Interpolation of channel search results
In general, the invention facilitates searching for energy peaks in spread spectrum wireless communication systems with greater precision. More particularly, various embodiments of the invention may involve reporting not only an energy peak and its associated offset, but also the energy levels corresponding to one or more offsets occurring before and after the offset at which the energy peak occurs. Interpolation or extrapolation techniques may be used to predict the actual location of an energy peak based on the apparent location of the peak and the energy levels observed at surrounding offsets.
1. A computer readable medium encoded with computer executable instructions for:
identifying a peak energy level and at least one shoulder energy level with a first time resolution for a spread spectrum signal;
receiving the peak energy level and, when a mode of operation is enabled, the at least one shoulder energy level;
configuring a demodulator as a function of the peak energy level and the at least one shoulder energy level when the mode of operation is enabled, and
configuring the demodulator without the at least one shoulder energy level when the mode of operation is disabled, wherein the demodulator operates at a second time resolution that is more fine than the first time resolution.
2. The computer readable medium of claim 1 , further encoded with computer executable instructions for
calculating an offset of an energy peak based on the peak energy level, an offset corresponding to the peak energy level, and the at least one shoulder energy level.
3. The computer readable medium of claim 2 , further encoded with computer executable instructions for
calculating the offset of the energy peak using at least one of an interpolation technique and an extrapolation technique.
4. The computer readable medium of claim 1 , further encoded with computer executable instructions for:
defining a search window comprising a set of offsets for a pseudorandom noise (PN) sequence; and
for each offset in the search window, applying a corresponding spreading code to the spread spectrum signal.
5. The computer readable medium of claim 1 , further encoded with computer executable instructions for
identifying a plurality of additional peak energy levels for the spread spectrum signal and respective shoulder energy levels for at least one of the additional peak energy levels.
6. The computer readable medium of claim 1 , wherein the spread spectrum signal comprises one of a continuous pilot signal, a discontinuous pilot signal, and a beam-formed pilot signal.
7. A computer readable medium encoded with computer executable instructions for:
defining a search window comprising a set of offsets for a pseudorandom noise (PN) sequence, wherein the set of offsets is at a first time resolution that is more coarse than a second time resolution of a demodulator used to demodulate a received CDMA signal;
for each offset, applying a corresponding spreading code to the received CDMA signal to obtain a signal energy level;
identifying a peak offset for which the obtained signal energy level is greatest, wherein the peak offset has the first time resolution;
deciding whether to enable a shoulder mode;
when the shoulder mode is enabled, reporting a first shoulder energy level corresponding to an offset preceding the peak offset and a second shoulder energy level corresponding to an offset following the peak offset; and
when the shoulder mode is not enabled, refraining from reporting the first shoulder energy level.
8. The computer readable medium of claim 7 , further encoded with computer executable instructions for
calculating an offset of an energy peak using at least one of an interpolation technique and an extrapolation technique as a function of the signal energy level corresponding to the peak offset, an offset corresponding to the peak energy level, and the first and second shoulder energy levels, wherein the offset of the energy peak has the second time resolution.
9. The computer readable medium of claim 8 , further encoded with computer executable instructions for
demodulating the received CDMA signal using a spreading code corresponding to the calculated offset.
10. The computer readable medium of claim 8 , further encoded with computer executable instructions for
determining a position as a function of the calculated offset.
11. The computer readable medium of claim 7 , further encoded with computer executable instructions for
identifying at least one additional shoulder energy level.
12. The computer readable medium of claim 7 , wherein the received CDMA signal comprises one of a continuous pilot signal, a discontinuous pilot signal, and a beam-formed pilot signal.
13. An apparatus comprising:
means for identifying a peak energy level and at least one shoulder energy level with a first time resolution for a spread spectrum signal;
means for receiving the peak energy level and, when a mode of operation is enabled, the at least one shoulder energy level;
means for configuring a demodulator as a function of the peak energy level and the at least one shoulder energy level when the mode of operation is enabled, and
means for configuring the demodulator without the at least one shoulder energy level when the mode of operation is disabled, wherein the demodulator operates at a second time resolution that is more fine than the first time resolution.
14. The apparatus of claim 13 , further comprising
means for calculating an offset of an energy peak based on the peak energy level, an offset corresponding to the peak energy level, and the at least one shoulder energy level.
15. The apparatus of claim 14 , further comprising
means for calculating the offset of the energy peak using at least one of an interpolation technique and an extrapolation technique.
16. The apparatus of claim 13 , further comprising:
means for defining a search window comprising a set of offsets for a pseudorandom noise (PN) sequence; and
means for applying a corresponding spreading code to the spread spectrum signal for each offset in the search window.
17. The apparatus of claim 13 , further comprising
means for identifying a plurality of additional peak energy levels for the spread spectrum signal and respective shoulder energy levels for at least one of the additional peak energy levels.
18. The apparatus of claim 13 , wherein the spread spectrum signal comprises one of a continuous pilot signal, a discontinuous pilot signal, and a beam-formed pilot signal.
19. An apparatus comprising:
means for defining a search window comprising a set of offsets for a pseudorandom noise (PN) sequence, wherein the set of offsets is at a first time resolution that is more coarse than a second time resolution of a demodulator used to demodulate a received CDMA signal;
means for applying a corresponding spreading code to the received CDMA signal to obtain a signal energy level for each offset;
means for identifying a peak offset for which the obtained signal energy level is greatest, wherein the peak offset has the first time resolution;
means for deciding whether to enable a shoulder mode;
means for reporting a first shoulder energy level corresponding to an offset preceding the peak offset and a second shoulder energy level corresponding to an offset following the peak offset when the shoulder mode is enabled; and
means for refraining from reporting the first shoulder energy level when the shoulder mode is not enabled.
20. The apparatus of claim 19 , further comprising
means for calculating an offset of an energy peak using at least one of an interpolation technique and an extrapolation technique as a function of the signal energy level corresponding to the peak offset, an offset corresponding to the peak energy level, and the first and second shoulder energy levels, wherein the offset of the energy peak has the second time resolution.
21. The apparatus of claim 20 , further comprising means for demodulating the received CDMA signal using a spreading code corresponding to the calculated offset.
22. The apparatus of claim 20 , further comprising
means for determining a position as a function of the calculated offset.
23. The apparatus of claim 19 , further comprising
means for identifying at least one additional shoulder energy level.
24. The apparatus of claim 19 , wherein the received CDMA signal comprises one of a continuous pilot signal, a discontinuous pilot signal, and a beam-formed pilot signal.