| CPC G01S 19/34 (2013.01) [G01S 19/254 (2013.01); G01S 19/256 (2013.01); G01S 19/258 (2013.01); G01S 19/36 (2013.01)] | 19 Claims |
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1. A method to be carried out in a remote receiver for positioning based on detecting a signal from a satellite, the signal embedding known ephemeris data, comprising:
receiving from an external source a variation of the known ephemeris data over a low-power, long range wireless network, wherein the external source derives the variation of the known ephemeris data by fitting variations of expected doppler values to a polynomial function;
receiving the signal from the satellite;
computing, for each of a plurality of delay values and each of a plurality of estimated doppler values, a correlation value between the received signal and a replica of the signal delayed by the delay value and offset in frequency by the estimated doppler value, the estimated doppler value being estimated at least in part from the variation of the known ephemeris data received;
from the correlation values, selecting a first group of non-zero correlation values and a second group of non-zero correlation values, wherein the non-zero correlation values in the first group are increasing with increasing delay values, and wherein the non-zero correlation values in the second group are decreasing with increasing delay values; and
estimating a delay value based on extrapolation from the first and the second groups of non-zero correlation values.
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