Joint Tactical Information Distribution System

Joint Tactical Information Distribution System

The Joint Tactical Information Distribution System (JTIDS) is an L band TDMA network radio system used by the United States armed forces and their allies to support data communications needs, principally in the air and missile defense community. It provides high-jam-resistance, high-speed, crypto-secure computer-to-computer connectivity in support of every type of military platform from Air Force fighters to Navy submarines. The full development of JTIDS commenced in 1981 when a contract was placed with Singer-Kearfott (later GEC-Marconi Electronic Systems, now BAE Systems E&IS). Fielding proceeded slowly throughout the late 1980s and early 1990s with rapid expansion (following 9/11) in preparation for Operation Enduring Freedom (Afghanistan) and Operation Iraqi Freedom. Development is now carried out by Data Link Solutions, a joint BAE/Rockwell Collins company.

JTIDS is one of the family of radio equipment implementing what is called Link 16. Link 16, a highly-survivable radio communications design to meet the most stringent requirements of modern combat, provides reliable Situational Awareness (SA) for fast-moving forces. Link 16 equipment has proven, in detailed field demonstrations as well as in the AWACS and JSTARS deployment in Desert Storm, the capability of basic Link 16 to exchange user data at 115 kbit/s, error-correction-coded. (Compare this to typical tactical systems at 16 kbit/s, which also have to accommodate overheads in excess of 50% to supply the same transmission reliability.)

While principally a data network, Link 16 radios can provide high quality voice channels and navigation services as accurate as any in the inventory. Every Link 16 user can identify itself to other similarly equipped platforms at ranges well beyond what Mark XII IFF systems can provide. Additionally, Link 16-equipped platforms capable of identification through other means (such as radar and TENCAP Blue Force Tracking) can pass that "indirect" identification data as part of its SA exchange. The capabilities of Link 16 are best represented by the JTIDS or its follow-on Multifunctional Information Distribution System (MIDS) terminals. The TADIL-J message format forms the basis for the mandates in the DoD Tactical Data Link Management Plan.

There are benefits to the full-scale implementation of the two key elements of Link-16: (1) the message "catalog" and (2) the specific radio waveform (i.e., frequency hopped, Lx-band CPSM, spread-spectrum and Reed-Solomon coding, omni-directional broadcast). Link 16 terminals implement the "NI" node-to-node protocols as well as one or more of the ICD-compliant user interfaces.

In a typical theater of operations combat forces and elements that are deployed to gather information tend to be scattered, are not always associated with a single unit, may even belong to different services and are not always well coordinated. As a result considerable information may exist about both friendly and enemy forces but the elements that possess that information often are not aware of the combat units who need it. Conversely, combat elements need information about both friendly and enemy forces but have no knowledge about who has it. Classically these "disconnects" have often made the difference between success and failure of a particular military mission. Conventional circuit oriented communications cannot solve this problem. With JTIDS people who have information can broadcast it without explicitly knowing where it is going and combat elements can filter the composite data stream to extract exactly what they need (and no more). One could argue that this is inefficient since more information is being conveyed over the network that any single user wants or needs but given the inability to precisely coordinate information sources and information users JTIDS is the only available architecture that meets the information distribution needs of the modern battlefield. There are situations where specific circuit oriented communications are necessary. For instance the transmission of a command to a combat unit to attack a specific target. It is also reasonable to attempt to exploit the security and jam resistance of JTIDS to accommodate some present communications such as voice. As a result these circuit oriented capabilities were included in the design. At the time this was done, there was concern that operators who were used to dealing with conventional communications would gravitate toward replicating the circuits they were used to over JTIDS at the expense of the new and more responsive architecture. To some degree this seems to have happened. I don't know how to fix it but the capacity concerns and overloading are a symptom of this problem. JTIDS needs to be viewed as a unique and precious resource that does a specific and necessary job better than any other system. For emerging communications needs they should be evaluated and if the specific JTIDS benefits are not needed the problem should be solved by a more conventional approach. JTIDS is bound by a set of parameters dictated by its unique properties in a way that makes it extremely difficult to make significant adjustments to its parameters. It has sufficient capacity to accomplish its primary task (situational awareness) and has some modest additional capacity to accommodate communication tasks that would not justify adding more equipment to a combat unit. This capability, however needs to be used sparingly and carefully so that the primary JTIDS objective is not compromised. —A description of the JTIDS system from the original MITRE program manager Eric Ellingson