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Figure 10Uplink processing function blocks.• recovers the uplink control channel dataand DPDCH data;• generates uplink TPC (UL-TPC) commands;• detects downlink TPC (DL-TPC) commands;and• decodes and de-maps the TFCI.SearcherIn multipath propagation environments,the RAKE receiver must know when themultipath rays arrive—that is, it must determinethe position of the multipath raysalong the delay axis, so that it can allocatethe RAKE fingers to positions where themultipath components hit with signalpower. The task of the searcher in the basebandis to synchronize the RAKE fingers.To speed up the searching process, a narrowsearcher window is placed where themultipath rays are expected. However, insome cases, such as soft-handover set-up, thepropagation delay is unknown; therefore, awide searcher window is needed that correspondsto the entire cell range. The searcheralso estimates the profiles of radio channeldelay and sends them to the RAKE receiver.RAKE receiverThe RAKE receiver separates the multipathcomponents and combines them coherentlyinto a large signal vector that provides gooddemodulation conditions. This increases theprobability of making correct decisions andimproves receiver performance.Given the proper spreading code, theRAKE receiver can de-spread all detectedmultipath rays. Using the pilot bits to estimatechannel amplitude, phase, frequencyoffset and Doppler spread, the RAKE receiverprocesses the multipath rays with thecorresponding weighting, and combinesthe rays. Before combining the rays, however,each ray is processed by one RAKEfinger.To make efficient use of the hardware resources,the RAKE fingers can be treated as apool of hardware resources. They can also beflexibly allocated between users on the sameRAX. This allocation is made according tothe position information delivered by thesearcher. Fewer RAKE fingers are needed inrural settings with a line-of-sight connectionbetween UEs and the radio base station thanin urban settings with multipath fading.During softer handover, which is thehandover between cells in the same RBS andon the same carrier, the detected signals arecombined.The DPCH signals are demultiplexed andde-mapped to the DCH of the transportchannel for the next step of processing in thedecoder. The decoder input signal consistsof interleaved soft bits from the demodulator.The following tasks are performed in thedecoder block:Ericsson Review No. 1, 2003 39