What’s New in GNSS Simulation? I remember working with a couple of “home- built” RF simulation systems myself, way back when. We experience a lot of maintenance and support issues. And, of course, if you build something and also build something to test it, its likely that incorrect assumptions will end up in both systems. Today, there are a number of excellent sources for GNSS simulation equipment and support you can buy on the open market. The spectrum of today’s providers seems to range from highly sophisticated scientific systems used for development by precision receiver manufacturers, through systems with GNSS and aiding solutions, to specialized systems for both general and specific application developers and also for production test. So this month I’d like to try to summarize (in no particular order) what some of the suppliers of GNSS simulation systems are up to, how they may be positioned in the market and, wherever possible, what we might expect to see from them in the future. GSG Series 6 GNSS simulator. Planning Open Pit Mining Operations Using Simulation Dy ALAN BAUER,. CALDER, t B.Eng., M.Se., Ph.D. SYNOPSIS TIte complexity of modem open pit load-haul-dump systems is described, and the peed. Artificial general intelligence (AGI) is the intelligence of a (hypothetical) machine that could successfully perform any intellectual task that a human being can. It is a primary goal of artificial intelligence research and. A functional check flight (FCF) is a nonrevenue flight that determines whether an aircraft is functioning according to established standards. This course, taught by Boeing test pilots, introduces operators of Boeing 737NG, 747. Spectracom is a more recent entrant to the GNSS simulation market, though the company has been providing frequency and time synchronization test equipment for about 40 years. Spectracom has integrated GPS into these products. A LADAR system employs the scanning mechanism to increase its coverage. There are a variety of scanning mechanisms and each has its own scanning pattern. Each LADAR system adopts a scanning mechanism suited to its own purpose. The Magenta Medical team has considerable experience in static and dynamic simulation for anatomy, surgery, laparoscopy and endovascular surgery. We provide a unique design of original electronic and force feedback. CPS 808 Introduction To Modeling and Simulation Lecture 1 Goals Of This Course Introduce Modeling Introduce Simulation Develop an Appreciation for the Need for Simulation Develop Facility in Simulation Model Building “Learn. Spectracom is a more recent entrant to the GNSS simulation market, though the company has been providing frequency and time synchronization test equipment for about 4. Spectracom has integrated GPS into these products for more than ten years, and decided three years ago to use the knowledge it had gained to get into the GNSS simulation business. The GSG family of simulators is positioned at the “affordable” end of the simulation equipment scale, and is targeted at users and integrators of GNSS, rather than developers of receivers. Spectracom claims to have about 8. Series 6) systems sell in the $2. NMEA 0183 is a proprietary protocol issued by the National Marine Electronics Association for use in boat navigation and control systems. Because early GPS sensors were designed for compatibility with these systems, GPS.While new to the business, the Spectracom team feels that this allows them to bring the newest technology and innovation to the market. The Spectracom system is derived from its well- known frequency/time synthesizer equipment — in fact, it has the same look front panel and chassis — and also makes use of the same “easy- to- use” concepts. The accompanying Studio View software is reportedly relatively easy to use to generate trajectories and other test scenarios by connecting to Google Maps and uploading them to the simulator. But with all new firmware and FPGA implementation, 6. General Purpose Simulation System (GPSS) (originally Gordon's Programmable Simulation System after creator Geoffrey Gordon; the name was changed when it was decided to release it as a product) is a discrete time simulation. GPS and GLONASS, the GSG family appears to be very well positioned for application developers integrating GNSS. Galileo and Beidou/Compass are in the works and expected this year, and will be supplied as upgrades to existing equipment. Spectracom anticipates significant growth in its target market for application developers in “anything that moves,” including automotive and airborne, video matching, radar/lidar, and handheld nav devices, including mobile phones. Spectracom has a number of product lines and around 1. GNSS simulation group is around 1. Rohde & Schwarz is another relatively recent GNSS simulation entrant with new products for the market. SMBV1. 00. A vector signal generator. Its current offering — the SMBV1. A Vector Signal Generator – can simulate 2. GPS, GLONASS and Galileo satellites. Real- time test scenarios can be customized by the user — including a neat facility that allows modeling of satellite masking by downtown buildings, along with anticipated multipath for the same urban scenario. While somewhat new to GNSS simulation, R& S has been around since the 1. GNSS simulation offerings. R& S anticipates significant growth in automotive, aerospace, UAV, and cellular assisted- GNSS application markets. R& S has had success in the aerospace market for UAVs, and has developed the capability to model antenna patterns and UAV body mask as the vehicle rotates and attitude changes towards visible satellites. Along the same lines, R& S has hooked up its system to flight simulators and provided hardware- in- the- loop testing for clients. R& S also has the ability to run simulation scenarios for long periods of time, and for “very long” periods if the receiver is stationary — this feature makes use of large internal memory storage within the SMBV1. A; of course, almanac validity limits just how long this is possible. P- code capability is provided as an option, and there is a roadmap for adding SBAS and Beidou capability later. IFEN Nav. X- NCS Professional. In the meantime, IFEN in Germany is focusing on its Nav. X- NCS Navigation Constellation Simulator range of multi- GNSS signal simulators. IFEN emphasizes the flexibility of its design, with a platform scalable from a 1. GPS L1 system up to a full multi- GNSS system with 1. GPS, GLONASS, Galileo, QZSS and SBAS. With this building- block approach, channels and capabilities can be added as and when additional testing complexity is required. IFEN claims that the capability to generate all GNSS signals — by combining different modulations with up to nine L- band frequencies — is the only existing solution on the market providing GPS, Galileo, GLONASS, QZSS and SBAS in one chassis at the same time. And, since April 2. IFEN Nav. X- NCS GNSS RF signal simulators are to include Bei. Dou B1 signal capability in accordance with the official Chinese Bei. Dou B1 ICD, and are ready for the other B2 and B3 Bei. Dou signals. IFEN also founded a subsidiary in the USA in January this year called IFEN, Inc., located in California and operational with Mark Wilson (formerly with Spirent) as VP Sales. In addition, IFEN has formed a partnership with WORK Microwave — a leading European manufacturer of advanced satellite communications and navigation equipment. WORK Microwave is responsible for RF and digital hardware design while IFEN develops the associated software and manages the distribution of the product range. Little- known IP- Solutions in Tokyo, Japan, has been working to develop its Re. Gen GNSS DIF signal simulator, a software simulator that simulates ionospheric effects, generates digital IF (DIF) signals similar to those recorded by an RF recorder, and comes with an optional capability of simulating integrated inertial navigation. IP- Solutions’ digital IF baseband signal simulator Re. Gen has been developed in close cooperation with the Japan Aerospace Exploration Agency (JAXA) to test and validate GNSS signal processing algorithms and methods for use on board aircraft using tight and ultra- tight integration with INS, including specific scintillation models and ionospheric bubble simulation. Actual recorded flight data (left), Re. Gen replicated flight data (right). Various configurations of Re. Gen can produce multichannel GPS and GLONASS L1 signals and single- channel GPS L1, L2, L5 and GLONASS L1 and L2 signals, as well as simulating noise and interference. Meanwhile, Spirent, arguably the original market leader in GNSS simulation, has continued along its chosen path of supplying the industry with the greatest capability and most extensive simulation systems. Spirent has recently released test systems with support for China’s Bei. Dou Navigation Satellite System in addition to GPS, GLONASS and Galileo. Spirent started shipping Bei. Dou- ready systems to its customers in 2. Now these may be upgraded to full Bei. Dou capability using the information available in the first full issue of the Bei. Dou- 2 Signal In Space Interface Control Document (ICD). Also aiming at mobile applications, Spirent’s Hybrid Location Technology Solution (HLTS) integrates Wi- Fi, Assisted Global Navigation Satellite System (A- GNSS), Micro Electro- Mechanical Systems (MEMS) sensor and cellular positioning technologies. HLTS integrates four very different and distinct location technologies and provides repeatable and reliable lab- based characterization of mobile devices supporting hybrid location technologies that will enable “accurate everywhere” location — including indoor user location determination. Other notable players in the GNSS simulation business include Racelogic, CAST Navigation and Agilent who are each pursuing their chosen niches in this expanding market segment. Racelogic’s Lab. Sat GPS simulator is gaining popularity with a number of leading companies, providing the ability to record and replay real GNSS RF data as well as user- generated scenarios. CAST has an extensive line- up of GPS and GPS/INS simulation systems and support software, and Agilent has added to its impressive electronic testing portfolio with a very capable looking GPS simulation product line. Several other companies — some based in China and Russia — are also trying to figure out their development and marketing strategies to conquer their chosen GNSS simulation market niche. This is all a very healthy sign that there are many other companies with new embedded GNSS applications that they are bringing to market and who therefore need GNSS simulation/test capability. Overall, this means there is still significant growth underway and far wider applications of GNSS on their way to market. Great news for the GNSS industry! Tony Murfin. GNSS Aerospace. GPS Interference Testing . How were those tests—many using signal generators and constellation simulator—carried out and how should we interpret the results? This article will tell you. Even low- level signals have the potential to interfere with GNSS receivers, which require very high sensitivity for acceptable performance due to the extremely low received GPS signal power at the Earth’s surface. In January 2. 01. U. S. Federal Communications Commission (FCC) granted satellite broadband provider Light. Squared Subsidiary LLC a waiver to operate a terrestrial- only Long Term Evolution (LTE) network that would use L- band spectrum adjacent to the L1 frequencies occupied by GNSS. The commission set a June 1. Light. Squared to submit a final report on the issue. The TWG would appoint dedicated expert teams to conduct a comprehensive test campaign to investigate the potential for interference with all categories of GPS receivers. This was especially challenging because, with the exception of the cellular industry, few standardized industry approaches to GPS receiver performance testing exist, especially with regard to interference. It is not intended to express an opinion on the part of the authors about the impact of Light. Squared signals, nor on whether Light. Squared should be allowed to deploy. It does, however, present a selection of the results from the TWG report, which was released on June 3. These can emanate from telecommunication and electronic systems that may be operating in adjacent bands or in bands relatively far from GPS bands such as FM/TV transmitter harmonics, AM transmitters, and mobile phone networks. Figure 1 illustrates the neighboring signals to GPS L1 and highlights the new potential interference source from Light. Squared. The downlink and uplink frequency ranges are 1. MHz to 1. 55. 9 MHz and 1. MHz to 1. 66. 0. 5 MHz, respectively, and the band can accommodate both 5- and 1. RF channel bandwidths. Current GPS receivers have not been designed with such a “noisy neighbor” to consider. Light. Squared signals coming from terrestrial towers arrive at the receiver with a power level of up to - 1. Bm while the mean GPS levels can be as low as - 1. Bm. These extreme differences in power levels at the receiver imply very stringent filtering requirements at the Light. Squared base stations. The resulting undesired signals may be translated to the intermediate frequency (IF) stages as spurious response frequencies. Receiver front- end filtering can improve the blocking characteristics by reducing the level of the blocking signal (See Figure 2.) However, they may limit the effectiveness of certain receivers that have wide- band filters to take advantage of satellite- based GPS augmentation systems or to improve crisp code- chip edge detection. This can be the case for the Light. Squared F5. L+F5. H deployment scenario. In the case of the TWG campaign, lab testing was used to reveal exactly how performance is affected as a function of LTE power, frequency and bandwidth. Other signals may also be present in the live environment that are not necessarily represented in the lab- testing environment. In contrast, lab testing strives to tightly control the environment to eliminate anything that could influence the repeatability of a test. Thus a complete evaluation of interference effects requires both lab and live testing to be conducted. These standards were chosen because they are widely used and accepted in the industry, not because they focus specifically on GPS interference. In practice, device manufacturers strive for, and many operators demand, better performance than that dictated in these specifications. As a result, new methodologies were defined and the metrics for, and definitions of, harmful interference were more challenging to identify. A common component of all sub- team lab tests was the introduction of the potential Light. Squared LTE signal interferer, which was combined with GPS signals before presentation to the unit under test (UUT). These could form a useful reference point for any future attempts to harmonize interference test requirements across the industry. RF signals are presented to the UUT in a conducted or OTA manner. Conducted testing uses coaxial cables to feed signals directly to the device via an RF port, bypassing the device’s antennas. OTA testing radiates signals wirelessly to the device from an antenna into a controlled RF environment, which typically consists of an anechoic chamber and specialized equipment to precisely control signal levels, angle of arrival, and signal polarization and to suppress unwanted signal reflections. OTA testing accounts for the contribution of the device’s antenna and form factor but adds complexity and cost to the test setup. Anechoic chambers have significant over- the- air transmission losses of the order of 4. This is not a problem with low- power GPS signals (typically in the –1. Bm power range). For conducted testing this can be achieved using coaxial splitters and addressing any isolation issues. For OTA tests, antennas must be separated adequately and located such as to avoid cross- coupling and to ensure that the received signals are uniformly distributed across the array. For example, the TWG testing used chambers ranging from a single assisted- GPS (A- GPS) device within a 1. GPS devices within a 4. An essential aspect of lab testing is the generation of RF signals. For GPS blocking interference tests, at least two RF signal types must be generated: the GPS satellite signals and the blocking signal. The GPS signal generation can be accomplished through either simulation or a record and playback method. Simulator testing allows receiver performance to be compared with a precise reference “truth,” enabling performance to be accurately quantified. The application of controlled changes, including in this case the LTE signals, enables evaluation of performance under a wider range of scenarios. A key benefit of this approach is that it enables the full rich, and perhaps chaotic, RF environment within the sampled band to be captured and replayed. Simulation and record and playback are generally complementary approaches and hence are often used together in a wide- ranging test plan. These signals were then captured using a vector signal analyzer for playback on a vector signal generator. Because most signal generators are not able to generate a signal compliant with Light. Squared’s proposed spectral mask, a representative bandpass filter was employed at the output of the vector signal generator. The relevant performance metrics collected and reviewed by most sub- teams during the TWG lab test campaign were: carrier/noise ratio (C/N0), response time (also known as time to first fix, or TTFF), and position error. Although C/N0 proved to be a good metric for assessing and comparing the impact on GPS receivers as LTE signal power is increased, it is not a metric that an end- user would normally encounter. To understand real- world performance degradation, response time and two- dimensional (2. D) position error are often more useful KPIs. The performance of many GPS devices is dependent on various augmentation systems. For example almost all mobile phones currently deployed in North America, require assistance data (e. Doppler, and their associated uncertainties) when operating in A- GPS mode. High- precision receivers use commercial and other space- based augmentation services to provide correction data. In addition to GPS signals, lab testing requires these augmentation elements to support the normal operating modes of these devices. The SMLC or PDE must be tightly coupled to the GPS signal generator so that the simulated assistance data is consistent and accurate. These messages and data can be mined for performance metrics by an automated test system. Automation is often an essential element of lab testing, particularly when the scope and scale of tests is large. A challenge such as the Light. Squared TWG testing with its aggressive timelines would be impossible without it. The benefits of automating the testing include. Greatly reduced test times. Elimination of regular human intervention with the test system, offering reduced error and uncertainty High repeatability: a typical test algorithm involves cycling through various GPS satellite scenarios and sweeping through a range of blocking signal levels while recording the data generated. All these elements benefit substantially from application of automation. A- GPS Cellular Device Testing Testing of A- GPS cellular devices in the lab can make use of conducted or OTA test configurations. Figure 3 and Figure 4 illustrate the conducted and OTA test configurations used for TWG Cellular Sub- Team testing, described in the May 1. FCC described in the Additional Resources section near the end of this article. For the OTA testing, the GPS and LTE interferer signals are presented at the same transmit horn to ensure alignment with existing industry- standard anechoic chamber test methodologies and to maintain an acceptable measurement uncertainty limit. Care was taken to ensure consistency with Light. Squared’s base station emission mask by using representative transmit filters in the test setup. To accomplish this, testing can be performed in accordance with industry technical standards. The standards used during the TWG GPS Cellular Sub- Team testing were. GPP TS 3. 4. 1. 71 for UMTS and GSM UUT’s. GPP2 IS- 9. 16 for CDMA UUT’s. CTIA Test Plan for Mobile Station Over the Air Performance, Version 3. The test objectives addressed multiple representative use cases.
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