Forum: GNU Radio Is it possible to make a USRP Tx and Rx at the same time?

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9f439a67199b34986c71a6ada12e9870?d=identicon&s=25 Jane Chen (Guest)
on 2009-02-06 15:12
(Received via mailing list)
Hi all,

I would like use a USRP as a GSM base station. Is it possible to make it
Tx and Rx at the same time? How?
http://wireless.cs.uh..edu/presentation/2008/oct24...
In "A Survey on Spectrum Management in Cognitive Radio Networks" (the
link), (page 44) it mentioned CR users should stop transmitting while
sensing. I am confused. Does it mean that even though the CR user has
two transceivers, the CR user still cannot sensing and transmitting at
the same time?

Thank you,
Jane
D0072e69d706bb3ca211d33a1b536e2c?d=identicon&s=25 Johnathan Corgan (Guest)
on 2009-02-06 17:13
(Received via mailing list)
On Thu, Feb 5, 2009 at 4:14 PM, Jane Chen <janechen_1979@yahoo.com>
wrote:

> I would like use a USRP as a GSM base station. Is it possible to make it Tx
> and Rx at the same time? How?

GSM is a half-duplex TDMA protocol.  That is, a station is only ever
transmitting or receiving, but not both at the same time.

The channel is divided into timed frames and slots, and the base
station and mobile units are allocated specific times to transmit. The
USRP is capable of supporting this.

There are at least two existing open-source GSM BTS implementations;
OpenBTS is one of them:

http://gnuradio.org/trac/wiki/OpenBTS

This project uses the low-level C++ interface to the USRP1, but not
the GNU Radio framework itself.

Johnathan
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