Audio Networking With GNU Radio

fsk

Thought GNU Radio was just for radio? Think again. [Chris] has been hard at work turning the signal generation and analysis of the best tool for software defined radio into a networking device for speakers and a microphone.

The setup uses GNU Radio to generate a carrier signal whose frequency is modulated with a data stream. With this modulated signal piped over a laptop’s speakers, [Chris] is able to send UDP packets across his desk using nothing but sound.

[Chris] had recently used a similar technique to transmit data via audio with GNU Radio, but this latest build is a vast improvement; this is now a duplex networking, meaning two computers can transmit and receive at the same time.

In the end, [Chris] created a strange, obsolete device called a “modem”. It’s not exactly fast; sending ‘Hello World’ takes quite a bit of time, as you can see in the video below.

[Read more...]

Ultrasonic Data Transmission With GNU Radio

ultrasonic

When we hear GNU Radio was used in a build, the first thing we think of is, obviously, radio. Whether it’s a using extremely expensive gear or just a USB TV tuner dongle, GNU Radio is the perfect tool for just about everything in the tail end of the electromagnetic spectrum.

There’s no reason GNU Radio can’t be used with other mediums, though, as [Chris] shows us with his ultrasound data transmission between two laptops. He’s transmitting audio from the speakers of one laptop at 23 kHz. It’s outside the range of human hearing, but surprisingly able to be picked up by a cheap desktop mic connected to another laptop. His GNU Radio setup first converts a string of text to a 5-bit packet, modulates it with FSK, and bumps up the signal to 23 kHz. On the other end, the data is decoded by doing the same thing in reverse.

The setup is easily able to reject all audio that isn’t in the specified frequency range; in the video after the break, [Chris] successfully transmits a ‘hello world’ while narrating what he’s doing.

[Read more...]

Follow

Get every new post delivered to your Inbox.

Join 97,759 other followers