Two-level pointer forwarding strategy for location management in PCS networks

For a IPCS network to effectively deliver services to its mobile users, it must have an efficient way to keep track of the mobile users. The location management fulfills this task through location registration and paging. To reduce the signaling traffic, many schemes such as a local anchor (LA) scheme, per-user caching scheme and pointer forwarding scheme have been proposed in the past. In this paper, we present a new location management scheme which intends to mitigate the signaling traffic as well as reduce the tracking delay in the PCS systems. In this strategy, we choose a set of visitor location registers (VLRs) traversed by users as the mobility agents (MA), which form another level of management in order to make some registration signaling traffic localized. The idea is as follows: instead of always updating to the home location register (HLR), which would become the bottleneck otherwise, many location updates are carried out in the mobility agents. Thus, the two-level pointer forwarding scheme is designed to reduce the signaling traffic: pointers can be set up between VLRs as the traditional pointer forwarding scheme and can also be set up between MAs. The numerical results show that this strategy can significantly reduce the network signaling traffic for users with low CMR without increasing much of the call setup delay.     

Quantitative analysis of a hybrid replication with forwarding strategy for efficient and uniform location management in mobile wireless networks

A location management scheme in wireless networks must effectively handle both user location update and search operations. Replication and forwarding are two well-known techniques to reduce user search and update costs, respectively, with replication being most effective when the call to mobility ratio (CMR) of the user is high, while forwarding is most effective when the CMR value is low. Thus, based on the user's CMR, the system can adopt a CMR threshold-based scheme such that if the user's CMR is lower than a threshold, then the system applies the forwarding scheme; otherwise, it applies the replication scheme. Applying different location management schemes based on per-user CMR values introduces undesirable high complexity in managing and maintaining location- related information stored in the system as different system support mechanisms must be applied to different users. In this paper, we quantitatively analyze a hybrid replication with forwarding scheme that can be uniformly applied to all users. The most striking feature of the hybrid scheme is that it can determine and apply the optimal number of replicas and forwarding chain length on a per-user basis to minimize the communication cost due to location management operations while still being able to use the same data structure and algorithm to execute location management operations in a uniform way for all users. We develop a stochastic Petri net model to help gather this information and show how the information obtained statically can be used efficiently by the system at runtime to determine the optimal number of replicas and forwarding chain length when given a use user's profile. We show that the proposed hybrid scheme outperforms both pure replication and forwarding schemes, as well as the CMR threshold-based scheme under all CMR values.     

Local anchor scheme for reducing signaling costs in personalcommunications 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     

Dynamic hierarchical database architecture for location managementin PCS networks

This paper introduces a dynamic hierarchical database architecture for location management in personal communications service (PCS) networks. The proposed scheme allows the dynamic adjustments of user location information distribution based on the mobility and calling patterns of the mobile terminals (MTs). A unique distribution strategy is determined for each MT, and location pointers are set up at selected remote locations which indicate the current location of the MTs. This method effectively reduces the signaling and database access overhead for location registration and call delivery. Besides, the required processing is handled by a distributed network of directory registers and centralized coordination is not necessary. The functions of the other network elements, such as the home location register (HLR) and the visitor location registers (VLRs), remain primarily unchanged. This greatly facilitates the deployment of this scheme in current PCS networks     

A batch‐update strategy for the distributed HLRs architecture in PCS networks

Owing to the increasing population of mobile subscribers, the rapidly expanding signaling traffic has become a challenge to the mobility management in PCS networks. Multiple database schemes to reduce signal traffic and to solve the bottleneck problem of the single home location register (HLR) architecture have been proposed by many researchers. However, in most of the multiple location databases or HLR systems, extra signaling is required for the multiple database updates. We propose a batch‐update strategy, instead of the immediate update method, for the location‐tracking schemes with replication to reduce the signaling overhead. In this paper, we first introduce a distributed HLRs architecture in which each HLR is associated with a localized set of VLRs and the location registrations and queries are processed locally. Then we propose our batch‐update strategy and present two pointing schemes for inter‐HLR call deliveries. The numerical result shows that our approach can effectively decrease the signaling cost of location registration and call delivery compared with the IS‐41 standard. Copyright © 2002 John Wiley & Sons, Ltd.     

3G中增强的3层动态位置管理建模与分析

基于3G网络中由HLR(home location register)、GLR(gateway location register)、VLR(visitor location register)构成的3层数据库结构,提出了基于移动的增强动态位置管理策略,重点分析了该策略下位置更新和寻呼的代价模型。并使用该代价模型对3G网络中基于移动的增强动态位置管理策略、基于移动的基本动态位置管理策略和静态位置管理策略进行了评价,计算结果显示增强动态位置管理策略要优于基于移动的基本位置管理策略和静态位置管理策略。     

Determination of the Registration Point for Location Update by Dynamic Programming in PCS

Location management is important to effectively keep track of mobile terminals with reduced signal flows and database queries. Even though dynamic location management strategies are known to show good performance, we in this paper consider the static location management strategy which is easy to implement. A system with single home location register and pointer forwarding is assumed. A mobile terminal is assumed to have memory to store the IDs of visitor location registers (VLRs) each of which has the forwarding pointer to identify its current location. To obtain the registration point which minimizes the database access and signaling cost from the current time to the time of power-off probabilistic dynamic programming formulation is presented. A Selective Pointer Forwarding scheme is proposed which is based on one-step dynamic programming. The proposed location update scheme determines the least cost temporary VLR which point forwards the latest location of the mobile. The computational results show that the proposed scheme outperforms IS-41, pure Pointer Forwarding, and One-step Pointer Forwarding at the expense of small storage and a few computations at the mobile terminals.     

Group location management for mobile subscribers on transportation systems in mobile communication networks

We propose a new location tracking scheme for subscribers on transportation systems (TSs) in which a large number of fast-moving users have the same location as the TS. The group location tracking (GLT) scheme in which a group location update is performed instead of the IS-41's individual location update has been proposed. We propose a distributed GLT (DGLT) scheme based on several virtual visitor location registers (VVLRs) and representative identities. We analyze the GLT and DGLT schemes in view of the database (DB) access cost as well as the signaling cost under one-dimensional network architecture. Compared with the IS-41 scheme, the schemes based on group management generally have a lower signaling cost and a lower DB access cost due to a significant reduction in the number of location updates. As user mobility increases or the number of users on a TS increases, the performance of the group management schemes improves. The DGLT scheme, in which a corresponding home location register selects a closest VVLR among several possible VVLRs, generally has a lower signaling cost although a DB access cost is increased slightly compared with the GLT scheme. We also obtain the regions in which the DGLT is more efficient than the IS-41 and the GLT scheme. The DGLT scheme is an appropriate solution for high signaling cost systems and the GLT scheme is useful for high DB access cost systems.     

A direction-based location update scheme with a line-pagingstrategy for PCS networks

On the problem of location update and terminal paging, many schemes using ring-paging strategies have been proposed. However, sequentially paging the rings surrounding the mobile user's last updated location may cause large paging cost. We propose a direction-based location update (DBLU) scheme using a line-paging strategy to reduce the paging cost. A moving direction identification mechanism using only simple computations detects the change of moving direction and updates the mobile's location. The numerical results show that our DBLU scheme achieves good performance when the paging cost is high     

A profile-based location strategy and its performance

Future microcellular personal communications systems (PCSs) will be characterized by high user density and high mobility. It is expected that registrations will incur a large amount of the radio link signaling traffic. A profile-based strategy (PBS) is proposed to reduce the signaling traffic on the radio link by increasing the intelligence within the fixed network. The system maintains a sequential list of the most likely places where each user is located. The list is ranked from the most to the least likely place where a user is found. When a call arrives for a mobile, it is paged sequentially in each location within the list. When a user moves between location areas in this list, no location update is required. The list may be provided by the user or may be based on each user's past calling history. The method for doing this is outside the scope of this work. This work focuses on the potential performance improvements that can result from maintaining such a list. This paper compares the performance of the proposed strategy to the typical geographic-based location-tracking schemes being implemented in evolving digital cellular and cordless standards. Key performance measures for the comparison are radio bandwidth, fixed network SS7 traffic, and call setup delay. We investigate the conditions under which the PBS performs better than the traditional scheme. Results indicate that over a wide range of parameters, it may be possible to reduce both the radio bandwidth and fixed network signaling load for a modest increase in call setup delay     

Group registration with local anchor for location tracking in mobile networks

In mobile networks, the location of a mobile user needs to be traced for successful and efficient call delivery. In existing cellular networks, as a mobile user changes his/her location area (LA), a location registration request is sent to the home location register (HLR) to update the user profile to point to the new LA. With a large number of mobile subscribers, this conventional registration strategy will incur a high volume of signaling traffic. We propose a new location registration strategy, called Group Registration (GR), which efficiently reduces the location registration cost by reporting location changes to the HLR for multiple mobile terminals (MTs) in a single location update request message. Specifically, the IDs of the MTs newly moving into an LA are buffered and sent to the HLR for location update in the route response message of the next incoming call to any MT in the LA. An analytic model is developed and numerical results are presented. It is shown that the proposed GR strategy can achieve significant cost reductions compared to the conventional strategy and the local anchor strategy over a wide range of system parameters. Moreover, the GR strategy results in a much smaller call delivery latency than the local anchor strategy.     

An Index-Based Location Management Scheme for PCS Network

Location management provides the guarantee to deliver a call to mobile user during the mobility of user and it is a key challenge in wireless cellular networks. In this paper, we are introducing a new index-based location management scheme. It is based on indexing of location update information at the home agent of network. A tuple of index will keep track of range of location update information and corresponding thread of it, connected to stack of information table. To register a new mobile user, the mobile switching centre will generate a new identification number with the help of mobile switching centre identification number and temporary mobile subscriber identity of subscriber. If, the identification number is with in the range of index then, the Care of Address of mobile subscriber is added to information table else, the index will be reconstruct based on new range of identification number. It has been observed that in proposed technique, the call setup delay and network overheads is reduces over the limitation of minor increment of registration delay. The analytical model and numerical result represents the effectiveness of proposed scheme over the existing schemes.     

Locating strategies for personal communication networks, a noveltracking strategy

The partition of location areas is designed to minimize the total costs of finding users' location and tracking their movement in personal communication networks (PCNs). A new scheme to partition and track mobile users and its implementation based on cellular architecture are proposed. According to the tracking strategy, the mobile station (MS) transmits only update messages at specific reporting cells, while the search for a mobile user is done at the vicinity of the cell to which the user has just reported. We use the cost analysis model to demonstrate the feasibility of updating and searching costs to reduce the amount of resources when using wireless channels. Simulations are performed to compare the performance of three schemes: always update, always search, and our new scheme     

A selective location update strategy for PCS users

A new location update strategy for personal communication services (PCS) networks and its implementation using a genetic algorithm are proposed. Most of the practical cellular mobile systems partition a geographical region into location areas (LAs) and users are made to update on entering a new LA. The main drawback of this scheme is that it does not consider the individual user mobility and call arrival patterns. Combining these factors with the LAbased approach, we propose an optimal update strategy which determines whether or not a user should update in each LA, and minimizes the average location management cost derived from a userspecific mobility model and call generation pattern. The location management cost optimization problem is also elegantly solved using a genetic algorithm. Detailed simulation experiments are conducted to capture the effects of mobility and callarrival patterns on the location update strategy. The conclusion from this work is that skipping location updates in certain LAs leads to the minimization of the overall location management cost for a user with a specific mobility pattern and even with moderately high call arrival rate.     

On optimum timer value of area and timer-based locationregistration scheme

In typical mobile communication systems, mobile station (MS) location information is updated when the MS crosses the location area boundary or the registration timer is expired. When a call attempt occurs, sequential paging rather than blanket paging is used to reduce the paging cost. We propose a new location update scheme in which to increase the paging accuracy, timer-based location update is performed within a location area. In this work, the optimum timer value of the area and timer-based location registration scheme with intelligent paging is derived. In case of a fixed location area, the optimum registration timer value depends on the speed and call arrival rate of the MS. If the speed or call arrival rate of the MS is high, location registration based on timer value should be performed frequently. Otherwise, location registration based on the crossing of location area is sufficient     

Implicit Deregistration with Forced Registration for PCS Mobility Management

Registration/deregistration with a mobility database called Visitor Location Registers (VLRs) is required in a PCS network when a mobile phone moves between registration areas. Several schemes were proposed to deregister a mobile phone after it moves out of a registration area. A simple scheme, called implicit deregistration, is studied in this paper, which does not specifically deregister any obsolete record in the VLR. If the VLR is full when a mobile phone arrives, a record in the VLR is deleted and the reclaimed storage is reassigned to the incoming mobile phone. It is possible that a valid record will be deleted. If so, the VLR record of a mobile phone may be deleted before a call to the mobile phone arrives. Our previous work assumed that the incoming call setup would be lost. In this paper, we propose forced registration to restore the VLR record before the call setup operation can proceed. With this modification, implicit deregistration totally eliminates the deregistration traffic at the cost of creating some forced registration traffic.We derive the record-missing probability and the portion of the network traffic saved by implicit deregistration. Our study indicates that implicit deregistration with forced registration may significantly reduce the deregistration traffic if the user mobility is high and the number of mobile phones in a registration area is not very large.     

Group location tracking based on representative identity andvirtual VLR for transportation systems

A location tracking scheme known as group location tracking (GLT) is proposed to reduce the location update cost for terrestrial transportation systems (TSs) in personal communication networks. When a TS moves into a new registration area, the GLT scheme, based on a representative identity of the TS and a virtual visitor location register, updates location information by a group location update request message instead of individual location update of users. Compared with the IS-41, the GLT scheme significantly reduces signaling load     

User mobility pattern scheme for location update and paging in wireless systems

The user mobility pattern (UMP) scheme is introduced for location update and paging in wireless systems where mobile terminals (MTs) maintain their history data in a database called user mobility history (UMH). During a location update, a UMP is derived from UMH and registered to the network. Unless the MT detects that it has moved out of the registered UMP, it does not perform any other location update. On the other hand, cells are paged selectively according to the cell entry times in the registered UMP upon a call arrival for the MT. The related data structures and the protocols for the UMP scheme are presented in the paper. The experimental results show that the UMP scheme outperforms the time-based and movement-based location update schemes as well as the blanket, selective, and velocity paging schemes.     

A profile-based strategy for managing user mobility in third-generation mobile systems

Several strategies have been proposed recently to improve the performance of the location management scheme in mobile systems, the influence of mobility on network performance must be reduced, mainly due to the huge number of mobile hosts in conjunction with the small cell size. In this article we present a profile-based strategy (PBS) to reduce location update signaling cost by increasing the intelligence of the location procedure. This strategy associates with each user a list of cells where she is likely to be at a given probability in each time interval. The implementation of this strategy has been subject to extensive evaluation. The results obtained confirm the effectiveness of PBS in significantly reducing the costs of both location updates and call delivery procedures when compared to IS-41 and other well-known strategies in the literature.     

雾计算中细粒度属性更新的外包计算访问控制方案

针对基于密文策略的属性加密(CP-ABE)在低时延需求较高的雾计算环境中,存在加解密开销大、属性更新效率低的问题,提出了一种雾计算中细粒度属性更新的外包计算访问控制方案,使用模加法一致性秘密(密钥)分享技术构建访问控制树,将加解密计算操作外包给雾节点,降低用户加解密开销;结合重加密机制,在雾节点建立组密钥二叉树对密文进行重加密,实现对用户属性的灵活更新。安全性分析表明,所提方案在决策双线性Diffie-Hellman假设下是安全的。仿真实验结果表明,所提方案中用户加解密时间开销相比其他方案更小,属性更新效率更高。