QoS adaptation in wireless broadband networks.

摘要

The growth of wireless communications coupled with the rapid developments in asynchronous transfer mode (ATM) networking technology makes broadband mobile communication possible. Mobility in a wireless network comes with many complexities that are not encountered in a fixed network. While many protocols have been devised to deal with handovers in wireless broadband networks, most of them deal with a partial list of the mobility-induced problems. A list of these problems includes the crossed path problem, the moveback problem, and the QoS adaptation problem. This dissertation introduces a protocol that seamlessly deal with these problems in wireless broadband networks, while at the same time minimizes handover latency and cell delay. As far as we know, no such protocol has ever existed in the literature.; The crossed path problem arises when both ends of a connection turn out to be MHs, and both attempt to handover simultaneously. This problem has been introduced in [TZTT02]. The moveback problem has been noticed because of the local mobility of MHs. It's unacceptable to set up the partial path that was recently torn down, and tear down the partial path that was recently set up. Postponing tear-down is proposed to solve this problem. Instability in QoS or routing adaptation can exist for VC-based network as shown in [BG92], and later in [TT01] in the context of high speed wireless networks. Some VCs could be torn down even though there was enough bandwidth. Sometimes, unbalanced load among cells cause unnecessary call blocks. By combining VC-level load balancing and cell-level load balancing, a solution for QoS adaptation can be achieved.