ably improved support for the downlink packet data transfer and enable the provision of various types of multimedia services [3GP01a]. A key characteristic of HSDPA is the use of Shared-Channel Transmission, which implies that a certain fraction of the total downlink radio resources, channel codes and transmission power belong to the common resource that is dynamically shared between users, primarily in the time domain. The use of shared-channel transmission in WCDMA is implemented through a new transport channel: High-Speed Downlink Shared Channel (HS-DSCH) that is shared by all HSDPA UEs within the cell. The HS-DSCH enables the possibility to rapidly allocate a large fraction of the downlink resources for transmission of data to a specific user. This is appropriate for packet data applications which in nature have bursty characteristics and thus rapidly varying resource requirements. The HS-DSCH excludes two basic features of WCDMA radio channels: variable spreading factor and fast power control. Instead, it introduces the following new features [HT06, DPSB07], which deliver the improved downlink performance in terms of higher peak data rate, lower latency and increased capacity. 1) Short Transmission Time Interval (TTI) of 2 ms. The use of such a short TTI for HSDPA reduces the overall delay and improves the tracking of fast channel variations exploited by the rate control and the channel dependent scheduling. 2) Adaptive Modulation and Coding (AMC): HSDPA is not power controlled instead it dynamically adjusts the modulation scheme between QPSK and 16QAM. The modulation scheme and coding is changed on a per user basis depending on signal quality and cell usage; and selected independently for each 2 ms TTI (Transmission Time Interval) by the Node B and can therefore track rapid channel variations. 3) Fast packet scheduling at the base station (Node B): by shifting the packet scheduler from the RNC in Rel99 to the Node B enables a more efficient implementation of the scheduling by allowing the scheduler to work 