Salija,

the notation

interleaver(666)

is one way to generate a random interleaver with a given seed (666 in

this

case).

The pccc block requires two FSM (finite state machine) specifications

(one

for each of the constituent codes)

and an interleaver specification.

You can give the interleaver specification either through a file or by

letting gnuradio generate a random one.

The interleaver class (pretty straighforward) has been implemented in

the

files:

gr-trellis/include/trellis/gnuaradio/interleaver.h

gr-trellis/lib/interleaver.cc

I am copying the class definition below:

/*!

* \brief INTERLEAVER class

* \ingroup trellis_coding_blk

*/

class TRELLIS_API interleaver

{

private:

int d_K;

std::vector d_INTER;

std::vector d_DEINTER;

```
public:
interleaver();
interleaver(const interleaver & INTERLEAVER);
interleaver(int K, const std::vector<int> & INTER);
interleaver(const char *name);
interleaver(int K, int seed);
int K () const { return d_K; }
const std::vector<int> & INTER() const { return d_INTER; }
const std::vector<int> & DEINTER() const { return d_DEINTER; }
void write_interleaver_txt(std::string filename);
};
```

as you can see there are 5 possible constructors:

interleaver();

interleaver(const interleaver & INTERLEAVER);

interleaver(int K, const std::vector & INTER);

interleaver(const char *name);

interleaver(int K, int seed);

the first 2 are trivial and copy constructor,

the third construct an interleaver from a vector with specified

permutations and

the fourth one from a file with specified permutations.

The last one constructs it from a random permutation with a given seed

(please see .cc code for details).

Let us know if you have any more questions.

Achilleas