The Need for Time Synchronization
17th May 2019
Global Navigation Satellite systems (GNSS) play a key role as a timing source for synchronising both wired and wireless telecommunication networks in a variety of sectors like Energy, Telecom, Finance, Enterprise, and even Defence. The need for GNSS in these sectors will continue to grow as new GNSS constellations come up such as Galileo, BeiDou, and IRNSS (NAVIC). This Whitepaper gives a brief overview of the applications of GNSS based time and frequency synchronization in different sectors for those who are new to the idea. The main applications covered are Power Grids, Telecom Infrastructure like Base Stations, Stock Exchanges, large and small enterprise networks, and Defence Communication networks.
Download Pdf
Spoofing Detector - Accord’s Anti-Spoofing Solution for GNSS
20th March 2019 to 22nd June 2021
Spoofing is an attempt to deceive a GNSS receiver, so that it acquires and tracks fake signals. Once the receiver latches on to the fake signals, the spoofer can introduce the required amount of errors and thus gets control on the position computed by the receiver. Through Spoofing, misleading navigation information is introduced into the GNSS receiver. The spoofed signals may be modified in such a way as to cause the receiver to estimate its position to be somewhere other than where it actually is, or to be located where it is but at a different time, as determined by the attacker. Magnitude of error introduced can be few meters to thousands of kilometres. Below is an image which shows a ship being diverted from its intended path by spoofing its GNSS navigation system.
Download Pdf
Why so many GNSS satellite Constellations? Why Multi-constellation and Multi-frequency Receiver is needed?
27th March 2019
This paper discusses the benefits of having so many Global Navigation Satellite System (GNSS) constellations and the need for a multi-frequency receiver.
Download Pdf
Advanced Navigation Research Lab for Universities!!!
18th March 2019
Universities play a vital role in research and innovation. Academic researches provide high quality journal articles, technically designed conference proceedings and many more. But it can also have a high impact in the government, industry and public sector when utilized effectively. This has been proven time and again with various academic research leading to world class innovations and benefit to mankind. Once such field where universities can contribute immensely is the field of navigation. One of the major contributors in recent time is the satellite navigation namely the GNSS – Global Navigation Satellite Systems. The need of GNSS research, benefits to university, pre-requisites for navigation lab is detailed in this article.
Download Pdf
How to meet the demanding challenges involved in testing GNSS receivers?
24th December 2018
Modernization of GNSS systems have demanded the validation of receiver performance for all new upcoming signals. The traditional live antenna analysis can no longer be used to validate all kinds of signal/environment/user scenarios which has lead to the introduction of GNSS simulators. With the help of GNSS simulators, users are now able to test the receivers in lab for all kind of critical signal conditions like modelling vehicle and satellite motion, GNSS signal structure, atmospheric and other environmental effects that can affect receiver performance.Thus, simulations can provide a controlled, reliable and repeatable way to test and adequately identify any receiver design limitations. In this article, the various challenges involved in testing GNSS receivers are highlighted. Methodologies to effectively validate the receivers using simulators are provided along with Accord GNSS Simulator products.
Download PdfArchived - 2017 & Earlier
High Integrity GPS-SBAS Receiver Using Innovative Correlator and Software Approach for Avionics Applications
A GPS-SBAS Receiver is developed around a Digital Signal Processor with optimize usage of hardware and software in the system. The receiver is designed andengineered for use in avionics application after FAA TSOcertification.Important aspects of the receiver are reliable hardwareand safety features. The failure analysis of the receiver hardware for various navigation functionalities shows acceptable performance. The power-on self test andcontinuous online tests to detect hardware failure enhancethe safety and reliability of the equipment. Additional hardware to detect failure improves the test coverage of the equipment.
Download PdfGPS Receivers for Navigation and Timing Applications
GPS receivers for navigation and timing applications are being developed and used extensively in India by various governmental and private organizations/industries. M/s Accord software has done a pioneering in this direction. The present paper deals with the development carried out M/s Accord software.Accord - an ISO9000-2000 certified company- isprimarily involved in the development of hardware and software for several of Aerospace applications and realtime embedded systems.
Download PdfInterference Effects on the GPS Signal Acquisition
Intentional or unintentional interference and jamming is one of the major concerns in using the Global Positioning System (GPS) in various critical applications. In spite of the GPS frequency bands being protected by International and Federal Communication Commission (FCC) frequency assignments, there is always a chance of disruption of the GPS signal availability in critical times and applications.
Download PdfSoftware-Aided Sequential Multi-TapCorrelator for Fast Acquisition
The requirement for GPS receivers with low Time To First Fix (TTFF) is increasing with the deployment of new standards like E911. Mean Acquisition Time (MAT)determines the TTFF in GPS receivers. In this paper we analyze a scheme called Sequential Muti-Tap correlator,which reduces MAT by an order of magnitude compared to a serial search correlator, without increasing the hardware significantly.
Download PdfReceiver Sensitivity Analysis and Results
GPS technology has found widespread applications invaried walks of life. GPS receivers serving these applications require among other performance factors,maximum possible sensitivity under non-conducive environments.Both acquisition and tracking sensitivities play animportant role in determining the overall performance of aGPS Receiver. As sensitivity is a function of various elements, it is important to analyze these parameters tostudy their impact on receiver sensitivity performance.
Download PdfDevelopment and Test Results of a Cost EffectiveInverse DGPS System
An Inverse Differential GPS (IDGPS) system is developed to achieve better GPS accuracy and significant cost savings on the air radio traffic charges by not broadcasting direct RTCM messages to the vehicles. The system consists of a Reference Station and up to twohundred and fifty In-Vehicle Equipment (IVE) fitted incars. Each IVE has a low cost GPS receiver and acommunication link to send data to a Control Station,which also receives RTCM data from the ReferenceStation through a leased line. The IDGPS is implemented in the measurement domain. The accuracy of the IVEposition is calculated before and after the range correctionto evaluate the performance achievable by this system.
Download PdfGPS/GSM based Fleet Management Systemfor Sparse GSM Networks
This paper describes the architecture and features of a GPS/GSM based Fleet Management System developed by Accord Software and Systems to cater for territories evenwith sparse coverage of GSM networks. As anintroductory note the importance of Vehicle FleetManagement in India is discussed with relevant Statistics.The paper concludes with the results of field operationscarried out in India has selected NexNav for Smart Deck.
Download PdfGPS-GSM Intrigaton Application Programming Interface
With the phenomenal growth of GPS based applications, the capabilities of aGPS receiver are expected to be exploited beyond that of a stand-alone receiver.The provision for integrating user applications on GPS chipset is becoming increasingly common among the GPS receivers. Most of the GPS receivers havea dedicated CPU for the application.
Download PdfAccord's Next Generation High Performance GPS/WAAS Receiver Based on the Soft-Correlator
NAV2500TM is the next generation GPS/WAAS receiverfrom Accord.Based on the enhanced Soft-CorrelatorTM, the receiver is designed around a single high performance fixed pointgeneral purpose Digital Signal Processor (DSP) from Analog Devices and a standard Radio Frequency down converter. The receiver features increased availability ofthe GPS solution by means of improved speed of signal acquisition and reacquisition along with enhanced signaltracking sensitivity.
Download PdfNavigating into the Future- What GPS has in Store
Global Navigation Satellite (GPS) system has gradually come of age and has found itself a place as standard Navigation equipment in most aircraft. However, data from a GPS Receiver is not reliable enough for it to be used as a primary or sole source of navigation information. As a result GPS only system is allowed to be used only as a supplemental means of navigation for aircraft in the less critical situations such as en-route, terminal and nonprecision approach stages of flight. Allthat is about to change with the advent of SBAS and GBAS.
Download PdfAn Efficient Algorithm to Compute the Inverse of a Fourth Order Positive Definite Symmetric Matrix
This paper presents an efficient and simple algorithm to compute the inverse of a fourth order positive definitesymmetric matrix. In GPS related algorithms (whetheriterative or non-iterative), the computations of userposition or velocity require determination of the inverse of such 4x4 symmetric matrices .
Download PdfMitigation of Static Carrier Phase Multipath Effects Using Multiple Closely-Spaced Antennas
The effect of carrier phase multipath in static mode is investigated and a system is developed to reduce the effect using multiple closely-spaced antennas. The correlated nature of multipath, along with the known geometry among the antennas are used to estimate and mitigate carrier phase multipath. The mathematical model of the multipath effects on carrier phase measurements and the Kalman filter implemented to estimate these errors are described. The model is first tested on simulated data and lateron field data collected on a roof whereby the model adaptively estimates the parameters of the compositemultipath signal
Download PdfAttitude Determination with GPS-Aided Inertial Navigation Systems
Precise attitude parameters are required in connection with numerous marine and airborne applications, including shipborne multi-beam echo sounding systems for sea floor mapping, and airborne laser and digital camera mapping. Multi-antenna GPS can deliveraccuracies of better than several arcmins under good conditions...
Download PdfSynergy Between GPS Code, Carrier and Signal-to-Noise-Ratio Multipath Errors
GPS code, carrier and SNR measurements are corrupted by multipath signals that can significantly affect the quality of data used for static and kinematic positioning applications. Atool to simulate code, carrier and signal-to-noise ratio (SNR) multipath errors in a user-defined, multi-antenna and multi-reflector environment for multipath error analysis is developed and described .
Download PdfAnalysis of Multiple GPS Antennas for Multipath Mitigation in Vehicular Navigation
The most important issue when using GPS for urbanvehicular navigation is the position reliability which usually depends on the nature of the environment. In particular, the presence of urban canyons and foliage can cause significant degradation in satellite visibility as wellas high multipath. Although GPS information tends to beintegrated with other dead-reckoning sensors to increaseposition availability, it is often difficult to isolate satelliteswith significant multipath effects, which can then corruptthe integrated position solution .
Download PdfLOW COST INS/GPS Intrigation Concepts and Testing
The high cost of inertial units is the main obstacle for their inclusion in precision navigation systems to support a variety of application areas.Standard inertial navigationsystems (INS) use precise gyro and accelerometersensors, however, newer inertial devices with compact, lower precision sensors, have become available in recent years.
Download PdfAttitude Determination Using MultipathMitigation on Multiple Closely-Spaced Antennas
The high cost of inertial units is the main obstacle for their inclusion in precision navigation systems to support a variety of application areas.Standard inertial navigationsystems (INS) use precise gyro and accelerometersensors, however, newer inertial devices with compact, lower precision sensors, have become available in recent years.
Download PdfUrban Vehicular Multipath Detection Using Multiple Antennas and Reliability Anal
This paper introduces NAV2300, a 12 channel and single frequency C/A code GPS receiver. Latest addition to the NAV2KÔ family of solutions, the receiver core is realized around a single programmable fixed-point DigitalSignal Processor (DSP) microcomputer from Analog Devices.
Download PdfNAV2300 - Accord's High Performance Low Cost Receiver Technology
Surveying is the first and foremost step conducted before embarking on any large-scale construction or for identifying geographic boundaries. Traditionally surveying has been ....
Download PdfImplementation of a Multi-Channel Baseband CDMA Receiver on a ADSP2189M Process
The origins of Spread spectrumare in military field and navigation systems. Techniques developed to provide efficient data communication proved for CDMA mobile technology. To meet data communication requirements for commercial mobile standards like GSM, implementation of a multi-channel CDMAreceiver offering a data rate of 9600 bps ....
Download PdfThe modified wave estimator as an alternative to a Kalman filter for real-time GPS/GLONASS±INS integration
The performance of a Kalman ®lter is essen-tially limited by the description of the input noise and therefore it is diffcult to improve the estimation proce- dure within the framework of traditional estimationtheory. One way to further improve performance is to describe the system in a deterministic sense for a mean-ingful, but short duration of....
Download PdfGPS-DR IntegrationUsing Low Cost Sensors
A land navigation system integrating a low cost GPSreceiver and Dead Reckoning (DR) sensors is developed. The DR sensors consist of an odometer and a vibrational gyroscope. A Kalman filter is developed, which uses allthe available information and estimates an optimum solution for position, velocity and sensor errors....
Download PdfCharacterization of GPSCarrier Phase Multipath
GPS carrier phase measurements are affected by multipath signals that can significantly affect the quality of data used for static and kinematic positioning applications. It is generally difficult to characterize thismultipath using field data whereby the exact sources of the errors cannot be easily isolated.....
Download PdfCode Range and Carrier Phase Multipath Mitigation Using SNR, Range and Phase Measurements...
Multipath is a major source of error in high precision GPS static and kinematic differential positioning. It is a majorconcern in reference stations such as in Local Area Augmentation Systems (LAAS), whereby correctionsgenerated by a reference station which are based on multipath corrupted measurements, can significantlyinfluence the position accuracy of differential usersf ....
Download PdfUse of Multiple Antennas to Mitigate Carrier Phase Multipath in Reference Stations
GPS carrier phase multipath is a major source of error in high precision static and kinematic differential positioning. It is especially prevalent in static applicationswhereby the multipath phase change is due only to satellite dynamics and can thus cause slowly varying bias errors ....
Download PdfMitigation of Static Carrier Phase Multipath Effects Using Multiple Closely-Spaced Antennas
GPS carrier phase multipath is a major source of error in high precision static and kinematic differential positioning. It is especially prevalent in static applicationswhereby the multipath phase change is due only to satellite dynamics and can thus cause slowly varying bias errors....
Download Pdf