Very Efficient High Sensitivity Fully Coherent AGPS Signal Processing with Almost No Assistance Requirements

B. Shayevits, H. Cohen, J. Nir and E. Dochovny

Abstract:	There is clear evidence that Assisted-GPS (AGPS) solutions are becoming popular for embedding into handsets, cellular PDA's and tracking devices. AGPS systems take advantage of aiding data provided by the cellular network which result in reduced time to first fix, increased sensitivity, reduced processing time and power consumption. CellGuide has developed a Software-Based AGPS solution with enhanced sensitivity, using off-the-shelf DSP/RISC processors to run the GPS software. A Fully coherent 2D processing of up to 2 seconds' dwells is performed. Coherent dwells may also be non- coherently integrated. Unlike similar AGPS solutions, the described algorithm requires: • Very limited assistance data • No accurate initial position (cell ID) or timing is required. • The processing is a full 2D coherent processing in range and Doppler. All 1023 phase codes in the 1 KHz range are processed in parallel.  Processing of 1-second duration of dwell, for example, will require performing a 1K complex FFT 3000 times only per satellite. For the above example of 1second dwell we get an equivalent system noise BW of 1 Hz that gives a sensitivity of -157dBm. (This assumes NF=1.5dB; processing loss=2.5dB; threshold=13dB). Other advantages of 2D coherent processing are: • Good immunity to noise/jamming and enhanced multi path rejection, which is very important in dense urban and indoor environments. Additional features of this solution are:  Very low standby power consumption (10mW) • Fast time to first fix.
Published in:	Proceedings of the 15th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2002) September 24 - 27, 2002 Oregon Convention Center Portland, OR
Pages:	231 - 240
Cite this article:	Shayevits, B., Cohen, H., Nir, J., Dochovny, E., "Very Efficient High Sensitivity Fully Coherent AGPS Signal Processing with Almost No Assistance Requirements," Proceedings of the 15th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2002), Portland, OR, September 2002, pp. 231-240.
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