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Application Layer Forward Error Correction for Mobile Multimedia Broadcasting
Published in Borko Furht, Syed Ahson, Handbook of Mobile Broadcasting, 2008
Thomas Stockhammer, Amin Shokrollahi, Mark Watson, Michael Luby, Tiago Gasiba
LT-codes, invented by Luby [11], are the first realization of fountain codes. LT-code exhibit excellent overhead and error probability properties. For LT-codes the probability distribution D has a particular form which we describe by outlining its sampling procedure. At the heart of LT-codes is a probability distribution Ω on the integers 1,…,k. This distribution is often called the weight or degree distribution of the LT-code. To create an output symbol, the following procedure is applied: Sample from Ω to obtain an integer w ∈ {1,…,k}. The number w is called the weight or degree of the output symbol.Choose a binary vector (a1,…, ak) of Hamming weight w uniformly at random.Set the value of the output symbol to ⊕i=1kaixi.
Outdoor OWC Links with Diversity Techniques
Published in Z. Ghassemlooy, W. Popoola, S. Rajbhandari, Optical Wireless Communications, 2019
Z. Ghassemlooy, W. Popoola, S. Rajbhandari
The basic idea behind RC is to perform the encoding/decoding process in two separate phases: (i) a pre-coding of the input symbols; and (ii) the subsequent application of an appropriate weakened Luby Transform (LT) code. Note that RC achieves linear encoding and decoding by having the pre-coding scheme based on a low-density parity-check (LDPC) code and using an LT code with an average degree of 3. LT codes show improved performance by reducing the encoding and decoding complexities and decreasing the failure probability [33]. LT codes employ a robust soliton distribution, which guarantees a higher probability of completing the decoding process, at the same overhead, compared to the ideal soliton distribution [40, 42]. Moreover, the encoding and decoding costs scale as K log(K), which is lower than the random linear FCs. In [34], it was shown that unlike RF wireless communications, RC can be used to take advantage of additional degrees of freedom in spatial dimensions in intensity modulation–direct detection FSO systems. In [35], orthogonal space-time block code (OSTBC) was also considered, whereas error control coding together with interleaving was investigated in [36]. However, FSO links employing error control coding with turbulence-induced fading normally require large interleavers in order to attain reasonable coding gains. This is because of the inherent large capacity and high transmission rates of optical systems, which display higher temporal correlation. In [37], the information rates of RC and much more powerful punctured low-density parity-check (LDPC) codes with feedbacks to detect and correct the burst error that results from scintillation was investigated for FSO systems [38], where code evaluation was implemented off-line using the recorded measured data sets. In [38], the LDPC-coded subcarrier intensity modulation–based FSO link under turbulence was reported to achieve a coding gain of more than 20 dB compared with similarly coded OOK.
Performance analysis of LT code-based HARQ error control in underwater acoustic sensor networks
Published in Journal of Marine Engineering & Technology, 2022
P. Kaythry, R. Kishore, V. Nancy Priyanka
The degree distribution aims to prevent the redundant coverage of data packets by the encoding process (Casari et al. 2008). The ideal degree distribution, Robust Soliton distribution for LT codes is given by the following equation: