cordingly. The target of the purpose, although other receiver structures are also power control is to ensure that the received SIR of the possible. However, if the cells belong to different DPCCH is at an appropriate level for each user. Note NodeBs, combining cannot take place in the RAKE re- that the required SIR depends on the data rate. This SIR ceiver. Instead, each NodeB tries to decode the received target may very well be different for different users. If signal and forwards correctly received data units to the the SIR is below the target, that is too low for proper RNC. As long as at least one NodeB received the data demodulation, the NodeB commands the UE to increase correctly, the transmission is successful and the RNC can its transmission power. Similarly, if the received SIR is discard any duplicates in the case multiple NodeBs cor- above the target and unnecessarily high, the UE is rectly received the transmission and only forward one instructed to lower its transmission power. If power copy of each correctly received data unit 1 Missing data control would not be present, the inter-user interference units, in case none of the NodeBs received a correct copy could cause the transmissions from some users to be non- of the data unit, can be detected by the RLC protocol and decodable. This is often referred to as the near-far a retransmission can be requested. Soft handover is one problem - transmissions from users near the base station of the main reasons why the RLC is located in the RNC will be received at a significantly higher power level than and not in the NodeB. transmissions from users far from the base station, In addition to reception at multiple cells, uplink soft making demodulation of far users impossible unless handover also implies power control from multiple cells. (closed-loop) power control is used. As it is sufficient if the transmission is received in one Fast closed-loop power control is used in the downlink cell, the UE lowers its transmission power if the power as well, although no