Patent ID: 8649755

Claim:
A method comprising, with a device operable in a plurality of selectable power modes: setting a timing circuit based, at least in part, on a phase value obtained from a signal acquired from a ground-based transmitter, wherein said signal comprises a pilot signal and said phase value is determined based, at least in part, on one or more time phase measurements of said pilot signal; and transitioning operation of said device to a lower power mode, wherein at least a portion of a receiver used to acquire said signal is disabled and at least a portion of enabled device circuitry uses said timing circuit, based, at least in part, on at least one of: a determination that a profile test indicating that said device is within a characterized environment is satisfied, at least in part, by said phase value; or a determination based, at least in part, on said phase value, that said device is in a constrained motion state.