Re: [Discuss-gnuradio] gr-lte updated to GNU Radio 3.7 API

[Johannes Demel]

Hi,

regarding the different parameters. 'tx_diversity' should always be left as it is. In case of a 1x1 MIMO configuration it will just have no effect. This parameter reflects the LTE standard with its two options 'tx_diversity' and 'spatial_multiplexing'. The latter isn't used for control channels.

In order to specify a certain bandwidth, use the parameter 'N_rb_dl', which specifies the number of resource blocks used. This will also set the bandwidth as this is the unit given by the system to determine the bandwidth. e.g. have a look at the paper which is included in the project there is a table which shows the dependencies.

25 RBs --> 25*12 = 300 subcarrier --> 15kHz * 300 + spacing = 5MHz.

The FFT length can be chosen freely as long as it provides sufficient bins to match the current number of subcarriers. It will be used to determine the input sample rate. I suggest you stick with power of 2 values. Those are the only ones I tested and the numbers the system is designed for. One more thing, a FFT length shorter than 256 results in fractional CP lengths, which should be avoided. LTE's CP use is already quite tricky and the introduction of fractional CP lengths will not ease the situation.

PBCH decoding is handled for one and two antenna configurations, so you don't have to worry about configuring the flowgraph there.

PCFICH decoding will receive a message on runtime which sets the decoded antenna configuration.

Happy hacking

Johannes

On Fri, Dec 20, 2013 at 2:39 AM, Baier <address@hidden> wrote:

Hi Johannes,

thank you very much for updating your gr-lte package. I could compiled all .grc files succesfully. Now I would like to test your receiver with a LTE signal saved to a file with the following settings.( 5 MHz, RB 25, fft 512, occupied carriers 300, no tx diversity). So I have started to change the parameters in your grc files.
RB 25 instead 50
fftlen 512 instead 2048(is it right?)
occupied carriers 300 instead 600.
So I have realized the files decode_pcfich_37.grc and decode_pbch_37 .grc are designed for tx_diversity with two antennas. How can I change it? Removing the blocks for the second antenna perhaps?
Thank you very much.
A. Baier

                   

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