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Figure 9TX board of the RBS3000 series.and chip-rate processing parts with respectto the control of measurements, set-up, release,and reconfiguration of cell-carriersand channels.The functionality of the lub user-plane interfacehandler and the physical layer processingcontroller is implemented in DSPsto give flexible implementation of• the controller functions;• external interfaces to the RNC for the userdata interface; and• interfaces to the board processor for thecontrol interface.The symbol-rate processing functionality isimplemented in FPGAs due to processingdelay and varying requirements put on thethroughput of user data. Some flexibility isalso provided in view of changing requirementsfor the implemented functionality.The chip-rate processing functionality isimplemented in ASICs. This approach employsparallel processing to meet the demandfor limited processing delay. It alsoallows synchronous transmission of the distributedoutput sequence to the TRX.Figure 9 shows a TX board used in anRBS3000. The board can handle multiplecell-carriers with more than one antennabranch.Interlace between the TX and RAX boardsThe interface between the TX and RAXboards supports fast signaling for controllingcall set-up and power. When the user equipment(UE) sets up a call to the RBS, the correspondingRAX board in the RBS reservessufficient resources. The RAX board thensends a layer-1 acknowledgement signal viathe TX board to the UE, indicating that theUE may send the RACH message part. Tocontrol power in the downlink, the RAXboard detects the TPC commands and sendsthem to the TX board, which adjusts downlinktransmission power.To control power in the uplink, the RAXboard compares the signal-to-interferenceratio (SIR) target with the SIR of the receivedsignals and generates the TPC commands,which it sends to the UE in thedownlink DPCCH.Uplink processingboard —RAX boardUplink processing functionsIn the uplink, the signals received from theair interface are input to the baseband in adigital signal format from the TRX radiopart of the RBS (Figure 10). For the dedicatedphysical channel (DPCH), the incomingsignals from the TRX are processed inthe demodulator function block, which containsa searcher and RAKE receiver. The demodulator• performs de-spreading;38Ericsson Review No. 1, 2003
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
Page 1 and 2: Ericsson 1/2003REVIEWTHE TELECOMMUN
Page 3 and 4: EricssonREVIEWTHE TELECOMMUNICATION
Page 5 and 6: systems built from Ericsson's produ
Page 7: EditorialEric PetersonSince joining
Page 10 and 11: Figure 3Interoperability of mobile
Page 12 and 13: Figure 7Handover from GSM to WCDMA.
Page 14 and 15: OMA—Changing the mobile standards
Page 16 and 17: Figure 3The OMA enables wireless co
Page 18 and 19: instance, the WAP Forum created mob
Page 20 and 21: The service network framework—An
Page 22 and 23: Figure 3Architectural views of the
Page 24 and 25: Figure 7SNF system type view.Sysfem
Page 26 and 27: Figure 9High-availability deploymen
Page 28 and 29: Realizing the operator's service ne
Page 30 and 31: Figure 3Consultative approach to me
Page 32 and 33: Figure 4MMS integration interfaces.
Page 34 and 35: Advanced baseband technology in thi
Page 36 and 37: channels. A channel element is defi
Page 38 and 39: Figure 6Backward hardware compatibi
Page 42 and 43: Figure 11RAX board implementation.
Page 44: Previous issuesNo. 3, 2002Packet da

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