Study of Signal Combining Methodologies for GPS III쳌s Flexible Navigation Payload

G. H. Wang, V. S. Lin, T. Fan, K. P. Maine, P. A. Dafesh and B. Myers

Abstract:	Global Position System (GPS) Modernization on Block IIR-M added a new military signal (M-Code) and a second civil signal (L2C). On GPS IIF, a civil signal for aviation users is to be introduced on the L5 frequency. This modernization continues on GPS III with the concept of a Flexible Navigation Payload. This reprogrammable payload is envisioned to be able to modify code schemes, code rates, data rate, and navigation messages on-orbit. Importantly, the key feature of the Flexible Payload would allow for the introduction of new signals while maintaining existing signals, if necessary. Previous works have studied signal combining for the C/A, P(Y) and M-code signals. Dafesh et al proposed the Coherent Adaptive Subcarrier Modulation (CASM) scheme [1], which is mathematically equivalent to Interplex [3], and was eventually adopted for use on Block IIR-M. Spilker and Orr explored using majority vote logic for GPS modernization in [5]. This paper extends these works by including additional signals and explores different signal combining methodologies. Our study herein focuses on linear combining, Interplex/CASM, and majority vote. It will be shown that while Interplex is very efficient for the three-signal case, it exhibits higher losses when an additional signal is present and other solutions may be more optimal.
Published in:	Proceedings of the 17th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2004) September 21 - 24, 2004 Long Beach Convention Center Long Beach, CA
Pages:	2207 - 2218
Cite this article:	Wang, G. H., Lin, V. S., Fan, T., Maine, K. P., Dafesh, P. A., Myers, B., "Study of Signal Combining Methodologies for GPS III쳌s Flexible Navigation Payload," Proceedings of the 17th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2004), Long Beach, CA, September 2004, pp. 2207-2218.
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