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Raptor Codes (raptor + code)

Distribution by Scientific Domains
Engineering100%

Selected Abstracts

Enhanced system design for download and streaming services using Raptor codes,,

EUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS, Issue 2 2009
Tiago Gasiba
Raptor codes have been recently standardised by 3rd Generation Partnership Project (3GPP) to be used in the application layer (AL) for multimedia broadcast and multicast services (MBMS) including download delivery and streaming delivery. Furthermore, digital video broadcast (DVB) has also recommended the inclusion of these Raptor codes for IP-datacast services. In this paper, enhancements on the system and receiver design using Raptor codes are studied, namely the permeable layer receiver (PLR) and the individual post-repair mechanism. With the PLR, the partial information ignored in the conventional receiver is passed from lower layer to higher layer. We show how a practical and efficient implementation of the Raptor decoder as a PLR can be done, which can not only achieve huge performance gains, but the gains can be achieved at an affordable low decoding complexity. Whereas the PLR is employed for enhancing both download and streaming services, the post-repair aims at guaranteeing reliable download delivery when a feedback channel is available. We propose here two efficient post-repair algorithms which fully exploit the properties of the Raptor codes. One allows to find a minimum set of source symbols to be requested in the post-delivery, and another allows to find a sufficient number of consecutive repair symbols. Selected simulations verify the good performance of proposed techniques. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Achieving a near-optimum erasure correction performance with low-complexity LDPC codes

INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 5-6 2010
Gianluigi Liva
Abstract Low-density parity-check (LDPC) codes are shown to tightly approach the performance of idealized maximum distance separable (MDS) codes over memoryless erasure channels, under maximum likelihood (ML) decoding. This is possible down to low error rates and even for small and moderate block sizes. The decoding complexity of ML decoding is kept low thanks to a class of decoding algorithms, which exploit the sparseness of the parity-check matrix to reduce the complexity of Gaussian elimination. ML decoding of LDPC codes is reviewed at first. A performance comparison among various classes of LDPC codes is then carried out, including a comparison with fixed-rate Raptor codes for the same parameters. The results confirm that a judicious LDPC code design allows achieving a near-optimum performance over the erasure channel, with very low error floors. Furthermore, it is shown that LDPC and Raptor codes, under ML decoding, provide almost identical performance in terms of decoding failure probability vs. overhead. Copyright © 2010 John Wiley & Sons, Ltd. [source]