QoS Management in Wireless Environments
In the past few years, wireless devices have been widely adopted, due to the users' needs for mobility and information anywhere and at any time. New and very powerful wireless hand-held equipments are now available at reasonable costs, and the time is mature to develop new services that can be easily accessed by the final user. Audio/Video streaming over the Internet is no longer a far imagination. VOD should emerge in mid term, with the availability of high bandwidth access medium (ADSL or cable) in the final customer's premises. The next step is to allow mobile users to access these services. In order to enable this vision, research has to be conducted on mobile devices, underlying network and audio/video format. Mobility poses new and challenging issues to be addressed, where QoS management is one of the most crucial, due to the immediate consequences it has on the user's satisfaction. Activities focus on:
- The development of a powerful infrastructure able to provide services, with guaranteed quality, taking care of the user's mobility and of the available resources. Resource reservation in wired networks is a relatively mature area, with some available solutions already on the market. The study of issues concerning the management of mobility in IP-based networks is also arising interest. The combination of both issues, resource reservation and mobility management, is however still at initial state and one of the most interesting arguments in literature is the interaction between QoS mechanisms and mobility protocols. In this activity the effort is focused on the QoS management in mobile environments dealing with the issues related to the resources reservation in terms of bandwidth. Therefore, a microcellular network architecture (a geographical area divided into cells whose size is in the order of some hundred of meters) has been proposed. In particular, the Cellular IP protocol has been used for creating the cellular structure. In order to carry on an effective bandwidth reservation, the routing messages of such protocol have been used. In this way, the reservation can be done in the whole path of the flow in the Cellular IP domain. Each time a handoff takes place, the resources reservation is done hop-by-hop on the new path, by using the Cellular IP packets;
- A low-overhead signalling mechanism able to manage the resources reservation during users' handoffs has been implemented. An efficient Call Admission Control (CAC) is one of the strategic components that a network management policy requires, which defines how to allocate network resources to roaming and new users. In such scenario, the importance of CAC not only in the ingress wireless points, but in the wired network too has been demonstrated. An integrated approach to CAC is then proposed whose advantages are shown through simulation analysis.