Hi Michael, I was able to make a PER block and it turns out I was dropping some packets, so when I took into account those dropped packets when I performed the BER, I was in a much better place 10e-2. Thank you for the explanation and help!
I had another question. I was previously using the N210 for this, and have since upgraded to the X310. However I get severe underruns (I tried the WBX and UBX-160 daughtercards). No matter what samp rate I use (from 400kHz to 10 MHz), I get lots of U’s printed on my console and then the X310 stops transmitting and freezes. I saw a previous thread that mentioned it was a problem with the UHD 3.10 code (which I am running), but didn’t say how it was fixed. (See http://lists.ettus.com/pipermail/usrp-users_lists.ettus.com/2017-March/023924.html). Do you have any idea what the problem could be? I also put a null source instead of file source and changed the uhd sink to a probe+message debug, and it looks like my rates are good 2e7. The N210 works great and the X310 will transmit other data at the same rates, but not the ofdm_tx code. Thank you! Sarah From: Michael Dickens <michael.dick...@ettus.com> Sent: Thursday, March 8, 2018 6:12 AM To: Sarah Tran <st...@oceanit.com>; usrp-users@lists.ettus.com Subject: Re: [USRP-users] OFDM TX/RX BER Calculator Hi Sarah - Glad you're heading down a positive path. The header data is removed from the raw data being decoded, but added as meta-data on the stream. This meta-data is optionally printed out by GR OFDM and/or various Qt displays. Once the header has been verified (via CRC8), it is no longer part of the raw OFDM symbol data. Cheers! - MLD On Wed, Mar 7, 2018, at 9:11 PM, Sarah Tran wrote: Thank you for your quick response! I wanted the payload to be QPSK modulated. I put a QT Range blocks in for the gain settings on the ofdm_tx and ofdm_rx flowgraphs. I still can’t seem to get any better than 20% BER though, but I think the advice about doing a PER calculator is pointing me in the right direction as a lost packet would definitely screw up the BER. So thank you very much for the advice!! I did have another question though regarding the metadata that still has me confused. If the header data is taken out of the payload, why does it still show up when I put a time sink after the payload gettings decoded (after the constellation decoder/stream CR32 blocks)? It plots the decoded bits as well as the packet num, carrier_offset, etc. Did I put my time sink in the wrong place?
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