Mixed traffic in UNITS downlink

The traffic being transferred within 3G mobile networks will be composed by different information flows with various constraints on the required QoS (bit rate, delays, etc.). In this scenario, flexibility will be a key point for the success of 3G systems. UNITS (Universal Mobile Telecommunication System) offers both circuit switched and packet switched transfer mode, and within each transfer mode;, different QoS can be achieved by properly setting physical parameters such as the spreading factor of the physical channels, the power control scheme; the rate of the FEC protecting code, etc. In this letter, we,give an evaluation of the downlink performance of W-CDMA UNITS radio interface when providing access to multimedia services. In particular, we analyze through simulations a typical scenario where voice calls and Web-browsing sessions share the same frequency carrier, the former using the dedicated channels (DCH), the latter being transferred on the downlink shared channel (DSCH).