Future battlefield wireless comms

Dr Dave Sloggett explores the implications of ad hoc coalitions and looks forward to the next generation of battlefield combat net radio systems and the application of wireless technologies

Future battlefield wireless comms

Since the start of the Second World War, communications systems have been a vital element of how military commanders control the movement of their assets on the battlefield. As operational manoeuvre became a military imperative, new technologies provided command and control systems that allow commanders to direct the movement and disposition of their forces.

The Battle of Britain in 1940 arguably provided the first operational example of the application of that capability.

Today, military commanders still need to be able to direct the movement of troops, warships and aircraft to achieve their objectives, and communications systems provide the backbone through which command and control can be exercised. Now, as military forces are to be scaled back over the coming years, it becomes more important than ever to use advances in communications to make the best use of whatever assets can be deployed into theatre.

Ad hoc coalitions of the willing parties are also unlikely to become a thing of the past. Applying military power also has to be done on a more selective basis. It is unlikely that the shifting balance of military power towards the less kinetic end of the spectrum is going to change. As the operations in Libya showed in 2011, it is vital to do everything you can to avoid killinWg civilians.

Unforeseen situation

These perceptible shifts in the paradigms of war never fully rule out a return to the kind of planning and exercises needed to prepare for total war, no matter how likely or not that is in the immediate future. There are still places around the world where international, political and military pressures may create an unforeseen and dire situation that requires a large scale military intervention of the form seen in Iraq in 1991 and 2003.

In both of the Gulf Wars, communications systems played a vital role in helping commanders move quickly to achieve their objectives. The innovation of the blue force tracking systems in the Second Gulf War was one very notable development that allowed commanders to synchronise the movements of their formations to achieve their military objectives.

The need to be able to conduct all-out industrial-scale warfare is something that cannot simply be eradicated from military preparations. Historical precedents simply cannot be ignored. But in the current international security landscape, military operations in the foreseeable future are likely to involve sending multinational forces into places around the world, often at short notice, either to help in the aftermath of a natural or man-made disaster or to help the internationally recognised government of a country establish and maintain security.

All of this has implications for the kind of radio communications systems that military forces may have to deploy in the future. The need to be able to react quickly is a characteristic of future military interventions – time will be of the essence. The solutions that will be needed may stretch the capacities of existing systems. It is axiomatic that no matter where military forces are deployed, bandwidth is always an issue.

Historically, systems such as the Clansman combat radio system provided voice communications systems over High Frequency (HF) and Very High Frequency (VHF) radio channels. They provided a flexible mix of capabilities that allowed military units to communicate in line of sight and beyond the radio horizon when needed.

Battlefield digitisation

Digital technologies were not yet at a state where anything other than voice could be passed. The first step in the digitisation of the battlefield focused on signal processing applications designed to reduce the bandwidth requirements for voice communications. This effort concentrated on eliminating redundant parts of speech to make efficient use of the limited bandwidth that was available.

Bowman was the first generation of a combat net radio (CNR) system deployed by the British Army. Its pathway into service was complicated – introducing new technologies to the battlefield can prove difficult. But by bringing together components from a number of different developments, Bowman arrived on the battlefield in Afghanistan. It has provided a really adept CNR capability, yet as ever with some military projects, defence officials have already started to look towards the next generation.

These network systems provided the first set of battlefield applications to the British Army in areas such as directing artillery fire. But this was a system designed for the Cold War and still relied on a mix of HF and VHF systems with all their associated bandwidth limitations. To conduct future military operations, the focus of the requirement of combat net systems has to move from the movement of digital voice and small quantities of data to real-time video and imagery.

To reduce civilian casualties and to ensure military power is applied proportionately, imagery will be needed. It also provides the lawyers that inevitably watch over contemporary military missions with any evidence that might be needed during or after the conflict. In situations where the media can be swift to accuse military forces of misdemeanours the ability to rebut those statements is paramount.

As expeditionary warfare has developed in the last 20 years from Kosovo to Libya, the need for higher bandwidth systems has become increasingly obvious. To apply soft power and avoid civilian casualties, the need for network imagery to be collected from the plethora of intelligence, surveillance, target acquisition and recognition (ISTAR) systems has become clear.

Short-term solutions to this have been achieved by using point-to-point links where the ISTAR platform is within line of sight of the units to which they are supplying real-time digital imagery. Unmanned aircraft such as the Predator, which is flown by the Royal Air Force, are a good example. They provide their digital imagery in real-time to ground-based Rover terminals.

Profound implications

This need for universal access to digital imagery has profound implications for the next generation of combat net radios. Networks for those systems simply have to be capable of generating sufficient bandwidth to allow real-time imagery to be streamed to units that are not necessarily in line of sight of the collecting platform. Satellite communications systems are not yet able to provide a solution to this need.

In time, having mobile satellite communications on the move using adaptive antennas may well provide some capability.

But bandwidth will always be in demand. To do this, very high bandwidth and secure communications systems need to be capable of being deployed. The question is, what might the solutions to that requirement look like?

One lesson that is unlikely to be forgotten from the procurement of the Bowman CNR is the need to incorporate off-the-shelf technologies into the solution. Bespoke developments are likely to be a thing of the past. They are simply too risky and delays inevitably ratchet up the costs. What is required is the ability to harness the ubiquity of commercially available technologies from the civilian world into the military world. After all, both domains consist of people on the move that need access to digital imagery.

Innovation

Developments in the field of optical fibre technologies allowed fixed civilian applications requiring higher data communication speeds to flourish. Major commercial concerns involving social networking applications have been built on that technological innovation. As people got used to accessing bandwidth at home they also wanted it on the move.

The speed with which mobile phone technologies have provided solutions to that need has been amazing. In built up areas where mobile phone masts have proliferated rapidly over the past 10 years, coverage of high bandwidth services is growing all the time. The introduction of fourth generation systems will take it to a new level.

Given the obvious similarities between mobile phone demands and the need for imagery on the move, there’s an obvious question: why not replace the current generation of CNR with systems based on mobile fourth generation systems?

As the billions sunk into the Bowman system development will always provide an emotional barrier, the solution is to chart an incremental path adding to the Bowman system’s capability in discrete steps. This is where the wireless technologies that are emerging in the commercial world can be applied into the military environment.

The major issue between the civilian and military applications of wireless technologies is the problem of range. A simple model of the trade-off in distance and power is provided in the example below (see page 14). In situations where time is of the essence, the military need to be able to take their radios with them in vehicles and in man-portable configurations that allow them to remain in touch with their command chain.

Solutions to this quandary require new paradigms for CNR. In military operations where the political imperative is to reduce the time on deployment to a minimum, the forces simply have to carry the communications backbone with them. Time does not permit investments in fixed infrastructure.

Point-to-point communications need to be enhanced with flexible and agile broadcast and multi-casting options. Digital imagery needs to be routed to those who need to see it. At the patrol level in the British Army that means the communications backbone must be capable of finding digital pathways that may open temporarily between two or more discrete points and then prioritise the movement of specific data between the two nodes. 

Close quarter battle

Battlefield situations can be confusing. If a formation is engaged in a close quarter battle, the range between individual elements may allow one to be the main receiver of the source imagery and then route it onto other members in the formation that need to see the data.

Where mobile units are operating within 1km of each other wireless solutions delivering 54 Mbps are possible, depending upon the terrain. Doubling that range, however significantly, reduces the link margin, making the movement of data at the desired rates difficult.

One solution may be to use adaptive antennas that are capable of altering their directionality, increasing gain in specific directions. Knowledge of the current positions of each of the member elements of the formation would be important. The bandwidth requirements for this are low. Operating to ranges beyond 1km is likely to be possible if the next generation CNRs are flexible enough to spot pathways that open as formations move on the battlefield. Those pathways could be created in ground-to-ground links or by using airborne platforms as relay points.

While it is difficult to place constraints on formation commanders to maintain units within a certain distance of each other, the movement of such forces is often orchestrated.

Units provide support for one other, not operating entirely autonomously. Algorithms that can store and forward imagery when pathways open, even on a temporary basis, are going to be important in future CNRs to ensure the kind of broadcast and multicast services needed by formations are available. 

Mobile router

Airborne relay points may also provide pathways acting as a mobile router. The issues will be whether those platforms are manned or unmanned, how long they can remain on station and the nature of the threat they face.

The US already deploys the Battlefield Airborne Communications Node (BACN) to provide a degree of interoperability between the different communications systems deployed in theatre. Its first successful test was conducted in 2006, while its developers, the United States Air Force and Northrop Grumman, received acknowledgement of their efforts in 2010 with the award of the Network Centric Warfare Award from the Institute for Defence and Government Advancement (IDGA).

Today, BACN provides the capacity for battlefield communications systems based on legacy waveforms and digital systems to interoperate, acting as a bridge. As the legacy systems inevitably become replaced with the next generation of Internet Protocols (IP), such as IP6, the problems associated with interoperability will ease. This will also help ad hoc coalitions to quickly come together to address a specific intervention. 

With unmanned aircraft being developed in even greater numbers it is possible to see short duration, smaller and dedicated platforms being launched to help link up units whose ground-to-ground connectivity has been disrupted by terrain or the presence of buildings. These platforms could remain airborne for many hours and provide the kind of short-range, temporary communications backbone and services that would support ground manoeuvre.

Operating at slant ranges of 1km-2km and with agile beam-forming antennas, the link budgets required to move data at 54Mbps could be maintained for the period of a patrol or local intervention on the ground. But that would be a low altitude for a manned aircraft operating in close proximity to the battlefield.

Reduce civilian casualties

Throughout the last 50 years technological advancements have given military leaders increased military capabilities to affect command and control over the forces under their command. As those operations inevitably focus on the needs to reduce civilian casualties and deliver precise effects the imperative to deliver real-time imagery around the battlefield will increase.

This is where the convergence between contemporary civilian applications on the move and the needs of the military will occur. While the next generation of CNRs may evolve from the current system to protect the investment, there are already possible uses of wireless-based increments that can deliver real-time image services on the battlefield which cannot be ignored.


Wireless link budgets

Estimating the link budgets for wireless systems is relatively straightforward. To compute the link budget the total free-space path loss of the signal must first be calculated. The following formula provides the answer:

Total path loss (dB) = 92.45+20Log10F + 20 Log10D
Where: F is the Frequency in GHz D is the distance between the two nodes in Km

For a connection between two points over a distance of 1km this gives a total path loss, irrespective of terrain or signal attenuation, through buildings of 100dB.  At 2km this increases to 106dB and at 4km the total free-space path loss is 112dB. Using a low flying manned or unmanned aircraft that needs to be kept out of range of any surface-to-air threats could immediately cause the total path loss to increase to 109.5dB for a platform at 3km (10,000ft) or to 120dB for a platform at 10km (30,000ft).

The calculated figure for the total free-space path loss then needs to be entered into the link budget formula.

The final link budget for this 1km scenario ensures that the link operates with a little margin. If the range were to double to 2km measures would have to be taken to either increase the transmitter power or the gain of the antennas. Not a great deal can be done about the cable losses other than to make sure the connectors are in a really good state. Path losses are a direct function of range. So to maintain a link budget that exceeds, say, +5 dB, adjustments to transmit power and antenna gain are required to offset the 6dB loss for each doubling of the distance. For relay applications using aircraft platforms to provide the beyond line of sight applications the gain of the antenna on the aircraft would be crucial to maintain suitable link budgets.

• Dr Dave Sloggett is an independent academic, author and freelance writer specialising in irregular warfare with over 20 years of experience in communications systems.

Written by Wireless magazine
Wireless magazine

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