Efficient paging procedures help minimize the amount of bandwidth expended in locating a mobile unit. Given a probability distribution on user location, it is shown that the optimal paging strategy which minimizes the expected number of locations polled E[L] is to query each location sequentially in order of decreasing probability. However, since sequential search over many locations may impose unacceptable polling delay, D, optimal paging subject to delay constraints is considered. It is shown that substantial reductions in E[L] can be had even after moderate constraints are imposed on acceptable D (i.e., D 3). Since all methods of mobility management eventually reduce to considering a time-varying probability distribution on user location, this work should be applicable to a wide range of problems in the area. most notably those with additive cost structures. 1 Introduction Paging and registration are necessary features of wireless communication networks because user locations va...

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

With rapid technological advances being made in the area of wireless communications it is expected that, in the near future, mobile users will be able to access a wide variety of services that will be made available over future high-speed networks. The quality of these services in the high-speed network domain can be specified in terms of several QOS parameters. In this paper we identify two new QOS parameters unique to the mobile environment -- guarantee of seamless service and ensuring graceful degradation of service in situations where user demands exceed the network's capacity to satisfy them. A network architecture and a suite of transport level services are proposed that enables these QOS parameters to be satisfied. To appear in J. Computer Communications 1 Introduction Mobile computing refers to an emerging new computing environment incorporating both wireless and wired high-speed networking technologies. In the near future, it is expected that millions of users equipped wit...

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...

this paper, we use the term mobile object to collectively refer to any component - implemented in hardware, software, or a combination thereof- that is capable of changing locations. We assume that a mobile object can be distributed or replicated across multiple locations, meaning that there may be several locations where the object resides at the same time. This can be the case, for example, with a whiteboard application shared between a number of mobile users. The existence of (worldwide) mobile objects introduces a location problem: The need for a scalable facility that maintains a binding (i.e., a mapping) between an object's permanent name and its current address(es). Such facilities are normally offered by wide-area naming systems such as the Internet's Domain Name System (DNS) [9], DEC's Global Name Service (GNS) [10], and the X.500 Directory Ser- vice [11]

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...

As users, services, databases, and computers become increasingly mobile, so fades the era of the fixed network. Modern networks are becoming mobile networks which must accommodate a broad range services with differing mobility characteristics. Consequently, there is an impetus to understand mobility and its effect on communications systems. Of particular interest are the unique stresses imposed by mobile computing and especially mobile computer programs (agents). As an aid to greater understanding, we propose a theoretical framework for the study of mobility tracking based on user/service/host location probability distributions. We show how this methodology, using stochastic ordering and information theory, can enable quantitative comparison of various mobility management schemes as well as insight into the mobility tracking problem over a wide range of mobility characteristics. This general approach should aid both applications and future research. This work supported in part b...

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.