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 ***


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

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?


发件人: Zhen [email protected]
收件人: [email protected]
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 ***


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

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