Improvements of the ABR loop performances in a wireless ATM network

There were a number of research activities to promote multimedia and wireless applications rate. Efficient flow and congestion control mechanisms are needed in high-speed networks to meet the new constraints and to offer best quality of service. Mechanisms founded on the rate adjustment had a particular interest. Wireless ATM technology, based on a number of wired ATM protocols and services, is considered a solution for these requirements. It provides multimedia services to mobile users and promises a support of quality of service (QoS). Otherwise, the WATM performances depend on the adopted mechanisms for flow and congestion control. Hence, several factors can influence this mechanism such as error probability on the wireless link and handover procedure type. The ABR service, standardized by the ATM forum, is the most widespread traffic congestion control mechanism permitting to provide fair sharing resources. ABR specifications were designed to enable efficient bandwidth allocation and low cell loss ratio. This paper addresses the interaction among the flow control algorithm, the handover procedure, and the resulting QoS characteristics. We present a novel ABR congestion control algorithm which is adaptive to changing network conditions and robust to terminal mobility. The objective of this algorithm is to achieve a high utilization factor and to maintain the compatibility between the wired and wireless link constraints. Therefore, it was important to develop the necessary mobility enhancements, such as handovers and radio resource management. This approach guarantees the development of an effective control strategy for the congestion control mechanism.