Why the ofdm data packet is not fully received ?

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Hello everyone,

I am using ofdm_tx/rx.grc to transfer text file data, and there is a "hello world" character in the text. I use two usrpb210 for transmission .When I set the "repeat" in the "file sink" to no, the receiving end cannot receive the correct "hello world" word, and the open file is blank; but when I set the "repeat" to yes, the receiving file is opened , Which contains a lot of repeated "hello world" words, I want to know why this happens? How can I solve this problem? (It can still be received correctly when my "repeat" is set to no)

The flowchart is in the attachment.

Thanks to anyone for the relevant information, thank you!

Sincerely

tx.pdf
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rx.pdf
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