Documentation

lteBCHDecode

Broadcast channel decoding

Syntax

  • [trblk,cellrefp] = lteBCHDecode(enb,softbits)
    example

Description

example

[trblk,cellrefp] = lteBCHDecode(enb,softbits) returns a vector, trblk, of the decoded information bits (24 bits). cellrefp is the number of cell-specific reference signal antenna ports detected (1,2,4) in the CRC mask for given input, softbits, and the structure, enb.

If the cellrefp value is 0, a CRC error has been detected.

The transport block size, 24, is relatively small when compared to the number of coded bits sent in the BCH transmission, 1920 or 1728. For this reason, the rate matching internal to the BCH coding results in a large number of repetitions of the coded block. Therefore, the decoder can successfully decode blocks whose lengths are much shorter than the length of the full coded block. Consequently, this decoder allows the input argument softbits to be of any length.

Examples

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Decode BCH-Encoded Block

Perform BCH encoding of one transport block. Then, perform BCH decoding of part of the encoded block, one quarter the length.

enb = lteRMCDL('R.4');
bchCoded = lteBCH(enb,ones(24,1));
out = bchCoded(1:length(bchCoded)/4);
[bchDecoded,cellRefP] = lteBCHDecode(enb,out);
bchDecoded(1:10)
    1
    1
    1
    1
    1
    1
    1
    1
    1
    1

In a practical system, this approach would be used to attempt BCH decoding on the one quarter part of the encoded block that is transmitted in the first subframe of each frame.

Input Arguments

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enb — eNodeB cell-wide settingsscalar structure

eNodeB cell-wide settings structure that can contain these parameter fields.

Parameter FieldRequired or OptionalValuesDescription
CyclicPrefixOptional

'Normal' (default), 'Extended'

Cyclic prefix length

softbits — Soft bits to decodenumeric vector

Soft bits to decode, specified as a numeric vector. This vector can have any length.

The transport block size, 24, is relatively small when compared to the number of coded bits sent in the BCH transmission, 1920 or 1728. For this reason, the rate matching internal to the BCH coding results in a large number of repetitions of the coded block. Therefore, the decoder can successfully decode blocks whose lengths are much shorter than the length of the full coded block.

Output Arguments

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trblk — Decoded information bitsinteger column vector

Decoded information bits, returned as a 24-by-1 integer column vector.

Data Types: int8

cellrefp — Number of cell-specific reference signal (CRS) antenna ports0 | 1 | 2 | 4

Number of cell-specific reference signal (CRS) antenna ports detected, returned as a nonnegative scalar integer. Possible values are 0, 1, 2, and 4. If the value is 0, a CRC error has been detected.

Data Types: uint32

See Also

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Introduced in R2014a

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