Due to its flexibility, cost-efficiency, and the ability to support mobility, wireless connectivity is seen today as a key enabler for a wide range of applications beyond classical mobile communications. A significant part of these applications depends on the capability of the wireless communication system to provide reliable connectivity. However, due to the randomness of the wireless propagation channel, reliability is still a critical issue in these systems. Some applications, such as vehicular and industrial applications, demand a level of reliability that wireless communication systems typically are not able to guarantee. This paper provides a framework that enables these applications to make use of wireless connectivity only if the transmission conditions are favorable enough. The concept is based on the idea that -despite the fact that it is practically impossible to ensure error-free wireless communication -it is feasible to derive boundary conditions for the transmission success. To this end, the paper introduces a novel metric for UltraReliable Communication (URC) referred to as "Availability", that determines the expected presence or absence of link reliability at the time of transmission. The availability is signaled by means of an Availability Indicator (AI) to the applications. Moreover, we develop the system model for computing the AI and illustrate the potential benefits of the new reliability metric by means of a possible implementation for automotive scenarios.
The combined use of diversity in the time, frequency, and space domains constitutes a powerful instrument to improve the reception of mobile broadcasting services. The improvement brought by the utilization of diversity techniques can be translated into an extended coverage of mobile services, or into a reduction of the network infrastructure. This dissertation addresses the use of diversity for the provision of mobile services in the European family of terrestrial broadcasting systems standardized by the DVB (Digital Video Broadcasting) consortium. This includes the first and second generation systems DVB-T (Terrestrial), DVB-H (Handheld) and DVB-T2 (Terrestrial 2nd Generation), as well as the next generation system DVB-NGH. Nevertheless, the work carried out in this dissertation is of generic nature and can be applied to future evolutions of standards such as the Japanese ISDB-T or the American ATSC. Our investigations employ an information-theoretic approach to obtain the performance limits of diversity techniques, as well as physical layer simulations to evaluate the performance in real systems.The investigations carried out in the context of DVB-T, DVB-H, and DVB-T2 are aimed at the simultaneous delivery of fixed and mobile services in terrestrial broadcasting networks. The convergence of the fixed and mobile paradigms can facilitate the introduction of mobile TV services by allowing the reuse of spectrum, content and infrastructure. The results show that the incorporation of time interleaving (TI) at the physical layer for time diversity, and single-input multiple-output (SIMO) for space diversity are critical for the performance of mobile broadcasting systems. Upper layer FEC (UL-FEC) techniques can be used to achieve time diversity in first generation systems like DVB-T and DVB-H; however, they require the transmission of additional parity data and are not useful for stationary reception. The analysis in terms of link budget reveals that the combined use of time and space diversity is not sufficient to enable the provision of mobile services with acceptable coverage levels in DVB-T and DVB-T2 networks planned for fixed reception. In contrast, diversity techniques can be used in networks planned for portable indoor iii ABSTRACT reception to increase the capacity of vehicular services and extend the coverage of handheld indoor reception.The utilization of combined diversity in the time, frequency, and space domains has been investigated in the context of DVB-NGH, the first broadcasting system to exploit the diversity in the three domains by incorporating at the physical layer long TI, time-frequency slicing (TFS) and multiple-input multiple-output (MIMO). In addition, the adoption of rotated constellations provides better robustness against fading by means of signal-space diversity (SSD).DVB-NGH features an optional satellite component, and has adopted long TI in order to cope with the signal outages that are characteristic of land mobile satellite (LMS) channels. However, the solution adopted in t...
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