While speech services in mobile communication systems are investigated quite well, video telephony services are relatively novel in this sector. Because of the market penetration of camera equipped mobile phones the video telephony service is expected to become a widely used service. In this article an introduction of the protocols used for video telephony in UMTS is given. Concepts for the performance evaluation in terms of video (PEVQ) and audio quality (PESQ) are presented and utilized. Evaluations are performed by both live measurements and network emulation. The results show that there is quite potential for improvements related to video telephony in UMTS in terms of video quality and channel setup time. Finally, an improved radio bearer configuration is provided which aims at a better integration of video telephony services into the UMTS architecture.

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The High Speed Downlink Packet Access (HSDPA) is one of the newest extensions to the Universal Mobile Telecommunications System (UMTS). HSDPA allows for higher data rates due to new Adaptive Modulation and Coding (AMC) techniques, a Hybrid Automatic Repeat Request (H-ARQ) protocol and a fast scheduling algorithm. The fast scheduling, taking into account the current channel conditions of each user, contributes significantly to the performance of HSDPA by the so called multiuser diversity gain.Within the scope of this paper several scheduling algorithms are introduced and are analyzed with respect to both, the overall system performance and the individual user Quality of Service (QoS) constraints. Results illustrate the trade-off between the conflicting targets of high cell throughput and the delay requirements for real-time services.

The goal of Universal Mobile Telecommunications System (UMTS) is the delivery of multimedia services to the mobile user. Each different service requires its specific Quality ofService (QoS) to satisfy the mobile user. In this paper, a scheduling concept for the Medium Access Control is presented that satisfies the QoS requirements. To validate the scheduling concept a typical mobile user application mix is examined for performance analysis by simulations. A UMTS Radio Inferface Simulafor (URIS) is used that is based on an emulation of the standardized UMTS protocol stack extended by the Transmission Confml Protocol (TCP) and the Internet Protocol (IP). Simulation results of QoS parameters like delay and throughput depict the performance of mobile applications over UMTS.

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