The broadcast TV infrastructure is built and operational today. In the United States, he broadcast TV infrastructure is distributed, robust, and comprises 2800 transmitters that are highly correlated with population density and broadband penetration. TV signals are plentiful, powerful, low and diverse in frequency, and easily penetrate walls, automobiles, and city buildings. Conversely, satellite-based systems were designed for outdoor applications, and are most challenged in the population centers where TV is strongest.

In sum, Rosum transforms the commercial TV infrastructure into a high-power, multi-frequency terrestrial GPS that is already deployed where people live and work today.



Further, TV transmitters are distributed, supplied with backup power at the studio and hilltop, and are highly robust to disaster. TV provides the backbone to the Emergency Alert System. The National Association of Broadcasters received presidential commendation following broadcasters' efforts to keep broadcasts on the air in the wake of Hurricane Katrina. TV is not best-effort infrastructure; TV is must-work infrastructure.

New broadcast standards targeting mobile receivers, such as DVB-H, DVB-SH, T-DMB, MediaFLO, and 1-segment ISDB are leading to deployment of new broadcast networks, and a new platform of devices capable of viewing mobile TV. Informa Research estimates that 160M TV-capable mobile devices will be shipped annually by 2010.

TV's Advantages

Rosum enjoys fundamental advantages over GPS and A-GPS. These advantages are based in the laws of physics, and their combined effect is compelling.

Power

Rosum TV-GPS enjoys a substantial power advantage over GPS signals. Terrestrial TV broadcast signals are typically 1 megawatt effective radiated power (ERP), compared to 500 watts ERP for GPS satellite signals. In typical metropolitan environments, TV towers are tens of miles from the user device to be positioned. The result is that the synch codes in the TV signal (which Rosum uses to track the signals) are approximately 40dB (ten thousand times) stronger than GPS signals.

For positioning, Rosum does not require that a TV signal be strong enough to be viewed on a TV set. 50dB of processing gain allow us to use even weak TV signals for location.

Frequency

GPS signals are transmitted at a frequency (1.575 GHz) which is strongly attenuated by buildings and other man-made structures. TV signals, in comparison, are broadcast at much lower frequencies (50-700 MHz). At these frequencies, signals are able to achieve building penetration for in-building TV viewing and Rosum positioning.

Frequency Diversity

Since each TV tower typically broadcasts more than one channel, the Rosum receiver will have a better chance of acquiring a signal given that these channels are broadcast at different frequencies. Rosum can choose the best channels from each tower to compute the user's location.

Bandwidth

In general, the wider the bandwidth of the signal, the more accurately one can resolve multipath, or the reflected signals that characterize urban and indoor environments. The bandwidth of broadcast television ranges from 6 MHz to 8MHz depending on the standard. In contrast, the bandwidth of the GPS satellite signal is 1MHz. This provides roughly a 6:1 bandwidth advantage, and a 6:1 advantage in the mitigation of signal multipath.