本研究計畫提出建構與解碼一類不規則的光纖LDPC 碼，其建構特色在把檢查矩陣分為兩部分：使用者設計部分、與固定型態部分。後者的矩陣部分為可逆，其圈長為無窮大。而使用者設計的部分，則使用結合密度進化法與進化演算法， 以達到最佳節點維度分佈。 LDPC 解碼則採用階層式解碼， 第一層採用信息傳遞(Message Passing, MP)法，第二層採用「自由位元結合非同步運算」的演算法，以確保解碼的BER 要求。此第二層法目的在改進當MP 解碼法失敗時，若不作重送之條件時，如何以軟解碼作快速與非同步運算之法作解決之道。 LDPC 碼亦極適合速率相容的(rate-compatible, RC) 的通道條件適應，本研究將發展如何藉增加或減少檢查矩陣中的矩陣成員，達到最佳節點維度分佈， 並設計RC 編碼與解碼之目標。本研究將研討在10-Gb/s 光纖傳輸時碼長約1000 時， 與其他碼 (Reed-Solomon 與BCH 碼)之誤碼率比較。至於光碼之實踐，則使用波導陣列 (AWG)作有效之架構。 ; In this project we present a class of optical irregular LDPC codes by constructing the parity check matrix from two parts: a user designed part and a fixed pattern part. The later is an invertible matrix of infinite girth. The former is obtained by using density evolution and evolution algorithm to yield node degree distribution. A two layer decoding method is also proposed. The first layer adopts the message passing (MP) method, and the second one is named as the free-bit- parallel algorithm (FBPA). The purpose of the second layer is to improve the decoding failure of the MP method. We also present a class of rate-compatible (RC) LDPC code for various values desired code rate by judiciously adjusting the columns of the parity check matrix. The decoding method for the resulted RC LDPC code is also discussed. We will consider an optical fiber transmission of 10-Gb/s with code length 1000. Performance comparison between various codes such as Reed-Solomon or BCH codes will be shown. Array wave guides (AWG) will be used for the implementation of the designed optical code. ; 研究期間 9708 ~ 9807
