comnum.TurboCode#

class comnum.TurboCode(k, *, iterations=8, max_log=False, qpp=None, seed=7, puncture=None)#

The turbo code of LTE: two (13, 15) recursive systematic codes in parallel, rate about 1/3, decoded by iterative log-MAP (Berrou, Glavieux & Thitimajshima 1993). The interleaver is the QPP (f1, f2) if given ("lte": the coefficients of LTE for k, TS 36.212 Table 5.1.3-3), else a random permutation. puncture punctures the systematic and the two parity streams by a pattern of three rows applied at every information index (the tail bits are kept): the name "turbo_1_2" (systematic 1 1, parity 1: 1 0, parity 2: 0 1, the rate-1/2 code of Berrou et al. 1993, Sec. II) or the rows of a pattern.

Parameters:

  • k (int) – information bits per block.

  • iterations (int) – decoding iterations.

  • max_log (bool) – max-log-MAP (else log-MAP, the exact Jacobian logarithm).

  • qpp (str | tuple[int, int] | None) – the QPP interleaver (f1, f2), or "lte".

  • seed (int) – seed of the random interleaver.

  • puncture (str | list[list[int]] | None) – the puncturing pattern (three rows).

Raises:

ValueError – for an invalid parameter or input (the message names it).

Examples

>>> import comnum, numpy as np
>>> code = comnum.TurboCode(40, qpp=(3, 10), puncture="turbo_1_2")
>>> (code.n, round(code.rate, 3))
(92, 0.435)
decode(llr)#

Decode whole blocks of LLRs (iterative log-MAP).

Parameters:

llr (array_like) – a multiple of n LLRs (positive for a 0).

Returns:

k bits per block (uint8).

Return type:

numpy.ndarray

Raises:

ValueError – for an input that is not an array of numbers of the expected shape.

Examples

>>> import comnum, numpy as np
>>> code = comnum.TurboCode(40)
>>> b = comnum.bits(40, comnum.Rng(1))
>>> bool(np.array_equal(code.decode(2.0 - 4.0 * code.encode(b)), b))
True
encode(bits)#

Encode whole blocks.

Parameters:

bits (array_like) – a multiple of k bits.

Returns:

n coded bits per block (uint8).

Return type:

numpy.ndarray

Raises:

ValueError – for an input that is not an array of numbers of the expected shape.

Examples

>>> import comnum
>>> comnum.TurboCode(40).encode(comnum.bits(80, comnum.Rng(1))).size
264
iterations#

Decoding iterations (read and write).

Type:

int

k#

Information bits per block.

Type:

int

n#

Coded bits per block (3k + 12 without puncturing).

Type:

int

puncture#

The rows of the puncturing pattern (systematic, parity 1, parity 2), None without puncturing.

Type:

list[list[int]] | None

rate#

Code rate (after puncturing).

Type:

float