Communication systems have always been a strategic target in times of conflict, but Modem 21 is one solution that has never been beaten in the fight to protect satellite communications against jamming. Now a NATO standard, Modem 21 technology has consistently drawn on the latest innovations to adapt to the specific needs of each customer.

During World War II, British and German experts waged a secret war to encrypt the communications of their respective armies and crack the codes of the other. Meanwhile in France, attempts by the German occupying forces to jam the frequencies used by the BBC still resonate in our collective memory.

Communications as a target

In an armed conflict, disrupting the enemy’s communications has always been a strategic objective, and jamming is now considered an act of war. With new technologies and the need to conduct operations further from home, it’s more important than ever to ensure that the channels of communication are permanently open, seamless, secure and resilient to attack.

Modem 21 is part of a long heritage of anti-jam systems for satellite communications. The story began in 2004, when the French defence ministry expressed the need to protect its strategic satcom systems so that commanders could stay in touch with the Navy’s front-line warships. The idea of an adversary jamming communications between France and its aircraft carrier was simply unthinkable.

An anti-jam modem

Jacques is an engineer. He figured that the way to prevent deliberate jamming of satellite communications was to keep switching frequencies, quickly and often, using a sequence that would be impossible for anyone else to replicate. With such a system, he argued, communications couldn’t be jammed because no one would be able to find them! The technique had already been used for radio, but it would need to be specially adapted for satellite communications, and all users on the same network would need to be synchronised. So Jacques invented a revolutionary waveform protocol, which is still the keystone of the disruptive technology used in Modem 21 today.

This highly resilient solution was designed to be compatible with all existing geostationary satellites, so there was no need to modify their payloads or put new ones into orbit. It quickly attracted interest from other branches of the military and was adapted to meet the requirements of forces deployed in remote theatres of operations so that commanders in the field could communicate securely with chiefs of staff in France.

Modem 21 scored a decisive success in 2006, when the technology was adopted to protect NATO satellite communications and became an official standard under STANAG 4606. This was Edition 1 of STANAG 4606 for low-data-rate communications.

Edition 2 soon followed, with faster data rates, but a real breakthrough came in 2008 with the Yahsat project for the United Arab Emirates. The Emirates already saw Modem 21 as a tried-and-trusted NATO-standard solution, but they wanted more. To dramatically increase data rates and expand the range of services and use cases, they realised that Modem 21 needed to incorporate IP, packet switching and other internet technologies.

Thales stepped up to the challenge with a new iteration of Modem 21, which was tested in the field by Yahsat and subsequently transcribed into Edition 3 of the NATO standard in 2014.

Unstoppable innovation

Since then, the dynamic for innovation has been sustained. Based on the needs expressed by the armed forces, Thales has consistently devised innovative solutions, and after rigorous field testing and validation, incorporated them into a constantly evolving, common international standard. To meet the specific requirements of each customer, each country and each branch of the military, Modem 21 has had to adapt. Today it is available as a hardened, shockproof, sandproof unit. The issues of portability and mobility have been addressed. And the system is ready for as-is integration on board UAVs and fast jets.

The latest iteration of STANAG 4606, Edition 4, offers very high data rates — up to 100 Mbps. Whether transmitting voice, images, video, maps or specialist application data, Modem 21 pre-processes the signal before it is amplified and sent to the satellite. The satellite simply bounces back the signal to a receiver on the other side of the world, also fitted with a Modem 21. And no one has yet succeeded in listening in or disrupting a signal as it travels between two terminals equipped with Modem 21!