Robust Open Service GNSS Receivers for Military Applications

G.A. McGraw, B. Disselkoen, G. Buesnel

Abstract:	There is increasing use of Standard Positioning Service/Open Service (SPS/OS) Global Navigation Satellite System (GNSS) receivers, which utilize unencrypted signals, for military applications. While the use of SPS receivers for many non-combat functions is not controversial, the lack of strong signal authentication, as found in Selective Availability Anti-Spoofing Module (SAASM) receivers, is problematic with the increasing proliferation of jamming and spoofing threats. There are several motivations for use of SPS/OS GNSS receivers in military applications, including: • The Size, Weight, and Power (SWAP) and non-intuitive user interfaces of standard-issue devices has led to the proliferation of consumer-grade GPS in ground combat use; • Key distribution and management, and the accountability of SAASM receivers, even when unkeyed, leads to significant logistics issues; • Foreign military sales bottlenecks, even for nations approved for SAASM; • Precision applications that require functionality like Real Time Kinematic (RTK) that until recently were not found in SAASM receivers; • Nations are increasingly interested in asserting varying degrees of sovereign control over the design and manufacture of GNSS receivers, for example to ensure that no malware has been introduced. Some of these issues have been addressed by the latest generation of SAASM engines that are capable of supporting high accuracy and have SWAP comparable to consumer devices, but the military community (both US and non-US) needs to accept that there is a role for SPS/OS receivers. The key challenge is to accomplish this in a manner that provides the warfighter the proper degree of positioning, navigation, and timing (PNT) assurance at an affordable cost. Broadly speaking, there are four main classes of receivers in military use today: • Protected Service. This includes SAASM today, and will evolve to include M-code, PRS, and possibly other encrypted signal receivers in the future. • Consumer-grade SPS. Examples include handheld units used by dismounted warfighters, including GPS engines embedded in personal electronic devices. • Survey-grade SPS. These include dual frequency units, with semi-codeless access to GPS L2 and increasingly other GNSS frequencies and signals. • Certified aviation SPS. These are L1 GPS and SBAS receivers that meet international standards, including design assurance, such as DO-178, DO-254, etc. In the future, these receivers will migrate to L1/L5 (E1/E5). The use of survey-grade receivers for applications such as Unmanned Aircraft System (UAS) navigation and targeting systems has received increased scrutiny, as lack of PNT assurance in these applications can lead to loss of life and compromise national security. The availability of SAASM receivers that can completely fulfill these functions is a case for discontinuing waivers. Similarly the use of consumer-grade receivers in tactical situations, particularly when calling for fire, is obviously of concern. There is a need for a new category of receiver capability that acknowledges the practical limitations to the adoption of Protected Service receivers, but addresses the issues associated with the use of SPS receivers in military operations. We are calling this class “Robust Open Service” (ROS) which we propose should include the following characteristics: • Receiver Autonomous Signal Authentication. Processing in the receiver system to detect and isolate spoofers and jammers, including use of multiple frequencies and constellations, inertial and clock aiding, and Receiver Autonomous Integrity Monitoring (RAIM) PNT processing can be used to ensure the reliability of the position solution, even without encrypted signals. Initial performance results will be presented for this capability. • Design Assurance. Similar to the hardware and software verification processes followed in civil aviation receivers, standards for design, production, and testing are needed. This process also provides a means for nations to assert some level of sovereign control. • Compatibility with military-unique interfaces, including anti-jam equipment. • Mechanisms to enable compatibility with encrypted receivers, either from the perspective of swapping ROS and Protected receivers in platform integrations, or else as dual-thread integrations that permit hybrid operation. The ROS receiver class fills an important gap in the military user space, in one sense representing a merging of the aviation and survey-grade categories, but also having the potential to fulfill the functions covered by consumer-grade units often used by individual soldiers. By offering a simplified logistics chain because of the use of OS signals and providing enhanced PNT assurance over commercial units, there is a potential for a “win-win” situation for both individual users and command and procurement authorities. When integrated with Protected Service devices, the ROS category also represents a stepping stone for receivers that support multiple independent levels of security, with a mixture of encrypted and open signals. To promote the proliferation of these enhanced capabilities, it is important that industry-wide standards become adopted.
Published in:	Proceedings of the 26th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2013) September 16 - 20, 2013 Nashville Convention Center, Nashville, Tennessee Nashville, TN
Pages:	2533 - 2541
Cite this article:	McGraw, G.A., Disselkoen, B., Buesnel, G., "Robust Open Service GNSS Receivers for Military Applications," Proceedings of the 26th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2013), Nashville, TN, September 2013, pp. 2533-2541.
Full Paper:	ION Members/Non-Members: 1 Download Credit Sign In