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In July 2016 this article was marked as probably too hard to understand by nonexperts. I have marked up the most opaque paragraphs. The lead, in particular, needs to be made much clearer for the non expert reader. |
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{{technical|date=July 2016}}
'''Cross-layer optimization''' is an escape from the pure [[waterfall model|waterfall]]-like
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>http://tr.ietejournals.org/downloadpdf.asp?issn=0256-4602;year=2012;volume=29;issue=3;spage=229;epage=247;aulast=Bin-Salem;type=2{{dead link|date=August 2017 |bot=InternetArchiveBot |fix-attempted=yes }}</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 |accessdate=2008-06-25 |url-status=dead|archiveurl=https://web.archive.org/web/20080516005547/http://graphics.stanford.edu/projects/lgl/papers/sab-adhocnow-04/sab-adhocnow-04.pdf |archivedate=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|last=|first=|publisher=Academic Press|year=2010|isbn=9780080879321|___location=Burlington, MA|pages=201–234}}</ref> {{clarify|date=December 2019|text=Differential algorithm systematics modified to the cross-layer interface enables rapid retrieval capabilities when the optimized protocol is defined in dynamic parameters.<ref>{{cite book |last1=Perez-Neira |first1=A |title=Cross-Layer Resource Allocation in Wireless Communications: Techniques and Models from PHY and MAC Layer Interaction |date=2010 |publisher=Academic Press |pages=72-93}}</ref> This effectively exposes the system to bypass allocation, wherein modal gates may be accessible to users for modification regardless of role-defined access level permissions.<ref>{{cite journal |last1=Xi |first1=Y |title=Distributed algorithms for spectrum allocation, power control, routing, and congestion control in wireless networks |journal=Proceedings of the 8th ACM international symposium on Mobile ad hoc networking and computing |date=2007}}</ref>}}
== Applications ==
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