gr::fec::code::cc_decoder
gr::fec::generic_decoder
gnuradio/fec/cc_decoder.h
generic_decoder::sptr static generic_decoder::sptr gr::fec::code::cc_decoder::make (int frame_size, int k, int rate, std::vector< int > polys, int start_state=0, int end_state=-1, cc_mode_t mode=CC_STREAMING, bool padded=false) make gr::fec::code::cc_decoder::make int frame_size int k int rate std::vector< int > polys int start_state 0 int end_state -1 cc_mode_t mode CC_STREAMING bool padded false

Build a convolutional code decoding FEC API object.

frame_size

Number of bits per frame. If using in the tagged stream style, this is the maximum allowable number of bits per frame.

k

Constraint length (K) of the encoder.

rate

Inverse of the coder's rate (rate=2 means 2 output bits per 1 input).

polys

Vector of polynomials as integers.

start_state

Initialization state of the shift register.

end_state

Ending state of the shift register.

mode

cc_mode_t mode of the encoding.

padded

true if the encoded frame is padded to the nearest byte.

CC_STREAMING
rate
bool bool gr::fec::code::cc_decoder::set_frame_size (unsigned int frame_size) override=0 set_frame_size gr::fec::code::cc_decoder::set_frame_size set_frame_size unsigned int frame_size

Sets the uncoded frame size to `frame_size`. If `frame_size` is greater than the value given to the constructor, the frame size will be capped by that initial value and this function will return false. Otherwise, it returns true.

double double gr::fec::code::cc_decoder::rate () override=0 rate gr::fec::code::cc_decoder::rate rate

Returns the coding rate of this encoder.

make

Convolutional Code Decoding class.

This class performs convolutional decoding via the Viterbi algorithm. While it is set up to take variable values for K, rate, and the polynomials, currently, the block is only capable of handling the following settings:

- K = 7

- rate = 1/2 (given as 2 to the constructor)

- polynomials = [109, 79]

This is the well-known convolutional part of the Voyager code implemented in the CCSDS encoder.

The intent of having this FECAPI code classes fully parameterizable is to eventually allow it to take on generic settings, much like the cc_encoder class where the CCSDS settings would be a highly-optimized version of this.

The decoder is set up with a number of bits per frame in the constructor. When not being used in a tagged stream mode, this encoder will only process frames of the length provided here. If used in a tagged stream block, this setting becomes the maximum allowable frame size that the block may process.

The `mode` is a cc_mode_t that specifies how the convolutional encoder will behave and under what conditions.

- 'CC_STREAMING': mode expects an uninterrupted flow of samples into the encoder, and the output stream is continually encoded. This mode is the only mode for this decoder that has a history requirement because it requires rate*(K-1) bits more to finish the decoding properly. This mode does not work with any deployments that do not allow history.

- 'CC_TERMINATED': is a mode designed for packet-based systems. This mode adds rate*(k-1) bits to the output as a way to help flush the decoder.

- 'CC_TAILBITING': is another packet-based method. Instead of adding bits onto the end of the packet, this mode will continue the code between the payloads of packets by pre-initializing the state of the new packet based on the state of the last packet for (k-1) bits.

- 'CC_TRUNCATED': a truncated code always resets the registers to the `start_state` between frames.

A common convolutional encoder uses K=7, Rate=1/2, Polynomials=[109, 79]. This is the Voyager code from NASA:

- 109: b(1101101) --> 1 + x + x^3 + x^4 + x^6

- 79: b(1001111) --> 1 + x^3 + x^4 + x^5 + x^6

gr::fec::code::cc_decoder
gr::fec::generic_decoder
gr::fec::code::cc_decoder
gr::fec::generic_decoder
d_logger
d_name
std::basic_string< Char >
std::shared_ptr< logger >
std::string
- gr::fec::code::cc_decoder
  alias
- gr::fec::code::cc_decoder
  base_unique_id
- gr::fec::code::cc_decoder
  d_logger
- gr::fec::code::cc_decoder
  d_name
- gr::fec::code::cc_decoder
  generic_decoder
- gr::fec::code::cc_decoder
  generic_decoder
- gr::fec::code::cc_decoder
  generic_work
- gr::fec::code::cc_decoder
  get_history
- gr::fec::code::cc_decoder
  get_input_conversion
- gr::fec::code::cc_decoder
  get_input_item_size
- gr::fec::code::cc_decoder
  get_input_size
- gr::fec::code::cc_decoder
  get_iterations
- gr::fec::code::cc_decoder
  get_output_conversion
- gr::fec::code::cc_decoder
  get_output_item_size
- gr::fec::code::cc_decoder
  get_output_size
- gr::fec::code::cc_decoder
  get_shift
- gr::fec::code::cc_decoder
  make
- gr::fec::code::cc_decoder
  my_id
- gr::fec::code::cc_decoder
  rate
- gr::fec::code::cc_decoder
  set_frame_size
- gr::fec::code::cc_decoder
  sptr
- gr::fec::code::cc_decoder
  unique_id
- gr::fec::code::cc_decoder
  ~generic_decoder