A connection-level call admission control using genetic algorithm for MultiClass multimedia services in wireless networks

Call admission control in a wireless cell in a personal communication system (PCS) can be modeled as an M/M/C/C queuing system with m classes of users. Semi-Markov Decision Process (SMDP) can be used to optimize channel utilization with upper bounds on handoff blocking probabilities as Quality of Service constraints. However, this method is too time-consuming and therefore it fails when state space and action space are large. In this paper, we apply a genetic algorithm approach to address the situation when the SMDP approach fails. We code call admission control decisions as binary strings, where a value of “1” in the position i (i=1,…m) of a decision string stands for the decision of accepting a call in class-i; a value of “0” in the position i of the decision string stands for the decision of rejecting a call in class-i. The coded binary strings are feed into the genetic algorithm, and the resulting binary strings are founded to be near optimal call admission control decisions. Simulation results from the genetic algorithm are compared with the optimal solutions obtained from linear programming for the SMDP approach. The results reveal that the genetic algorithm approximates the optimal approach very well with less complexity

A New CAC Policy Based on Traffic Characterization in Cellular Networks

The Call Admission Control (CAC) method presented in this paper is based on the statistical properties of the network’s traffic variables. It probabilistically estimates the time until the release of a seized channel: the admission control depends on the computed mean remaining time averaged along all channels at a specific instant and on a time threshold. The policy produces a smooth transition between the QoS metrics, giving the operator the freedom to design the network at the desired QoS point. Another valuable property is that the algorithm is straightforward and fed only by simple teletraffic metrics: distribution and the first and second moments of Channel Holding Time (CHT). Simplicity is important for a CAC method because decisions for accepting or rejecting calls must be computed quickly and frequently.Peer Reviewe

DISEÑO ÓPTIMO DE POLÍTICAS DE CONTROL DE ADMISIÓN DEL TIPO MULTIPLE FRACTIONAL GUARD CHANNEL (MFGC) PARA REDES MÓVILES MULTISERVICIO

Las políticas de CA MFGC son probablemente las que han suscitado un mayor interés en el entorno móvil. Sin embargo, realizar el ajuste de parámetros de este tipo de políticas entraña un esfuerzo computacional que puede llegar a ser prohibitivo. Para hacer frente a esta limitaciones se proponen algunos algoritmos basados en aproximaciones númerica. Abstract: Multiple Fractional Guard Channel (MFGC) policy provides good results and its implementation is quite simple. Nevertheless, computing the optimal parameters setting of this policy can constitute a high computational cost. To face these computational limitations some algorithms based in numerical approximations are proposed.Bernal Mor, E. (2007). DISEÑO ÓPTIMO DE POLÍTICAS DE CONTROL DE ADMISIÓN DEL TIPO MULTIPLE FRACTIONAL GUARD CHANNEL (MFGC) PARA REDES MÓVILES MULTISERVICIO. http://hdl.handle.net/10251/12625Archivo delegad

Diseño óptimo de políticas de Control de Admisión (CA) del tipo Multiple Fractional Guard Channel (MFGC) para redes móviles multiservicio

[ES] La necesidad de garantizar Calidad de Servicio (QoS) en escenarios móviles multiservicio, lleva a explorar nuevas estrategias que permitan minimizar la probabilidad de terminación forzosa de una conexión debido a un fallo de handover por insuficiencia de recursos en la celda destino. Estas estrategias deben estar coordinadas con los sistemas de Control de Admisión (CA). Las políticas de CA del tipo MFGC son probablemente las que han suscitado un mayor interés pues consiguen unas buenas prestaciones y su implementación es bastante simple. Sin embargo, realizar el ajuste de parámetros de este tipo de políticas de una manera óptima entraña un esfuerzo computacional que puede llegar a ser prohibitivo. Para hacer frente a esta limitaciones computacionales se han propuesto algunos algoritmos basados en aproximaciones numéricas. De los resultados obtenidos, se observa que el coste computacional necesario puede llegar a ser muy elevado en algoritmos previos descritos en la literatura. La aproximación basada en fórmulas recurrentes no ofrece resultados totalmente convincentes, pues la configuración calculada a partir de éste no cumple los objetivos de QoS. Finalmente se propone un algoritmo que mejora los tiempos de cálculo respecto al algoritmo previo y obtiene resultados fiables, pero es mucho más lento que el algoritmo que se basa en la aproximación.[EN] The need to guarantee certain QoS requirements in multiservice cellular networks has led to explore new strategies to minimize blocking probabilities. These strategies must be coordinated with admission control systems (CA). In this paper we study Multiple Fractional Guard Channel (MFGC) policy which provides good results and its implementation is quite simple. Nevertheless, computing the optimal parameters setting of this policy can constitute a high computational cost. To face these computational limitations some algorithms based in numerical approximations are proposed. The obtained results show that the algorithm based in one-dimensional recursion formulas is not a good approximation since the policy configuration obtained do not fulfills the QoS constrains. But this approximation can be useful to accelerate a previous algorithm appeared in the literature. Finally, we propose another algorithm which outperforms this previous algorithm in terms of computational cost and fulfills the QoS constraints, but it is slower than the algorithm based in one-dimensional recursion formulas.Bernal Mor, E. (2008). Diseño óptimo de políticas de Control de Admisión (CA) del tipo Multiple Fractional Guard Channel (MFGC) para redes móviles multiservicio. http://hdl.handle.net/10251/27132.Archivo delegad

Robustness of optimal channel reservation using handover prediction in multiservice wireless networks

The aim of our study is to obtain theoretical limits for the gain that can be expected when using handover prediction and to determine the sensitivity of the system performance against different parameters. We apply an average-reward reinforcement learning approach based on afterstates to the design of optimal admission control policies in mobile multimedia cellular networks where predictive information related to the occurrence of future handovers is available. We consider a type of predictor that labels active mobile terminals in the cell neighborhood a fixed amount of time before handovers are predicted to occur, which we call the anticipation time. The admission controller exploits this information to reserve resources efficiently. We show that there exists an optimum value for the anticipation time at which the highest performance gain is obtained. Although the optimum anticipation time depends on system parameters, we find that its value changes very little when the system parameters vary within a reasonable range. We also find that, in terms of system performance, deploying prediction is always advantageous when compared to a system without prediction, even when the system parameters are estimated with poor precision. © Springer Science+Business Media, LLC 2012.The authors would like to thank the reviewers for their valuable comments that helped to improve the quality of the paper. This work has been supported by the Spanish Ministry of Education and Science and European Comission (30% PGE, 70% FEDER) under projects TIN2008-06739-C04-02 and TIN2010-21378-C02-02 and by Comunidad de Madrid through project S-2009/TIC-1468.Martínez Bauset, J.; Giménez Guzmán, JM.; Pla, V. (2012). Robustness of optimal channel reservation using handover prediction in multiservice wireless networks. 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Contribución al control de admisión en redes móviles celulares multiservicio

El trabajo contenido en esta tesis trata de contribuir en la caracterización, comprensión y desarrollo de mecanismos para la apropiada gestión de los recursos en las redes móviles celulares. En concreto, la aportación que comprende este esfuerzo incluye el desarrollo de modelos, algoritmos y métodos para estudiar el control de admisión desde una perspectiva estacionaria, y el desarrollo de esquemas que optimicen el comportamiento del control de admisión de manera adaptativa con respecto a las situaciones no estacionarias de los sistemas reales.García Roger, D. (2007). Contribución al control de admisión en redes móviles celulares multiservicio [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/1845Palanci

Modelado y evaluación de la gestión de recursos en redes móviles celulares

En la última década las redes móviles celulares han experimentado un enorme crecimiento. Asimismo el aumento del número de servicios y el ancho de banda que requieren hace necesario un correcto modelado y gestión de recursos. Este trabajo pretende ser una contribución al desarrollo de modelos para el estudio y la evaluación de la gestión de recursos radio en redes móviles celulares. Más concretamente, se ha pretendido profundizar en el estudio de modelos de reintentos. Estos modelos son de gran utilidad para la caracterización de diferentes aspectos de funcionamiento. Tradicionalmente, se ha entendido por sistema de reintentos aquel sistema en que los usuarios que son bloqueados, tratan de acceder de nuevo, tras un tiempo de espera. Esta es una característica propia del comportamiento humano que no debe obviarse en el modelado de sistemas de comunicaciones, puesto que puede tener un gran impacto en las prestaciones ofrecidas por el sistema. Adicionalmente, en las redes móviles celulares, por su estructura y características propias, podemos encontrar este efecto no sólo debido al comportamiento humano, sino que también puede deberse a la gestión de los handovers. Este tipo de reintentos, incluido en el estándar de GSM, permite realizar un número máximo de reintentos consecutivos, mientras que el terminal se encuentra en el área de handover, sin que el usuario intervenga. Es posible encontrar otro tipo de sistemas de reintentos que caracterizan toda una serie de nuevas aplicaciones. Se trata de aplicaciones que, en caso de bloqueo, permiten reintentar el acceso disminuyendo el número de recursos solicitado. Así, aparecen las aplicaciones rate adaptive en que, según el grado de congestión, se ofrece un servicio de mayor o menor calidad. Este tipo de modelo resulta de especial interés para tratar aplicaciones como VoIP o servicios de videoconferencia para las que se han desarrollado codecs que permiten adaptar la tasa de servicio a las condiciones de la red.Doménech Benlloch, MJ. (2009). Modelado y evaluación de la gestión de recursos en redes móviles celulares [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/8319Palanci