Algoritmo de Asignación de Canales para Redes de Comunicación Inalámbricas con Acceso Oportunista basado en Algoritmos Genéticos

La creciente demanda de conectividad inalámbrica (e.g. estándar IEEE802.11) en zonas densamente pobladas, conlleva a una gran cantidad de dispositivos de acceso inalámbrico operando sin coordinación sobre un mismo espacio geográfico, lo que podría llevar a altos niveles de interferencia entre los dispositivos, ya que operan en bandas de uso compartido (e.g.ISM). Fruto de esto se podrían generar problemas de funcionamiento tales como la atenuación del nivel de señal de transmisión y consecuentemente un bajo rendimiento de la red. Una posible solución a estos problemas podría ser el uso oportunista de canales de bandas licenciadas que tienen algún tipo de disponibilidad temporal o espacial. En este contexto se propone un sistema que disminuya la congestión del espectro en la banda ISM, mediante el desarrollo de un mecanismo de asignación de canales con acceso oportunista al espectro subutilizado, empleando conocidas técnicas heurísticas para la asignación de recursos como son los algoritmos genéticos, comúnmente utilizados en problemas de optimización complejos. Para esto será considerada la heterogeneidad del espectro y la priorización del uso de la banda ISM, con la finalidad de disminuir interferencias entre WLANs en un escenario urbano con diferentes densidades de dispositivos.The growing demand for wireless connectivity (e.g.IEEE802.11 standard) in densely populated, leading to have a large number of wireless devices operating without coordination on the same geographic space, which could lead to high levels of interference between devices, already operating in bands shared (e.g.ISM). The result of this operation could lead to problems such as attenuation of the transmitted signal level and consequently low network performance. One possible solution to these problems could be the opportunistic use of channels licensed bands that have some sort of temporal or spatial availability. In this context, a system to decrease congestion spectrum in the ISM band, by developing a mechanism for allocating channels with opportunistic access to underutilized spectrum, using techniques known heuristics for the allocation of resources such as genetic algorithms is proposed, commonly used in complex optimization problems. To this will be considered the heterogeneity of the spectrum and prioritizing the use of ISM band, in order to reduce interference between WLANs in an urban setting with different densities of devices

Asignación Distribuida Coordinada de Canales para WLANs con Acceso Oportunista

Las WLANs cuentan con una cantidad limitada de canales de frecuencia (espectro radio eléctrico), donde la saturación de estos canales en áreas densamente pobladas se torna un problema inevitable, y es imperativo encontrar nuevos procesos que permitan una eficiente administración de este recurso para mantener una buena calidad de funcionamiento (operación). En este artículo se presenta un algoritmo, basado en la técnica probabilística “Simulated Annealing”, para la asignación de canales de manera distribuida coordinada para redes WLAN, mediante la construcción de árboles de expansión mínima. Se realiza un proceso de asignación de costos y un análisis de niveles de interferencia, el mismo que se ejecuta para cada punto de acceso (AP) del escenario. El objetivo de este trabajo es conseguir una asignación eficiente de canales para cada AP, sea en la banda ISM, o de manera oportunista en una banda licenciada, que permita minimizar los niveles de interferencia de cada AP.WLANs have a limited number of frequency channels (radio spectrum), where the saturation of these channels in densely populated areas becomes an inevitable problem, and it is imperative to find new processes that enable efficient management of this resource to maintain good performance (operation). In this article is presented an algorithm, based on probabilistic technique 'Simulated Annealing', for channel assignment in a distributed coordinated manner for WLAN networks, by building Minimum Spanning Trees. A process of cost allocation and an analysis of interference levels is performed, the same as it is executed for each access point (AP) of the stage. The objective of this work is to achieve efficient allocation of channels for each AP, either in the ISM band, or opportunistically in a licensed band, which minimizes interference levels for each AP

Flexible cross layer optimization for fixed and mobile broadband telecommunication networks and beyond

In der heutigen Zeit, in der das Internet im Allgemeinen und Telekommunikationsnetze im Speziellen kritische Infrastrukturen erreicht haben, entstehen hohe Anforderungen und neue Herausforderungen an den Datentransport in Hinsicht auf Effizienz und Flexibilität. Heutige Telekommunikationsnetze sind jedoch rigide und statisch konzipiert, was nur ein geringes Maß an Flexibilität und Anpassungsfähigkeit der Netze ermöglicht und darüber hinaus nur im begrenzten Maße die Wichtigkeit von Datenflüssen im wiederspiegelt. Diverse Lösungsansätze zum kompletten Neuentwurf als auch zum evolutionären Konzept des Internet wurden ausgearbeitet und spezifiziert, um diese neuartigen Anforderungen und Herausforderungen adäquat zu adressieren. Einer dieser Ansätze ist das Cross Layer Optimierungs-Paradigma, welches eine bisher nicht mögliche direkte Kommunikation zwischen verteilten Funktionalitäten unterschiedlichen Typs ermöglicht, um ein höheres Maß an Dienstgüte zu erlangen. Ein wesentlicher Indikator, welcher die Relevanz dieses Ansatzes unterstreicht, zeichnet sich durch die Programmierbarkeit von Netzwerkfunktionalitäten aus, welche sich aus der Evolution von heutigen hin zu zukünftigen Netzen erkennen lässt. Dieses Konzept wird als ein vielversprechender Lösungsansatz für Kontrollmechanismen von Diensten in zukünftigen Kernnetzwerken erachtet. Dennoch existiert zur Zeit der Entstehung dieser Doktorarbeit kein Ansatz zur Cross Layer Optimierung in Festnetz-und Mobilfunknetze, welcher der geforderten Effizienz und Flexibilität gerecht wird. Die übergeordnete Zielsetzung dieser Arbeit adressiert die Konzeptionierung, Entwicklung und Evaluierung eines Cross Layer Optimierungsansatzes für Telekommunikationsnetze. Einen wesentlichen Schwerpunkt dieser Arbeit stellt die Definition einer theoretischen Konzeptionierung und deren praktischer Realisierung eines Systems zur Cross Layer Optimierung für Telekommunikationsnetze dar. Die durch diese Doktorarbeit analysierten wissenschaftlichen Fragestellungen betreffen u.a. die Anwendbarkeit von Cross Layer Optimierungsansätzen auf Telekommunikationsnetzwerke; die Betrachtung neuartiger Anforderungen; existierende Konzepte, Ansätze und Lösungen; die Abdeckung neuer Funktionalitäten durch bereits existierende Lösungen; und letztendlich den erkennbaren Mehrwert des neu vorgeschlagenen Konzepts gegenüber den bestehenden Lösungen. Die wissenschaftlichen Beiträge dieser Doktorarbeit lassen sich grob durch vier Säulen skizzieren: Erstens werden der Stand der Wissenschaft und Technik analysiert und bewertet, Anforderungen erhoben und eine Lückenanalyse vorgenommen. Zweitens werden Herausforderungen, Möglichkeiten, Limitierungen und Konzeptionierungsaspekte eines Modells zur Cross Layer Optimierung analysiert und evaluiert. Drittens wird ein konzeptionelles Modell - Generic Adaptive Resource Control (GARC) - spezifiziert, als Prototyp realisiert und ausgiebig validiert. Viertens werden theoretische und praktische Beiträge dieser Doktorarbeit vertiefend analysiert und bewertet.As the telecommunication world moves towards a data-only network environment, signaling, voice and other data are similarly transported as Internet Protocol packets. New requirements, challenges and opportunities are bound to this transition and influence telecommunication architectures accordingly. In this time in which the Internet in general, and telecommunication networks in particular, have entered critical infrastructures and systems, it is of high importance to guarantee efficient and flexible data transport. A certain level of Quality-of-Service (QoS) for critical services is crucial even during overload situations in the access and core network, as these two are the bottlenecks in the network. However, the current telecommunication architecture is rigid and static, which offers very limited flexibility and adaptability. Several concepts on clean slate as well as evolutionary approaches have been proposed and defined in order to cope with these new challenges and requirements. One of these approaches is the Cross Layer Optimization paradigm. This concept omits the strict separation and isolation of the Application-, Control- and Network-Layers as it enables interaction and fosters Cross Layer Optimization among them. One indicator underlying this trend is the programmability of network functions, which emerges clearly during the telecommunication network evolution towards the Future Internet. The concept is regarded as one solution for service control in future mobile core networks. However, no standardized approach for Cross Layer signaling nor optimizations in between the individual layers have been standardized at the time this thesis was written. The main objective of this thesis is the design, implementation and evaluation of a Cross Layer Optimization concept on telecommunication networks. A major emphasis is given to the definition of a theoretical model and its practical realization through the implementation of a Cross Layer network resource optimization system for telecommunication systems. The key questions answered through this thesis are: in which way can the Cross Layer Optimization paradigm be applied on telecommunication networks; which new requirements arise; which of the required functionalities cannot be covered through existing solutions, what other conceptual approaches already exist and finally whether such a new concept is viable. The work presented in this thesis and its contributions can be summarized in four parts: First, a review of related work, a requirement analysis and a gap analysis were performed. Second, challenges, limitations, opportunities and design aspects for specifying an optimization model between application and network layer were formulated. Third, a conceptual model - Generic Adaptive Resource Control (GARC) - was specified and its prototypical implementation was realized. Fourth, the theoretical and practical thesis contributions was validated and evaluated

Channel assignment algorithms for OSA-Enabled WLANs exploiting prioritization and spectrum heterogeneity

Allowing WLANs to exploit opportunistic spectrum access (OSA) is a promising approach to alleviate spectrum congestion problems in overcrowded unlicensed ISM bands, especially in highly dense WLAN deployments. In this context, novel channel assignment mechanisms jointly considering available channels in both unlicensed ISM and OSA-enabled licensed bands are needed. Unlike classical schemes proposed for legacy WLANs, channel assignment mechanisms for OSA-enabled WLAN should face two distinguishing issues: channel prioritization and spectrum heterogeneity. The first refers to the fact that additional prioritization criteria other than interference conditions should be considered when choosing between ISM or licensed band channels. The second refers to the fact that channel availability might not be the same for all WLAN Access Points because of primary users' activity in the OSA-enabled bands. This paper firstly formulates the channel assignment problem for OSA-enabled WLANs as a Binary Linear Programming (BLP) problem. The resulting BLP problem is optimally solved by means of branch and bound algorithms and used as a benchmark to develop more computationally efficient heuristics. Upon such a basis, a novel channel assignment algorithm based on weighted graph coloring heuristics and able to exploit both channel prioritization and spectrum heterogeneity is proposed. The algorithm is evaluated under different conditions of AP density and primary band availability.Peer Reviewe

Telecommunications Networks

This book guides readers through the basics of rapidly emerging networks to more advanced concepts and future expectations of Telecommunications Networks. It identifies and examines the most pressing research issues in Telecommunications and it contains chapters written by leading researchers, academics and industry professionals. Telecommunications Networks - Current Status and Future Trends covers surveys of recent publications that investigate key areas of interest such as: IMS, eTOM, 3G/4G, optimization problems, modeling, simulation, quality of service, etc. This book, that is suitable for both PhD and master students, is organized into six sections: New Generation Networks, Quality of Services, Sensor Networks, Telecommunications, Traffic Engineering and Routing

Mobile Ad-Hoc Networks

Being infrastructure-less and without central administration control, wireless ad-hoc networking is playing a more and more important role in extending the coverage of traditional wireless infrastructure (cellular networks, wireless LAN, etc). This book includes state-of-the-art techniques and solutions for wireless ad-hoc networks. It focuses on the following topics in ad-hoc networks: quality-of-service and video communication, routing protocol and cross-layer design. A few interesting problems about security and delay-tolerant networks are also discussed. This book is targeted to provide network engineers and researchers with design guidelines for large scale wireless ad hoc networks