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This paper stands at the intersection of two distinct lines of research. One line is “holographic algorithms,” a powerful approach introduced by Valiant for solving various counting problems in computer science; the other is “normal factor graphs,” an elegant framework proposed by Forney for representing codes defined on graphs.(More)
This paper studies the problem of Raptor-code design for binary-input AWGN (BIAWGN) channels using the mean-LLR-EXIT chart approach presented in [1]. We report that there exist situations where such a design approach may fail or fail to produce capacity-achieving codes, for certain ranges of channel SNR. Suggestions and discussions are provided pertaining(More)
—In this letter, we present a new message-passing schedule for the decoding of low-density parity-check (LDPC) codes. This approach, designated " probabilistic schedule, " takes into account the structure of the Tanner graph (TG) of the code. We show by simulation that the new schedule offers a much better performance/complexity trade-off. This work also(More)
We explore the use of rateless coding for communication over fading channels with delay constraints. Both quasi-static fading and block-fading channels are considered. When only the receiver has channel information, we show there exist rateless codes that are both reliable and efficient for every channel realization of such channels. We then apply these(More)
We consider the problem of reliable transmission of information over unknown AWGN channels using rateless codes and non-uniform modulation techniques. We show that Raptor codes and a form of non-uniform, high-order modulation allow for reliable communication at low SNR, with the ability to automatically adapt rate as the SNR increases. Simulation results(More)
In his recent work, Valiant presented a powerful family of new algorithms, which he calls holographic algorithms. The mathematical foundation of holographic algorithms is what is known as Holant Theorem. Synthesizing from Valiant's work, in this paper, we introduce the notion of Valiant transform for normal graphs. Exploiting this synthesis, we establish a(More)
We have developed an integrated suite of algorithms, statistical methods, and computer applications to support large-scale LC-MS-based gel-free shotgun profiling of complex protein mixtures using basic experimental procedures. The programs automatically detect and quantify large numbers of peptide peaks in feature-rich ion mass chromatograms, compensate for(More)