A Fault-Tolerant Scheme for Mobility Management in PCS Networks

One of the most important and challenging issues in the design of personal communication service (PCS) systems is the management of location information. In this paper, we propose a new fault-tolerant location management scheme, which is based on the cellular quorum system. Due to quorum's salient set property, our scheme can tolerate the failures of one or more location server(s) without adding or changing the hardware of the systems in the two-tier networks. Meanwhile, with a region-based approach, our scheme stores/retrieves the MH location information in the location servers of a quorum set of the local region as much as possible to avoid long delays caused by the possible long-distance of VLR and HLR. Thus, it yields better connection establishment and update delay. Ming-Jeng Yang received the M.S. degree in computer science from the Syracuse University, New York, in 1991, and the Ph.D. degree in computer science from National Taiwan Normal University, Taiwan, in 2004. He is an associate professor in the Department of Information Technology, Takming College, Taiwan. His research interests include wireless networks, mobile computing, fault-tolerant computing, and distributed computing. He is a member of the IEEE Computer Society and the ACM. Yao-Ming Yeh received the B.S. degree in computer engineering from National Chiao-Tung University, Taiwan, in 1981, and the M.S. degree in computer science and information engineering from National Taiwan University, Taiwan, in 1983. In August 1991, he received the Ph.D. degree in the Department of Electrical and Computer Engineering, The Pennsylvania State University, Pa., U.S.A. He is a professor in the Department of Information and Computer Education, National Taiwan Normal University, Taiwan. His research interests include fault-tolerant computing, web and XML computing, and distributed computing.     

Location Management in PCS Networks by Caching Two-Level Forwarding-Pointers

One of the challenging tasks in Personal Communication Services (PCS) is to efficiently maintain the location of PCS subscribers who move from one region to another (hereafter called mobile users). When a mobile user receives a call, the network has to quickly determine its current location. The existing location management scheme suffers from high signaling traffic in locating the mobile users. Two-level forwarding pointer scheme has been proposed from per-user forwarding pointer scheme to reduce the cost of signaling traffic. In this paper, we enhance the two-level forwarding pointer scheme. When a mobile user moves from its current Registered Area (RA), which is served by Mobile Switching Center (MSC), to another RA the local switch that acts as a parent of those two MSCs maintains this movement in its memory (hereafter called cache entry). A cache entry is used to locate rapidly the mobile user instead of querying the Home Location Register (HLR) and waiting for its reply. HLR is centralized in the network and far away from the mobile users so that the signaling traffic crossing it is expensive. Sometimes the cache entry may be failed to reach the mobile user then a two-level forwarding pointers will be created from the corresponding Visitor Location Register (VLR), attached to its MSC, through a correct path to locate the mobile user. Thus, there is a saving in cost of querying the underlying HLR. The analytical results indicate that such proposal efficiently reduces the signaling traffic cost for all values of Call to Mobility Ratio (CMR), this is especially considerable when CMR ≥1, without any increase in the call setup delay. Salah M. Ramadan (samohra@yahoo.com) received the BS and MS degrees from Computers Engineering Department, Al-Azhar University, Cairo, Egypt, in 1995 and 2002, respectively. From 2002, he was a Ph.D. student in Computers Engineering Department at Al-Azhar University and is currently pursuing the Ph.D. degree, where he is a research assistant in the Wireless Networks Branch. His research interests include traffic management in ATM networks, routing protocols, mobility management in PCS networks, and mobile computing. He is currently an instructor in Cisco Academy, Egypt. Ahmed M. El-Sherbini (Sherbini@mcit.gov.eg) received the Ph.D. in Electrical and Communication Engineering, Case Western University, U.S.A. March 1983 and M.Sc. in Communication Engineering, Cairo University, Giza, Egypt, June 1980. (M. Sc. Research Studies at the Ecole Nationale Superieure des Telecommunications (ENST), Paris, France). He is the Director, National Telecommunication Institute – Ministry of Communications and Information Technology, Egypt and Professor of Electrical and Communication Engineering Dept. Faculty of Engineering, Cairo University, Egypt. M. I. Marie received his B.Sc., M.Sc. and Ph.D. in electronic and communication engineering from Cairo University on 1972, 1981, 1985, respectively. Now he is a professor of communications at Computer and System Engineering department Al-Azhar University, Cairo, Egypt. His fields of interest includes digital communication, computer networks and protocols development. M. Zaki (azhar@mailer.scu.eun.eg) is the professor of software engineering, Computer and System Engineering Department, Faculty of Engineering, Al-Azhar University at Cairo. He received his B.Sc. and M.Sc. degrees in electrical engineering from Cairo University in 1968 and 1973 respectively. He received his Ph.D. degrees in computer engineering from Warsaw Technical University, Poland in 1977. His fields of interest include artificial intelligence, soft computing, and distributed system.     

A State-based Dynamic Location Management Scheme

We consider a state-based dynamic location management scheme, in which the user is partitioned into different mobility state set, and his location area size is changed dynamically corresponding to the state set that he belongs to. Comparing with the fixed LA scheme, numerical experiment result shows its performance can be improved by 30% whilethe current location and paging procedure can still be applied. Besides, as this scheme does not need to process complicated user information, the requirement of computing power can be decreased significantly in compare with the user-based schemes. Our scheme can be used in current 2G mobile systems (such as GSM, CDMA) and the Third Generation (3G) mobile systems with slightly modification of the equipment software.     

A Distributed and Adaptive Location Management Scheme for Hierarchical Mobility Management

1IntroductionThe IETF Mobile IPstandards[1~2]were proposedtosolve the general problemof host mobility in the inter-net.However,whenthe number of Mobile Node(MN)grows rapidly and the MNare far away fromhome andwith micro mobility,this basic mechanism will …     

An Adaptive User Preferences Elicitation Scheme for Location Recommendation

User preferences elicitation is a key issue of location recommendation.This paper proposes an adaptive user preferences elicitation scheme based on Collaborative filtering (CF) algorithm for location recommendation.In this scheme,user preferences are divided into user static preferences and user dynamic preferences.The former is estimated based on location category information and historical ratings.Meanwhile,the latter is evaluated based on geographical information and two-dimensional cloud model.The advantage of this method is that it not only considers the diversity of user preferences,but also can alleviate the data sparsity problem.In order to predict user preferences of new locations more precisely,the scheme integrates the similarity of user static preferences,user dynamic preferences and social ties into CF algorithm.Furthermore,the scheme is paraltelized on the Hadoop platform for significant improvement in efficiency.Experimental results on Yelp dataset demonstrate the performance gains of the scheme.     

非线性网络管理方案的设计

本文分析了非线性网络系统与传统编辑系统的不同，提出了非线性网络管理方面的一些技术方案，详尽论述了在网管工作中，为提高网络的稳定性与安全性所采取的一些具体措施。     

一种基于状态的动态位置管理方法

在蜂窝移动通信系统中,用户位置管理方法性能的好坏直接影响系统的服务质量.本文提出了一种基于运动状态的动态位置管理方法.系统根据用户不同的运动状态动态地决定其位置区的大小.其性能较传统方法有显著提高,接近基于个体移动特征的方法;同时,它保持了传统算法实现简单的特点,不增加任何系统负担,不改变现有的信令流程,较好地兼顾了性能与工程实用性两方面的要求,适合3G系统的应用要求,具有很好的工程应用前景.     

一种改进的支持无线IP网络的资源预留协议

移动IP技术能够支持基于IP的无线网络,资源预留协议(RSVP)用来保证多媒体传输的服务质量。然而把现有的RSVP应用于移动IP网络就会存在许多问题。提出了一种改进的RSVP支持方案(ERSVP)来实现无线IP网络的服务质量保证。ERSVP在分层网络中结合了MRSVP和RSVP隧道技术。根据性能分析,ERSVP方案能够获得比MRSVP较少的信令延迟、信令负载和资源耗费。     

一种Ad—hoc密钥维护优化方案

Ad-hoc网络节点之间的无线连接越多，网络通信跳数相对越少，但网络需要的密钥量越大，加重了密钥维护的负担，因此在通信跳数可接受的情况下应该尽量减少密钥量。定义了网络付出的代价，用来描述通信跳数和密钥量。以网络付出的代价最小为原则，设计了一种简单的密钥维护优化方案。将方案应用于一个Ad-hoc场景，推算结果表明该方案对密钥维护的优化是有效的。     

An Enhanced Hierarchical Key Management Scheme for MANETs

Security is one of the major issues in Mobile Ad-hoc Networks (MANETs). Their natural characteristics make them vulnerable to numerous severe attacks. In this paper, we present an enhanced hierarchical key management scheme for secure group communications in MANETs. The proposed approach primarily aims at improving security and complexity, especially complexity in the level of ordinary members for joining or leaving processes to achieve the most possible dynamic characteristic of MANETs without neglecting network security. The proposal scheme is designed with the potential of developing an efficient model interested in keying applied on hierarchical structure to increase the security and make no need to apply rekeying of all group members in different sub-levels as made by hierarchical key management scheme (HKMS). Also, it reduces complexity of processing load, memory usage and improves resources. In the proposed model, each communication between two nodes have a unique key to make it more secure with encrypting messages by different keys for more than one time and support node flexibility. Experiments are carried out on the proposed scheme to show the effect of complexity on each node in different grades and results are compared with traditional HKMS.     

An Anchor Chain Scheme for IP Mobility Management

This work presents a simple mobility scheme for IP-based networks, termed the anchor chain scheme. The scheme combines pointer forwarding and caching methods. Every mobile host (MH) is associated with a chain of anchors that connects it to its home agent. Each anchor defines the location of the MH at a certain degree of accuracy. The accuracy is increased along the chain until the attachment point of the MH is reached. We develop distributed procedures for updating the anchor chain (binding operation) with MH movements and for delivering messages to a MH (delivery operation). In terms of worst case performance, the total cost of the binding operations is O(Move logMove), where Move is the total geographic distance that the MH has traveled since its activation. The total length of the MH's pointer path is linear with the distance between the MH and its home network, and the delivery cost is near optimal. In addition, the anchor chain of a MH is determined dynamically with no need for preliminary definitions of static anchors or regions. Our simulation results show that the anchor chain scheme also yields lower average overheads for both the binding and the delivery operations than other methods that are described in the literature, including the current home approach. We believe that the proposed scheme is scalable, fairly easy to implement and there fore attractive for supporting MHs.     

An efficient multicast protocol for PCS networks

In a Personal Communication Services (PCS) network, mobile hosts communicate with other mobile hosts through base stations on a wired (static) network. The mobile hosts connect to different base stations through wireless links and the base stations to which mobile hosts are connected change depending on the current location of the mobile hosts. In this environment, the problem of efficiently delivering a multicast message from one mobile host to a group of other mobile hosts becomes challenging. In this paper, we present a multicast protocol that delivers multicast messages from a mobile host to a group of other mobile hosts without flooding the wired network. The multicast protocol is built on top of a user location strategy that should follow one of the three models of user location described in the paper. The basic multicast protocol proposed guarantees exactlyonce message delivery to all mobile hosts in the multicast group and also ensures that multicast messages are delivered in FIFO order from the point of view of the base station that originates the multicast message (referred to as BSFIFO). More importantly, an extension of the basic protocol is provided that, unlike earlier work, delivers multicast messages in FIFO order from the point of view of the mobile host that initiates the multicast message (referred to as MHFIFO). The modifications to be made to the multicast protocol to accommodate each of the three models of user location is also described.     

Location update cost of distance-based scheme for PCS networks with CTRW model

This letter concerns the optimization of the dynamic location-update area (LA) for the per-user distance-based scheme in personal communication service (PCS) networks. We have two main contributions: (1) under the general and popular one-dimensional (1-D) continuous-time random walk (CTRW) mobility model, we propose a novel framework to analyze the location update cost; (2) with this framework, we investigate the impact of call arrivals and the initial position of the mobile terminal (MT) on the position of the LA, which was neglected by previous work. Simulation shows that our theoretical model is very accurate.     

一种改进的CATV网传输方案

本文分析现有CATV网中的IP传输技术应用现状，提出一种以简单数据链接（SDL）协议在CATV网中的传输方案。通过在SDH网上的试验，可知该方案在变长高速数据传输中的性能比传统协议方案更为优越，可用于CATV网的数据业务传输。     

Secured Key Management Scheme for Multicast Network Using Graphical Password

Mobile Networks and Applications - In recent days, management of keys in a group has become a significant part of data communication. The textual and alphanumerical passwords used for security...     

Cooperative Location Management for a Cellular Network with Ad Hoc Communication

The cellular network with ad hoc communication has been foreseen in the next-generation mobile communication system. For such a network, a distance-based (DB) location management scheme cooperated with the ad hoc assistance node (DBCAN) is proposed in this paper. Allowing a mobile terminal to pass its mobility information to the ad hoc assistance node (AAN) with appropriate location updating, DBCAN can effectively reduce the paging cost and limit the paging delay. Moreover, DBCAN includes a method to determine whether AANs should be utilized or not to make cost effective. Our simulation results show that DBCAN can effectively reach cost reduction and still get performance improvement even if the probability to successfully deliver mobility information to AANs falls to the median level.     

User Mobility Management in the PCS Network Through the Placement of Hierarchical Databases

The personal communication service (PCS) networkis the next generation wireless communication networkthat allows users to communicate with each other oraccess information in the network any time and anywhere. It is the integration of the cellulartelephone network, the conventional telephone network,and the digital communication network. User movementswithin the network coverage area must be tracked using a database. A hierarchical distributeddatabase architecture localizes database operationscaused by user movements and call setup requests, andreduces traffic in the signaling network. Placement of the database in the signaling networkaffects performance of the network. A new method ispresented to find the best database placement scheme fora given estimation of user movement and call setuprequest rates. This database placement scheme minimizesthe delays of messages resulting from user movements andcall setup requests in the signaling network.     

Analysis and Comparison of Location Strategies for Reducing Registration Cost in PCS Networks

In mobile environments, a personal communication service (PCS) network must keep track of the location of each mobile user in order to correctly deliver calls. A basic scheme used in the standard IS-41 and GSM protocols is to always update the location of a mobile user whenever the mobile user moves to a new location. The problem with this approach is that the cost of location update operations is very high especially when the mobile user moves frequently. In recent years, various location management strategies for reducing the location update cost have been proposed. However, the performance issue of these proposed algorithms remains to be investigated. In this paper, we develop two Markov chains to analyze and compare the performance of two promising location update strategies, i.e., the two location algorithm (TLA) and the forwarding and resetting algorithm (FRA). By utilizing the Markov chain, we are able to quickly answer what-if questions regarding the performance of PCS networks under various workload conditions and also identify conditions under which one strategy can perform better than the others. Using the cost due to location update and search operations between two successive calls to a mobile user as a performance measure, we show that when the mobile user exhibits a high degree of locality and the mobile user's call-to-mobility ratio (CMR) is low, TLA can significantly outperform both FRA and IS-41. On the other hand, when CMR is high, FRA is the winner. Furthermore, unlike TLA which may perform worse than IS-41 at high CMR values, FRA at identified optimal conditions can always perform at least as good as IS-41, suggesting that FRA over TLA should be used as a generic scheme in reducing the location cost in the PCS network to cover all possible per-user CMR values.     

一种高效的延迟容忍移动传感器网络异步探测机制

针对延迟容忍移动传感器网络(Delay Tolerant Mobility Sensor Network, DTMSN)节点间连接探测开销大、错失率高的问题,该文提出一种高效的DTMSN异步探测机制(Efficient Asynchronous Probing Scheme, EAPS)。该机制面向随机路点(Random Way-Point, RWP)移动模型,在采用互质周期对的时隙睡眠机制基础上,通过对节点运动区域的合理划分和周期对的优化选择,保证了网络连接探测的高成功率和低能耗的特性。仿真结果表明,与现有的异步探测机制相比,该机制能够在低能耗下实现更高的探测成功率与更低的探测延迟。