Communications In Interference Limited Networks

This book offers means to handle interference as a central problem of operating wireless networks. It investigates centralized and decentralized methods to avoid and handle interference as well as approaches that resolve interference constructively. The latter type of approach tries to solve the joint detection and estimation problem of several data streams that share a common medium. In fact, an exciting insight into the operation of networks is that it may be beneficial, in terms of an overall throughput, to actively create and manage interference. Thus, when handled properly, "mixing" of data in networks becomes a useful tool of operation rather than the nuisance as which it has been treated traditionally. With the development of mobile, robust, ubiquitous, reliable and instantaneous communication being a driving and enabling factor of an information centric economy, the understanding, mitigation and exploitation of interference in networks must be seen as a centrally important task.

Since interference is the main performance-limiting factor in most wireless networks, it is crucial to characterize the interference statistics. The main two determinants of the interference are the network geometry (spatial distribution of concurrently transmitting nodes) and the path loss law (signal attenuation with distance). For certain classes of node distributions, most notably Poisson point processes, and attenuation laws, closed-form results are available, for both the interference itself as well as the signal-to-interference ratios, which determine the network performance. This monograph presents an overview of these results and gives an introduction to the analytical techniques used in their derivation. The node distribution models range from lattices to homogeneous and clustered Poisson models to general motion-invariant ones. The analysis of the more general models requires the use of Palm theory, in particular conditional probability generating functionals, which are briefly introduced in the appendix.

Dans cette thèse, nous menons une étude dans le cadre de la théorie de l'information sur deux questions importantes de la communication sans fil : l'amélioration du débit de données dans les réseaux avec interférence grâce à la coopération entre utilisateurs et le renforcement de la sécurité des transmissions à l'aide d'un signal de rétroaction.Dans la première partie de la thèse, nous nous concentrons sur le modèle le plus simple qui intègre à la fois l'interférence et la coopération, le canal à relais et interférence ou IRC (Interference Relay Channel). Notre objectif est de caractériser dans un nombre fixe de bits la région de capacité du IRC gaussien. À cette fin, nous dérivons une nouvelle limite supérieure de la capacité et deux stratégies de transmission. La limite supérieure est notamment obtenue grâce à une extension non triviale que nous proposons, de la classe de canaux semi-déterministe et injective à l'origine dérivée par Telatar et Tse pour le canal à interférence.Dans la seconde partie, nous étudions le canal avec espion et rétroaction généralisée ou WCGF (Wiretap Channel with Generalized Feedback). Notre objectif est de développer une stratégie de transmission générale qui englobe les résultats existants pour les différents modèles de rétroaction trouvés dans la littérature. À cette fin, nous proposons deux stratégies de transmission différentes sur la capacité du WCGF sans mémoire. Nous dérivons d'abord une stratégie qui est basée sur le codage source-canal conjoint. Nous introduisons ensuite une seconde stratégie où le signal de rétroaction est utilisé pour générer une clé secrète qui permet de chiffrer le message partiellement ou totalement.

In wireless vehicular communication networks the periodic transmission of status updates by all vehicles represents a basic service primitive, in particular for safety related applications. Due to the limited communication resources the question raises how much data each node may provide such that the quality of service required by applications can still be guaranteed under realistic interference conditions. Local broadcasts capacity is introduced and analyzed to tackle this open question.

Learn about a new, information-theoretic approach to minimizing interference in 5G wireless networks.

This book targets major issues in terrestrial-satellite communication networks and presents the solutions. While the terrestrial networks can achieve high-speed data service at low cost, satellite based access is one way to complement terrestrial based networks to ensure ubiquitous, 100% geographic coverage. The coexistence and cooperation between terrestrial and satellite networks are of great potential in future communication networks, and satellite radio access networks has already been considered in the fifth-generation (5G) networks to be supported for phase 2. Therefore, it is important to study the architectures of terrestrial-satellite networks, as well as the possible techniques and challenges. The authors introduce the technique of beamforming in satellite communication systems, which is an efficient transmitting method for multiple access, and they discuss the main challenges as well as prospective applications. The authors introduce possible methods for interference cancelation reception in terrestrial-satellite communication networks when reusing the frequency band between the two networks. Due to the limitation of spectrum resources, spectrum sharing will become one of the important issues in terrestrial-satellite communication networks. The problems of spectrum coexistence between GEO and Terrestrial Systems and between GEO and NEGO systems are also discussed. Finally, taking both the two system into consideration, the resource allocation problem will be more complex due to the coupling between resources and the interference. Based on this, the authors propose several resource allocation schemes in different scenarios of terrestrial-satellite communication networks, which can optimize the capacity performance of the system. The expected audience for this book includes (but not limited to) graduate students, professors, researchers, scientists, practitioners, engineers, industry managers, and government researchers working in the field of satellite communications and networks. The expected audience for this book includes (but not limited to) graduate students, professors, researchers, scientists, practitioners, engineers, industry managers, and government researchers working in the field of satellite communications and networks.

In this dissertation, we address two issues related to communication in interference-limited wireless networks. In the first part of the thesis, we study benefits of deploying inexpensive half-duplex relays in interference-limited cellular system. We study two relaying schemes in a downlink system, users sharing the same frequency band. In the first collaborative relaying scheme, relays help users after they decode the message intended for the user by a collaborative power addition scheme. We evaluate power savings and rate improvement for delivering a common rate for 90% of users in the system. We then consider power control at the base stations and relays in order to manage the interference. In both cases, the ability of relays to reduce the peak base station transmit power while delivering the baseline rate or alternately to increase the user rate is computed. When power control is employed, the peak power saving is 2.6 dB and the average total power in the system can be reduced by 3 dB. We also observe a 34% improvement over the baseline in the users' common rate. In the second orthogonal relaying scheme, we study a simple scheme where the base station and relays transmit in orthogonal time slots. We find that the performance of the simple orthogonal relaying scheme comes very close to that of the collaborative power addition scheme. In the second part of the thesis, we consider a centralized spectrum server that coordinates the transmissions of a group of links sharing a common spectrum. Links employ on-off modulation with fixed transmit power when active. The rate obtained by an active link depends on the activity of all other links. With knowledge of the link gains in the network, the spectrum server schedules the on/off periods of the links so as to satisfy constraints on link fairness and efficiency. We then extend the centralized scheduling framework to multi-hop wireless networks with interfering links. A framework for cross-layer scheduling of end-to-end flows in a multi-hop wireless network with links sharing a common spectrum is presented. Given a set of known routes, the optimization framework can be used to find the flow on each route in order to maximize an objective function. The framework encompasses a variety of physical layer transmission schemes. The rates in the individual links are determined based on the transmission strategy employed. With the knowledge of the link rates in the network, the spectrum server schedules the rates on the links and flows on the sessions to maximize a utility function of the source rates. The schedules are a collection of time shared transmission modes (sets of active links).

In an interference network, multiple transmitters communicate with multiple receivers using the same communication channel. The capacity region of an interference network is defined as the set of data rates that can be simultaneously achieved by the users of the network. One of the most important example of an interference network is the wireless network, where the communication channel is the wireless channel. Wireless interference networks are known to be interference limited rather than noise limited since the interference power level at the receivers (caused by other user's transmissions) is much higher than the noise power level. Most wireless communication systems deployed today employ transmission strategies where the interfering signals are treated in the same manner as thermal noise. Such strategies are known to be suboptimal (in terms of achieving higher data rates), because the interfering signals generated by other transmitters have a structure to them that is very different from that of random thermal noise. Hence, there is a need to design transmission strategies that exploit this structure of the interfering signals to achieve higher data rates. However, determining optimal strategies for mitigating interference has been a long standing open problem. In fact, even for the simplest interference network with just two users, the capacity region is unknown. In this dissertation, we will investigate the capacity region of several models of interference channels. We will derive limits on achievable data rates and design effective transmission strategies that come close to achieving the limits. We will investigate two kinds of networks - "small" (usually characterized by two transmitters and two receivers) and "large" where the number of users is large.

Indoor Wireless Communications: From Theory to Implementation provides an in-depth reference for design engineers, system planners and post graduate students interested in the vastly popular field of indoor wireless communications. It contains wireless applications and services for in-building scenarios and knowledge of key elements in the design and implementation of these systems. Technologies such as Wireless Local Area Networks, Bluetooth, ZigBee, Indoor Optical Communications, WiMAX, UMTS and GSM for indoor environments are fully explained and illustrated with examples. Antennas and propagation issues for in-building scenarios are also discussed, emphasizing models and antenna types specifically developed for indoor communications. An exhaustive survey on indoor wireless communication equipment is also presented, covering all available technologies including antennas, distribution systems, transceivers and base stations.