Mobilidade em redes wimax: um estudo sobre os processos de handover, consumo de energia e qualidade de serviço

Abstract

Lately, networks based in wireless technology have grown due to many factors, such as commercial success of the mobile telephony, the continuous grown number of mobile users and Internet users and new multimedia applications. New technologies are being developed, such as WIMAX IEEE 802.16 e IEEE 802.16e. Networks based in WIMAX IEEE 802.16 are used in broadband metropolitan areas, to solve the “last mile” problem, while IEEE standard 802.16e are used to support mobility in this environment. However, any technology that offers mobility must have a mechanism capable to deal with the change of cells while the users are in movement, without interrupting their connections. This concept is called transparent handover. In this context, many solutions are being proposed to minimize the losses caused by the handover processes [2] [14]. In [2], the fast handover algorithm is proposed, aiming to reduce delay and packages loss of real-time downlink flows, improving the handover process in the link layer level (link-layer handover). Through this algorithm, a mobile station (MS) can receive data from the downlink channel of its future base station (BS), through a new management message sent from this BS during the handover process, just after the downlink channel synchronization, but before the uplink channel synchronization process. In [14], the solution proposed is based in a management infrastructure that anticipates where the next handover will probably take place, based on the behavior of users movement profile, allowing proactive reserve of resources for the chosen cell. This permits the maximization use of networks resources and provision of better QoS to different users classes, becoming a very important requirement for WIMAX networks. The objective of this work is to extend the research initiated in [14] that explores the profile of user movement behavior to maximize the network efficiency and provides better QoS for different users class, which easily integrates with WiMAX technology. An algorithm is proposed that, in real-time, makes use of the user profile to reduce the set of probable cells where the next handover will take place, taking in account the type of user, the service being used, and the network availability, allowing pro-active resources reservation in the chosen cells that will be used after the handover. This work describes the handover process in details, identifies main aspects to be observed while implementing IEEE 802.16e networks and finally details the main characteristics that must be present when implementing more efficient methods to support the handover process in WiMax networks, such as mobility models and prediction, and methods of energy consumption reduction.