The Implementation of Exit Chart with Log-MAP Algorithm in Turbo Decoding
碩士 === 國立中正大學 === 通訊工程研究所 === 95 === In nowadays, Turbo codes have already been widely applied to many wireless communication systems and yield a remarkable performance approaching Shannon Limit. The turbo encoder consists of two or more traditional convolutional encoders that are connected in paral...
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| Format: | Others |
| Language: | zh-TW |
| Published: |
2007
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| Online Access: | http://ndltd.ncl.edu.tw/handle/05108357626229536157 |
| Summary: | 碩士 === 國立中正大學 === 通訊工程研究所 === 95 === In nowadays, Turbo codes have already been widely applied to many wireless communication systems and yield a remarkable performance approaching Shannon Limit. The turbo encoder consists of two or more traditional convolutional encoders that are connected in parallel or in cascade and then sends out the codeword. Decoding of the received coded messages is based on BCJR algorithm published in 1974. Later on, a log-MAP algorithm derived from BCJR algorithm is published to simplify the decoding computation such that the decoding procedure becomes faster and easier for implementation.
To analyze the convergence behavior of turbo decoding based on iterative log-MAP algorithm, mutual information transfer characteristics of soft in/soft out decoders are proposed as a tool to better understand the convergence behavior of iterative decoding schemes. The exchange of extrinsic information is visualized as a decoding trajectory in the extrinsic information transfer chart (EXIT chart).
In this thesis, we will build up the aforementioned tools following the work by Stephan ten Brink. And then we will simulate the transfer characteristics and the decoding trajectories. We use it to verify that the behavior of decoding trajectories will be predicted appropriately by the transfer characteristics curve.
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