Technologies

Link 22 - Ready for operational use

Link 22, also known as NATO Improved Link Eleven (NILE), is a communications standard for tactical data links. The new standard is planned to replace the widely used Link 11 in the medium term and will be employed concurrently with Link 16.

Tactical data links are particularly important as far as digital naval communications are concerned. NATO and allied navies use the Link 11 protocol, which allows the exchange of radar track information and written messages between ships, shore installations and aircraft. Link 11 uses HF (High Frequency) and UHF (Ultra High Frequency) communications. The use of both HF and UHF for Link 22 is to enable traffic to travel across line-of-sight and over-the-horizon ranges. Up to 61 participants can be hosted on a Link 11 network at any one time. Link 11 is now being superseded by Link 22, boasting noticeable increases in capability, e.g. up to 125 participants can be hosted and it can achieve data rates of 4kbps when using an HF network, increased to 12kbps when using a UHF network. While Link 11 is expected to remain the chief naval tactical data links for another ten years, it will be progressively replaced by Link 22 from about 2024.

Link 22 is another important element in the exchange of information in network-centric warfare. Tactical data links are mainly used to exchange sensor-to-shooter information and situational awareness information (with its focus on command and control support).

NATO’s goal is to establish a tactical data link that allows the exchange of information among different military platforms such as ships, submarines, aircraft and shore-based stations. This exchange should be immediate and remain possible even in tense situations and hostile environments. Existing standards (e.g. STANAG 4205 for fixed-frequency operation and STANAG 4273 for EPM operation) are to be adapted to enable the continued use of radios deployed in previous Link 11 systems.

Link 22 was developed by seven NATO countries (Canada, France, Germany, Italy, Spain, UK and USA) on the basis of a memorandum of understanding (MoU). Deliveries to countries not belonging to the seven NILE nations will be governed by agreements with the NILE program management (NILE PMO). Link 22 is intended to be used primarily by naval forces and is being progressively rolled out across navies.

Outstanding features of the new standard include optimized information processing, a higher data rate, a transmission technique less susceptible to interference, and a flexible network topology. Employing dynamic time division multiple access (TDMA) mechanisms, Link 22 can also adapt quickly to changing communications structures during missions. Up to four radio networks can be combined for operational use. Crypto mechanisms and the use of radios with frequency-hopping capability (HF and/or UHF) ensure secure communications.

A committed partner: Rohde & Schwarz

Tried and tested

With its extensive expertise, Rohde & Schwarz supports not only the IT office of the German Armed Forces and NILE PMO, but also numerous customers worldwide. Within the framework of Link 22 related activities, Rohde & Schwarz participates in many international Link 22 conferences, workshops and demonstrations, contributes actively toward the optimization and standardization of the new tactical data link, and provides input to various working groups in NATO.

Link 22 can be employed in the HF range (2-30MHz) and the UHF range (225-400MHz). UHF is intended for line-of-sight (LOS) communications, HF for links up to 1,000nm (1,852km). Fixed-frequency modes as well as EPM (ECCM) modes are defined for both HF and UHF.

For the UHF range, two alternative approaches were worked out for implementing an interface between EPM UHF radios with frequency-hopping capability and the Link 22 modem. These are to serve as official NILE interfaces. Rohde & Schwarz, in cooperation with TELEFUNKEN RACOMS, defined one of the two interfaces and developed it for series production.

Link 22 tests have been conducted in real-world environments for several years. Rohde & Schwarz took part in a test in Finland as early as 2007, where data was exchanged within a supernetwork consisting of three subnetworks referred to as NILE units. One command ship and two land-based stations located at different sites were simulated. It was the first test of its kind transmitting real radar data over a Link 22 tactical data link.

In the meantime, further tests have been carried out using Rohde & Schwarz equipment, e.g. in Germany and France. These tests demonstrated that the software defined radios of the Rohde & Schwarz M3SR family – including R&S Series 4100 HF radios and R&S Series 4400 UHF radios – can work error-free with each of the three Link 22 modem types currently available.

Link 22 has since matured to a degree that allows its installation in customer systems. The active participation of Rohde & Schwarz in developing this data link standard ensures that customers will always obtain the optimal solution for their radio applications. Already delivered radios can be upgraded to support Link 22 protecting the investments made by our customers.