To accommodate the increase in user population in future personal communication systems, hierarchical architectures of location databases have been proposed. In this paper, a scheme based on forwarding pointers is presented, that reduces the cost of the overall network and database traffic generated by frequent location updates in such hierarchical architectures. To reduce the number of forwarding pointers that need to be traversed to locate a user, auxiliary caching techniques are presented. Various conditions for purging the chain of forwarding pointers and updating the database are also introduced. Special care is given so that the scheme correctly supports the concurrent execution of updates and lookups. The applicability of the scheme and the performance of the caching techniques are demonstrated through a number of experiments for a range of call to mobility ratios and for a variety of moving and calling behaviors. Keywords: Mobile Computing, Distributed Database Systems, Locati...

Location management is a fundamental problem in mobile computing systems. Existing industry standards employ centralized location management schemes. Centralized schemes are not highly scalable. This paper presents a new, distributed location management strategy for 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. Location information of a mobile host is replicated at a subset of location servers. The set of location servers associated with a mobile host changes with time, depending on the location of mobile hosts and load on the servers. This dynamism prevents situations of heavy load (location update and query messages) on some location servers when the mobile hosts are not uniformly distributed in space, or when some mobile hosts have their location updated or queried more often than others. New lo...

Abstract. The Mobile IP (MIP) protocol for IP version 4 as being standardized by the Internet community provides continuous Internet connectivity to mobile hosts, without requiring any changes to existing routers and higher-layer applications. We propose an alternative protocol, Mobile IP with Location Registers (MIP-LR) which is closer to the “service node ” database approach used in the Public Switched Telephone Network (PSTN): before launching a packet to the mobile host, the sender first queries a database to obtain the recipient’s current location. MIP-LR is designed for operation in enterprise environments or within logical administrative domains, as it requires a sending host to be aware which hosts are potentially mobile and implement the MIP-LR protocol. The benefits of MIP-LR are that potentially long routes, called “triangle routes”, from the sender to the mobile host are avoided, encapsulation of packets sent to a mobile host is not required, the load on the home network as well as the home and foreign agents is reduced, and there is substantially improved interoperability with protocols such as RSVP for providing QoS guarantees. We carry out a simplified average-case analysis of the costs and benefits of MIP-LR and show it can result in significant reductions in mean network costs compared to MIP. 1.

We are building a wide-area location service that tracks the current location of mobile and replicated objects. The location service should support up to 10 12 objects on a worldwide scale. To support this huge number of objects, the workload of the location service is distributed over multiple hosts. Our load distribution method is unique in that it is aware of the (geographical) location of the hosts it uses. By using this location knowledge when distributing the workload, the distribution mechanism enforces locality of operations in the location service. Enforcing locality minimizes the use of global network resources by the location service and thereby enhances its scalability. We also show how this location-aware load distribution mechanism can be implemented. 1 Introduction Objects provide an easy way to model both applications and system services. It is therefore easy to understand that the use of objects as a design and implementation method has become popular, for example...

Many mobile applications require some knowledge about the current geographic locations of the mobile objects involved. Therefore, services exist that can store and retrieve the position of mobile objects in an efficient and scalable way. More advanced location-aware applications, however, require additional functionality, like determining all mobile objects inside a certain geographic area (range query). This functionality is not supported by existing services on a large scale yet. In this paper, we present a generic large-scale location service. We describe the location service model, defining the semantics of position, range and nearest neighbor queries. A hierarchical distributed architecture is presented, which can efficiently process these queries, and the structure of a main-memory database for efficiently storing and retrieving position information on a location server. Finally, through measurements on a first prototype of this architecture, we show the feasibility of such a location service.

Source messages intended for a mobile host can be routed in one of two ways. Either the source knows the direct route to the mobile host, and is informed of all location changes by the mobile host (informed routing), or the source directs messages to a home agent that forwards messages to the mobile host (triangle routing). When the rate at which the mobile host changes location and the rate at which messages are directed to the mobile host are known and fixed, we show that the optimal routing policy is described by a threshold rule that depends on the normalized differential route cost between triangle and informed routing and the call to mobility ratio (source messaging rate divided by location update rate). Since the call to mobility ratio may not be known a priori or may change slowly with time, we also derive an adaptive policy selection algorithm. The policy is derived from a maximum likelihood estimate of the call to mobility ratio based on observations of message arrivals and l...

This paper studies the eectiveness of a fully distributed location management scheme for PCS networks. Using analytical modeling and numerical simulation, we show that fully replicating location information is both appropriate and ecient for small PCS networks. Then, we extend the scheme in a hierarchical environment so as to reduce overhead and scale to large PCS networks. Through extensive numerical results, we show the superiority of our scheme compared to the current IS-41 standard. Keywords: Location Management; PCS Networks; Centralized versus Distributed; Performance Analysis. 1. Introduction One of the challenging tasks in a Personal Communication Services (PCS) network is to eciently maintain the location of PCS subscribers who move around freely with their wireless unit (hereafter called mobile host or mobile for short). In North America, Telecommunications Industry Association's interim

In a Personal Communication Services(PCS) Network, mobile hosts communicate with other mobile hosts through base stations on a wired (static) network. The mobile hosts connect to different base stations through wireless links and the base stations to which mobile hosts are connected change depending on the current location of the mobile hosts. In this environment, the problem of efficiently delivering a multicast message from one mobile host to a group of other mobile hosts becomes challenging. In this paper, we present a multicast protocol that delivers multicast messages from a mobile host to a group of other mobile hosts without flooding the wired network. The multicast protocol is built on top of a user location strategy that should follow one of three models of user location described in the paper. The basic multicast protocol proposed guarantees exactly-once message delivery to all mobile hosts in the multicast group and also ensures that multicast messages are delivere...

This paper presents a novel location management technique, HOPPER, that is designed to support in a scalable and efficient manner nongeographical (lifelong) personal numbers in Personal Communications Services (PCS). Performance comparisons between our scheme and other schemes are derived from large scale simulations using a realistic traffic modeling framework for the ten largest cities of the United States. Results show that, in addition to inherently providing non-geographical numbers, the proposed scheme significantly improves lookup performance and requires relatively little database access and network signaling resources.

This paper describes current and proposed protocols for mobility management for PLMNbased networks, Mobile IP, Wireless ATM, and Satellite networks. The integration of these networks will be discussed in the context of the next evolutionary step of wireless communication networks. First, a review is provided of location management algorithms for PCS implemented over a PLMN network. The latest protocol changes for location registration and handoff are investigated for Mobile IP, followed by a discussion of proposed protocols for Wireless ATM and Satellite networks. Finally, an outline of open problems to be addresses by the next generation of wireless network service is discussed. Key Words: Mobility Management, Location Management, Paging, Handoff, IMT 2000, PLMN, PCS, PSTN, Mobile IP, Wireless ATM, Satellite This work was supported by DoD, National Security Agency under grant number MDA904-97-C-1105-0003. 1 Introduction The commercial proliferation of cellular voice and limited ...