SwRI Flexible Communications Systems and Software-Defined Radio Flyer

Engineers at Southwest Research Institute® (SwRI®) have extensive experience in research and development projects on flexible communications systems and software-defined radio (SDR) for commercial, military, and other government agencies. SwRI has demonstrated the viability of this technology through system simulations and hardware demonstrations.

Engineers in the Communications and Embedded Systems Department have conducted SDR research for implementation of software architectures on general purpose processors and other programmable hardware components.

SwRI engineers have also adapted architectures for specialty applications such as new military radios which require quick-boot SCA (software component architecture) and SDRs that are required to be compliant with the Joint Tactical Radio System (JTRS).

Four-channel WCDMA (wideband code division multiple access) signal, one of the 3G standards, with and without digital predistortion

SwRI engineers have developed model-based design tools for SDR and other radio systems. One set of models describes communications and processing requirements, available hardware, and relevant properties of the alternative software architectures. This tool allows the design space to be quickly searched and incrementally refined in higher payoff regions.

SwRI designed and implemented a reconfigurable satellite terminal that was compatible with an existing satellite network, and transmitted small data packets over a low-bit rate channel to the network. The terminal was extremely small and built with commercially available parts. SwRI engineers developed a waveform that was compatible with the network, and implemented the waveform firmware and integrated it with other devices and an RF module to create a small low-power satellite terminal.

Digital predistortion is an important enabling technology for software-defined radio because it improves spectrum control and efficiency and can support more flexible radio frequency (RF) hardware. Internal research at SwRI has resulted in a set of algorithms for digital predistortion, including linear and non-linear compensation, memory effects compensation, and crest-factor reduction. SwRI engineers have also developed proof-of-concept subsystems for digital predistortion in third-generation (3G) cellular, television, and other broadcast systems.

SDR on a CD demo system – UHF radio using OSSIE SCA (open source SCA implementation: embedded), FSK/PSK/MSK modem, standard laptop, and USB-based RF interface devices

Smart antenna systems can adaptively point the main antenna beam in the direction of a desirable transceiver and can be made to resonate at different frequencies. SwRI engineers have extensive experience in developing smart antennas. Areas of study in specialty antenna research include broadband, electrically small, and low-observable antennas; phased-array radar systems, and antennas with other special attributes.

The SwRI-developed demonstration SDR is JTRS-compliant and is built on a standard laptop that implements the base-band waveform processing and an IF/RF module that plugs into the laptop USB and provides a base-band digital to RF interface. The laptop is booted from a compact disc that includes all of the waveform processing software, the SCA operating environment, the xml domain profiles, and a simple user interface.

In a project for a major aerospace company, SwRI built a tool for analyzing the tradeoffs between costs (size, weight, power, and development time) as the waveform algorithm, performance, hardware platform, operating environment, and software vs. hardware allocation is varied. This tool supported a trade space analysis for space-borne communications systems, utilizing FPGA hardware and leveraging standard communications architectures such as the JTRS SCA.

SwRI teamed with NASA’s Johnson Space Center (JSC) to design and build a prototype SDR that is compatible with the Space-to-Space Communications System (SSCS), a wireless communications system used to carry voice and telemetry data between the space shuttle, the international space station, and the extravehicular mobility unit. SwRI demonstrated integrated operation of the SDR with a network of SSCS flight radios in the JSC laboratory.