Propuesta de sistema de comunicación inalámbrica basado en la integración del estándar Wave y técnicas de radio cognitiva para la optimización de sistemas inteligentes de transporte

Abstract

The massive use of transportation systems in our society has produced three areas of potential research: transport effectiveness, energy efficiency and transport safety. The transport effectiveness will provide the possibility of decreasing congestion and the journey lengths. Energy efficiency will bring a reduction of the environmental impact of the human activities related to transport. Transport safety will decrease the number of fatalities in transport. The application of the information and communication technologies in this field in order to solve the mentioned problems leads us to the Intelligent Transportation Systems (ITS). In road transportation there are lots of applications which are built over the wireless communication system, either car to car or car to infrastructure. In order to define some common requirements for these communication environments, there are several international organisms that have developed different specifications to standardize the wireless communications in the vehicular environment, as the WAVE standard (Wireless Access for Vehicular Environment) defined by IEEE. However, some specific applications for the vehicular environment demand real-time communications requirements in order to ensure the vehicles and passengers safety. One of these applications in which is mandatory to meet the real time communication requirements is the cooperative guidance of autonomous vehicles in formation. In this type of applications the information must reach its destination within a specified maximum deadline which cannot be exceeded. This is the main characteristic of the real time communication in ITS. In this thesis, the following medium access control mechanisms have been developed: NCCTDMA (Non Cooperative Cognitive Time Division Multiple Access) and ENCCMA (Enhanced Non Cooperative Cognitive Multiple Access). Both of them use cognitive radio techniques as spectrum sensing and dynamic spectrum access in order to obtain schedule based and self-organized mechanisms (a central node to propagate the schedule is not required). These mechanisms does not require the exchange of protocol signaling. These characteristics give users of these mechanisms the ability to manage themselves autonomously in a wireless vehicular network while meeting the real time communication requirements in the field of ITS. To achieve that, an analysis of different proposals found in the literature has been performed; cognitive radio techniques and other ones related to spectrum sensing and dynamic spectrum access have been studied and applied in the design of the medium access control mechanisms and, to evaluate the designed mechanisms, simulation tools have been implemented to measure its performance in several scenarios. In addition, a description of a parallel work related to this thesis, the implementation of a physical prototype of WAVE, has been included