itted on the known as the Common Pilot Channel (CPICH). The DPDCH. This information is required by the physical CPICH contains known data and is used as a reference layer in the NodeB for proper demodulation. for downlink channel estimation by all UEs in the cell. User-specific scrambling is used in the WCDMA There is also a pre-allocated control channel carrying cell- uplink and the channelization codes are only used to specific control information. separate different physical channels from the same ter- Since physical channels are separated by OVSF codes, minal. The same set of channelization codes can there- transmissions on different physical channels are orthog- fore be used by multiple UEs. As the transmissions from onal and will not interfere with each other. The different terminals are not time synchronized, separation WCDMA downlink is therefore often said to be ortho- of different terminals by the use of OVSF codes is not gonal. However, at the receiver side, orthogonality will possible. Hence, the uplink is said to be non-orthogonal partly be lost in case of a frequency-selective channel. and different users' transmissions will interfere with each This will cause signal corruption to the received signal other. and result in interference between different codes used The fact that the uplink is non-orthogonal implies that for downlink transmission. Such signal corruption can be fast closed-loop power control is an essential feature of counteracted by an equalizer. WCDMA. With fast closed-loop power control, the +1+1-1-1 +1-1+1- +1+1+1+1 +1-1-1+1 SF=16 SF=32 SF=64 SF=128 SF=256 Figure 4.6-5 Channelization codes. CHAPTER 4.6 WCDMA evolution: HSPA and MBMS NodeB measures the received signal-to-interference ratio uplink transmission are located in the same NodeB, (SIR) on the DPCCH received from each terminal and combining of the received signals occurs in the physical- commands the terminals 1500 times per second to adjust layer receiver. Typically, a RAKE receiver is used for this its transmission power ac