Abstract
Abstract Handoff and mobility management are the essential problems of wireless communication systems. When the MS travels across the cell boundary, a new channel are required to continue the call; these activities are called handoff in general. A strategy called Forced-Jump is presented in this dissertation, capable of making use of the overlap region of cell boundary to raise the utilization of channel resources. The Forced-Jump strategy augments the existing handoff scheme, with the objective of reducing rate of forced termination. When handoff request occurs to a cell in which all channels are occupied, the base station (BS) of this cell attempts to pick up a proper mobile station (MS) in overlap areas of this cell and forces it to use the channel of its neighbor. The mobility management consists of the mechanisms to track user’s location and find the users. Tracking of the mobile user is very important since the mobile users roam around the network. The movement of every mobile unit is noted in the registration records in VLR (Visit Location Register) of the corresponding Registration Area (RA) as well as HLR (Home Location Register) database. E.g. IS-41 is a well-defined implementation for managing location update and mobile tracking within wireless system and has been applied in famous AMPS cellular phone system. In IS-41 standard, RA might consist of one or more cell(s), it performs roaming management by a hierarchical database structure (HLR, and VLR). Each RA has a VLR to record the location of visiting mobiles. The discussion of mobility management issues in this dissertation were categorized into: 1) modified Dual Group method (single HLR solution), and 2) Fixed Pointer Method (multiple HLRs solution). The Group method can effectively reduce the loading of the network caused by tracking mobile users in a mobile cellular system because it joins several cells to form a group. Instead of performing registration and deresgistration for each individual cell, the Group Method performs these tasks on a group scale. Moreover, the Dual Group Method saves network resources because it eliminates unnecessary location updates due to its fewer group boundary passes. The main idea of fixed pointer distributed HLR is using fixed pointers to link distributed database. Each of the database contains part of total system information of the system and some pointers. The pointers point to the location of real data. Since there are pointers point to the data directly, the system can get the required information as soon as possible.