Location Management Scheme Research Articles

Schemes for mobility management of wireless ATM networks

The growing fields of wireless networks and asynchronous transfer mode (ATM) are merging to form wireless ATM networks. This paper addresses dynamic bandwidth allocation, connection admission procedures, routing, and location management strategies in wireless ATM. More precisely, we investigate the issue of extending the private Network to Network Interface, PNNI, and protocols to support mobility. PNNI-based hierarchical routing, hand-off, location management and routing schemes are proposed to integrate wireless capabilities into ATM networks. These schemes provide fast and efficient hand-off connection processing mechanism and a reduction in the connection disruption time during a connection hand-off session. They also provide a predictable resource requirement of the mobile system during its connection. During a connection hand-off, misrouted cells can be re-routed to their destinations. This substantially reduces the overhead due to end-to-end re-transmissions invoked at higher layers. An analytical model is developed to illustrate the hand-off algorithm. Copyright © 1999 John Wiley & Sons, Ltd.

On the design of a location and query management strategy for mobile and wireless environments

The rapid development of wireless digital communication technology led to a new computing environment known as mobile or nomadic computing. Mobile computing no longer requires users to confine to wired network premises, but rather it enables users to access information regardless of their location. Mobility of mobile users poses a new class of problems in the fields of networking, operating systems, and databases. Location management and location dependent query processing are major challenges in mobile computing. Location management addresses the issue of continuously keeping track of the location of each user. This article presents the architecture for the location and query management based on distributed databases and distributed object management standards. The architecture is implemented using the common object request broker architecture (CORBA) and mobile IP standards.

A cost effective distributed location management strategy for wireless networks

The mobility feature of mobile stations (MSs) imposes a large burden on network traffic control as a result of location management. Design issues of location management include MS registration (updating) and call set-up (paging). Previous approaches introduced several network topologies for updating and paging procedures, but most of them focused on a single problem: either updating optimization or paging optimization. In this paper, we design and integrate two mechanisms, distributed temporary location caches (TLCs) and distributed home location registers (HLRs), to reduce database access delay and to decrease network signaling traffic in both updating and paging for low power, low tier micro cellular systems. By using TLCs, our approach can improve the performance of updating and paging in comparison with previous approaches. Experimental results based on our analytic model show that our location management procedures have lower HLR access rate, lower registration cost, and lower call set-up cost than other approaches.

Location management strategies for cellular mobile networks

Location management in mobile communication systems is concerned with those network functions necessary to allow the users to be reached wherever they are in the network coverage area. The basic operations for that purpose-paging and location updating-are resource-consuming since both involve signalling over the radio link between the mobile stations and base stations. Future cellular mobile communication networks (wireless personal communication networks (PCN)) will have to support a large number of users, so a significant amount of radio signalling can be expected. This paper describes the conventional location management strategy (the one used in modern cellular systems like the Global System for Mobile communications (GSM)) and reviews, describes and comments on some alternative location management proposals for future high-density PCN environments that aim to reduce this expected high (radio) signalling load.

Database and location management schemes for mobile communications

Signaling traffic incurred in tracking mobile users and delivering enhanced services causes an additional load in the network. Efficient database and location management schemes are needed to meet the challenges from high density and mobility of users, and various service features. In this paper, the general location control and management function is treated as the combination of two parts, the global and local scope. New schemes and methods are proposed, and improvements achieved over established basic schemes are shown by using simulations.

A route optimization algorithm and its application to mobile location management in ATM networks

In this paper, we propose an algorithm for optimizing the route of a connection that becomes suboptimal due to operations such as handoffs and location-based reroutes, for mobile ATM (asynchronous transfer mode) networks based on the PNNI (private network-to-network interface) standard. This algorithm uses hierarchical route information of the connection and summarized topology and loading information of the network to determine a such that adjusting the connection from that crossover node results in an optimally routed connection. We then apply this algorithm to the mobile location management problem. Location management schemes have been proposed in which an incoming call to a mobile is routed to its home switch (based on summarized reachability data) and then rerouted to the mobile's current location. If we consider such rerouting a first phase of mobile connection setup, a second phase is required to optimize the paths of such rerouted connections. Such an approach is considered a two-phase mobile location/connection setup scheme. Alternatively, an incoming call to a mobile can be routed to its home switch based on summarized reachability data, and then cranked back to an optimal crossover node before rerouting the connection to the mobile's current location. Such a scheme is a one-phase mobile location/connection setup scheme since it directly results in an optimal path. A comparative performance analysis of the one- and two-phase connection setup schemes is presented. Measures of comparison are call setup delay and the amount of network resources allocated to a connection. The maximum call setup delay (worst case call setup delay) is lower in the two-phase scheme, but the average call setup delay is lower in the one-phase scheme. The amount of resources required for a connection in the two-phase scheme (prior to route optimization) is significantly greater than that in the one-phase scheme.

A Location Management Scheme Supporting RouteOptimization for Mobile Hosts

Using the Internet as a foundation for wireless networking, there is currently a great deal of interest in providing IP networking support for mobile hosts. As a result of IPs reliance on the entire Internet address for host identification, most proposals depend on a default route through the mobile host's home address, which makes for unnecessarily long routes. This paper introduces two concepts, “local region” and “patron service”, based on the locality features of host moving and calling patterns. It then shows how these concepts work together to realize a location management scheme for achieving optimal routing for most traffic while restricting costly location propagation. The proposed scheme was implemented using a network simulator and evaluated from routing effectiveness point of view, as compared with its location overhead.

Mobility and connection management in a wireless ATM LAN

This paper proposes algorithms for handoff, location, and connection management in a wireless asynchronous transfer mode (ATM) local-area network (LAN). Fast handoffs while maintaining cell sequence and quality-of-service (QoS) guarantees are achieved by distributing switching functionality to base stations, and using a networking scheme based on provisioned virtual trees. A new distributed location management scheme using a minimal registration procedure and broadcasts on wired links is proposed for this LAN. The detailed signaling procedures that support the algorithms for mobility and connection management are described. Finally, an implementation of these procedures and an analysis of the measured data is presented. Measurements of service times obtained from this implementation indicate that over 100 calls/s. can be handled by each node in 50-node network with a high-percentage of mobiles (75%) relative to fixed endpoints. This is comparable to current wired ATM switch call handling throughputs, in spite of the fact that these nodes perform additional handoff and location management functions. The data also indicates handoff latency times of 1.3 ms. This validates our proposal for maintaining cell sequence while performing handoffs.

Adaptive location management scheme for global personal communications

A major issue for achieving seamless universal personal communications is efficient location tracking of a multitude of mobile terminals. The approach in which each mobile registers in relatively small location areas may not be adequate for global personal communications because a very large number of mobile terminals with a broad range of terminal mobilities may generate excessive location updating traffic. As an alternative, the authors present an efficient multilayer mobility management scheme that is especially suitable for hierarchical cellular structures. The scheme accounts for past as well as present terminal mobilities and dynamically changes the hierarchical level of the location area to which a mobile terminal registers. In a system that contains both a terrestrial segment and a satellite segment, highly mobile terminals such as aircraft will tend to register at the highest level where location areas are formed by spotbeams. Low mobility terminals such as pedestrians will tend to register at the lowest level where location areas are formed by microcells or clusters of microcells. An additional feature of the scheme is that the required signalling traffic for location updating is distributed evenly to all stations at each level of the system. An analytical model is developed to determine the required location updating supervisory traffic of the proposed scheme. Example performance characteristics are presented. The proposed scheme can track large numbers of terminals with a broad range of mobility.

Analysis of a mobile-assisted adaptive location management strategy

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 cost of the routing techniques and the ratio of the source messaging to location update rates. Since this call to mobility ratio may not be known a priori or may change slowly with time,we also derive anadaptive policy selection algorithm.The policy is derivedfroma maximum likelihood estimate of the call tomobility ratio based on observations of message arrivals and location changes. The algorithm is found to work well when there is a clear advantage to either triangle or informed routing. However,when the two routing schemes are relatively close in average cost, the algorithmperformance is degraded by repeatedpolicy reversals. For this reason,algorithms which use hysteresis and/or a preset preference (preference threshold) for one routing scheme or another were explored. It was found that neither hysteresis, nor preference threshold techniques alone performed well, but rather a combination of the tworesulteding reatly improved performance for a wide range of values of the call to mobility ratio.

Static and adaptive location management in mobile wireless networks

Location management is one of the most important issues in mobile computing. Location management consists of location updates, searches and search-updates. An update occurs when a mobile host changes location. A search occurs when a host wants to communicate with a mobile host whose location is unknown to the requesting host. A search-update occurs after a successful search, when the location information corresponding to the searched host is updated at some hosts. Various strategies can be designed for search, update and search-update. Static location management uses one fixed combination of search, update and search-update strategies. Simulations were carried out to evaluate the performance of different static location management strategies for various call-mobility patterns. It was noticed that performing search-updates significantly reduced the search costs without significantly increasing the cost of updates (upon moves and searches). To obtain good performance using static location management, the system designer should a priori have a fair idea of the call-mobility pattern of the users. Having this information, the system designer can select the combination which performs best for the given call-mobility pattern. The host behavior (call frequency, mobility) is not always available to the system designer. Thus, there is a need for adaptive location management. In this paper we present a scheme for adaptive location management. The basic assumption behind adaptive location management is that the past history of the system will reflect the behavior in the future. The adaptive scheme dynamically estimates the future host behavior with the help of the past callmobility patterns. Results indicate that the adaptive scheme performs better than the static scheme for a wide range of call-mobility patterns.

On location management for personal communications networks

Personal communications services (PCS) support mobile terminals (MTs) which are free to travel within the service coverage area. In order to effectively locate an MT when a called is initiated, location management schemes are used to keep track of the locations of the MTs. The current approach to location management requires each MT to report its location to the network periodically. The location information is then stored in databases. When a call is initiated. The network determines the current location of the called MT through a database lookup and paging procedure. A currently available standard for location management is described. Research results on location management are surveyed in detail.

Local anchor scheme for reducing signaling costs in personal communications networks

A personal communications network (PCN) location tracking scheme called local anchoring is introduced which reduces the signalling 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 (VLRs) 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.