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Tue, 25 Jan 2011
TETRA Air Interface

If you are interested in how the air interface and the lower levels of TETRA work, you should have a look at the website.

My contribution so far was to search for a suitable demodulator (TETRA uses PI/4-DQPSK) which I found at the OP25 project (the author of the demodulator is KA1RBI).

I also implemented some "proof of concept" code which allows decoding speech traffic and converting it to raw audio using the TETRA reference codec. Please note that this cannot be used to listen to encrypted TETRA traffic, it only works if no encryption is used.

[ /sdr | permanent link ]

Sun, 01 Aug 2010
Microsoft Research and SDR

I wasn't aware of it, but Microsoft Research is doing SDR (Software Defined Radio): Sora.

Their approach is interesting, all the raw samples are transferred between the PC memory and the ADC/DAC of the Radio Front-end by a PCIe card and all the signal processing is done by the CPU of a PC. There is no DDC (Digital Down Converter) or DUC (Digital Up Converter) in an FPGA involved. They already implemented 802.11a/b/g and an LTE receiver this way.

The price of the hardware does not sound too expensive. The software only runs on Windows and I have not yet checked the license terms in detail.

I could imagine that combining this approach with the power of a GPU can be quite interesting.

[ /sdr | permanent link ]