On Sat, May 5, 2012 at 12:00 PM, Amr Youssef <amryoussef.ieee.c...@gmail.com> wrote: > Hi , i have some questions : > > 1- In the following .cc file : ./gr-digital/lib/digital_crc32.cc > > Regarding CRC-32 , why the generated polynomial is of length 36 Bits > instead of 32 Bits (as expected) ! " it is written as : > // Automatically generated CRC function > // polynomial: 0x104C11DB7 > the above two lines exist in the code . "
Amr, That code is old and I'm not sure where it's from, but I'll respond like I know what I'm talking about, anyways (mostly from experience with these kinds of registers). That's not 36 bits, actually, it's 33 bits, and the 33rd bit is a 1. It's typical to have always have a 1 in the last place for shift registers like this. The algorithm itself is likely created using a 32-bit value. > 2- In the following .py file : ./gr-digital/python/ofdm_packet_utils.py > > How "random_mask_tuple" is generated through the 15-bit Linear Feedback > Shift Register (LFSR) . > Are they random ? if yes , why they are of length 8 bits (maximum number > 255 ) instead of 15 bits ?! > > Thanks in-advance > Amr, I'd have to let the person who wrote that code answer. Tom _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
