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'''Multiple Access with Collision Avoidance for Wireless''' ('''MACAW''')<ref name="MACAW">{{cite journal|author=Vaduvur Bharghavan|title=MACAW: A Medium Access Protocol for Wireless LAN's|url=http://pdos.csail.mit.edu/decouto/papers/bharghavan94.pdf|version=In the Proc. ACM SIGCOMM Conference (SIGCOMM '94), August 1994, pages 212-225|date=1994-08-01|accessdate=2007-01-18|display-authors=etal}}</ref> is a slotted [[medium access control]] (MAC) protocol widely used in [[ad hoc network]]s.<ref name="SMAC_1">{{cite journal |author=Wei Ye|title=An Energy-Efficient MAC Protocol for Wireless Sensor Networks |url=http://www.isi.edu/~weiye/pub/smac_infocom.pdf|version=INFOCOM 2002|date=2002-06-01|accessdate=2006-11-26 |archiveurl = https://web.archive.org/web/20061104045110/http://www.isi.edu/~weiye/pub/smac_infocom.pdf |archivedate = 2006-11-04|display-authors=etal}}</ref> Furthermore, it is the foundation of many other [[Medium Access Control|MAC]] protocols used in [[wireless sensor networks]] (WSN).<ref name="SMAC_1"/> The [[IEEE 802.11 RTS/CTS]] mechanism is adopted from this protocol.<ref name="SMAC_2">{{cite journal |author=Wei Ye|title=Medium Access Control With Coordinated Adaptive Sleeping for Wireless Sensor Networks |url=http://www.isi.edu/~weiye/pub/smac_ton.pdf|version=IEEE/ACM Transactions on Networking, Vol. 12, No. 3, pp. 493-506, June 2004|date=2004-06-01|accessdate=2006-12-27 |archiveurl = https://web.archive.org/web/20061209195620/http://www.isi.edu/~weiye/pub/smac_ton.pdf |archivedate = 2006-12-09|display-authors=etal}}</ref><ref name=holger>{{cite book | last = Karl| first = Holger | authorlinkauthor-link = Holger Karl | year = 2005| title =Protocols and Architectures for Wireless Sensor Networks | url = https://archive.org/details/protocolsarchite00karl| url-access = limited| publisher = Wiley | isbn = 0-470-09510-5 | page = [https://archive.org/details/protocolsarchite00karl/page/n144 117]}}</ref> It uses ''RTS-CTS-DS-DATA-ACK'' frame sequence for transferring data, sometimes preceded by an ''RTS-RRTS'' frame sequence, in view to provide solution to the [[hidden node problem]].<ref name="MACAW"/> Although protocols based on MACAW, such as [[S-MAC]], use [[carrier sense]] in addition to the RTS/CTS mechanism, MACAW does not make use of carrier sense.<ref name="MACAW"/>
== Principles of operation ==
==Ongoing research==
Additional back-off algorithms have been developed and researched to improve performance.<ref name=Miao>{{cite book|author1=[[Guowang Miao]]|author-link=Guowang Miao|author2=Guocong Song|title=Energy and spectrum efficient wireless network design|publisher=[[Cambridge University Press]]|isbn=1107039886|year=2014}}</ref><ref>P. Venkata Krishna, Sudip Misra, [[Mohammad S. Obaidat|Mohhamed S. Obaidat]] and V. Saritha, “Virtual Backoff Algorithm: An Enhancement to 802.11 Medium Access Control to Improve the Performance of Wireless Networks” in IEEE Trans. on Vehicular Technology (VTS), 2010</ref><ref>Sudip Misra, P. Venkata Krishna and Kiran Issac Abraham, “Learning Automata Solution for Medium Access with Channel Reservation in Wireless Networks” accepted in Wireless Personal Communications (WPS), Springer</ref><ref>P. Venkata Krishna & N.Ch.S.N. Iyengar “Design of Sequencing Medium Access Control to improve the performance of Wireless Networks” Journal of Computing and Information Technology (CIT Journal), Vol. 16, No. 2, pp. 81-89, June 2008.</ref><ref>P.Venkata Krishna & N.Ch.S.N.Iyengar, 'Sequencing Technique – An Enhancement to 802.11 Medium Access Control to improve the performance of Wireless Networks', Int. J. Communication Networks and Distributed Systems, Vol.1, No.1, pp 52-70, 2008</ref> The basic principle is based on the use of sequencing techniques where each node in the wireless network maintains a counter which limits the number attempts to less than or equal to the sequence number or use wireless channel states to control the access probabilities so that a node with a good channel state has a higher probability of contention success.<ref name="Miao"/> This reduces the number of collisions.
=== Unsolved problems ===
== References ==
{{Reflist}}
<references/>
{{Channel access methods}}
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