this paper, we exploit the use of hierarchical distributed location databases, where each database site covers a specific geographical region and contains location information about all objects residing in it. For highly mobile objects, a scheme based on forwarding pointers enhanced with auxiliary caching techniques is presented, to reduce the cost of the overall network and database traffic generated by frequent location updates. The scheme is extended to support concurrency and failure recovery. Performance is demonstrated through a number of simulation experiments for a range of call to mobility ratios and for a variety of moving and calling behaviors

Performance Issues in Mobile Wireless Networks. (August 1996) P. Krishna, B.S.(Hons.), Regional Engineering College, Rourkela, India; M.S., Texas A&M University Co--Chairs of Advisory Committee: Dr. Dhiraj K. Pradhan Dr. Nitin H. Vaidya The research presented in this dissertation deals with the following performance issues in mobile wireless networks: recovery, location management and routing. The mobile wireless environment poses challenging fault-tolerant data management problems due to the mobility of the users, limited bandwidth on the wireless link, and power restrictions on the mobile hosts. Thus, traditional fault-tolerance schemes cannot be directly applied to these systems. To this effect, extensions to existing traditional recovery schemes are presented which suit this environment. Analytical models are built to analyze the performance of these schemes to determine those environments where a particular recovery scheme is best suited. The trade-off parameters to evaluate the r...

This paper presents a new distributed location management strategy for cellular mobile systems. Its salient features are fast location update and query, load balancing among location servers, and scalability. The strategy employs dynamic hashing techniques and quorums to manage location update and query operations. The proposed strategy does not require a home location register (HLR) to be associated with each mobile node. Location updates and queries for a mobile node are multicast to subsets of location servers, which change with time depending on the location of mobile node/querying node and load on the servers. Simulation experiments demonstrate that such dynamism prevents situations of heavy load on some location servers when mobile nodes are not uniformly distributed in space, or when some mobile nodes have their location updated or queried more often than others. Also, queries return the latest location information of a mobile node with a very high probability. The proposed scheme requires at most one unicast and two rounds of message multicasting for location update and query operations. All multicast messages have a small payload and are restricted to the high bandwidth wired part of the mobile network resulting in low communication overhead. Moreover, if a quorum of location servers gets overloaded, part of its load can be transferred to another lightly loaded quorum using dynamic hashing techniques.

this paper, we use the term mobile terminal (MT) to refer to a portable device or a person who carries it

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. The location information of users can be replicated at various databases in a hierarchy to improve the efficiency of call lookups at the expense of increase in update and storage cost. In this paper, we systematically investigate this problem and propose two solutions. The first solution has optimal lookup and update cost, but the execution time could be exponential to the number of databases. The second solution makes some assumptions and then uses dynamic programming to tackle this problem. Its execution time is dramatically reduced with the result being less optimal. Finally, to further improve efficiency and reducing storage requirements, we propose the incorporation of clustering techniques. 1 Introduction Establishing a connection in a wireless environment requires the location information of the callee, who may be on the move. While this problem is mostly encountered at the data link or networking layer transparently from the layers above it, applications may also need the lo...

In this paper, a dynamic HLR (Home Location Register) scheme for location management in PCS (Personal Communications Service) networks is presented. The proposed scheme provides a dynamic copy of mobile terminal location information in the nearest (current) HLR database. A modified table lookup procedure is also proposed for determining the current HLR easily. It allows the location registration and call delivery to be performed efficiently. An analytical model is developed for studying the performance of the proposed scheme. The performance study shows that the proposed scheme significantly reduces the system overhead for location management in PCS networks.

Distributed systems which use non-stationary communicating objects have to address the problem of managing locations of these objects. We study location management (LM) in the context of dynamic load-balancing for parallel distributed computing and its impact on application performance. We summarize our experience with LM in distributed object-based systems by comparing six location management policies (LMPs). The LMPs are studied within the PREMA framework used mainly for parallel mesh generation and refinement applications. Our experimental study is using a synthetic tunable micro-benchmark and two mesh generation applications. We explain why the commonly adopted in practice Jump Update LMP is efficient for most of our applications and we compare it with the other location management techniques. We show how the performance of a particular LMP can be affected by the application properties and its data layout. Finally, we identify the conditions under which certain LMPs are more beneficial than Jump Update.

Location management is an essential component of many of the current communication net-work technologies that provide services to mobile users, e.g., Mobile Internet Protocol (MobileIP) and Global System for Mobile Communications (GSM). The basic operations of location manage-ment are the pushing of location information (i.e., updating) and the pulling of location informa-tion (i.e., searching) around the network. Current trends in population rise, size of coverage and decrease in size of the registration/location areas greatly impact the overhead of location manage-ment. Performance improvements on location management schemes have been based on the up-date/search trade-off. However, saturation of trade-off optimizations pushes research toward finding new ways to improve performance of location management. Location area overlapping is one such performance improvement with benefits widely known in the research community. However, the limits of the improvements which location area overlapping offers are generally unexplored. In this thesis, new ways of optimizing location management are devised through the study of optimization problems that arise from the application of overlapping registration areas in mobile

Mobile computing has the potential for managing information globally. Data management issues in mobile computing have received some attention in recent times, and the design of adaptive broadcast protocols has been posed as an important problem. Such protocols are employed by database servers to decide on the content of broadcasts dynamically, in response to client mobility and demand patterns. In this paper we design such protocols and also propose efficient retrieval strategies that may be employed by clients to download information from broadcasts. The goal is to design cooperative strategies between server and client to provide access to information in such a way as to minimize energy expenditure by clients. We evaluate the performance of our protocols analytically. 1 Introduction One of the most important information dissemination strategies in the current fast paced corporate and personal environments is to employ wireless networks. Furthermore, the data-hungry users who access ...