Problem of BAD CRC for GNURadio bbn_80211b

Zhen · October 10, 2010, 3:15am

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 ***

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

Zhen · October 10, 2010, 6:58am

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?

å‘ä»¶äººï¼š Zhen [email protected]
æ”¶ä»¶äººï¼š [email protected]
å‘é€æ—¥æœŸï¼š 2010/10/9 (å‘¨å…) 6:25:22 ä¸‹åˆ
ä¸» é¢˜ï¼š [Discuss-gnuradio] Problem of BAD CRC for GNURadio
bbn_80211b