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IEEE TRANSACTIONS ON INFORMATION THEORY, VOL. 47, NO. 2, FEBRUARY 2001 699 The Turbo Decoding Algorithm and Its Phase
 

Summary: IEEE TRANSACTIONS ON INFORMATION THEORY, VOL. 47, NO. 2, FEBRUARY 2001 699
The Turbo Decoding Algorithm and Its Phase
Trajectories
Dakshi Agrawal, Member, IEEE, and Alexander Vardy, Fellow, IEEE
Abstract--This paper analyzes phase trajectories and
fixed points of the turbo decoding algorithm as a function of
signal-to-noise ratio (SNR). By exploiting the large length of turbo
codes, the turbo decoding algorithm is treated as a single-param-
eter dynamical system, parameterized (approximately) by the
SNR. This parameterization, along with extensive simulations
at practical SNRs and asymptotic analysis as SNR goes to zero
and infinity, is used to subdivide the entire SNR range into
three regions with the "waterfall region" in the middle. The
turbo decoding algorithm has distinctive phase trajectories and
convergence properties in these three SNR regions. This paper
also investigates existence and properties of fixed points in these
SNR regions.
The main fixed points of the turbo decoding algorithm are clas-
sified into two categories. In a wide range of SNRs (corresponding
to bit-error rates less than 10 1), the decoding algorithm has an

  

Source: Agrawal, Rakesh - IBM T.J. Watson Research Center

 

Collections: Computer Technologies and Information Sciences