Cellular locator number phone

Wireless carriers finally have a number of options when it comes to locating users.

D. Douglas Graham

Wireless communication is quickly becoming an everyday feature of modern life. According to Oliver Hilsenrath, president of U.S. Wireless Corp. in San Ramon, Calif., American wireless networks currently enjoy a subscriber base of approximately 60 million. That number will jump to 100 million early in the 21st century, Hilsenrath says. When that happens, one out of every three Americans will be talking on cell phones.

As cellular telephony has advanced with wireless locating, many emergency calls have moved to wireless media. Cellular emergency calls cannot be traced back automatically, nor can cell-phone users be located when in transit. In March 1996, the FCC took a hard look at these new challenges and required that all wireless carriers be equipped with a locating feature by the year 2001. The wireless industry has been scrambling for a solution ever since.

Almost every wireless location technology currently under industry discussion was originally conceived for defense purposes, the idea being to track your enemy's radio communications back to him. These strategies fall into two broad categories: handset and network solutions.

'Ninety-nine percent of wireless communication in wartime was based on tactical communications and signal processing,' Hilsenrath says. 'For this purpose, portable communications devices were developed that would become the ancestors of the modern cellular handset. There is a solution to the caller location problem that is dependent on the Global Positioning System (GPS). GPS is a satellite-based technology that is used to help boats and airplanes navigate. While the technology is sound, it does have its downside.' For instance, GPS requires a clear line of sight, which is not always available.

Right now there are more than 30 manufacturers of handsets across the globe, according to Hilsenrath. The units are shrinking in size, and the logistical problems involved in incorporating GPS into ever-smaller handsets are likely to be very daunting. Moreover, the idea of developing GPS-based locating technology may be problematic in itself. While GPS works fine if one is guiding a missile or helping a jumbo jet navigate its way across the ocean, using it on the ground would prove very troublesome because the signal would be blocked by thousands of natural and man-made obstructions.

Traditional network solutions work on the principle of triangulation. There are two approaches to triangulation. The first is based on angle of arrival, the second on time of arrival. In a typical military scenario, a communications network consists of two to five base stations. Finding the caller is a matter of calculating the call's line of bearing. Theoretically, the caller will be found at the intersection of the two lines of the angle of arrival. In military terms, this technique is also known as direction finding (DF). Time of arrival is used with at least three base stations. Callers are found by measuring the time required for the messages to be transacted. When time is translated to distance it becomes possible to trace the call to its source.

Triangulation is a step up from GPS, but here again a clear line of sight is imperative for the process to be effective. Both DF and time of arrival were developed on the battlefield where good line of sight could be achieved by simply moving one's tank. The trouble is that 70% of today's cellular traffic is generated in big cities with massive permanent structures all around.

RADIO CAMERAS

U.S. Wireless has created a solution that overcomes the line-of-sight problems associated with GPS and triangulation. 'Radio Cameras' - a trademarked term for the company's PC-sized locator - are deployed downtown and in rural places where a small number of stations are available. The boxes are installed at base stations throughout their operational area. There they go through a 'learning' process, by which calls are identified and 'fingerprinted' based on their location.

'The calls are ID'd based on their point of origin,' Hilsenrath says. 'Every call received by the base station gets a location-fingerprint which the camera recognizes down the road. This solution overcomes the line of sight problems that you get with GPS-dependent locating technology and triangulation. Because a Radio Camera is not triangulating but fingerprinting, it does not require the cooperation of two or three bases.

'The technology also exceeds the criteria for accuracy stipulated by the FCC ruling. To meet the FCC's requirement, location must be accurate up to 125 meters. Radio cameras are accurate to 20 to 40 meters, which is four or five times more accurate that the rule requires. This is not a bonus but a necessity. If you're chasing down a 911 medical emergency in a big city, you need to get as close to the mark as is reasonably possible.'

FIND IT ANYWHERE

For a location technology to function in the real world, it must be low cost, fully mobile, and auto roaming, according to Dick Gossen, president of Aeris Communications, Inc., San Jose, Calif. Aeris MicroBurst technology meets this criteria, Gossen says, and because the solution is designed to service the entire marketplace, it may soon become the Holy Grail of location technologies.

MicroBurst is implemented as an overlay on the nation's cellular system, making use of certain frequencies or channels that are usually underutilized in the normal operation of the cellular system. A portion of the cellular spectrum is allocated for control and overhead transactions to support call setups, tower-to-tower handoffs, and overhead or background handshaking that needs to occur between a normal cell phone and the cellular switch downtown. These overhead channels are currently used at only 10% of their actual capacity.

MicroBurst uses the remaining 90% without interfering with or compromising the normal voice cellular operation. The technology gives users access to a nationwide, fully mobile, two-way data transport utility. Aeries operates a central data clearinghouse connected to all the carriers over the normal SS7 signaling network, providing a single point of connectivity to a broad array of fixed and mobile data applications, including position tracking.

'Tracking trucks and freight is one thing,' Gossen says, 'but how do you get the position information to the customer? The answer is to use the cellular system for the collection of data, and the Internet as the information distributor. One of things that is unique about Aeris is that we are a point of presence on both networks, making us an internetwork data distribution company. This is a first in the Internet world.'

'MicroBurst also has the advantage of being ubiquitous, and this feature is one of the primary reasons that our customers have embraced it,' Gossen says. 'One of them, Qualcomm, invented and deployed CDMA [code division multiple access] cell-phone technology. Omnitrax, a division within Qualcomm, performs tracking services for long-haul trucking companies. Currently, 300,000 vehicles carry Omnitrax equipment. When Qualcomm first looked at MicroBurst, the technology had only 25% coverage of the U.S. and could not offer the seamless, coast-to-coast coverage they needed. That situation has since changed, but in the beginning they could not get behind MicroBust until we were able to demonstrate that it would soon work all over the country.'

TIME TRAVEL

Time Difference of Arrival (TDOA) is the locating method pioneered by Cell-Loc, Inc., Calgary, Canada. According to chairman & CEO John Webb, TDOA measures the time required for a signal to travel from a handset to a base station. When this process is duplicated three or four times, it provides the data needed to perform a mathematical process known as hyperbolic trilateralization. Similar to triangulation, trilateralization works with very high-speed measurements. Because it works in nanoseconds, the process provides extremely accurate location information that can be used to track vehicles in motion, or follow a medical emergency call to its source, even in a hectic urban environment.

'For something like this to work you need a method that not only moves quickly, but also deals effectively with environmental conditions that would normally impede RF transmission,' Webb says. 'Cell-Loc's patented process accomplishes this. We've been trialing the product with carriers in Alberta, and the results have been extremely encouraging. We expect to ship our first product in the fourth quarter of this year, and we're very excited about it. The market opportunity for wireless locating is about $5 billion to $10 billion. It's a red hot area in telecommunications, and it's only just emerging.'

Graham is a technology writer based in Columbia, Mo.