A Hybrid Scheme for Handover in ATM-Based Personal Communication Network

Abstract

In a Personal Communication Networks (PCN), the covered geographical area is typically partitioned into a set of microcells. Each microcell has a Base Station (BS) to exchange radio signals with wireless mobile terminals. Due to the limited range of wireless transceivers, mobile users can communicate only with BSs that reside within the same microcell at any instance. The number of handoffs/handovers during a call will increase as the cell radii decrease, thus affecting the Quality of Service (QoS). Frequent handoff in wireless/mobile networks introduces a new paradigm in the area of network congestion and admission control. The increase in processing load due to demand for service and fast handoffs to mitigate the propagation effect, a high speed backbone network for the PCN to connect BS is required. The ATM technology, which has recently emerged to be a predominant switching technology, is suited to be an infrastructure to interconnect the BSs of the PCN. To support network-wide handoff, new and handoff call requests will compete for connection resources in both the mobile and backbone networks. Handoff calls require a higher congestion related performance, i.e. blocking probability, relative to new calls because forced terminations of ongoing calls due to hand-off call blocking are generally more objectionable then new call blocking from the subscriber's perspective. A hybrid scheme has been proposed for handover in ATM-based PCN, which combines queuing and reservation schemes. In the scheme, FIFO and Measurement Based Priority Scheme (MBPS) queuing discipline [Tekinay & Jabbari, 1992] and the Reserved Channel Scheme (RCS) [Kim et al., 1999] are used. This scheme gives handovers higher priority than queuing or reservation schemes. When reservation is applied on both radio and backbone channels, it leads to significant improvement in QoS. After applying proposed scheme there is a remarkable reduction in Forced Termination Probability (FTP) at the cost of tolerable Call Blocking Probability (CBP).