Depuncture

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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

Insert description of flowgraph here, then show a screenshot of the flowgraph and the output if there is an interesting GUI. Currently we have no standard method of uploading the actual flowgraph to the wiki or git repo, unfortunately. The plan is to have an example flowgraph showing how the block might be used, for every block, and the flowgraphs will live in the git repo.

Source Files

C++ files
TODO
Header files
TODO
Public header files
TODO
Block definition
TODO