Method and apparatus for processing satellite signals at a satellite positioning system receiver
Method and apparatus for processing satellite signals in an SPS receiver is described. In one example, the satellite signals are correlated against pseudorandom reference codes to produce correlation results. A determination is made whether the SPS receiver is in a motion condition or a stationary condition. The correlation results are coherently integrated in accordance with a coherent integration period. The coherent integration period is a value that depends upon the motion condition of the SPS receiver.
1. A method of processing satellite signals in a satellite positioning system (SPS) receiver, comprising:
correlating the satellite signals against pseudorandom reference codes to produce correlation results;
detecting whether the SPS receiver is in a motion condition or a stationary condition; and
coherently integrating the correlation results in accordance with a coherent integration period, where a value of the coherent integration period depends on the movement of the SPS receiver.
2. The method of claim 1 wherein the coherent integration period being a first value if the SPS receiver is in the stationary condition, or a second value if the SPS receiver is in the motion condition, the second value being less than the first value.
3. The method of claim 1 , wherein the detecting step comprises:
monitoring information received from a wireless communication network at the SPS receiver.
4. The method of claim 3 , wherein the information comprises a plurality of timing advance values obtained at a respective plurality of times.
5. The method of claim 4 , wherein the monitoring step comprises:
computing a difference between a maximum of the plurality of timing advance values and a minimum of the plurality of timing advance values;
where the stationary condition is detected in response to the difference having an absolute value of less than a certain amount, and the motion condition is detected in response to the difference having an absolute value being greater than the certain amount.
6. The method of claim 1 , wherein the detecting step comprises:
monitoring information generated by a motion measurement device.
7. The method of claim 1 , wherein the satellite signals are global positioning system (GPS) signals, and wherein the first value of the coherent integration period is greater than an epoch of a pseudorandom code.
8. The method of claim 7 , wherein the second value of the coherent integration period is less than the epoch of the pseudorandom code.
9. The method of claim 1 , wherein the second value is selected from a plurality of values based on a magnitude of the motion condition.
10. Apparatus for processing satellite signals in a satellite positioning system (SPS) receiver, comprising:
a correlator for correlating the satellite signals against pseudorandom reference codes to produce correlation results;
a motion detection module for detecting whether the SPS receiver is in a motion condition or a stationary condition;
integration circuits for coherently integrating the correlation results in accordance with a coherent integration period; and
control logic for setting the coherent integration period to a value that depends on the movement of the SPS receiver.
11. The apparatus of claim 10 wherein the coherent integration period value comprises:
a first value if the SPS receiver is in the stationary condition, or a second value if the SPS receiver is in the motion condition, the second value being less than the first value.
12. The apparatus of claim 10 , further comprising:
a wireless transceiver for receiving a wireless signal from a wireless communication network;
wherein the motion detection module is configured to monitor information in the wireless signal.
13. The apparatus of claim 11 , wherein the information comprises a plurality of timing advance values obtained at a respective plurality of times.
14. The apparatus of claim 11 , wherein the motion detection module is configured to compute a difference between a maximum of the plurality of timing advance values and a minimum of the plurality of timing advance values, where the stationary condition is detected in response to the difference having an absolute value of less than a certain amount, and the motion condition is detected in response to the difference having an absolute value being greater than the certain amount.
15. The apparatus of claim 10 , wherein the motion detection module comprises a motion measurement device.
16. The apparatus of claim 11 , wherein the satellite signals are global positioning system (GPS) signals, and wherein the first value of the coherent integration period is greater than an epoch of a pseudorandom code.
17. The apparatus of claim 16 , wherein the second value of the coherent integration period is less than the epoch of the pseudorandom code.
18. The apparatus of claim 11 , wherein the control logic selects the second value from a plurality of values based on a magnitude of the motion condition.