Nedeljko Varnica

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We propose an augmented belief propagation (BP) decoder for low-density parity check (LDPC) codes which can be utilized on memoryless or intersymbol interference channels. The proposed method is a heuristic algorithm that eliminates a large number of pseudocodewords that can cause nonconvergence in the BP decoder. The augmented decoder is a multistage(More)
Two incremental redundancy hybrid ARQ (IR-HARQ) schemes are compared: one is based on LDPC code ensembles with random transmission assignments, the other is based on recently introduced Raptor codes. A number of important issues, such as rate and power control, and error rate performance after each transmission on time varying binary-input, symmetric-output(More)
Two incremental redundancy hybrid ARQ (IR-HARQ) schemes are proposed, analyzed, and compared: one is based on LDPC code ensembles with random transmission assignments, the other is based on recently introduced Raptor codes. A number of important issues, such as rate and power control, Raptor code design, and error rate performance after each transmission on(More)
An LDPC code based hybrid ARQ scheme with random transmission assignments is analyzed. The spectrum properties of LDPC code ensembles that are necessary for this analysis are derived. Very good estimates of maximum-likelihood decoding error rates after each transmission are provided. The results are tested on practical code examples by simulation
In this paper, we design capacity-approaching codes for partial response channels. The codes are constructed as concatenations of inner trellis codes and outer low-density parity- check (LDPC) codes. Unlike previous constructions of trellis codes for partial response channels, we disregard any algebraic properties (e.g., the minimum distance or the(More)
The i.i.d. rate of a channel is the mutual information rate between the channel input and the channel output when the channel input symbols are independent, identically distributed (i.i.d.) and equally likely. We design a coding strategy that achieves rates higher than the i.i.d. rate of a partial response channel (intersymbol interference channel with(More)
In this letter we provide several methods to improve belief-propagation (BP) decoding of low-density parity-check codes. The methods use additional processing of the decoded information during the decoding process and are grouped into two categories. The first category is useful in the waterfall performance region and is based on processing averaged(More)
Multiple description codes are data compression algorithms designed with the goal of minimizing the distortion caused by data loss in packet-based or diversity communications systems. Recently, techniques that achieve multiple description coding by combining embedded source codes with unequal error protection channel codes have become popular in the(More)