MEMS IMU Based Pedestrian Indoor Navigation for Smart Glass

In open air environment, Global Positioning System (GPS) receiver can determine its position with very high accuracy. Inside a building the GPS signal is degraded, the position estimation from the GPS receiver is very erroneous and of no practical use. In this paper, we present an indoor navigation system to track the position of a pedestrian by using built-in inertial measurement unit (IMU) sensors of a smart eyeglass. The device used for this project was an intelligent eye-wear “JINS MEME”. Here algorithm for step detection, heading and stride estimation are used to estimate the position based on the known locations of the walker using Pedestrian Dead Reckoning method (PDR). We have used extended Kalman filters as sensor fusion algorithm, where measurements of acceleration and orientation from IMU are used to track user’s movement, pace, and heading. The results showed that the level of accuracy was entirely acceptable. Average deviancy between the estimated and real position was less than 1.5 m for short range of walk was accomplished. There are some ideas for further development. Increasing the accuracy of the position estimation by palliation of stride length estimation error was identified as the most essential.     

WAW Location-based Service Positioning

Coordinated positioning operations require the user to be aware, not only, of his own position but also of the positions of the other elements on his team. Its deployment can be supported in WAW (??Where Are We???) location-based services, where the position of each user is made available to the rest of the group. This paper presents a method for the estimation of a user??s position based on measurements from a group of Global Positioning System (GPS) receivers. None of the GPS receiver positions, used in the estimation process, is considered to be known. The proposed approach leads to an improvement on the accuracy of the position estimates, when compared with those computed on an autonomous way, and has a direct application in the development of enhanced services in WAW location-based services. The positioning estimator takes advantage from the fact that, in this type of location-based service, GPS measurements are available from several receivers. Instead of estimating the user??s position based only on the measurements of his own GPS receiver, the proposed approach uses the measurements from all the GPS receivers in the group. The paper presents details of the positioning model and estimator used to achieve the accuracy improvements. Simulation results are presented based on real GPS satellite ephemeris, collected at the University campus.     

An advanced dual-frequency positioning algorithm for satellite navigation receivers

With the development of the Ground Positioning System (GPS) modernization and the expectable implementation of Galileo, people pay more and more attention to civil applications on multi-frequency signals. This paper proposes a new and advanced positioning algorithm for the dual-frequency satellite navigation receivers, concerning the various influences of all the ranging error sources and taking advantage of the Klobuchar single-frequency ionospheric model. The paper also presents positioning precision prov...     

Position Estimation in Single-Frequency GPS Receivers Using Kalman Filter with Pseudo-Range and Carrier Phase Measurements

Today Global Positioning System (GPS) is the most important system of positioning in the world and is used in different industries. Basic positioning methods in GPS receivers are based on pseudo-range and carrier phase measurements types whilst each of which has its own advantages and disadvantages. Pseudo-range method is not very much accurate. Carrier phase has a substantial accuracy, but its main problem is that it is an indirect measurement which only computes the displacement. Carrier phase measurement can include some whole cycles plus a fraction of carrier phase. The number of whole cycles may change through time however this change is unknown for us. Code measurements (based on pseudo-range) and carrier phase are corrupted with the same error sources, but with main differences. Basically, code tracking with low accuracy makes unambiguous pseudo-ranges. Carrier phase measurements are highly accurate, but get limited with integer ambiguity. Integer is fixed until the time that carrier tracking loop is saved. Every kind of gap in tracking, no matter how short it is, changes the amount of integer which is the biggest problem in carrier phase utilization. In this paper, the corporation of pseudo-range capability and carrier phase in single-frequency GPS receivers will be discussed which makes a substitute for the pure pseudo-range observations and provides a high level of positioning accuracy. To achieve this aim, Kalman filter will be used.     

GPS: primary tool for time transfer

The Global Positioning System (GPS) is not only a navigation system, it is also a time-transfer system. As a time-transfer system it provides stability very close to one part in ten to the fourteenth over one day (1 ns/day). After a brief introduction to timekeeping terms, this paper reviews the role of GPS in time distribution and clock synchronization. The GPS coarse acquisition (C/A)-code single-frequency single-channel (one satellite) common-view (CV) time transfer is then discussed. Special consideration is given to progress in GPS C/A-code CV time and frequency transfer through the use of “all-in-view” multichannel receivers. This technique increases the number of daily observations by a factor of ten relative to conventional single-channel receivers and results in an improvement in time and frequency transfer stability by a factor of about three. Other important improvements discussed are the use of GPS carrier phase measurements and temperature-stabilized antennas. The latter reduce the daily and seasonal delay variations of GPS time-receiving equipment. The use of GLONASS as a complementary tool to GPS time transfer is also be reported. These improvements indicate that GPS, as a time-transfer system, should provide the capability to reach a stability of one part in ten to the sixteenth over one day (10 ps/day)     

Revisiting the doppler filter of LEO satellite GNSS receivers for precise velocity estimation

The theoretical aspects of the precise velocity determination of Low Earth Orbit (LEO) satellites’on board Global Navigation Satellite Systems (GNSS) receivers are derived. It shows that the receiver’s Phase Lock Loop (PLL) is required to feature extremely small group delay within its low frequency band, which is in contrast to existing work that proposed wide band linear phase filters. Following this theory, a Finite Impulse Response (FIR) filter is proposed. To corroborate, the proposed FIR filter and an Infinite Impulse Response (IIR) filter lately proposed in literals are implemented in a LEO satellite onboard GNSS receiver. Tests are conducted using a third party commercial GPS signal generator. The results show that the GNSS receiver with the proposed FIR achieves 11 mm/s R.M.S precision, while the GNSS receiver with the IIR filter has a filter-caused velocity error that can not be ignored for space borne GNSS receivers.     

分布式无源雷达成像及其空间谱特性分析

针对随机分布辐射源、分布式接收雷达以及目标构成的三维空间构型,推导了基于单频辐射信号的一次快拍成像公式,提出了球坐标系统下的分布式无源雷达成像方法,并在空间谱域探讨了成像分辨率特性及其影响因素。以GPS辐射源为例仿真验证了文中成像方法的有效性,并根据空间谱填充效果对比,分析了收发空间构型和数目等因素对成像的影响,为探索利用GPS等分布式非合作辐射源实现无源成像提供了一条可能的途径。     

Neural Technologies for Precise Timing in Electric Power Systems with a Single-Frequency GPS Receiver

The global positioning system (GPS), with its ability to provide time synchronization with accuracy to 200 ns over the wide area, provides an ideal tool for performing time tagging in electric power systems. The observed GPS pseudo-range varies from the true range because of range measurement errors. GPS errors sources are ionospheric delays, atmospheric delays, troposphericelays, multi-path effects and dilution of precision etc., affecting the GPS signals as they travel from satellite to user on Earth. In this paper neural models has been presented are for more accurate GPS timing in electric power systems with a single-frequency GPS receiver. The proposed methods use back-propagation (BP), extended Kalman filter (EKF) and particle swarm optimization (PSO) training algorithms, which achieves the optimal training criterion. We use actual data to evaluate the performance of the proposed methods. An experimental test setup is designed and implemented for this purpose. Results using the three methods are discussed. The experimental results obtained from a coarse acquisition (C/A)-code single-frequency GPS receiver are provided to confirm the efficacy of the approaches to give high accurate timing. The GPS timing RMS error using neural network based on PSO learning algorithm reduces to less than 105 and 36 ns, before and after SA, respectively.     

基于平方根差分滤波的动中通姿态稳定方法

为了隔离载体扰动对天线指向的影响,研究了单基线GPS和微惯性传感器组合的低成本姿态估计及稳定方法。该方法以四元素和陀螺误差作为状态变量,根据陀螺角速率信息、加速度计的重力场信息和单基线GPS航向信息分别建立状态方程和量测方程,设计具有不同测量周期的平方根差分滤波分别融合惯性传感器和GPS信息,解决了加速度计与单基线GPS航向信息输出频率不一致问题;利用估计出的姿态角在角位置环路上对天线进行捷联稳定,隔离载体扰动。仿真结果表明,平方根差分滤波能有效估计出载体姿态,利用中等精度的微惯性器件可以满足动中通姿态稳定的需求。     

The accuracy of the global positioning systems

In certain cases, due to such high precision of geographical position estimation, there problems connected with the accuracy of systems for the projection of the globe convex surface to the two-dimensional surface of a chart emerge. When using DGPS, one should pay closer attention if the chart datum is compliant with GPS. Although DGPS can increase the precision of the SPS several times, the accuracy improvement of the PPS is very limited. Satellite navigation systems used for non-military purposes found their application mainly in maritime and aerial navigation; however, recently they started to invade inland applications. Expensive cars are being equipped with such systems, which transmit signals from remotely controlled transmitters hidden in vehicles in case of theft. Today, one can buy an inexpensive GPS or DGPS receiver capable of displaying position and travelled distance on a map of any selected region, in selected scale and with a variety of useful information such as location of hotels, restaurants, museums, or gas stations. Many developed countries are beginning to implement GPS receivers equipped with an interactive vehicle communication system that connects them with traffic control centres.     

Design and practical implementation of multifrequency RF front ends using direct RF sampling

The use of direct RF sampling has been explored as a means of designing multifrequency RF front ends. Such front ends will be useful to multifrequency RF applications such as global navigation satellite system receivers that use global positioning system (GPS) L1, L2, and L5 signals and Galileo signals. The design of a practical multifrequency direct RF sampling front end is dependent on having an analog-to-digital converter whose input bandwidth accommodates the highest carrier frequency and whose maximum sampling frequency is more than twice the cumulative bandwidth about the multiple carrier signals. The principle of direct RF sampling is used to alias all frequency bands of interest onto portions of the Nyquist bandwidth that do not overlap. This paper presents a new algorithm that finds the minimum sampling frequency that avoids overlap. This design approach requires a multifrequency bandpass filter for the frequency bands of interest. A prototype front end has been designed, built, and tested. It receives a GPS coarse/acquisition code at the L1 frequency and GPS antispoofing precision code at both L1 and L2. Dual-frequency signals with received carrier-to-noise ratios in excess of 52 dB-Hz have been acquired and tracked using this system.     

一种基于GPS载波跟踪环的窄带干扰性能优化

针对全球定位系统(GPS)卫星信号具有随机性及干扰工程实现成本的问题,讨论了窄带干扰性能优化问题。关于如何抵消卫星信号随机性问题,仿真分析了单频信号不同干扰位置分布与窄带线性调频(LFM)信号带宽设置对GPS接收机的干扰效果;关于如何降低干扰工程实现成本问题,采用了多个干扰代替单个干扰的方法进行实验分析。仿真结果表明,当采用最佳干扰位置或GPS信号带宽内均匀、随机分布等方法可一定程度消除卫星信号随机性带来的干扰不确定性;采用多信号代替单信号可相应地降低干扰所需总成本。     

GPS接收机伪码测距方法及误差分析

根据全球定位系统(GPS)的信号特点,介绍了GPS接收机利用L1频段C/A码进行伪码测 距的原理和方法,提出了一种简单、易行的位同步环设计 方法,并与传统设计方案进行了对比。最后,对影响伪距测量值的因素进行了讨论,给出了 误差计算的方法,分析了对测距精度的影响。     

Performance Analysis of Single-Frequency CW Signal-Based I/Q Regeneration in Five-Port Junction-Based Direct Receivers on Rayleigh Fading Channels

This paper analyzes the influence of the Rayleigh fading channel on the performance of a single-frequency continuous-wave (CW) signal-based I/Q regeneration in five-port junction-based direct receivers. This method uses a single-frequency CW signal to estimate the I/Q regeneration parameters. Simulation results show that the eye diagram, error vector magnitude, and bit error rate performances of five-port junction-based direct receivers using a single-frequency CW signal-based I/Q regeneration are almost the same as those of conventional coherent demodulators, even in fading channels.     

GPS软件接收机基带信号处理研究

GPS软件接收机相对传统硬件接收机,设计灵活,能够迅速分析、仿真、实现各类算法.本文主要针对GPS L1频率的C/A码信号,设计并实现了GPS软件接收机的基带处理部分,阐述了射频前端原理、并行码相位搜索捕获策略以及鉴频辅助跟踪环路,并推导了适应动态环境的三阶数字环路滤波器.仿真数据和实际中频数据测试表明:算法性能优越,能迅速捕获并锁定信号,获取导航数据.     

WCDMA中联合迭代信道估计与解码的研究

首先介绍了基于WCDMA系统中RAKE接收机的信道估计方法，然后将Turbo原理引入信道估计，针对WCDMA系统提出两种迭代信道的估计方法。通过使用RAKE接收机或解码之后的软信息来改善整个WCDMA系统的性能，对WCDMA系统中联合运用信道估计与解码技术进行了研究。由于联合信道估计与解码技术可以利用通信系统不同模块之间的“软信息”交换，从而有效地提高了信道估计准确程度和解码器的性能。仿真结果表明，利用解码之后的软信息来修正信道估计的方法较传统的RAKE接收机中的信道估计方法性能有较大改善，在误码率为10^-2左右时，提高大约1dB。     

Combined GPS/GLONASS LAAS flight trials

The use of GPS in aviation is now accepted, with extensive work being undertaken on the technological, precision and infrastructure requirements. Work has focused on providing a service that is able to operate continuously in all areas. GPS alone, however, is seen as being unable to satisfy the stringent requirements for some phases of flight. Of the many solutions proposed, the Russian GLONASS system has been regularly overlooked. The research described in this paper aims to present GLONASS as a realistic and proven augmentation to GPS for aircraft positioning. During October 1996 the Civil Aviation Authority (CAA) Institute of Satellite Navigation (ISN) at the University of Leeds, in conjunction with the National Air Traffic Services Ltd (NATS UK) and the Defence Evaluation and Research Agency (DERA), performed a series of landmark differential GPS/GLONASS flight tests using the DERA BAC 1–11 flying laboratory. A real-time differential system was constructed using two GPS/GLONASS receivers developed by the ISN and a C-band data link for the RTCA corrections. Integration onboard the aircraft with avionic sensors and flight management systems was achieved using the ARINC 429 protocol. Routes were designed and flown to evaluate the complete system over a variety of airborne dynamics for both en-route and approach situations. In total, over 16 h of flying time was recorded, including 30 runway approaches over nine flights. A thorough evaluation of the accuracy and integrity of the positioning system was performed. Emphasis was made in comparing the flight statistics with recognized Required Navigation Performance (RNP) figures. The paper describes in detail the project development and the results achieved. An analysis of the results, showing that aircraft positioning with GPS/GLONASS augmentation in a local area augmentation system (LAAS) scenario can achieve accuracies that are both comparable with GPS-alone solutions and can satisfy up to CAT II precision approach criteria, is presented. Results are also given for position propagation using velocities derived from GPS and GLONASS carrier phase measurements. © 1997 John Wiley & Sons, Ltd.     

GPS receiver architectures and measurements

Although originally developed for the military, the Global Positioning System (GPS) has proven invaluable for a multitude of civilian applications. Each application demands specific performance from the GPS receiver and the associated requirements often vary widely. This paper describes the architectures and functions of civilian GPS receivers and then focuses on performance considerations. The fundamental receiver measurements are described and the quality of these measurements are related to the aforementioned receiver architectures     

GPS姿态测量系统基线长度和天线布局设计

在GPS姿态测量系统工程实施和设计过程中,天线的布局和基线长度计是影响姿态测量精度和实时性的关键因素,通过分析和推导建立了基线的长度和天线的布局以及天线的数量对GPS姿态测量系统的测量精度和实时性的影响,介绍了可同时满足高精度和实时性要求的多天线GPS姿态测量系统。     

GPS接收机Z跟踪技术抗干扰性能分析

Z跟踪技术是民用GPS接收机为消除或减弱AS（Anti—Spoofing）政策影响,实施精密测距和高精度导航定位的一种有效方法。通过分析Z跟踪技术载波相位测量的基本原理,研究了GPS接收机Z跟踪技术的抗压制干扰、抗欺骗干扰性能。结果表明：采用Z跟踪技术的GPS接收机与C／A码接收机的抗压制干扰基本相同;其在信号捕获状态下的抗欺骗干扰能力取决于欺骗干扰信号与GPS信号的相关程度,而在信号跟踪状态下抗欺骗干扰能力则等同于抗伪随机噪声码干扰能力。