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ANEP-87
Manufacturers of underwater acoustic communications equipment supplying NATO and partner navies operating submarines, surface ships and autonomous underwater vehicles
ANEP-87 defines JANUS, NATO's digital underwater acoustic signalling standard, so equipment from different manufacturers can discover each other and exchange short digital messages underwater.
ANEP-87 is the NATO Allied Naval Engineering Publication that defines JANUS, a digital underwater acoustic signalling standard built so that submarines, surface ships, buoys, sensor networks and autonomous underwater vehicles (AUVs) from different manufacturers can discover each other and exchange short digital messages underwater. Before JANUS, each manufacturer's underwater modem used its own proprietary coding scheme, so NATO and allied navies had no way to communicate digitally underwater between assets built by different suppliers, even where each already carried some digital underwater capability of its own. JANUS fixes that at the physical layer: a single acoustic waveform, a 64-bit "Baseline JANUS Packet" structure, an error-correcting code and five defined frequency bands, so that any compliant modem can at least detect and decode a JANUS transmission regardless of who built it.
JANUS uses Frequency-Hopped Binary Frequency Shift Keying (FH-BFSK), a waveform chosen for robustness in the underwater acoustic channel and ease of implementation on existing hardware. Five frequency bands are defined, each with its own centre frequency, bandwidth and chip duration; bands A, B and C are intended predominantly for military use, while bands D and E serve both military and civilian applications, and band A is not expected to become obsolete before 2030. Every transmission starts from a fixed 64-bit packet: a version number, a mobility flag, a schedule flag, transmit/receive and forwarding flags, an 8-bit class-user identifier, a 6-bit application type, a 34-bit application data block and an 8-bit CRC. The packet is protected by a rate-1/2 convolutional encoder, based on the same coding used in the commercial IS-95 CDMA cellular standard, and then interleaved. An optional "Cargo Data" extension can follow the baseline packet for larger payloads, with the channel time for it reserved in advance or requested at a fixed repeat interval, for up to nearly eleven minutes at a time.
A large part of the standard's medium access control is built around one constraint: not disrupting NATO's existing analogue underwater telephone and distress traffic, which is standardised separately. JANUS uses an energy-detection carrier-sensing scheme with exponential backoff to avoid collisions, and adds a mandatory guard time before transmitting so that pauses between spoken words on an analogue underwater telephone are never mistaken for a free channel. Where the JANUS band overlaps the underwater telephone band, a JANUS node must not transmit immediately after detecting the channel was busy. The document leaves one detail deliberately open: the specific algorithm a modem uses to estimate background acoustic noise is not fixed, and an implementation is judged only by whether its false-alarm and missed-detection behaviour stays broadly in line with other implementations.
On top of the baseline packet, the standard allocates 256 numbered "User Classes", some assigned to specific message types, most left open for future assignment or reserved for individual nations. The message types actually specified cover emergency position, status and combined reports for a vessel in distress; an automated remote-query mechanism for retrieving sensor data; underwater AIS-style contact reports covering up to eight vessels' type, position, depth, speed and heading at once; oceanographic and meteorological data requests aimed at offshore installations; text chat with optional encryption (including AES-GCM) and delivery acknowledgement; two different node-discovery "first contact" handshakes for a device joining a network; a "keep silent" emission-control message for acoustic-sensitive operations; and a symmetrically pre-shared-key messaging scheme for pre-canned, codebook-style communication. Older equipment built to the previous packet-version number keeps working under separate legacy formulas the standard still carries, so this edition's changes do not break fielded systems built to the prior version.
The standard does not speak in terms of "Supplier" and "Acquirer" the way NATO's quality-assurance publications do. It speaks in terms of the equipment and the people who build and operate it: manufacturers, who the document expects to bring existing systems into compliance mostly through firmware updates rather than a hardware redesign; and operational commanders, who choose which frequency band to use for a given mission. What brings JANUS into force is not the publication date but ratification: nations record their agreement to use ANEP-87 through STANAG 4748, and that ratification does not mean uniform or immediate rollout. Recorded reservations already show navies moving at different speeds - one nation's newest submarines and frigates carry JANUS from their in-service date, while its existing fleet is not expected to gain the capability for several more years, tied to its own industrial testing timeline rather than a single NATO-wide deadline.
ANEP-87 leaves several things to the implementer rather than specifying them: the algorithm for estimating background acoustic noise, the addressing scheme used by the basic text-chat application, and the specific encryption method behind several of its "user-defined" encryption options. It also names no certification scheme, no accredited certification body and no notified body: nothing in the document supports the idea that a product, or a company, can be "JANUS certified."
ANEP-87 is an engineering specification, not a management-system standard: the work of meeting it happens in a modem's firmware and RF hardware, on a test bench and in interoperability trials, not inside a software system. ComplyTrain does not design acoustic waveforms, write modem firmware, or run the frequency-hopping, CRC or channel-sensing conformance tests a product needs to pass - that stays specialist RF and DSP engineering work, verified by the manufacturer and by interoperability trials between navies.
What ComplyTrain does is hold the paper trail that engineering work needs: design records showing which JANUS user classes, applications and frequency bands a product implements; verification records evidencing that its packet timing, CRC and channel-sensing behaviour were checked against the standard's own tables and worked examples; training records for the engineers responsible for keeping that implementation current as editions change; and a record of which contract clause or national reservation drove a given implementation decision. None of that is a certification: nothing in ANEP-87 is certifiable, and ComplyTrain makes no claim that it is.
Which naval interoperability standards a given contract requires, and what else sits alongside ANEP-87 and STANAG 4748, is set by the contract and the customer's quality clause, not by us. See what else sits in the naval armaments family in the standards explorer, and talk to us about the evidence trail behind it.
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Yes. ANEP-87 is the NATO Allied Naval Engineering Publication that specifies JANUS, the digital underwater signalling waveform and protocol. "JANUS" is the name commonly used for the standard's technical content; ANEP-87 is the NATO publication number it is issued under.
It binds through ratification, not automatically. Nations record their agreement to use it through STANAG 4748, and several nations have registered reservations affecting when their own fleets implement it, so rollout timing depends on the ratifying nation and, for a supplier, on the contract or programme that specifies it.
STANAG 4748 is the agreement nations ratify; ANEP-87 is the Allied Publication that carries the technical specification the agreement covers. A nation implements ANEP-87 because it has agreed to STANAG 4748, not the other way round.
No. JANUS's medium access control is explicitly designed for non-disruptive coexistence with NATO's existing analogue underwater telephone and distress communications, including a mandatory guard time so JANUS transmissions do not interfere with them.
No. ANEP-87 names no accredited certification body, notified body or certification scheme. Compliance is established through the manufacturer's own engineering verification and through interoperability testing between implementations, not through a NATO-awarded certificate.
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