Dynamic model-based filtering for mobile terminal location estimation

Mobile terminal location is an important area of research because of its applications in location-sensitive browsing and resource allocation. The paper presents a method for reducing the error in mobile terminal location estimation. A preprocessor using nonparametric estimation is used to reduce the effects of non-line-of-sight and multipath propagation on the location procedure. A model-based dynamic filter is presented that uses an accurate model of mobile terminal motion to combine information from location measurements made at different time instances to create an improved location estimate. The model of mobile terminal motion has a kinematic state space model describing the physical rules governing terminal motion and a control model that describes the human control input into the motion process. Location dependency in the control input model is used to derive a new dynamic filter. This filter provides greatly improved accuracy over previously known location techniques and is much more robust to variations in the mobile terminal motion and nonlinear effects in the propagation environment.     

模拟空中目标定位运动模型的几点设想

空中目标定位运动模型主要为雷达模拟设备与系统提供及时、准确、逼真的空中目标信息。空中目标定位运动模型是任何雷达模拟系统都必须建立的基本模型,其结构与系统的处理速度、精度有极大的相关性。建立雷达训练想定时,为了使目标在预定时间到达预定地点（如拦截、合批、分批等操作）,需要确定精确的4D飞行航迹,必须给定确定的航路点,模拟目标的实际位置。     

A collaborative location model for cellular mobile position location

In cellular network, several Time Difference Of Arrival (TDOA) location algorithms can be applied to mobile position estimation. However, each algorithm has its own limitations and none of them is proved to be the most reliable one in different channel environments. In this paper Kleine-Ostmann‘s data fusion model is modified and a collaborative location model which incorporates position estimate of two TDOA location algorithms is proposed.Analysis and simulation show that more reliable and accurate mobile position estimation can be achieved based on this model.     

Realistic mobility simulation of urban mesh networks

It is a truism that today’s simulations of mobile wireless networks are not realistic. In realistic simulations of urban networks, the mobility of vehicles and pedestrians is greatly influenced by the environment (e.g., the location of buildings) as well as by interaction with other nodes. For example, on a congested street or sidewalk, nodes cannot travel at their desired speed. Furthermore, the location of streets, sidewalks, hallways, etc. restricts the position of nodes, and traffic lights impact the flow of nodes. And finally, people do not wander the simulated region at random, rather, their mobility depends on whether the person is at work, at lunch, etc. In this paper, realistic simulation of mobility for urban wireless networks is addressed. In contrast to most other mobility modeling efforts, most of the aspects of the presented mobility model and model parameters are derived from surveys from urban planning and traffic engineering research. The mobility model discussed here is part of the UDel Models, a suite of tools for realistic simulation of urban wireless networks. The UDel Models simulation tools are available online.     

一种新的蜂窝网NLOS误差抑制算法

非视距传播(NLOS)误差是目前基于蜂窝网络的移动台定位系统提高定位精度必须解决的关键问题,该文提出一种基于概率密度估计和偏差Kalman滤波器的NLOS误差无偏估计算法。仿真结果表明,该算法在性能上优于现有同类算法,并且算法对环境先验知识的需求更少,具有更广泛的适用性。     

Repeatable and Realistic Experimentation in Mobile Wireless Networks

Experimenting with mobile and wireless networks is challenging because testbeds lack repeatability and existing simulation models are unrealistic for real-world settings. We present practical models for the physical and MAC layer behavior in mobile wireless networks in order to address this challenge. Our models use measurements of a real network rather than abstract radio propagation and mobility models as the basis for accuracy in complex environments. We develop an adaptive measurement technique in order to maximize the accuracy of our models in dynamic environments. The models then predict the packet delivery, deferring, and collision probability in the same network for an arbitrary set of transmitters. This allows to explore the performance of different network and higher layer protocols in simulation or emulation under identical and realistic conditions. We evaluate the accuracy of our models empirically by comparing them to benchmark measurements. We find that our models are effective at reproducing mobile scenarios in various environments. Across many experiments in realistic environments, we are able to reproduce link delivery probabilities with RMS error below 12 percent, and the simulated throughput of data flows in the presence of interfering transmitters with an error that is below 10 percent.     

关于功率放大器中功率检测在负载失配下的研究

在复杂的应用环境中,手机等移动终端设备在负载高驻波比的条件下,其相位的变化会严重影响功率检测的精度。通过对功率检测模型进行理论分析,并利用仿真软件ADS进行仿真和分析,验证影响功率检测精度的关键因素,为在实际系统设计中实现最优化的功率检测精度提供理论指导和实现方案。     

Analysis and heuristics for the characterization of selective repeat ARQ delay statistics over wireless channels

We consider a point-to-point wireless transmission where link layer ARQ is used to counteract channel impairments. In particular, we refer, as an example, to a 3G cellular system, where a dedicated channel is used between a mobile terminal and its serving base station. Our aim is to find accurate and fast heuristics for the characterization of link layer and higher level (e.g., application level) packet delay. Existing methods to obtain such statistics are often based on recursive computations or large-sized matrix manipulations. For these reasons, they are too complex to be successfully applied in a mobile terminal due to memory, delay, and energy constraints. We first present an analytical framework to compute link-layer packet delivery delay statistics as a function of the packet error rate; then we extend the model in order to find the statistics related to higher level packets (i.e., to aggregates of link layer packets). Both in-order and out-of-order delivery of link-layer packets to higher levels are considered. The goodness of the channel model considered in the analysis is proved by means of accurate channel simulation results. The obtained statistics are then characterized by highlighting their properties as a function of the round-trip time and the error rate at the link layer. Finally, fast and accurate heuristics are derived directly from the analysis. These heuristics are very simple (piecewise linear functions), so they can be effectively used in a mobile terminal to obtain accurate delay statistics estimates with little computational effort.     

Estimating position of mobile terminals from path loss measurements with survey data

Estimating the position of mobile terminals is an important problem for cellular networks. A low cost method of locating the mobile terminal is to use measurements of the radio path loss. The distribution of radio path loss is, unfortunately, a non‐linear function of the mobile terminal location. The non‐linearity results from large obstacles to radio‐wave propagation such as buildings or hills. This paper demonstrates how the conditional density of the location given measured path loss can be approximated as a sum of kernel density functions based on radio propagation data collected from propagation surveys or estimated from computer models. Using these approximate density functions an accurate location estimate of a mobile terminal can be estimated from measured path loss values contaminated by measurement noise. Copyright © 2002 John Wiley & Sons, Ltd.     

Movement-based location update and selective paging for PCSnetworks

This paper introduces a mobility tracking mechanism that combines a movement-based location update policy with a selective paging scheme. Movement-based location update is selected for its simplicity. It does not require each mobile terminal to store information about the arrangement and the distance relationship of all cells. In fact, each mobile terminal only keeps a counter of the number of cells visited. A location update is performed when this counter exceeds a predefined threshold value. This scheme allows the dynamic selection of the movement threshold on a per-user basis. This is desirable as different users may have very different mobility patterns. Selective paging reduces the cost for locating a mobile terminal in the expense of an increase in the paging delay. We propose a selective paging scheme which significantly decreases the location tracking cost under a small increase in the allowable paging delay. We introduce an analytical model for the proposed location tracking mechanism which captures the mobility and the incoming call arrival patterns of each mobile terminal. Analytical results are provided to demonstrate the cost-effectiveness of the proposed scheme under various parameters     

一种基于GPRS网络的缓存一致性策略

提出了在GPRS网络中加入一个验证服务器VS维护无线移动环境下的缓存一致性的策略,利用GPRS骨干网中SGSN的有关移动终端的位置信息和用户访问的局域性,有针对性地只向在线终端发送所缓存数据的失效信息,有效地降低异步传输中的信息量。性能分析表明,该策略简化了维护缓存一致性的复杂性,使用很少的移动终端计算量,支持任意断开连接时间和一个PLMN网内的漫游。     

A statistical modeling approach to location estimation

Some location estimation methods, such as the GPS satellite navigation system, require nonstandard features either in the mobile terminal or the network. Solutions based on generic technologies not intended for location estimation purposes, such as the cell-ID method in GSM/GPRS cellular networks, are usually problematic due to their inadequate location estimation accuracy. In order to enable accurate location estimation when only inaccurate measurements are available, we present an approach to location estimation that is different from the prevailing geometric one. We call our approach the statistical modeling approach. As an example application of the proposed statistical modeling framework, we present a location estimation method based on a statistical signal power model. We also present encouraging empirical results from simulated experiments supported by real-world field tests.     

Database Correlation Method with Error Correction for Emergency Location

The constantly growing number of mobile terminal users increases also the number of mobile originated emergency calls. In the United States mobile terminal location in case of an emergency call was mandated with stringent accuracy requirements by Federal Communications Commission (FCC) in 1996. Since July 2003 emergency call location is required also in the European Union (EU), but contrary to the US, without accuracy limits. The global positioning system (GPS) offers high location accuracy, but the density of GPS-capable terminals is very low. Thus, to be able to provide location estimations for all mobile originated emergency calls nationwide, techniques based on cellular network are preferred. In many cases, however, conventional techniques cannot provide sufficient accuracy. This is typical especially for urban areas, where obstacles in signal propagation path degrade location estimation. In urban areas the mobile terminal user density is high and a substantial part of urban emergency calls are mobile originated requiring accurate location estimation. In this paper, we propose a method for emergency call location in urban areas. This database correlation method (DCM) is complemented by error correction method (ECM) developed in the frame of the EU IST project cellular network optimization based on mobile location (CELLO) [http://www.telecom.ntua.gr/cello/]. In performance evaluations DCM has proven to offer sufficient urban accuracy of 44 m in GSM field trial and 25 m in UMTS simulations. The ECM has been tested and proven to ease the implementation of DCM.     

考虑运动补偿的机载SAR定位误差传递模型及航迹标定方法

机载合成孔径雷达(SAR)定位误差不仅受载机位置/速度测量误差、系统时间误差等的影响,还与运动补偿残余误差有关.然而现有机载SAR定位模型很少考虑运动补偿误差的影响.该文针对实际中普遍存在的含运动误差和载机航迹测量误差的情况,结合运动补偿和频域成像算法,推导了机载SAR图像定位误差传递模型,阐明了运动补偿残余误差影响下...     

On the generation of correlated Rayleigh fading envelopes for accurate simulation of diversity channels

The generation of correlated Rayleigh fading envelopes based on mobile radio channel characteristics for realistic simulation of diversity systems was documented in 1974 by Jakes. In this letter, a survey of recent algorithms which draw upon Jakes' work will be given, as well as an illustration of their shortcomings. Subsequently, a procedure is presented for the generation of multiple equal-power correlated Rayleigh fading envelopes, with desired cross-correlations and autocorrelation functions specified so as to model channel conditions under the general assumption of isotropic scattering. The algorithm presented will enable accurate simulation and investigation of the effect of correlated fading on diversity schemes.     

Doppler Shift and Capacity Analysis of MIMO Antenna Arrays in a Novel 3D Geometric Channel Model

One of the fundamental research areas in wireless communications is the development of realistic models that can efficiently and accurately describe the wireless propagation channel. In multi-path environments, the received signal frequency constantly varies as a result of the relative motion between the receiver and transmitter. In this paper, we bridged a novel 3D geometric channel model and the multiple-input and multiple-output (MIMO) antenna array, analyzed deeply the probability density functions (PDFs) of the Doppler shift (DS), its variance, and characteristic function and etc. For the particular channel model, analytical expressions for PDFs of the channel model and the DS of mobile station (MS) due to its motion, have been derived. Based on the analysis, we investigated MIMO receiving performance. Also developed a geometric channel model, and was firstly in the asymmetric geometry literature due to a directional antenna array employed at base station. For this channel model, it was assumed that each multi-path component of the propagating signal undergoes one bounce. It was also assumed that the scattering objects around MS, could be expressed as Gaussian and exponential density models, which are more suitable to simulate outdoor and indoor environments.

     

A Hierarchical Signal-Space Partitioning Technique for Indoor Positioning with WLAN to Support Location-Awareness in Mobile Map Services

The precise and accurate performance of location estimation is a vital component of context-aware applications. Numerous mobile devices with built-in IEEE 802.11 Wi-Fi technology can be used to estimate a user’s location through a wireless local area network (WLAN) in indoor environments in which fixed access points are deployed. This study deals with improving the common techniques of such positioning once the acquisition of the fingerprint database in offline phase is performed. The main idea is to propose a methodology that includes two layers of classification: a concurrent hierarchical partitioning of both signal and physical space in a way that signal patterns in each part of building have the highest similarity, and a precise and independent positioning in a given part. A procedure for combining the proposed classifier with either artificial neural network (ANN) or Bayesian probabilistic model is then introduced. We also consider an alternative strategy for ANN learning by including all raw observations. The average distance error was successfully reduced in the proposed methodology by 32 % compared to the simple approach. We concluded that the physical partitioning should also consider the signal behavior. Toosi location-aware mobile system was ultimately implemented, providing different services (e.g., friend finder and nearest point of interest) based on the proposed technique via WLAN. The system benefits from the high level of interaction provided by Asynchronous JavaScript and XML (AJAX) technology. It is capable of transferring locational data and GIS map services efficiently to the mobile terminal.     

Ad hoc routing protocol's performance: a realistic simulation based study

Multiple wireless devices jointly create and maintain ad hoc networks; their employment is favored to happen in a variety of environments with distinct topological characteristics. Diversified environmental conditions are expected to vary network performance. In fact, obstacles, buildings and/or mountains may act as either barriers, or source of noise for the radio signals. Nevertheless, most of the previous performance evaluation studies based on simulation, neglected this consideration; they used simulation models that were too simplistic, and too narrow (i.e. idealistic) in their scopes. With this paper we propose a new, complete and realistic Urban Mobility Model (UMM). It models realistically users motion, and radio signals propagation in a city-like scenario. Our aim is to study the effects of realistic network simulation on routing performance. The results prove that a realistic scenario with roads and buildings has a significant impact on routing.     

移动通信网中的一种边界关联位置更新策略

本文针对移动通信蜂窝网固定位置区位置管理中存在的两个主要问题:边界乒乓效应和边界信令集中,提出了一种边界关联位置更新策略,能够在很大程度上抑制乒乓效应,同时,部分平滑了位置区边界的信令负荷.采用随机游走模型和状态转移矩阵理论推导的方法,对本文提出的更新策略与传统位置更新策略进行了分析比较,并通过仿真进一步验证了结果.分析和仿真表明,本文策略不仅相对易于实现,而且极大优化了性能.     

Performance analysis of cellular mobile communication systems fordata transmission

Buffers are used to overcome the data losses due to the interruption of data transmission when a mobile station is handed over in a cellular network. Data traffic from a wireline network to its mobile data terminal, such as access to large commercial databases or data transmission from a main computer to its remote mobile terminal, is studied. Compound Poisson (CP) is used to approximate the arrival process of the data traffic, and a modulated D (MD) distribution is used to approximate the service and handover process. The performance of the queueing model CP/MD/1/N is analyzed. Probability generating functions and characteristic functions are used to evaluate the mean queue length and the mean burst delay for an infinite buffer system and the overflow probabilities versus the buffer size for a finite buffer system. A method is presented to find the probability transition matrix entries by recursively taking derivatives of the probability generating function of the number of the characters arriving during the service-time. The queue length distributions for a finite buffer, both at departure instants and at arbitrary time instants are derived. Comparison with simulation indicates that the model is accurate. The numerical results of the model confirm the effectiveness of the scheme