Re: [Discuss-gnuradio] gr-lte chanel estimation

[Johannes Demel]

Hey Doug,

This particular part of the flowgraph deals with reception of a 2
antenna transmitter. That implies that an Alamouti code is applied
before transmission. Thus, for correct reception, it is necessary to
perform the inverse Alamouti code operation. This is generally called
Precoding. For data channels, some other schemes are used as well.
They all require to do an inverse operation. So, the flowgraph does
channel estimation for all antennas. Also, RS symbols are transmitted
differently for each antenna layer.
Without a second receiver antenna, this whole channel estimation,
precoding thing does not result in better reception. But you could use
a B210 or a similar device which offers to RX channels in order to
exploit this extra diversity.
Hope that sheds some light on why and how things are done. Also let me
know about specifics which are unclear in those blocks. So I'll add
some doc.

Cheers
Johannes

On 01.07.2015 23:16, Anderson, Douglas J. wrote:
> Hi all,
> 
> I'm working at putting together a flowgraph based on gr-lte.
> 
> For the channel estimator hier block [1], it looks like there are
> two RS map generators, one for each of 2 "antenna ports".
> 
> I only have one antenna connected to my USRP N210. Is this a
> problem? Do I still use 2 RS map generators with antenna port 0 and
> 1?
> 
> -Doug
> 
> [1]
> https://raw.githubusercontent.com/kit-cel/gr-lte/master/docs/lte_estimator_hier.grc.png
>