GNU Radio: Tools for Exploring the Radio Frequency Spectrum
In addition to the examples discussed above, GNU Radio comes with a complete HDTV transmitter and receiver, a spectrum analyzer, an oscilloscope, concurrent multichannel receiver and an ever-growing collection of modulators and demodulators.
Projects under investigation or in progress include:
A TiVo equivalent for radio, capable of recording multiple stations simultaneously.
A passive radar system that takes advantage of broadcast TV for its signal source. For those of you with old TVs hooked to antennas, think about the flutter you see when airplanes fly over.
Digital Radio Mundial (DRM).
Distributed sensor networks.
Distributed measurement of spectrum utilization.
Amateur radio transceivers.
Ad hoc mesh networks.
Multiple input multiple output (MIMO) processing.
Every revolution has its political issues. Free software for building radios is troublesome to some people. In the US, we've run into opposition from the Motion Picture Association of America and its attempt with the Broadcast Flag to restrict the kinds of receivers that can be built for over-the-air digital TV.
The US Federal Communications Commission has issued a Notice of Proposed Rule Making (NPRM) concerning “Cognitive Radio Technologies and Software Defined Radios”. Several troublesome issues are raised in the NPRM, including restricting the sale of high-speed digital-to-analog converters, requirements for digital signatures or similar methods to keep unauthorized software out of software radio hardware and new restrictions on radios built for the amateur radio market.
Software radio is an exciting field, and GNU Radio provides the tools to start exploring. A deep understanding of software radio requires knowledge from many domains. We're doing our best to lower the barriers to entry.
Resources for this article: /article/7497.
Eric Blossom is the founder of the GNU Radio Project. Prior to his involvement with software radio, he spent many years in the secure phone business. When he's not hacking software radio, you're likely to find him practicing yoga or jujutsu. He can be reached at email@example.com.
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One of the best things about the UNIX environment (aside from being stable and efficient) is the vast array of software tools available to help you do your job. Traditionally, a UNIX tool does only one thing, but does that one thing very well. For example, grep is very easy to use and can search vast amounts of data quickly. The find tool can find a particular file or files based on all kinds of criteria. It's pretty easy to string these tools together to build even more powerful tools, such as a tool that finds all of the .log files in the /home directory and searches each one for a particular entry. This erector-set mentality allows UNIX system administrators to seem to always have the right tool for the job.
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