355 research outputs found
The q-ary image of some qm-ary cyclic codes: permutation group and soft-decision decoding
Using a particular construction of generator matrices of
the q-ary image of qm-ary cyclic codes, it is proved that some of these codes are invariant under the action of particular permutation groups. The equivalence of such codes with some two-dimensional (2-D) Abelian codes and cyclic codes is deduced from this property. These permutations are also used in the area of the soft-decision decoding of some expanded Reed–Solomon (RS) codes to improve the performance of generalized minimum-distance decoding
A Better Understanding of the Performance of Rate-1/2 Binary Turbo Codes that Use Odd-Even Interleavers
The effects of the odd-even constraint - as an interleaver design criterion -
on the performance of rate-1/2 binary turbo codes are revisited. According to
the current understanding, its adoption is favored because it makes the
information bits be uniformly protected, each one by its own parity bit. In
this paper, we provide instances that contradict this point of view suggesting
for a different explanation of the constraint's behavior, in terms of distance
spectrum
On Quadratic Inverses for Quadratic Permutation Polynomials over Integer Rings
An interleaver is a critical component for the channel coding performance of
turbo codes. Algebraic constructions are of particular interest because they
admit analytical designs and simple, practical hardware implementation. Sun and
Takeshita have recently shown that the class of quadratic permutation
polynomials over integer rings provides excellent performance for turbo codes.
In this correspondence, a necessary and sufficient condition is proven for the
existence of a quadratic inverse polynomial for a quadratic permutation
polynomial over an integer ring. Further, a simple construction is given for
the quadratic inverse. All but one of the quadratic interleavers proposed
earlier by Sun and Takeshita are found to admit a quadratic inverse, although
none were explicitly designed to do so. An explanation is argued for the
observation that restriction to a quadratic inverse polynomial does not narrow
the pool of good quadratic interleavers for turbo codes.Comment: Submitted as a Correspondence to the IEEE Transactions on Information
Theory Submitted : April 1, 2005 Revised : Nov. 15, 200
Blind identification of an unknown interleaved convolutional code
We give here an efficient method to reconstruct the block interleaver and
recover the convolutional code when several noisy interleaved codewords are
given. We reconstruct the block interleaver without assumption on its
structure. By running some experimental tests we show the efficiency of this
method even with moderate noise
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