lteBCHDecode

Broadcast channel decoding

Syntax

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

Description

[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 in the CRC mask for given input, softbits, and the structure, enb. This function performs the inverse of the Broadcast Channel (BCH) processing described in TS 36.212 [1], Section 5.3.1.

Examples

Decode BCH-Encoded Block

Perform BCH coding of one transport block, and BCH decoding of part (one quarter) of the encoded block. 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.

Create cell-wide configuration structure, initialized to RMC R.4. Perform BCH coding of one transport block.

enb = lteRMCDL('R.4');
bchCoded = lteBCH(enb,ones(24,1));

Perform BCH decoding of one quarter of the transport block.

out = bchCoded(1:length(bchCoded)/4);
[bchDecoded,cellRefP] = lteBCHDecode(enb,out);
bchDecoded(1:10)

ans = 10x1 int8 column vector

   1
   1
   1
   1
   1
   1
   1
   1
   1
   1

Input Arguments

enb — eNodeB cell-wide settings

scalar structure

eNodeB cell-wide settings, specified as a structure containing these parameter fields:

Parameter Field	Required or Optional	Values	Description
CyclicPrefix	Optional	'Normal' (default), 'Extended'	Cyclic prefix length

softbits — Soft bits to decode

numeric 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 many repetitions of the coded block. This decoder allows the input argument softbits to be of any length because successful decoding of coded BCH blocks is often possible using a fraction of the full coded block length.

Output Arguments

trblk — Decoded information bits

integer-valued column vector

Decoded information bits, returned as an integer-valued column vector of length 24.

Data Types: int8

cellrefp — Number of CRS antenna ports

0 | 1 | 2 | 4

Number of cell-specific reference signal (CRS) antenna ports detected, returned as 0, 1, 2, or 4. A value of 0 indicates that the function detects a cyclic redundancy check (CRC) error during the decoding process.

Data Types: uint32

References

[1] 3GPP TS 36.212. “Evolved Universal Terrestrial Radio Access (E-UTRA); Multiplexing and channel coding.” 3rd Generation Partnership Project; Technical Specification Group Radio Access Network. URL: https://www.3gpp.org.

Version History

Introduced in R2014a