Cross-layer optimization: Difference between revisions

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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>{{Cite web |url=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|datetitle=AugustIETE 2017Technical Review : Paid Content |botarchive-url=InternetArchiveBothttps://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 |fixarchive-attempteddate=yes15 April 2013 |url-status=dead}}</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|volumepages=183–208|pagesdoi=10.1016/B978-0-12-415844-3.00007-3|isbn=9780124158443|viaurl-access=subscription}}</ref>

* power control

* congestion control

* multihop routing<ref>{{Cite journalbook|last=Wymeersch|first=Henk|date=2016|title=Multiple access control in wireless networks|url=|journal=Academic Press Library in Mobile and Wireless Communications: Transmission|date=2016|chapter=Multiple Techniquesaccess forcontrol Digitalin Communicationswireless networks|volumepages=435–465 |pagespublisher=Academic Press |viadoi=10.1016/B978-0-12-398281-0.00012-0|isbn=978-0-12-398281-0 }}</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

* a [[fuzzy logic]] based reasoning about applying the appropriate control strategy

* the statistically computed control input to parameter settings and mode switches

== Tailoring to resource efficiency of cross-layer==

The quality aspect is not the only approach to tailor the cross-layer optimization strategy. The control adjusted to availability of limited resources is the first mandatory step to achieve at least a minimum level of quality. Respective studies have been performed and will continue.<ref>http://www.nyman-workshop.org/2003/papers/Cross-Layer%20Optimization%20for%20Sensor%20Networks.pdf {{Webarchive|url=https://web.archive.org/web/20080828183649/http://www.nyman-workshop.org/2003/papers/Cross-Layer%20Optimization%20for%20Sensor%20Networks.pdf |date=2008-08-28 }} {{Bare URL PDF|date=March 2022}}</ref>

== Adapting MAC scheduling based on PHY parameters ==

Communication systems that need to operate over media with non stationary background noise and interference may benefit from having a close coordination between the [[Medium access control|MAC]] layer (which is responsible for scheduling transmissions) and the [[Physical layer|PHY]] layer (which manages actual transmission and reception of data over the media).<ref>S. Shabdanov, P. Mitran, C. Rosenberg,

[httphttps://ieeexplore.ieee.org/xpldocument/login.jsp?tp=&arnumber=6151784&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D6151784/ "Cross-Layer Optimization Using Advanced Physical Layer Techniques in Wireless Mesh Networks", in IEEE Transactions on Wireless Communications]</ref><ref name=Miao>{{cite book|author1=Guowang Miao|author2=Guocong Song|title=Energy and spectrum efficient wireless network design|publisher=[[Cambridge University Press]]|isbn=978-1107039889|year=2014|author1-link=Guowang Miao}}</ref>

<ref>S. Shabdanov, P. Mitran, C. Rosenberg,

[http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=6151784&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D6151784 "Cross-Layer Optimization Using Advanced Physical Layer Techniques in Wireless Mesh Networks", in IEEE Transactions on Wireless Communications]</ref><ref name=Miao>{{cite book|author1=Guowang Miao|author2=Guocong Song|title=Energy and spectrum efficient wireless network design|publisher=[[Cambridge University Press]]|isbn=978-1107039889|year=2014|author1-link=Guowang Miao}}</ref>

In some communications channels (for example, in power lines), noise and interference may be non-stationary and might vary synchronously with the 50 or 60&nbsp;Hz [[AC current]] cycle. In scenarios like this, the overall system performance can be improved if the MAC can get information from the PHY regarding when and how the noise and interference level is changing, so that the MAC can schedule transmission during the periods of time in which noise and interference levels are lower.<ref name="Miao"/>

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== Issues ==

Some issues may arise with cross-layer design and optimization by creating unwanted effects as explained in.<ref>V. Kawadia, P.R. Kumar, [http://ieeexplore.ieee.org/Xplore/login.jsp?url=/stamp/stamp.jsp?arnumber=01561928 "A cautionary perspective on cross-layer design"], in: IEEE Wireless Communications, Volume 12, Issue 1, Feb. 2005.{{Dead link |date=November 2017}}</ref><ref>P. Papadimitratos, A. Mishra, and D. Rosenburgh, [https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=1605922 "A Cross-Layer Design Approach to Enhance 802.15.4"], in: IEEE MILCON 2005, Volume 3, pp 1719-1726, June 2005</ref> Cross-layer design solutions that allow optimized operation for mobile devices in the modern heterogeneous wireless environment are described in,<ref>F. Foukalas et al.,

[httphttps://ieeexplore.ieee.org/xpl/articleDetails.jsp?tp=&arnumber=4483671&contentType=Journals+%26+Magazines&sortType%3Dasc_p_Sequence%26filter%3DAND%28p_IS_Number%3A4483664%29 "Cross-layer design proposals for wireless mobile networks: a survey and taxonomy "]</ref> where in addition the major open technical challenges in the cross-layer design research area are pointed out.

== See also ==

*[[OSI model]]

*[[Cognitive networks]]

*[[OSI model]]

== References ==

{{Reflist}}

<references/>

{{Authority control}}

[[Category:OSI protocols]]