Communications
SOFTWARE-DEFINED RADIO SIGNALS A REVOLUTION
Byline: Gordon Arthur / Hong Kong
Military communications have come a long way from heliographs, flags and smoke signals. The past century has witnessed a phenomenal explosion in communication technologies. Less than a century ago, the military was reliant on pigeons amongst other methods! Radios have revolutionised communications, and that process is now continuing even faster with the advent of the digital age.
The ultimate aim of communication is to provide improved situational awareness and to enhance command and control. The buzzword for a number of years has been network-centricity, and radios are critical to this concept. The sector is big business too. Last year some USD17 billion was spent globally on military communications.
Before examining trends in modern radio system technologies, let us look quickly at the types of radios used within armies. Very-high frequency (VHF) radios operate in the 30-300MHz range, a band rarely used by the commercial sector. However, the downside is that VHF is limited to line of sight (about 8km for a dismounted soldier). VHF radio offers vertical connectivity to a headquarters but it does not horizontally link section/squad members. This gap is filled by the ultra-high frequency (UHF) radio that is generally smaller and handheld (often referred to as a personal role radio). The possession of such radios by every member in a fire team has greatly enhanced small-unit tactics.
However, the backbone of the tactical network is still the high-frequency (HF) manpack radio. In fact, HF has undergone a renaissance during recent combat operations in Afghanistan and Iraq where satellite communications are finite and congested. HF works in the 2-30MHz band and it offers beyond-line-of-sight application by bouncing signals off the ionosphere. HF radios are commonly used on foot patrols now because they are lighter and have increased data transmission rates. Another advantage is the use of Automatic Link Establishment (ALE), which means the average soldier without any great technical expertise can operate HF radios.
Software-defined radio – what is it?
Modern radios can transmit not only voice messages, but also data and imagery with amazing speed. In fact, software-defined radio (SDR) is opening up new realms of possibility in terms of combat radios. SDR technology, in its simplest terms, is a melding of computer and radio. Radios previously had a narrowly defined set of inbuilt functions that were constrained by their hardware. However, SDR makes use of multiple software layers to perform a variety of tasks in much the same way that a desktop computer can do word processing, internet browsing and database management depending on the user’s preference. SDR uses waveforms or software programs to control functions (e.g. frequency range, frequency hopping). In the following attempt at trying to demystify SDR, the author acknowledges his indebtedness to a series of informative articles by John Keller, editor-in-chief of Military & Aerospace Electronics.
The SDR operating system employed by the USA is called Software Communications Architecture (SCA) and this enables SDR waveform software modules to share information with each other. The encrypted waveforms are reprogrammable and flexible. For example, the Single-Channel Ground and Airborne Radio System (SINCGARS) could be loaded onto an SDR, but if a different function is needed (e.g. combined voice and data), a more suitable waveform could be loaded instead. Thus, SDR offers huge flexibility based on just a single hardware platform. An important waveform is the Soldier Radio Waveform (SRW), while others include the Wideband Networking Waveform (WNW), Mobile User Objective System (MUOS) and Tactical Targeting Network Technology (TTNT), plus many more are around the corner. For instance, SRW soldier network connectivity, while WNW provides long-haul connectivity.
SDR advantages
A key benefit of SDR is interoperability between legacy and modern systems. It is an expensive proposition replacing the entire radio inventory in an armed force, so it is important that new and old systems can work compatibly side by side. Radios in some countries might even date back to the Vietnam War era. At one time the US Armed Forces possessed 200 different radio types, none of which were designed to interact with each other. The ability for the US Army, US Marine Corps and US Air Force to communicate easily is of course desirable and SDR offers this possibility. SDRs adapt to a range of protocols so that different models and networks can communicate. This is important because militaries are increasingly working within large-scale multilateral operations such as the International Security Assistance Force (ISAF) in Afghanistan. Getting radios to interoperate is important not only within a military and its allies, but also with civilian agencies such as the police too.
The interface between radios is also improving, meaning an operator does not need to be a technical expert. The latest technology does a lot of its work automatically without requiring user input. For example, radios can act as communications repeaters and create wireless data networks whilst on the move.
Another benefit of SDR is the ability to squeeze a lot of capability into one compact package. One system can now do a job that beforehand required several radios. For example, data about infantrymen who have SDRs and embedded global positioning systems (GPS) can be broadcast on a network so that everyone knows where they are. Such a system could even monitor a soldier’s vital signs, and a commander would know the exact physical disposition and wellbeing of his forces.
The lifespan of a military radio is typically 15-20 years, so another huge advantage of the software-based radio is that upgrades can be quickly implemented. This extends a radio’s life cycle since it can be adapted for new technological capabilities and challenges simply through modifying the software.
Today’s customer requires smaller, lighter and faster devices. They need to give more capacity but yet still interoperate with old narrowband systems. SDR leverages embedded computing technology, and builds upon advances being made in digital signal processing (DSP), field-programmable gate arrays (FGPA), software design and software code generation, for example. A typical battery now measures 40mm x 75mm x 75mm and it provides 8-10 hours of life. Radios have progressed from NiCad, through nickel-metal-hydride to the current lithium-ion. Fuel cell technology is another area that will influence SDRs, but this is probably still some ten years away.
Products
A significant SDR product is the General Dynamics AN/PRC-154 Rifleman Radio that is cutting edge thanks to it being the first military user of Mobile Ad Hoc Network (MANET) technology. This means the system is self-configuring; its intrinsic connectivity allows signals to hop from one AN/PRC-154 to another until a gateway to a satellite or the internet is gained.
The AN/PRC-148 Multiband Inter/Intra Team Radio (MBITR) from Thales Communications is the most widely used handheld tactical SDR in use with NATO. This April Thales Communications is due to start production of the second-generation MBITR2 multiband inter/intra-team military radio. It simultaneously integrates two channels – wideband SRW tactical internet and voice network connectivity with a narrowband channel. Thales is positioning the MBITR2 as a cost-effective upgrade for the AN/PRC-148.
Another popular type is the Harris Corporation Falcon III AN/PRC-117G that is NSA Type 1 certified. Australia ordered AN/PRC-117G wideband and AN/PRC-117F multiband manpack units to replace its legacy Raven systems, as well as AN/PRC-150(C) manpacks plus amplifier adaptors to mount AN/PRC-152 units in more than 1,000 armoured vehicles. More recently the Antipodean country received Falcon III AN/PRC-152(C) multiband handheld tactical radios that support SINCGARS, transmit voice and data messages and have embedded GPS receivers.
Interestingly, different ‘types’ of war impose different radio requirements. Defence Review Asia spoke to Faisal Munir, a regional sales director from Harris Corporation, at the IDEAS defence show in Karachi last year. He said: “Pakistan is an important market. It has one of the largest armies in the world plus it’s doing a lot more counterinsurgency/small-unit tactics.” Indeed, the Pakistani military has undergone a marked change in focus necessitated by its counterinsurgency against Islamic extremists, instead of its anticipated massive armoured confrontation with India. At the show, Harris Corporation was promoting three products in particular – the RF-7800H Falcon III, handheld RF-7800M-HH and a ruggedised RF-3590 tablet – suitable for counterinsurgency operations.
American programmes
The US Army’s target is 581,000 SINCGARS radios, and most have already been fielded. They are not software-defined but with so many in service, new SDRs obviously need to interoperate with them. More than 300,000 were acquired after 9/11, meaning they are still relatively new. SINCGARS is produced by ITT Exelis, with the current model distinguished by the inclusion of JTRS Enhanced Multiband (JEM) technology from Thales.
SDR must now be considered a relatively mature technology. The concept was first exploited in General Dynamics’ Digital Modular Radio in 1998, but in the past few years just about every new radio introduced has included some form of SDR technology. It has moved on from basic enabling technologies towards development of more efficient waveforms and systems, which should lead to cost reductions and greater availability for other nations. The commercial sector has not pursued SDR since it prefers more disposable platforms.
The USA’s Joint Tactical Radio System (JTRS) was supposed to set the benchmark in multipurpose communications. However, the US Army cancelled the Boeing-led JTRS Ground Mobile Radio (GMR) programme in October 2011 after spending billions of dollars. The major problem was that JTRS became unwieldy and unaffordable due to its complexity and over-ambition. Therefore, the JTRS was axed in favour of finding an off-the-shelf product of lower cost, reduced size, lighter weight and reduced power consumption.
JTRS and its cancelled GMR component has been reorganised under the Joint Tactical Networking Center (JTNC), the organisation now responsible for managing SDR technology and waveform development within the US military. The US Army is pursuing the JTRS Handheld, Manpack, Small Form Fit (JTRS-HMS) programme. General Dynamics is prime contractor and the HMS family includes the AN/PRC-154 Rifleman and two-channel AN/PRC-155 manpack. The army will also rely on the Mid-Tier Networking Vehicular Radio (MNVR) to replace the GMR and to extend communications from the brigade/battalion level down to companies and platoons. This is shaping up as a fierce competition between General Dynamics, ITT Exelis, Harris, Raytheon and BAE Systems (with its Phoenix family), with a request for proposals issued on 28 August 2012.
Future directions
What does the future hold for radios? SDRs are likely to grow smaller. For example, the Harris AN/PRC-152A handheld radio now has the type of capability that a manpack once had. As technology improves and devices become smaller, SDR could be embedded in devices such as wrist-mounted or helmet-mounted displays. Researchers are exploring how devices can be tied together on the battlefield so that individuals can access and extract useful data. Future networks will be able to display in real time where friendly and hostile forces are located, a situational awareness capability that only battle management systems (BMS) can currently achieve. Another potential use may be to map nuclear, biological and chemical (NBC) agents, or listing the availability of artillery strikes and air support assets to troops on the ground.
The next step after SDR is smart, computer-controlled radios that automatically establish links in real time. This is called cognitive radio, and it will rely even more heavily on computers. Cognitive radios have inbuilt intelligence to automatically monitor the environment for elements such as interference or electronic jamming, and to make decisions about the best way of operating. They could choose less congested areas of the spectrum or create an ad hoc network to utilise clear frequencies, for example. However, such technology is likely to be exploited commercially before it makes its way onto the military scene. Another challenge of cognitive radio is how to prioritise messages so that the most urgent can be transmitted quickly while less important ones wait in line.
Another trend is to use more commercial off-the-shelf (COTS) devices tactically. Considering the lightning speed at which the consumer market is moving, this approach holds promise and the interplay between tactical radios and mobile devices is certain to explode. In the future, radios may act as a secure wireless node that supplies internet connectivity to a host of other computer and phone devices.
An interesting area of research by the US Air Force Research Laboratory (AFRL) at Wright-Patterson Air Force Base in Ohio is communicating via infrared lasers so as to evade enemy interception. The system is virtually hack-proof because the enemy would need to be directly in line with the narrow 1.5-micron beam. An optical laser beam can carry thousand times more information than wireless signals. Stationary small-scale systems have been used at Bagram Air Base since the mid-2000s, while ITT Exelis is developing a 19km-range ship-to-shore system for the navy. Such a system would almost complete the communication circle begun by such optical systems as the heliograph!
