Consider a database that represents information about moving objects and their location. For example, for a database representing the location of taxi-cabs a typical query may be: retrieve the free cabs that are currently within 1 mile of 33 N. Michigan Ave., Chicago (to pick-up a customer). In the military, moving objects database applications arise in the context of the digital battlefield, and in the civilian industry they arise in transportation systems. Currently, moving objects database applications are being developed in an ad hoc fashion. Database Management System (DBMS) technology provides a potential foundation upon which to develop these applications, however, DBMS's are currently not used for this purpose. The reason is that there is a critical set of capabilities that are needed by moving objects database applications and are lacking in existing DBMS's. The objective of our Databases fOr MovINg Objects (DOMINO) project is to build an envelope containing these capabilities...

In this paper we consider databases representing information about moving objects (e.g. vehicles), particularly their location. We address the problems of updating and querying such databases. Specifically, the update problem is to determine when the location of a moving object in the database (namely its database location) should be updated. We answer this question by proposing an information cost model that captures uncertainty, deviation, and communication. Then we analyze dead-reckoning policies, namely policies that update the database location whenever the distance between the actual location and the database location exceeds a given threshold, x. Deadreckoning is the prevalent approach in military applications, and our cost model enables us to determine the threshold x. We propose several dead-reckoning policies and we compare their performance by simulation. Then we consider the problem of processing range queries in the database. An example of a range query is `retrieve the ob...

Mobile wireless networks pose interesting challenges for routing system design. To produce feasible routes in a mobile wireless network, a routing system must be able to accommodate roving users, changing network topology, and fluctuating link quality. We discuss the impact of node mobility and wireless communication on routing system design, and we survey the set of techniques employed in or proposed for routing in mobile wireless networks.

We describe a service for locating distributed objects identified by location-independent object identifiers. An object in our model is physically distributed, with multiple active copies on different machines. Processes must bind to an object in order to invoke its methods. Part of the binding protocol is concerned with contacting the object, which offers one or more contact points. A contact point is associated with an active part of the distributed object, and describes exactly how and where initial communication should take place. An object can change its contact points in the course of time, thus exhibiting migration behavior. Finding an object’s contact points is the essence of our location service. Our model is based on a worldwide distributed search tree, capable of handling trillions of distributed objects. The tree adapts dynamically to individual migration patterns. By exploiting an object’s relative stability with respect to a region, combined with the use of pointer caches, an object can be contacted through a search path of only length two. We present the architecture of our location service, including its update and lookup mechanism, and discuss its scalability. 1

We consider the problem of managing the information required to locate users in a wireless communication system, with a focus on designing and evaluating location management techniques that are efficient, scalable, and flexible. The three key contributions of this paper are: (1) A family of location management techniques, HiPER (for Hierarchical ProfilE Replication), that efficiently provide life-long (non-geographic) numbering with fast location lookup; (2) Pleiades, a scalable event-driven wireless system simulator with realistic calling and mobility patterns derived from several months of real traffic traces; and (3) multi-day simulations comparing our proposed location management techniques with current and previously proposed techniques on a realistic geographical and network topology. Research supported by the Center for Telecommunications and the Center for Integrated Systems at Stanford University, and by equipment grants from Digital and IBM Corporations. 1 Introduction I...

A personal communications network (PCN) location tracking scheme called local anchoring is introduced which reduces the signaling cost as compared to the location management strategy proposed in the IS-41 standard. Local anchoring reduces the number of location registration messages between the home location register (HLR) and the visitor location registers (VLR’s) in a way that location change is reported to a nearby VLR called the local anchor (LA) instead of to the HLR. This method successfully reduces the cost for location tracking when the call arrival rate is low relative to the mobility rate and the cost for location registration is high. A dynamic local anchoring mechanism is then introduced which dynamically selects the LA such that the expected cost for location registration and call delivery can be further reduced. It is demonstrated that the cost of dynamic local anchoring is always lower than or equal to that of the IS-41 scheme.

In this paper, we propose a fast and efficient handoff scheme to handle the movements of mobile nodes among small wireless cells at the fringes of the Internet. Our scheme adopts a hierarchical mobility management architecture to restrict the handoff processing overheads within the vicinity of the mobile node, and uses multicast as the packet forwarding mechanism to deliver packets to multiple base stations within the vicinity of the mobile node to achieve fast handoff performance. Our scheme is based on the Internet Protocol (IP) and is compatible with Mobile IP and its route optimization option. We also present simulation results for our simulation using the Network Simulator (ns2). The simulations show that our handoff scheme is fast enough to meet the requirements of an interactive voice communication session. The first packet from the new base station arrives at the mobile node within 10 ms after the mobile node initiates a handoff. Hence our scheme is suitable for roaming mobil...

We consider per-user profile replication as a mechanism for faster location lookup of mobile users in a Personal Communications Service system. We present a minimum-cost maximum-flow based algorithm to compute the set of sites at which a user profile should be replicated given known calling and user mobility patterns. We then present schemes for replication plans that gracefully adapt to changes in the calling and mobility patterns. We show the costs and benefits of our replication algorithm against previous location lookup approaches through analysis. We also simulate our algorithm against other location lookup algorithms on a realistic model of a geographical area to evaluate critical system performance measures. A notable aspect of our simulations is that we use well-validated models of user calling and mobility patterns. 1 Introduction In a Personal Communications Service (PCS) system, users place and receive calls through a wireless medium. Calls may deliver voice, data, text, fa...

In this paper we consider databases representing information about moving objects (e.g. vehicles), particularly their location. We address the problems of updating and querying such databases. Specifically, the update problem is to determine when the location of a moving object in the database (namely its database location) should be updated. We answer this question by proposing an information cost model that captures uncertainty, deviation, and communication. Then we analyze dead-reckoning policies, namely policies that update the database location whenever the distance between the actual location and the database location exceeds a given threshold, x. Dead-reckoning is the prevalent approach in military applications, and our cost model enables us to determine the threshold x. Then we consider the problem of processing range queries in the database, and we propose a probabilistic algorithm to solve the problem.

This paper presents two mobile location management algorithms for ATM (asynchronous transfer mode) networks based on the PNNI (private network-to-network interface) standard. The first solution is called the mobile PNNI scheme because it builds on the PNNI routing protocol. It uses limitedscope (characterized by a parameter S) reachability updates, forwarding pointers, and a route optimization procedure. The second solution is called the LR (location registers) scheme because it introduces location registers (such as the cellular home and visitor location registers) into the PNNI standards-based hierarchical networks. This scheme uses a hierarchical arrangement of location registers with the hierarchy limited to a certain level S. Analytical models are set up to compare the average move, search, and total costs per move of these two schemes for different values of the CMR (call-to-mobility ratio), and to provide guidelines for selecting parameters of the algorithms. Results show that at low CMR's (CMR !0.025), the LR scheme performs better than the mobile PNNI scheme. We also observe that the two schemes show a contrasting behavior in terms of the value to be used for the parameter S to achieve the least average total cost. At low CMR's, the parameter S should be high for the mobile PNNI scheme, but low for the LR scheme, and vice versa for high CMR's. Index Terms---Mobility management, PNNI, wireless ATM. I.