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

5G Cellular: Key Enabling Technologies and Research Challenges

The evolving fifth generation (5G) cellular wireless networks are envisioned to provide higher data rates, enhanced end-user quality-of-experience (QoE), reduced end-to-end latency, and lower energy consumption. This article presents several emerging technologies, which will enable and define the 5G mobile communications standards. The major research problems, which these new technologies breed, as well as the measurement and test challenges for 5G systems are also highlighted.Comment: IEEE Instrumentation and Measurement Magazine, to appear in the June 2015 issue. arXiv admin note: text overlap with arXiv:1406.6470 by other author

Esquemas de cooperação entre estações base para o LTE no sentido descendente

The explosive growth in wireless traffic and in the number of connected devices as smart phones or computers, are causing a dramatic increase in the levels of interference, which significantly degrades the capacity gains promised by the point-to-point multi input, multi output (MIMO) based techniques. Therefore, it is becoming increasingly clear that major new improvements in spectral efficiency of wireless networks will have to entail addressing intercell interference. So, there is a need for a new cellular architecture that can take these factors under consideration. It is in this context that LTE-Advanced arises. One of the most promising LTE-Advanced technology is Coordinated Multipoint (CoMP), which allows base stations to cooperate among them, in order to mitigate or eliminate the intercell interference and, by doing so, increase the system’s capacity. This thesis intends to study this concept, implementing some schemes that fall under the CoMP concept. In this thesis we consider a distributed precoded multicell approach, where the precoders are computed locally at each BS to mitigate the intercell interference. Two precoder are considered: distributed zero forcing (DZF) and distributed virtual signal-to-interference noise ratio (DVSINR) recently proposed. Then the system is further optimized by computing a power allocation algorithm over the subcarriers that minimizes the average bit error rate (BER). The considered algorithms are also evaluated under imperfect channel state information. A quantized version of the CSI associated to the different links between the BS and the UT is feedback from the UT to the BS. This information is then employed by the different BSs to perform the precoding design. A new DVSINR precoder explicitly designed under imperfect CSI is proposed. The proposed schemes were implemented considering the LTE specifications, and the results show that the considered precoders are efficiently to remove the interference even under imperfect CSI.O crescimento exponencial no tráfego de comunicações sem-fios e no número de dispositivos utilizados (smart phones, computadores portáteis, etc.) está a causar um aumento significativo nos níveis de interferência, que prejudicam significativamente os ganhos de capacidade assegurados pelas tecnologias baseadas em ligações ponto-a-ponto MIMO. Deste modo, torna-se cada vez mais necessário que os grandes aperfeiçoamentos na eficiência espectral de sistemas de comunicações sem-fios tenham em consideração a interferência entre células. De forma a tomar em consideração estes aspectos, uma nova arquitectura celular terá de ser desenvolvida. É assim, neste contexto, que surge o LTE-Advanced. Uma das tecnologias mais promissoras do LTE-Advanced é a Coordenação Multi-Ponto (CoMP), que permite que as estações base cooperem de modo a mitigar a interferência entre células e, deste modo, aumentar a capacidade do sistema. Esta dissertação pretende estudar este conceito, implementando para isso algumas técnicas que se enquadram no conceito do CoMP. Nesta dissertação iremos considerar a implementação de um sistema de pré-codificação em múltiplas células, em que os pré-codificadores são calculados em cada BS, de modo a mitigar a interferência entre células. São considerados dois pré-codificadores: Distributed Zero Forcing (DZF) e Distributed Virtual Signal-to-Interferance Noise Ratio (DVSINR), recentemente proposto. De seguida o sistema é optimizado com a introdução de algoritmos de alocação de potência entre as sub-portadoras com o objectivo de minimizar a taxa média de erros (BER). Os algoritmos considerados são também avaliados em situações em que a informação do estado do canal é imperfeita. Uma versão quantizada da CSI associada a cada uma das diferentes ligações entre as BS e os UT é assim enviada do UT para a BS. Esta informação é então utilizada para calcular os diferentes pré-codificadores em cada BS. Uma nova versão do pré-codificador DVSINR é proposta de modo a lidar com CSI imperfeito. Os esquemas propostos foram implementados considerandos especificações do LTE, e os resultados obtidos demonstram que os pré-codificadores removem de uma forma eficiente a interferência, mesmo em situações em que a CSI é imperfeita

Relay Technology in Cellular Networks

Relay technology has been explored and studied for decades, ranging from generic multi-hop mobile ad hoc networks to most recent collaborative multiple-input multiple-output (MIMO) cellular networks. Deploying low cost relays reduces the infrastructure cost of establishing new base stations in order to improve the cell coverage and system capacity of next generation cellular networks. For efficient heterogeneous network planning, fixed relays are considered as one of the main enhancing technologies in 3rd Generation Partnership Project (3GPP) Long Term Evolution Advanced (LTE-A). The function of the relay station can be described simply as a device which assists in transmissions between the local base station and the mobile station. Since the performance of relay transmissions is strongly affected by the collaborative strategy in dense wireless networks, the relay selection always attracts research attentions. In this thesis, the symbol error probability of the selective decode-and-forward (DF) relaying strategy is derived to explore the selection diversity. Furthermore, an effective joint beamforming vector design and relay selection scheme for a MIMO relay system are proposed. In addition, two main relay deployment scenarios are addressed in this thesis: the fixed relay and the mobile relay. The LTE relay is a fixed relay which is located near the cell edge. A dynamic system level simulator is developed to evaluate the downlink transmission performance of fixed relay-enhanced LTE-A systems. With deployment of a high number of relay nodes inter-cell interference and resource management problems increase. An adaptive beamforming strategy with limited feedback is proposed to reduce inter-cell interference. The proposed algorithm has been applied in relay-enhanced LTE-A cellular networks to show its advantage. Furthermore, we study the concept of shared relays, in which a relay station is deployed at the intersection of neighboring macro cells. An efficient resource allocation and scheduling scheme based on the sub-frame structure of LTE-A is proposed to maximize the benefit of shared relays. As the penetration rate of mobile phones, especially smart phones keeps increasing, users in public transportation expect high speed wireless services. Recently, the mobile relay for high speed railways has gained significant interest. A system level simulator is developed to investigate the capacity and handover performance of the mobile relay in a high speed railway scenario. Furthermore, a coordinated mobile relay node (MRN) strategy is proposed to combat co-channel interference and handover delay problems in a conventional mobile relay system.Die Relaistechnik für Funksysteme wurde seit Jahrzehnten erforscht und untersucht, angefangen von generischen mobilen Multi-Hop Ad-hoc-Netzwerken bis hin zu kollaborativen multiple-input multiple-output (MIMO) Mobilfunknetzen. Das Aufstellen kostengünstiger Relais reduziert die Infrastrukturkosten für den Aufbau neuer Basisstationen, um die Zellabdeckung und die Systemkapazität von Mobilfunknetzen der nächsten Generation zu verbessern. Für eine effiziente heterogene Netzwerkplanung werden ''fixed relays'' (Festrelais) als eine der Technologien in 3GPP LTE-Advanced betrachtet, welche die größten Verbesserungen aufweisen. Die Funktion der Relaisstation kann beschrieben werden als eine Vorrichtung, welche bei der Übertragung zwischen der lokalen Basisstation und der Mobilstation unterstützend wirkt. Da die Leistung von Relaisübertragungen stark von der Kooperationsstragie in dichten Funknetzwerken abhängt, erregt die Relaisauswahl stets die Aufmerksamkeit der Forschung. In dieser Arbeit wird die Symbolfehlerwahrscheinlichkeit der selektiven decode-and-forward (DF) Relais-Strategie abgeleitet, um den Diversitätsgewinn Auswahldiversität zu untersuchen. Weiterhin wurde ein gemeinsames Strahlformungsvektor-Design und Relais-auswahlschema für ein MIMO-Relais-System vorgestellt. Des Weiteren werden in dieser Arbeit zwei wesentliche Relais-Verteilungsszenarien untersucht: das Festrelais-Szenario und das Mobilrelais-Szenario. Das LTE Relais ist ein Festrelais, welches nah an dem Zellenrand liegt. Ein dynamischer System-Level-Simulator wurde entwickelt, um die Downlink-Übertragungsleistung von mit Festrelais erweiterten LTE-A-Systemen zu evaluieren. Bei der Verwendung einer hohen Anzahl von Relaisknoten steigt zum einem die Interzellinterferenz und zum anderen die Problematik des Ressourcenmanagements. Es wird eine adaptive Strahlformungsstrategie mit wenig zurückgekoppelte Information vorgestellt, um Zellinterferenzprobleme zu reduzieren. Der vorgestellte Algorithmus wird auf ein mit Relaisstationen erweitertes LTE-A-Mobilfunknetz angewendet, um seine Vorteile aufzuzeigen. Weiterhin wird das Konzept eines gemeinsam genutzten Relais untersucht, in welchem eine Relaisstation an der Grenze von benachbarten Makrozellen aufgestellt wird. Es wird ein effizientes Ressourcenzuweisungs- und Zeitplanungsschema, basierend auf der Sub-Rahmenstruktur, vorgestellt, um den Vorteil von gemeinsam genutzten Relais zu maximieren. Da die Verbreitungsrate von Mobiltelefonen, besonders von Smartphones, weiter ansteigt, werden Benutzer auch in öffentlichen Verkehrsmitteln drahtlose Hochgeschwindigkeitsdienste erwarten. In letzter Zeit hat das Mobilrelais für Hochgeschwindigkeitszüge große Bedeutung gewonnen. Es wurde daher ein System-Level-Simulator entwickelt, um die Kapazität und Übergabgeleistungsfähigkeit von Mobilrelais in Hochgeschwindigkeitszug-Szenarios zu untersuchen. Zusätzlich wird eine koordinierte Mobilrelais-Strategie zur Bekämpfung von Gleichkanalinterferenz und Übergabeverzögerungsproblemen in herkömmlichen Mobilrelaissystemen vorgestellt

End-to-End Simulation of 5G mmWave Networks

Due to its potential for multi-gigabit and low latency wireless links, millimeter wave (mmWave) technology is expected to play a central role in 5th generation cellular systems. While there has been considerable progress in understanding the mmWave physical layer, innovations will be required at all layers of the protocol stack, in both the access and the core network. Discrete-event network simulation is essential for end-to-end, cross-layer research and development. This paper provides a tutorial on a recently developed full-stack mmWave module integrated into the widely used open-source ns--3 simulator. The module includes a number of detailed statistical channel models as well as the ability to incorporate real measurements or ray-tracing data. The Physical (PHY) and Medium Access Control (MAC) layers are modular and highly customizable, making it easy to integrate algorithms or compare Orthogonal Frequency Division Multiplexing (OFDM) numerologies, for example. The module is interfaced with the core network of the ns--3 Long Term Evolution (LTE) module for full-stack simulations of end-to-end connectivity, and advanced architectural features, such as dual-connectivity, are also available. To facilitate the understanding of the module, and verify its correct functioning, we provide several examples that show the performance of the custom mmWave stack as well as custom congestion control algorithms designed specifically for efficient utilization of the mmWave channel.Comment: 25 pages, 16 figures, submitted to IEEE Communications Surveys and Tutorials (revised Jan. 2018

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

Cooperative diversity schemes for wireless communication systems

Mestrado em Engenharia Electrónica e TelecomunicaçõesA presente dissertação insere-se na área das comunicações sem fios, ou mais especificamente na temática da diversidade cooperativa. Neste trabalho é feito o estudo, implementação e avaliação do desempenho de esquemas de diversidade cooperativa de baixa complexidade para sistemas de comunicação móvel. Estes esquemas são mapeados em modelos de simulação baseados em OFDMA e são completamente simulados em CoCentric System Studio. Os resultados obtidos com os modelos desenvolvidos mostram que os esquemas de diversidade cooperativa atenuam os efeitos do desvanecimento induzido pela propagação multipercurso, aumentando desta forma a capacidade e cobertura dos sistemas wireless. Os ganhos são particularmente altos quando as perdas de percurso são consideráveis, como é o caso das zonas urbanas densas. ABSTRACT: This dissertation is inserted into the wireless communication, or more specifically, into the cooperative diversity field. within this thesis, the performance of low-complexity cooperative diversity schemes projected for mobile communication systems are studied, implemented and evaluated. These schemes are mapped into simulation models based on OFDMA and are fully simulated in the CoCentric System Studio environment. The obtained results show that the proposed cooperative schemes for the uplink communication mitigate fading induced by multipath propagation, thereby increasing the capacity and coverage of wireless systems. Cooperation gains are particularly high when multipath losses are considerable, as is the case for dense urban regions