Re: [Discuss-gnuradio] ofdm_sync and ofdm_sampler blocks

[monika bansal]

Please help me with this.

Thanks.

Regards,

-monika

On Wed, Apr 27, 2016 at 4:37 PM, monika bansal <address@hidden> wrote:

Hi,

I have connected benchmark_tx.py and benchmark_rx.py to make it loopback mode without USRPs. There is no channel block between the tx and rx chain.

I checked all blocks in the Transmit chain. All are working as expected. But in Receiver chain i did not understand the output of ofdm_sync_ml and digital.ofdm_sampler  blocks. 

I tried checking the output of port 1 of ofdm_sync. The sync signal is one on the following indexes:

 714,   7109,  13515,  19911,  26308,  32705,  39115,  45515,

        51910,  58315,  64715,  71115,  77515,  83915,  90315,  96712,

       103115, 109512, 115910, 122315, 128715, 135113, 141510, 147915,

       154288, 160711, 167112, 173515, 179912, 186315

I checked the output of port 1 of ofdm_sampler. The sync signal is one on the following indexes:

0,   5120,  10752,  15872,  20992,  26112,  31744,  36864,

        41984,  47616,  52736,  57856,  62976,  68096,  73216,  78336,

        83968,  89088,  94208,  99840, 104960, 110080, 115200, 120832,

       125952, 131584, 136704, 142336, 147456, 153088

I expected the output of port 1 of ofdm_sync to be 639, 639+6400, 639+12800 , ...

and output of  port 1 of ofdm_sampler to be 0, 5120, 5120*2, 5120*3, ....

General parameters are as follows: 

fft_len = 512

cp_len = 128

occupied_tones = 200

modulation = bpsk

pkt_size = 200 bytes

after CRC and Header pkt_length = 209 bytes

1 sync word for each packet

Finally there will be 10 OFDM symbols per pkt and 512+128 = 640 complex symbols per OFDM symbol.