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.     

一种TDOA/AOA混合定位算法及其性能分析

在蜂窝移动通信系统中，智能天线阵列的应用使得服务基站（BS）能提供较准确的移动台（MS）电波到达角（AOA）测量值，从而可以用于对移动台的定位估计，文中对文献[1]的电波到达时间差（TDOA）定位算法进行了改进，提出了一种既能继承原算法的优良性能，又可充分利用AOA测量值信息提高定位性能的TDOA/AOA混合定位算法，该算法还具有解析表达式解。仿真结果表明，只要AOA测量值达到一定精度，该算法就能取得比文献[1]的单纯TDOA定位算法更好的性能。     

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.     

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     

一种利用激光超声技术检测裂纹位置的策略

为了检测工程机械疲劳裂纹所在位置,本文利用 激光超声技术,基于脉冲回波法(Pulse-echo)提出了一种检测裂纹所在位置的策略。结果表明:通过将探测光源放置在 近 场区域,同时将探测源与激励源相对固定,两次移动材料的这种策略,可使两次移动过程中 利用探测光位置代表裂纹左右边缘,从而能得到裂纹所在的位置及裂纹的宽度。实验证明, 本策略可用于定位裂纹误差,与传统的光源设置方法中单向移动扫描的方式相比,能够同时 得到裂纹的位置信息和宽度大小。本文为激光超声检测工程机械裂纹位置提供了一种策略。     

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 setup (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 setup cost than other approaches.     

An alternative strategy for location tracking

Mobile radio communications raise two major problems. First: a very poor radio link quality. Second: the users' mobility, which requires the management of their position, is resource consuming (especially radio bandwidth). This paper focuses on the second issue and proposes an intelligent method for users locating: the alternative strategy (AS). Our proposal is based on the observation that the mobility behavior of a majority of people can be foretold. If taken into consideration by the system, this characteristic can save signaling messages due to mobility management procedures, leading thus to savings in the system resources. Several versions of the AS are described: a basic version for long term events (i.e., received calls and registrations), and versions with increased memory for short and medium term events. The evaluation of the basic versions was performed using analytic and simulation approaches. It shows that storing the mobility related information brings great savings in system resources when the users have medium or high predictable mobility patterns. More generally speaking, this work points out the fact that the future systems will have to integrate users related information in order: firstly: to provide customized services and secondly: to save system resources. On the other hand, current trends in mobile communications show that adaptive and dynamic system capabilities require that more information to be collected and computed     

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 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 novel sectional paging strategy for location tracking in cellular networks

In this letter, we propose a new paging technique, sectional paging, that reduces the paging cost while complying with the delay constraint for mobiles roaming with traceable patterns. Without having to install much additional complexity, the developed scheme predicts the likelihood of residence and assigns optimal paging boundaries. Thus while complying with the required delay constraints, quality-of-service (QoS) measures will not need to be sacrificed as a result of increasing the update threshold. Under the same network conditions and mobile characteristics, simulation results reveal that the usage of sectional paging is most suitable when the roaming pattern is either traceable or can be predicted with reasonable precision.     

A two-phase algorithm and performance bounds for the star-starconcentrator location problem

The introduction of concentrators in a centralized telecommunication network provides a cost-effective way to connect the network. The star-star (SS) network model is considered, and the star-star concentrator location problem (SSCLP) is then examined. The SSCLP is NP-complete and can be formulated as a 0-1 integer programming problem. A two-phase algorithm is developed to solve the SSCLP. In the first phase, dualizing the side constraints produces a Lagrangian problem that is easy to solve and has an optimal value that is a lower bound (for minimization problems) on the optimal value of the original SSCLP. Heuristics then are applied to produce an upper bound (feasible solution) to the SSCLP. In the second phase, a branch-and-bound method is used to refine the solution space to obtain a tighter lower bound. First, an enumeration heuristic is applied to improve the best feasible solution obtained from the first phase. Then, a procedure for deriving bounding problems is presented and various branching strategies are discussed. Computational examples with up to 100 terminals and 30 potential concentrators are considered. All the network designs obtained are shown to be within 2% of optimal     

Chord bisection strategy for fast ellipse location

It is shown that a previously proposed rapid sampling technique can be extended using a strategy based on chord bisection. The strategy is characterised by very high speed of operation coupled with accurate location, and can be matched to the level of robustness required by the application. The new technique has been tested on images in which the ellipses are cereal grains with close to 2:1 aspect ratio. But it appears to be suitable for locating ellipses of any eccentricity with near ultimate speed of processing     

有源无源一体模式下目标定位及其精度分析

在分析两站无源交叉测向平面定位的基础上,提出一种测向、时差联合定位的模型,并分析了其定位原理和精度;推导了组网雷达的探测精度表达公式,并比较了单站、两站、三站雷达定位精度的差异.在此基础上,结合有源组网探测的优点和无源侦察只被动接收、不辐射信号的优点,提出了有源无源一体模式下的目标定位模型及其定位精度分析,并对五站定位中的两种不同情况进行了仿真和分析.仿真结果表明,有源无源一体模式下的目标定位方式能有效地对目标进行定位并有良好的定位精度.     

基于多跳蜂窝网的组位置管理策略

提出了一种成组进行位置管理的策略,分析了彼此临近的移动台组成一个自组织网的基本网络模型,提出了向中继点注册,由中继点进行信令压缩,组成组控制信令,成批向网络报告位置的位置更新的策略;采用M/M/n/n模型具体比较了批处理方案与传统方案的性能,说明作者的方案不仅减少了移动台的发射功率,还大量节省了频率资源,增加了系统的吞吐能力。     

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 thiscall to mobility ratio may not be knowna priori or may change slowly with time, we also derive an adaptive policy selection algorithm. The policy is derived from a maximum likelihood estimate of the call to mobility 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 algorithm performance is degraded by repeated policy 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 two resulted in greatly improved performance for a wide range of values of the call to mobility ratio.     

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.     

Adaptive directional‐aware location update strategy

In this paper, a new tracking strategy, the directivity‐aware location updating scheme was developed to better utilize the distinct characteristics of individual users on travelling directions. In this new adaptive scheme, an optimal distance‐based update threshold is selected according to the call‐to‐mobility ratio and a transitional directivity index, introduced to give indications of the mobile's travelling patterns. It is found that as far as mobility characteristics are concerned, the actual transitional direction of roaming mobiles plays a significant role in selecting the optimal threshold in addition to the usual perception about mobility rate. Its advantage becomes even more visible when an optimal threshold is not theoretically obtainable due to certain restrictions imposed by the network during times of high system loadings. Simulation results show that the additional information made available about roaming mobile's transitional directivity is critical to ensure that the best available sub‐optimal threshold is realizable. Other advances in this paper include the simplification of existing Markovian movement model. With the improved model presentation, the number of states necessary to simulate such memoryless movements is reduced. Consequently, the computational complexity involved is also lessened. Copyright © 2004 John Wiley & Sons, Ltd.     

A lightning location system in China: its performances and applications

This paper describes the largest lightning location system in China-Guang Dong lightning location system (GDLLS), which only locates the electromagnetic fields radiated by individual return strokes in cloud-to-ground flashes. Using information gathered from 14 combined magnetic direction and time-of-arrival finder sensors, the GDLLS provides both real-time and historical lightning data to the electric utility industry. The real-time data include the time of lightning strokes, their location and polarity and an estimate of the peak current. In this paper, the performance of the GDLLS is addressed, including detection efficiency and location accuracy. The potential applications of lightning data collected by the GDLLS are discussed also for electric power utilities in the Guang Dong province.     

An intra-LA location update strategy for reducing paging cost

The blanket paging strategy in current mobile networks may waste a lot of wireless bandwidth. While keeping the standard location area (LA) based location update (LU) strategy unchanged, we propose an intra-LA LU scheme to reduce the paging cost. While a mobile terminal (MT) is residing in an LA with a cell called anchor cell, where the MT usually stays for a significant period, an intra-LA LU is performed whenever the MT changes its location between the anchor cell and the rest of cells in the LA. For an incoming call, either the anchor cell or the rest of cells in the LA is paged to locate the MT. Thus the paging cost is greatly reduced, especially when the called MT is located in its anchor cell.     

一种无电解电容隔离型Cuk逆变器及其功率解耦策略

基于隔离型Cuk变换器具有电气隔离、结构简单、输入电流连续等优点,提出一种新型隔离型Cuk逆变器及其功率解耦策略。首先给出Cuk逆变器的拓扑结构及控制策略,详细分析了工作原理,该结构不需要中间母线电解电容,减小了变换器的体积,可提高功率密度与可靠性。针对输入直流侧存在二次电流纹波,进一步提出在逆变器输入端并接一个有源功率解耦单元以消除二倍频脉动电流,详细分析解耦单元工作原理、特性、关键参数设计及控制。搭建500 W的实验仿真电路,仿真结果证明了所提逆变器及其控制策略的可行性。