Link 4

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Link 4 is a non-secure data link used for providing vector commands to USAF and other NATO fighter aircraft. It is a netted, time division link operating in the UHF band at 5,000 bits per second. There are 2 separate "Link 4s": Link 4A and Link 4C.

NATO Intergovernmental military alliance of Western states

The North Atlantic Treaty Organization, also called the North Atlantic Alliance, is an intergovernmental military alliance between 29 North American and European countries. The organization implements the North Atlantic Treaty that was signed on 4 April 1949. NATO constitutes a system of collective defence whereby its independent member states agree to mutual defence in response to an attack by any external party. NATO's Headquarters are located in Evere, Brussels, Belgium, while the headquarters of Allied Command Operations is near Mons, Belgium.

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Link 4A TADIL C is one of several Tactical Data Links now in operation in the United States Armed Services and forces of the North Atlantic Treaty Organization (NATO). Link-4A plays an important role by providing digital surface-to-air, air-to-surface, and air-to-air tactical communications. Originally designated Link-4, this link was designed to replace voice communications for the control of tactical aircraft. The use of Link-4 has since been expanded to include communication of digital data between surface and airborne platforms. First installed in the late 1950s, Link-4A has achieved a reputation for being reliable. But Link-4A's transmissions are not secure, nor are they jam-resistant. However, Link-4A is easy to operate and maintain without serious or long-term connectivity problems.

Link 4C is a fighter-to-fighter data link which is intended to complement Link 4A although the two links do not communicate directly with each other. Link 4C uses F-series messages and provides some measure of ECM resistance. Link 4C is fitted to the F-14 only and the F-14 cannot communicate on Link 4A and 4C simultaneously. Up to 4 fighters may participate in a single Link 4C net. It is planned that Link 16 will assume Link 4A's role in AIC and ATC operations and Link 4C's role in fighter-to-fighter operations. However Link 16 is not currently capable of replacing Link 4A's ACLS function and it is likely that controlled aircraft will remain equipped with Link 4A to perform carrier landings. Message standards are defined in STANAG 5504 while standard operating procedures are laid down in ADatP 4.

See also

Joint Tactical Information Distribution System

The Joint Tactical Information Distribution System (JTIDS) is an L band Distributed Time Division Multiple Access (DTDMA) 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 produces a spread spectrum signal using Frequency-shift keying (FSK) and Phase-shift keying (PSK) to spread the radiated power over a wider spectrum than normal radio transmissions. This reduces susceptibility to noise, jamming, and interception. In JTIDS Time Division Multiple Access (TDMA), each time interval is divided into time slots. Together, all 1536 time slots in a 12-second interval are called a "frame". Each time slot is "bursted" (transmitted) at several different carrier frequencies sequentially. Within each slot, the phase angle of the transmission burst is varied to provide PSK. Each type of data to be transmitted is assigned a slot or block of slots (channel) to manage information exchanges among user participation groups. In traditional TDMA, the slot frequencies remain fixed from second to second. In JTIDS TDMA, the slot frequencies and/or slot assignments for each channel do not remain fixed from frame to frame but are varied in a pseudo-random manner. The slot assignments, frequencies, and information are all encrypted to provide computer-to-computer connectivity in support of every type of military platform to include Air Force fighters and Navy submarines.

Link 1 is a computer network standard developed by NATO to provide information exchange for air defence.

Link 16 is a military tactical data link network used by NATO and nations allowed by the MIDS International Program Office (IPO). Its specification is part of the family of Tactical Data Links.

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References

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