Space-Time Processing Applications for Wireless Communications

Sammanfattning: Wireless mobile communication networks are rapidly growing at an incredible rate around the world and a number of improved and emerging technologies are seen to be critical to the improved economics and performance of these networks. The technical revolution and continuing growth of mobile radio communication systems has been made possible by extraordinary advances in the related fields of digital computing, high-speed circuit technology, the Internet and, of course, digital signal processing. Improved third generation (3G) and future generation wireless communication systems must support a substantially wider and enhanced range of services with respect to those supported by second generation and basic 3G systems. The never-ending quest for such personal and multimedia services, however, demands technologies operating at higher data rates and broader bandwidths. This combined with the unpredictability and randomness of the mobile propagation channel has created many new technically challenging problems for which innovative, adaptive and advanced signal processing techniques may offer new and better solutions. Space-time processing techniques have emerged as one of the most promising areas of research and development in wireless communications for the efficient utilization of the physical mobile radio propagation channel. Space-time processing signifies the signal processing performed on a system consisting of several antenna elements, whose signals are processed adaptively in order to exploit both the spatial (space) and temporal (time) dimensions of the radio channel. This can significantly improve the capacity, coverage, quality and energy efficiency of wireless systems. This thesis expands the scope of space-time processing by proposing novel applications in wireless communication systems. These include the reduction of possibly harmful electromagnetic radiation from mobile phones, enhancing the quality of Bluetooth links in indoor office environments, increasing the spectral efficiency of satellite and the novel high altitude platforms (HAPs) communication systems, enhancing the coverage and capacity of integrated multiple-HAP 3G systems, and improving the energy efficiency of cooperative wireless sensor networks. The performance of these systems is assessed by theoretical analysis, by computer simulations under a range of propagation environments including realistic channel models, advanced commercial electromagnetic modeling software, and a proposed novel multi-channel simulator suitable for various space-time applications.