Coherent Processing Techniques for YMCA++ Receivers in Different Environments

N. Bhatia, A. Jovancevic, A. Brown, S. Ganguly

Abstract:	The next generation of GPS receivers will be able to receive navigation signals on the L1 and L2 frequencies including M code on L1 and L2 and L2C on L2. All of these codes are generated from the same clock in a given satellite. The availability of these signals coherently generated at the satellite allows for coherent processing at the receiver. A YMCA++ receiver can utilize this coherence and provide coherent combining of these signals, resulting in improved performance. Unlike the conventional tracking receiver, where a different set of correlator, tracking loops and replica generator are used for each code, in YMCA coherent processing a single set can be used to perform the entire task of tracking different codes. This paper describes the algorithms developed and results obtained in the development of such a YMCA++ receiver. The YMCA receiver using composite codes is shown to provide a significant performance advantage over the conventional tracking architectures. It coherently combines the power of all the three codes (P(Y), M and C/A codes) resulting in the improved SNR and better immunity to adverse signal conditions including varying C/No, various types of jammers and multipath. A significant improvement in SNR and A/J performance was observed using this receiver architecture. The FFT based block correlation developed for the receiver allows a high-resolution multiple correlator structure to be implemented efficiently which can be used to do high-speed parallel Doppler and Multipath search. The YMCA coherent processing architecture can be implemented either using a single composite correlator or separate correlators for each code along with a single coherent replica generator. Consequently, it results in reducing the overall computational burden by using a single set of tracking loops and replica generator. The receiver is implemented using reconfigurable software radio based architecture. The software approach offers flexibility in designing and testing new concepts and algorithms. Center for Remote Sensing, Inc. has developed a software receiver development platform which allows simulation of a variety of architectures, configuration and scenarios. The tested simulation can then be easily ported onto programmable processors to implement a real-time prototype. The paper compares different coherent processing techniques and provides a comprehensive set of metrics illustrating the enhanced benefit of using a YMCA++ receiver. The results obtained from the exhaustive performance analysis of the receiver under various extreme conditions demonstrate the advantages of a coherent processing architecture over conventional processing
Published in:	Proceedings of the 19th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2006) September 26 - 29, 2006 Fort Worth Convention Center Fort Worth, TX
Pages:	1866 - 1877
Cite this article:	Bhatia, N., Jovancevic, A., Brown, A., Ganguly, S., "Coherent Processing Techniques for YMCA++ Receivers in Different Environments," Proceedings of the 19th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2006), Fort Worth, TX, September 2006, pp. 1866-1877.
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