UMTS Optimization.pdf

167
UMTS Optimization

description

UMTS optimization

Transcript of UMTS Optimization.pdf

  • UMTS Optimization

  • WCDMA Features Idle Mode Behavior (Air interface review) Power control Handover Capacity management Channel switching 3G KPIs Monitoring and analysis HSDPA CQI

    Course Content

  • WCDMA Radio Network Features

  • Idle Mode Behavior

    PLMN selectionAir interface Review Cell Selection / Reselection Paging Location Update and Routing area update System Information

  • UE in IDLE MODE has the following properties : UE is Powered ON , while it doesn't have connection to the Radio Network UE is synchronized with Radio Network and can read broadcast information , Accordingly UE can access the Network. UE is registered on the network , updating Network with its LAC , Accordingly reachableWhat is Idle Mode?

  • Normal Service When the UE select accepted level cell in its HPLMN Limited ServiceUE didnt find any accepted level cells at its HPLMN it selects any accepted level cell at any other PLMN Operator reserved servicesOperator can reserve any cell for testing only and this through two parameters cell reserved and Access classNbarredServices Types in Idle Mode

  • PLMN SelectionPLMN SelectionWhat is it ? And When it happens ? What are the types of PLMN selection?

    PLMN Selection is the process in which the UE decide which PLMN it should register in

    Happens when the Mobile turned on or when the mobile returned back from limiting service

    Automatic PLMN selection Manual PLMN selection

  • Automatic PLMN selectionWhen the mobile powered on The mobile uses information about the last registered PLMN (Freq) Mobile search the strongest signal cells and read its system information to get (MCC and MNC) If the chosen cell is accepted the mobile try to do the registration If the last chosen PLMN not available or there is no stored info in the mobile USIM then the mobile might select any accepted PLMN

  • In the automatic selection if no last register PLMN exists or available the Mobile will select the PLMN that is available as follow HPLMN Each PLMN in User controlled PLMNs list in the USIM, in order of priority Each PLMN in operator controlled PLMN list in the USIM, in order of priority Other PLMNs according to the high quality criteria randomly the minimum CPICH RSCP power is 95dBm Other PLMNs that dont fulfill high quality criteriaAutomatic PLMN selection

  • Initial Cell Selection Automatic Mode

  • Manual PLMN Selection UE displays all the available PLMNS after carriers scanning All the available PLMNs will appear regardless it is allowed or not

  • RoamingUE will be able to obtain services from another PLMN Same country (national roaming) Another country (international roaming) Every 30 minutes the UE try to reselect its home PLMN

  • Air Interface

  • TDMA TRANSMITTERDataMultiplexer

  • Channelizationcode 1Channelizationcode 2Channelizationcode 3Channelizationcode NScramblingCodeScramblingCodeScramblingCodeScramblingCodeWCDMA TRANSMITTER

  • In all radio systems the air interface will add noise to the signal This will produce a distortion in the received signal.

    Analog Cellular

    Digital Cellular

    In the case of an analogue cellular system the human ear perform error correction of this received signal and noise.

    However in digital systems we do not have this case, This noise will result in bit errors, logic 1 could be interpreted as a logic 0logic 0 could be interpreted as a logic 1.

    All digital systems must have some method of overcoming these errors.

  • CRC for Error Detection

  • CRC Cyclic Redundancy CheckCyclic Redundancy Check (CRC) coding is used in error detection.

    CRC is used to calculate Block Error Ratio (BLER).

    Transmitter ReceiverIF mismatching in check sum The is an error

  • Error Correction

  • 1-Send the information a number of times

    Receiver could select which message is most correct by a best out of three decision. The more times the data is transmitted the better is the error protection. However the bandwidth is also increased proportionallyThere are two basic types of FEC available, block or continuous codesBlock Codes (Hamming Codes, BCH Codes, Reed-Solomon Codes)

    Continuous Codes (Convolutional Codes, Turbo Codes)

  • LOGICAL CHANNELS

  • 1-LOGICAL CHANNELS

    Logical channel types are classified into two groups: Control channels for the transfer of control information Traffic channels for the transfer of user information.Broadcast Control Channel (BCCH) Downlink channel for broadcasting system information.

    Paging Control Channel (PCCH) Downlink channel that transfers paging information and is used when the UE is in idle mode.

    Common Control Channel (CCCH) Used by the UE needs to access the network.

    Dedicated Control Channel (DCCH) Point-to-point bi-directional channel that transmits dedicated control information between UE and the network.

    Dedicated Traffic Channel (DTCH) Point-to-point channel, dedicated to one UE, for transferring userinformation. A DTCH can exist in the uplink and downlink.

  • Transport CHANNELS

  • Dedicated Transport Channel (DCH)The dedicated transport channel carries all the information intended for the given userService data, such as speech framesHigher layer control information, such as handover commands or measurement reports from the terminal. Common Transport ChannelsBroadcast ChannelForward Access ChannelPaging ChannelRACHDSCH2-Transport CHANNELS

  • 2-Transport CHANNELS (Contd)

    Broadcast Channel (BCH)Continuous transmission of system and cell information

    Forward Access Channel (FACH)Control signaling during call setupPacket data transmission in low rates

    Paging Channel (PCH)

    When the network wants to initiate communication with the terminal.

    RACHThe RACH is an uplink transport channel used to make requests to set up a connection

    DSCHThe DSCH is always associated with a downlink DCH.

  • Physical CHANNELSCommon Physical ChannelsDedicated Physical ChannelsDownlink Indication Channels

  • Common Physical Channels

    P-CCPCH Primary Common Control Physical Channel (DL)-Broadcasts cell information

    SCH Synchronization Channel (DL)- Fast Synch.

    S-CCPCH Secondary Common Control Physical Channel (DL)-Carries both the Paging Channel (PCH) and the Forward Access Channel (FACH).

    P-CPICH Primary Common Pilot Channel (DL). Aids channel estimation (handover and cell selection).

    Physical Random Access Channel (PRACH) ULThis channel is used to carry access requests

  • Dedicated Physical Channels

    DPDCH Dedicated Physical Data Channel (DL/UL)-Transmits user dedicated data to RBS-Used for sending dedicated data

    DPCCH Dedicated Physical Control Channel (DL/UL)-Signaling and control to UEsTransmit Power Control (TPC) bits

    Downlink Indication Channels

    AICH Acquisition Indication Channel-Acknowledges that RBS has acquired a UE Random Access attempt

    PICH Page Indication ChannelInforms a UE if it should monitor the Paging Channel

  • Layers generate channel typesLayer 3RRCControl PlaneLayer 2RLCMACUser Plan (User data)SRBLogical ChannelsLogical ChannelsTransport ChannelsRBLayer 1Physical LayerUu interface

  • Mapping of Transport Channels onto the Physical Channels

    The different transport channels are mapped to different physical channels.

    There exist physical channels to carry only information relevant to physical layer procedures.Synchronization Channel (SCH)Common Pilot Channel (CPICH)Acquisition Indication Channel (AICH)[Are not directly visible to higher layers]

    A DCH is mapped onto two physical channels. The Dedicated Physical Data Channel (DPDCH)Dedicated Physical Control Channel (DPCCH)

  • Physical Channel Layer Structure

    A physical channel consists of a three-layer structure Super frames, radio frames, and time slots.

    Super frame A Super frame has duration of 720ms and consists of 72 radio frames. The super frame boundaries are defined by the System Frame Number (SFN)Radio frame A Radio frame is a processing unit of 10ms length, which consists of 15 time slots.Time slot A Time slot is a unit that consists of 2560 chips that represent the information symbols. The number of symbols per time slot depends on the physical channel.

  • Primary Common Control Physical Channel (PCCPCH)Broadcast Channel (BCH)Transport ChannelPhysical ChannelRBSChannel mappingSecondary Common Control Physical Channel (SCCPCH)Physical Downlink Shared Channel (PDSCH)Forward Access Channel (FACH)Paging Channel (PCH)RACHDSCHDCHUEDedicated Physical Control Channel (DPCCH)Physical Common Packet Channel (PCPCH)

    Dedicated Physical Data Channel (DPDCH)Logical ChannelPhysical Random Access Channel (PRACH)

  • Frame Structure of the Dedicated Physical Channels (DPCCH)DPCCHDPDCHFrame 1Frame 2Radio Frame720 msSlot 0Slot 14

    Radio Frame10 ms

  • Cell selection

  • Cell selection procedure Squal = Qqualmeas qQualMin (For WCDMA)

    Qqualmeas is CPICH Ec/No qQualMin is minimum required Ec/No

    Srxlev = Qrxlevmeas qRxlevMin (for all cells)

    Qrxlevmeas is CPICH RSCP qRxlevMin is minimum required RSCP The cell consider as accepted if

    Squal > 0 and Srxlev > 0

  • Cell selection occurs when

    When UE is switched on When UE in idle mode has had a number of failed RRC connection request When a UE returns to idle mode from the connection mode on common channel (cellFACH) UE returns to idle mode from connected mode (cellDCH) When a UE returns to idle mode after an emergency call on any PLMNCell selection procedure(Contd)

  • Cell Re-selection

  • Cell reselection procedure When it occurs When cell on which it is camping is no longer suitable When there is any neighbor with better quality than the selected one When the UE in the limited service state on an acceptable cell When the UE is in cell _FACH state3G F13G F2GSM3G F1

  • 1- Intra frequency measurements starts when

    Squal

  • Cell reselection procedure(Contd)3. GSM measurements starts when

    Squal

  • GSM measurementTimeQqualmin-18-14Qqualmeas

    SRAT Search=4dBCell reselection procedure(Contd)

  • GSM measurementTimeQrxlevmin-115-112QRxlevmeas

    SHcsSearch=3dBCell reselection procedure(Contd)

  • When the UE triggers a cell reselections procedure it starts ranking for the cell satisfyScriteria (Squal > 0 and Srxlev > 0) and the ranking will be according Rcriteria

    R(serving)= Qmeas(s)+qHyst(s) R(neighbor)= Qmeas(n)qOffset(s,n)Cell reselection procedure(Contd) Qmeas: is the quality value of the received signal which is derived fromCPICH Ec/No orCPICH RSCP

    qHyst(s): hystersis value sent to mobile in system information used to delay the reselection qHyst1 if the ranking based on CPICH RSCPqHyst2 if the ranking based on CPICH Ec/No

  • qOffset(s,n): is the offset between the serving and the neighbor cell also used to shift the cell boarder qOffset1sn : if the ranking based on RSCP. qOffset2sn : if the ranking based on Ec/No

    qualMeasQuantity is the parameter that determine if we will do the ranking based on RSCP or Ec/No

    The UE reslect the better cell if it stay better for time interval more than TreselectionCell reselection procedure(Contd)

  • TimeQmeas

    R(S)Cell reselection procedure(Contd)qHyst2=4R(n)Qmeas(S)Qmeas(n)qOffset2SN=oTreSelectionCell Re-Selection to NeigR(n) >R(S)UMTS to UMTS cell

  • TimeQmeas

    R(S)qHyst1=4Qmeas(n) (GSM)qrxlevmin+SHcsSearchQmeas(S)QrxlevminR(N)qoffset1SNTreSelectionUMTS to GSM cell ReselectionCell reselection procedure(Contd)

  • Location Update and Routing area update If the LAI or RAI read on system information has been changed then the UE tries to do RAor LA registration Update During the idle mode when the UE changes its location or routing area it should do LAU or RAU LAU and RAU managed by CN11-The UE reads from system information that the LAI is not the same as that stored in the USIM. This triggers the UE to update the location area.

    2-The UE tries to access the network and sends a request message to the RNC, via the RBSThe RNC checks if it is possible to allocate a dedicated channel to the UE.

    3- Resources in the RBS and over the Iub interface are reserved by the RNC and are ACK by the RBS

    4. Information about the new channel is sent to the UE with a setup message.

    5. Synchronization is achieved between the UE and the RBS, and the UE sends a complete message.

    22345Example :LOCATION UPDATING

  • 12234566-The UE sends the request to update the location information to the CN.This message also carries the IMSI and old LAI. Iu signaling bearer is set up between the RNC and the CN. There is now a signaling connection between the UE and the CN. As this is the first time the UE accesses this service area the subscriber is unknown in the VLR.

    7-The VLR sends a request to the subscribers HLR for Authentication Information.

    8- The HLR sends this information to the VLR.

    9-MSC/VLR starts to authenticate the subscriber. This message is transparent over WCDMA RAN.

    10-After Authentication, the VLR asks the HLR to update its Location information for the IMSI and with thenew VLR address

    11- VLR receives an acknowledgement from the HLR.

    12-The MSC/VLR transmits an acceptance to the UE, UE updates the location information in the USIM.

    13- The signaling connection is released. First the UE is told to release the connection then the RBS78910111213Location Update and Routing area update(Contd)

  • Types of Updates

    PeriodicOccurs periodically after timer T3212 for LAU or T3312 for RAUThe value of the timer sent to the UE over BCCH in the IMSI attach or in RAUCN parameter.when the UE is in connected mode and the timer expired then the UE wait until enter idle mode again to perform the periodic LA

    NormalOccurs when the UE change its LA or RA, the UE discover the changes after comparing the new Cell RAC or LAC with the stored values in the USIMLocation Update and Routing area update(Contd)

  • IMSI attach and detach

    IMSI attach occurs when the UE activated and the detach occurs when UE deactivated This function used to prevent unnecessary paging for the off UEs IMSI attach is an optional function and it is managed by cell parameter called ATT sent to UE over BCCH If ATT set to 1 it means the UE should do IMSI attach and detach

  • Paging Is the process through it the CN inform the UE there is a service request or RAN inform all theUEs that the System information has been updated

    Paging occurs in the following states Idle URAPCH (SRB) CellFACH (SRB and RAB) CellDCH Paging in Idle mode and URAPCHPICH and SCCPCH are used to page the UEPICH used to tell the UE when to read SCCPCHSCCPCH used to carry RRC message type1 which includes actual paging info and the number of times the WCDMA RAN will retransmit the paging Paging in cellFACH and cellDCHWhen the establish connection between UE and RAN is existing Paging type 2 message are sent to the user it is carried on DCCH so it is only for one user.

  • Power Control

  • NoPowerFreq

  • To achieve the required BLER for each service their must be Eb/No requirements

    WCDMA is based on QPSK modulation technique

  • 1 Carrier (5MHz)PowerEb/No
  • Power control is on Both links:- DL power control ( Capacity issue )UL power control ( Coverage issue )DL power control (Capacity issue)1 Carrier (5MHz)Eb/No > Eb/No RequiredEb/No = Eb/No RequiredPowerPowerInterferenceCapacity

  • Max TX powerEb/No requiredFreq.PowerCell BreathingUL power control (coverage issue)

  • WCDMA power control procedure consists of 3 Loops1- Open-loop2- Inner-loop3- Outer-loop UL Power Control1- Open-loop power control(UL)At beginning of a connection in order to provide initial powerMS estimates an initial minimum required powerIf no response received from Node-B, MS retries with a slightly higher power until acknowledgement received

    PowerPiniAck

  • 2- Inner-Loop Power Control (UL) SIR received is compared to target SIRSIR > Target SIR Node-B send power control commands to MS to decrease its power to reach target SIR< Target SIRNode-B send power control commands to MS to increase its power to reach targetNote: Power control commands reaches up to 1500 command per second able to over come fast fading

  • BLER3- Outer-Loop Power Control(UL)BLER > blerQualityTarget SIR target is increased hence sent power control commands to MS to increase its power so that BLER decreasedBLER < blerQualityTarget SIR target is decreasedhence sent power control commands to MS to decrease its power (able to achieve SIR target with lower power )BLER increase RNCBLERSIR TargetBLER DecreaseMS PowerRNCBLERSIR TargetMS Power

  • 1-Downlink Open Loop Power Control2-Downlink Inner Loop Power ControlUL and DL Inner Loop Power Control aim tomaintain a required SIR target foreach connected UE.3-Downlink Outer loop Power Control

  • CRC=OKCRC=OKCRC=OKCRC=notCRC=OKCRC=OKCRC=OKCRC=OKCRC=OKCRC=notCRC=OKCRC=OKSIR targetSIR targetTimeTimeulSirStepRatioulSirStepulSirStepBLERBLERBLERTwo alternative algorithms for uplink Outer Loop Power control can be implemented.

    Constant Step Regulator algorithmJump Regulator algorithm

  • ParametersulSirStepulSirStep = 10 { 0..50 }Size of up step of SIR target for 10 ms TTI users.Unit: 0.1 dBulSirStepTti2ulSirStepTti2 = 5 { 0..50 }Size of up step of SIR target for 2 ms TTI users.Unit: 0.1 dBsirMaxsirMax = 100 { -82..173 }Maximum allowed SIR target for 10 ms TTI users.Unit: 0.1 dBsirMaxTti2sirMaxTti2 = 173 { -82..173 }Maximum allowed SIR target for 2 ms TTI users.Unit: 0.1 dBsirMinsirMin = -82 { -82..173 }Minimum allowed SIR target.Unit: 0.1 dBulOuterLoopRegulatorThe parameter determines the algorithm to be used in UL Outer loop power control0 CONSTANT_STEP1 JUMP

  • Each node-B in the active set listen to the same sequence of TPC commands from the UE.

    Received TPC commands may be affected by different errors, due to the different radio propagation conditions experienced by each of links.

    Consequently, the transmitted power at different RBSs will start to drift

    Power Balancing prevents this power drift problemTPC CommandTPC CommandPower DriftBS PowerBS Power

  • Downlink Power Balancing is configured to work on an eight frame cycle.At the beginning of the cycle reference power is calculatedReference power = average of all Radio Link (RL) powers Over the next eight frames the power of each RL is adjusted back to this referenceTPC CommandTPC CommandBS PowerRNCP(k) = P(k-1) + Pbal

  • Parameter dlPcMethod defines the selected Power Balancing method.

    dlPcMethodCommentFIXEDBoth Power Balancing and downlink Inner Loop Power Control are disabledNO BALANCINGDownlink Inner Loop Power Control is active, but Power Balancing is never startedBALANCINGPower Balancing is activated and runs in parallel with downlink Inner Loop Power Control when more than one Radio Link Set (RLS) is involved in the connection between the UE and UTRAN. Downlink Inner Loop Power Control is always active. FIXED BALANCINGDownlink Inner Loop Power Control is active as long as one single RLS is involved in the connection between the UE and UTRAN. As soon as an additional RLS enters the active set, downlink Inner Loop Power Control is disabled, and Power Balancing is activated

  • Handover

  • Inter-System HandoverHandover from a CDMA system to an Analog or TDMA systemTraffic and Control Channels are Disconnected and must be Reconnected Hard HandoverWhen the MS must change CDMA carrier frequency during the HandoverTraffic and Control Channels are Disconnected and must be Reconnected Soft HandoverUnique to CDMADuring Handover, the MS has concurrent traffic connections with two BSsHandover should be less noticeable Softer HandoverSimilar to Soft Handover, but between two sectors of the same cellHandover is simplified since sectors have identical timing

  • Missing Neighbour Problem

  • Cell ACell BCell FCell ECell DCell CCell A Cell B A & B must be neighbor cells Cell B Cell C A & B must be neighbor cells Cell C Cell D A & B must be neighbor cells

    Cell D Cell E A & B must be neighbor cells Cell E Cell F A & B must be neighbor cells

    2G Missing Neighbour Problem

  • Cell ACell BCell FCell ECell A Cell B A & B must be neighbor cells Cell B Cell C A & C are not neighborsCell B Cell D B & D are not neighborCell B Cell E A & E must be neighbor cells Cell E Cell F E & F must be neighbor cells

    ABCDEFCell BCell BMissing Neighbor Cells2G Missing Neighbour Problem(Contd)

  • 3G Cell13G Cell 23G All have the same frequency3G Cell 1PowerSignal (Eb/No) < Required Cant Decode Interference (No)Interference Figure at 3G cell 23G Cell 2 User 3G cell 1 user3G Cell 2 UserInterference (No)Signal (Eb/No) = Required Eb/No Can Decode 3G Cell 1Missing Neighbor Cells3G cell 1 user3G Missing Neighbour Problem(Contd)

  • BS[1]BS[2]RNCRNC3G Missing Neighbour Problem(Contd)

  • Network takes advantage of having several simultaneous radio linksUL power of UE can be lowered reducing UL interference and increasing system capacityRNCRNCRNCRNCWhen the UE is in soft handover it receives (possibly different) TPC commands from all cells in its active set.

    All of these commands are combined, yielding a single combined TPC command that tells the UE to increase or decrease the transmit power

  • Without Soft/Softer Handover At the edge of the node-BUE entering a new cell area without being power controlled by the detected cellAt the edge UE would transmit on full power for UL.The UE transmitting on full power would cause UL interference in other node-Bs. Reducing the capacity of other node-Bs.Protection from UEs becoming severe disturbers.In 3GPP UE can report Detected Cells. If the detected cell quality measure exceeds the quality measure of the best cell in the Active Set by the amount of releaseConnOffset dBsConnection will be released in order to avoid the UE staying in that cell area without being power controlled by the Power Control function of that cell.

  • Field Example

  • Soft/Softer Handover

  • Soft HandoverUnique to CDMADuring Handover, the MS has concurrent traffic connections with two BSsHandover should be less noticeable

    Softer HandoverSimilar to Soft Handover, but between two sectors of the same cellHandover is simplified since sectors have identical timingNode-B 1Node-B 2Node-B 1Soft/Softer Handover(Contd)

  • Active Set Cell 2(AS)Active Set Cell (AS) 3Active Set Cell 1 (AS)Monitor NeighborMonitor NeighborDetected NeighborDetected NeighborMissing Neighbor CellsMissing Neighbor CellsSoft/Softer Handover(Contd)

  • Handovers in 3G consists of two partsEvaluation part UEs designed to evaluate and send measurement reports to the system when certain events occur.

    Evaluation part triggers the corresponding handover execution part.Execution part. Triggered by the evaluation results, allocates resources and performs the actual Handover

    SRNCMEASUREMENT CONTROL MESSAGEmeasurement criteria

    Measured cell (X)fulfilled the thresholdEvent TriggeredMEASUREMENT REPORTEvent occurred which cells fulfilled the event criteria

  • Hysteresis and Time to Trigger Concept

    Due to fluctuations we need to limit the amount of event-triggered reports Hysteresis parameter should be considered with reporting event. The value of the hysteresis is given to the UE in the reporting criteria field of the MEASUREMENT CONTROL message that SRNC sends.In general, The condition to trigger the event is that Meas. Signal > or < threshold +or (H/2)Meas. Signal > or < threshold +or (H/2) during a time equal or greater than the corresponding time to trigger.

    SRNCMEASUREMENT CONTROL MESSAGEmeasurement criteria

  • Filtering, Offsetting, and Weighting before ReportingFilteringThe measured values are filtered by the UE before comparing the result values with the event report criteria. .The layer 3 filter formula is as follows:

    Where,Fn Result of current measurement filter. Fn-1 Result of last filter. Mn Current measurement result. a =1/2^(k/2) Filter coefficient calculated based on the filter factor K (FilterCoeff (Intra)).

    OffsettingOffset can be assigned to each cell. Either positive or negative, Offset is added to the measurement quantity before the UE evaluates whether an event has occurred or not. The UE receives the cell offsets for each cell in the MEASUREMENT CONTROL message sent from the SRNC to the UE. WeightingWeighting factor is used to include active set cells other than the best in evaluation criteria for reporting events.

  • MeasurementquantitytimeP_CPICH best cellreportingRange1aHysteresis1b/2Hysteresis1b/2P_CPICH cell 1Hysteresis1a/2Hysteresis1a/2TTT1areportingRange1bTTT1bSeries of events are defined in 3GPP to trigger criteria for Soft/Softer(HO)

    Event 1a (add) When a cell, not included in the Active Set, enters the reporting range.

    Event 1b(delete)When a cell, included in the Active Set, leaves the reporting range,

  • Event 1a condition

    R1a: Refers to the reporting range of Event 1A. H1a: Refers to the reporting hysteresis of Event 1A. MNew: Refers to measurement of the new cell outside the active set. CIONew:Offset of cell outside active set in relation to other cells (CellIndivOffset (utranRelation)). Mi:Refers to the mean measurement value of other cells except the best cell in active set. NA:Refers to the number of other cells except the best cell in active set. MBest:Refers to the measurement of the best cell in the active set. W:Weight proportion of the best cell to the rest cells in the active set in evaluation standards.

  • Event 1b condition

    R1b: Refers to the reporting range of Event 1B. H1b :Refers to the reporting hysteresis of Event 1B. MOld: Refers to measurement of cell in the active set. CIOOld: Refers to offset of cell in active set in relation to other cells (CellIndivOffset (utranCell)). Mi: Refers to the mean measurement value of other cells except the best cell in active set. NA: Refers to the number of other cells except the best cell in active set. MBest: Refers to the measurement of the best cell in the active set. W: Refers to the weight proportion of the best cell to the rest cells in the active set in evaluation standards.

  • MeasurementquantitytimeAS Cell 1AS Cell 2AS Cell 3Hysteresis1c/2Hysteresis1c/2Cell 4TTT1CEvent 1c

    When a cell, not included in the Active set, becomes stronger than the weakest cell in the Active set, The UE sends an event 1c report to the RNC. If the reported cell is :Valid neighbor Active Set is full Reported cell is proposed as a replacement for the weakest cell in the Active set.

  • Event 1C conditionH1c Refers to the reporting hysteresis of Event 1C. MNew: Refers to measurement of cell outside the active set. MInAS: Refers to the cell with poorest quality in the active set. CIONew: Refers to offset of cell outside the AS in relation to other cells (CellIndivOffset (utranRelation). CIOInAS: Refers to offset of cell with poorest quality in AS in relation to other cells (CellIndivOffset (utranCell)).

  • MeasurementquantitytimeAS Cell 1AS Cell 2AS Cell 3Hysteresis1d/2Hysteresis1d/2TTT1dEvent 1dWhen any (Active Set, Monitored set, and Detected) cell becomes stronger than the best cell in the Active Set, during a time at least equal to timeToTrigger1d, event 1d occursEvent 1d conditionMNotBest: Refers to the measurement of cell within or outside the active set. CIONotBest: Refers to the offset of cell within the active set (CellIndivOffset (utranCell)) or outside the active set (CellIndivOffset (utranRelation)) in relation to other cells.

  • CIOBest: Refers to offset of cell in the active set in relation to other cells (CellIndivOffset (utranCell)). MBest: Refers to the measurement of the cell in the active set.H1d: Refers to Event 1D report hysteresis

  • SRNCMEASUREMENT CONTROL MESSAGEmeasurement criteria

    Measured cell (X)fulfilled the thresholdEvent TriggeredMEASUREMENT REPORTEvent occurred which cells fulfilled the event criteria

    Active Set UpdateActive Set Update CompleteEvaluationEvaluates which cells should be proposed to be added, removed, or replaced in the Active Set

    ExecutionTake ActionSummary

  • INTER RAT HANDOVER (IRATHO) FROM WCDMA TO GSMMeasurementQuantity2d Threshold2F thresholdhysteresis2d/2UMTS CellGSM Cell3A GSM Threshold3A UTRAN ThresholdHysteresis 3A/2Hysteresis 3A/2Go to 2G Hysteresis 2F/2Go back to 3G&Trigger Event 3A and 3G to 2G execution startStart Compressed Mode

  • SRNCCN/UMSCTarget BSSUENode-BINTER RAT HANDOVER (IRATHO) FROM WCDMA TO GSM(Contd)

  • MeasurementQuantityCurrently used frequency2d ThresholdNon-used frequencyStart Compressed ModenonusedFreqThresh4_2bHysteresis 2b/2Hysteresis 2b/2usedFreqThresh4_2bInter Freq HOGo back to 3GHysteresis 2F/2%INTER Frequency HANDOVER&Trigger Event 2b and IF execution start2F threshold

  • SRNC

    ExecutionTake ActionINTER Frequency HANDOVER(Contd)Inter-frequency Handover sequence

  • Inter-frequency Handover TacticINTER Frequency HANDOVER(Contd)Event 2A: The best carrier frequency changes. Event 2C: The quality of non-working carrier frequency is higher than a threshold.

  • Compressed Mode

    Certain idle periods are created in radio frames during which the UE can perform measurements on other frequencies.Compressed mode must be initiated for Inter-RAT/inter-frequency measurement.Two different methods are used to create these idle periodsSF/2HLSHalving of Spreading Factor (SF) Current SF = (Used SF )/2Consume more radio resources to transmit the normal amount of user data. Power CodeHigher Layer Scheduling The amount of data scheduled during compressed frames is reduced ,so that it can fit in the decreased number of available slots.

    Some timeslots in a radio frame are assigned for inter-frequency/Inter-RAT measurement and some are assigned for data transmission.

    This strategy is used for non-real time services with low requirements for delay,

  • 014Radio FrameRadio Frame10 msRc Chip Rate =3.84 Mcps

    Number of Chips in TS= (3.84Mcps*10ms)/15 = 2560 chip

    SF = Chip Rate/ Bit Rate

    # Bits = # Chips / SF

    # of bits =2560/128 =20 *2 = 40 bit

    With in the Frame 40*15 = 600 bit # of bits =2560/64 =40 *2 =80 bit

    With in the Frame 80*7.5=600 bitRadio FrameRadio Frame

  • Channel Switching

  • Channel Switching is applied only to best effort packet data traffic

    Channel Switching is activated in connected mode and handles switches between the different states or to idle mode.

    There are two states in connected mode: Dedicated state (Cell_DCH) Dedicated resources common state (Cell_FACH)Common resources Low bit rate services The switches between dedicated and common states are handled by WCDMA RAN without the involvement of the Core Network.

  • Cell_DCH EUL/HSCell_DCH 384/HSCell_DCH 64/HSIdle modeCell_DCH 64/384Cell_DCH 64/64Cell_FACHCell_DCH 64/128SHO can initiate a switch if it fails to add a RLDown switch based onthroughput or inactivity or coverageDedicated to commonbased on UL/DL userthroughputNo activityUpswitch based on throughputActivityCommon to Dedicatedbased on buffer sizeor activityDedicated ChannelsCommon Channel

  • The Channel Switching algorithm consists of the following sub-algorithms:

    Common to Dedicated Evaluation

    Dedicated to Common Evaluation

    Common to Idle Evaluation

    Dedicated to Dedicated Up switch Evaluation

    Dedicated to Dedicated Down switch Evaluation

    Multi-RAB Up switch Evaluation

    Multi-RAB Down switch Evaluation

  • Channel Switching uses the below as input to the algorithms.

    Buffer load

    Throughput

    Transmitted Code Power

    Switching Counters

    pmNoOfSwDownNgCongShows number of down switches from a dedicated channel to a common channel initiated by congestion control.

    PmNoOfSwDownNgAdmShows number of down switches within dedicated channels initiated by admission control

  • Buffer load(UP Switch)

    The Common to Dedicated Evaluation algorithm monitors the amount of user data buffered in the RNC or UE.

    dlRlcBufUpswitch orulRlcBufUpswitchTime (s)RLC buffer size (bytes) (UL/DL)

    Parameter NameDefault ValueValue RangeResolutionUnitdlRlcBufUpswitch5000..2000100bytesulRlcBufUpswitch2568; 16; 32; 64; 128; 256; 512; 1024; 2048; 3072; 4096; 6144; 8192bytes

  • Throughput (Down Switch)The Dedicated to Common Evaluation algorithm monitors the transmitted user data.

    Time (s)downswitchThresholddownswitchTimerThresholddownswitchTimerdownswitchTimer stopsNo downswitchdownswitchTimerDownswitch requestThroughput (kbps)(UL/DL)

    Parameter NameDefault ValueValue RangeResolutionUnitdownswitchThreshold00..321kbpsdownswitchTimerThreshold00..641kbpsdownswitchTimer[1][0..100][0.5][s]

  • Cell ACell BTransmitted Code PowerThe Coverage Triggered Down switch Evaluation algorithm monitors the DL code power

    Max Code PowerMax Code PowerPower alarm thresholdPower alarm thresholdTransmitted DL Code PowerTransmitted DL Code PowerdownswitchPowerMargindownswitchPowerMarginCoverage TimerCoverage TimerDown switchDown switchTime (s)Time (s)

    Parameter NameDefault ValueValue RangeResolutionUnitdownswitchPwrMargin[1][0 ... 10][0.5][dB] coverageTimer[1][0 ... 10][0.1][s]

  • Load Control

  • Load Control

  • Load Control (Contd)

    PUC (potential user control)

    Based on the cell load PUC works

    If the load becomes heavy ,PUC modifies cell selection and reselection parameters and broadcast them ,PUC leads UEs to neighboring cells with less load

    If the cell load becomes normal PUC uses the parameters configured

    If the cell load becomes light ,PUC modifies cell selection and reselection parameters and broad cast them ,PUC leads UEs to this cell

  • ICAC (intelligent call admission control)

    UE access control procedures 1-UE send a connection setup request

    2-RNC and CN negotiate the service rate according to the requested

    3-RNC judges whether the cell resource allow the access IF yes RNC admits the UEIF no the RNC go to step 4

    4-RNC judges whether pre-emption is allowedIf yes RNC performs pre-emption ,if pre-emption succeed ,the RNC admit the UE If no the RNC go to step 5

    5-RNC Judges weather queuing is allowedIf yes ,the RNC perform queuing ,if queuing success the RNC admit the UEIf no the RNC go to step 6

    6-RNC performs DRD If the DRD success ,the RNC admit the user If no the RNC go to step 7

    7- RNC reject the access request

    Load Control (Contd)

  • Load Control (Contd)

    The admission decision is based onCell available code resource Cell available power resource Node-B resource stateAvailable IUB transport layer resource

  • Load Control (Contd)

    The algorithm Chooses UEs for Pre-emption

    The pre-emption capability of the request Indicating whether this request can preempt a lower priority radio connection or not in case of resource shortage.

    Pre-emption results in the release of one or more RABs according to their priority

    The priority level (1.. 15) where value 15 means 'no priority' and 1 is highest priority.

    The pre-emption capability indicator (PCI) which consists of two values, (Indicates the pre-emption capability of the request)'shall not trigger pre-emption''may trigger pre-emption'.

    The pre-emption vulnerability indicator (PVI) with the values not pre-emptable pre-emptablePVI indicates whether a RAB in the connection can be released due to the admission of a higher priority (pre-emption capable request) or not.

  • Load Control (Contd)LDR load reshuffling When the cell is in basis congestion RNC can take one of the following steps Inter-frequency load handover Rate reduction CS inter RATPS inter RAT

    OLC over load control When the cell is highly over loaded may lead to instability and dropped calls OLC can rapidly reduce the load

  • Admission and congestion control

  • 1- Admission control

    Function blocks new incoming calls block handover attempts

    When High load on the air interface

    How Measurements of uplink interferenceDownlink output power Actual number of users.

  • 2- Congestion control

    FunctionReduces bit rates of existing connections Removes existing connections.

    WhenIn case of overload (increased power requirement of the user)

    HowIt uses Power measurements

    Reduces bit rate (BE) packetsExampleWhen the Cell load rises due to the increased power requirement for UE that is moving away from the RBS.When this load reaches a defined limit the RBS reduce it by delaying Best Effort (BE) packets.This is achieved by switching BE users to lower rate common channels.

    Best effort packetsLittle quality of service (not guaranteed bit rate),i.e. WAP, Email and MMS , *

  • RTWPIFHYSTIFHYSTCongestionCongestion resolvedIFCongUplink Congestion ControlTime

  • DL transmitted powerPwrhystCongestionCongestion resolvedDownlink Congestion ControlTimePWRAdmPWROffsetPwrhyst

  • The following set of system resources are relevant within the Capacity Management scope:

    Per Cell:1-Downlink channelization codes2-Downlink transmitted carrier power3-Air Interface Speech Equivalents (ASE) in uplink and downlink4-Uplink Received Total Wideband Power (RTWP)5-The number of radio links per DL Spreading Factor6-The number of radio links per UL Spreading Factor7-The number of radio links in compressed mode8-The number of serving HS connections9-The number of serving EUL connections10-The number of serving 2 ms TTI EUL connections11-The number of non-serving EUL connections

    Per Hardware Pool:1-RBS hardware utilization

    System Resource

  • Key Performance IndicatorsKPIs

  • Main 3G KPIs Traffic (CS)R99 RABs Establishment success rate RRC success rate Call drop RateHS establishment rate R99 & HS & EUL throughputHandover

  • IRATHO Success Rate100*/HS to FACH100*(/)CDR HSDPA NEW100*(()/(+++))CDR_CS_SP100*(/(+))

  • CDR_CS_VIDEO100*/(+)FACH to HS (/)*100HS2DCHIf =0 Then 1 Else (/)RAB_HSDPA_EST_RATE100*/RAB_PKT_EST_SUC%100*/RAB_SPE_EST_SUC%100*(/)

  • RAB_VID_EST_SUC%100*/RRC_CON_SUC%100*/SHO_Succ_Rate100*/DCH to HSDPA Success Rate %:100*(/)

  • HSDPA

  • Why HSDPA? Gain more throughput per cell and higher bit rate per user.

    HSDPA is based on the following features Higher-order modulationShared channel transmissionShort transmission time interval (TTI)Fast link adaptationFast schedulingFast hybrid automatic-repeat-request (ARQ)Dynamic Power Allocation

    High-Speed Downlink Packet Access (HSDPA)

  • High-Speed Downlink Packet Access (Contd)

  • HSDPA features 1- Short TTI (2 MS)One reason for a shorter TTI is to reduce the air-interface delay by reducing the RTTThis will improve the end-user performance since shorter TTI improves the interaction with TCP/IP.Old releases10 ms20 ms40 ms80 msHSDPA2 ms2- Shared Channel Transmission

    Certain amount of radio resources of a cell (code space and power) is seen as a common are dynamically shared between users in the time domain.

    The main benefit with DL shared channel transmission is to reduce the risk for code-limited capacity and power limited capacity

  • Shared channel transmission(Contd)SF1

    2

    4

    8

    16

    32TTI=2mstimeSharedchannelizationcodesTTI=2msTTI=2msTTI=2msTTI=2msHSDPA features (Contd) Channelization codes allocatedfor HS-DSCH transmission8 codes (example)

  • 3- Higher-Order ModulationHSDPA features (Contd) R99 is based on QPSK modulationTo support higher data rates, higher-order data modulation, such as 16QAMHigher-order modulation is more bandwidth efficient, i.e. can carry more bits per Hertz.Higher-order modulation is also less robust and typically requires higher energy per bit for a given a given error rate

  • HSDPA features (Contd) 4-Fast Link Adaptation

    Radio-channel conditions will typically vary significantly, both in time and between different positions

    Reasons for these variations in channel conditions:

    Different positions within the cell, due to distance dependent path loss and location-dependent shadowing

    Variations in the interference level.The interference level will depend on:The position within the cell, with typically higher interference level close to the cell border.The instantaneous transmission activity of neighbor cells. Own-cell interference

    Multi-path fading, The rate of these variations depends on the speed of the mobile terminal.

  • Multi-path propagationTime dispersionh()01230123HSDPA features (Contd)

  • Direct SignalReflected SignalCombined SignalHSDPA features (Contd) Combined Signal

  • time (mSec)Composite Received Signal StrengthDeep fade caused by destructive summation of two or more multipath reflectionsmsecHSDPA features (Contd) Fast (Rayleigh) Fading due to Multipath relctionsDeep fade caused by destructive summation of two or more multipath reflections

  • Fast link adaptation(Contd)Fast adjustment of the data rate every TTI (2 ms).HSDPA features (Contd)

  • 5- Fast Channel Dependent SchedulingHSDPA features (Contd) User 1User 2TTI=2msTTI=2msTTI=2msTTI=2msTTI=2msTTI=2msTTI=2msScheduled User

  • Scheduling algorithms

    Max C/I RatioAssign the channel to the user with the best channel qualityHigh system throughput but not fair(if user is on cell border)Round Robin (RR)Cyclically assign the channel to users without taking channel conditions into accountSimple but poor performanceProportional Fair (PF)Schedules all users in the cell but prioritize users with better channel quality But ensure that all users receive a guaranteed minimum throughput. It gives ratherHigh throughput, fairHSDPA features (Contd)

  • 6- Fast hybrid automatic-repeat-request (ARQ)P1P1P2NACKP2ACKP3P3HSDPA features (Contd)

  • 7-Dynamic Power AllocationHSDPA features (Contd) PowerMax cell powertimeCCH power

    DCH PowerHSDPA powerHSDPA will take the power left after CCHs and DCHs have taken their parts

    Average power utilization will increase in the network with HSDPA

  • HSDPA Mobility

  • HSDPA introduction3GPP Release 5 extends the WCDMA specification with a new downlink transport channel for packet data, the High-Speed Downlink Shared Channel (HS-DSCH). The HS-DSCH utilizes the remaining transmission power which is not used for the dedicated and common channels. With shared channel transmission, a certain amount of the channelization codes and transmission power in a cell are considered a common resource that is dynamically shared among the users. Max Cell PowerDCH PowerHSDPA powertimePower

  • HS-DSCH - High-Speed Downlink Shared ChannelMapped on one or several (HS-PDSCHs) which are simultaneously received by the UE.In the 3GPP standard, there are up to 15 HS-PDSCHs per cell with the spreading factor fixed 16. The number of HS-PDSCHs per cell is configurable and depending on the license, each cell has up to 5, 10, or 15 HS-PDSCHs.

    High-Speed Shared Control Channel (HS-SCCH) Carries control information to the scheduled UE. The control information required for each 2-ms TTIUE IDCodesModulationCoding%

    High-Speed Dedicated Physical Control Channel (HS-DPCCH) The UE uses this channel to :Request retransmission of the incorrectly received blocks on the HS-DSCH (ACK/NACK)Report CQI is used by the scheduling and link adaptation functions

  • HS-PDSCH User data +Over head bitsUser dataTransport ChannelPhysical Channel

  • The dedicated uplink and downlink channels use soft handover.HS-DSCH do not use soft handover as it is shared transport channel.Mobility for the HS-DSCH is called HS-DSCH cell changeHS-SCCH carries control signaling for the HS-DSCH, and is never in soft handover.HS-DPCCH only capable of softer handovers since it is terminated in the RBS

    HS-DPCCHHS-SCCHHS-DSCHA-DCHIURIUBA-DCHIUBSoft /Softer HOSofter HOCell Change

  • Serving cell change is triggered when:Change of the best cell within the Active set (event 1d HS).Current serving cell should be removed or replaced from the Active set (event 1b or 1c).

    When HSDPA is started, an extra MEASUREMENT CONTROL related to the event 1d HS , is sent to the UE having another MEASUREMENT ID The reason for having a separate event 1d HS is to be able to Use different hysteresis Use different time to trigger parameters to trigger serving HS-DSCH. ItUse a different quality criteria

    HS-DSCH mobility can be divided into the following parts:Serving HS-DSCH Cell Change triggered by change of Best Cell within the Active Set.Serving HS-DSCH Cell Change triggered by removal of the serving HS-DSCH cell from the Active Set.Coverage triggered IF or IRAT HO attempts, HS-DSCH Cell Selection.

  • hsCellChangeAllowed YesYesNoNoYesNoYesNo (No SuitableHS cell is found)TRUEFalsehsToDchTriggerOFFONWhen a serving HS-DSCH Cell Change is triggered by change of best cellblocked

  • hsCellChangeAllowed YesYesNoNoYesNoYesNo (No SuitableHS cell is found)TRUEFalsehsToDchTriggerOFFRNC shall release the connectionONServing HS-DSCH Cell Change triggered by removal of the serving HS-DSCH cell from the Active Set.blocked

  • Coverage Triggered IF or IRAT HO attemptno defined GSM neighborsno defined IF neighborsYesNOYesYesNOhsToDchTriggerONOFFblockedNoYesNO

  • CQI

  • CQI report UE sends a Channel Quality Indicator (CQI) on the uplink (HS-DPCCH)CQIEstimates the number of bits that can be transmitted to the UE using a certain assumed HS-PDSCH power with a block error rate of 10%UE receiver performanceGood UE receiver can report that it can receive more bits than a Bad UE receiver implementation for the same channel conditions.

    PCPICH_RX Received power of the P-CPICH Measurement Power Offset MPO Cell level parameter hsMeasurementPowerOffset Reference power adjustment Given by Table 7A, 7B, 7C, 7D, 7E, 7F or 7G depending on the UE category.

  • Physical layer procedures (FDD), 3GPP TS 25.214CQI algorithm indicates Transport block sizeNumber of HS-PDSCH codesModulation TypeHS-PDSCH PowerHSDPA Scheduler algorithm indicates Which UE to transmit to in the TTI, Available HS-PDSCH transmission power, Available number of HS-PDSCH codes. It does not indicate how much data to transmit.

    CAT6CQI ValueTransport Block SizeNumber of HS-PDSCHModulationReference Power Adjustment11371QPSK021731QPSK032331QPSK043171QPSK053771QPSK064611QPSK076502QPSK087922QPSK099312QPSK01012623QPSK01114833QPSK01217423QPSK01322794QPSK01425834QPSK01533195QPSK0163565516-QAM0174189516-QAM0184664516-QAM0195287516-QAM0205887516-QAM0216554516-QAM0227168516-QAM0237168516-QAM-1247168516-QAM-2257168516-QAM-3267168516-QAM-4277168516-QAM-5287168516-QAM-6297168516-QAM-7307168516-QAM-8

  • Why CQI !

  • Back to Developing Basics

  • PN 1PN 2PN 3PN codes (distinguish each Base Station)Not orthogonalHigh cross correlation propertiesPN1 * PN2 0 (mini. output)

    Channelization Codes (distinguish data channels Coming from each Base Station)Orthogonal CodesOC1 * OC2 = 0

    OC3, OC4OC1, OC2OC5, OC6, OC7OC1, OC2

  • PN 1PN 1PN 2PN 3PN 4

  • Ec/No for most of us is quality measurement metric. It gives us how good or bad the link quality is.However by definition it is confusingRSCPReceived signal code powerReceived power level of pilot channel of a one cell (dBm/mW)Using RSCP we can compare different cellsUsing RSCP handover and cell reselection decisions can be takenRSSISignal power over the complete 5MHZ carrier which include all components received Signal from the current cell and neighboring cells on the same frequencyTheoretically in an isolated cell having only CPICH power with no other channels RSSI CPICH power RSSI will change if the carrier use the DCH or the common channels

  • CPICH Ec/NoPilot channel quality ,energy per chip over total received power spectral densityEc/No= RSCP/RSSIThe Better this value the better the signal can be distinguished from the over all nosieAlways negative Using Ec/No we can compare different cellsUsing Ec/No handover and cell reselection decisions can be takenNoNoise power spectral density Interfering power Non interfering power Thermal noiseTest bed being served by single cellEc/No of UE is Measure of PCPICH =RSCPMeasure of total wide band power =RSSI

  • Assume that UE is in Test bed being served by single cell`Cell MAXTXPOWER 20 watt (43 dBm)Assuming that 10 % of the cell power is dedicated for CPICH 2 watt (33 dBm)If you have no DCH or HS channels Ec/No= 10 log (CPICH Power/Total transmitted power)Ec/No=10 log (2w/2w)= 10 log 1 = 020 wattPower2 wattAssume that you start HS sessionEc/No= 10 log (CPICH Power/Total transmitted power)Ec/No=10 log (2w/20w)= -10 dB (Poor value)Ec/No will always give a false value for an HSDPA user

  • Deviating CQI reports lead to faulty decisionsCQI accuracy will continue to vary depend on :UE model UE vendor

    Deviating CQIUE that consistently overestimates the channel qualityScheduled too often, at the price of other users. Experience a block error rate that is higher than the target 10%, with more retransmissions and reduced system throughput and increased service delayUE instead underestimates the channel quality Scheduled too seldom. Experience a Block error rate will be lower than 10%, which will lead to lower transmitted data rates than possible and hence reduced system throughput.

    In both cases, both system throughput and end-user experience of the service is negatively impacted.

    121201918CQI Adjustment

  • To avoid the negative system impact due to inaccurate CQI reports, CQI adjustment algorithm RBS works on the ACKs and NACKs received from the UE to determine if the UE is overestimating or underestimating the channel quality. The algorithm make every effort to achieve a block error rate of 10%

    The output from the adjustment algorithm is CQIadjusted, The CQI adjustment algorithm is an optional feature and can be enabled on cell level through parameter cqiAdjustmentOn.

    BLER

  • Thank you

  • Thanks

    The Multiplexer allows various data channels to share the same timeslot.The timeslot selector allows multipletransmitters to share the same carrierfrequency,

    ******Eb=(E*Sec)/( bit*Sec) =S/RbNo=N/BW=N/RCEb/No=(S*Rc)/(Rb*N)Eb/No=(S/N)*(Rc/Rb)Eb/No=SNR+PgPg=Rc/Rb** If the parameter is set to FIXED, both Power Balancing and downlink Inner Loop PowerControl are disabled, and the downlink power is kept at a constant level fixedPowerDl(configurable by the operator) during the call. If the parameter is set to NO BALANCING, downlink Inner Loop Power Control is active, butPower Balancing is never started. If the parameter is set to BALANCING, Power Balancing is activated and runs in parallel withdownlink Inner Loop Power Control when more than one Radio Link Set (RLS) is involved inthe connection between the UE and UTRAN. Downlink Inner Loop Power Control is alwaysactive. If the parameter is set to FIXED BALANCING, downlink Inner Loop Power Control is active aslong as one single RLS is involved in the connection between the UE and UTRAN. As soon asan additional RLS enters the active set, downlink Inner Loop Power Control is disabled, andPower Balancing is activated. In this latter case, the downlink power converges to aconfigurable reference power level, fixedRefPower, and stays there as long as the activeset includes multiple RLSs.

    **The RAKEreceiver buffers these signals according to their delay, decodes them, andperforms maximum ratio combining. This gives protection against fading, andmacro-diversity and multipath diversity gain can be obtained depending onradio conditions and consequently the RBS output power can be lowered whilemaintaining sufficient connection quality.*However, there is a trade-off between Soft/Softer Handover and systemcapacity. A UE involved in Soft/Softer Handover uses several radio links, moreDL channelization codes, and more DL power than a single-link connection.Consequently, if all the UEs connected to a particular RNC are considered,more resources are needed in the RBSs, more resources over the Iub and Iurinterfaces, and more resources in the RNC. For this reason, the number ofradio links involved in the Soft/Softer handover must be limited. Radio networkplanning and optimization must determine the size of the handover areasbetween the cells.*Evaluates which cells should be proposed to be added, removed, or replaced in the Active Set

    ****64 QAM*The instantaneous transmission activity of neighbor cells. when high-rate data traffic contributes a major part of the overall traffic.

    ** ImplementiWhen HSDPA is started, an extra MEASUREMENT CONTROL related to the event 1d HS , is sent to the UE having another MEASUREMENT ID than the MEASUREMENT CONTROL message. ng soft handover for the high-speed channels is not feasible, since fast channel-dependent scheduling is handled by a single RBS.****