Re: [Discuss-gnuradio] Query on simulation of MIMO on Gnuradio

[Martin Braun]

Karan,

the current 'master' branch has a "multiply_matrix_cc" block which might
be what you're looking for.

M

On 08/06/2014 08:47 AM, Karan Talasila wrote:
> Hi,
>      we are trying to implement alamouti encoding and decoding on an
> underlying ofdm communication system in Gnuradio. So we are using
> benchmark_tx.py. In  ofdm mapper block we have written our own block
> which does alamouti encoding which gives out alamouti encoded symbols
> across two output ports. The first output port will give x1 and -x2*.
> The second output port will give x2 and x1* according to the alamouti code.
> 
> Now, from each of these two output ports, we are connecting an insert
> preamble block followed by an IFFT block and then a cyclic prefixer
> block. All of these blocks are standard gnuradio blocks used  in ofdm
> examples directory in gnuradio( benchmark_tx.py). Now we would want to
> connect these two ouputs to their respective usrp sink blocks thereby
> implementing a mimo system with 2 transmitters.
> 
> Now we are using an alamouti decoder block which is implemented in ofdm
> frame acquisition block. Before we put it on usrp's which require
> perfect hardware time synchronisation, we  would like to test whether
> our end to end transmitter and receiver in software is working. So we
> connected the txpath1 to rxpath1 and txpath2 to rxpath2 which is like
> connecting two transmitters to two receivers directly. But we are not
> receiving the decoded symbols properly. when we are debugging, we are
> having doubts as to maybe the H matrix(channel matrix) values of h12 and
> h21 might not be received because we are connecting transmitter 1 to
> receiver 1 and transmitter 2 to receiver 2. can that be an issue?
> 
> In general how do you test mimo blocks in software. Is the way we are
> doing right i.e. connecting txpath1 to rxpath1 and txpath2 to rxpath2.
> Or are there other better ways of testing end to end MIMO systems
> without hardware?
> 
> 
> 
> -- 
> Regards
> Karan Talasila
> 
> 
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