Re: [Discuss-gnuradio] 4x4 MIMO with USRP

[Eric Blossom]

On Wed, Aug 29, 2007 at 09:40:58PM -0500, Ketan Mandke wrote:
> Martin,
> 
> Thanks for your response. It is disappointing to hear that the MIMO
> support for 4 antennas will not be available for some time.

Addressing your disappointment:  This is a free software project.
Code gets written because some actual human being writes it ;)
If you're waiting for somebody else to write it, you may be waiting
for a long long time...

> Could you provide some more details into why this problem of aligning
> the transmit samples will be easier in the new m-block framework? Will
> these new packet oriented m-blocks utilize a different interface to
> the USRP which will make this alignment-task easier?

There will be a new interface.  More on that when it becomes available.

Each frame to be transmitted will have a timestamp that specifies the
time that it is to be transmitted.  You still have to sync the sample
clocks and LO's on the separate USRPs, but there will be a way to
communicate, in-band, when you want the frame to be transmitted.

Low-level design ideas are described here:

  http://gnuradio.org/trac/browser/gnuradio/trunk/usrp/doc/inband-signaling-usb

They are subject to change...

See also:

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

Eric