Wavecom W-BitView V2.5.00 - Manual (Page 46)

40

Function Library BitView Manual V2.5.00 WAVECOM W-BV
Example with code length 15 and error correction capability 3:
“011001010000111” is changed to “00111”.
Block Code Analysis
In: Bit stream
Out: Bit stream
Function:
Identify forward error correction block codes like BCH, RS, CRC or Hamming.
The function returns alphabet size (normally equal to 2 because input is a binary bit stream), block code
type (BCH, RS, etc.), code word length estimation (n), generator polynomial, input length estimation (k)
and code rate estimation (R = k/n).
The function will identify the following Block Code Types,
BCH
CRC or perfect cyclic code
Binary repetition (reversals)
Binary Golay
Binary Hamming
CRC block code
Non-cyclic block code
Unidentified code
The generator polynomial is returned as a string of ones and zeros, starting at the lowest order of 2^x,
e.g., 1001110010101 means 1 + x^3 + x^4 + x^5 + x^8 + x^10 + x^12.
The results of the analysis are displayed in a new document window and in the Calculation category in
the Properties window. The table below lists the calculated parameters.
Parameter Description
Alphabet size Size of input alphabet
Block code type Type of block code used
Codeword length
estimation
Length of input code word (n) , i.e., number of data bits (k) plus number of checksum bits
(n-k)
Generator polyno-
mial
Generator polynomial (G(x)), i.e., the polynomial used to generate the checksum
Input length Estimated number of data bits per code word
Rate estimation Code rate (R = k/n), i.e., ratio between number of data bits (k) and total number of bits
per frame (n+k)
Constraints: Frames must have equal length and if the bit stream is delimited by flags they must be
removed with the Extract or Cut functions.
Convolutional Code Analysis
In: Bit stream
Out: Bit stream