We’ve been hearing about the blooming of location-based cellular services for years now, though not many successful business models have emerged. Most location-based technologies are primarily designed to meet Federal Communication Commission requirements to implement the E911 system, which lets emergency services locate cell phones that call 911. The ability to meet those regulations took far longer than anyone imagined, but those systems are mostly in place now and functioning. But there’s always room for improvement, and that’s where the Andrews Solutions division of CommScope comes in. Its Multiple Range Estimation Location (MREL) system is an improvement over most existing technologies for specific applications.

Article Tools

• 

Current Location Technology

There are two common techniques for locating cell phones: GPS and uplink time difference of arrival (U-TDOA). GPS systems are handset-based, as GPS satellites can “see” a GPS receiver chip installed in the phone. The GPS information from the satellites is used to compute the location of the phone and communicate it back to the carrier. U-TDOA uses various network time measurements between three basestations to determine location.

There are at least eight other different network-based technologies. They all use location measurement units (LMUs), which are basestation components comprising both hardware and software. LMUs are installed at selected basestations to measure certain signal characteristics from the existing access network infrastructure (basestation, antennas, cables, etc.) to identify the location of the mobile phone user.

The characteristics they use to identify a location generally include the time difference between when a certain part of the cell call arrived at different local cell towers, the angle of arrival for the cellular signal, or some other trait of the cellular signal that will help estimate a location. It’s a complicated process that involves different methods of trying to estimate exactly where the caller is. The government requires operators to be able to estimate a location within a certain degree of accuracy, generally within 50 to 150 m.

The various network-based location technologies differ in how they determine the location. The MREL system uses LMUs to exploit features in the newer digital signaling protocols to produce location results in areas U-TDOA cannot. MREL makes innovative use of the feedback loop that exists between a mobile and a basestation to determine the actual time that the handset transmits a signal of interest. It then uses the transmission time and the time of arrival of the signal at a sensor site to determine a circular range ring, where the handset could be located, around each sensor site. The location is then estimated by the best intersection of the multiple range-rings.

Generally, most location technologies can meet E911 requirements in some way. Using a variety of techniques in the same network, though, yields higher accuracy. And outside of E911 purposes, location technologies are increasingly being used for commercial purposes. There are so many different technologies because they each have different levels of accuracy and work better in different environments.

For example, GPS is pretty accurate except in buildings or other areas where the satellite signal has difficulty seeing the phone. Some carriers use Assisted-GPS to help locate a cell phone indoors or in some other satellite-compromised viewing location. But because GPS is handset-based, operators can’t maximize the potential commercial revenues that come from offering network-based location services. Most network-based location technologies work better in buildings, or like MREL, in rural areas. So basically, wireless operators have a host of technologies to choose from to meet government requirements as well as enable the kind of location technology that has the potential to be profitable in other commercial applications.

MREL is part of Andrews’ GeoLocation Enabled Network solutions (GeoLENs) portfolio of products for the Location Enabled Network. The portfolio includes the Mobile Location Center (MLC) platform supporting control plane 3GPP network functionality and a wide range of network-based, Assisted-GPS, and hybrid positioning technologies, including the complementary GeoLENs LMU products supporting the latest generation of MREL technology. The MLC continues to evolve to support LTE E-SMLC functionality as standards definitions become finalized, and it continues to support concurrent OMA SUPL user-plane capability in a fully integrated single-bay delivery platform.