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the numble of complex in the preamble RRS feed

  • Question

  • Hi, there!

    In the process of transmitting, COMPLEX_PER_SYMBOL  equals to 160, and the preamble equals to 4*COMPLEX_PER_SYMBOL =640. But it seems in the process of receiving, the number of COMPLEX_PER_SYMBOL decreases by half. And so we do Signal  and Data processing every 80 complexes. les me is that, the numble of preamble(used for both cs and sync and preamblefft) should be 4*80=320 ,but according to the comment of the "preamblefft" function   there are just 160 complexes(used for both cs and sync and preamblefft)?

    Waiting for your answer!

    Thursday, January 17, 2013 2:24 PM

Answers

  • Hi buptboy,
    I understand your question now. The PLCP preamble field is used for synchronization. It consists of 10 short symbols and two long symbols. BB11ARxTrySync consumes short training symbols, and BB11ARxTryPreambleFFT consumes long training symbols.

    • Proposed as answer by Qi LuoEditor Monday, January 21, 2013 5:15 AM
    • Marked as answer by buptboy Friday, January 25, 2013 2:55 AM
    Monday, January 21, 2013 5:14 AM
    Answerer

All replies

  • I assume your question is related to the function BB11ARxFrameDemod. The implementation of the function FetchDMADataTouchDownSampled40 shows the signal fetched from RX stream (40M sample per second) is down-sampled to 20M. So the number of samples in a OFDM symbol decreases to half.
    • Proposed as answer by Qi LuoEditor Friday, January 18, 2013 8:11 AM
    Friday, January 18, 2013 8:11 AM
    Answerer
  • Yes, it's related to the function BB11ARxFrameDemod.But what really puzzles me is that ,after the function of FetchDMADataTouchDownSampled40,there should have 320 complexes in the receiver ,because there are 640 complexes in the preamble in the transmitter.But the comments below tells us that there are just 160 complexes . I don't know where I am wrong. Waiting for your answer, thanks a lot.

    Friday, January 18, 2013 3:34 PM
  • Hi buptboy,
    I understand your question now. The PLCP preamble field is used for synchronization. It consists of 10 short symbols and two long symbols. BB11ARxTrySync consumes short training symbols, and BB11ARxTryPreambleFFT consumes long training symbols.

    • Proposed as answer by Qi LuoEditor Monday, January 21, 2013 5:15 AM
    • Marked as answer by buptboy Friday, January 25, 2013 2:55 AM
    Monday, January 21, 2013 5:14 AM
    Answerer