Tactical Data Links - Link 11 and 11B
Key words and phrases: tactical data links, link 11, link 11b, standard message formats, high frequency
Link 11, also known as
TDL A (previously TADIL A) in the US, employs netted communication
techniques using standard message formats. Data is exchanged using the
Conventional Link Eleven Waveform (CLEW) over a differential quadrature
phase-shift keying modulated data link operating at a rate of 1364 (HF/UHF) or
2250 (UHF) bits per second (bps). Since this former is susceptible to ECM, a
recent addition has been the Single Tone Link Eleven Waveform (SLEW), which
disperses data bit errors uniformly utilising data interleaving and employs Full
Tail Biting Convolutional Block (FTBCB) encoding. This greater ECM resistance
provides a data rate of 1800 bps.
Link 11 is designed for operation on High Frequency (HF) and thus has a beyond line of sight (BLOS) capability (to a theoretical range of approximately 300 NM).
Link 11 can also operate in the UHF band but is then limited to LOS ranges (approximately 25 NM surface-to-surface or 150 NM surface-to-air). As an alternative, communication media satellite and fibre optic can be used. Units which exchange data via Link 11 are designated Participating Units (PUs) or Forwarding Participating Units (FPUs).
Link 11 is based on 1960s technology and is a relatively slow link which normally operates on a polling system with a Net Control Station polling each participant in turn for their data. In addition to this "Roll Call" mode, Link 11 may be operated in broadcast modes in which a single data transmission or a series of single transmissions is made by one participant. Link 11 is, therefore, a half duplex link. Link 11 is secure but not ECM-resistant.
Link 11 supports the exchange of air, surface and subsurface tracks, EW data and limited command data among C2 units, but does not support aircraft control nor other warfare areas.
Within the UK Link 11 is employed by the Royal Navy, Royal Marines and Royal Air Force in its Ships, Ship Shore Ship Buffers (SSSBs), E-3D AEW, Nimrod MPA, Tactical Air Control Centre (TACC), etc. Within NATO Link 11 is primarily used as a Maritime Data Link. However, Link 11 will be adapted to cater for Theatre Missile Defence information exchange, consequently Ground Based (Surface-to-Air Missile) SAM Systems are or will be equipped with Link 11. Within NATO and beyond, Link 11 is widely fitted in ships, airborne surveillance and some ground facilities.
Link 11B/TADIL B
Link 11B employs a dedicated, point-to-point, full-duplex digital data link using serial transmission frame characteristics and standard message formats transmitted by individual signal elements or binary digits on a time sequential basis. Data is exchanged over a fully automatic, phase-continuous, full-duplex, frequency-shift-modulated data link operating at a standard rate of 1200 bps with optional capabilities of 600 and 2400 bps (or multiples of 1200 bps, e.g. 3600, 4800, etc.) Units which exchange data via Link 11B are designated Reporting Units (RUs) or Forwarding Reporting Units (FRUs).
Within the UK, Link 11B is or will be employed by the TACC, the second generation SSSBs and for ground-to-ground communications with the Iceland Air Defence System (IADS). Within NATO Link 11B is used to integrate Ground Based SAM Command and Control and Fire Distribution Centres into the Air Defence Ground Environment using Control and Reporting Centre (CRC) SAM Interfaces (CSI). Within the US, and some other NATO Nations (e.g. France), Link 11B is used as the primary data link for ground based TACS (e.g. USAF MCE, and USMC TAOC).
Message standards for both Link 11 and Link 11B are defined in STANAG 5511 (US MIL-STD 6011) while Standard Operating Procedures are laid down in ADatP 11 and the Multi-Link ADatP 33 (US JMTOP).
Data Link descriptions: Tactical Data Links | Link 16 | Link 11 | Link 22 | IJMS | Link 1 | Link 14 | Link 4 | Other protocols | CDL, TCDL & HIDL | Satellite Link 16 | Variable Message Format - VMF
Further information is available from:
Email:
Tel: +44 (0)1252 732555
