摘要
實體層猛禽碼為一種無碼率編碼，傳統上能針對單一訊雜比做最佳化。文獻已證實於二元輸入高斯雜訊通道中，可以適用所有訊雜比的通用猛禽碼並不存在，但達到準通用的猛禽碼設計應是可能的。本論文將針對非系統性碼與系統性碼，探討此種猛禽碼的可行性。論文主體分三部份。第一部份提出可適性非系統性猛禽碼的設計，使其可於一個廣泛的雜訊比範圍內逼近通道容量。此設計利用可適性度分布，於傳送中能逐次改變度分布。第二部份研究盧比變換-累加碼之設計。此編碼移除猛禽碼中做為外碼之低密度奇偶檢查碼，改採用累加器做為盧比變換碼之內碼。最後一部分提出一個根據原模圖的系統性猛禽碼設計。藉由原模圖外在資訊傳遞的分析，可以根據舊有原模圖盧比變換碼之檢查節點，找出最適合之新檢查節點。此方法能建構出在一個廣泛訊雜比範圍內逼近通道容量的系統性猛禽碼。
並列摘要
The phisical-layer Raptor (PLR) code is a class of rateless coding that can be constructed to achieve a rate close to the capacity of the binary-input AWGN (BIAWGN) channel with a fixed signal-to-noise ratio (SNR). It has been proved that there does not exist an universal PLR code that has capacity achieving ability for all channel conditions of BIAWGN channels. Nevertheless, PLR codes with quasi-universality that can be capacity-approaching in an SNR range is possible. In this dissertation, we study such PLR codes for both non-systematic and systematic case. In the first part, we propose a constructive approach of designing the non-systematic PLR code such that the achieved rates are close to the associated capacities for wide SNR ranges. The proposed adaptive PLR code employs an adaptive degree distribution that is constructed based on the concept of switching degree distributions during transmission. In the second part, we study the design of LT-accumulate code that concatenates an inner accumulator to the LT code instead of an outer low-density parity check (LDPC) code. In the last part, a construction of systematic PLR codes based on protographs is proposed. A modified protograph EXIT analysis is employed to find the extra check nodes in addition to the existing check nodes so as to meet the threshold required by the outer LDPC code. Systematic PLR codes which are capacity approaching for a wide SNR range can be obtained using the proposed algorithm.