Combined Transmission of DOD-FAA Signal Structures from CAG

Mohan Ananda, Prem Munjal, Robert Sung and K.T. Woo

Abstract:	A system concept for Communication Satellite Augmented GPS (CAG) was previously proposed and studies are underway to evaluate the feasibility of modifying the Defense Satellite Communications System to incorporate the CAG space segment payload. This paper presents two schemes by which combined transmission of both Department of Defense (DOD) and Federal Aviation Administration (FAA) signal structures can be achieved simultaneously. The DOD signal will be backward-compatible with the 50- bps navigation message. In addition, the DOD signal will also contain a 50-bps integrity message primarily for Precise Positioning Service (PPS) users. A brief description of its preliminary format is included. The FAA signal uses a 2.50-bps data rate to provide Wide Area Differential GPS (WADGPS) data. The first scheme involves the C/A code modulation with the 50- bps navigation message on the inphase channel of the Ll carrier and the P(Y) code is modulated with the 50- bps navigation message on the quadrature-phase channel of the Ll carrier. In addition, the P(Y) code is modulated with the 50-bps navigation message on the inphase channel of the L2 carrier and a different P(Y) code is modulated with the 50-bps DOD integrity message on the quadrature-phase channel of the L2 carrier. The FAA data at 250 bps is transmitted utilizing an Ll subcarrier at 1.023 MHz by modulating on a different C/A code to minimize interference with the primary C/A code. The second scheme involves the C/A code modulation with the 50-bps navigation message on the inphase channel of the Ll carrier and the P(Y) code is modulated with the 50-bps navigation message on the quadrature-phase channel of the Ll carrier. In addition, the FAA data at 250 bps shall be transmitted by modulating on a different C/A code on the quadrature-phase channel of the Ll carrier. The L2 carrier would be identical to the first scheme.
Published in:	Proceedings of the 1994 National Technical Meeting of The Institute of Navigation January 24 - 26, 1994 Catamaran Resort Hotel San Diego, CA
Pages:	251 - 260
Cite this article:	Ananda, Mohan, Munjal, Prem, Sung, Robert, Woo, K.T., "Combined Transmission of DOD-FAA Signal Structures from CAG," Proceedings of the 1994 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 1994, pp. 251-260.
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