Communications Toolbox™

fec.bchenc - Construct BCH encoder object

Synopsis

h = fec.bchenc

h = fec.bchenc(N,K)

h = fec.bchenc(property1, value1, ...)

h = fec.bchenc(bchdec_object)

Description

enc = fec.bchenc constructs a BCH encoder enc with default properties. It is equivalent to: enc = fec.bchenc(7,4)

enc = fec.bchenc(N,K) constructs an (N,K) BCH encoder object enc.

enc = fec.bchenc(property1, valule1, ...) constructs a BCH encoder object enc with properties as specified by PROPERTY/VALUE pairs.

enc = fec.bchenc(bchdec_object) constructs a BCH encoder object enc by reading the property values from the BCH decoder object bchdec_object

Properties

A BCH encoder object has the following properties, which are all writable except for the ones explicitly noted otherwise.

Property	Description
Type	The type of encoder object. This property also displays the effective message length and codeword length, taking shortening and puncturing into consideration. This property is not writable.
N	The codeword length of the base code, not including shortening or puncturing.
K	The uncoded message length, not including shortening.
T	The number of errors the base code is capable of correcting. This property is not writable.
ShortenedLength	The number of bits by which the code has been shortened.
ParityPosition	Must be 'beginning' or 'end'. Specifies if parity bits should appear at the beginning or end of the codeword.
PuncturePattern	Indicates which parity bits in a codeword are punctured. This binary-valued vector is of length N-K. Values of "0" indicate bits that are punctured, and values of "1" indicate bits that are not.
GenPoly	The generator polynomial for the code. GenPoly must be a Galois row vector that lists the coefficients, in order of descending powers, of the generator polynomial.

Methods

`CODEWORD = ENCODE(ENC, MSG)`

Encodes MSG using the BCH code specified by a BCH encoder object ENC. MSG must be an array of binary elements, with an integer multiple of K-ShortenedLength elements per column. There may be multiple codewords per channel, where each group of K-ShortenedLength input elements represents one message word to be encoded. Each column of MSG is considered to be a separate channel, with the same BCH code applied to each channel.

Usage Examples

%Create BCH encoder object.
enc = fec.bchenc(7,4);
  
% Create a message to be encoded.
msg = [0 1 1 0]'; 
  
% Encode msg with the ENCODE function.
code = encode(enc,msg);
     
% Create a shortened encoder
encShort = copy(enc);
encShort.ShortenedLength = 1;
 
% Create a shortened message
msgShort = [0 1 1]';
 
codeShort = encode(encShort,msgShort);

% Create a punctured encoder
encPunc = copy(enc);
encPunc.PuncturePattern = [1 0 1];

% Create a punctured message
codePunc = encode(encPunc,msg);

References

[1] Wicker, Stephen B., Error Control Systems for Digital Communication and Storage, Upper Saddle River, N.J., Prentice Hall, 1995.

[2] Berlekamp, Elwyn R., Algebraic Coding Theory, New York, McGraw-Hill, 1968.

fec.bchdec

fec.rsdec