During the past few years, a worldwide interest and unanimous consensus has arisen on personal communication services (PCS), where satellites can play a crucial role in a global scenario for the provision of PCS's all over the world. While for maritime and aeronautical communication services, the mature technologies of geostationary earth orbit (GEO) satellite systems seem the most suitable for present and future enhanced systems, other orbital configuration such as low earth orbit (LEO) and medium earth orbit (MEO) are being considered for the provision of satellite personal communication services to hand-held mobile terminals. One of the main objectives of personal communication services is the capability to provide personal (or continuous) mobility, communication anytime, anywhere. In general, satellite systems can provide a limited capacity with respect to terrestrial networks, nevertheless they are particularly suited in order to cover large terrestrial areas offering a scarce amount of traffic. The problem of radio frequency management for mobile applications has been addressed by World Administrative Radio Conference (WARC-92). One of the most relevant decisions taken at WARC-92 was to allocate the radio determination satellite system (RDSS) 1610-1626.5 MHz (L-Band) and 2483.5-2500 MHz (S-Band) slots to LEO satellite services on a worldwide, primary basis. This enables "big LEO's" to have a reasonable amount of spectram (i.e. capacity) to serve a substantial number of subscribers. However, the available amount of spectrum at L-band and S-band out of WARC-92 appears hardly sufficient to permit several systems to operate. Hence, to enable all the systems to operate and fulfil the capacity demand, S-PCNs need to share the limited available frequency spectrum. In this thesis we have proposed and evaluated a new fully overlapped band sharing scheme for mobile satellite systems operating in a land mobile satellite channel environment. The results show that the mobile satellite systems can share the limited available bandwidth. However, the overall system capacity of the MSS has been reduced due to excess intersystem interference. In order to reduce the excess inter-system interference a new enhanced overlapped band sharing protocol is proposed. The performance of this optimised band sharing scheme outperforms the conventional band segmentation scheme. Thus, achieving superior overall system capacity.

Yes / The potentially broad application area in engineering design using Genetic Algorithm (GA) has been widely adopted by many researchers due to its high consistency and accuracy. Presented here is the initial design of a wideband non-dispersive wire bow-tie antenna using GA for breast cancer detection applications. The ultimate goal of this design is to achieve minimal late-time ringing but at higher frequencies such as that located from 4 to 8 GHz, in which is desire to penetrate human tissue for near field imaging. Resistively loading method to reduce minimal ringing caused by the antenna internal reflections is implemented and discussed when the antenna is located in free space and surrounded by lossy medium. Results with optimised antenna geometry and different number of resistive loads are presented and compared with and without existence of scatterers.