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...

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.

In current distributed systems, the notion of mobility is emerging in many forms and applications.

This paper describes current and proposed protocols for mobility management for public land mobile network (PLMN)-based networks, mobile Internet protocol (IP), wireless asynchronous transfer mode (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 personal communication systems (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 addressed by the next generation of wireless network service is discussed

Mobile Computing is a new emerging computing paradigm of the future. Data Management in this paradigm poses many challenging problems to the database community. In this paper we identify these new challenges and plan to investigate their technical significance. New research problems include management of location dependent data, wireless data broadcasting, disconnection management and energy efficient data access. 1 Introduction The rapidly expanding technology of cellular communications, wireless LAN, wireless data networks, and satellite services will give mobile users capability of accessing information anywhere and anytime. In the near future, tens of millions of users will carry a portable (palmtop, laptop) computer (often called personal digital assistant (PDA) or personal communicator) with wireless connection to a worldwide information network. Coming years will most likely be the decade of mobile or nomadic computing. This vision poses new challenging problems to the databas...

this paper, we look at the problems associated with delivering multicast messages to mobile hosts. First, we identify how a mobile host's ability to connect to different MSSs at different times, affects delivery of multicast messages and present schemes to deliver multicast messages to MHs from atleast-one location, from atmost-one location, and from exactly-one location. Next, we introduce "multicast groups" of mobile hosts wherein each multicast group is associated with a "host view", a set of MSSs representing the aggregate location information of the group. A host-view membership algorithm is then presented and combined with the multicast scheme for exactly-once delivery. As a result, to deliver a multicast message to a specified group, copies of the message need be propagated only to the MSSs in the group's host-view. 1 Introduction

Mobile computing is a new emerging computing paradigm posing many challenging data management problems. We identify these new challenges and investigate their technical significance. New research problems include management of location dependent data, frequent disconnections, structuring distributed algorithms for mobile hosts, wireless data broadcasting, and energy efficient data access. 1 Introduction The rapidly expanding technology of cellular communications, wireless LAN, and satellite services will make it possible for mobile users to access information anywhere and at anytime. In the near future, tens of millions of users will carry a portable computer often called a personal digital assistant or a personal communicator. Various possibilities are shown in Figure 1. Smaller units will run on AA batteries and may be diskless; larger units will run on Ni-Cd packs. These will be powerful laptop computers with large memories and powerful processors. Regardless of size, all mobile co...

Handovers for multi-media Wireless LANs (WLANs) have special requirements, unlike those in the public wireless networks. In this paper, the problems and challenges faced in a multi-media WLAN environment are presented and a multi-tier wireless cell clustering architecture is introduced. New design issues for multi-media handovers are specified and a fast, continuous and efficient hybrid handover protocol is proposed. A prototype of the proposed handover protocol is implemented into a Cambridge Fairisle ATM switch and the results are evaluated. We found that implementing transport mobility for a Wireless ATM environment is not practical as the cell re-routing function is not scalable to increasing cell rate and to the number of mobile connections. It also changes the characteristics of the traffic. Instead, the data link layer mobility implementation is found to work well. The protocol provides symmetric data disruption to traffic flows in both directions and up to seventy five intra-cluster handovers can be supported in a second. Throughout the experiment, cells arrive in sequence with no cell loss observed during the handover, up to the capacity limit of the ATM switch.

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. 1 Introduction In a Personal Communications Service (PCS) system, users place and receive calls through a wireless medium. Calls may deliver voice, data, text, facsimile, or video information [JLLM94]. PCS users are located in system-defined cells, which are bounded geographical areas. When a user places a call, the PCS infrastructure must route the call to the base-station located in the same cell as the callee. The base-station then transmits the data in the call to the PCS unit through the wireless medium. We consider the problem of locating users who...

this paper, we have used the terms mobile and portable computing interchangeably. However, strictly speaking, we view portable computing as a more restrictive form of mobile computing: though a portable computer may connect to the network from different locations, it essentially connects to the network at any given access point through an individual wired connection and therefore, cannot simultaneously move and maintain its connection to the network. The notion of a "cell" and the associated wireless communication with a broadcast capability, is absent from portable computing.