Software-defined radio is key to seamless and effective military communication

Story

October 07, 2015

Stephanie Chiao

Per Vices Corporation

To be ready for modern warfare, military communication on the battlefield needs to be interoperable, adaptable, and fast. Software-defined radio (SDR) is the solution that makes seamless communication on the battlefield possible.

Military radio needs have evolved past basic voice and data communication; the warfighter now requires communication that uses several different frequencies and implements several different protocols. SDR has evolved significantly over the years and is able to cater to these specific needs.

Further, SDRs can be utilized for not only standard two-way communication but can also act as communication repeaters (allowing for different wireless devices to communicate with one another), offer secure wireless nodes, engage with a number of different devices concurrently, and provide very low latency point-to-point wireless links.

What is software-defined radio?

SDR can be defined as a wireless communication device where the receiver and transmitter functionality is changed or modified by software without making any physical changes to the hardware. It was essentially developed with the idea of software replacing radio tuners and filters. This structure in turn eliminates the need for using resistors and capacitors, as software-based filtering algorithms can be used to select specific frequencies. Such a setup still requires a flexible enough hardware platform; today’s designs are ensuring that devices all incorporate this feature.

Although there are different architectures implemented for different SDRs, one high-performance design separates signals from high band and low bands (baseband). Figure 1 outlines the architecture and the steps through the receive chain. The signal is first sampled from the antenna; the analog signal is fed through an RF switch based on the frequency of the signal being sampled. High band is reserved for signals greater than a certain threshold, while the low band is reserved for signals lower than the threshold. Within the respective RF chains (high and low) the analog signal is filtered and divided into “I” and “Q” channels for advanced signal processing on a FPGA or other processor. The high band offers low-noise amplifier (LNA) for weaker signals plus a frequency mixer for desired intermediate frequencies prior to signal processing. The low band offers a varactor circuit to fine-tune the delay between the “I” and “Q” channel. An analog-to-digital (ADC) driver is common between both bands (high and low) prior to the ADC. The ADC will send the data across to the DSP chain within the FPGA using a serial interface.

Figure 1: Receive architecture separating high band and low band.

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On the software side, the algorithms are both downloadable and adaptable over the life span of the radio hardware. This capability makes SDR flexible and ideal for military and defense applications. Today’s SDR is capable of more than data and voice transmission and its popularity is driven by the ability to implement new functionality on the device through software. Before SDR entered the marketplace, functions like encoding/decoding and modulation/demodulation were all hard-wired. That situation has since changed, however, and tasks such as migration, changes in frequencies, and modulation schemes can be performed simply modifying the software.

SDR in military communication

In times of conflict, military communications significantly depends on adaptability, clarity, interoperability, precision, and speed. Deficiencies in any aspect of military communication can have dire consequences. As a result, SDRs have grown to have a significant influence on defense mechanisms as the device provides for not only standard two-way communication, but also offers secure wireless nodes, engages with a number of different devices concurrently, and provides very low latency point-to-point wireless links. Further, SDR can also act as a communication repeater.

The defense industry today is currently engaging in monitoring and communications activities on several different frequencies (HF, UHF, and VHF). They also operate using several different protocols (Bluetooth, CDMA, GSM, LTE, and WiFi). Traditional equipment offers military personnel the ability to tune into only one of the preferred frequencies and support only one protocol. With SDR, however, those on the battlefield are able to monitor and communicate over a large portion of the spectrum while supporting multiple protocols.

Not all SDRs are the same, so it is important to highlight some of the important features of SDRs that enable the most applications. The key features, brief description, and how it relates to end applications are highlighted in Table 1 (on following page).

Table 1: Key specifications of software-defined radios and related applications

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SDRs are highly portable

The weight carried by soldiers has always been an issue, as it can affect how quickly military personnel can move on the ground. As a result, the military has always searched for ways to make equipment lighter and more portable. In the past, soldiers would have had to carry multiple radios on the front lines, which could essentially hinder their movements and capabilities. SDR has been able to reduce size, weight, and power (SwaP) for those in battle, as it is one device replacing multiple radios. This portability is one of the reasons why the defense-industrial complex has increased its spending to obtain new radios developed for the military that are based on SDR.

The future of military SDR

SDR has come a long way since the early days when process technology limited the amount of processing, and therefore the capabilities of SDR. At the present time, SDRs are network-control devices and communication repeaters, but in the future, experts predict SDRs to also act as:

Biological-weapons detector
Chemical detector
Nuclear detector
Area mapper
Tool for situational awareness
Tool to offer data on the availability of support
Tool with the ability to call in an airstrike quickly

With the introduction of SDR, the need for a new military-communications standard was clear. Communication devices on the field needed to be adaptable, clear, interoperable, fast, portable, and light to ensure seamless and effective communication. In the future, SDR is expected to be augmented into cognitive radios that can survey the area, choose the best frequencies, determine and engage in electronic warfare, and set up an ad hoc network on the fly for clear communication.

One platform for SDR technology is the Per Vices Crimson SDR (Figure 2). It operates from DC to 6 GHz with over 1 GHz of RF bandwidth spread across four independent chains (each chain offers 322 MHz of bandwidth). Crimson supports the most common communication frequency ranges: 700 MHz to 950 MHz and 1.7 GHz to 2.6 GHz, while providing the architecture to cleanly sample a signal and/or provide a low-latency link.

Figure 2: The Crimson SDR has four independent receive and four independent transmit chains, each able to carry 322 MHz of RF bandwidth up to 6 GHz.

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Stephanie Chiao is the Product Marketing Manager at Per Vices Corporation, where she is responsible for marketing strategy, technical promotion, and media relations. She brings over eight years of consumer and enterprise marketing experience and has worked with brands including Microsoft, Rogers Wireless, and Torstar Corporation. She holds an Honours Bachelor of Business Administration degree from the Schulich School of Business in Toronto. She may be reached at [email protected].

Per Vices Corporation www.pervices.com