Hindawi Publishing Corporation Mathematical Problems in Engineering Volume 2013, Article ID 574528, 13 pages http://dx.doi.org/10.1155/2013/574528 Research Article Dynamic Cognitive Self-Organized TDMA for Medium Access Control in Real-Time Vehicle to Vehicle Communications Mario Manzano, 1 Felipe Espinosa, 1 Ángel M. Bravo-Santos, 2 Enrique Santiso, 1 Ignacio Bravo, 1 and David Garcia 1 1 Electronics Department, Polytechnic School, University of Alcala, Campus Universitario s/n, 28871 Alcala de Henares, Spain 2 Signal and Communications Teory Department, Higher Polytechnic School, Carlos III University, Avenida de la Universidad 30, 28911 Leganes, Spain Correspondence should be addressed to Felipe Espinosa; espinosa@depeca.uah.es Received 21 September 2012; Accepted 23 December 2012 Academic Editor: Wuhong Wang Copyright © 2013 Mario Manzano et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Te emergence of intelligent transport systems has brought out a new set of requirements on wireless communication. To cope with these requirements, several proposals are currently under discussion. In this highly mobile environment, the design of a prompt, efcient, fexible, and reliable medium access control, able to cover the specifc constraints of the named real-time communications applications, is still unsolved. Tis paper presents the original proposal integrating Non-Cooperative Cognitive Time Division Multiple Access (NCC-TDMA) based on Cognitive Radio (CR) techniques to obtain a mechanism which complies with the requirements of real-time communications. Tough the proposed MAC uses a slotted channel, it can be adapted to operate on the physical layer of diferent standards. Te authors’ analysis considers the IEEE WAVE and 802.11p as the standards of reference. Te mechanism also ofers other advantages, such as avoiding signalling and the adaptation capacity to channel conditions and interferences. Te solution is applied to the problem of units merging a convoy. Comparison results between NCC- TDMA and Slotted-Aloha are included. 1. Introduction Te massive use of transportation vehicles in our society, and in particular of road transportation, has led to problems of congestion, pollution, and safety [1]. However, current advances in technology are steering the future of transport towards the intelligent transportation systems (ITS) and innovative cooperative transport alternatives [2, 3]. Te frst attempt to standardize the techniques related to ITS was the Digital Short Range Communication (DSRC) [4], developed in the United States in order to meet these commu- nication needs. In the recent years, several organizations have led diferent programs and standardization eforts to cope with the specifc requirements of the ITS [5]. Some of them are the industry consortia C2C-CC (Car to Car Communica- tion Consortium) [6], the IEEE with the protocol suite WAVE (Wireless Access for the Vehicular Environment) [7] or the ISO (International Organization for Standardization) with CALM (Continuous Air-Interface Long and Medium range), and the CVISs project (Cooperative Vehicle Infrastructure Systems) [8]. One of the common factors associated with these stan- dardization activities is that the IEEE 802.11p technology is targeted to be the common V2V data link technology used for trafc safety applications [5]. As mentioned above, the IEEE proposal is the new protocol suite WAVE (Wireless Access in Vehicular Envi- ronments), which includes the description of the protocol IEEE 802.11p, belonging to the widely used 802.11 family of standards [8]. Tis protocol was introduced to solve the limitations inherent in nonuniversal standardization and based on the gained experience. Te aim of developing a universal standard such as WAVE, and therefore 802.11p, is to produce a standard which is generically applicable to the greatest possible number of intelligent transportation systems. Tus, the fnal system