Uplink Power Control And TFCS Selection In WCDMA

Mobile communication is one of the most repaid develop fileds in the filed ofcommunication.Until now, mobile communication has gone through first generationmobile communication , second mobile communication and will enter third generationmobile communication. The third generation mobile communication can combinemultimedia communication with voice communication, in addition,3G may providemany service such as picture,music,web browse,video meeting and so on.The thirdgengration mobile communication means standards which is appropriate for all thecountry in the word,new service,much bigger range much more frequency resources.Inthird gengration mobile communication system,every one can have his own numberand estabilish his connection which is required for his business across many networks.In third generation mobile communication,how to manage limited resources is avery important issue.The providers of the service want to use a high capabilitysystem,thus,they can gain more income by providing service to more users；In the otherside,the users want to be provided good quality communication,however,more andmore users coming in the system increase the interference to each other,as a result, aseries of issues such as quality going down or long time waiting happen.Power is a limited resource in third generation mobile communication systemsdue the existence of a theoretical maximum-capacity point that arises as a result ofimperfect interference cancellation in the receiver. The channel decoder sees residualinterference as an increase in noise power and hence detection is impaired due to areduction in signal-to-interference ratio (SIR). In order to improve the SIR for thatuser, the solution is to increase his transmit power (S). However, this also increases (I)for all other users and hence they must increase their transmit powers accordingly.The result is that the power entering the system spirals as more users are admitted,andaccordingly the capability of the system is limited.Within UTRA the selection of TFCScontrol the error correction scheme,therefore appropriate selection of TFCS is coupledwith power control scheme.The overall power control scheme should attempt to ensure that this performancegoal is met, but not exceeded. To achieve this, power control schemes are usually splitinto two functions；a so-called'inner-loop'that attempts to maintain a consistent targetsignal to interference ratio at the receiver, and a so-called'outer-loop'that attempts tomaintain the specified consistent error rate through appropriate setting of the inner-loopSIR target.The uplink inner-loop power control process run in the UE,the whole process isbelow(in PUSCH state):1. UE demodulat the BCCH of the cell and has knowledge of the followingparameters as a result: PCCPCH Reference Power (Pref), ISCP (for each UL timeslot),USCH constant parameter (KUSCH).2. The process has also been gathering measurements of RSCP on timeslot 0,OVSF code 1 (RSCPTS0), and has produced a filtered value of these measurementsRSCPFILT. RSCPFILT is derived from a filtering process which is performed in the lineardomain. The value of RSCPFILT is then derived by converting this linear filtered valueinto the log domain.3. Caculate the power of the UE.The uplink outer-loop power control process run in the RNC, The function of theUL outer loop is to maintain a constant UL BLER in line with the BLER target value forthe packet service to the UE as configured by the element manager. Sawtooth algorithmis a outer loop power control algorithm in common use,we improve this algorithm byset some threshold.Commonly a decision on whether to adjust the SIRTarget signalled in the nextPSCHAM message is made based on:1. The counter value C in relation to a predetermined counter thresholdMAC_PDU_LIMIT.2. The current value of OLT.3. The time since the last SIRTarget update, as regulated by threshold Pms.In order to provide a quicker response time for cases in which the current estimatedBLER is unacceptably high,in the following condication also notify the UE adjust theSIRTarget signalled in the next PSCHAM message:1. The BLER observed over this period is greater than 3 times the BLER target.2. The time since the last update is greater than Pms.The gengral concept of the uplink TFCS selection algorithm is that a modifiedform of UE uplink power control algorithm. The algorithm operates as follows:1. UE reports P-CCPCH RSCP and ISCP in PUSCH CAPACITY REQUESTmessage.2. RRM determines UE-Node B pathloss from P-CCPCH RSCP and P-CCPCHreference power.3. Node B reports timeslot ISCP.4. RRM determines maximum achievable SIR at Node B for this UE usingdetermined pathloss, node B ISCP and maximum allowed UE TX power.5. A provisional TFCS decision is made6. We need to perform a check to stop excessive interference from occurring intoneighbouring cells which will occur if a high TFCS is selected .7. The TFCS decision is signalled to UE for subsequent allocations of PUSCH ina PSHCAM message.In the end,the uplink power control algorithm and TFCS selection algorithm istested on a realWCDMAsystem.The algorithm run well,can meet the users'requirement on QoS.