How does TimeLoc work?
Thursday, 1 November 2012
The complete TimeLoc process is described in detail in the Locata TimeLoc Patent (US Patent #7,616,682). Nevertheless, the following is a brief description:
TimeLoc is the mechanism used to synchronize the radio signals transmitted by LocataLites. The unique LocataLite transceiver design utilizes a receiver within the LocataLite to track both signals from an external LocataLite (let’s call it “A”) as well as the signals from its own internal transmitter broadcasting co-located signals (“B”). This sets up a measurable loop which is described in the Locata patent document and has been named a Time Lock Loop (TLL). By taking pseudorange and carrier phase measurements derived from both external received signal A and internal signal B, LocataLite B is able to move or slew its signals to align with A.
TimeLoc is fundamentally based on aligning the timing (range) of LocataLite signals to correspond to the geometric distances from the receive antenna to both external LocataLite A and LocataLite B’s co-located transmit antennas. The distances are computed from antenna locations derived when the antennas for both LocataLites are installed and surveyed into position. The known antenna positions are broadcast as “a Locata equivalent to the GPS satellite system’s ephemeris” as part of the navigation data broadcast around the LocataNet. To synchronize the co-located signals with external LocataLite A, LocataLite B slews its internal signals until the single difference range between A and B is the geometric range. This internal correction process is accurate to the millimeter level.
Locata’s TimeLoc technology is not affected by traditional synchronization problems such as RF delays in the receiver front-end, or timing delays within the receiver/transmitter hardware or components, because all of these delays are cancelled out as a natural consequence of the differencing process in the TimeLoc method. From a Locata receiver’s perspective, the two transmitters are completely synchronized. Once the ranging signals are synchronized, LocataLite B signals it has TimeLoc, sets its health bit to “healthy”, and “joins” the LocataNet. The TimeLoc method is simple, robust, and works extremely well in real world deployments, allowing synchronization at the nanosecond (or better) level.
There is no other technology in the world that can do this.