Cross-layer optimization: Difference between revisions

Revision as of 08:03, 16 March 2019

Revision as of 22:26, 1 October 2019

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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. The cross layer approach transports feedback dynamically via the layer boundaries to enable the compensation for e.g. 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 |accessdate=2008-06-25 |deadurlurl-status=yes dead|archiveurl=https://web.archive.org/web/20080704184307/http://netlab.caltech.edu/pub/papers/tcpip-ton2004.pdf |archivedate=2008-07-04 |df= }} </ref>

In the original OSI networking model, strict boundaries between layers are enforced, where data are 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. 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>

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 |deadurlurl-status=yes 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>

== 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 |dead-url-status=yes 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

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== 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</ref>

== Adapting MAC scheduling based on PHY parameters ==

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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.,

[http://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.