A distributed location management strategy for next- generation IP-based wireless networks

1 Introduction Mobility management is a key technical aspect in mobile communication systems. The main purpose of mobility management is to enable mobile terminals or users to communicate with each other continuously while moving—— while minimizing data…     

A speed-adaptive strategy for location management cost reduction in cellular networks

A speed adaptive location management scheme will greatly reduce the cost of tracking mobile stations, because mobile stations can travel at a wide range of speeds. Recently, an elegant distance- and time-based scheme has been proposed. The scheme uses a look-up table which describes the relationship between the distance and the time: the distance decreases while the time increases. In the scheme, the paging area for a mobile station will be automatically reduced if the mobile station does not update its location over a certain time period. Therefore, the scheme performs well when a mobile station travels at a low speed. However, it does not perform well when the incoming call arrival rate is high or when the speed of a mobile station is high. To overcome those drawbacks, a novel speed-adaptive scheme is proposed in this paper. The proposed scheme uses an enhanced look-up table that consists of two parts: the distance in the first part increases while the time increases; in the second part, the distance decreases with the increasing time. By introducing the first part, the proposed scheme reduces the paging cost for a call arriving shortly after a location update, and adapts to the speed range of a mobile station. To reduce the paging cost further, a paging angle is introduced for high-speed mobile stations. Numerical simulations using various activity-based models and random walk models show that the proposed scheme performs well for mobile stations traveling at both high and low speeds. Zhijun Wang is a Ph.D. candidate in the Department of Computer Science at the University of Alabama. He received his M.S. in computer science from the University of Alabama in 2002. He also had a formal training in physics and obtained his B.S. in physics from Tianjin University in 1993 and his M.S. in physics from Yale University in 1998. His current research interests include location management in cellular networks and routing in ad hoc networks. Jingyuan Zhang received the bachelor’s degree from Shandong University in 1984, the master’s degree from Zhejiang University in 1987, and the doctoral degree from Old Dominion University in 1992, all in computer science. He is currently an assistant professor with the Department of Computer Science at the University of Alabama. Prior to joining the University of Alabama, he was an instructor with Ningbo University, an assistant professor with Elizabeth City State University, and a principal computer scientist with ECI Systems and Engineering. Dr. Zhang’s current research interests include wireless networks and mobile computing, single display groupware, graphics, and parallel processing. He is a member of the IEEE.     

A distributed control strategy for wireless ATM networks

Cellular networks are expected to be upgraded to offer Personal Communication Services (PCS). The mobility management and wireless call control approach used in cellular networks are currently being proposed for use in PCS networks. Recent work indicates that both the signaling load and database update rates caused by these mobility management and call control procedures will increase significantly in next generation PCS networks. In this paper, we propose and analyze a new cluster-based architecture and define algorithms to effectively handle mobility management and call control functions for PCS. We assume an ATM network infrastructure. Some of the key aspects of our proposal include simplifying the mobile location and tracking function, performing connection setup in segments, eliminating the need for user service profile downloads between networks, and more efficient routing of connections by removing the need for an anchor switch. Advantages of this approach include a reduction in signaling traffic load, improved call/connection setup delays, and more efficient routing of connections. We carry out an analysis of our solution for high-tier PCS applications.     

A new distributed location management algorithm for broadbandpersonal communication networks

We propose an efficient location management algorithm for broadband personal communication networks (PCNs) which reduces the complexity of network signaling and delay due to database access when locating a portable station (PS). Previous works on updating and search algorithms for personal communications have concentrated on the access delay due to signaling network traffic only. But, with the advances in fiber optic technology, it will be possible to provide the capacity of signaling network on the order of several Mbps in broadband PCNs. Thus it may be more important to simplify the signaling procedure and reduce the number of database accesses for mobility management at the cost of some increase of signaling traffic. In the proposed algorithm, we first remove all visitor location registers (VLRs) in order to achieve the simplicity of signaling procedure. Thus, only home databases for mobility management are distributed in a global network, and each database keeps only the current locations of PSs initially registered in its management area. It can solve the problem of requiring an impractically large database in a centralized database structure by distributing home location registers (HLRs) while maintaining the simplicity of mobility management and reducing database loads. This algorithm has a simple signaling procedure, and reduces database operations when compared to hierarchical algorithms as network switching hierarchy increases or relocation and calling rate increase     

An integrated strategy for reducing location management cost

In this letter, an integrated location information management strategy is proposed for mobile networks, where local anchor and replica are deployed to efficiently manage the location information of a mobile terminal (MT) based on its call and mobility characteristics. As an MT's user is roaming within the local signal transfer point (LSTP) region serving the user's home or workplace, the MT's location change is reported to a local anchor (LA)-the visitor location register (VLR) associated with the user's home or workplace. Meanwhile, the LA's location is replicated at several switches (called the replicas) originating relatively high call rates to the MT. As a result, the MT's home location register (HLR) needs to be accessed only when the MT changes its LSTP region or an incoming call for the MT is generated by a nonreplica originating switch. This is shown to reduce location tracking costs.     

Hierarchical distributed management clustering protocol for wireless sensor networks

In recent years, there has been a marked increase in the use of wireless sensor networks in various environments such as crisis areas, military operations, and monitoring systems. These networks do not use a fixed network infrastructure and therefore they are a popular choice for highly dynamic environments. One of the main concerns in these networks is the topology management issue, which the clustering method is a subfield for that. The main objective of clustering methods is optimizing the energy consumption. This paper proposes a new clustering protocol, which uses many parameters such as the activity history of each node, local and general state of nodes and their resources condition to determine the best cluster heads and members of each cluster that can increase the network lifetime, fair resource consumption and network coverage.     

A distributed routing algorithm for mobile wireless networks

We present a loop-free, distributed routing protocol for mobile packet radio networks. The protocol is intended for use in networks where the rate of topological change is not so fast as to make flooding the only possible routing method, but not so slow as to make one of the existing protocols for a nearly-static topology applicable. The routing algorithm adapts asynchronously in a distributed fashion to arbitrary changes in topology in the absence of global topological knowledge. The protocol's uniqueness stems from its ability to maintain source-initiated, loop-free multipath routing only to desired destinations with minimal overhead in a randomly varying topology. The protocol's performance, measured in terms of end-to-end packet delay and throughput, is compared with that of pure flooding and an alternative algorithm which is well-suited to the high-rate topological change environment envisioned here. For each protocol, emphasis is placed on examining how these performance measures vary as a function of the rate of topological changes, network topology, and message traffic level. The results indicate the new protocol generally outperforms the alternative protocol at all rates of change for heavy traffic conditions, whereas the opposite is true for light traffic. Both protocols significantly outperform flooding for all rates of change except at ultra-high rates where all algorithms collapse. The network topology, whether dense or sparsely connected, is not seen to be a major factor in the relative performance of the algorithms.The work of A. Ephremides was supported in part by the National Science Foundation under grants D-CDR-8803012 and EEC94-02384.     

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.     

A cone-based distributed topology-control algorithm for wireless multi-hop networks

The topology of a wireless multi-hop network can be controlled by varying the transmission power at each node. In this paper, we give a detailed analysis of a cone-based distributed topology-control (CBTC) algorithm. This algorithm does not assume that nodes have GPS information available; rather it depends only on directional information. Roughly speaking, the basic idea of the algorithm is that a node u transmits with the minimum power p/sub u,/spl alpha// required to ensure that in every cone of degree /spl alpha/ around u, there is some node that u can reach with power p/sub u,/spl alpha//. We show that taking /spl alpha/=5/spl pi//6 is a necessary and sufficient condition to guarantee that network connectivity is preserved. More precisely, if there is a path from s to t when every node communicates at maximum power then, if /spl alpha//spl les/5/spl pi//6, there is still a path in the smallest symmetric graph G/sub /spl alpha// containing all edges (u,v) such that u can communicate with v using power p/sub u,/spl alpha//. On the other hand, if /spl alpha/>5/spl pi//6, connectivity is not necessarily preserved. We also propose a set of optimizations that further reduce power consumption and prove that they retain network connectivity. Dynamic reconfiguration in the presence of failures and mobility is also discussed. Simulation results are presented to demonstrate the effectiveness of the algorithm and the optimizations.     

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.     

A utility-based distributed maximum lifetime routing algorithm for wireless networks

Energy-efficient routing is a critical problem in multihop wireless networks due to the severe power constraint of wireless nodes. Despite its importance and many research efforts toward it, a distributed routing algorithm that maximizes network lifetime is still missing. To address this problem, this paper proposes a novel utility-based nonlinear optimization formulation to the maximum lifetime routing problem. Based on this formulation, a fully distributed localized routing algorithm is further presented, which is proved to converge at the optimal point, where the network lifetime is maximized. Solid theoretical analysis and simulation results are presented to validate the proposed solution.     

A generalized framework for distributed power control in wireless networks

Most power control algorithms that aim at hitting a signal-to-interference ratio (SIR) target fall within Yates' framework. However, for delay-tolerable applications, it is unnecessary to maintain the SIR at a certain level all the time. To maximize throughput, one should increase one's power when the interference level is low, and the information transmission rate is adjusted accordingly by adaptive modulation and coding techniques. This approach is called opportunistic communications. In this paper, we generalize Yates' result and establish a new framework, which is applicable to systems supporting opportunistic communications and with heterogeneous service requirements. Simulation results show that our proposed algorithm yields significant improvement in throughput when compared with the conventional target tracking approach.     

A fully distributed location registration strategy for universalpersonal communication systems

The universal personal communication system (UPCS) is a system that enables anyone to communicate instantly with anyone else anywhere in the world. One of the crucial problems of such a system is locating hundreds of millions of moving portables in an efficient manner. The location registration strategy described is able to locate active portables automatically in the system with a small overhead in a distributed fashion. The system knows the exact position of an active portable in its service areas. The connection is set up by the system directly to its destination using the direct (shortest) path. The system capacity, efficiency, and inquiry time delay have been improved greatly compared to the leading existing techniques. It is shown that in the proposed system, the maximum database size is 0.51% and the database updating cost is 6.86% of that needed by a central database system under a specified scenario     

Replication enabled distributed cache invalidation method: replication enabled distributed cache management system for wireless mobile networks

This work proposes a replication scheme that is implemented on top of a previously proposed system for MANETs that cache submitted queries in special nodes, called query directories, and uses them to locate the data (responses) that are stored in the nodes that first request them, called caching nodes. The system, which was named distributed cache invalidation method (DCIM), includes client‐based mechanisms for keeping the cached data consistent with the data source. In this work, we extend DCIM to handle cache replicas inside the MANET. For this purpose, we utilize a push‐based approach within the MANET to propagate the server updates to replicas inside the network. The result is a hybrid approach that utilizes the benefits of pull approaches for client server communication and those of push approaches inside the network between the replicas. The approach is analyzed analytically, and the appropriate number of replicas is obtained, where it was concluded that full replication of the indices of data items at the query directory and two‐partial replication of the data items themselves makes most sense. Simulation results based on ns2 demonstrate the ability of the added replication scheme to lower delays and improve hit ration at the cost of mild increases in overhead traffic. Copyright © 2013 John Wiley & Sons, Ltd.     

分布式声探测无线网络时间同步算法研究

分布式声探测无线网络是一种基于声达时间差(TDOA)进行目标定位的无线传感器网络;而基于TDOA算法的分布式定位需要节点之间严格时间同步,本文正是对节点之间严格时间同步进行了重点研究.文中系统分析了分布式声探测无线网络的应用环境、工作机制和硬件平台,在此基础上提出节点之间的采样同步和全网同步问题,并基于后同步思想和分级同步机制,设计了分布式声探测无线网络节点同步的整体解决方案.该方案已经进行了组网测试,有效解决了分布式身探测的时间同步问题.本文对相关工程实践具有一定的指导意义.     

A unified framework for distributed video rate allocation over wireless networks

When multiple video streams share a wireless network, careful rate allocation is needed to prevent congestion, as well as to balance the video qualities among the competing streams. In this paper, we present a unified optimization framework for video rate allocation over wireless networks. Our framework applies to both unicast and multicast sessions, and accommodates both scalable and non-scalable streams. The optimization objective is to minimize the total distortion of all video streams without incurring excessive network utilization. Our system model explicitly accounts for heterogeneity in wireless link capacities, traffic contention among neighboring links, as well as different video rate-distortion (RD) characteristics. The proposed distributed media-aware rate allocation scheme leverages cross-layer information exchange between the MAC and application layers to achieve fast convergence at the optimal allocation.We evaluate performance of the proposed scheme for streaming of high-definition (HD) and standard-definition (SD) video sequences over 802.11-based wireless networks, both in unicast and multicast scenarios. The scheme consistently outperforms conventional TCP-Friendly Rate Control (TFRC) in terms of overall video quality, and achieves more balanced qualities among the streams.     

TOA-based robust location algorithms for wireless cellular networks

Caused by Non-Line-Of-Sight (NLOS) propagation effect, the non-symmetric contamination of measured Time Of Arrival (TOA) data leads to high inaccuracies of the conventional TOA based mobile location techniques. Robust position estimation method based on bootstrapping M-estimation and Huber estimator are proposed to mitigate the effects of NLOS propagation on the location error. Simulation results show the improvement over traditional Least-Square (LS) algorithm on location accuracy under different channel environments.     

A cross-layer strategy for cooperative diversity in wireless sensor networks

We investigate the problem of how to minimize the energy consumption in multi-hop Wireless Sensor Network (WSN), under the constraint of end-to-end reliability Quality of Seervice (QoS) requirement. Based on the investigation, we jointly consider the routing, relay selection and power allocation algorithm, and present a novel distributed cross-layer strategy using opportunistic relaying scheme for cooperative communication. The results show that under the same QoS requirement, the proposed cross-layer strategy performs better than other cross-layer cooperative communication algorithms in energy efficiency. We also investigated the impact of several parameters on the energy efficiency of the cooperative communication in WSNs, thus can be used to provide guidelines to decide when and how to apply cooperation for a given setup.     

A framework for optimal cost media streaming in three-tier wireless networks

Heterogeneous networking is envisioned as a key solution for accommodating the traffic surge resulting from resource demanding applications such as video streaming. In this paper, the diversity in cost, coverage, and resource availability in heterogeneous systems is exploited to minimize the streaming session cost in three-tier integrated systems. A sub-optimal streaming decision engine is developed to overcome the complexity of the original problem whose solution contradicts with both the limited processing capabilities of end-user equipment and short handoff delay requirements. Our results show that the developed framework achieves significant monetary cost savings in comparison to typical greedy streaming behavior. Additionally, our solution can be easily tuned to compromise the tradeoff between monetary, signaling and quality cost components.     

Active distributed management for IP networks

We argue that a management platform for the future Internet has to be inherently distributed and programmable. This motivates us to introduce a new management architecture, named active distributed management, which exploits the active network and mobile agent paradigms and provides the properties of distributed control and programmability inside the network. We realize the ADM architecture as a management middleware composed of several layers. In order to facilitate the development of efficient and correct programs, these layers include patterns for distributed algorithms that are typical for management applications and a set of building blocks for constructing management programs. First results of an ADM prototype system are presented