DESIGN OF SOME NEW EFFICIENT SECOND-ORDER SPECTRAL-NULL CODES
| Autor: | Dong-Jing Lee, 李東璟 |
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| Rok vydání: | 2006 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 94 This thesis focuses on studying the second-order spectral-null (2-OSN) code. 2-OSN code can achieve a larger rejection of low-frequency components than first-order spectral-null (1-OSN) code besides has the capability of one error correcting. 1-OSN code is also called balanced code, the encoded sequence itself contains no low-frequency components and it provided the noises can be avoided by high-pass filter besides has the capability of all unidirectional error detection. So-called unidirectional error means only one type of error can occurs in a codeword is different from symmetric error which a codeword may contains two types of error, 1-error (1 to 0) and 0-error (0 to 1). In the recent day, unidirectional error control codes play an important role on reliable data communication over optical fiber and optical storage system, and some researches point out the errors occur in VLSI memory are also unidirectional. Hence, 2-OSN codes can be employed in many circumstances. The construction for 2-OSN code is to encode the information to balanced code and then use 2-order balance function to transform balanced code to 2-OSN code. Afterwards, encode the index outputted by 2-order balance function recursively. In this thesis, we propose two methods to construct 2-OSN codes with the capability of one error correcting and all unidirectional error detection (1-EC/AUED). The proposed methods include: (1) the design of extended basic codes (EBC) that increases the available index values, (2) the technology of new balance function reduces the required index span. These two strategies can reduce the overall code length efficiently. EBC is to extend the original basic optimal codes to encode 2-OSN code as one recursive step. This design can obtain not only more available indexes but also fewer computations. The new 2-order balance function using cyclic bit shift (CBS) balance function requires few indexes and also reduces the computations remarkably. Besides, these two methods are different in nature and independent. They can be integrated to construct more efficient code. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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