GPS Receiver Application Module (GRAM) Open System Architecture (OSA) for Next-Generation DOD GPS Receivers

Eddy Emile, Steven L. Saks

Abstract:	An Open System Architecture (OSA) consists of 4 well defined, non-proprietary components: (1) precise technical detinitions, (2) functional specifications. (3) performance metrics, and (4) Interface Control Drawings (ICDs). A successful OSA contains information suficient such that anyone can: (a) design and build the desired item, and (b) that anyone can integrate and test the desired item. Additionally, a good OSA is also accompanied with a non-proprietary test plan for item OSA compliance verification. The GPS Receiver Application Module (GRAM) OSA is the basis of a GPS Joint Program Office (JPO) Initiative for the next-generation of U.S. Department of Defense (DOD) GPS receivers. The GRAM OSA defines GPS receiver cards suitable for embedding in military Line Replaceable Units (LRUs, i.e. boxes). The GRAM Guidelines (GG) is a specification-like document that provides precise GPS system and receiver technical definitions, receiver functional requirements, and receiver performance metrics. The GG invokes ICD-GPS-155 that defines the GRAM interfaces. The DOD has generated and published a Common GRAM Test Plan. The GG, the ICDs, and the Test Plan are all non-proprietary documents available to any GPS receiver suoplier or integrator. Hence, the GRAM is an OSA for embedded military GPS receiver modules. The GRAM OSA may be extended to commercial, non-military receiver designs by simply removing COMSEC requirements from commercial variants. This paper describes the GRAM Initiative in broad terms. It lays out the rationale behind the decision to go with an OSA for the next-generation of military GPS receivers for avionics applications and the operational/logistics benefits that will be accrued. The current status of the JPO GRAM initiative is discussed along with the plans for migrating from today’s dedicated LRU GPS receivers to tomorrow’s embedded GRAMs. The GRAM OSA is important to the DOD because it will ensure commonalty, standardization, interoperability, and interchangeablility among military GPS receiver cards. The GRAM OSA is important to industry because it will promote competition by empowering all suppliers with the requirements needed to produce a compliant (and sellable) unit. The GRAM OSA is important to aviation because it may provide a "dual use" pathway for military and civilian use of a common card.
Published in:	Proceedings of the 1998 National Technical Meeting of The Institute of Navigation January 21 - 23, 1998 Westin Long Beach Hotel Long Beach, CA
Pages:	297 - 307
Cite this article:	Emile, Eddy, Saks, Steven L., "GPS Receiver Application Module (GRAM) Open System Architecture (OSA) for Next-Generation DOD GPS Receivers," Proceedings of the 1998 National Technical Meeting of The Institute of Navigation, Long Beach, CA, January 1998, pp. 297-307.
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