1 research outputs found
Inter-Block Permuted Turbo Codes
The structure and size of the interleaver used in a turbo code critically
affect the distance spectrum and the covariance property of a component
decoder's information input and soft output. This paper introduces a new class
of interleavers, the inter-block permutation (IBP) interleavers, that can be
build on any existing "good" block-wise interleaver by simply adding an IBP
stage. The IBP interleavers reduce the above-mentioned correlation and increase
the effective interleaving size. The increased effective interleaving size
improves the distance spectrum while the reduced covariance enhances the
iterative decoder's performance. Moreover, the structure of the
IBP(-interleaved) turbo codes (IBPTC) is naturally fit for high rate
applications that necessitate parallel decoding.
We present some useful bounds and constraints associated with the IBPTC that
can be used as design guidelines. The corresponding codeword weight upper
bounds for weight-2 and weight-4 input sequences are derived. Based on some of
the design guidelines, we propose a simple IBP algorithm and show that the
associated IBPTC yields 0.3 to 1.2 dB performance gain, or equivalently, an
IBPTC renders the same performance with a much reduced interleaving delay. The
EXIT and covariance behaviors provide another numerical proof of the
superiority of the proposed IBPTC.Comment: 44 pages, 17 figure