An Efficient Weak Signal Acquisition Algorithm for a Software GPS Receiver

David M. Lin and James B.Y. Tsui

Abstract:	This paper discusses a new acquisition algorithm to process 40 ms of data regardless of the location and the number of phase transitions. The algorithm uses coherent integration. The correlation peak of this approach is in the frequency domain. If there is no phase transition, the result will be the same as the regular 40 ms coherent integration. If there are phase transitions in the 40ms data, or the Doppler frequency is off the frequency bin, or both, the spectrum of the signal spreads. However, there are several dominant spectral lines surrounding the bin of the Doppler frequency. In this approach, if the peak in frequency domain is not above the detection threshold, the components at adjacent frequency bins are subsequently non-coherently or coherently added. The results are compared against the corresponding thresholds until the signal is detected or acquisition fails. The total spectral lines used in the addition are limited to 4. The addition of adjacent bins not only adds the signal but also increases the noise level. This paper also discusses how the threshold for each noise level is developed. In order to measure the efficiency of the algorithm, 200 simulation runs were conducted to compare this new algorithm with the regular 40 ms coherent integration algorithm which doesn’t perform the subsequent additions. The simulation result shows the new algorithm can process data with C/No =30dB with 90% probability of detection. The sensitivity of this approach is 2 dB better than the regular 40 ms coherent integration algorithm.
Published in:	Proceedings of the 14th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2001) September 11 - 14, 2001 Salt Palace Convention Center Salt Lake City, UT
Pages:	115 - 136
Cite this article:	Lin, David M., Tsui, James B.Y., "An Efficient Weak Signal Acquisition Algorithm for a Software GPS Receiver," Proceedings of the 14th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2001), Salt Lake City, UT, September 2001, pp. 115-136.
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