A channel allocation algorithm for OSA-Enabled IEEE 802.11 WLANs

Channel allocation problem is a major challenge in wireless local area networks (WLANs), especially in dense deployments of access points (APs) where congestion of the unlicensed spectrum bands (i.e., ISM bands) could undermine achieved network performance. This paper analyses the possibility to alleviate congestion of the ISM band by allowing some APs to use additional channels located in licensed bands in an opportunistic manner whenever licensee services (i.e., primary users) are not affected. Availability of these additional channels in licensed bands is assumed not to be the same for all the APs. Based on this assumption, we formulate the problem for the channel assignment as a Binary Linear Programming (BLP) problem, which allows us to obtain an optimal solution despite an elevated execution time. We also develop a heuristic method based on building a Minimum Spanning Tree (MST) graph attending to interference conditions that is able to find nearoptimal solutions with a shorter execution time. Results are provided to assess the benefits of such a proposal under different WLAN deployment situations and primary channel availability conditions.Postprint (published version

AP Deployment Research Based on Physical Distance and Channel Isolation

Aiming at the problem of inefficiency of wireless local area networks (WLAN) access point (AP) deployment in urban environment, a new algorithm for AP deployment based on physical distance and channel isolation (DPDCI) is proposed. First, it detects the position information of deployed APs and then calculates the interference penalty factor combined with physical distance and channel isolation, and finally gets the optimal location and channel of the new AP through the genetic algorithm. Comparing with NOOCA algorithm and NOFA-2 algorithm, the results of numerical simulation show that the new algorithm can minimize the mutual interference between basic service sets (BSS), can ensure the maximum of throughput based on quality of service (QoS) in BSS, and can effectively improve the system performance

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

Impacto de la Movilidad sobre el Rendimiento de Sistemas de Comunicaciones Inalámbricas

Este proyecto pretende entregar una herramienta de análisis sobre el impacto de movilidad a través de los algoritmos de asignación de canal usando tanto las bandas ISM como la banda primarias PB orientando al estándar IEEE 802.11, generando para ello diversos escenarios en los cuales se colocarán determinadas cantidades de puntos de acceso (AP). Se definirá un factor de interferencia o penalidad mismo que será usado en los algoritmos, éste estará influenciado por la ubicación relativa de un determinado AP en comparación con la ubicación de sus AP’s vecinos, así como por el canal candidato que será probado en el AP en que está siendo ejecutado el algoritmo en comparación con los canales establecidos de los otros AP’s. Sobre esta base, se evaluara el rendimiento de tres algoritmos de asignación de canal no orientados a la solución de acceso oportunista al espectro sino más bien a la distribución de canales de forma equiprobable entre ambas bandas de frecuencias tanto ISM como PB, cada uno con su procedimiento en particular. La problemática será planteada, procesada y analizada mediante el uso de la herramienta MATLAB, donde se generaran los diversos escenarios y se ejecutara n sobre ellos los algoritmos a tratar.This project aims to provide a tool of analysis of the impact of mobility through the channel assignment algorithms using both the ISM bands as the primary band PB guiding the IEEE 802.11 standard, creating for it several scenarios in which certain amounts are placed Access point (AP). A factor of interference or penalty which will be used in the algorithms will be defined, it will be influenced by the relative location of a particular AP in comparison to the location of your AP's neighbors as well as by the candidate channel that will be tested in the AP it is being executed algorithm compared to other established channels AP's. On this basis, the performance of three channel assignment algorithms not oriented to the solution of opportunistic spectrum access but rather to equiprobable distribution channels form between the two ISM frequency bands as PB therefore be assessed, each with its particular procedure. The issue will be raised, processed and analyzed using the MATLAB tool where various scenarios were generated and executed on them algorithms to try

Performance analysis of channel assignment schemes for coordinated cognitive WLAN networks

Nowadays local wireless networks are very used by an elevated number of people and its use continues rising. This provokes an increase of the interference and as consequence, congestion in the non-licensed band of 2.4GHz, caused by the increase of users in a given zone and thus, the limitation of channels offered by this band. As a solution to this problem, in this project it is studied the possibility of using additional channels from licensed bands used for other radio-communications services. The use of these channels in the local network (named in this context as secondary user of this spectrum) is done in an opportunistic manner, when ever it does not provoke any interference to the users of the service which have the rights to use this spectrum (named primary users in this context), since these ones have priority to access these bands of the spectrum. As a first approximation to the solution of the assignment problem, it is studied the behaviour of a random channel assignment in a scenario with a certain density of local networks that can generate interference between them and where the availability of the primary channel for opportunistic use is not homogeneous. Later, stated the possibility of improving the level of interference even with a random channel assignment, there are proposed two channel assignment methods designed to have in concern the availability of primary channels. The first method is set out through the formulation of an Integer Linear Programming (ILP) problem, which allows obtaining an optimal solution but with an elevated execution time. The other method is an heuristic one based on obtaining a Minimum Spanning Tree (MST) on interference terms, which allows to obtain near-optimal solutions in less time of execution. In the project it is done a detailed comparison of these two methods to contrast the advantages of each one. Finally, there are identified some aspects of the implementation of these methods in a real scenario