Abstract
Since the first generation of mobile communication systems (IG), mobile services have been relying on ground-based infrastructures. However, the increasing mobile services demand on higher frequencies and higher data rates has been urging the ground-based systems to have far more sites. With a limited number of appropriate sites, achieving seamless coverage and supporting high user mobility may not be cost effective. On the other hand, satellites have been operated to gain regional or global mobile communications coverage and offer high user mobility. Yet these space-based infrastructures have high latency (i.e. propagation delays) and propagation loss that substantially limit the system capacity and make the user terminals expensive. Hence, for about a decade, aerial platforms have been studied and recognised as potential sky-based infrastructures as part of the future mobile communications. In the year 2000, High Altitude Platform Station (HAPS) has been accepted as an alternative infrastructure for the third generation of mobile communication systems (3G) such as UMTS. However, most of the attention is currently more towards the development of sophisticated platform technologies that have long endurance and capable of offering high system capacity. Consequently, the implementation and desperately required proof of the concept are significantly delayed. Furthermore, many studies have covered the exploitation of the strength of aerial platforms but none has comprehensively addressed the challenging properties of such platforms. Therefore, instead of waiting for the maturity of the platform technologies to fit with the mobile communications requirements, in this work airplane (an existing aerial platform) is selected as infrastructure for UMTS. Apart from the maturity of the airplane technology and the ultra-fast deployment features for emergency situations, airplanes also resemble the most challenging features of aerial platforms that are also addressed in this thesis. Severe atmospheric disturbance, high airplane speed, and short endurance are identified as the main features of Airplane UMTS. These features are realistically incorporated into an Airplane UMTS system level simulator, which is developed for the study of the characteristics and performance of the system in terms of Doppler, coverage, interference, coexistence with ground-based system, and airplane handover. The results show that the viability of Airplane UMTS is very encouraging. The Doppler rates are less than the ones of the benchmark system, ground-based UMTS, although the Doppler shifts are higher due to the mobility of the airplane. The airplane attitude does not have significant effects to the system coverage but it does affect the handover performance particularly for a system with fixed mounted multibeams antenna. The overall interference in the system is also affected by the airplane mobility, but it is still better than the ground-based system. Airplane UMTS can also coexist very well with the ground-based UMTS as a neighbouring or even as an overlay system. The short endurance problem can be overcome by the implementation of the proposed smooth airplane handover technique.