Depuncture

Depuncture a given block of input samples of . The items produced is based on the pattern. Basically, if:

k = 0
if _puncpat[i] == 1:
   out[i] = input[k++]
else:
   out[i] = symbol # default sym=127

This block is designed for unpacked bits - that is, every input sample is a bit, either a 1 or 0. It's possible to use packed bits as symbols, but the depuncturing will be done on the symbol level, not the bit level.

puncpat is specified as a 32-bit integer that we can convert into the vector _puncpat used in the algorithm above:

_puncpat = [0,...]
for i in puncsize:
    _puncpat[i] = puncpat >> (puncsize-1-i)

Example:

puncsize = 8
puncpat = 0xEF  -->  [1,1,1,0,1,1,1,1]
input = [a, b, c, d, e, f, g, h]
output = [a, b, c, 127, e, f, g, h]

The gr.fec Python module provides a read_bitlist function that can turn a string of a puncture pattern into the correct integer form. The pattern of 0xEF could be specified as fec.readbitlist("11101111"). Also, this allows us to use puncsize=len("11101111") to make sure that our sizes are set up correctly for the pattern we want.

The fec.extended_decoder takes in the puncture pattern directly as a string and uses the readbitlist inside to do the conversion.

The parameter delays the application of the puncture pattern. This is equivalent to circularly rotating the by . Note that because of the circular shift, the delay should be between 0 and , but this is not enforced; the effective delay will simply be mod . A negative value here is ignored.

Parameters

Puncture Size

Size of block of bits to puncture

Puncture Pattern

The puncturing pattern

Delay

Delayed the puncturing pattern by shifting it

Symbol

The symbol to reinsert into the stream (def=127)

Example Flowgraph

This flowgraph can be downloaded from Media:Depuncture.grc.

Source Files

C++ files

TODO

Header files

TODO

Public header files

TODO

Block definition

TODO