Raptor code: Difference between revisions

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{{Short description|Fountain code class}}

{{Citation style|date=January 2021}}{{Format footnotes|date=January 2021}}{{about|error correction codes|codebases named raptor|Raptor (disambiguation)}}

In [[computer science]], '''Raptor codes''' ('''''rap'''id '''tor'''nado'';<ref>{{cite speech|author=Amin Shokrollahi|title=The Development of Raptor Codes|event=Invited talk at the [[Kungliga Tekniska högskolan]]|date=31 January 2011|url=http://bambuser.com/v/1372056|accessdate=24 February 2012}}</ref> see [[Tornado code]]s) are the first known class of [[fountain codes]] with linear time encoding and decoding. They were invented by [[Amin Shokrollahi]] in 2000/2001 and were first published in 2004 as an extended abstract. Raptor codes are a significant theoretical and practical improvement over [[LT codes]], which were the first practical class of [[fountain codes]].

{{More citations needed|date=June 2024}}

{{Citation style|date=January 2021}}

In [[computer science]], '''Raptor codes''' ('''''rap'''id '''tor'''nado'';<ref>{{cite speech|author=Amin Shokrollahi |title=The Development of Raptor Codes|event=Invited talk at the [[Kungliga Tekniska högskolan]]|date=31 January 2011 |url=http://bambuser.com/v/1372056|accessdate=24 February 2012}}</ref> see [[Tornado code]]s) are the first known class of [[fountain codes]] with linear time encoding and decoding. They were invented by [[Amin Shokrollahi]] in 2000/2001 and were first published in 2004 as an extended abstract. Raptor codes are a significant theoretical and practical improvement over [[LT codes]], which were the first practical class of [[fountain codes]].

Raptor codes, as with fountain codes in general, encode a given source block of data consisting of a number ''k'' of equal size source symbols into a potentially limitless sequence of encoding symbols such that reception of any ''k'' or more encoding symbols allows the source block to be recovered with some non-zero probability. The probability that the source block can be recovered increases with the number of encoding symbols received above ''k'' becoming very close to 1, once the number of received encoding symbols is only very slightly larger than ''k''. For example, with the latest generation of Raptor codes, the RaptorQ codes, the chance of decoding failure when ''k'' encoding symbols have been received is less than 1%, and the chance of decoding failure when ''k+2'' encoding symbols have been received is less than one in a million. (See ''Recovery probability and overhead'' section below for more discussion on this.) A symbol can be any size, from a single byte to hundreds or thousands of bytes.

Raptor codes may be [[systematic code|systematic or non-systematic]]. In the systematic case, the symbols of the original source block, i.e. the source symbols, are included within the set of encoding symbols. Some examples of a systematic Raptor code is the use by the [[3rd Generation Partnership Project]] in [[mobile cellular wireless]] broadcasting and multicasting, and also by [[DVB-H standard]]s for IP datacast to handheld devices (see external links).{{cn|date=June 2024}} The Raptor codes used in these standards is also defined in [[IETF]] RFC 5053.

[[Online codes]] are an example of a non-systematic fountain code.

== RaptorQ code ==

The most advanced version of Raptor is the RaptorQ code defined in [[IETF]] RFC 6330. The RaptorQ code is a systematic code, can be implemented in a way to achieve linear time encoding and decoding performance, has near-optimal recovery properties (see Recovery probability and overhead section below for more details), supports up to 56,403 source symbols, and can support an essentially unlimited number of encoding symbols.

The RaptorQ code defined in [[IETF]] RFC 6330 is specified as a part of the Next Gen TV ([[ATSC 3.0]]) standard to enable high quality broadcast video streaming (robust mobile TV) and efficient and reliable broadcast file delivery (datacasting). In particular, the RaptorQ code is specified in [A/331 within ATSC 3.0.<ref>{{cite report |date=22 March 2017 |url=https://www.atsc.org/wp-content/uploads/2016/01/A331S33-174r6-Signaling-Delivery-Sync-FEC.pdf A/331|title=ATSC Candidate Standard: Signaling, Delivery, Synchronization, and Error Protection] within(A/331) |id=ATSC 3.0S33-174r6 (see|publisher=Advanced Television Systems Committee}}</ref> See [[List of ATSC standards]] for a list of the ATSC 3.0 standard parts). Next Gen TV (ATSC 3.0) goes well-beyond traditional TV to provide a Broadcast internet enabling general data delivery services.

== Overview ==

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* Greater than 99.99% recovery probability with overhead of 1 symbol (recovery from ''k+1'' received encoding symbols).

* Greater than 99.9999% recovery probability with overhead of 2 symbols (recovery from ''k+2'' received encoding symbols).

These statements hold for the entire range of ''k'' supported in [[IETF]] RFC 6330, i.e., ''k''=1,...,56403. See [[IETF]] RFC 6330 for more details.<ref name="RFC 6330"/>

== Legal status ==

Qualcomm, Inc. has published an IPR statement for the Raptor code specified in [[IETF]] RFC 5053, and an IPR statement for the more advanced RaptorQ code specified in [[IETF]] RFC 6330. These statements mirror the licensing commitment Qualcomm, Inc. has made with respect to the

[[Dynamic Adaptive Streaming over HTTP|MPEG DASH standard]]. The MPEG DASH standard has been deployed by a wide variety of companies, including DASH Industry Forum member companies.

== See also ==

* [[Erasure code]]

* [[Fountain codes]]

* [[LT code]]

* [[Fountain codes]]

* [[Tornado codes]]

== Notes ==

{{reflist}}|refs=

<ref name="RFC 6330">{{cite report |vauthors=Luby M, Shokrollahi A, Watson M, Stockhammer T, Minder L |date=August 2011 |title=Request for Comments: 6330. RaptorQ Forward Error Correction Scheme for Object Delivery |url=http://tools.ietf.org/html/rfc6330 |issn=2070-1721}}</ref>

}}

== References ==

* Shokrollahi, Amin, "Raptor Codes," IEEE Transactions on Information Theory, vol. 52, pp. 2551-2567, 2006. [http://ieeexplore.ieee.org/iel5/18/34354/01638543.pdf?isnumber=34354&prod=JNL&arnumber=1638543&arSt=2551&ared=2567&arAuthor=Shokrollahi%2C+A. PDF] (requires login)

* [[ATSC 3.0]] (Advanced Television Standards Committee 3.0)

* [http://www.3gpp.org 3GPP] (The 3rd Generation Partnership Project)

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* [http://tools.ietf.org/html/rfc5053 RFC5053] Raptor Forward Error Correction Scheme for Object Delivery

* [http://www.dvb-h-online.org/technology.htm DVB-H IP Datacasting specifications]

* [http://tools.ietf.org/html/rfc6330 RFC6330] RaptorQ Forward Error Correction Scheme for Object Delivery

== Further reading ==

* [https://datatracker.ietf.org/ipr/search/?option=rfc_search&rfc_search=5053] "IPR" Search Result for RFC 5053, with statements by some patent owners

* {{cite journal |last=Shokrollahi |first=Amin |title=Raptor Codes |journal=IEEE Transactions on Information Theory |volume=52 |pages=2551-2567 |date=June 2006 |doi=10.1109/TIT.2006.874390 |url=https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=1638543 |url-access=subscription}}

* [https://datatracker.ietf.org/ipr/search/?option=rfc_search&rfc_search=6330] "IPR" Search Result for RFC 6330, with statements by some patent owners

* [https://datatracker.ietf.org/ipr/search/?option=rfc_search&rfc_search=5053] "IPR" Search Result for RFC 5053], with statements by some patent owners

* [https://datatracker.ietf.org/ipr/search/?option=rfc_search&rfc_search=6330] "IPR" Search Result for RFC 6330], with statements by some patent owners

[[Category:Coding theory]]