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GNSS to Enhance Military Connectivity By Phil Froom Rockwell Collins UK Limited


For many years the Western world has been reliant upon the US GPS NavStar (Navigation System with Timing and Ranging) constellation as its space based satellite navigation system, either using the open C/A code (SPS) signals for civilian users and non GPS MOU countries, or the highly protected P(Y) Code (PPS), available to those nations who are authorised under the GPS MOU agreement to access the encrypted service.

As the world’s armed forces began to adopt GPS (some much faster than others) there were a number of statements made by senior NATO officials that their forces would not become ‘GPS Reliant,’ but would use GPS as an “aid to navigation”. However, as GPS became an increasingly reliable global 24/7 capability, our Armed Forces have become widely reliant upon GPS for not only weapons delivery, but also position, navigation and critical timing (PNT) across defence.

As with all technologies, there are positives and negatives associated with the use of GPS, and these can vary depending upon how GPS is used relative to positioning, navigation or timing. On the one hand, GPS is now available to almost everyone on earth. The early ‘dithering’ of commercial C/A Code has been removed, and accurate and accessible GPS signals are now used in all walks of life, from tracking domestic pets, to delivering nuclear weapons. But whilst availability of GPS signals are a great positive to society, the denial of GPS serves both the criminal element of society, and our enemies.

Despite the current widespread use of GPS, sole reliance upon the US GPS constellation by both civilian and military users is about to become a thing of the past. There are multiple satellite navigation systems in the process of launch and completion; two new global satellite navigation constellations, two regional or augmentation constellations and another existing but enhanced constellation, all soon to be available to global or regional users. Of course we are interested here in military use of what has now become commonly referred to as Global Navigation Satellite Systems (GNSS), so what are these new constellations, and how will they enhance or change our mission?

Without getting into detailed constellation specifics, the first thing to consider is that these combined satellite navigation systems will increase the number of available navigation satellites from the current 31 operational GPS satellites available, (granted there is the GLONASS constellation too if the user wishes to use it) to approximately 126.

The advantages to military users are evident – since one of the current major issues with GPS can be the accessibility of signals when in forested or urban operational areas, since both are prone to line of sight denial (the basic inability to see the satellites) and the attenuation of signals in the case of dense wet foliage, both of which cause GPS denial.

Of course, the above does not even take into account hostile denial of GPS by our enemies. GPS jamming is now endemic, even in civilian circles, as small low cost

GNSS Technology Provides Connectivity

GPS jammers are available on-line to anyone with a wish to buy one (Personal or Privacy Protection Devices (PPD) retail from around €25.00) and although these are normally being used for non-military denial (toll jumping, high value asset theft and own vehicle invisibility) their effect on not only their intended target, but on civilian infrastructure (airports especially) make the threats posed by GPS jamming abundantly clear.

In parallel, spoofing can perhaps be more dangerous for operational troops than jamming. When jammed, a good military GPS receiver will make that clear, but spoofing can often take place without the user being aware, and is aimed at intentionally displacing the user, by spoofing his GPS receiver into believing it is actually in a significantly different location (achieved by broadcasting false

GPS signals to SPS receivers). The dangers are obvious. For navigation, the outcome can result in friendly troops erroneously navigating into danger zones, such as mine fields or dangerous terrain, and in the case of weapons (as proven in recent conflicts) friendly artillery, bombs or missiles striking the wrong targets, be they civilian or blue forces, with obvious catastrophic results.

But in the near future Military GNSS receivers will provide troops with significantly better potential to receive the combination of GPS, Galileo, GLONASS, Beidou (and in certain regions IRNSS and QZSS) signals appropriate to their mission. In addition, new services are being transmitted on different frequencies providing further redundancy and making effective jamming and spoofing harder. The use of multi-frequency GNSS will improve the ability of receivers to both navigate and conduct their mission more effectively and safely. The multitude of new navigational satellites and signals will immediately mitigate the terrain denial caused by foliage and buildings, but will also offer new opportunities to mitigate intentional denial via spoofing and jamming.

So future military procurers now need to be changing their URDs and SRDs from the use of the phrase “must include GPS” to “must include Global Satellite Navigation System, or must include GNSS” since we are no longer limited to single constellation navigation and we must begin to look to this new and improved capability to support future missions. Not only do these new and enhanced constellations offer the military user significantly more satellites, but they offer some significant options with regard to both procurement and operational use.

Many current military users are limited to C/A Code (GPS-SPS) GPS (unencrypted and extremely vulnerable to Spoofing and of course Jamming). In many cases vulnerable off-the-shelf receivers are in use (sometimes without the resulting mission risk being identified or understood). Some users have access to GPS P(Y) Code (GPS-PPS) GPS (fully protected from Spoofing and to a certain extent, Jamming). But if the procurer is not a signatory of the US GPS MOU, they will not be granted P(Y) Code, currently limiting them to some form of commercial and extremely vulnerable C/A Code open signal.

Even those countries entitled to P(Y) Code, face certain inevitable challenges. The procurement of P(Y) Code SAASM based GPS must be conducted under strict US guidelines. Until fairly recently only via Government to Government FMS procurement, this brought long time delays in obtaining hardware, drove cost and limited some users to how they operate and integrate their GPS hardware.

Yet in the near future, with so many new GNSS satellites and services available, the capabilities desired by the military user community can now be addressed in a variety of ways. There will always be a need for high level protected and encrypted GPS by the US and its Allies. Today the encrypted signal is provided  via a Selective Availability Anti Spoofing Module (SAASM), tomorrow it will be provided by the new and already operational for test, M-Code and the Galileo equivalent, the Galileo Public Regulated Service (GAL-PRS). So for high end weapons and high value systems, these individually or together will almost certainly remain the chosen solution by NATO and its Allies.

But how about the infantry soldier in the field, does he really need such a high level of protection, driving integration costs and crypto administration challenges, or can we address his needs in a different way – whilst still keeping him and his comrades safe of course? Well, with the new GNSS satellites and a new generation of military GNSS receivers we can. Instead of providing a soldier with a fully encrypted GPS or GNSS receiver which could be larger, more power hungry, need regular crypto upgrades and have storage and handling issues, we can now provide him with a Multi Constellation Open Service (MCOS) military GNSS receiver, which instead of simply receiving GPS signals, can access, GPS,  Galileo, Beidou, GLONASS and also any available regional services. The receiver can now sample multiple open signals from each constellation (say two from GPS, one from Galileo, one from Beidou and one from GLONASS constellations) and with intelligent processing, can not only ensure that it is not being spoofed, but also provide a degree of protection from Jamming, since jamming multiple GNSS constellations, will prove much more difficult than simply jamming one, and also makes the jammer extremely vulnerable. Beyond the use of multiple GNSS signals, our soldier now has numerous Open Service GNSS satellites to navigate from, protection from spoofing –since his new system is constantly comparing the output of multiple satellites simultaneously across two or more constellations, and is looking for any deviation potentially caused by spoofing. The system will also employ intelligent Digital Signal Processing to constantly assess the integrity of those received signals, and by use of advanced technology, built in to receivers, such as Rockwell Collins’ Receiver Autonomous Signal Authentication (RASA) we are able to protect him from spoofing, and to a much greater extent from jamming, and all this with no crypto, ITAR, costs or handling issues.

So having solved the user’s ability to receive a reliable and usable GNSS solution, what else should our future procurers be looking for in a next generation military GNSS receiver? I think the answer here has to relate to the credibility and reliability of this GNSS solution. Receiving GNSS signals is possible with a wide variety of current civilian receivers, many with a wide variation in quality and integrity, but although they are receiving some form of GNSS signal, can we be sure it is an Assured signal (can we trust it and walk into harm’s way, relying upon it)? The answer with many cheaper civilian receivers is (or should be) no. These receivers are using a combination of direct, reflected and refracted signals, which will tend to produce unstable and patchy navigational solutions, as the receiver relies upon one, then another and another reflected signal from adjacent buildings, or from other signal interdicting objects, the result being an inconsistent, confusing, and unreliable solution being presented to the user.

The use of a high assurance receiver, which will process the signals it sees and use only those which are confirmed to be of consistently high quality, reliability and accuracy, will ensure our user will always have the most accurate and reliable signal to navigate by when engaged in combat operations. But assurance is also critically important when we consider the origin of our GNSS receiver itself. As military users, we are becoming more and more aware of the Cyber threat to our communications and electronic systems. Since GNSS is a radio based system, the threat here is in no way reduced, but can now be greatly mitigated if we ensure we deploy the correct devices.

Some time ago a high profile NATO user discovered that a military system which had been procured and cleared into service, contained a GPS receiver produced in an unregulated foreign nation, which was found to have a ‘back door’ built into its code. The intention was unknown; was it simply that the software coder left himself a back door in case he locked himself out, or could that back door have been intentionally placed there to later be exploited electronically by our enemies, potentially in time of conflict with the intent to disrupt or deny this system from use? The truth in this case (as officially released) was that we simply do not know.

But if we look at where the majority of low cost GNSS receivers are produced, and the fact that we have no visibility of the code being run, do we really want to insert these GNSS receivers into our radios, command and control systems or weapons? I would suggest the answer here should be No. Yet even such key components of military systems as the navigation element are still being procured by many nations on a cost rather than capability or security basis.

Perhaps our final consideration when looking to procure our next generation Military GNSS receivers is the constant integration challenge. We have noted that there are many hundreds of GNSS receivers available even today, from a variety of manufacturers from across the Globe, each with their own capability, design, form factor and software. For commercial users this can be a very positive thing, as it keeps costs down and allows receivers to be purchased to meet bespoke high volume hardware form factors and target costs on a month by month basis.

However this is quite the opposite to what military users need, since they will procure Military GNSS systems for a platform or programme (AJAX in UK or A-PNT in US for example) which is expected to be in service for in excess of ten years. It may be a phased procurement, and this solution needs to meet both the needs of today’s fleet, but also that of tomorrow. These users also need an Interface Control Document (ICD) they can rely upon to be stable across the platform or programme lifetime… But since most commercial receivers are driven by commercial timelines and needs, their own ICDs (if one exists at all) will be driven by the next big commercial phenomenon, not by a necessarily long standing military supply and support requirement. The result being that when they look to tranche two of their programme, the form factor from that supplier will likely have changed, and the ICD too… once again, driving integration costs, and programme delays.

To mitigate the issues surrounding availability, integrity, spoofing, jamming, Integration, Cost, handling and political drivers, a new family of next generation Military GNSS receivers are being designed and produced under a cooperation agreement between Rockwell Collins and QinetiQ.

This family of GNSS receivers has been designed specifically for military and high value Government users and platforms and will provide the procurer with multiple options with regard to how he meets the needs of his user community. Although the family will include more than one form factor, these form factors have been designed to meet specific platform requirements and to offer a variety of navigation solutions and levels of protection to the user, from Multi-Constellation Open Service (MCOS) GNSS, through to high level solutions offered currently by SAASM or other security regimes, and tomorrow by M-Code and other secure services.

Based upon the experience and expertise of these two satellite navigation and advanced technology providers, the future procurers and users of military GNSS can be sure that the receivers available to them for tomorrow’s military systems, will be of proven design assurance (being both designed and manufactured in EuMEA) of high signal integrity, are highly protected from spoofing and jamming and will provide both mission flexibility and longevity of capability of the platforms and programmes within which they will be installed.

They will provide common form factors and common ICDs, designed specifically for military use (so meet the high environmental norms demanded) and will employ high levels of Digital Signal Processing, both to ensure the integrity of the received signal, but also to mitigate Spoofing and Jamming. They will deliver assured position, navigation and timing whilst achieving a low size, weight and power consumption commensurate with some of the most demanding applications, from use in equipment carried by dismounted soldiers to embodiment in complex platforms and compact weapons.

It is hoped then, that the provision of a new generation of protected military GNSS receivers, and the further enhancement of navigational availability and resilience by use of multi-sensor integration (e.g. use of inertial MEMs sensors) and the integration of advanced anti-jam controlled radiation pattern (CRPA) antennas will eliminate the current dangerous practice of deploying commercial receivers in the battlespace.




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