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Efficient Design and Analysis of Airborne Radomes
Alexander E. Braun
West Coast Correspondent
At the New York World’s Fair in 1939, the General Motors Pavilion, “Highways and Horizons,” stole the show with its Futurama presentation. Seated on chairs fixed to a conveyor belt, 28,000 people took a 15-minute ride into the future every day. Futurama’s 36,000 square feet of dioramas, modeled to appear as if they were viewed from a low flying plane, depicted the wonders of 1939’s future. Cities were soaring towers of steel and crystal quartered by enormous parks, and farms had orchards that fruited all year under glass domes. Everything was linked by seven-lane highways that were elevated when they cut across a city, bypassing its streets, and large, trailerless trucks loaded and unloaded cargoes inside buildings to avoid traffic disruption.
A centerpiece of the presentation was the airport, which boasted circular runways that floated on deep pools of mercury enabling them to turn into or away from the wind to allow gigantic transatlantic dirigibles to be moored or depart safely. Every so often the narrator paused to allow the stunned audience to catch their breath and remarked, “Unbelievable? Remember, this is the world of 1960!” As Arthur C. Clarke once put it, “The future isn’t what it used to be.”
The World of 2002
Imagine aerodynamic automobiles and trucks, a mere 12 feet apart, speeding along highways at 100 mph while commuters read, schedule meetings and receive e-mail on their palmtops or just snooze on their way to the office. Meanwhile, the vast nationwide highway network of sensors and computers that controls each vehicle safely eliminates the driver’s triple whammy of traffic jams, accidents and stress. As a byproduct, this intelligent transportation system (ITS) reduces accidents by 80 percent while it increases the efficiency of some highways by as much as 200 percent per lane. Figure 1 shows a simulation of this ITS in operation.
This concept is not 1939 daydreaming, but the vision of the National Automated Highway System Consortium (NAHSC). Approximately $20 M of a $200 M research and development budget — 80 percent of which has been financed by the federal government — has been spent already to bring the ITS vision closer to reality.
This month, the NAHSC will demonstrate a system along 7.6 miles of San Diego’s Interstate 15’s commuter lane that steers, turns and stops a car. Automobiles from various manufacturers will participate, loaded down with radar gear, more computing power than all the moon missions put together had available and assorted gadgets such as magnet sensors and vision gear. Although this preliminary demonstration system requires a driver to accelerate and brake, by 2002 the NAHSC expects to present the federal Department of Transportation (DoT) with a workable plan for equipping both cars and highways in such a way as to make the driver mostly irrelevant. The DoT then will decide where (and if) to begin this national retrofit process. Figure 2 shows the test of one such system where the car follows a series of buried magnetic markers that direct it along an established route.
Is ITS a stillborn vision of the future, like 1939’s world of 1960, or truly the shape of things to come? Implementation costs aside, the technologies with which to build such an intelligent traffic control system and vehicle already exist, albeit in bits and pieces, like a jigsaw puzzle; vehicle navigation systems, anticollision radar and cellular data systems are available now. The question is whether all the pieces will be brought together to work harmoniously and produce the automated, intelligent vehicles and highway transit control systems the NAHSC is considering. So, let us consider the puzzle pieces.
Radar Detectors to Warning Systems
The technology that produced police radar detectors for automobiles is creating an entire new family of products designed to provide road information to motorists. The technical challenges that had to be solved and how the solution was achieved make for an interesting tale because good, stable, inexpensive radar transmitter components operating at 24.1 GHz, the frequency of interest, are not easy to find. A few companies, such as M/A-COM, provide them. Figure 3 shows the M/A-COM 24 GHz traffic-monitoring system.
Under the sponsorship of the Safety Warning Foundation L.C., a Florida partnership owned by 80 percent of the radar detector industry, Georgia Tech developed the Safety Warning System™ (SWS). According to Gene Greneker, principal research scientist at the university, SWS will make a very good test bed for some of the concepts being advocated for ITS, specifically in-vehicle signing, which is a means of providing the driver with warning messages on road conditions.
The SWS concept is being developed by MPH Inc. of Owensboro, KY, a leading manufacturer of police radar, under license from the Safety Warning Foundation. SWS consists of two system elements: a transmitter and a radar detector receiver or stand-alone safety warning receiver/display system. The transmitter can be mounted on police cars, emergency vehicles, and utility company and highway repair vehicles, as well as stationary locations along the highway. Reception range is between a half and one mile, depending on terrain. The transmitter’s antenna pattern can be shaped so that lanes in only one direction receive the alert, or the warning message can be broadcast in all directions. The system uses the same homodyne radar transmitter/receiver for communications purposes, so it is a dual-purpose system. Figure 4 shows an SWS transmitter. Figure 5 shows typical automobile SWS receivers equipped to display the alphanumeric warning messages.
When a highway patrol vehicle turns on its emergency lights, the unit’s radar activates and determines whether the vehicle is moving or stationary. If the vehicle is moving, the radar transmits the message, “Police in pursuit.” If not, the message, “Stationary police vehicle ahead,” is sent. The message is picked up by an SWS unit or a radar detector in the motorist’s car. If the radar detector is one of the high end models that have been manufactured since June 1996, it has an alphanumeric display and possibly a voice synthesizer. In that case, the display will flash the message while the voice synthesizer announces, “Police in pursuit.” Low end detectors will have a light-emitting diode labeled SWS and its flashing pattern will communicate whether the warning’s subject is moving or stationary. The system is capable of sending 64 different messages using a fixed transmitter. The fixed SWS transmitter site will operate in four modes: radar, time, continuous transmit and contact closure.
In the radar mode, the system activates every 0.5 s to determine whether anything is within range. If no vehicles are in range, the system shuts down. In a situation where roadwork is being performed and there is a need to warn motorists, for example, the system determines whether the posted speed limit is being exceeded. If it is not, no warning is emitted; if it is, a warning concerning a work zone ahead is issued. The time mode allows the operator to set four independent turn-on, turn-off times during any 24-hour period to warn of the presence of schoolchildren, for instance. If a message is important, such as a serious accident, the operator can use the continuous transmit mode to repeat the warning. The contact closure mode uses sensor arrays. For example, a portion of a highway may be subject to heavy, localized fog. If the roadside in that area is equipped with a fog sensor, whenever visibility is impaired the sensor would close a relay and activate the safety warning transmitter, which would send the message “Heavy fog ahead.” The same thing would be true for a pavement icing sensor, which is especially useful in the case of black ice on the road.
The radar detector industry is planning to produce a safety warning receiver without radar warning capability that will allow the receiver to be used, particularly by trucks, while traveling through jurisdictions that ban detectors. MPH is ready to produce a mobile transmitter when it receives the go-ahead from the Federal Communications Commission. The system will be licensed under Part 90 as a radar with ancillary functions as a communications device.
The system will be fielded on vehicles on a voluntary basis, with motorists either buying a unit or selecting it as a built-in option for a new car. The SWS infrastructure probably will be established through local DoTs. Additional functions are expected to be built into fixed-site SWS transmitters, which will do more than warn motorists. The system’s radar also will allow collection of traffic data, such as traffic flow, which currently require two or more sensors. Although two-way transmission is not being contemplated to obtain data from vehicles, an undisclosed application, which would use the LO’s leakage, is being considered.
“The biggest technical challenge we had was to accommodate the approximately 10 to 20 million radar detectors already on the highways of the US,” recalled Georgia Tech’s Gene Greneker. Because these numbers represent an immediate installed population, it was decided the messaging system should be designed to affect those detectors also. Initially, Georgia Tech considered some sort of selective beep that would set it apart from the normal traffic police radar warning. However, this approach was unsuccessful because each detector manufacturer performs its processing differently.
The solution was the use of a marker frequency, transmitted for 0.5 s, before coming out with the data burst. This time period is also the 0.5 s during which the homodyne radar in the fixed site samples the environment. The 0.5 s transmission is enough to set off an ordinary detector, making it react as if it is being illuminated by K-band police radar. “Because the warning registers like ordinary police radar,” said Greneker, “the driver slows down and takes notice.”
Greneker believes that although dedicated ITS deployment will take years, a fielded base of technology and products exists with which to begin. “SWS is a cutting-edge test for some of the ITS in-vehicle signing concepts. Thirty years from now I hope we will have a vehicle that will tell us we have a call on our mobile while it makes priority decisions as to which message to display when. Maybe at the moment the SWS instructs us to leave the highway, our side warning radar is telling us we have someone in our blind spot, and then the system sorts it all out.”
ITS and Long-haul Trucking
At first glance it would appear that the professionals of the road, the long-haul truckers, would be the first to welcome and benefit from ITS; but the reality is not quite so straightforward. Commercial systems already in use put this theory into perspective. QUALCOMM’s OmniTRACS® system is a form of ITS that is already deployed successfully. The geostationary satellite-based mobile communications system provides two-way data and position-reporting services, as shown in Figure 6 . QUALCOMM has prevailed against industry giants and is now the number one manufacturer of satellite communication terminals with almost 200,000 mobile satellite communications terminals deployed worldwide.
According to Tom Doyle, vice president of marketing at QUALCOMM’s OmniTRACS division, ITS is focused on the concepts of either using tag technologies and/or placing cameras along the roadside. “Roadside infrastructure is oriented towards the collection of traffic data. It is fair to characterize the technologies involved as having the potential to serve the broad-based transportation market, including passenger cars, not just commercial vehicle operation [CVO].” From Doyle’s perspective, most of the work being performed has been oriented more toward broader consumer markets as opposed to focusing on CVO.
“There are several instances of apparently fairly successful rollouts of some infrastructure in certain isolated corridors,” said Doyle. “But from a long-haul trucking perspective, it’s useless.” In the long-haul trucking market, having traffic data for just a few corridors is not helpful. Economically, long-haul trucking cannot depend on a patchwork quilt of systems until they provide enough coverage to make it worthwhile to integrate them into operations and systems. Paradoxically, whether or not these few systems are compatible with one another is irrelevant to the long-haul trucker.
This difference in perspective is only one of many important distinctions of commercial vehicle applications and their consumer counterparts. “Many, if not most, personal vehicle applications give the driver information to determine how to get to where he wants to go,” explained Doyle. “For the trucker, however, those decisions — where he should go, what routes to take, and when he should get there — are made by the dispatch center.” Because these decisions are not made by the individual truckers, in the long-haul trucking world traffic data need to be sent directly to the dispatch center, not the vehicle.
At the dispatch center, traffic information becomes part of the data used to make decisions about how to dispatch and route the driver. Thus, even with a fully deployed ITS, the truck driver would still end up being assigned a route without knowing (or caring) why it was selected. Therefore, contrary to the situation of a passenger vehicle that needs to receive data directly, system compatibility problems are not a concern. For commercial, long-haul vehicle applications the only concern over the compatibility of ITS systems would be that they are able to work with the dispatch center. Even if this was not the case, conversion routines probably would be available in the dispatch center’s database to change various incoming data formats into a common format that can be processed by the dispatch computer.
Low earth orbit (LEO) satellites are expected to play a leading role in long-haul ITS transportation, in particular the planned GlobalStar™ constellation of 48 LEO communication satellites. This system is a good fit with QUALCOMM’s code-division multiple access (CDMA) wireless communications systems.
GlobalStar was founded as a joint venture between Loral Space & Communications Ltd. and QUALCOMM, and now others. The GlobalStar LEO satellite constellation is targeted for broad-based services that will include both consumer and commercial vehicle applications.
“In a few years,” said Doyle, “we expect GlobalStar to be an important resource, from a mobile communications standpoint, with which to provide voice, data, fax — a wide array of services with ubiquitous coverage. GlobalStar terminals and phones are being designed to be compatible both with the ground-based CDMA cellular infrastructure and the satellites so that the customer will have access to the ground-based infrastructure when it is available and, if not, then to the GlobalStar satellites.”
GPS, ITS and Service Applications
Mobile positioning and tracking applications have come of age with the development of the Global Positioning System (GPS). Although several different markets exist for mobile positioning, the main difference between these markets is the communications channel. Thus, how GPS is incorporated with communications tends to be a function of the particular need and market being addressed. Whichever way it is viewed, positioning technology is key to the development of ITS.
According to Tom Ellis, vice president and general manager of Trimble’s Mobile Positioning and Communications division, the company has customers in the long hauling as well as the ocean shipping arenas. “This is one of the reasons we have products in the [International Maritime Satellite] INMARSAT area,” said Ellis. “Because of the end user’s global nature, it is important to have a seamless communication channel enabling communications from one point in the world to any other point. In shipping this is important — not only for data messaging, but also for emergency applications.”
These applications are important for long-haul trucking as well. Ellis points out that the market is driven by the nature of the communications channel, which must be accessible seamlessly from anywhere. For example, the ability to integrate GPS and other intelligent features with cellular and address the commercial market reduces equipment and service costs. Thus, depending on requirements, the user has a number of options when it comes to automatic vehicle location (AVL).
Besides long-haul trucking, Ellis views the public safety market (primarily fire and ambulance services) as still in the early phases of their growth in terms of AVL. Industry observers believe that the AVL market is poised for exponential growth. Trimble’s experience is that mobile applications blending the use of GPS and data are taking off in the public service market, which promises to be the test bed from which many of these applications will make the transition into commercial and consumer markets.
In many cases, a public service customer will install a secondary system with a separate radio specifically for data. For this reason, Trimble does much of its public service market work with Motorola. That data system can be used for messaging, statusing and AVL. Since emergency services use dedicated frequencies for voice and data, there are no service charges, just an up-front equipment charge.
At first, AVL was considered just another option by public service providers. It was a situation similar to when police radio first made its appearance and there was resistance to its implementation, sometimes even from the police. However, with the passing of time and the deployment of a dozen or so key installations where benefits were observed in terms of public service and productivity, AVL has moved up on the priority list.
As police and other public service vehicles continue to become more sophisticated and GPS prices continue to drop, this capability will be embedded in every squad car. GPS information is not just position information, it adds considerable value to other data, such as accident reports.
The Accuracy Question
It does not appear the DoT will open precise positioning for everybody anytime soon. However, products exist that use differential measurements and, in some cases, integrate GPS with dead reckoning (basically a gyro hooked to the odometer, much as the more familiar inertial navigation systems). Prices on these products are also dropping as they are adopted more widely. Vehicle components of the Trimble GPS/AVL subsystem are shown in Figure 7 . Commercial fleets and security services providers, such as ADT and Brinks, are not the only ones who benefit from such systems. Automobile manufacturers, such as Cadillac and Lincoln, already offer their customers GPS/AVL programs.
Not being subject to selective availability, the military obtains 16 to 25 m accuracy. The civilian market has discovered that results can be made as good or better by using differential and augmented systems, depending on the system and need. With static systems it is possible to integrate signals over time and obtain increasingly accurate results. Of course in a mobile situation, such as a pursuing squad car, that luxury does not exist.
A worst-case accuracy of under 100 m is not unusual using a standard GPS. On average, accuracy is considerably better than that, depending on circumstances. The urban canyons of New York are one situation, an interstate in the middle of Iowa is another. The lack of precise positioning data and the options developed to assist performance are not the key barriers to applications. The impediments have been mostly market awareness, equipment price and communications charges, all of which now appear headed in the right direction for real growth.
The Security Market
Security is another important developing market for GPS. AVL and GPS deployment in the commercial marketplace is growing rapidly, particularly for security such as for high value assets and some cargoes. The key trigger is the availability of public networks like the existing cellular infrastructure, which already offers relatively inexpensive hardware and software adaptable to applications for trucks, limousines, shuttles and a variety of commercial vehicles. This existing network enables a regular cellular channel to be used to instruct a PC back at the base station to have the vehicle tracked. Not only is communication with the vehicle possible, but the base station can determine if the airbag is deployed or unlock doors if a key is lost.
Thieves have been apprehended when trucks are equipped with these systems even when the driver cannot set off an alarm because the vehicle’s position is known. Even if the abandoned truck is found later, it is possible to download the information to a device with a data-logging feature and determine exactly where it has been, where it stopped and for how long. These data, together with a map, are sufficient cause for a judge to issue a search warrant.
This application represents the emergence of a new service provider business for selling these kinds of services to commercial fleets. Cadillac and Lincoln already have programs for customers where, by pushing an emergency button (combined with GPS capability), the driver obtains access to a tow truck or police. Businesses such as armored car transports and fast-delivery services are considering applications of this technology for their customer base.
Ellis believes that after security the next GPS wave will hit the small and large commercial fleets. “Probably the largest segment that is really going to benefit from GPS, and data and communications cost, and how all that plays together is the utilities,” he said, adding that he expects much of this technology to be installed in service fleets and even small mom and pop operations such as plumbing, air conditioning and heating companies with six to 20 trucks.
According to Ellis, “We’ve barely scratched the surface. GPS will be so pervasive it will come with every new car within the next five years or so. It certainly is going to be just a commodity — a utility.”
The partnering of wireless technologies with GPS, which offers fundamental, reliable information, adds great value to other types of information. In turn, this coupling is leveraging other wireless technologies and causing two of the hottest areas in the market to converge. Information and wireless technologies are coming together with an overlay of GPS, creating new kinds of information that add value to existing as well as new applications.
Many in the industry think ITS is an idea whose time has come… maybe. According to Thomas Rose, director of strategic marketing at M/A-COM, Lowell, MA, “ITS is a good idea, but before the government gets what it wants, all the bits and pieces that are working out there independently are going to have to come together.” Rose added that although he believes ITS is inevitable, its implementation at the scale government visualizes may be as many as 20 years away.
Forward-looking radar (FLR), as shown in Figure 8 , is one of the ITS developments that is being fielded. The system not only warns about possible collisions, but keeps the driver informed about emergencies while reminding him or her not to tailgate.
Japan merits watching in the ITS arena. According to Rose, “The Japanese are deploying an extensive system. They already have considerable deployment of GPS on vehicles, and are starting to integrate it with their own trimode system.” The Japanese system uses three communications modes: FM subcarriers, infrared and microwave. Depending on the road structure being used (urban, suburban or highway), a different interface is used. “Many Japanese manufacturers already offer vehicles with one, two or all three modes, depending on where the consumer does most of his driving,” said Rose.
What the Japanese are implementing could be defined as a true ITS infrastructure; it is probably the best example of what will be a country-wide system. Rose believes the fact that this ITS system is being deployed and offered for sale means it soon will be integrated into original equipment manufacturers’ products.
Is the Japanese trimode system practical? Perhaps, but it requires three times as many beacon installations on the road. Three interfaces mean three times the cost and complexity. Part of this tactic is an attempt to limit the size of the cell sending vehicles the information so that the information received applies only to an individual within the specific coverage area. In an urban environment, the driver cares only about what is happening within a limited area. On an open highway, rolling along at high speed, the driver wants to know what might be miles ahead because he or she will be there soon.
Liability, Demographics and Government
The one-size-fits-all ITS futurist outlook may not be adequate for a country as diverse in geography and population as the US. The lifestyle, needs and environment of a motorist living in the middle of the Kansas prairie and one in downtown Manhattan are perceptibly different.
Another genuine concern is the possibility of a catastrophic failure or a terrorist act carried out on a system used by thousands of automobiles and trucks traveling 12 feet apart at 100 mph. Even with draconian federal enforcement of laws regulating vehicle maintenance, it is unlikely that if a sudden, massive, system-wide failure occurred everybody’s fail safes would operate optimally.
Liability in the actual fielding of ITS is another consideration. After assurances of anonymity, a member of the Society of Automotive Engineers who works for one of the big US automobile manufacturers addressed the liability problem: “These days if you hang anything on a car that requires a driver to do something he normally would not do, you automatically become liable. If cruise control had been developed today, no US car manufacturer would be willing to be the first to field it. New technology or applications of this type goes to Europe or Japan first, get[s] tested [and] developed, and it becomes their market. When there is sufficient demand here, the American companies — who may have originated the technology in the first place — have to form strategic alliances or license it from them.”
This fact is why true collision warning (a system that brakes the car independently of the driver) and magnetic strip guidance systems are considered farfetched by some. However, this is not the case for autonomous cruise control. The concept of installing sensors on vehicles to make the driver’s life easier by looking for obstacles, issuing blind spot warnings, and tracking how far ahead a car is and at what speed it is traveling seems practical and, most important, does not require a massive ITS infrastructure to operate. SWS also will become a reality. There may be some applications for airbag arming using radar technology; not to deploy the airbags themselves, but to regulate the threshold of the g sensors that actuate them.
In terms of other infrastructure components, there is feverish activity in wireless communications to move key information around on roads (where traffic problems are located). Deploying a robust communications system that would be used first to keep the infrastructure running and eventually to communicate warnings and advice to the driver is another strong possibility, particularly in light of the coming of CD-quality digital radio, which will be adopted on a nationwide basis. Once cars are equipped with this type of radio, its generous bandwidth will allow it to double as a road infrastructure receiver. In the US, digital radio probably will become a principal means of sending road information and warnings to individual vehicles.
Any infrastructure deployed on a national basis probably will first see the light of day in the Interstate highway system; whether on a state-by-state or multiple-state basis. It is likely that those states already experimenting with automatic toll collection will be among the first to test such a system.
Within the next three to five years the capability to download large amounts of data into a car will increase, particularly as a result of onboard navigation systems. Instead of carrying CD-ROM maps of cities, a driver will be able call for information on different areas to be broadcasted directly to the car’s navigation system. These capabilities, combined with GPS, will quickly spill over to all kinds of delivery vehicles as well.
However, the focus must remain on practical applications. The more a global solution is sought to solve every problem, the less likely it becomes that anything will be deployed on any sort of major scale. Practical, independent standard applications that can work together, such as traffic management and toll collection, are good examples of this fact.
ITS on any kind of large scale is not going to occur unless Congress backs a program like the NAHSC’s. However, for this legislative support to happen the people’s representatives must understand what the significance of this national goal is and stop posturing.
Unfortunately, Congress has too few engineers and too many lawyers. During sessions dealing with ITS, some of the members of Congress kept demanding to be told, “What is this ‘ITS’ thing?” while others loudly proclaimed it “a welfare program for Fortune 500 companies that no longer can market their defense products and, therefore, are attempting to jump into transportation using tax funds.” If any form of ITS is to take place, it will take a sizable (even by federal standards) and sustained investment to keep industry interested in developing and pursuing these technologies and markets.
If this interest and investment occur, will all the pieces needed to produce intelligent traffic systems and autonomous vehicles come together? This implementation is not simply a matter of funding and technology. Demographics could tilt the equation heavily, making it even more complicated to solve. An example taken from the computer industry is useful.
As more computing power has been required, processor and memory geometries have become smaller and more complex. Increasingly, lower operating voltage is needed to avoid frying these smaller architectures, resulting in a predictable, evolutionary migration from 5 to 3.3 V, and from there to 2.5 V levels. However, while it appeared that the next step, 1.8 V, is inevitable and major processor/memory manufacturers already offer product families that can operate at that voltage level, some are pausing as if they have reached a landing on a long staircase.
Personal communications systems such as palmtop computers are viewed as the initial (and principal) users of 1.8 V processors and memories. However, there are indications that consumers are shying away from today’s continuous inundation of data, omnipresent communication and the Internet (whose main use still is e-mail after all).
People no longer appear as enthusiastic as they once were over the possibility of carrying the office wherever they go. This, in turn, means that the demand for sophisticated palmtops capable of making and receiving calls, doing word processing and spreadsheets, and sending and receiving faxes and e-mail may not materialize for quite some time (if at all). A vice president of one of the processor/memory manufacturers put it best: “We’re not going to see palmtops on the golf course or at the beach anytime soon. And if the demand isn’t there, we’re not going to rush in to fill it.”
This change in perception regarding new technology is related to the nationwide ITS. Leaving aside its potential for liability questions and new, more devastating forms of terrorism, the fact remains that nobody today can factor how its need will be perceived and affected by future changes in work habits and patterns.
Other than the fact that it is going to be a sizable number by the time the new millennium rolls in, statistics disagree on how many Americans will work away from the office. Fiber infrastructure in major cities, cheaper computers, advances in video conferencing over the Internet, virtual reality developments and wireless networking already make an actual physical presence at the workplace irrelevant for a large percentage, if not a majority, of corporate employees. That technology is here now. If environmental, economic or other concerns modify only slightly the current corporate culture that demands a physical presence at the workplace, transportation needs may alter fundamentally as larger numbers of people work from their homes or at satellite offices. The constellations of geosynchronous-orbit communications satellites have put us all only 45,000 miles away from each other. So, when all of these trends are factored in, what shape ITS will take becomes anyone’s guess. “Prediction,” somebody once remarked, “is difficult, particularly about the future.”
The ITS simulation and NAHSC test photographs are courtesy of the NAHSC. The traffic-monitoring system photograph is courtesy of M/A-COM. The SWS transmitter and receiver diagram are courtesy of Georgia Tech. The OmniTRACS system diagram is courtesy of QUALCOMM. The GPS/AVL subsystem diagram is courtesy of Trimble. The FLR system illustration is courtesy of Delco.
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