A Silicon Valley company specializing in location and timing tools that use a combination of GPS and TV signal detection says it can sense TV signals as weak as -128 dBm, well below the -114 dBm threshold suggested by other companies that want to operate devices in the white spaces between DTV channels.
Rosum announced a deal Oct. 4 with Intel, a member of the White Space Coalition, licensing some of its technology to the chipmaking giant. This will lead to the inclusion of location technology in mobile computing devices that will contain TV tuners, said Todd Young, director of product and business development at Rosum. That could enable applications from location-specific search and advertising to security features—allowing only computers actually at the Pentagon to view a certain file, for example, Young said.
Rosum was started by original architects of the GPS system to extend location and timing into indoor and urban areas, where GPS signals are often too weak to detect.
In its location systems, Rosum deploys stationary, regional monitor units (RMU), equipped with off-the-shelf TV receivers and GPS antennas, to measure the timing of TV broadcasts and provide this information to a Rosum location and timing server (RLTS), according to the company’s FCC filing. The mobile device in question (so far, only test models exist) receives aiding data from the RLTS and makes its own timing measurements and sends them to the RTLS, which computes location.
The aiding data provided by the RMUs allow Rosum-enabled receivers to detect TV signals down to -128dBm. According to Young, the company has been hard at work since its founding in 2000 on utilizing TV signals as-is for location and timing applications indoors and in urban areas where GPS fails, and can even utilize signals far weaker than those required for demodulation. The company realized that extending its techniques, some seven years in development, to the white space detection challenge was a natural fit.
In its rollout on the corridor from Northern Virginia to New Hampshire, an area with about 50 million people, the company uses 15 RMUs. In its filing with the FCC, Rosum showed how in the San Francisco Bay Area, a single RMU, located in Redwood City, could provide coverage from lower San Francisco and Berkeley down to San Jose, a distance of about 70 km. In all, Rosum has 29 RMUs covering about 20 percent of the U.S. population.
Rosum says the technology can detect signals—and changes in signals, in real time—without the use of geolocation databases (or, as Rosum puts it, “pre-defined channel lookup tables.”) Rosum said it considers its methods complementary to the “geolocation and sensing” regime proposed by Motorola.
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