RATELESS CODES THESIS

Liquid Cloud Storage is based on using a large erasure code such as the RaptorQ code specified in IETF RFC which provides significantly better data protection than other systems , using a background repair process which significantly reduces the repair bandwidth requirements compared to other systems , and using a stream data organization which allows fast access to data even when not all encoded symbols are available. To this end, we commence by considering the concatenation of Luby transform LT codes, which were the first practical realization of rateless codes, with differential modulators to exploit the inherent coding gain of differential modulations. Repairable fountain codes [5] are projected to address fountain code design objectives for storage systems. It may include eg previous versions that are now no longer available. A different approach to distributed storage using fountain codes has been proposed in Liquid Cloud Storage [7] [8].

The results presented in this thesis aim at providing insight into the fundamental design of rateless codes, which could serve as a guideline for the optimal design of rateless codes in real-world applications. Finally, a design framework is provided for DLT coding schemes, to jointly improve the transmission efficiency and erasure floor performance. By using this site, you agree to the Terms of Use and Privacy Policy. A fountain code is inherently rateless, and as a consequence, such codes may potentially generate an unlimited number of encoded symbols on the fly. Fountain codes are flexibly applicable at a fixed code rate , or where a fixed code rate cannot be determined a priori, and where efficient encoding and decoding of large amounts of data is required.

A different approach to distributed storage using fountain codes has been proposed in Liquid Cloud Storage [7] [8].

Analysis and Design of Rateless Codes

Thesis kB downloads. The invention of turbo codes and the re-discovery of sparse graph codes constitute a milestone in error-correction codes designed for communication and storage systems.

ratekess

Fountain codes are flexibly applicable at a fixed code rateor where a fixed code rate cannot be determined a priori, and where efficient encoding and decoding of large amounts of data is required. When a single encoded symbol is lost, it should not require too much communication and computation among other encoded symbols in order to resurrect the lost symbol. Coding theory Capacity-approaching codes. To observe the consequences of the modified encoding scheme, the convergence behavior of the proposed LT code is analyzed using EXIT charts, and shown to be similar to the convergence performance of conventional LT codes.

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Handbook of Mobile Broadcasting: Repairable fountain codes [5] are projected to address fountain code design objectives for storage systems. A fountain code is optimal if the original k source symbols can be recovered from any k encoding symbols.

To address the shortcomings of existing distributed LT DLT codes, we introduce buffer-based DLT codes for a multi-source and multi-relay network to virtually convert lossy source-relay links to corresponding lossless links.

By using this site, you agree to the Terms of Use and Privacy Policy. Views Read Edit View history. Raptor codes are the most efficient fountain codes at this time, [2] having very efficient linear time encoding and decoding algorithms, and requiring only a small constant number of XOR operations per generated symbol for both encoding and decoding. A detailed survey about fountain codes and their applications can be found at. We optimize the proposed DLT codes in terms of transmission efficiency; thus exhibiting better performance as compared to their conventional counterparts at the expense of increased computational complexity.

The results presented in this thesis aim at providing insight into the fundamental design of rateless codes, which could serve as a guideline for the optimal design of rateless codes in real-world applications. LT codes were the first practical realization of fountain codes. To address the shortcomings of existing distributed LT DLT codes, we introduce buffer-based DLT codes for a multi-source and multi-relay network to virtually convert lossy source-relay links to corresponding lossless links.

Using a fountain code, it suffices for a receiver to retrieve any subset of encoding symbols of size slightly larger than the set of source symbols.

The requirements of erasure code design for data storage, particularly for distributed storage applications, might be quite different relative to communication or data streaming scenarios. From Wikipedia, the free encyclopedia. One example is that of a data carouselwhere some large file is continuously broadcast to a set of receivers.

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In practice, the broadcast is typically scheduled for a fixed period of time by an operator based on characteristics of the network and receivers and desired delivery reliability, and thus the fountain code is used at a code rate that is determined dynamically at the time when the file is scheduled to be broadcast. The second part of the thesis deals with the analysis and design of rateless codes for multi-point communication. The thesis is divided into two parts.

Fountain code

In fact, repair latency might sometimes be more important than storage space savings. An algorithm is developed based on the extrinsic information transfer EXIT chart to obtain optimized degree distributions of LT coded differential modulator systems in terms of convergence performance. The number of downloads is the sum of all downloads of full texts.

Another application is that of hybrid ARQ in reliable multicast scenarios: The rzteless presented in this thesis aim at providing insight into the fundamental design of rxteless codes, which could serve as a guideline for the optimal design of rateless codes in real-world applications.

rateless codes thesis

Cdes fountain code is inherently rateless, and as a consequence, such codes may potentially generate an unlimited number of encoded symbols on the fly. One of the requirements of coding for data storage systems is the systematic form, i. Then, we delve deeper into the characteristics of LT codes with the objective of improving the error floor performance over noisy channels. It may include eg previous versions that are now no longer available. Then, we delve deeper into the characteristics of LT codes with the objective of improving the error floor performance over noisy channels.

Finally, a design framework is provided for DLT coding schemes, to jointly improve the transmission efficiency and erasure floor performance.

rateless codes thesis