Date of Award

5-12-2005

Degree Type

Closed Thesis

Degree Name

Master of Science (MS)

Department

Computer Science

First Advisor

Dr. Anu G. Bourgeois - Chair

Second Advisor

Dr. Raj Sunderraman

Third Advisor

Dr. Alex Zelikovsky

Abstract

Location Management is defined as the process of tracking the position of a mobile terminal when it moves to its associated area within the network. This allows the network to detect the mobile user’s path for the purpose of call delivery. The location management schema in a public-LAN mobile network (IS-41 and GSM) is based on centralized two-tier database architecture. The root level is called the Home Location Register (HLR) and the second level is called the Visitor Location Register (VLR). The HLR permanently stores all the mobile users’ location information and the types of services subscribed in the user’s profile database. The VLR stores the location information whenever a user registered in the HLR moves to its related location area within the network. By contacting the HLR, the VLR authenticates and updates the mobile user’s current position when a mobile terminal moves from one location area to another. The HLR then updates the mobile terminal’s new location information and removes the mobile terminal from its previous VLR. There can be multiple VLR’s under each HLR in a network. In the current location management schema, all the information requests, queries, acknowledgements have to go through the HLR. This results in excessive overload at the HLR. This overload becomes high when the number of mobile terminals increases within the network. The heavy traffic at the root (HLR) may cause congestion, degradation of the bandwidth at the root and hence becomes a major bottleneck for the entire network. To solve this congestion/bottleneck problem, a modified iterative protocol with VLR cache was introduced, where the VLRs in the network handle all de-registration, registration and acknowledgement of messages. The HLR only handles updating the location information of the mobile terminal in its database. This reduced the excess load/traffic experienced at the HLR thus improving the network’s performance. The modified protocol was tested with different cache replacement policies such as First-In First-Out (FIFO), Random and Least Frequently Visited (LFV) with uniform traffic with random mobile terminal movement. In this thesis report, we extend the previous work in the modified iterative protocol by 1) increasing the topography of the network, to analyze the impact of network’s size on performance and 2) changing the mobile terminal traffic pattern from uniform traffic with random mobile terminal movement to non-uniform traffic with unbalanced probability movement. With these changes, we analyzed the modified protocol’s performance with different cache replacement policies (FIFO, LFV and Random) under uniform traffic with random movement and non-uniform traffic with unbalanced probability movement.

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