Questions about the descramble results in BB11BRx when doing sending and receiving frames tests? RRS feed

  • Question

  •          Hello. I set the sending rate 2Mbps in 11b . The PLCP Header is set as the protocol  requirements and the preamble type is long preamble. The PSDU length is 50 bytes with 46 char 'B',and the the rest of 4 bytes CRC-32. It is as said the payload is 46 bytes except for CRC-32.

           However,When I added some "fprintf" and output some data processing results to some txt files. I found the result of PLCP Header was right. But after PLCP Header ,the first byte descrambled of the PSDU was '74"(ASCII), and that is 'H'.The second byte and the rests  were ‘66’(B)except the CRC-32. I had modified the scrambleseed  value when the preamble was  decoded and added    scrambleseed  value  when it began to decode the PSDU after decoding the PLCP Header. I tried some  scrambleseed  values related。  But it seemed the first byte '74' was right since it had the CRC-16 and CRC-32 check. I tried but I did not know why. Did the first byte value change when I sent the frame or some reason else.     It was a simple question I found before and asks now.Hoping your reply。

    Wednesday, May 28, 2014 2:46 AM

All replies

  • I cannot see clearly what is your question from the post.

    General suggestion: If the problem only related to CRC, scrambler, descrabler, CRC check, you may have more focused unit test on them. For example, try connected these components in a small test program and run your expected test, you will find the reason soon.

    Friday, May 30, 2014 11:01 AM
  • Frame content set in dot11btx.c(umxdot11)

    This was the frame content set "B",except CRC-32.Then I watched the dump file using sdscope-11b.exe.The result was below,and I also had added some fprintfs.The result was the same. ,the first byte descrambled of the PSDU was '74"(ASCII), and that is 'J'.The second byte and the rests  were ‘66’(B) The picture is as below:

    frame content picture 

    The first byte is "J"(I am sorry I make a mistake because I said it was "H" in my question),and that is the question I do not know why.I think it should be "B". .Do you see my question?

    Thank you .

    • Edited by d kd Tuesday, June 3, 2014 10:35 AM make a mistake
    Tuesday, June 3, 2014 10:32 AM