| Summary: | 碩士 === 國立清華大學 === 電機工程學系 === 101 === In the encoding of Luby transform (LT) codes, information bits (variable
nodes) are randomly connected to the check nodes. Although the check node
degrees have been optimized for error-rate performance, the arbitrary connec-
tions in the code graph cannot guarantee ecient propagation of the channel
information, and may slowdown the convergence speed of the iterative decod-
ing. This thesis proposed a design of generator matrix such that the channel
information can be eciently propagated through the arranged connections.
In addition, the convergence speed for rateless codes can also be accelerated
using a variety of dierent decoders. The proposed degree-oriented schedul-
ing belief propagation (DOS-BP) updates the decoding messages in the order
of check node degrees, and further reduces the required number of iterations.
The improvement in the convergence speed can be achieved without sacri-
cing the error-rate performance. In the case of Raptor codes, the BER
performance can even be improved.
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