The Utility of Tactical Data Links
In the mid-1990s, with the end of the Cold War all major military powers studied a different role and structure of military capabilities. The universal conclusions were that future wars were likely to be modest in size, could develop rapidly and almost anywhere where religious, economic and political instability was evident.
The conclusions also led to the realisation by significant military powers that a different approach to war-fighting was required – one that focussed on an integrated fighting capability that was highly mobile and flexible. In most cases that must also include NATO and other allies since the new threat was global.
There was also the realisation that international politics must play an increasingly important role to defuse hot spots by negotiation with using the force of arms only a last resort.
At that time, major military powers and smaller ones (such as Australia) operated a traditional decentralised military structure comprising largely independent navy, army and air force services, with relatively poor communications between each except at the tactical level. Even at the penultimate command level, isolation was evident. Strategic decisions were largely the province of a country’s government in consultation with all three services – and that often led to wide differences of opinion.
The decentralised military structure began to break down, probably first in the United States, with the realisation that force and mission integration was imperative and not in the style of frequently independent service operations which occurred in WW11 and the Vietnam War. Exceptions then were invasions, as combined operations, with a different management arrangement.
The development of the ability to conduct warfare with an integrated force led to major changes to the design of standardised digital data processing systems in ships, aircraft, submarines and land forces. All of these forces required better communication systems, with the ability to process significantly larger amounts of data securely and in near real time.
One of the first force elements to adopt this approach was the US Navy – operating a largely autonomous and highly mobile fleet that could establish a major power base almost anywhere in the world. But the success of this approach depended on the adoption of digital computer-based systems and high bandwidth, very high data rate, and digital communications – the latter requiring the development of a digital data link. So the era of digital computer-based combat systems and digital communications for military applications was “in,” and communications by voice and manually operated plotting tables were relegated to the museum.
This huge transition was led by the United States across its four services, but especially the US Navy. Europe soon followed. This transition fostered the developed of the Tactical Data Information Link now universally known as a “TADIL” in US Military parlance, or as “Links” in other military organisations.
TADILs were first adopted by the US Navy for its fleet operations including carrier-borne aircraft, followed by a plethora of others for almost every land and air operation where digital communications were essential. The use of TADILs was soon adopted by all NATO nations. As a result the US Department of Defence developed military standard specifications for modems, the variable message format, military designations and other specifications relevant to this new technology.
However, whilst this allowed the development of more powerful and complex combat systems, the introduction of the much newer concept of networked centric warfare [NCW] was still many years into the future.
In Australia, fleet modernisation requirements resulted in the purchase of three US Navy Charles F. Adams DDGs in the 1960s which were fitted with a variant of the US Navy’ s Naval Tactical Data System, called the Junior Participating Tactical Data System [JPTDS].
JPTDS (or “Jeeps” as it was more often known) marked the introduction of a digital-processor-based combat system that paved the way for the addition of a digital data link. The Royal Australian Navy [RAN] nominated JPTDS as its naval combat data system [NCDS] and a land-based version was installed, operated and further developed at the Naval Combat Data System Centre, located in Canberra. With US Navy and United States contractor support – combined with the RAN and local contractors – the NCDS provided excellent service until the ships were retired. A similar system installed in the six FFGs was also purchased from the US Navy. These two classes of ship later received the Link 11 tactical data link, necessitating modernisation of naval communications systems.
The adoption of digital combat and digital communications systems by the Army and the Royal Australian Air Force was not that simple. Their systems required digital data link solutions that were compatible with equipment they used and operated. As a result, Australia’s establishment of a seamless inter-service integrated digital data network is still evolving.
Overseas, the US Armed Forces “lead the pack” with digital data links that met their requirements and led to the adoption of United States products by some NATO countries. However, others who were not members of NATO developed their own solutions that were not always interoperable with United States systems. Countries like Australia that predominantly bought United States equipment got what those systems came with, and that in turn complicated the development of an ADF-wide information grid.
Concerning the adoption of NCW, Australia – as a committed ally of the United States – began to study the applicability and impact on the ADF of what was then known as the revolution in military affairs about a decade ago. But it appears that Australia considers NCW not as a methodology of fighting a conflict but rather the adoption (or development) of a philosophy that defines how the ADF will combine all its military assets and apply them. NCW will not replace the skills and determination of military force, but it is an enabler.
Elsewhere, there does not appear to be within NATO or US Allies a single “tablet in stone” that defines NCW, but General Klaus Naumann, former Chief of Defence of Germany, described it as an “…information superiority-based concept of operation that produces increased combat power through networking of sensors, decision makers and actors and is able to translate information provided by dominating battlefield situation awareness into full-spectrum dominance.”
From the foregoing, it will be evident that Tactical Data Links (TDL) will have to be capable of evolution to match their perceived or actual operational environment and the platforms in which they will be installed.
What is a TADIL?
In the simplest sense, a TADIL is a device that enables digital data to be shared at high speeds between elements of a force – whether maritime, airborne or land – using compatible radio communications. A TADIL is not limited today to operation in a tactical environment, so the name is something of a misnomer. A TADIL is installed in each contributing element of a given communications network and has full-duplex capability. Data to be transmitted is assembled into bit-oriented (machine readable) format required by digital-processor based C2 systems. Some TADILs will also process voice data. The address of each element in a given network is established using time-multiplexed techniques – time division multiplex access [TDMA] – where each element of the network has a specific time slot, or an address. Data are usually assembled using the variable message format [VMF] technique that reduces message size and the transmission period by deleting repetitive data. There is a large range of VMFs.
TADILs employ additional techniques to make radio transmissions between elements jam-resistant, but these techniques do not affect the communications network itself. TADILS are designed to operate using UHF/VHF, HF and Satcom bearers as a function of the required communications range and network structure. Data output by a TADIL is controlled by the originator it serves. TADILS do not require an operator in the loop.
In order to extend the utility of a TADIL, interoperability between legacy systems and newer ones is available.
In the quite near future, TADILS are highly likely to be adopted for unmanned aerial vehicles [UAVs] and land-based robotic systems as the requirement to integrate these devices into an NCW environment evolves and the density of their use increases.
TADILs will continue to evolve on a needs basis, for communications required by the user, including application, technology advances and performance improvements – particularly security and jam resistance. COTS and MOTS technologies are being widely adopted as they offer improved design standardisation, higher reliability and availability, platform adaptability and usually reduced cost. Major effort is also being spent to reduce their physical size and mass allowing them to be installed more easily into airborne platforms. As the complexity of application increases – for example in UAVs of all classes – it appears likely that present communications required by these systems will yield to the use of TADILs.
Types of TADILS
The list of TADILS below is not exhaustive, but covers the predominant devices:-
LINK 11 (TADIL A)
Link 11 (NATO user designation), known as TADIL A/B (US Designation), is a fairly early, widely used, 1960s vintage technology device, which was and is primarily used by airborne, land-based and shipborne tactical data systems. It provides netted, point-to-point, full duplex serial transmission high-speed digital communications using standard message formats. It operates with HF and UHF communications networks. With HF and UHF networks, it operates at 1364bps (HF, UHF) and also 2250bps (UHF), providing ranges of around 300km (HF) and around 25km (UHF).
Link 11 normally operates on a “network polling” scheme, with one station controlling the polling of the others in the network, but it maybe configured to operate in the broadcast mode when its transmits in half-duplex mode to other participants.
Link 11 supports data exchange between ships, aircraft and ground-based system participants by processing electronic warfare [EW] and command data, but it does not support aircraft control or other warfare activities.
Link 11 is secure but is not fully ECM-resistant and the latter feature limits its application to benign environments. A feature later introduced in Link 11, called the Single Tone Link 11 waveform, disperses data bit errors uniformly to increase the link’s ECM resistance.
Variants of Link 11 have been produced by companies to overcome the link’s shortfalls. One of these, attributable to DRS Technologies, provides interoperability across all operational modes of Link 11A by software reconfiguration. It operates with HF, UHF and satellite data links, by selection. The system also provides for operation with a number of different network configurations to satisfy single and dual networks and single channel or multiple frequency link operations, with up to four channels operating simultaneously at high or low data rates. The flexibility of this data link allows it to be interfaced with a range of other data links and RF communications.
Link 11B (TADIL B)
This link provides a dedicated fully automatic point-to-point, full duplex, digital data capability using serial transmission frame characteristics defined by standard message formats. The link embodies phase continuous FSM and operates at the standard rate of 1200bps, with optional 600bps and multiples of 1200bps to give 2400bps, 3600bps 4800bps and so on, depending on the bandwidth of the communications bearer. Units that exchange data using Link11B are designated as reporting or forwarding reporting units
Link 11B is widely used in ground-based systems applications.
Link 4A (TADIL C)
This link provides netted, time division multiplexed data and operates in the UHF band at 5,000bps. Introduced in the late 1950s, the link has a reputation for reliability, ease of use and availability. The link was developed to replace voice communications for the control of tactical aircraft by providing digital surface-to-air, air-to-surface, and air-to-air communications. Link 4A’s transmissions are not secure, neither are they jam-resistant.
Link 4C is a derivative of Link 4A to provide a fighter-to-fighter connection to complement 4A, but the two links are not interoperable. Up to four aircraft can communicate using 4C. Link 16 is the replacement for this link.
This is a specialised link that handles broadcast HF teletype data for maritime units that have tactical data system capabilities to units that do not have them and which do not have Link 11 capability. The link will operate with HF, VHF and UHF depending on the units’ communication configurations. Transmission formats are user dependent.
Link 16 (TADIL -J)
This is a relatively new link that is widely deployed by the US Armed Forces, some NATO countries and Japan – and is now being introduced into service in Australia. Link 16 was designed to operate with the US Joint Tactical Information Distribution System [JTIDS]. JTIDS is an advanced radio communications system that distributes a wide range of tactical information, including position location identification. This is done at high data rates and in an encrypted, jam resistant format. JTIDS (developed by the United States) is a multi-service system that is also intended to be used by allies.
Link 16 is the primary TADIL for command, control, communications and information systems as it provides crucial joint interoperability data, including situational awareness. Link 16 uses TDMA architecture and the “J” message format standards. These are the designated standards for TADILs.
Link 16 does not materially change the basic concepts of tactical data links employed by earlier Link 11and Link 4A TADILs. However, Link 16 provides significant performance improvements, including technical and operational advantages – the former including improvements in jam resistance, security, higher data rates and better granularity of exchanged data. The latter includes largely automatic operation, following establishment of a specified network.
A third generation Link 16 called multi-function information system [MIDS] low volume terminal is an international cooperative program, designed to satisfy the Link requirements of the United States and its cooperating partners. MIDS uses new technology to reduce mass and size.
Additionally, Link 16 is subject to a communications Joint Range Extension program called the TADIL JRE. This program seeks to extend the range of JTIDS to beyond-line-of-sight [BLOS], without requiring the use of an airborne relay. In so doing, the JRE will significantly improve the size of the operational area of JTIDS. Several methods of achieving JRE have been studied, including the use of a SATCOM link.
This link – also referred to as the NATO Improved Link Eleven – is considered to be a hybrid between the MIDS Link 16 and Link 11 as it adopts many of the operating features of these links, particularly Link 16.
Link 22 is defined to be the next generation NATO TDL to replace Link 11 and 16. It is being developed by a collaborative multi-national NATO group, with the United States as a host nation. The collaborators are Canada, France, Germany, Italy, The Nederlands, United Kingdom and United States. The Netherlands dropped out and were replaced by Spain. System availability dates were scheduled for 2009 onwards.
Link 22 uses a computer-to-computer digital link and operates between TDS equipped maritime, land and air assets which comply with the requirements of STANAG 5522 and ADatP 22. Link 22 is also defined to be able to use, as far as possible, existing radio equipment.
From a technical standpoint, Link 22 is an ECM resistant, BLOS tactical data communications system that operates in the HF and UHF bands and is able to use fixed or frequency hopping techniques. The system will operate in TDMA or dynamic TDMA modes for flexibility of operation, and can also use VMF formats.
Link 22 is classified as a “Link 16 family” data link – along with its formats, including VMF. The 72-bit word structure can carry embedded J-Series Link 16 messages (FJ Series) as well as Link 22 F Series messages. This capability significantly enhances its operational flexibility.
There is also considerable emphasis on Link 22’s ability to operate in a network mode. It can operate with up to four discrete networks simultaneously, to form a super network, with each using different radio systems, and with any participant on any network being able to communicate with any other network with data forwarding capabilities. Coupled with network management and super network management, within the design of Link 22, the potential to react dynamically to varying communications loads and operating conditions is provided. These capabilities are highly important in the context of interoperability, NCW and future warfare environments.
The Tactical Common Data Link for UAVs
An embedded capability that differentiates many UAVs from tactical fighters, transport aircraft and even the yet to be delivered Wedgetail AEW&C (all of which use data links for tactical purposes) is UAVs typically incorporate stabilised daylight and infra-red cameras and frequently synthetic aperture radars as well. These sensors collectively are able to scan the earth below, and provide intelligence, surveillance and reconnaissance [ISR] data and transmit it in near real-time to multiple users. The transmission of this video imagery requires the use of a high bandwidth data link and a dedicated portion of the frequency spectrum. Australia has reserved all or part of the 14.5-15.35 GHz spectrum for government and military use in this application.
The advent of highly capable UAVs and their ability to carry an ISR payload led to the development by DARPA of the tactical common data link [TCDL]. The goals were the development of a family of low cost, light-weight, current CDL compatible data links. These needed to support a wide range of airborne ISR sensors, with interoperability between multiple TCDL platforms and ground TCDL stations. The performance requirements included a full-duplex, digital transmission between platforms and ground stations using point-to-point LOS slant range connections of 200km (goal) and 150km (requirement) at an altitude above ground of 15,000 feet. The platform, TCDL, was also specified to be capable of receiving a spread spectrum transmission for platform control.
Apart from the above aims, design implementation was also required to adopt as much COTS as practicable and open architecture techniques with commensurate flexibility – enabling changes in application without significant re-design being necessary. TCDL development was led by the US companies L-3 and Harris.
Since that time in the late 1990s, TCDL applications have expanded to include the P3-C maritime patrol aircraft that has a similar ISR payload to an advanced UAV, plus ESM, and growth to the TCDL-extended littoral battlespace for the US Navy’s wide area relay network. This is a high-bandwidth, interoperable, Ku-band, digital communications link and is being applied to the US Navy’s MH-60R shipbourne helicopters carried by US Navy’s FFG-7 and DDG-51 ships. The system with the commercial name of “Hawklink,” is being produced by a Harris/BAE Systems team.
TCDL will progressively become the data link of choice for all UAV applications and for manned aircraft that provide ISR and targeting data for eventual incorporation in networked communications systems used by tactical and shooter applications.
The adoption of Tactical Data Links by Australia
A conclusion is being reached in the United States and United Kingdom (to name but two countries) that designing a communications network is the critical driver for the selection of a tactical data link and the element that will use it. The logic of this approach is difficult to refute. For example, the Eurofighter has been defined to be an element of a network – rather than just an aircraft – and this approach has also been adopted by the United States. Sweden adopted this approach in the 1960s, and the use of data links on the ‘Draken’ aircraft was a national secret for at least 20 years.
Whilst history shows that the United States started off the other way round by developing data links without a network (an approach that is simply analogous to starting to lay bricks without a house plan), Australia might be set on a similar course.
Two undated Defence presentations on the subject showed that Defence was/is proceeding to equip existing major maritime and air assets with Link 16 and foreshadowed the installation of that Link in new, yet to be delivered acquisitions (e.g. AWD, Wedgetail, Vigilaire, AP-3C replacement and HALE UAV). The product of this approach appears, possibly, to be a number of small limited communications networks, focussed on operationally related assets, and not the design of an infinitely broader integrated network. So expediency, rather than mind-numbing research to produce an ADF-wide operationally integrated communications network, that will be capable of interoperability with a global information grid, appears to be the order of the day.
Although it has to be recognised that smaller, discrete and dedicated networks – such as TCDL described above – can be established and then integrated at progressively higher command levels to provide larger force integration, this will be achieved at the expense of longer, higher density, communication paths between the smaller networks. There are also issues of the adoption of new TADILs such as Link 22 that are yet to be fully evaluated.
Another issue worth visiting is that Defence does not appear to have considered it to be desirable or essential to encourage Australian defence industry to become involved in digital data link [DDL] development, manufacture and support -yet it has supported for many years the development of an indigenous EW. Whilst it is accepted that EW is a critically important capability for the ADF and industry to possess, because of some uniqueness in the ADF’s operational environment, it is evident that an ADF-wide communications network is likely to have a uniqueness of the same magnitude, at least, as EW. Companies, who are suppliers of systems or data link technology, such as Boeing, L-3, BAE Systems, Saab Systems and QinetiQ – all of original foreign origin but now resident in Australia – might be contributing to the development of the architecture of a system for the ADF. DSTO will also be making a significant contribution.
However, the fact that Australia does not have an industrial base capable of design, developing, manufacturing and supporting DDL must be considered as an unfortunate circumstance – to put it mildly – as it leaves the country completely in the hands of overseas suppliers. This is clearly undesirable when it is considered that the total number of DDLs, of various types, is possibly in the order of 300-500 units, not all of a common design, but all of which have definable life cycle.
Development and establishment of an integrated network that is compliant with the ADF’s requirements and those of its allies is not a matter of why, but when and how, and the ADF has no option but to accept the cost of this activity. It also has to accept the costs of selecting and embedding suitable DDLs in ADF assets to provide ADF-wide and allied interoperability.
To acquire DDLs without having developed the network within which they operate is a case of “ad hoc-racy” working against the totality of the objectives. This form of acquisition also carries the high risk of getting a DDL that is not fit for purpose, might also be obsolescent or obsolete, and not supportable. Beware the snake-oil salesman.
Figure 1 below is a very simple Venn diagram of what a limited network might comprise. Being simple, the diagram does not address the following:-
No definition of the number of elements (assets) in a segment (coloured circles) and no definition of the force structure of the elements within a segment.
No definition of the operational area that each segment might cover (communications issue).
No definition of the role of each segment (land, maritime or air) with the role of each of these segments having different networking requirements.
An assumption that each segment must be capable of communications with the other two.
An assumption that there is a higher command capability that controls the operations of the segments.
No definition of how the segments might interoperate within a larger “allied force” network, directly or through the higher command capability (technical, doctrinal issues). This factor will vary as function of the operation of each segment and the contribution it makes to the allied force. The simplest example is one where a segment is fully attached to the allied force, but retains the capability to report to the higher command structure.
The implementation of NCW as a philosophy and its implementation as a practice is not going to go away. It is a huge challenge that in many respects is unique to the way the ADF operates.
A fully integrated scalable, flexible, communications network that will continue to evolve, necessary for NCW and allied interoperability is a major program and intellectual challenge. It is a program that will be necessarily multi-phased.
Unlike many other projects, Australian industry does not appear to have been publicly invited to participate in the program and this will disadvantage the ADF’s future objectives, by tying the country to foreign DDL and communications products (consider the results of HF modernisation program).
Defence might be “backing into” the program by proceeding with the equipping of selected assets using United States products of earlier vintages as a stop-gap measure.