ION Technical Content
Self-Aiding in GPS Signal Tracking
| Abstract: | In the GPS C/A signal tracking process, the longest coherent integration time is 20 milliseconds that are limited by the 50 Hz navigation data on top of the base band CDMA signal. To improve the sensitivity for weak signal tracking, such as indoor applications, external aiding is a good option. The aiding resources can be, for example, from a local mobile network. With the aiding of the binary navigation data sequence, the integration time for the tracking loop can be extended for a better tracking performance. But in the cases when the external aiding is not available, the navigation data can be estimated at the same time when the tracking process is going on. The estimated binary data can be then used in a feedback scheme for the self-aiding to extend the coherent integration time of the tracking loop. In this report, some feedback principles are discussed for the GPS signal tracking. It ranges from a simple hard binary estimation feedback and a softer decision feedback based on the signal quality, or the likelihood of the signal power level. The experiment results show that the self-aiding can improve the tracking behavior. The improvement can be as high as +5 dB. The premises are that the satellite signal acquisition has been set up and the data bit synchronization has been achieved. So, the method cannot be used alone in a deep low signal level environment at the beginning. But the improvement of the tracking performance gives a better pseudo range measurement in a normal situation. The tracking process is getting more stable in most of the cases when the coherent integration time increases. On the other hand, the scheme can be applied when a GPS receiver is moving, for example, from outdoor to indoor or from highway to tunnel. The already tracked signal can be continually tracked in a deeper low signal level environment. The sensitivity of the receiver is somehow improved. The technique is quite simple for the implementation in practice. |
| 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: | 506 - 509 |
| Cite this article: | Zhengdi, Qin, "Self-Aiding in GPS Signal Tracking," Proceedings of the 15th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2002), Portland, OR, September 2002, pp. 506-509. |
| Full Paper: |
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