Vehicle-to-vehicle communication for AVCS platooning

\u3cp\u3eVehicle-to-vehicle radio links suffer from power variations, multipath fading and associated Doppler spreading in frequency, as well as interference form other vehicles. These effects are investigated in the context of an Automated Vehicle Control Systems (AVCS) employing vehicle platoons. A statistical model for the channel is considered and the performance of the network involving many links is evaluated. We compare the performance of Time Division Multiple Access (TDMA), Direct Sequence Code Division Multiple Access (DS-CDMA), and Multi-Carrier Code Division Multiple Access (MC-CDMA). Reliability of the radio link is investigated by specifying the radio spectrum occupation for a given required reliability of the radio link.\u3c/p\u3

Future by design: a framework for introducing radical change in urban rail systems

Urban mobility is increasingly becoming accepted as a basic human need, when socio-economic opportunities depend on the ability to reach places within acceptable times. On the other hand, the emergence of megalopoleis as dominant features of the global landscape has been increasing commuting effort to unprecedented levels. These ever-larger urban areas allowed by the dominance of the automobile and their associated travel distances highlight important shortcomings in the operation of mass transport systems. Public transport users in megalopoleis spend up to two times longer than drivers for covering similar distances, exacerbating important social and economic inequalities and reinforcing the preference for private modes. However, even though there is an assumption that the problem can be easily overcome by increasing the speed of transport systems, advocates of this approach overlook important utility trade-offs that arise from the conflict between greater vehicle speeds and the additional time required to access the services. The first original aspect of the thesis is the deeper understanding of the inherent limitations of paradoxes in urban rail systems. For instance, metro systems are inherently constrained by a paradox between access and in-vehicle speeds, which prevents them from offering sufficient door-to-door speeds to cover long distances within acceptable travel times. It becomes clear that these systemic limitations can only be solved by radical innovation, especially in cases where the systems environment is rapidly changing. The first part of the research comprises a literature review on the foundations of engineering to understand how to achieve radical change in socio-technical systems. This in turn leads to the second original aspect of the thesis: a novel heuristic framework that combines the backcasting method with a system engineering approach to develop innovative solutions that are equally robust and resilient in face of the uncertainty of future scenarios. With that, normative scenario building becomes a quantitative process in which benefits, performance, and risks can be analysed and optimised according to different parameters. The second part of the thesis, and its third main original aspect, illustrates the framework in a specific case study of metro systems in megalopoleis. Models are used to identify the functional paradoxes that are used to develop a proposed concept that comprises three main operational foundations. Firstly, an operational strategy where autonomous vehicles stop in different patterns along the line to reduce access times without an impact on in-vehicle times. Secondly, stations are located off the main line to guarantee that all passengers can board their preferred services within minimum headways. Finally, the operational concept adopts autonomous vehicles that travel in platoons and are controlled by vehicle-to-vehicle communication algorithms similarly to automated highways. Results show that this type of solution can potentially improve door-to-door journey times in metro systems if practical barriers can be overcome. In theory, it can reduce the distance between stations to a minimum and thus reduce access time by 50%, while simultaneously increasing in-vehicle speeds by 45% and reduce door-to-door journey times by up to 31% compared to conventional operations. Moreover, capacity can also be increased between 20% and 40% compared to current systems. Therefore, this thesis proposes a series of heuristic steps rooted in normative scenarios to develop operational concepts which are not only innovative but also robust, in a quantitative and verifiable manner. Systems can be functionally modelled, allowing specific technical requirements and specifications to be met in the future. With that, the limitations of current capabilities are reversed from their original position of functional constraint, to a position of normative functional guidelines for development. By focusing on what tools to develop for an ideal system rather than a system that adapts to current tools, this research is a starting point to a new perspective on developing future urban systems