Speed-Sensitive Handover Scheme over IEEE 802.16 Multi-Relay Networks

Abstract

Abstract —Multi-Relay Networks should accommodate mobile users of various speeds. The cellular system should meet the minimum residency time requirements for handover calls while considering an efficient use of available channels. In this paper, we design speed-sensitive handover under dynamic hierarchical cellular systems, in which mobile users are classified according to the mean speed of mobile users and each class has its cellular layer. In order to meet the minimum residency time, the cell size of each cellular layer is dynamically determined depending on the distributions of mean speeds of mobile users. Since the speed-dependent non-preferred cell can provide a secondary resource, overflow and take-back schemes are adopted in the system. We develop analytical models to study the performance of the proposed system, and show that the optimal cell size improves the blocking probability. Keywords —Multi-Relay Networks, Handover 1. I NTRODUCTION The existing IEEE 802.16 is a series of Wireless Broadband standards known as WiMAX as an important technology for providing high-speed Internet access to home and business sub-scribers in a wide area cellular network[1]. Handover is a key factor for the quality of wireless communication services. Due to the geographical problem, significant data loss occurrs, the coverage region for high data rates is decreased, and even dead spot areas in the coverage region occurr. IEEE 802.16j adopts multihop or relay technologies in order to eliminate dead spot areas and extend the coverage region. In IEEE 802.16j networks, the Relay Stations (RSs) relay sig-naling and data messages between the Multihop Relay BS (MR-BS) and the Mobile Station (MS)[2, 3]. Therefore, handover issues for the RS on IEEE 802.16j have been carried out[4]. The increasing demands for mobile communications are proceeding with a strong tendency toward increasing need for high traffic capacity and mobility in the access links within the wire-less links[5, 6]. Since the micro-cell of the micro-cellular systems makes an efficient use of available channels by using low-power transmitters to allow channel reuse at much smaller dis-tances, the micro-cellular systems with an extremely small cell radius can meet the traffic de-mand[7, 8]. However, the micro-cell increases the number of cell boundary crossings for high-mobility users, and the increasing handover rates of ongoing calls may cause an excessive proc-essing load in the network. Furthermore, the handover calls of fast-moving users cannot meet