Browse Prior Art Database

Key Equation Solver for Variable Block Reed-Solomon Decoders

IP.com Disclosure Number: IPCOM000115660D
Original Publication Date: 1995-Jun-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 2 page(s) / 65K

Publishing Venue

IBM

Related People

Blanz, E: AUTHOR [+5]

Abstract

The syndrome generation and the Chien search in a Reed-Solomon decoder proceed in opposite directions. Thus, if a is the generator of the finite field over which the decoder operates, the syndromes are the values of the codeword polynomial c(x) at the locations [a sup i ] sub 0 sup r-1 which coincide with the zeroes of the encoder polynomial. The Chien search, on the other hand, evaluates the error locator polynomial v(x) at the locations [ a sup N-i ] sub 0 sup N-1, where N is the codeword size. Since the decoder has no knowledge of the codeword size value N, which may change, it appears that the Chien search has to be updated with scalar factors computed from the read data. If the error evaluator v(x) is of degree t, this implies the computation of t-1 scalar factors a sup jN, j=1, ..., t-1.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 58% of the total text.

Key Equation Solver for Variable Block Reed-Solomon Decoders

      The syndrome generation and the Chien search in a Reed-Solomon
decoder proceed in opposite directions.  Thus, if a is the generator
of the finite field over which the decoder operates, the syndromes
are the values of the codeword polynomial c(x) at the locations [a
sup i ]  sub 0 sup r-1 which coincide with the zeroes of the encoder
polynomial.  The Chien search, on the other hand, evaluates the error
locator polynomial v(x) at the locations [  a sup N-i ]  sub 0 sup
N-1, where N is the codeword size.  Since the decoder has no
knowledge of the codeword size value N, which may change, it appears
that the Chien search has to be updated with scalar factors computed
from the read data.  If the error evaluator v(x) is of degree t, this
implies the computation of t-1 scalar factors a sup jN, j=1, ...,
t-1.  Since they are variable, this would require in addition t-1
variable multipliers to achieve the proper scaling.  Since variable
multipliers are hardware expensive, at the cost of t delay cycles, it
is possible to update the Chien search using a single variable
multiplier, a multiplexor and some control logic.

      In this disclosure a solution is proposed that completely
eliminates the need for variable multipliers for the Chien search
update.  Instead, a change in the Key Equation Solver is introduced.
In prior art a symbol slice for a Key Equation Solver is described.
This symbol slice is...