Re: [Discuss-gnuradio] CRC check

Thank Marcus.

"packet decoding" recovers message from received packet 

and i got false from crc.py

def check_crc32(s):

    if len(s) < 4:

        return (False, '')

    msg = s[:-4]

    #print "msg = '%s'" % (msg,)

    actual = digital.crc32(msg)

    (expected,) = struct.unpack(">I", s[-4:])

    #print "actual =", hex(actual), "expected =", hex(expected)

    print actual == expected

    return (actual == expected, msg)

2016-02-21 20:52 GMT+09:00 Marcus Müller <marcus.mueller@ettus.com>:

Dear Sang Hyuk Kim,

what "packet decoding" are you specifically talking about, and could you show us the code you've modified?

Best regards,
Marcus

On 21.02.2016 12:32, SangHyuk Kim wrote:

Hi, I transmit simple text file using two USRP N210

Tx)

file source -> packet encoding -> mod(GMSK) -> usrp sink

Rx)

usrp source -> demod(GMSK) -> packet decoding -> file sink

To make corrupt packet, I tried to modify part of crc check

I guess if the crc of received packet doesn't match with original one, receiver would discard the packet.

However, I found receiver accepts every packet even if crc check returns 'false'.

(I expected receiver accepts packet only pass crc check by 'true')

 Why it always return false and how can I corrupt packet with other ways ?

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