The Maritime Gateway provides a prototype implementation of the functionality required for maritime ship-to-shore and maritime rear link communications over existing HF radios, using modern, high performance, COTS equipment. Based on the MG subnetwork protocol design, STANAG-5066 has been drafted by NC3A to specify a profile for High Frequency Radio Data Communications (Figure 1). Prototype implementations of the STANAG have been tested to validate the completeness and correctness of the STANAG, and as demonstrations of the capabilities of the open standard, which has been adopted by for Broadcast and Ship-Shore (BRASS) operations in NATO.

STANAG 5066 describes the technical and interoperability requirements for several sublayers in an HF subnetwork, including the following:

• a subnetwork-interface sublayer (SIS),
• a channel-access sublayer (CAS)
• a data-transfer sublayer (DTS)
• a subnetwork management sublayer (SMS).

In addition to these mandatory sublayer definitions, STANAG 5066 defines recommended and advisory support for the subnetwork profiles with standard modem and radio equipment, based on the use of STANAG 4285, MIL-STD-188-110A, and STANAG 4529. In addition, the STANAG supports evolutionary growth to include high-speed serial-tone waveforms at rates as high as 9600 bits per second. The protocol profile includes definition of the subnet interface layer requirements for standard application clients (but not of the clients themselves) for reliable message transfer, Z-modem applications, an HF Simple Mail Transfer Protocol (HF-SMTP), and HF-POP (Post-Office-Protocol) Mail, to name a few.

The protocol profile defined in STANAG 5066 provides a common air interface and open systems specification for the following data services over arbitrary HF channels:

• reliable point-to-point data transfer using an automatic repeat request (ARQ) protocol;
• unreliable (or non-ARQ) point-to-point, broadcast, or multicast (i.e., group broadcast) data transfer;
• regular data services using ARQ and non-ARQ delivery modes;
• expedited data services using ARQ and non-ARQ delivery modes;
• link establishment and teardown services for simple channel access;
• management services for automatic data rate change (DRC) protocols.



Two implementations of the STANAG 5066 protocol stack have been developed, one by GEC-Marconi, Chelmsford, UK, with support from NC3A, and the other by Rockwell-Collins France, with support by DERA, UK. Both implementations have been produced with substantial vendor financial input, indicating the long-term interest and support for an open protocol for reliable HF data communications. These implementations have been tested in a variety of environments at various data rates from 300 b/s to 2400 b/s by NC3A and DERA including the following:

• error-free back-to-back channels on the bench;

• simulated HF channels;

• near-vertical incidence (NVI) skywave channels;

• shipboard environments.

• Interoperability tests and additional verification and validation tests for STANAG 5066 are ongoing.


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