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Rosum 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
Every building has slightly different signal attenuation across the broadcast TV spectrum. 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 position using that signal. The bandwidth of analog and digital 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.