OFDM cannot receive the correct number of packets

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HI,

Recently I am conducting some ofdm experiments, using the example ofdm_tx/rx.grc and two USRPB210s, but I found that when the number of data packets I send is small (about ten or less), I can receive at the receiving end To the same number of packets. But when I increase the number of sent packets to about a few hundred, the number of received packets will be less than the number of sent packets, but occasionally their numbers will be equal. At first I thought it was caused by the too short sending and receiving time, but when I increased the sending and receiving time, occasionally the number of the two could be the same. Most of the time it was different.  What is the cause of the phenomenon? Is it a USRP sampling problem? How should I ensure that the number of data packets sent is the same as the number of received data packets each time? Is it really because of the time of sending and receiving?

I found that the amplitude of USRP is limited to the range of (-1, 1). If the "multiply const" setting is incorrect, will the receiver fail to detect the start of the data packet correctly, which causes this problem?

But why doesn't this error occur when the number of data packets is relatively small? Because the number of FFT transforms does not change, and the modulation method is also fixed at the four constellation points, theoretically, there should be no problems caused by the change in the number of data packets?

Sincerely

Thanks!

rx.pdf
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tx.pdf
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