Cross-layer optimization: Difference between revisions

Revision as of 19:33, 28 October 2020

Revision as of 21:12, 15 December 2020

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{{technical|date=July 2016}}

'''Cross-layer optimization''' is an escape from the pure [[waterfall model|waterfall]]-like concept of the [[OSI model|OSI communications model]] with virtually strict boundaries between layers. {{clarify|date=December 2019|text=The cross layer approach transports feedback dynamically via the layer boundaries to enable the compensation for overload, latency or other mismatch of requirements and resources by any control input to another layer, but that layer directly affected by the detected deficiency.<ref>http://www.ece.purdue.edu/~shroff/Shroff/journal/LSS06.pdf{{Dead link |date=November 2017}}</ref><ref>{{cite web |url=http://netlab.caltech.edu/pub/papers/tcpip-ton2004.pdf |title=Archived copy |accessdateaccess-date=2008-06-25 |url-status=dead|archiveurlarchive-url=https://web.archive.org/web/20080704184307/http://netlab.caltech.edu/pub/papers/tcpip-ton2004.pdf |archivedatearchive-date=2008-07-04 |df= }}</ref>}}

Strict boundaries between layers are enforced in the original OSI networking model, where data is kept strictly within a given layer. Cross‑layer optimization removes such strict boundaries to allow communication between layers by permitting one layer to access the data of another layer to exchange information and enable interaction. {{clarify|date=December 2019|text=For example, having knowledge of the current physical state will help a channel allocation scheme or automatic repeat request (ARQ) strategy at the MAC layer in optimizing tradeoffs and achieving throughput maximization.<ref>[https://archive.today/20130415081707/http://tr.ietejournals.org/downloadpdf.asp?issn=0256-4602;year=2012;volume=29;issue=3;spage=229;epage=247;aulast=Bin-Salem;type=2]</ref>}}

{{clarify|date=December 2019|text=Especially in information routing with concurrent demand for limited capacity of channels there may be a need for a concept of intervention to balance between e.g. the needs of intelligible speech transmission and of sufficiently dynamic control commands. Any fixed allocation of resources will lead to a mismatch under special conditions of operations.}} Any highly dynamic change of resource allocation might affect the intelligibility of voice or the steadiness of videos. However, as with other optimizing strategies, the algorithm consumes time as well.<ref>{{cite web |url=http://graphics.stanford.edu/projects/lgl/papers/sab-adhocnow-04/sab-adhocnow-04.pdf |title=Archived copy |accessdateaccess-date=2008-06-25 |url-status=dead|archiveurlarchive-url=https://web.archive.org/web/20080516005547/http://graphics.stanford.edu/projects/lgl/papers/sab-adhocnow-04/sab-adhocnow-04.pdf |archivedatearchive-date=2008-05-16 |df= }}</ref>

== Principles ==

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* The Chaos of Unbridled Cross-Layer Design

Unlike a traditional architectural design approach, where designers can focus on a single problem without worrying about the rest of the protocol stack, one must be careful to prevent unintended effects on other parts of the system. Dependency graphs are helpful for adaptation loops that occur using cross-layer design. <ref name=":02">{{Cite book|title=Cognitive Radio Communications and Networks : Principles and Practice|url=https://archive.org/details/cognitiveradioco00wygl|url-access=limited|last=|first=|publisher=Academic Press|year=2010|isbn=9780080879321|___location=Burlington, MA|pages=[https://archive.org/details/cognitiveradioco00wygl/page/n223 201]–234}}</ref>

== Applications ==

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* adaptation

* scheduling

* resource allocation<ref>{{Cite journal|last=Karmokar|first=Ashok|date=21 November 2012|title=Energy-Efficient Green Radio Communications for Delay Tolerant Applications|url=https://www.sciencedirect.com/science/article/pii/B9780124158443000073|journal=Handbook of Green Information and Communication Systems|volume=|pages=|via=}}</ref>

* power control

* congestion control

* multihop routing<ref>{{Cite journal|last=Wymeersch|first=Henk|date=2016|title=Multiple access control in wireless networks|url=|journal=Academic Press Library in Mobile and Wireless Communications: Transmission Techniques for Digital Communications|volume=|pages=|via=}}</ref>

Its advantages include high adaptivity in a [[Wireless sensor network]] and a larger optimization space.<ref name=":02" />

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== Adjusting quality of service ==

Cross-layer optimization shall contribute to an improvement of quality of services under various operational conditions. Such [[adaptive quality of service]] management is currently subject of various patent applications, as e.g.<ref>{{Cite web |url=http://www.patentstorm.us/patents/7339897.html |title=Cross-layer integrated collision free path routing - US Patent 7339897<!-- Bot generated title --> |access-date=2008-06-25 |archive-url=https://web.archive.org/web/20110612185123/http://www.patentstorm.us/patents/7339897.html |archive-date=2011-06-12 |url-status=dead|df= }}</ref>

The cross-layer control mechanism provides a feedback on concurrent quality information for the adaptive setting of control parameters. The control scheme apply

* the observed quality parameters