الفهرس 
Wireless Technology OverviewOnly 14 pages are availabe for public view
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Abstract
Over the past 100 years, great advances have been made in the
wireless communication technology. Personal communication devices
now enable communications to and from virtually anywhere on the
planet, and even outside. To improve performance, coverage and
efficiency, modern wireless communication systems utilize digital
signaling techniques. With digital signaling, it is possible to use error
control coding. Recently, a new coding scheme called ”turbo coding”
has generated tremendous interest in channel coding of digital
communication systems due to its high error correcting capability.
Two key innovations in turbo coding are parallel concatenated
encoding and iterative decoding.
A soft-in soft-out component decoder can be implemented using
the maximum a posteriori (MAP) or the maximum likelihood (ML)
decoding algorithm. While the MAP algorithm offers better
performance than the ML algorithm, the computation is complex and
not suitable for hardware implementation. The log-MAP algorithm,
which performs necessary computations in the logarithm domain,
greatly reduces hardware complexity.
With the proliferation of the battery powered devices, power
dissipation, along with speed and area, is a major concern in VLSI
design. The near optimum performance of turbo codes and/or the
performance gains realized via iterative decoding is conditioned upon
reliable knowledge of the channel side information. Lack of this
knowledge can severely degrade the performance of turbo codes
and/or offset any gains that may otherwise have been realized via
turbo processing. Therefore, the need for reliable channel knowledge
necessitates some form of channel estimation at the receiver.
The aim of this thesis is to design and implement an iterative
decoder with a channel estimator then employ and exploit the
estimator to take a decision of terminating the iterations of the turbo
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(iterative) decoder to optimize the decoder power consumption. The
iterative decoder based on the MAP decoding algorithm (which is
categorized as a Trellis-based symbol by symbol estimation
algorithm) uses the channel information given by the estimator to
make a termination operation of the decoding process. The designs of
the decoder and the estimator are combined into one embedded
design.
The thesis demonstrates that an adaptive number of iterations
calculated depending on the channel state offers a power efficient
system than that depending on a fixed number of decoding iterations.