What is Link 16?

Link 16 is a secure, jam-resistant tactical data link that U.S., NATO and coalition forces use to exchange real-time tactical data, voice and situational awareness. The Navy's MIDS program office calls it a standardized system for those forces in its January 2025 program sheet. The same sheet says the office's foreign military sales division delivers Link 16 terminals to 58 nations and NATO. The National Telecommunications and Information Administration (NTIA) band summary for 960-1164 MHz, dated September 1, 2014, says the Joint Tactical Information Distribution System (JTIDS) has been operational since 1981.

JTIDS and the MIDS terminals

The NTIA summary says JTIDS and the Multifunctional Information Distribution System (MIDS) are identical at the radio frequency level and belong to a family of radio equipment that implements Link 16. Both use time division multiple access, frequency hopping and error correction to keep working in a jammed environment.

The Navy program sheet traces the terminals:

• MIDS Low Volume Terminal (MIDS-LVT): a hardware-defined radio developed as a pre-planned improvement of the JTIDS Class 2 terminal, giving Link 16 to platforms short of space and weight.
• MIDS Joint Tactical Radio System (MIDS JTRS): a multi-channel, software-defined variant of MIDS-LVT that adds Link 16 Concurrent Multi-Netting (CMN-4) and Tactical Targeting Network Technology (TTNT), for air, ground and maritime platforms.

The office, PMA/PMW 101, includes the MIDS International Program Office of France, Germany, Italy, Spain and the United States. The Director, Operational Test and Evaluation (DOT&E) FY2012 report says a MIDS JTRS terminal provides the Link 16 data link, Link 16 digital voice, and Tactical Air Navigation (TACAN), plus three programmable channels for other waveforms.

J-series messages

The FY2012 report describes the Link 16 data link as using standard messages to exchange information among platforms and with command and control systems. DOT&E's FY2019 report lists what equipped units exchange: air and surface tracks, identification, fuel, weapons, mission status, engagement orders, targeting data and engagement results.

NATO publishes the message standard. The NATO Interoperability Standards and Profiles catalogue, Baseline 16 of September 5, 2024, lists ATDLP-5.16 Edition C Version 1 (2024), which is STANAG 5516 Edition 9, as a mandatory standard for tactical data exchange. The catalogue says messages shall comply with "the J-series message schema defined STANAG 5516."

The public sources used here name individual messages only by example. A 2004 NATO C3 Agency paper names the J3.5 Ground (Land) Track Message as track data based on STANAG 5516. The paper describes a plan to pass that message through a JTIDS terminal into the Link 16 network of a live exercise.

Which platforms carry it

DOT&E reports name several host aircraft. The FY2012 report covers MIDS JTRS on the F/A-18E/F, which DOT&E then judged operationally effective and suitable, and on the Air Force E-8C Joint STARS. For the F/A-18E/F, DOT&E reported that major deficiencies found in 2010 testing, including ineffective Link 16 message exchange and fine synchronization, had been resolved. The FY2019 report covers the CMN-4 terminal on the F/A-18E/F and EA-18G, and a tailored CMN-4 design for the Air Force F-22.

The E-2D carries it too. DOT&E's FY2023 E-2D report lists MIDS among the subsystems that let the aircraft perform its mission, beside the AN/APY-9 radar, the TTNT data link and the Cooperative Engagement Capability (CEC). The program sheet adds that MIDS JTRS can be integrated into air, ground and maritime platforms.

Limits public sources state

• Shared spectrum. Link 16 operates in the 960-1215 MHz band, which is allocated on a primary basis for aeronautical radionavigation. NTIA says JTIDS may use the 960-1164 MHz part only on the condition that it causes no harmful interference to aviation systems. The DoD and the Federal Aviation Administration have agreements to keep the systems compatible, achieved by limiting the duty cycle of JTIDS and MIDS transmissions and, in the United States, by managing pulse densities.
• Line of sight. The FY2012 report describes Link 16 digital voice as a line-of-sight capability. The NATO catalogue lists a separate standard, STANAG 5518, for the Joint Range Extension Application Protocol (JREAP).
• Message load. DOT&E says the CMN terminals were designed to receive more Link 16 messages during periods of high message exchange. The Navy intended TTNT to provide larger throughput with lower latency than Link 16.
• Network setup. The FY2012 E-2D report found a deficiency in the E-2D's mission planning system loading network configuration data for some Link 16 networks.

What to check

• Does a document distinguish the waveform (Link 16) from the terminal (JTIDS, MIDS-LVT or MIDS JTRS)?
• Which edition of STANAG 5516 does a message claim rest on? NATO's 2024 catalogue lists Edition 9.
• Does a range or coverage claim account for line of sight and any range extension such as JREAP?
• Does a statement about the E-2D's data links separate MIDS from TTNT and CEC, as DOT&E's list does?
• Does a spectrum claim reflect the condition that Link 16 must not cause harmful interference to aviation systems in the band?

Azcuna's ELLMENT, the E-2D Large Language Model Entity, was proposed to NAVAIR PMA-231 under Navy SBIR Phase I topic DON26BZ01-NV010. The prototype, built at private expense on publicly available doctrine, answers with a page-level citation and refuses when the documents do not support an answer. The proposal has been submitted.

Sources

1. 1Multifunctional Information Distribution Systems (MIDS) Program Office, PMA/PMW 101 · Program Executive Office C4I, Distribution Statement A (January 1, 2025)
2. 2960-1164 MHz (Federal Spectrum Compendium) · National Telecommunications and Information Administration, September 1, 2014
3. 3Multi-functional Information Distribution System (MIDS) Joint Tactical Radio System (JTRS) (FY2012 Annual Report) · Director, Operational Test and Evaluation
4. 4Multi-Functional Information Distribution System (MIDS) Joint Tactical Radio System (JTRS) (FY2019 Annual Report) · Director, Operational Test and Evaluation
5. 5E-2D Advanced Hawkeye (FY2023 Annual Report) · Director, Operational Test and Evaluation
6. 6E-2D Advanced Hawkeye (FY2012 Annual Report) · Director, Operational Test and Evaluation
7. 7NATO Interoperability Standards and Profiles, NISP Baseline 16 (AC/322-D(2024)0053, Enclosure 1) · NATO, September 5, 2024
8. 8Dissemination of ISR Data in the Coalition Aerial Surveillance and Reconnaissance (CAESAR): Results and the Way Ahead · NATO Research and Technology Organisation, RTO-MP-MSG-028 (October 2004)

Where this shows up in our work

• ELLMENT, the offline LLM for E-2D crews answers a crew's question from the aircraft's own manuals and cites the page, with no network.
• TRACE, the offline S1000D and IETM viewer opens S1000D, MIL-STD-3001 and PDF technical manuals on a tablet with every marking intact.