SIMPLY PUT
Software-defined radios (SDRs) are systems that can change their radio emission and reception functions through programming that can be modified and updated. They can change the type of modulation and encoding, or the frequency band and the intended effect, from data transmission to jamming, or change from reception to sens- ing. The new tactical radios being procured by the U.S. military are SDRs. Technology advances faster today than it did during the procurement of the current voice (Single- Channel Ground and Airborne Radio System (SINCGARS)) or data (Enhanced Position Location Reporting System (EPLRS)) radios that were the mainstays of the Army for many years.
To explain simply the difference between the newer, software-defined radios and the older, hardware- defined radios, consider a smartphone. If you had a truly software- defined cellphone, it would have required only a software update to progress from 2G to 3G, 4G or LTE. However, current cellphones are hardware-defined and use hard- coded modulation techniques, such as LTE, Wi-Fi or Blue- tooth. The original iPhone, for example, worked only with 2G and is not upgradable.
There are good reasons for manufacturers of smartphones to do this. One is profit. If your phone could be upgraded to the latest and greatest with nothing but a software update, there would be little reason to go out every year or two and buy a replacement. But as compelling as profit may be, so is the speedy advance of technology: Cram- ming all that tech into such a small space requires sacrific- es. The chip that runs the phone—its computer brain—has to be very small. Technological advances make it possible to produce smaller and faster chips that significantly in- crease speed with each new model.
However, what is true of consumer electronics isn’t neces- sarily true of military electronics. For tactical users, there are several reasons for wanting to be able to change the signaling software or waveform. These include corrections for security, improvements in efficiency and changes to adapt to new technology, among others. Military radios are expected to have a life span of 10 to 15 years for a vehicular model and five to 10 years for a portable one. And they don’t have to fit in a shirt pocket. Plus, improve- ments must be made in parallel with all other military radios at the same time to maintain interoperability. Not so with smartphones, despite their expense. Big changes to the technology require replacement of the entire phone.
TACTICAL SMARTPHONES
Soldiers used SDRs during Network Integration Evaluation 15.2, one in a series of Soldier-led evaluations designed to further integrate and rapidly advance the Army’s tactical communications network. (Photo courtesy of the Program Executive for Office Command, Control and Communications – Tactical)
The software communications architecture (SCA) is a specification that defines a software architectural frame- work for management, control and configuration of an SDR. Although it is often misunderstood to be an operating system (OS), like Windows, the SCA specifications are ac- tually only an explanation of what the manufacturer’s own OS needs to include and be able to do. The specifications tell the manufacturer how the software they develop using the application program interfaces (APIs) must interact with the waveforms’ software. Both—the SCA and API speci- fications and the actual waveform software—are mature technologies available for the manufacturers to implement.
SDRs themselves can be thought of as a collection of components that are commanded or employed by the software. Examples include GPS, Ethernet, encryption and even the processors. Radio services are persistent libraries of software code that provide common software functions to the waveforms. APIs are standardized so that every manufacturer’s radio has the same exact protocols;thus, the different software packages can talk to each other in the same way.
—MR. ALAN CLAYTON (LTC, USA, RET.) and MS. ASHLEY BUZZELL
ASC.ARMY.MIL
93
SCIENCE & TECHNOLOGY
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