| Vol. 1, No. 1, February 2004 - Art. 4 |
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| Performance Evaluation of UMTS Packet Services |
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by
Flaminio Borgonovo, Antonio Capone, Matteo Cesana, Luigi Fratta (Politecnico di Milano, Italy)
Copyright
© Politecnico di Milano, 2003 |
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Abstract
The provision of efficient high speed packet data services is probably the most important challenge for third generation systems (3G) The efficiency of such services mainly depends on the radio interface. The UMTS W-CDMA radio interface is characterized by great flexibility and a variety of different physical and logical channel types: for example, on the downlink, the Dedicated Channels (DCH) offer circuit switching, and the Downlink Shared Channel(DSCH) and Forward Access Channel (FACH) use packet switching, the former with closed loop power control. Furthermore, the choice of suitable parameters, such as spreading factors, code rates and ARQ schemes make possible several user rate and protection options. In this paper, we evaluate the performance of UMTS packet data services over dedicated channels and shared channels through detailed simulations. In particular, we study the effect of several parameters (spreading factor, code rate, channel set-up delay, etc.) on the system capacity by means of the delay-throughput curves and show that the setting of parameters may be critical with respect to system performance and stability. Finally, in order to improve the quality of the offered packet service, we propose a simple but effective flow control mechanism which is able to limit the interference on the shared resource. |
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