Some Designs of Physical-Layer Raptor Codes
Date Issued
2015
Date
2015
Author(s)
Kuo, Shiuan-Hao
Abstract
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.
Subjects
rateless coding
physical-layer Raptor code
protograph
EXIT analysis
channel capacity
Type
thesis
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