Performance models of handover protocols and buffering policies in mobile wireless ATM networks

Due to the connection-oriented nature of the asynchronous transfer mode (ATM), one of the challenges in mobile wireless ATM (WATM) systems is the management of terminal handovers. When ATM connections are reestablished to follow terminals moving between areas covered by distinct base stations, seamless handover protocols are necessary to guarantee that ATM cells are delivered to terminals in the correct order, with cell loss rate and delay that satisfy the contracted quality of service (QoS). A promising approach to meet QoS requirements is based on the use of handover buffers at the (destination) base station, where transmitted cells are stored while the connection is being reestablished. Up to date, only simulation and experimental results are available to determine the performance of such protocols and buffering schemes. This paper presents the first attempt to develop an analytical modeling approach to estimate the performance of handover protocols making use of handover buffers at the base station. By incorporating several approximations, the proposed models allow designers to simultaneously take into account numerous system parameters, including handover buffer size, sustainable and peak cell rates of the ATM connection, terminal offered load, and time needed to reestablish the ATM connection. Analytical performance predictions are shown to closely match results of detailed simulation experiments, thus demonstrating the suitability of the proposed modeling framework for the selection of the most adequate solution to handle handover and provide the QoS required by end users.