The European Telecommunications Standards Institute (ETST) is currently specifying the standard for Satellite UMTS (S-UMTS) as a significant complementary component enabling Universal Mobile Telecommunication System (UMTS) to provide world-wide multimedia wireless Services in environments encompassing indoor Pico cells to satellite mega cells. Due to the interworking requirement between terrestrial and satellite component, the main focus of the standardization can be categorized in twofold: system level regarding integration issue and protocol level regarding compatibility issue between both radio components. This thesis analyzes possible integration scenarios of the satellite component into UMTS in terms of their impacts on the overall system performance. A meaningful integration scenario is selected among them and subsequently, in order to indicate feasibility of the selected integration scenario, a Mobility Management (MM) protocol named Inter-Segment Roaming (TSR) is proposed to enable seamless roaming between terrestrial and satellite radio segments. For investigating the impact of integration of the satellite component into the system, the on-board processing facility of the satellite is taken as the most significant factor on the overall system performance. Furthermore, applicability of UMTS protocol to S-UMTS is investigated, whereby the investigation is performed from Medium Access Control (MAC) to Radio Resource Control (RRC) layer in Access Network (AN). Taking the long propagation delay characterized by the satellite component as the main investigation metric, its impacts on performance as well as functionality of each layer protocol are investigated. Subsequently, proposals to overcome the negative impacts of the long propagation delay on the system performance are represented. For the MAC protocol in S-UMTS, an innovative medium access strategy named Fast Uplink Signalling Channel (FAUSCH) is proposed as a complementary solution to the Random Access Channel (RACH) to avoid the long access delay in RACH operation den to collision. The performance of the FAUSCH operation in S-UMTS is evaluated in terms of analytical as well as simulative model under several radio propagation conditions represented by the satellite component. Further, the performance of the error correction mechanism with retransmission for the Radio Link Control (RLC) layer in S-UMTS is analyzed. Due to the long round trip delay of the satellite component, Selective Repeat -ARQ (SR-ARQ) is selected as the most appropriate ARQ protocol type for the RLC Acknowledged Mode (AM). In this thesis, the performance of the SR-ARQ protocol is investigated by analyzing mathematical model as well as through simulation. Thereby, the on-board processing of satellite is brought in relation with the selected ARQ type and comparative investigations with the bent-pipe type of satellite are performed indicating a huge advantage of on-board processing. Regarding the RRC layer in S-UMTS, the protocol for supporting the Non Access Stratum (NAS) functionality is specified, whereby a novel SIPRAN concept is proposed that enhances parameters of NAS message into a Session Initiation Protocol (SIP) message. It is proved that the proposed SIPRA 1 concept accomplishes a much shorter duration for the Session setup procedure than the conventional NAS and SIP signalling method. The performances of the topical Internet traffics i.e. Voice over IP (VoIP), Web browsing and file transfer in S-UMTS arc analyzed by means of stochastic event driven en simulation. Thereby, two types of simulators i.e. link level and protocol level simulators are used for focusing on all impacts of the system parameters like interference, channel condition and layer protocol configuration into account.