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

Nonorthogonal Multiple Access for 5G and Beyond

This work was supported in part by the U.K. Engineering and Physical Sciences Research Council (EPSRC) under Grant EP/N029720/1 and Grant EP/N029720/2. The work of L. Hanzo was supported by the ERC Advanced Fellow Grant Beam-me-up

Cooperative Communications inWireless Local Area Networks: MAC Protocol Design and Multi-layer Solutions

This dissertation addresses cooperative communications and proposes multi-layer solu- tions for wireless local area networks, focusing on cooperative MAC design. The coop- erative MAC design starts from CSMA/CA based wireless networks. Three key issues of cooperation from the MAC layer are dealt with: i.e., when to cooperate (opportunistic cooperation), whom to cooperate with (relay selection), and how to protect cooperative transmissions (message procedure design). In addition, a cooperative MAC protocol that addresses these three issues is proposed. The relay selection scheme is further optimized in a clustered network to solve the problem of high collision probability in a dense network. The performance of the proposed schemes is evaluated in terms of through- put, packet delivery rate and energy efficiency. Furthermore, the proposed protocol is verified through formal model checking using SPIN. Moreover, a cooperative code allo- cation scheme is proposed targeting at a clustered network where multiple relay nodes can transmit simultaneously. The cooperative communication design is then extended to the routing layer through cross layer routing metrics. Another part of the work aims at enabling concurrent transmissions using cooperative carrier sensing to improve the per- formance in a WLAN network with multiple access points sharing the same channel

A Survey on Wireless Security: Technical Challenges, Recent Advances and Future Trends

This paper examines the security vulnerabilities and threats imposed by the inherent open nature of wireless communications and to devise efficient defense mechanisms for improving the wireless network security. We first summarize the security requirements of wireless networks, including their authenticity, confidentiality, integrity and availability issues. Next, a comprehensive overview of security attacks encountered in wireless networks is presented in view of the network protocol architecture, where the potential security threats are discussed at each protocol layer. We also provide a survey of the existing security protocols and algorithms that are adopted in the existing wireless network standards, such as the Bluetooth, Wi-Fi, WiMAX, and the long-term evolution (LTE) systems. Then, we discuss the state-of-the-art in physical-layer security, which is an emerging technique of securing the open communications environment against eavesdropping attacks at the physical layer. We also introduce the family of various jamming attacks and their counter-measures, including the constant jammer, intermittent jammer, reactive jammer, adaptive jammer and intelligent jammer. Additionally, we discuss the integration of physical-layer security into existing authentication and cryptography mechanisms for further securing wireless networks. Finally, some technical challenges which remain unresolved at the time of writing are summarized and the future trends in wireless security are discussed.Comment: 36 pages. Accepted to Appear in Proceedings of the IEEE, 201

4G Technology Features and Evolution towards IMT-Advanced

Kiinteiden- ja mobiilipalveluiden kysyntä kasvaa nopeasti ympäri maailmaa. Älykkäiden päätelaitteiden, kuten iPhone:n ja Nokia N900:n markkinoilletulo yhdistettynä näiden korkeaan markkinapenetraatioon ja korkealuokkaiseen käyttäjäkokemukseen lisäävät entisestään palveluiden kysyntää ja luovat tarpeen jatkuvalle innovoinnille langattomien teknologioiden alalla tavoitteena lisäkapasiteetin ja paremman palvelunlaadun tarjoaminen. Termi 4G (4th Generation) viittaa tuleviin neljännen sukupolven mobiileihin langattomiin palveluihin, jotka International Telecommunications Union:in Radiocommunication Sector (ITU-R) on määritellyt ja nimennyt International Mobile Telecommunications-Advanced (IMT-Advanced). Nämä ovat järjestelmiä, jotka pitävät sisällään IMT:n ne uudet ominaisuudet, jotka ylittävät IMT-2000:n vaatimukset. Long Term Evolution-Advanced (LTE-Advanced) ja IEEE 802.16m ovat IMT-A sertifiointiin lähetetyt kaksi pääasiallista kandidaattiteknologiaa. Tässä diplomityössä esitellään kolmannen sukupolven järjestelmien kehityspolku LTE:hen ja IEEE 802.16e-2005 asti. Lisäksi työssä esitetään LTE-Advanced:n ja IEEE 802.16m:n uudet vaatimukset ja ominaisuudet sekä vertaillaan näiden lähestymistapoja IMT-A vaatimusten täyttämiseksi. Lopuksi työssä luodaan katsaus LTE ja IEEE 802.16e-2005 (markkinointinimeltään Mobile WiMAX) -järjestelmien markkinatilanteeseen.The demand for affordable bandwidth in fixed and mobile services is growing rapidly around the world. The emergence of smart devices like the iPhone and Nokia N900, coupled with their high market penetration and superior user experience is behind this increased demand, inevitably driving the need for continued innovations in the wireless data technologies industry to provide more capacity and higher quality of service. The term "4G" meaning the 4th Generation of wireless technology describes mobile wireless services which have been defined by the ITU's Radiocommunication Sector (ITU-R) and titled International Mobile Telecommunications-Advanced (IMT-Advanced). These are mobile systems that include the new capabilities of IMT that go beyond those of IMT-2000. Long Term Evolution-Advanced (LTE-Advanced) and IEEE 802.16m are the two main candidate technologies submitted for IMT-Advanced certification. This thesis reviews the technology roadmap up to and including current 3G systems LTE from the 3rd Generation Partnership Project (3GPP) and IEEE 802.16e-2005 from the Institute of Electrical and Electronics Engineers (IEEE). Furthermore, new requirements and features for LTE-Advanced and IEEE 802.16m as well as a comparative approach towards IMT-Advanced certification are presented. Finally, the thesis concludes with a discussion on the market status and deployment strategies of LTE and IEEE 802.16e-2005, or Mobile WiMAX as it is being marketed

Hardware Impairments Aware Transceiver Design for Bidirectional Full-Duplex MIMO OFDM Systems

In this paper we address the linear precoding and decoding design problem for a bidirectional orthogonal frequencydivision multiplexing (OFDM) communication system, between two multiple-input multiple-output (MIMO) full-duplex (FD) nodes. The effects of hardware distortion as well as the channel state information error are taken into account. In the first step, we transform the available time-domain characterization of the hardware distortions for FD MIMO transceivers to the frequency domain, via a linear Fourier transformation. As a result, the explicit impact of hardware inaccuracies on the residual selfinterference (RSI) and inter-carrier leakage (ICL) is formulated in relation to the intended transmit/received signals. Afterwards, linear precoding and decoding designs are proposed to enhance the system performance following the minimum-mean-squarederror (MMSE) and sum rate maximization strategies, assuming the availability of perfect or erroneous CSI. The proposed designs are based on the application of alternating optimization over the system parameters, leading to a necessary convergence. Numerical results indicate that the application of a distortionaware design is essential for a system with a high hardware distortion, or for a system with a low thermal noise variance.Comment: Submitted to IEEE for publicatio