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J. Cerezo Oliva:
"Comparison in the two clusters merging scenario between the IEEE 802.11p MAC protocol and STDMA";
Supervisor: A. Alonso, C. Mecklenbräuker; Institute of Telecommunications, 2012; final examination: 07-11-2012.

IEEE 802.11p is the proposed wireless technology for vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communication in vehicular ad hoc networks (VANETs) with the purpose of increasing road traffic safety. A VANET is characterized by a constantly changing topology and an unlimited number of nodes, so a medium access control (MAC) algorithm with a good scalability is needed to handle transmissions in these type of networks. If, furthermore, we run safety applications on them, which have strict delay requirements, the MAC algorithm needs to achieve predictable delays as well.
The MAC method of IEEE 802.11p is a Carrier Sense Multiple Access (CSMA) scheme, which scales badly in terms of providing timely channel access for a high number of participating nodes. Because of that, another MAC method has been proposed: Self-organizing Time Division Multiple Access (STDMA) with which all nodes achieve timely channel access regardless of the number of participating nodes.
In this work, several performance indicators for both MAC methods are evaluated and compared. These indicators show the behaviour of both MAC algorithms in terms of delay and scalability in a concrete scenario, which is a very common scenario that takes place in highways: two clusters of vehicles moving in opposite directions. In addition, some proposals for future work on this scenario are made, so the 􏰄exibility that STDMA o􏰂ers can be exploited.

WAVE, 802.11p, STDMA, MAC, medium access, vehicular communications, ITS

http://publik.tuwien.ac.at/files/PubDat_208719.pdf