Re： [Discuss-gnuradio] Problem of ***BAD CRC *** for GNURadio bbn_80211b

[Zhen]

It's solved! Just open 'bbn_80211b_pkt.py' and set  'short_preamble = 0', then long preamble is used and test scripts work well.

But why short preamble doesn't work?

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发件人： Zhen <address@hidden>
收件人： address@hidden
发送日期： 2010/10/9 (周六) 6:25:22 下午
主 题： [Discuss-gnuradio] Problem of ***BAD CRC*** for GNURadio bbn_80211b

Hi all,

I ran into a problem than seems also met by others, but I am not sure how to solve it.

I use GNU Radio 3.2.2, bbn 802.11b usrp2_version, Python 2.6.5, GCC 4.4.3,  and Ubuntu 10.4 LTS.

When I ran the test scripts "bbn_80211b_sptest.py" and "bbn_80211b_test.py" from /bbn_80211_branches/usrp2_version/gr-bbn/src/examples, they both reported BAD CRC error, with the outputs like these:

------------------------------------------------------------------
SNR set at:  12  spb set at:  25  using barker:  1
>>> gr_fir_ccf: using SSE
Recieved (short) header!
  signal: 0x70
  service: 0x4B
  length: 0xE3B1
  crc: 0x7F0F
Calculated crc: 0x7F68
*** BAD CRC ***

Recieved (short) header!
  signal: 0x7D
  service: 0xD6
  length: 0xB306
  crc: 0x5672
Calculated crc: 0xA702
*** BAD CRC ***

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I searched mailing list, it seems the problem is from short PLCP preamble, but how to fix it and make it run successfully?

Thanks in advance!

Hanks