From The Editor | May 23, 2024

Secure, Adaptive, And Intelligent: The Future Of Military SDR Applications

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By John Oncea, Editor

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Software defined radio plays a crucial role in the military’s communication infrastructure. Let’s look at ways the military might use this technology in the future.

Software defined radio (SDR) is a radio communication system in which components traditionally housed in analog software – such as mixers, filters, amplifiers, modulators/demodulators, and detectors – are, instead, implemented via software.

A computer with a sound card or other analog-to-digital converter and an RF front end are basic system requirements for SDRs which can receive and transmit a wide variety of radio protocols based on the software used. This technology is utilized by the military and for cell phone services because of its ability to manage various radio protocols in real time. SDRs are expected to one day become the dominant technology in radio communications, along with software defined antennas.

A Brief History Of SDR

The concept of SDR emerged in the 1970s-1980s from the combined efforts of various research groups in the private and government sectors of the U.S., primarily the U.S. Department of Defense Laboratory and a team at the Garland, TX Division of E-Systems Inc., writes Springer Link.

It was the E-Systems (now Raytheon) team that, in 1984, coined the term “software radio” to refer to a digital baseband receiver that provided programmable interference cancellation and demodulation for broadband signals. In the same year, Ulrich L. Rohde’s department at RCA developed the first SDR while working under a U.S. Department of Defense contract, using RCA’s COSMAC chip, according to ComSoc.

“In 1991,” writes Spring Link, “Joe Mitola independently reinvented the term ‘Software Radio’ (SR) in cooperation with E-Systems as a plan to build a true software-based GSM transceiver. The SR platform essentially processes almost all the transceiver algorithms as software for a processor (including) nearly all layers of transmission.”

SDR implementations initially focused on military applications because of their ability to transmit a wide range of radio waveforms and protocols through software programming. Over time, SDRs evolved to support broader bandwidths, higher data rates, and multi-channel architectures, driven by advancements in digital signal processing, hardware design, and integrated circuit technologies.

According to NI (now part of Emerson), SDRs were initially met with skepticism but gradually became the de facto industry standard across various domains, including military communications, signals intelligence, electronic warfare, test and measurement, and spectrum monitoring. Today, SDRs are a dominant technology, enabling frequency-agile intelligent communication systems with increased flexibility and efficiency.

More Than “Voodoo Magic”

SDR is popular with amateur radio enthusiasts who use the technology for radio communication, satellite tracking, and signal decoding. Ham radio operators, especially the younger generation with ECE/CS degrees love the technology but parts of the older generation frown upon SDR as “voodoo magic” with too many computer/network dependencies.

Ham radio operator and professional technologist Onno Benschop (VK6FLAB) says on his podcast Foundations of Amateur Radio (April 28, 2019)that describing SDR as “traditional radio where all the components are implemented in software” is similar to “explaining how a radio works by waiving your hands and saying: here is magic.” Benschop says that how SDR works is altogether more interesting and thought-provoking than that.

“You may have heard that a Software Defined Radio hears all frequencies at the same time,” Benschop says. “Essentially, it's a voltmeter connected to your antenna, spitting out measurements as fast as it can for processing by a computer. The waveform that comes from those antenna voltage measurements represents all of the RF spectrum and it's just the beginning of what you can do next.

“In the same way that my voice is made up of lots of different parts, all played together, the RF spectrum is made up of the local broadcast stations, the local TV stations, mobile phones, garage remotes, Roy on the 7130 DX net, this podcast on your local repeater, all at the same time, all played together, to make the waveform that represents the measurements you make at the base of an antenna. Unlike a traditional radio, which has to work hard to filter out undesirable information, a software defined radio can filter out information by just deleting those measurements you're not interested in.”

While Benschop is interested in SDR because of his love of amateur radio, defense agencies worldwide seeking advanced communication solutions are utilizing it as well to the point is emerging as a vital component in modernizing military communication systems.

SDR And The Military

The military has used SDRs for years for a variety of applications, including:

  • Battlefield communications
  • Intelligence, surveillance, and reconnaissance (ISR)
  • Military air traffic control (ATC)
  • Radar control
  • Over-the-horizon communications-on-the-move (COTM)
  • Command and control system management
  • Satellite communication

Because they are built with built with open architectures, SDRs allow for rapid adaptation to enemy capabilities and efficient introduction of emerging technologies. Standardized radio hardware can be readily upgraded with new waveforms, enabling U.S. forces to communicate across services within the Joint All-Domain Command-and-Control (JADC2) environment. Avionics adds that running multiple waveforms simultaneously ensures secure communication without being spied on by opposition forces.

The military also values the technology’s ability to offer secure communications in conflict zones. This was made evident when Ukrainian forces were able to target radio transmissions from commercial-grade radios and cell phone calls used by poorly trained and equipped Russian soldiers. Secure SDRs provide greater mobility, survivability, and protection against electronic warfare systems as well.

Finally, according to Military Embedded Systems, SDRs can engage in spectrum jamming and handle syncronized ground and airborne radio networks, improving information sharing and facilitating shared situational analysis.

In summary, SDRs are critical for secure and adaptable military communications, and their future applications extend beyond traditional radio functions. They enhance situational awareness, security, and interoperability across services and platforms.

SDR And The Military – Future Uses

Currently, SDRs serve as network-control devices and communication repeaters due to their flexibility, adaptability, and ability to support a wide range of waveforms and protocols. Those same attributes are expected to lead to continued use of SDRs by the military in the following ways:

  • Interoperability and Legacy System Integration: One of the key advantages of SDRs is their ability to support multiple waveforms and communication protocols through software updates, enabling interoperability between different radio systems. This will allow the military to seamlessly integrate new SDR systems with existing legacy radio hardware, reducing the need for costly hardware replacements and enabling a gradual transition to modern communication technologies.
  • Cognitive and Adaptive Radio Capabilities: Future SDRs are expected to incorporate cognitive and adaptive radio capabilities, allowing them to dynamically sense and adapt to the radio frequency environment, optimizing spectrum usage and mitigating interference. This will be particularly useful in contested and congested electromagnetic environments, ensuring reliable and secure communications for military operations.
  • Secure and Jam-Resistant Communications: SDRs can be designed with advanced encryption and anti-jamming capabilities, providing secure and jam-resistant communications for military operations. This will be crucial in protecting sensitive information and maintaining communication links in hostile environments.
  • Integration with Emerging Technologies: SDRs can be integrated with emerging technologies such as artificial intelligence, machine learning, and 5G networks, enabling advanced capabilities like intelligent spectrum management, automated waveform adaptation, and high-speed data transfer. This will support the military's need for real-time situational awareness, data-driven decision-making, and high-bandwidth applications.
  • Satellite Communications and Navigation: SDRs can be used for satellite communications and navigation, enabling global connectivity and precise positioning for military assets. This will be essential for coordinating operations across different theaters and ensuring accurate targeting and tracking capabilities.
  • Unmanned Systems and Internet of Battlefield Things (IoBT): SDRs will play a vital role in enabling communication and control for unmanned systems, such as drones and autonomous vehicles, as well as the Internet of Battlefield Things (IoBT), which involves interconnecting various sensors and devices on the battlefield. This will enhance situational awareness, improve decision-making, and enable new operational capabilities.

Overall, the flexibility and adaptability of SDRs make them well-suited for the rapidly evolving and demanding requirements of modern military communications, ensuring that armed forces can stay ahead of emerging threats and leverage innovative technologies.