Improving idle handoff in CDMA mobile systems

In this letter, we have developed an efficient idle handoff technique, starting from field-test results obtained with the method used in present CDMA mobile phones, where the handoff is performed when a new pilot rises over the current one by a predefined constant. Unlike the conventional method, the proposed method decides the handoff based on a variable threshold, the value of which is automatically determined depending on the pilot strength received from the home base. It is shown that the proposed method reduces unnecessary idle handoffs and keeps the mobile tracking the pilot received with sufficient strength     

移动大气激光通信中接收视场角的研究与分析

在移动大气激光通信中，通常采用信号光和信标光来完成信号的捕获、跟踪、定位以及通信。畅通的通信链路以及稳定的接收信号对通信的建立是至关重要的。如何计算信号、信标光的接收视场角的大小，是决定链路能否畅通，接收信号能否稳定的重要因素。对移动大气激光通信中接收视场角的设计进行了研究和分析，并根据大气激光通信传输方程和黑体辐射理论提出了一种计算移动大气激光通信中信号信标光发射接收视场大小的方法，为实现激光通信系统提供了参数的定量计算方法。     

Location Error Spatial Distribution in Urban Wireless Cellular Networks

In this work the spatial distribution of the location error in wireless cellular networks operating in an urban outdoor environment is studied. We assume signal strength based positioning methods that avoid additional network hardware costs and handset modifications, while approaching FCC requirements for emergency positioning. In order to cope with the computational burden associated with the required spatial discrimination of our analysis, we developed an efficient simulator that is capable of analyzing a comprehensive class of cost efficient location algorithms based on the received signal strength measurements made periodically by the mobile terminals in GSM and UMTS systems. The simulation results show that the key factors to achieve positioning accuracy are line-of-sight and homogeneous distribution of base stations in the vicinity of the mobile terminals, leading to the conclusion that the positioning error is location dependent. This conclusion motivates a reliability analysis based on the spatial segmentation of the location process. In the same scenario we estimate the a posteriori location probabilities providing a framework for the further development of reliable methodologies for the tracking of mobile terminals.     

Estimation of mobile speed and average received power in wirelesssystems using best basis methods

A new method is presented for estimating the mobile speed and the average received power in general wireless propagation environments. The locally stationary received signal is expanded in a local exponential basis using best basis methods of wavelet analysis. An estimate of the time-varying Doppler power spectrum is obtained together with an estimate of the maximum Doppler frequency, which is proportional to the mobile speed. The average received power is then estimated by integrating the time-varying spectrum. Simulations demonstrate good tracking of variable mobile speed and average received power for a wide range of angular distributions of incident power. The estimator is shown to perform significantly better than an adaptive averaging method described in the literature. The speed and average power estimates are also used to detect the corner effect in urban cellular systems to improve handoff performance and reduce the call dropping rate     

面向毫米波波束跟踪的扩展卡尔曼滤波算法研究

针对移动毫米波通信场景中收发波束存在角度偏差时接收信号质量急剧下降的问题,提出一种联合 迭代优化均方误差和扩展卡尔曼滤波(Extended Kalman Filtering,EKF)的稳健波束跟踪算法。该算法首先采用EKF算法对信道增益和波束角度进行跟踪,然后基于最小均方误差准则(Minimum Mean Square Error,MMSE)对误差进行 平滑处理,以消除EKF 线性近似引入的误差,实现对波束发射角和到达角的动态跟踪。仿真结果表明所提出的算法能够明显降低移动环境中的波束跟踪误差,并具有稳健的波束跟踪能力。     

Effect of employing directional antennas on mobile OFDM system with time-varying channel

In this letter, we analyze the inter-carrier-interference (ICI) caused by Doppler spreading in an orthogonal frequency-division multiplexing system when the angle-of-arrival (AOA) of the received signal is not uniformly distributed. An expression of the ICI power is derived by taking into account the probability density function of the AOA. We also present examples using directional antennas at the base station, at the mobile or at both mobile and base station. The ICI power changes marginally when a directional antenna is placed at the base station. Finally, we show that the ICI power can be reduced substantially when a directional antenna, along with frequency tracking, is employed at the mobile.     

Robust Struck tracker via color Haar-like feature and selective updating

Recently, Struck—a tracker based on structured support vector machine, received great attention as a consequence of its superior performance on many challenging scenes. In this work, we present an improved Struck tracker by using color Haar-like features and effective selective updating. First, we integrate color information into Haar-like features in a simple way, which models the spatial and color information simultaneously without increasing the computational complexity. Second, we make selective model updates according to the tracking status of the object. This prevents inferior patterns resulted by occlusions, abrupt appearance or illumination changes from being added to object model, which decreases the risk of model drift problem. The experimental results indicate that the proposed tracking algorithm outperforms the original Struck by a remarkable margin in precision and accuracy, and it is competitive with other state-of-the-art trackers on a tracking benchmark of 50 challenging sequences.     

A Tracking-Assisted Routing Scheme for Wireless Sensor Networks

Wireless sensor networks (WSNs) offer much promise for target tracking and environmental monitoring. While many WSN routing protocols have been proposed to date, most of these focus on the mobility of observers and assume that targets are fixed. However, in reality, many applications require for sensing data to be propagated from multiple mobile targets to multiple mobile observers. In addition, WSNs often operate under strict energy constraints, and therefore reducing energy dissipation is also an important issue. In this paper, we present a grid-based routing scheme known as TRENS. First, we address the issue of the WSN comprising multiple mobile targets and observers—with TRENS being the first scheme of its kind to use tracking technology to increase the efficiency of routing procedures in the context of dynamic topology. Next, we introduce a shortcutting approach to resolve energy issues by optimizing routing paths and thus decreasing communication costs and latency. Finally, we conduct extensive simulations to show how TRENS conserves energy and performs better than other grid-based schemes.     

Simulation and analysis of Awerbuch–Peleg and GSM schemes for location tracking of mobile users

Mobile users are increasingly demanding full access to networked communications while they are on the move. Several studies have shown that the overhead incurred by the network to keep track of the current location of mobile users is considerably high. The methods currently used for location tracking incur heavy unnecessary costs by requiring that users update locations in their home networks after each move regardless of the distance at which the move occurs, and that all search attempts for a mobile user are first routed to that user's home network. The Awerbuch–Peleg scheme presents a formal model for location tracking which attempts to minimize the cost of local operations—both move and find operations—through the construction of a regional hierarchy. In this paper we present a performance evaluation of the Awerbuch–Peleg scheme. We also compare its performance to that of the GSM‐based location tracking scheme. It is found that the Awerbuch–Peleg scheme in general results in higher costs than the GSM scheme. The reason for this is found to be some unexpected properties of the read and write sets which are key components of the Awerbuch–Peleg scheme. Copyright © 2001 John Wiley & Sons, Ltd.     

Cumulant-based adaptive multichannel filtering for wirelesscommunication systems with multipath RF propagation using antenna arrays

A method based on high-order statistics is proposed to mitigate the performance degradation caused by multipath RF propagation in a mobile radio communication system using a linear antenna array at the base-station receiver. It is shown that an overdetermined system of linear equations (involving only cumulants of the received baseband digitized signal) can be obtained to perform noniterative deconvolution. An efficient adaptive algorithm based on square-root decomposition is proposed to avoid numerical problems when real-time tracking of moving transmitters is needed     

An Adaptive Hard Handoff Algorithm for Mobile Cellular Communication Systems

In this letter, we propose an adaptive hard handoff algorithm with a dynamic hysteresis value based on the received signal strength from the serving base station, for mobile cellular communication systems. A discrete‐time method is presented to evaluate handoff algorithms analytically. Performance is evaluated in terms of the average number of handoffs, the probability of link degradation, and the average handoff delay. Numerical results and simulations demonstrate that the proposed algorithm outperforms the handoff algorithm with fixed hysteresis values and the handoff algorithm using both threshold and hysteresis.     

Fast adaptive super-exponential multistage beamforming for cellularbase-station transceivers with antenna arrays

A new blind adaptive beamforming algorithm is introduced. We show how cumulants of the received signals can be used to obtain the weights of the beamformer that perform blind extraction. The method is based on a spatial interpretation of a deconvolution procedure known as the super-exponential algorithm. The basic block processing algorithm is attractive because it can be transformed in an efficient adaptive algorithm which exhibits good tracking capability. To prove the effectiveness of the idea, we show results for a typical mobile communications scenario where several cochannel interferers corrupt the signals of interest     

一种基于接收信号强度的自行车跟踪算法

为了实现对赛车手进行实时定位以保障其安全,提出基于接收信号强度指示(Received signal strength Index,RSSI)测距的场地自行车的跟踪算法(Track Cycling Tracking based on received signal strength Index Ranging, TCTR)。TCTR算法的目的就是估计移动节点(自行车)和锚节点(教练)间的距离。依据对数正态衰落模型(Log-normal shadowing model, LNSM)和锚节点所接收的RSSI值,TCTR算法测量自行车和教练间的距离。为了提高测距精度,建立室内、室外的场地自行车实验,获取RSSI值和距离数据,再通过拟合,最终估计LNSM参数。仿真结果表明,通过优化LNSM参数,降低了测距的均方根误差。     

车辆监控系统中车载GPS GSM双定位终端的设计

随着我国交通运输业的发展,车辆的跟踪监控在物流等行业显得越来越重要。车辆监控系统中,车载定位终端多采用GPS技术进行定位,而GPS定位虽然定位精度高但存在盲点较多的缺陷。而基于GSM网络的位置服务恰恰能弥补GPS定位盲点较多的缺点,从而可以有效地克服GPS定位盲点多的缺点,故该定位终端集成了GPS和GSM网络两种定位方法的优点。实验结果表明,该定位终端可达到准确、实时、全天候、无盲点定位,大大提高了定位性能。     

Intelligent Dynamic Radio Tracking in Indoor Wireless Local Area Networks

Indoor positioning is an enabling technology for delivery of location-based services in mobile computing environments. This paper proposes a positioning solution using received signal strength in indoor Wireless Local Area Networks. In this application, an explicit measurement equation and the corresponding noise statistics are unknown because of the complexity of the indoor propagation channel. To address these challenges, we introduce a new state-space Bayesian filter: the Nonparametric Information (NI) filter. This filter effectively tracks motion in situations where the Kalman filter and its variants are inapplicable, while maintaining a computational complexity comparable to that of the Kalman filter. To deal with the noisy nature of the indoor propagation environment, the NI filter is used in the design of an intelligent dynamic WLAN tracking system. The system anticipates future position values and adapts its sensing and estimation parameters accordingly. Our experimental results conducted on measurements from a real office environment indicate that the combination of the intelligent design and the NI filter results in significant improvements over the Kalman and particle filters.     

SIP Paging and Tracking of Wireless LAN Hosts for VoIP

This paper introduces a new paging technique to track and wake up a mobile node (MN) attached to an access point (AP) in a wireless LAN network after a session initiation protocol (SIP) INVITE message is initiated by a caller. A tracking agent (TA) keeps track of the mobiles' handoffs between the APs. A paging agent (PA) triggers the TA to page the mobile when a SIP INVITE is received for one of its users. The context transfer feature of our paging protocol allows the paging messages to deliver the station context in order to enable faster session reestablishment. The AP then does onlink paging in a wireless link. SIP extensions are needed to trigger the PA to start paging MNs to notify their dormant status using an extended SIP REGISTER method. Tracking protocol is analyzed to compare soft- and hard-state approaches for state inconsistency ratio, message rate, and the overall cost. The simulation model we developed enables us to evaluate the traffic introduced by the tracking protocol and the cache (state) size. Paging protocol is analyzed for CPU processing times and the transmission delays in the SIP session setup with paging. Simulation of the paging with context transfer is used to show the gains in reauthentication.     

An integrated system based on wireless sensor networks for patient monitoring,localization and tracking

This works describes the system LAURA which provides patient localization, tracking and monitoring services within nursing institutes through a wireless sensor network. The system is composed of three functional blocks: a localization and tracking engine which performs localization out of samples of the received signal strength and tracking through a particle filter; a personal monitoring module based on bi-axial accelerometers which classifies the movements of the patients eventually detecting hazardous situations, and a wireless communication infrastructure to deliver the information remotely. The paper comments on the design and dimensioning of the building blocks. Two approaches are proposed to the implementation of the localization and tracking engine: a centralized implementation where localization is executed centrally out of information collected locally, and a distributed solution where the localization is performed at the mobile nodes and the outcome is delivered to the central controller. Strengths and weaknesses of the two solutions are highlighted from a system’s perspective in terms of localization accuracy, energy efficiency and traffic loads. LAURA modules are finally tested in a real environment using commercial hardware. The main outcomes are an average localization error lower than 2 m in 80% of the cases and a movements classification accuracy as high as 90%.     

Research on dynamic handover decision algorithm based on fuzzy logic control in mobile FSO networks

Because of multiple advantages such as high bandwidth, high security, and flexible networking, the free space optical communication (FSO) has attracted more and more attention. However, the narrow beam of laser and the constrained access degree of optical node limit the development of mobile FSO networks, especially in the aspect of handover. In this paper, we propose a fuzzy logic control-based handover decision (FLC-HD) algorithm to ensure real-time and reliable communication. First, according to the predictive position and the motion information of mobile nodes obtained by the error correction extend Kalman filter algorithm, we obtain the received signal strength and the relative motion angles at next transmission. Second, we put forward the concept of threshold to ensure the completion of handover operations before the current link breaking. Third, the fuzzy logic control method is designed to select the optimal access point (AP) with three critical parameters, i.e., the received signal strength, the relative motion angles, and the access degrees of nodes. Simulation results show that the FLC-HD algorithm can improve the handover efficiency and relieve the ping-pong effect in mobile FSO networks.

     

基于红外辐射信息的IRST系统机动目标跟踪算法

传统的IRST(红外搜索与跟踪)系统是一个仅有角测量的系统,对于目标距离是不可观测的。文中增加了红外探测器对目标红外辐射的响应信息这一测量项,使其成为一个距离可观测系统,并在此基础上,建立了目标的观测模型,推导出了机动目标跟踪的EKF跟踪算法。通过跟踪一个机动目标的仿真过程,对算法性能进行了检验,结果表明：本算法对机动目标能进行有效的跟踪,而且跟踪精度也是令人满意的。     

Real-time mobility tracking algorithms for cellular networks based on Kalman filtering

We propose two algorithms for real-time tracking of the location and dynamic motion of a mobile station in a cellular network using the pilot signal strengths from neighboring base stations. The underlying mobility model is based on a dynamic linear system driven by a discrete command process that determines the mobile station's acceleration. The command process is modeled as a semi-Markov process over a finite set of acceleration levels. The first algorithm consists of an averaging filter for processing pilot signal, strength measurements and two Kalman filters, one to estimate the discrete command process and the other to estimate the mobility state. The second algorithm employs a single Kalman filter without prefiltering and is able to track a mobile station even when a limited set of pilot signal measurements is available. Both of the proposed tracking algorithms can be used to predict future mobility behavior, which can be, useful in resource allocation applications. Our numerical results show that the proposed tracking algorithms perform accurately over a wide range of mobility parameter values.