Abstract
A construction of physical-layer Raptor (PLR) codes based on protographs is proposed. We first set up a sequence of signal-to-noise ratios (SNRs). For each SNR, we employ a modified protograph EXIT analysis to find the extra check nodes in addition to the existing check nodes so as to meet the threshold required by the outer low-density parity check code. PLR codes which are capacity-approaching for a wide SNR range can be obtained using the proposed construction. © 1997-2012 IEEE.