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.

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 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 80 percent of the features of the top-end simulations systems, but its more capable (Series 6) systems sell in the $20-30k range. 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. “It doesn’t take a navigation scientist to operate these simulators,” said John Fischer, chief technology officer at Spectracom. 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, 64 channels, and four frequency bands covering both 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 100 people working for them, but the GNSS simulation group is around 12 strong.

Rohde & Schwarz is another relatively recent GNSS simulation entrant with new products for the market.

SMBV100A vector signal generator.

Its current offering — the SMBV100A Vector Signal Generator – can simulate 24 dynamic GPS, GLONASS and Galileo satellites.  The SMBV 100A has wide bandwidth and high output power levels. 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 1930s, and its experience with frequency synthesizers and similar equipment is being carried forward into what the company terms its “cost-effective” 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 SMBV100A; 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 NavX-NCS Professional

In the meantime, IFEN in Germany is focusing on its NavX-NCS Navigation Constellation Simulator range of multi-GNSS signal simulators.

IFEN emphasizes the flexibility of its design, with a platform scalable from a 12-channel GPS L1 system up to a full multi-GNSS system with 108 channels and 9 frequencies for 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 2013, all IFEN NavX-NCS GNSS RF signal simulators are to include BeiDou B1 signal capability in accordance with the official Chinese BeiDou B1 ICD, and are ready for the other B2 and B3 BeiDou 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 ReGen 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 ReGen 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), ReGen replicated flight data (right).

Various configurations of ReGen 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 BeiDou Navigation Satellite System in addition to GPS, GLONASS and Galileo.

Spirent started shipping BeiDou-ready systems to its customers in 2012. Now these may be upgraded to full BeiDou capability using the information available in the first full issue of the BeiDou-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 LabSat 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

Mark Sampson

By Mark Sampson, Racelogic

GNSS is changing. The days of only American GPS satellites providing signals to the civilian population are gone as new constellations are launched. GLONASS was a slow starter, but is now well established, and its signal architecture is now commonly implemented in manufacturers’ chipsets. Galileo is still very much in test phase with global coverage planned for 2019, although position fix using only Galileo satellites has already been demonstrated. The Japanese QZSS system, designed to aid navigation in urban canyons, is partially operational with further launches announced for the near future.

The latest openly documented network to come online is BeiDou-2, or BDS. Formerly known as Compass, the Chinese constellation now provides signals to China and surrounding areas, but plans for global coverage should come to fruition by the end of the decade.

Full control over its own constellation gives a country military, socio-political, and commercial advantages, especially if additional functionality — such as search and rescue services — is introduced alongside the standard navigational broadcast. BDS is unique in its use of a combination of standard-orbit and geo-synchronous satellites, the latter giving it a wider range of signal designed to carry more information.

The populace stands to benefit from a wide variety of localized and global satellite coverage, but only if there are end-user products available that actually make use of the new signals. Any manufacturer wanting a share of the market in China, for instance, will need to get BeiDou-2 integrated into its chipsets quickly, especially if an import levy is placed upon devices that don’t support it (as nearly happened with GLONASS).

How do you go about implementing BDS support in your new GPS product if you’re based in Europe or America? The coverage isn’t global yet; you can’t just go out into the office car park to test, and how are you going to incorporate the signals from the three geostationary satellites without actually being underneath them? Moving to China isn’t very practical, so the solution is a GNSS record-and-replay device.

Manufacturers and other customers will want to seek out simulators from companies that have been highly proactive in ensuring their products provide full support for each constellation, even before they come fully online. The convenience in being able to test new designs, applications, and system integration with reliability and consistency can bring significant savings in development cost and time.

With 14 BDS satellites currently in operation, and the recent release of the Interface Specification, we find more and more companies in the marketplace have been asking for BeiDou functionality. An added benefit for existing users would be flexible hardware capable of taking a simple firmware upgrade in order to record and replay BeiDou as well as GPS and GLONASS.

Icing on the system-testing cake would be a hard drive containing pre-recorded scenarios from China and Europe, with good BDS visibility, so that bench testing can commence immediately. Given that such a device can record raw signals, live recordings can be taken in Asia and then transferred to test facilities around the world.

Mark Sampson is Racelogic’s LabSat product manager. He has more than 15 years of experience in the development of GNSS technology. Working closely with leading businesses such as Bosch, Intel, Samsung, and Telefonica, he provides knowledge and expertise in testing any GNSS device, application, or integration.

GNSS have been with us for more than 30 years, giving rise to a wealth of positioning and navigation technologies for military, civilian, and consumer use. Today, we’re entering a new era of experimentation and innovation in satellite and hybrid positioning. In turn, this drives new test challenges and introduces an ever wider group of engineers to the art and science of GNSS test.

Where Is the Testing Panacea? I am sometimes asked, “What is the best way of testing a GPS receiver?” — as if there existed some laboratory panacea to all GNSS test and characterization woes. Well, there is a saying, “There are horses for courses,” meaning what performs well in one situation may not deliver in another, and nowhere is this more true than in the field of GNSS test. Not only is there a wide range of different test equipment available, but there are no universally applicable test objectives, test methods, or parameter definitions, in exactly the same way as there is not one universally applicable GNSS receiver. Just as the rapid time-to-first-fix of an automotive receiver may be less relevant in a maritime environment, so different test approaches have their place.

A Systematic Approach. If there is one thing, it is this: be systematic in your test design. Consider the purpose of the test, the test conditions, and the measurements you plan to take, and be wary of generic tests that may not achieve your objectives.

Equipment. A wide range of GNSS testing equipment is available, ranging from basic single-constellation RF simulators to highly configurable, multi-GNSS constellation simulators. Single-channel, multi-channel, and record and playback systems all have their place, and to get the best results in the fastest time, it’s essential to choose the kit that’s right for the kind of testing you need to do.

Vulnerability, Fidelity, Integrity, and Time Travel. More and more, receivers need to be tested for their vulnerability to interference, jamming, and spoofing. As GNSS-derived position and time become more ubiquitous, so the motivation for confounding the system grows. This has a double impact on test.

First, performance requirements around vulnerability may be introduced, with tests to match. Second, and perhaps less obvious, is the way in which this concern is reflected in the receiver’s design and potential rejection of the laboratory test signal. Yes, I mean receivers getting more fussy about the signals they lock onto. Anyone who has tested a receiver with an out-of-date recording or simulation scenario will have experienced a receiver refusing to track a satellite showing a time and date prior to its firmware release date. The receiver, discounting time travel, knows there has to be something wrong with a satellite showing a date before it was born. With the risk of spoofing, receivers will only get more picky and likely to reject poorly simulated signals. To avoid such effects, it is important to have very high integrity and fidelity in any simulator system. Getting these details right is not esoteric, but is essential to allow the proper attribution of any problems observed and if test results are to have any meaning.

Conclusion. Be systematic in your approach to test; beware the universal and generic; “good enough,” it rarely is.

Steve Hickling is lead product manager for Spirent’s GNSS simulator business and is based at the factory in Paignton, England. Previously he held a variety of marketing, technical, and management roles in the telecoms and optical components industries. He holds a bachelor of science degree in physics and electronic engineering from Birmingham University, an MBA from Open University Business School, and a post-graduate diploma from the Chartered Institute of Marketing.

Today’s customers ask for high-accuracy positioning everywhere, even in the most demanding environments. The time is long gone that the only requirement for a receiver was to track GPS L1 and L2 signals in open-sky conditions. State-of-the-art receivers operate in increasingly difficult conditions, cope with local radio-frequency interference, survive non-nominal signal transmissions, decode differential corrections from potentially untrusted networks — and more!

Difficult real-life operating conditions are typically not addressed in textbooks or in the specialized literature, and yet they constitute the real challenge faced by receiver manufacturers. Most modern GNSS receivers will perform equally well in nominal conditions, or when subjected to nominally degraded conditions such as the ones that correspond to standard multipath models. However, the true quality of a GNSS receiver reveals itself in the environment in which it is intended to be used.

In view of this, a GNSS manufacturer’s testing revolves around three main pillars:
◾    identifying the conditions and difficulties encountered in the environment of the intended use,
◾    defining the relevant test cases, and
◾    maintaining the test-case database for regression testing.

In developing new receiver functionality, it is important to involve key stakeholders to comprehend the applications in which the feature will be used and the distinctive environment in which the receiver will function. For example, before releasing the precise-point-positioning (PPP) engine for the AsteRx2eL, we conducted a field-test campaign lasting a full month on a ship used for dredging work on the River Thames and in the English Channel. This enabled engineers to capture different types of sea-wave frequency and amplitude, assess multipath and signal artifacts, and characterize PPP correction data-link quality.

Most importantly, we immersed the team in the end-user environment, on a work boat and not simply in a test setup for that purpose. As another example, in testing our integrated INS/GNSS AsteRxi receiver for locating straddle carriers in a container terminal, we spent months collecting data with the terminal operator. This was necessary to understand the specificities of a port environment, where large metal structures (shore cranes, container reach-stackers, docked ships) significantly impair signal reception.

Furthermore, the close collaboration between the GNSS specialist, the system integrator, and the terminal owner was essential to confirm everything worked properly as a system. In both examples, in situ testing provide invaluable insight into the operating conditions the receivers have to deal with, much surpassing the possibilities of a standard test on a simulator or during an occasional field trip.

Once an anomaly or an unusual condition has been identified in the field, the next step is to reproduce it in the lab. This involves a thorough understanding of the root cause of the issue and leveraging the lab environment to reproduce it in the most efficient way. Abnormalities may be purely data-centric or algorithmic, and the best approach to investigate and test them would be software-based. For example, issues with non-compliance to the satellite interface control document or irregularities in the differential correction stream are typically addressed at software level, the input being a log file containing GNSS observables, navigation bits, and differential corrections.

Other issues are preferably reproduced by simulators, for example those linked to receiver motion, or those associated to a specific constellation status or location-dependent problems. Finally, certain complicated conditions do not lend themselves to being treated by simulation. For example, the diffraction pattern that appears at the entrance of a tunnel is hard to represent using standard simulator scenarios. For these circumstances, being able to record and play back the complete RF environment is fundamental.

Over the years, GNSS receiver manufacturers inventoried numerous cases they encountered in the field with customers or during their own testing. For each case, once it has been modeled and can be reproduced in the lab, it is essential to keep it current. As software evolves and the development team changes, the danger exists that over time, the modifications addressing a dysfunctional situation get lost, and the same problem is reintroduced. This is especially the case for conditions that do not occur frequently, or do not happen in a systematic way. Good examples are the GLONASS frequency changes, which arise in an unpredictable way, making it very difficult for the receiver designer to properly anticipate. This stresses the importance of regression testing. It is not enough to model all intricate circumstances for simulation, or to store field-recorded RF samples to replay later. It is essential that the conditions of all previously encountered incidents be recreated and regularly tested in an automated way, to maintain and guarantee product integrity.

The coverage of an automated regression test system must range from the simplest sanity check of the reply-to-user commands to the complete characterization of the positioning performance, tracking noise, acquisition sensitivity, or interference rejection. Every night in our test system, positioning algorithms including all recent changes are fed with thousands of hours of GNSS data, and their output compared to expected results to flag any degradation. Next to the algorithmic tests, hardware-in-the-loop tests are executed on a continuous basis using live signals, constellation simulators, and RF replay systems, with the signals being split and injected in parallel into all our receiver models. Such a fully automated test system ensures that any regression is found in a timely manner, while the developer is concentrated on new designs, and that a recurring problem can be spotted immediately. The test-case database is a valuable asset and an essential piece of a GNSS company’s intellectual property. It evolves continuously as new challenges get detected or come to the attention of a caring customer-support team. Developing and maintaining this database and all the associated automated tests is a cornerstone of GNSS testing.

Indoor location research and fielded developments currently focus on consumer-level applications, mostly using mobile phone handsets, but this work will hopefully also benefit professional and high-precision uses of GNSS. Indoor location technologies could be of particular interest in machine control for warehousing, industrial assembly, indoor and even underground mapping, underground mining, in forestry where dense canopy virtually cuts out GNSS, construction, and other areas where sky-view is limited or negligible.

Tune in to Indoor Nav Webinar Thursday

Tune in to GPS World’s webinar, “Indoor Positioning and Navigation: Results of the FCC’s CSRIC Bay Area Trials,” on Thursday, April 18. Speakers include Khaled Dessouky (Technocom); Ganesh Pattabiraman (NextNav); Norm Shaw (Polaris Wireless); and Greg Turetzky (CSR). Registration is free.

Professional users will want to keep abreast of developments in the E-911 area, and be aware as achievable accuracies begin to approach what could be possible for precision applications. Right now, that’s maybe a pretty big stretch, but taking a look periodically is a good idea. A recent round of landmark tests by the Federal Communications Commission (FCC) provides just such an occasion for a look-in.

The U.S., E-911 legislation put in place back in 2001 required that both landlines and cellphones should provide the location of callers to within specific accuracy levels. Location information was to be sent transparently to Public Safety Answering Points (PSAPs) which would allow fire/rescue/police personnel to be dispatched to the location of the 911 call. For mobile phones, cellphone manufacturers and network providers forged ahead and implemented a number of location strategies using differing technologies — all require being outdoors where a clear sky-view is available.

GPS and augmented GPS technologies were only part of the cellphone solution. Other implementations included use of the cell-signal itself, along with an extensive database that can contain, amongst other things, signal attributes and network asset locations. Turns out that, today, around 60 percent of mobile phone calls are made within buildings, so the FCC started to investigate how to bring E-911 capability to indoor calls.

In 2011, the FCC commissioned a group called the Communications Security, Reliability and Interoperability Council (CSRIC), and Working Group 3 (WG-3) is the one currently investigating what can be done for indoor E-911 location. Drawn from interested industry participants, the WG-3 Location-Based Services (LBS) sub-group set about finding what technologies exist, how well they work, and how they could be applied to E-911. Now, there are a lot of people trying to crack this problem and many, many ways that it’s been tackled — all of which are at different stages of development and with differing levels of capability. In order to make definitive progress, WG-3 LBS decided that a test-bed was the best way to evaluate and compare what’s currently available.

Seven vendors signed up initially, but only three — NextNav, Polaris Wireless, and Qualcomm — completed the rigorous testing, which set out to basically establish horizontal and vertical accuracy, speed of location, and reliability and consistency of results for each system. The trial tested the performance of location systems across urban, suburban and rural areas in the San Francisco Bay Area. More than 13,000 test calls were placed from various tested technologies in 75 different indoor locations selected by participating public safety organizations from around the U.S. Click here for the full report.

In the tests, Polaris Wireless used an RF pattern matching/fingerprinting technique, Qualcomm used a hybrid Assisted-GPS (A-GPS)/Advanced Forward Link Trilateration (AFLT) system, and NextNav used wireless beacon technology. NextNav came out on top, and largely within the magical 50-meter “search ring” requirement, and was the only vendor to provide vertical location capability.

NextNav uses pressure transducers in its beacons and in the handheld units to accurately measure calibrated altitude — within about 2 meters — so it can actually report the floor where the handheld is located; it’s the only system tested that was able to do so. Apparently the use of MEMS pressure sensors in cellphones is forecast to increase to 681 million units in 2016, so this could be the right approach.

NextNav is focusing on the San Francisco market, where the company has fielded a significant number of beacons, but it has also placed beacons in another 40 metropolitan locations across the U.S. NextNav has acquired appropriate spectrum rights to transmit a 900-MHz “GPS-like” signal that’s synchronized to GPS. This enables good penetration into most urban buildings — both high-rise and those with fewer floors.

To support adoption of its solution, NextNav is working with a chipset manufacturer to incorporate processing of its location signal within an upcoming spin of an embedded cellphone chipset. While other solutions have adopted Wi-Fi and cell-signal solutions, NextNav contends that its approach is the most cost effective, as beacon deployment is geographically less dense and can be amortized over so many users.

NextNav Beacon.

Other solutions also apparently rely on the use of databases that store signal characteristics and a number of other parameters – the CSRIC report highlights the complexity this brings to database management and maintenance. NextNav also has a database, but this is basically to store records of location, cable configurations and calibration data. This is only used to ensure consistent performance of their system; it’s not required for network operation or location.

Higher precision applications would also benefit from this type of augmentation in the same way that WAAS users achieve higher accuracies, except this system uses local beacons, and there could be the potential for even higher precision with known fixed beacon locations within urban environments. As commercial UAV applications grow, it’s not impossible that there will be higher precision flight applications within cities, for geo-location surveying, building and outside appliance inspections, signal mapping, traffic mapping, road-work repair monitoring — in fact, many of the monitoring activities we see daily in towns and cities where a view of the sky can be particularly restricted.

The CSRIC participants are not the only ones pursuing the holy grail of indoor location. As mentioned, seven different location vendors/technologies began the process to demonstrate their performance indoors through the common test bed, but only three completed the process. The others remain highly motivated and involved, however, and at work tuning their varied solutions. The WG3 report states, “The following location vendors showed initial interest in having their technologies tested and highlighted through the test bed process, but ended up not participating in the Stage 1 test bed, for a variety of reasons.

• U-TDOA Positioning (TruePosition)
• DAS Proximity-based Positioning (CommScope)
• A-GNSS / Wi-Fi / MEMS Sensor Hybrid Positioning (CSR)
• LEO Iridium Satellite-based Positioning (Boeing BTL).”

Meanwhile, promising indoor location research goes on at a number of commercial and academic institutions, such as the University of Calgary PLAN group, which has focused on integration of Wi-Fi and GPS. An upcoming paper reports that Wi-Fi, using the 802.11 standards, can be employed in several different ways as a complementary positioning technology for GPS/GNSS navigation, and the two can be used in an integrated framework to provide a continuous and robust positioning service.

Another promising component for indoor location could be the recent release of a software application by Baseband Technologies, which can provide rapid ephemeris for up to 28 days, between ephemeris downloads from GPS directly or over cellphones from the Internet. But indoor location warrants much more extensive treatment than these few random comments — what’s summarized here are only some recent developments in E-911.

There will likely be another round of E-911 test-bed activities if funding and management issues are resolved. See CSRIC WG-3 LBS Subgroup member Greg Turetzky’s “Expert Advice” column from GPS World for perspective and a forward look. We can anticipate even wider participation by differing technologies and even greater levels of performance in future. Longer term progression towards higher precision professional applications seems to be inevitable.

Tony Murfin,
GNSS Aerospace

Janice Partyka

But Google and Facebook Signal Their Intent to Capture Users’ Location

The biggest international mobile-phone show ever, Mobile World Congress 2013, took place early this month in Barcelona, Spain. It came at an interesting time. Attendees learned it no longer makes sense to think about which device, or screen, is of primary importance to users. Google reports findings that 90 percent of users move sequentially between several screens — TV, phone, desktop computer and tablet — to accomplish tasks.

Google, wanting to more fully exploit ad opportunities across all devices, has revamped its AdWords program to be one platform that advertisers will use to control ads on all types of devices. In the past, advertisers could choose to advertise on desktops and no other devices.  The new rule requires mobile advertising. Although it is an integrated platform, advertisers can use parameters like the device’s location or type to send specially crafted messaging.

The GPS-based fitness watch market looks like it is on a steep curve upwards, and feasible smartphone GPS watches are available.
Rumor says Facebook is going to start tracking users’ locations at all times, to be able to cull more ad revenue from individuals’ preferences and geo life.

Finally, and most importantly in the long run for all location-enabled users, the Federal Trade Commission took a stand on location privacy.

Google Requires Mobile Advertising. Citing concerns that the shift from desktop to smartphones and tablets is damaging its bottom line, Google is revamping its AdWords advertising platform to integrate ad campaigns across all device screens. In fact, Google indicated that it will require all advertisers to pay for mobile ads even if they only wish to reach consumers on desktops. The revamp will allow customers to use contextual factors like location, time of day and device type to control integrated campaigns.

Google provides an example of how a user’s location and device type could change the advertising message. “For example, a pizza restaurant probably wants to show one ad to someone searching for ‘pizza’ at 1pm on their PC at work (perhaps a link to an online order form or menu), and a different ad to someone searching for ‘pizza’ at 8pm on a smartphone a half-mile from the restaurant (perhaps a click-to-call phone number and restaurant locator),” reads Google’s blog.

Will Apple Grab Your Wrist? Rumors continue that Apple will release a GPS-based fitness watch in 2013. Whether Apple enters the market or not, the GPS fitness market is huge and growing. The GPS fitness watch market is set to reach $1.07 billion in 2013, predicts ABI Research. Cellular-connected GPS fitness watches like the I’m Watch may further speed this market.

“There have already been unfounded rumors around Apple in 2013, so let’s wait and see. If an Apple watch did feature integrated GPS, it would no doubt significantly boost shipment forecasts in 2013,” asserts Dominique Bonte of ABI. Some start-ups in the GPS Watch category have joined the action including Leikr, Pebble, Basis and others.

Facebook Is Watching. Is it possible for the relationship between Facebook and Google to get tenser? According to a Bloomberg article, Facebook is developing a smartphone application that will track the location of its users. The app is said to be scheduled for release by mid-March, and would run on handsets in the background, even when the Facebook app or the phone isn’t open or in use.

The location data would help Facebook capture more advertising revenue as ads can be more targeted with information about a user’s location and habits. The project is said to be headed by an ex-Googler and talent from Glancee and Gowalla, both of whom were purchased by Google.

Location privacy Is Covered. Privacy concerns with Facebook location tracking would undoubtedly be raised. Currently Facebook records the GPS coordinates of users when they post status updates or photos from their phones, or check into a venue. Tracking users 24/7 is another thing. Facebook’s current location sharing policy seems to cover them carte blanche. It allows the use of data “to serve you ads that might be more relevant,” and “to tell you and your friends about people or events nearby, or offer deals to you that you might be interested in.”

Also-Rans. Will Windows and BlackBerry smartphones succeed? Will there be a crack, even a tiny one, in the duopoly of iOS and Android? The biggest worry for Microsoft and BlackBerry is if initial sales of their smartphones are too small to excite developer interest. Without abundant applications, consumers won’t continue to buy these phones. ABI Research is predicting that the demand will be strong enough and is forecasting a BlackBerry installed base of 20 million and Windows smartphone base of 45 million by year end.

Location Standards for Next Generation LBS. The Open Geospatial Consortium (OGC) held a free session and reception at the Mobile World Congress for mobile developers, location data providers, network operators and LBS service users. Attendees learned the latest in open standards development.

Path Social Network Charged on Privacy Infringement. The operator of the Path social networking app has agreed to settle Federal Trade Commission (FTC) charges that it deceived users by collecting personal information from their mobile device address books without their knowledge and consent. The settlement requires Path, Inc. to establish a comprehensive privacy program and to obtain independent privacy assessments every other year for the next 20 years. The company also will pay $800,000 to settle charges that it illegally collected personal information from children without their parents’ consent.

The settlement with Path is part of the FTC’s ongoing effort to make sure companies live up to the privacy promises they make to consumers, and that kids’ personal information isn’t collected or shared online without their parents’ consent.

“Over the years the FTC has been vigilant in responding to a long list of threats to consumer privacy, whether it is mortgage applications thrown into open trash dumpsters, kids information culled by music fan websites, or unencrypted credit card information left vulnerable to hackers,” said FTC Chairman Jon Leibowitz. “This settlement with Path shows that no matter what new technologies emerge, the agency will continue to safeguard the privacy of Americans.”

Path operates a social networking service that allows users to keep journals about “moments” in their life and to share that journal with a network of up to 150 friends. Through the Path app, users can upload, store, and share photos, written “thoughts,” the user’s location, and the names of songs to which the user is listening.

In its complaint, the FTC charged that the user interface in Path’s iOS app was misleading and provided consumers no meaningful choice regarding the collection of their personal information. In version 2.0 of its app for iOS, Path offered an “Add Friends” feature to help users add new connections to their networks. The feature provided users with three options: “Find friends from your contacts;” “Find friends from Facebook;” or “Invite friends to join Path by email or SMS.”

However, Path automatically collected and stored personal information from the user’s mobile device address book even if the user had not selected the “Find friends from your contacts” option. For each contact in the user’s mobile device address book, Path automatically collected and stored any available first and last names, addresses, phone numbers, email addresses, Facebook and Twitter usernames, and dates of birth.

The FTC alleged that Path’s privacy policy deceived consumers by claiming that it automatically collected only certain user information such as IP address, operating system, browser type, address of referring site, and site activity information. In fact, version 2.0 of the Path app for iOS automatically collected and stored personal information from the user’s mobile device address book when the user first launched version 2.0 of the app and each time the user signed back into the account.

The agency also charged that Path, which collects birth date information during user registration, violated the Children’s Online Privacy Protection Act (COPPA) Rule by collecting personal information from approximately 3,000 children under the age of 13 without first getting parents’ consent. Through its apps for both iOS and Android, as well as its website, Path enabled children to create personal journals and upload, store and share photos, written “thoughts,” their precise location, and the names of songs to which the child was listening. Path version 2.0 also collected personal information from a child’s address book, including full names, addresses, phone numbers, email addresses, dates of birth and other information, where available.

The COPPA Rule requires that operators of online sites or services directed to children, or operators that have actual knowledge of child users on their sites or services, notify parents and obtain their consent before they collect, use, or disclose personal information from children under 13. Operators covered by the Rule also have to post a privacy policy that is clear, understandable, and complete.

The FTC charged that Path violated the COPPA Rule by:

• not spelling out its collection, use and disclosure policy for children’s personal information;
• not providing parents with direct notice of its collection, use and disclosure policy for children’s personal information; and
• not obtaining verifiable parental consent before collecting children’s personal information.

In addition to the $800,000 civil penalty, Path is prohibited from making any misrepresentations about the extent to which it maintains the privacy and confidentiality of consumers’ personal information. The proposed settlement also requires Path to delete information collected from children under age 13 and bars future violations of COPPA. Path has already deleted the address book information that it collected during the time period its deceptive practices were in place.

The FTC also introduces “Mobile App Developers: Start with Security,” a new business guide that encourages developers to aim for reasonable data security, evaluate the app ecosystem before development, and includes tips such as making someone responsible for data security and taking stock of the data collected and maintained.

The commission vote to authorize the staff to refer the complaint to the Department of Justice and to approve the proposed consent decree was 5-0. The DOJ filed the complaint on behalf of the Commission in U.S. District Court for the Northern District of California on January 31, 2013. The proposed consent decree will be filed with the same U.S. District Court today and is subject to court approval.

Janice Partyka is contributing editor for wireless at GPS World. Subscribe free to her monthly e-newsletter, Wireless Pulse, at www.gpsworldcom/subscribe.

System Health

John Pottle, Spirent Positioning Technology

Most people are aware that simulation forms a key part of GPS receiver development and testing.

However, simulators are also used as critical tools in other areas, from the development of a new GNSS system to testing system problems and effects of interference.

From the beginning of the Galileo program, simulators have been used to enable development of the ground segment monitoring receivers. These Ground Sensor Stations continuously monitor the performance of the Galileo satellites and provide information to the Galileo Control Centre in Fucino, Italy, from where correction messages are generated.

Galileo RF Constellation Simulators were also used for research and development testing of the initial user segment receivers for the Galileo system. These included not only the Open Service receivers but also development of the initial Public Regulated Service receivers that include the encryption algorithms.

Similarly, simulators have been used for many years to test receivers that actually fly in space, including on the GPS satellites themselves as well as missions like the Space Shuttle.

When GPS has a problem, the industry oftentimes relies on simulators to recreate the problem in the laboratory to help understand the issues and find fixes.

For example, when SVN-49 satellite issues were first noticed in April 2009, simulator scenarios were generated and made available to the industry in co-operation between Spirent Federal and the GPS Directorate. These scenarios helped with the characterization of the problems on board the satellite and also with looking at possible fixes.

More recently, simulators and other receiver test approaches were widely used to help with the understanding and quantification of the impact of the proposed LightSquared broadband network on GPS systems.

A wide range of simulators was deployed in the testing that was led by the Technical Working Group set up under the auspices of the FCC. The sub-groups of the TWG used not only RF constellation simulators but also live sky sample and playback systems for testing. A wide range of test approaches was adopted, including conducted testing (from the RF simulator via co-axial cable into the receiver front-end, bypassing the antenna and with antenna effects being modeled as part of the simulation where required) and over-the-air test approaches in small and large chambers.

Following the LightSquared testing the current debate is whether it would be helpful to have certification or standardization of GPS and other GNSS receivers in some form. Standards for GPS systems already exist in the safety critical areas such as aviation and maritime as well as in areas such as emergency location (E-911). Discussion on extending current A-GNSS standards to include other positioning methods such as Wi-Fi positioning and MEMS sensor-based positioning are also underway in various standardization forums.

Whatever the problems the industry and systems face today and into the future, one thing seems assured — simulation will remain a key tool to help create a repeatable and controllable environment to enable understanding and continuous improvements in navigation and positioning technology.

John Pottle has more than 20 years of experience in technical, marketing, and business development positions in communications and navigation. He is responsible for marketing at Spirent Communications’ Positioning Technology division in Paignton, UK. He trained as a communications engineer and holds a master’s degree in business administration.

Debug, Verify

Paul Myers, Spectracom

The affordability, shrinking size, and power requirements of GPS and GNSS receivers are accelerating their integration into a multitude of products: personal navigation, safety devices such as alarms systems and cell phones, telematics devices, camera systems, and timing and control systems. But the additional capabilities of position, navigation, and time/frequency synchronization come with an increased cost of test and verification.

Traditional lab bench development and field testing demonstrate operational capabilities. However, these methods alone may not reveal the subtle issues and fatal flaws found in the real world. Lab testing often demonstrates only the best or worst your test cases can offer. Furthermore, field testing only checks conditions and GNSS constellation operation for your location at specific times. Most integrators do not have the luxury of testing their product in the multitude of places their customers might use their product. This is where the application of a GNSS simulator adds value. GNSS simulators allow repeatable testing of real-world situations under a variety of test conditions and in a diverse set of simulated places at different times.

The first step of GNSS integration is to define requirements based on the product use cases. The prudent test designer realizes lab tests, field tests, and simulation all have a place in the product development cycle, and later in maintenance.

Once the product requirements and use cases are known, the type of GNSS receiver can be selected, and supporting software and hardware design can begin. High-level test design is best performed as you design your product. This allows you to better schedule and estimate project time and costs.

Your type of product dictates your test plan design. You will need to allocate some testing to the lab, some to the field, and some to GNSS simulation. The right test case allocation depends on your product type.

Depending on your product requirements, you may have to define navigation test cases, positioning test case, or time and frequency synchronization performance test cases. Position and navigation products require a GNSS receiver with sufficient accuracy and update rates to provide accurate position and navigation data. Time and frequency products, whether mobile or stationary, require a 1PPS output with a serial time code output and sufficient stability and precision to discipline an oscillator to generate precise time and frequency.

Identify which test cases require execution in the lab setting, which require GNSS simulation, and which demand field testing, then allocate them in the test plan to project phase. The old adage that lab testing can’t catch everything that field testing finds can be cheated by the use of GNSS simulation. GNSS simulations reduce cost and schedule time by avoiding repetitive field testing and integration cycles. Plus, simulation testing allows iterative development and retesting by virtually testing in the field.

For example, positioning and time and frequency products can initially utilize lab testing to iteratively develop features and accurately measure system performance. The GNSS simulation can then be leveraged to model the field environment under many different conditions, locations, and times. Finally, field beta testing then can validate the lab and simulation results with real-world beta site experience.

Similarly, mobile navigation or time/frequency products benefit less from lab bench testing and require more in field testing to verify operation under real-world navigation scenarios. Solution accuracy can be baselined in the lab, but accuracy in the field is vital for product success. A GNSS simulator can be used to test conditions, remote locations, and time/dates impossible to achieve using the real GNSS signals. This reduces some of your testing to defining use cases and making simulator configuration files. Without simulation you can only develop, ship, and then fix bugs found by your customers — all the while sweating bullets waiting for users to report problems found from untested situations or when leap seconds occur.

Finally, don’t forget to create regression tests from the verification testing already performed; this enables you to continue to maintain and re-verify product performance. Again, leverage the lab environment, GNSS simulator test cases, and your shipping product to create a product maintenance process. Remember, a smart designer develops the requirements, use cases, and test cases before completing design and development. And a smart integrator uses a GNSS simulator to field test the product before it ever leaves the lab!

Paul Myers is a principal engineer at Orolia USA. He has more than 20 years of experience in embedded systems development in defense and commercial applications. He has a BSEE from Clarkson University, an MSEE from Syracuse University, and is a graduate of General Electric’s Advanced Course in Engineering.

Modern Requirements

Markus Lörner, Rohde & Schwarz

Receivers for satellite-based navigation systems such as GPS and GLONASS can be found nowadays in many electronic devices to support location-based services. The faster and more accurately the actual position can be determined, the better the user experience will be. The devices are typically used not only in open space, where the reception conditions would be ideal, but more often in densely populated cities, where harsh conditions such as urban canyons with obscuration and multipath propagation are prevalent. To ensure optimal performance, the receiver needs to be tested and verified with repeatable scenarios that can only be provided by a GNSS simulator.

Standard tests such as time-to-first-fix and location accuracy need to be conducted for all GNSS receivers and modules.

When using a GNSS simulator, this is a straightforward task. The definition of harsher scenarios with multiple obstacles that generate obscuration and reflections is already much more complex, as there are no common test procedures defined. As a result, vendors must specify and generate their own test plans. This requires very flexible GNSS simulation solutions that allow direct access to the satellite constellation configurations.

Many of today’s state-of-the-art receivers are multimode receivers, which means that they support, for example, both GPS and GLONASS. They can therefore use satellites from both systems and still provide a location fix, whereas a single system receiver does not see enough satellites to obtain a stable 3D fix. Each of the two systems must be verified on its own, of course, but additional tests with both systems active are also required to make sure the receiver works properly with these hybrid scenarios. One additional test is to verify receiver performance when the system time of the different GNSS systems is drifting, since these system clocks are controlled and monitored separately.

Increasingly more important is receiver performance in the simultaneous presence of many other signals, such as Bluetooth or WLAN, at a much higher signal level. Another aspect is that cross-correlation distortion from other GNSS systems degrades the desired GNSS signal. Again, no official test requirements are defined in general. The Federal Aviation Administration instructs aviation receiver manufacturers to perform tests with additive noise and CW interferer. Ideally, these tests can be done inside the GNSS simulator.

To summarize, GNSS systems are used more often in especially harsh reception conditions, but users expect perfect location information almost everywhere. To ensure optimal user experience, greater emphasis must be put on testing. Addressing these needs requires a full-featured GNSS simulator, which ideally can also be used as an interference generator for Bluetooth and other standards.

Markus Lörner is a product manager for RF signal generators and power meters at Rohde & Schwarz headquarters in Munich, Germany. He joined the company in 2000 after receiving his degree in electrical engineering from the University of Erlangen-Nürnberg.

Success Factors

Mark Sampson, RaceLogic

With more devices now using mobile location-based services and the completion of the GLONASS constellation, it has become more important than ever that companies who incorporate multi-GNSS engines into their products have a reliable, cost-effective way of accurately testing these devices and applications.

Developing GNSS-enabled products within budget and to timescale has, however, always been a challenge. The traditional methods of repetitive field testing and expensive signal laboratory simulation have proved ineffective at offering engineers the repeatability and realism required to test how their devices perform in everyday, real-world scenarios.

Introduction of multi-constellation GNSS simulators has enabled R&D departments to effectively record and replay real-world signals in testing facility conditions, all at a cost-effective price. Providing engineers with the repeatability, consistency, and reliability required to effectively test a range of GNSS-enabled devices, these compact and light-weight systems cut development times by reproducing genuine satellite signals, all from the comfort of your desk.

Before you begin to see how your device performs, there are a number of factors to consider to assure successful GNSS testing is carried out. One of these considerations is the need to clearly pre-define objectives depending on the device or application to be tested and the stage in the product’s development cycle. These can include specific tests for the development of the product chipset, its module, and verification testing to ensure the product meets targets before it is released.

The other consideration is having to test signal reception from multiple satellite constellations to a single GNSS receiver — a special challenge for R&D departments, with system-specific reference frames, system-specific propagation models, timing offsets, date rollover, and cross-system impacts all having to be taken into consideration before successful GNSS testing can be implemented.

After these points have been resolved, using a simulator to simulate scenarios via live-sky signals couldn’t be easier. Connecting directly to an RF antenna input of a GPS engine and simulating the signals associated with navigation using GPS/ GLONASS / Galileo and satellite-based augmentation systems (SBAS), you can carry out highly repeatable tests without leaving the office.

Working alongside a simulation software, engineers can generate a data file that can be replayed on a simulator based on a user-generated trajectory file. This allows you to simulate almost any kind of dynamic profile, at a set time and date, anywhere in the world.

Mark Sampson has more than 15 years of experience in GNSS technology. He works closely with businesses such as Bosch, Intel, Samsung, and Telefonica, providing expertise in testing GNSS devices, applications, and integrations.

Why Test?

John F. Clark, CAST Navigation

Testing the operation and performance of a GPS receiver can be a time-consuming and complicated process. To achieve this effort, some receiver manufacturers and system integrators use a combination of receiving live sky GPS signals with an outside antenna as well as receiving signals produced from a GPS simulator.

While you may think that it is easy enough to just go out and put up an antenna to receive the GPS signals from the live sky, you need to ask yourself what it is that you are actually evaluating. Are you evaluating a position solution that contains the effects of local variations such as antenna shading due to placement of the antenna in relation to an existing structure? Are you seeing some effects of multipath being induced to the receiver solution? Is the placement of the antenna causing a larger than expected error? Will you get different navigation results by testing at different times of day? How do you test your receiver under dynamic conditions that contain vehicle motion? Due to the volatility of the GPS constellation, a satellite simulator provides you with repeatable and customizable test conditions.

A GPS simulator must model all transmission paths, anomalies, satellite motion, and user motion to provide you with the ability to control all aspects of the GPS signal to accomplish repeatable testing under known environmental conditions. A GPS simulator should also be capable of allowing you to define a specific time, date, and almanac to be utilized during the simulation, thus enabling you to reproduce the same GPS constellation characteristics as seen from a live-sky antenna for a specific time and location.

You can also use a GPS simulator to assist with the evaluation of new software builds for receivers, characterize a receiver, or evaluate multiple GPS receivers under identical operating conditions. A few simulators also provide the ability to drive an inertial interface, to assist with aircraft avionics integration and testing in a dynamic environment without leaving the laboratory for expensive flight testing.

Using a GPS simulator provides you with the ability to evaluate some operational specifications like time-to-first-fix, time-to-subsequent-fix, low signal-to-noise ratios, receiver loss of RF, reacquisition after signal loss, tracking of rising and setting SVs, and more.

Some GPS simulators also allow you to define and simulate multipath signals. The ability to define the characteristics of multipath signals provides you with a very precise and repeatable signal source to accurately measure and quantify the effects of multipath signals on carrier-phase measurements and receiver performance. This allows you to accurately characterize multiple types of GPS receivers, enabling you to select the appropriate receiver for use in different types of applications and operating environments.

John F. Clark is vice president, engineering, for CAST Navigation, LLC. He has more than 25 years of experience in the GPS industry, and has worked at CAST since 1991.

Charles Abraham

By Charles Abraham

As today’s handsets and consumer devices become more sophisticated, manufacturers continue to incorporate more and more functionality into a small and sleek form factor. Today’s range of smartphones incorporate voice and data transceivers, GPS, Bluetooth, Wi-Fi, cameras, music, touchscreen interfaces, compasses, motion sensors, cameras, storage cards, and many other technologies. Free turn-by-turn navigation services, such as offered on Google Android phones and iPhones, have created a compelling reason for many of us to own a GPS-equipped smartphone.

The pressure on manufacturers to integrate so many functions into one small printed circuit board has fueled a race among semiconductor suppliers to offer new solutions combining GPS and wireless connectivity. Phones that are small and comfortable to hold mean less and less space available for the internal electronics. Large screen sizes and the trend to thinner and thinner devices means smaller, less efficient antennas, placing pressure on chip designers to improve integrated circuit (IC) performance to make up for antenna constraints.

Finally, cost competition in these markets is intense, as operators compete to bring more users online.
These forces have shaped several changes in the wireless semiconductors found in new smartphones. Three important enabling technologies are:

• reduced-geometry semiconductor technologies,
• wafer-scale packaging, and
• combo chip integration.

Let’s look at the trends in each area.

Semiconductor transistor sizes have been shrinking for decades. GPS processors in the market today use transistor geometries with gate widths of 0.18 micrometers, 0.13 micrometers, 90 nanometers (nm), and 65 nm, the latter showing up in the newest handsets on the market. 40-nm-based ICs have been announced as well, and will find their way into the market in the next year or two.

Each generation of technology offers a 50–100 percent increase in density for pure digital circuits. This so-called shrink has allowed designers to both reduce the size of chips and to pack in more performance — in GPS chips this usually means more tracking channels and more correlators for faster signal search. The area for non-digital circuits such as the radio receiver in a GPS has not been shrinking as fast as the digital portion. This had led to changes in architecture, with more and more functions going digital. Examples include digital band-shaping filters, digital gain adjustment, and sigma-delta analog- to-digital converters.

Wafer-scale packaging has moved into the mainstream for GPS and other wireless ICs. Traditional ball-grid array (BGA) packaging requires placing a semiconductor die on a substrate. The substrate carries the balls (pins) and some interconnects, and the semiconductor die is connected to the substrate via wire bonds. For small ICs the overall package size may be 50 percent larger than the die itself, because of overhead of the space needed for wire bonds.

By contrast, wafer-level ball grid array (WLBGA) packaging yields a finished packaged part with the same dimensions as the underlying die. Wire bonds are not used; a redistribution layer (RDL) is bonded to the silicon wafers and carries interconnections from the silicon to the balls. This type of packaging yields the smallest possible board footprint. It also places strict limitations on the number of package pins, since the pins must all fit under the chip and cannot be spaced too closely, due to board manufacturing constraints. Often designers struggle to provide the features customers seek while abiding by package pin-count limitations. Pins are shared or multiplexed to preserve flexibility.

Combo-chip integration offers the ultimate solution for small size. A single IC with multiple functions will almost always be considerably smaller than several ICs on a printed board. The last two years have seen the introduction of several combo ICs containing GPS, including the Broadcom’s BCM2075 Bluetooth-FM-GPS combo IC. Combo ICs like this allow manufacturers to build cellular handsets that would be difficult or impossible to create using discrete chip sets. Since GPS, FM, and Bluetooth have become standard features across many product lines, manufacturers not only benefit from small size but also economies of scale, designing a single part into dozens of devices.

The benefits of combo ICs are easy to understand, but making these devices brings unique challenges. First and foremost, these ICs are wireless devices containing multiple sensitive radios, where every fraction of a decibel of performance counts. With few exceptions, handset manufacturers and their wireless operator customers are not willing to sacrifice radio performance in their quest for miniaturization and cost reduction. Each function on the wireless combo IC must perform as well as its counterpart function in a stand-alone IC.

However, in a combo IC the radios are at most a few millimeters apart from each other. Designing for this type of integration requires engineering attention at multiple stages of the design. Up front, during the system engineering phase, component specifications must be set that minimize interference between radio subsystems, considering not just the radios on the combo IC but the influence of other radios in a handset as well. For example, in setting the specification for the second-order intercept point of the GPS receiver, system engineers must consider the fact that transmissions in 825 MHz cellular band can mix with Bluetooth transmissions at 2400 MHz to yield an intermodulation product at 1575 MHz, right in the middle of the GPS receive band. Designers also choose clock frequencies to avoid interference; for example, a GPS baseband processor that clocks at 100 MHz might be changed to 75 MHz to avoid the FM receive band. These are just a couple of examples of the many scenarios and considerations that must be examined early in the design process.

Once the system engineer has done his or her job, the next level of interference mitigation falls on the analog designers. They choose where to place circuits, how to structure the semiconductor layers, how to drive and load interconnects, and how to properly filter supply voltages to avoid undesired interactions. Keeping spurious products off local oscillator signals is a key challenge. GPS receivers have 100 dB or more of gain to amplify very weak GPS signals to a usable level. Due to this high gain, even a tiny spurious product on a local oscillator can have the effect of tuning in an undesired cellular transmitter. For example, a spurious product offset 135 MHz will tune a cellular transmitter at 1710 MHz down to 1575 MHz, again right in the middle of the GPS band. Avoiding these interactions requires experienced designers who can anticipate complex issues. Mistakes can be costly, with each mask for each IC iteration going into seven figures.

As the challenges of combo ICs are overcome, it’s likely the future will bring even more in the way of wireless technology integration. This in turn will provide even more opportunities for GPS to penetrate a broader set of handsets and cellular devices, making this exciting technology available to more consumers every day.

CHARLES ABRAHAM is senior director of engineering for the GPS Business Unit at Broadcom, which he joined via acquisition of Global Locate, a company he co-founded in 2000. Previously, he worked at Ashtech, Magellan, Trimble, and Hughes Electronics.