forward relaying protocols are achieved by N relays to transfer the source message to the destination. System performance is analyzed in terms of outage probability, symbol error probability, and average channel capacity. The numerical results have shown that the best relay selection approach achieves the diversity order of (d≈mN/n) where m is a cascaded Rayleigh fading parameter. Second, we investigate the performance of multihop-IVC systems with regenerative and non-regenerative relays. In this study, we derive approximate closed-form expressions for the outage probability and amount of fading when the maximum ratio combining (MRC) diversity reception is employed. Further, we analyze the power allocation for the underlying scheme in order to minimize the overall outage probability. We show that the performance of regenerative systems is better than that of non-regenerative systems when the cascading order n is low and they have similar performance when n is high. Third, we consider the problem of energy detection of unknown signals over n*Rayleigh fading channels. In this work, novel approximate expressions are derived for the average probability of detection with and without MRC diversity reception. Moreover, the system performance is analyzed when cooperative spectrum sensing (CSS) is considered under various channel constraints (e.g, perfect and imperfect reporting channels). The numerical results show that the detection reliability decreases as the cascading order n increases and substantially improves when CSS employs MRC schemes. It is demonstrated that CSS with MRC scheme keeps the probability of false alarm minimal under imperfect reporting channels rather than increasing the number of cooperative users. Finally, we present a new approach for the performance analysis of IVC systems over n*Rayleigh fading channels, using n_T transmit and n_R receive antennas to combat fading influence. In this context, we evaluate the performance of MIMO-V2V systems based on the transmit antenna selection with maximum ratio combining (TAS/MRC) and selection combining (TAS/SC) schemes. In this study, we derive tight analytical expressions for the outage probability, the symbol error probability, and the amount of fading over n*Rayleigh fading channels. It is shown that both schemes have the same maximum diversity order equivalent to (d≈mn_T n_R /n). In addition, TAS/MRC offers a better performance gain than TAS/SC scheme when the number of receive antennas is more than that of transmit antennas, but the performance improvement is limited as n increases

Physical-Layer Security in Cognitive Radio Networks

The fifth-generation (5G) communications and beyond are expected to serve a huge number of devices and services. However, due to the fixed spectrum allocation policies, the need for cognitive radio networks (CRNs) has increased accordingly. CRNs have been proposed as a promising approach to address the problem of under-utilization and scarcity of the spectrum. In CRNs, secondary users (SUs) access the licensed spectrum of the primary users (PUs) using underlay, overlay, or interweave paradigms. SUs can access the spectrum band simultaneously with the PUs in underlay access mode provided that the SUs’ transmission power does not cause interference to the PUs’ communication. In this case, SUs should keep monitoring the interference level that the PU receiver can tolerate and adjust the transmission power accordingly. However, varying the transmission power may lead to some threats to the privacy of the information transfer of CRNs. Therefore, securing data transmission in an underlay CRN is a challenge that should be addressed. Physical-layer security (PLS) has recently emerged as a reliable method to protect the confidentiality of the SUs’ transmission against attacks, especially for the underlay model with no need for sharing security keys. Indeed, PLS has the advantage of safeguarding the data transmission without the necessity of adding enormous additional resources, specifically when there are massively connected devices. Apart from the energy consumed by the various functions carried out by SUs, enhancing security consumes additional energy. Therefore, energy harvesting (EH) is adopted in our work to achieve both; energy efficiency and spectral efficiency. EH is a significant breakthrough for green communication, allowing the network nodes to reap energy from multiple sources to lengthen battery life. The energy from various sources, such as solar, wind, vibration, and radio frequency (RF) signals, can be obtained through the process of EH. This accumulated energy can be stored to be used for various processes, such as improving the users’ privacy and prolonging the energy-constrained devices’ battery life. In this thesis, for the purpose of realistic modelling of signal transmission, we explicitly assume scenarios involving moving vehicles or nodes in networks that are densely surrounded by obstacles. Hence, we begin our investigations by studying the link performance under the impact of cascaded κ−μ fading channels. Moreover, using the approach of PLS, we address the privacy of several three-node wiretap system models, in which there are two legitimate devices communicating under the threat of eavesdroppers. We begin by a three-node wiretap system model operating over cascaded κ − μ fading channels and under worst-case assumptions. Moreover, assuming cascaded κ − μ distributions for all the links, we investigate the impact of these cascade levels, as well as the impact of multiple antennas employed at the eavesdropper on security. Additionally, the PLS is examined for two distinct eavesdropping scenarios: colluding and non-colluding eavesdroppers. Throughout the thesis, PLS is mainly evaluated through the secrecy outage probability (SOP), the probability of non-zero secrecy capacity (Pnzcr ), and the intercept probability (Pint). Considering an underlay CRN operating over cascaded Rayleigh fading channel, with the presence of an eavesdropper, we explore the PLS for SUs in the network. This study is then extended to investigate the PLS of SUs in an underlay single-input-multiple-output (SIMO) CRN over cascaded κ-μ general fading channels with the presence of a multi-antenna eavesdropper. The impact of the constraint over the transmission power of the SU transmitter due to the underlay access mode is investigated. In addition, the effects of multiple antennas and cascade levels over security are well-explored. In the second part of our thesis, we propose an underlay CRN, in which an SU transmitter communicates with an SU destination over cascaded κ-μ channels. The confidentiality of the shared information between SUs is threatened by an eavesdropper. Our major objective is to achieve a secured network, while at the same time improving the energy and spectrum efficiencies with practical modeling for signals’ propagation. Hence, we presume that the SU destination harvests energy from the SU transmitter. The harvested energy is used to produce jamming signals to be transmitted to mislead the eavesdropper. In this scenario, a comparison is made between an energy-harvesting eavesdropper and a non-energy harvesting one. Additionally, we present another scenario in which cooperative jamming is utilized as one of the means to boost security. In this system model, the users are assumed to communicate over cascaded Rayleigh channels. Moreover, two scenarios for the tapping capabilities of the eavesdroppers are presented; colluding and non-colluding eavesdroppers. This study is then extended for the case of non-colluding eavesdroppers, operating over cascaded κ-μ channels. Finally, we investigate the reliability of the SUs and PUs while accessing the licensed bands using the overlay mode, while enhancing the energy efficiency via EH techniques. Hence, we assume that multiple SUs are randomly distributed, in which one of the SUs is selected to harvest energy from the PUs’ messages. Then, utilizing the gathered energy, this SU combines its own messages with the amplified PUs messages and forwards them to the destinations. Furthermore, we develop two optimization problems with the potential of maximizing the secondary users’ rate and the sum rate of both networks

Mobile and Wireless Communications

Mobile and Wireless Communications have been one of the major revolutions of the late twentieth century. We are witnessing a very fast growth in these technologies where mobile and wireless communications have become so ubiquitous in our society and indispensable for our daily lives. The relentless demand for higher data rates with better quality of services to comply with state-of-the art applications has revolutionized the wireless communication field and led to the emergence of new technologies such as Bluetooth, WiFi, Wimax, Ultra wideband, OFDMA. Moreover, the market tendency confirms that this revolution is not ready to stop in the foreseen future. Mobile and wireless communications applications cover diverse areas including entertainment, industrialist, biomedical, medicine, safety and security, and others, which definitely are improving our daily life. Wireless communication network is a multidisciplinary field addressing different aspects raging from theoretical analysis, system architecture design, and hardware and software implementations. While different new applications are requiring higher data rates and better quality of service and prolonging the mobile battery life, new development and advanced research studies and systems and circuits designs are necessary to keep pace with the market requirements. This book covers the most advanced research and development topics in mobile and wireless communication networks. It is divided into two parts with a total of thirty-four stand-alone chapters covering various areas of wireless communications of special topics including: physical layer and network layer, access methods and scheduling, techniques and technologies, antenna and amplifier design, integrated circuit design, applications and systems. These chapters present advanced novel and cutting-edge results and development related to wireless communication offering the readers the opportunity to enrich their knowledge in specific topics as well as to explore the whole field of rapidly emerging mobile and wireless networks. We hope that this book will be useful for students, researchers and practitioners in their research studies

Radio Communications

In the last decades the restless evolution of information and communication technologies (ICT) brought to a deep transformation of our habits. The growth of the Internet and the advances in hardware and software implementations modified our way to communicate and to share information. In this book, an overview of the major issues faced today by researchers in the field of radio communications is given through 35 high quality chapters written by specialists working in universities and research centers all over the world. Various aspects will be deeply discussed: channel modeling, beamforming, multiple antennas, cooperative networks, opportunistic scheduling, advanced admission control, handover management, systems performance assessment, routing issues in mobility conditions, localization, web security. Advanced techniques for the radio resource management will be discussed both in single and multiple radio technologies; either in infrastructure, mesh or ad hoc networks

Advanced Trends in Wireless Communications

Physical limitations on wireless communication channels impose huge challenges to reliable communication. Bandwidth limitations, propagation loss, noise and interference make the wireless channel a narrow pipe that does not readily accommodate rapid flow of data. Thus, researches aim to design systems that are suitable to operate in such channels, in order to have high performance quality of service. Also, the mobility of the communication systems requires further investigations to reduce the complexity and the power consumption of the receiver. This book aims to provide highlights of the current research in the field of wireless communications. The subjects discussed are very valuable to communication researchers rather than researchers in the wireless related areas. The book chapters cover a wide range of wireless communication topics

Cooperative Radio Communications for Green Smart Environments

The demand for mobile connectivity is continuously increasing, and by 2020 Mobile and Wireless Communications will serve not only very dense populations of mobile phones and nomadic computers, but also the expected multiplicity of devices and sensors located in machines, vehicles, health systems and city infrastructures. Future Mobile Networks are then faced with many new scenarios and use cases, which will load the networks with different data traffic patterns, in new or shared spectrum bands, creating new specific requirements. This book addresses both the techniques to model, analyse and optimise the radio links and transmission systems in such scenarios, together with the most advanced radio access, resource management and mobile networking technologies. This text summarises the work performed by more than 500 researchers from more than 120 institutions in Europe, America and Asia, from both academia and industries, within the framework of the COST IC1004 Action on "Cooperative Radio Communications for Green and Smart Environments". The book will have appeal to graduates and researchers in the Radio Communications area, and also to engineers working in the Wireless industry. Topics discussed in this book include: • Radio waves propagation phenomena in diverse urban, indoor, vehicular and body environments• Measurements, characterization, and modelling of radio channels beyond 4G networks• Key issues in Vehicle (V2X) communication• Wireless Body Area Networks, including specific Radio Channel Models for WBANs• Energy efficiency and resource management enhancements in Radio Access Networks• Definitions and models for the virtualised and cloud RAN architectures• Advances on feasible indoor localization and tracking techniques• Recent findings and innovations in antenna systems for communications• Physical Layer Network Coding for next generation wireless systems• Methods and techniques for MIMO Over the Air (OTA) testin