| Summary: | 碩士 === 國立交通大學 === 電信工程研究所 === 99 === Previous studies on low-density parity-check convolutional codes (LDPC-CCs) revealed
that LDPC-CCs with rational parity-check matrices (RPCM) have poor bit-error-rate (BER)
performances due to the existence of lenth-4 cycles in their Tanner graphs. In our recent
work, we found that we can transform the original Tanner graph of an LDPC-CC with an
RPCM into a new Tanner graph with larger girth based on the concept of puncturing such
that the LDPC-CC can have a comparable or even better BER performance than those of
LDPC-CCs with polynomial parity-check matrices (PPCMs). For the decoding of punctured
LDPC codes, sequential schedules are usually used to improve BER performances or
speed up the convergence of the decoding. We select the well-performed ecient dynamic
scheduling (EDS) among the available sequential schedules to decode those LDPC-CCs with
RPCMs in order to obtain better BER performances. In this thesis, we rstly modify the
residual function of EDS to have a more appropriate updating order. Besides, since several
observations indicate that the decoding based on the original EDS or our improved EDS
may not converge or converge to non-optimal codewords, two rened strategies based on the
perturbation and the bit-
ipping are hence proposed to mitigate these problems. Revealed
by the simulations results, not only for RPCMs but also for PPCMs, our proposed algorithm
can provide better BER performances than those of several existent schemes.
|
|---|
