Tech, ExplainedNetworking, infrastructure and security
Concept

Software-defined radio

A radio set by code, not circuits.

HOW IT WORKSAn antenna picks upradio wavesA converter turns thewaves into numbersA processor runssoftware that filtersthe wanted signalThe software decodesthe messageThe maker canchange thesoftware to supportanother standardBecause the radio's behaviour is in software, one pieceof hardware can be updated to handle a new standard.HOW IT WORKSAn antennapicks upradio wavesA converterturnsthe wavesinto numbersA processorrunssoftware thatfilters thewanted signalThe softwaredecodesthe messageThe maker canchange thesoftware tosupportanotherstandardBecause the radio's behaviour is in software, one pieceof hardware can be updated to handle a new standard.HOW IT WORKSAn antenna picks up radio waves↓A converter turns the waves into numbers↓A processor runs software that filtersthe wanted signal↓The software decodes the message↓The maker can change the software tosupport another standardBecause the radio's behaviour is in software, one piece ofhardware can be updated to handle a new standard.
An antenna and a converter turn radio waves into numbers, and software on a processor filters and decodes them.
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Software-defined radio (SDR) is a radio whose behaviour is set by software rather than fixed in hardware. In an older radio, a circuit made for one frequency and one kind of signal did the job, so a different signal needed a different radio. In a software-defined radio, the hardware only receives and sends raw radio signals, and software decides how to read and make them.

Here is how it works in general. An antenna picks up radio waves, and a fast converter turns them into numbers. A processor, such as a chip or a programmable circuit, runs software that handles those numbers. It filters the wanted signal, finds its frequency, and decodes the message. To send, the same processor makes the numbers for a signal, and a converter changes them to a radio wave. To change the radio to another standard, the maker changes the software and sends an update. Nothing is rewired.

The two key parts are the converter and the processor. The converter must sample the wave very fast, millions of times a second. The processor, often a programmable chip called an FPGA, must keep up with that speed. There is a cost. A software radio uses more power and costs more than a fixed chip made for one standard, so phones use fixed chips for their main standards. Software radio is used where flexibility matters more than cost: army radios, test equipment, base stations and satellites.

Take, for example, a mobile tower. The same hardware can be updated from an older to a newer standard by new software; see radio units and antennas and RAN software. Consider an army radio that must work on several frequencies and kinds of signal. A software-defined radio can switch among them; see defence electronics. Say a satellite dish must follow different satellites. Its radio can be changed by software.

The same idea is used in open RAN and moving software off hardware. It uses programmable chips as in FPGA timing and baseband chips. It also helps mesh networks.

How is it different from an ordinary radio? An ordinary radio can do one thing. A software-defined radio can be changed to do something else, even after it is sold.

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Networking, infrastructure and security
Industrial tech and mobility
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