M-Code Receiver Testing: The Time is Now

M-Code – it is here. Public Law 111-383, Section 913 requires all military GPS user equipment purchased after FY 2017 to be M-Code capable, unless a waiver is issued the Secretary of Defense.

One reason for the Secretary of Defense to issue this waiver has been the unavailability of M-Code user equipment. With Military GPS User Equipment (MGUE), or M-Code receivers, becoming available to vendors, now is the time to start getting serious about integration and performance testing of MGUE and systems that rely on it.

Currently there are two GPS security architectures – and both are available only to authorized users. The first, Selective Availability Anti-Spoofing Module (SAASM), has been required for all newly fielded DoD GPS systems as of October 2006. It uses the GPS Precise Position Service, which is provided using encrypted signals (P(Y) Code) on two frequencies – L1 (1575.42MHz) and L2(1227.6MHz).

MGUE is the second one, utilizing the M-Code signals. As one aspect of the GPS modernization program, M-Code is also an encrypted signal provided on L1 and L2 frequencies.

M-Code offers several operational benefits over the previous P(Y) code signals.

  • Jamming Resistance – Using spot beams from the GPS III satellites, M-Code will be delivered to specific regions through a high gain antenna, improving the power level available to the receivers on the ground within those regions.
  • Blue Force Electronic Attack Compatibility – Due to the modulation type of the M-Code signal, it is possible to purposely jam the commercial GPS L1 C/A signal while continuing to receive and use the M-Code signal. M-Code can also be acquired without the use of C/A code, so there is no reliance on non-military signals.
  • Anti-Spoof – Not only is the M-Code signal encrypted, MGUE is also be able to detect and reject false signals.

M-Code includes new cryptography: Modernized Navstar Security Algorithm (MNSA), to ensure the system is secure. The key management has been designed to make the system easier to use and manage by the end users. M-Code is currently being transmitted on 19 satellites today, and MGUE is available from several providers, so let’s get started!

As mentioned, the M-Code signal is encrypted using MNSA. As you can imagine, the encrypted details are kept very restricted and are not available to most people. Because of this, other test methods are necessary to allow military and contractors to integrate the MGUE without having to access the MNSA information.

M-Code Testing Methods:

  • AES M-Code. Rather than using the MNSA encryption, it is possible to use a known AES encryption method for testing purposes only. This method is useful to test integration, performance and specific user scenarios in an unclassified setting.
  • M-Code SDS. Simulator Data Sets are signals created with MNSA for replay in authorized simulators. The simulator vendor does not need to know the MNSA methods to incorporate the SDS into their simulators. This method is useful for testing the security algorithms and is a replay of already created data, so no user inputs are specified.
  • MNSA M-Code. Full testing of both the performance and the security features of the MGUE are possible. The user has full control over scenario settings with the real encryption used on the M-Code signal. This method is developed by simulator manufacturers with cooperation of the GPS Wing. It is only available to authorized users.

BroadSim Defense has the configurations you need to start MGUE test and integration – right out of the box.

BroadSim Defense is unique in that it takes advantage of state-of-the-art RF commercial off-the-shelf (COTS) hardware during processing and generates signal data using COTS graphics-processing units (GPU). It is revolutionizing the GNSS industry because of its extraordinary flexibility, low cost and ability to achieve rapid development cycles.

For more information see the BroadSim Defense datasheet, visit the BroadSim Defense web page, or get a quote.

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Lisa Perdue
Lisa Perdue

Lisa Perdue is a world-leading expert in testing critical GPS and GNSS systems. She has trained hundreds of engineers and technicians who are responsible for high-reliability positioning, navigation and timing (PNT) applications. She took a lead role in the development of the first GNSS Vulnerability Test System and speaks widely on the topic at many industry conferences. Lisa Perdue is currently the Simulation Product Line Director at Orolia, directing the organization's GNSS simulation activities and contributing to its entire portfolio of resilient PNT solutions. She has more than 15 years of navigation and RF systems experience, which includes 10 years of service with the U.S. Navy, where she was a certified master training specialist.