Combined Time, Frecuency and Space Diversity in Multimedia Mobile Broadcasting Systems

Abstract

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...