MobileComm Technologies India Pvt. Ltd. Dallas . Atlanta . Washington . LA . Sao Paulo . New Delhi . Toronto . Muscat. SydneyWCDMA Fundamantels

Copyright 2010 MobileComm Technologies India Pvt. Ltd. All rights reserved MobileComm is committed to providing our customers with quality instructor ledTelecommunications Training.This documentation is protected by copyright. No part of the contents of thisdocumentation may be reproduced in any form, or by any means, without the prior written consent of MobileComm Technologies .Document Number: RK/CT/3/2010This manual prepared by: MobileComm Technologies

MobileComm Technologies(India)Pvt. Ltd. 424, First Floor, Udyog Vihar Phase -4, Gurgaon-122002Headquarter: MobileComm Professionals Inc. 1255 West 15th Street, Suite 440 Plano, TX, 75075 Tel: (972) 633-5100 Fax: (972) 633-5106 www.mcpsinc.com

WCDMA Air InterfaceWCDMA Principles & Spreading codesOverview of Radio Resource Management (RRM)Load controlAdmission ControlPacket SchedulerResource ManagerPower ControlHandover ControlCapacity limitation and Cell breathing Rake receiverObjectivesAt the end of this session, you will be able to:W-CDMA Fundamantels

AgendaWCDMA Air InterfaceWCDMA Principles & Spreading codes Overview of Radio Resource Management (RRM)Capacity limitation and Cell breathing Rake receiver

PowerFrequencyTimeFrequencyTimePowerFDMATDMAW-CDMAAccess Technologies

WCDMA Cocktail Party

UMTS Air Interface technologiesUMTS Air interface is built based on two technological solutionsWCDMA FDDWCDMA TDD

WCDMA FDD is the more widely used solutionFDD: Separate UL and DL frequency bandWCDMA TDD technology is currently used in limited number of networksTDD: UL and DL separated by time, utilizing same frequency

Both technologies have own dedicated frequency bands

This course concentrates on design principles of WCDMA FDD solution, basic planning principles apply to both technologies

Duplex Spacing: 190 MHzFDDTimeFrequencyPower5 MHz5 MHzCode MultiplexULDLTimeFrequencyPowerTDD5 MHzCode Multiplex&Time Division 666.67 msUMTS USER 2UMTS USER 1W-CDMA: FDD or TDDUMTS Air Interface technologies

W-CDMA FDD mode for the paired banduplink and downlink are separated in frequencyTD-CDMA TDD mode for the unpaired banduplink and downlink are separated in timeflexible time duration for uplink and downlink for asymmetrical traffic

UMTS Air Interface technologies

WCDMA Technology5+5 MHz in FDD mode 5 MHz in TDD modeWCDMA CarrierUsers share same time and frequency

IMT-2000 frequency allocationsITU-R responsible for world-wide Radio Communication aspects setting requirements for 3G / 4G Mobile Communication (IMT-2000 / IMT-Advanced)

World Radio Conference WRC 1992: IMT-2000 frequency allocation proposals

national regulation authorities: responsible for national frequency allocation & licensing process GSM spectrum refarming is also possible

UMTS FDD Frequency band evolutionRelease 99I 1920 1980 MHz 2110 2170 MHz UMTS only in Europe, Japan, IndiaII 1850 1910 MHz1930 1990 MHzUS PCS, GSM1900New in Release 5III 1710-1785 MHz 1805-1880 MHzGSM1800New in Release 6IV 1710-1755 MHz2110-2155 MHzUS 2.1 GHz bandV 824-849MHz869-894MHz US cellular, GSM850VI 830-840 MHz875-885 MHzJapanNew in Release 7VII 2500-2570 MHz2620-2690 MHzVIII 880-915 MHz925-960 MHzGSM900IX 1749.9-1784.9 MHz1844.9-1879.9 MHz Japan

UMTS frequency allocations Duplex Frequency : 2110-1920 = 190 MHzBandwidth :1980-1920 = 60 MHzCarriers : 60 / 5 = 12UL : 1959 MHz 1979 MHzDL : 2149 MHz 2169 MHz

Frequency channel numbering UTRA Absolute Radio Frequency Channel Number (UARFCN) UARFCN formula (3GPP 25.101 and 25.104): UARFCN = 5 . f [MHz] Uplink/Downlink Center Uplink/Downlink with 0.0 MHz

Center Frequency Center Frequency fcenter Consequence of UARFCN formula (see previous slide): fcenter must be set in steps of 0.2MHz (Channel Raster=200 kHz) fcenter must terminate with an even number (e.g 1927.4 not 1927.5) fcenter values Uplink (1920Mhz-1980MHz) 1922.4MHz

WCDMA FDD technologyMultiple access technology is wideband CDMA (WCDMA)All cells at same carrier frequencySpreading codes used to separate cells and usersSignal bandwidth 3.84 MHz

Multiple carriers can be used to increase capacityInter-Frequency functionality to support mobility between frequencies

Compatibility with GSM technologyInter-System functionality to support mobility between GSM and UMTS

UMTS & GSM Network Planning

Differences between WCDMA & GSMHigh bit rates

AgendaWCDMA Air InterfaceWCDMA Principles & Spreading codes Channelization CodeScrambling Code Overview of Radio Resource Management (RRM)Capacity limitation and Cell breathing Rake receiver

WCDMA FeaturesSeparate users through different codesLarge bandwidthContinuous transmission and receptionCode planning - Frequency reuse is 1No frequency planningScrambling code planning5 MHz carrier separationFast Power ControlSoft/Softer HandoverAdmission ControlCongestion Control

3GPP : 3rd Generation Partnership Projecthttp://www.3gpp.org

Separates users through different codes Codes are used for two purposes: Differentiate channels/users Spreading the data over the entire bandwidth

fCodetMS 1 MS 2 MS 3 5 MHz WCDMA (5 MHz) IS-95 (1.25 MHz) CDMA2000 (1.25, 3.75 MHz)Spreading PrincipleDirect Sequence Spreading - Code Division Multiple Access (DS-CDMA)

Spreading PrincipleSpreading code = Scrambling code + Channelization code

Scrambling codes (Repeat period 10 ms=38400 chips)Separates different mobiles (in uplink)Separates different cells (in downlink)

Channelization codesSeparates different channels that are transmitted on the same scrambling codeOrthogonal Variable Spreading Factor (OVSF) codesPeriod depends on data rate

Spreading CodeSpread SignalDataAir InterfaceBits (In this drawing, 1 bit = 8 Chips SF=8)Baseband DataDespreadingCDMA principle - Chips & Bits & Symbols

Common Technical Terms Bit, Symbol, Chip:A bit is the input data which contain informationA symbol is the output of the convolution, encoder, and the block interleavingA chip is the output of spreading

Processing Gain:Processing gain is the ratio of chip rate to the bit rate. Closely related to spreading factor, SF.

Forward direction/ Downlink : Information path from base station to mobile station

Reverse direction/ Uplink : Information path from mobile station to base station

Block Diagram of WCDMA SystemSource codingChannel codingSpreadingModulationSource decodingChannel decodingDespreadingDemodulationRadio channel

WCDMA SystemSource CodingVoice : Adaptive multirate technique with rate 4.75kbps 12.2kbps

Channel CodingCRC Attachment.Check for error during transmission.Voice : CRC check returns error, discard informationData : CRC check returns error; ask for retransmission

Convolutional or Turbo CodingConvolution coding for voice and low speed signalingTurbo Coding for large data transmission. Better performance than convolutional coding

Interleaving Distribute error over data transmitted

Rate MatchingMatch symbol rate to that accepted by spreadingRate matching technique : Repeat or puncturing

Energy BoxFrequency BandDuration (t = 1/Rb)Power/HzOriginating BitReceived BitEnergy per bit = Eb = constHigher spreading factor Wider frequency band Lower power spectral densityBUTSame Energy per Bit

Spreading PrincipleUser information bits are spread into a number of chips by multiplying them with a spreading codeThe chip rate for the system is 3.84 Mchip/s and the signal is spread in 5 MHzThe Spreading Factor (SF) is the ratio between the chip rate and the symbol rateThe same code is used for de/spreading the information after it is sent over the air interface.

Spreading TechnologySpreading consists of 2 stepsChannelization operation: Transforms data symbols into chips. Thus increasing the bandwidth of the signal. The number of chips per data symbol is called the Spreading FactorSF.The operation is done through multiplication with OVSF code.Scrambling operation is applied to the spreading signal.

DL & UL Channelisation CodesWalsh-Hadamard codes: orthogonal variable spreading factor codes (OVSF codes)SF for the DL transmission in FDD mode = {4, 8, 16, 32, 64, 128, 256, 512}SF for the UL transmission in FDD mode = {4, 8, 16, 32, 64, 128, 256} Good orthogonality properties: cross correlation value for each code pair in the code set equals 0In theoretical environment users of one cell do not interfere each other in DLIn practical multipath environment orthogonality is partly lost Interference between users of same cellOrthogonal codes are suited for channel separation, where synchronisation between different channels can be guaranteedDownlink channels under one cellUplink channels from a single userOrthogonal codes have bad auto correlation properties and thus not suited in an asynchronous environmentScrambling code required to separate signals between cells in DL and users in UL

Channelisation Code TreeSF=1SF=2SF=4SF=8SF=16SF=256SF=512...

SF and Service RateSymbol Rate*SF=Chip Rate

In WCDMA system, if chip rate=3.84MHz, SF=4, then symbol rate=960Kbps.

Symbol Rate=(Service Rate + Checking Code)*Channel Coding Rate* Repeat or Puncture Rate

In WCDMA system, if service rate=384Kbps, channel coding=1/3 Turbo coding, then symbol rate=960Kbps;

Correlation Function

SpreadingSpreading Principle

Spread Spectrum Gain

Benefits of SpreadingMODDEMDETFMOD - modulationDEM - demodulationF - filteringDET - detectionNBI - narrow-band interferenceWBI - wide-band interference

Frequency (Hz)

Voice user (R=12,2 kbit/s)

Packet data user (R=384 kbit/s)

Power density (W/Hz)

RFrequency (Hz)

Gp=W/R=24.98 dBPower density (W/Hz)

RGp=W/R=10 dB

Spreading sequences have a different length Processing gain depends on the user data rate

Processing Gain ExamplesProcessing gain:

The more processing gain the system has, the more the power of uncorrelated interfering signals is suppressed in the despreading process.

Thus, processing gain can be seen as an improvement factor in the SIR (Signal to Interference Ratio) of the signal after despreading.

Example: Voice AMR 12.2 Kbps Gp= 10*log(3840000/12200)= 25 dB.After despreading the signal power has to be typically few dB above the interference and noise: Eb/No = 5dB; therefore the required wideband signal-to-interference ratio is 5dB Gp= -20 dB.In other words, the signal power can be 20 dB under the interference and the WCDMA receiver can still detect the signal.Processing gain

Transmission PowerFrequency5MHzPower densityTimeHigh bit rate userLow bit rate user

Channelization CodesCC1, CC2CC3, CC4CC5, CC6, CC7CC1 , CC2, CC3CC1, CC2CC1, CC2, CC3, CC4In the Uplink, Channelization Codes are used to distinguish between data (and control) channels from the same UEIn the Downlink, Channelization Codes are used to distinguish between data (and control) channels coming from the same NodeBChannelization Codes have different length depending on the bit rate

After the Channelization Codes, the data stream is multiplied by a special code to distinguish between different transmitters.

Scrambling codes are not orthogonal so they do not need to be synchronized

The separation of scrambling codes is proportional to the code length longer codes, better separation (but not 100%)

Scrambling codes are 38400 chips longScrambling Codes

Scrambling CodesIn the Downlink, the Scrambling Codes are used to distinguish each cell (assigned by operator SC planning)In the Uplink, the Scrambling Codes are used to distinguish each UE (assigned by network)

Scrambling Code planning exampleSC 0SC 16SC 40SC 32SC 56SC 24SC 1SC 17SC 41SC 33SC 64SC 8SC 48SC 9SC 25SC 57SC 65SC 49

Half rate speechFull rate speech128 kbps384 kbps 2 Mbps(QPSK modulation)Physical Layer Bit Rates (DL)Modulation :DL : QPSK, 16 QAM.UL : BPSK

Spreading factor

Channel symbol rate

(ksps)

Channel bit rate

(kbps)

DPDCH channel bit rate range (kbps)

Maximum user data rate with -rate coding (approx.)

512

7.5

15

36

13 kbps

256

15

30

1224

612 kbps

128

30

60

4251

2024 kbps

64

60

120

90

45 kbps

32

120

240

210

105 kbps

16

240

480

432

215 kbps

8

480

960

912

456 kbps

4

960

1920

1872

936 kbps

4, with 3 parallel codes

2880

5760

5616

2.3 Mbps

DL & UL Scrambling CodesDL Scrambling CodesPseudo noise codes used for cell separation512 Primary Scrambling Codes

UL Scrambling CodesTwo different types of UL scrambling codes are generatedLong scrambling codes of length of 38 400 chips = 10 ms radio frameShort scrambling codes of length of 256 chips are periodically repeated to get the scrambling code of the frame lengthShort codes enable advanced receiver structures in future

512 DL Primary Scrambling Codes16.7 million UL Scrambling Codes

Basic W-CDMA Terminologies Eb/NoCINCEb/NoW-CDMATDMA-GSMPower spectrum1111111222233333244444Eb/Io is the Bit Energy we obtain after despreading in the presence of the Noise generated by all other users and the Noise from NodeB equipment.

Eb/No -> Eb = Energy per bit, No = Noise Spectral Density[ Sensitivity of Base Station]Uplink Eb/No = Minimum Signal/Noise to achieve any ServiceBER (Bit Error Rate) = Function of Eb/NoSNR = C/I = Eb/No - Processing GainBasic W-CDMA Terminologies

Sheet1

CS 12.2CS 64PS 64PS 128PS 384

Bit rate (kbps)12.26464128384

UL Eb/No (dB)4.933.22.62.1

Spreading Factor256

Processing gain (dB)2518181510

UL C/I (dB)-20-15-15-12-8

Spreading Factors

UplinkbpsCS19

4960CS213.4

8480CS315.6

16240CS421.4171.2

32120

6460MCS18.8

12830MCS211.2

25615MCS314.8

MCS417.6

DownlinkMCS522.4

41920MCS629.6

8960MCS744.8

16480MCS854.4

32240MCS959.2473.6

64120

12860

25630

51215

Sheet3

Interference levelExample: 2 UEs at the same distance from the BTS using 2 data ratesEb/No requiredSF = 128Service provided: SpeechInterference levelEb/No requiredSF = 8Service provided: Data 144User 2 needs more power for the UL & DL for the same quality as user 1UE2UE1Speech 8 kbpsData 144 kbpsThe higher the SF, the less power requiredReceived powerReceived powerCoverage Limits

SF = 128Speech 8 kbpsData 64 kbpsData 384 kbpsNode BSF = 32SF = 4Coverage Limits

Channelisation and Scrambling Codes

Channelisation code

Scrambling code

Usage

Uplink: Separation of physical data (DPDCH) and control channels (DPCCH) from same terminal

Downlink: Separation of downlink connections to different users within one cell

Uplink: Separation of mobile

Downlink: Separation of sectors (cells)

Length

4256 chips (1.066.7 (s)

Downlink also 512 chips

Different bit rates by changing the length of the code

Uplink: (1) 10 ms = 38400 chips or (2) 66.7 (s = 256 chips

Option (2) can be used with advanced base station receivers

Downlink: 10 ms = 38400 chips

Number of codes

Number of codes under one scrambling code = spreading factor

Uplink: 16.8 million

Downlink: 512

Code family

Orthogonal Variable Spreading Factor

Long 10 ms code: Gold code

Short code: Extended S(2) code family

Spreading

Yes, increases transmission bandwidth

No, does not affect transmission bandwidth

Scrambling codeChannelization code 1Channelization code 2Channelization code 3User 1 signalUser 2 signalUser 3 signalCodes Multiplexing 1 - Downlink Transmission on a Cell Level

Channelization code2 - Uplink Transmission on a Cell LevelScrambling code 2User 2 signalScrambling code 3User 3 signalChannelization codeChannelization codeScrambling code 1User 1 signalCodes Multiplexing

Channelization and Scrambling Codes2 data channels (voice, control) SC3 + CC1 + CC22 data channels (14 kbps data, control) SC4 + CC1 + CC23 data channels (voice, video, control) SC2 + CC1 + CC2 + CC33 data channels (voice, video, control) SC5 + CC1 + CC2 + CC34 data channels (384 kbps data, voice, video, control) SC6 + CC1 + CC2 + CC3 + CC44 data channels (384 kbps data, voice, video, control) SC2 + CC4 + CC5 + CC6 + CC72 data channels (voice, control) SC1 + CC1 + CC21 data channels (control) SC1 + CC3Voice ConversationUplink Packet DataVideoconferenceVideoconference with DataPilot, Broadcast SC1 + CCP + CCBPilot, Broadcast SC2 + CCP + CCB

DL Spreading and Multiplexing in WCDMAUser 3User 2User 1BCCHPilotXCODE 1XCODE 2XCODE 3XCODE 4XCODE 5+XSCRAMBLING CODERF3.84 MHzRF carrier3.84 MHz bandwidthCHANNELISATION codes:P-CPICHP-CCPCHDPCH1DPCH2DPCH3

Physical Layer StructureFrame #0Frame #1Frame #iFrame #4095System frame = 4096 frames = 40.96 secondsSlot #0Slot #1Slot #jSlot #14Frame = 15 slots = 10 ms = 38400 chipsSlot = 0.667 ms = 2560 chips UMTS Frame Format(38400*1000/10 = 3.84 Mcps)

WCDMA Parameters

Sheet1

ParametersWCDMA

Chip rate3.84 Mcps

Frame length10 or 2 ms

ModulationDownlink: QPSK; 16QAMUplink: BPSK

Bandwidth5 MHz

VocoderAlgebraic Code Excited Linear Prediction Coder(ACELP)

Base synchronizationAsynchronization

Power control rate1500 Hz

Cell identificationUnique scrambling code (Gold code)

Channelization codeOVSF code

Sheet2

Sheet3

AgendaWCDMA Air InterfaceWCDMA Principles & Spreading codes Overview of Radio Resource Management (RRM)Load controlAdmission ControlPacket SchedulerResource ManagerPower ControlHandover ControlCapacity limitation and Cell breathing Rake receiver

Radio Resource ManagementRRM is responsible for optimal utilisation of the radio resources: Transmission power and interference Logical codesThe trade-off between capacity, coverage and quality is done all the timeMinimum required quality for each user (nothing less and nothing more) Maximum number of usersThe radio resources are continuously monitored and optimised by several RRM functionalitiesservice qualitycell coveragecell capacityOptimizationand Tailoring

RADIO RESOURCE UTILIZATIONTo adjust the transmit powers in upilnk and downlink to the minimum level required to enshure the demanded QoSTakes care that a connected user is handed over from one cell to another as he moves through the coverage area of a mobile network.Let users set up or reconfigure a radio access bearer(RAB) only if these would not overload the system and if the necessary resources are available.Takes care that a system temporarily going into overload is returned to a non-overloaded situation.To handle all non-realtime traffic,allocate optimum bit rates and schedule transmission of the packet data, keeping the required QoS in terms of throughput and delays. To control the physical and logical radio resources under one RNC;to coordinate the usage of the available hardware resouces and to manage the code tree.Basic RRM functions* Power Control* Handover Control* Congestion Control* Resource Management

Load control

Packet data scheduling

Congestion Control

Radio Resource Management

Power Control

Handover Control

Resource Manager

Admission control

RRM FunctionalitiesLC Load ControlAC Admission ControlPS Packet SchedulerRM Resource ManagerPCPower ControlHCHO Control

LC performs the function of load control in association with AC & PSLC updates load status using measurements & estimations provided by AC and PSContinuously feeds cell load information to PS and AC;Interference levels (UL)BTS power level (DL)

LCACPSNRT loadLoad change infoLoad statusLoad Control (LC)

Load Control Load StatusLoad thresholds set by radio network planning parametersOverloadthreshold xLoad Targetthreshold yPowerTimeLoad MarginOverloadNormal loadMeasured loadFree capacity

Checks that admitting a new user will not sacrifice planned coverage or quality of existing connections

Admission control handles three main tasksAdmission decision of new connectionsTake into account current load conditions (from LC) and load increase by the new connectionReal-time higher priority than non-real timeIn overload conditions new connections may be rejectedConnection QoS definitionBit rate, BER target etc.Connection specific power allocation (Initial, maximum and minimum power)Admission Control (AC)

Packet Scheduler (PS)PS allocates available capacity after real-time (RT) connections to non-real time (NRT) connectionsEach cell separatelyBased on QoS priority level of the connectionIn overload conditions bit rates of NRT connections decreased

PS selects allocated channel type (common, dedicated or HSPA)

PS relies on up-to-date information from AC and LC

Capacity allocated on a needs basis using best effort approachRT higher priority

Resource Manager (RM)Responsible for managing the logical radio resources of the RNC in co-operation with AC and PSOn request for resources, from either AC(RT) or PS(NRT), RM allocates:DL spreading codeUL scrambling code

AgendaWCDMA Air InterfaceWCDMA Principles & Spreading codesOverview of Radio Resource Management (RRM)Load controlAdmission ControlPacket SchedulerResource ManagerPower ControlHandover ControlCapacity limitation and Cell breathing Rake receiver

Power ControlConcept : Power is a common resource in WCDMA

Goal : Ensure sufficient received energy per information bit for all communication links

Strategy : Power control on COMMON CHANNELS ensures there is sufficient coverage to establish connections and transfer date on common transport channels

Power control on DEDICATED CHANNELS (DCH) ensures sufficient connection quality while minimizing impact on other connections.

Power Control or Rate Control

Power control strategy (R99): adjust transmitted power while keeping the data rate constantRate control strategy (HSDPA): adjust the data rate while keeping the transmitted power constant

Before despreadingAfter despreadingNear-Far-ProblemUp to around 80 dB attenuation between UE1 and UE2If UE1 and UE2 transmitted with the same power, UE1 would jam UE2 : so-called near-far effectSolution : power controlNeed for an efficient power control able to fight against slow AND fast fading!

Power Control TypesOpen loop power ControlInitial power settingOuter Loop (RNC)Adjust quality target dependent on performanceInner Loop (fast power control-NodeB)compensates for fading channelsneeds dedicated control channel for power control commands

UL Outer Loop Power ControlOpen Loop Power Control (Initial Access)Closed Loop Power ControlRNCNode BUEDL Outer Loop Power ControlPower Control typesBLER target

Open Loop Power Control Controlled by UE. Determine UE initial transmission power for random access procedure. Not in use when inner loop power control running. UE obtain information from network on: CPICH power Uplink interference level Constant value (Default = 2dB) UE Initial Power = CPICH power CPICH_RSCP + UL interference + ConstantSystem information :CPICH power, UL interference & constantPRACH Tx power

Power Ramping on PRACH

powerOffsetP0powerOffsetP0powerOffsetPpmOpen Loop Power Control

PRACH

AICH

Preamble Sequence

1st transmitted preamble

Increase power until heard

Once preamble is heard, increase power for message

Message (Control Part)

Preamble heard and Acquisition Indicator sent

UL

DL

Inner Closed Loop Power ControlPower Control Bit Located in UE & NodeB

Controls power of dedicated physical channels

Power controls occurs at 1500Hz, thus known as fast power control

NodeB and UE continuously measure and compare SIRmeasured with SIRthreshold value, and inform each other to increase /reduce its power accordingly.With Optimum Power ControlReceived power at NodeB(SIR)measuredNodeBUE2UE3UE1UE4SIR threshold

Outer Closed Loop Power Control Adjust SIR for every user

Needed to keep track of changes in radio environment

Aims to provide required quality

If SIRthreshold reaches its maximum, system has to perform inter-frequency/inter-system handover RRC connection release

BER/BLER ValueChange in (SIR)thresholdRNCSIR threshold

Power ControlTX Power is adjusted regularly so that each connection is received with the required Eb/No of its serviceUplink: Avoid Near-Far-Problem Downlink: Power share allocation

Policy: No one gets a higher quality (Eb/No) than he needs. Everyone gets exactly the required quality or is not served at allno unnecessary increase of interference for other mobilesno waste of common power resource in the downlink

PC Gain:Lower Eb/No

Importance of Power ControlMinimizes the Interference and there by enhances capacity and quality.It helps allowing as many users as possible while keeping the interference as minimum as possibleIt maintains the quality of all radio connections by controlling the transmit power in both the links.Power Control aims at using the minimum required SIR for the quality of connection to remain sufficient. No excessive quality.Power Control on common channels ensures that their coverage is sufficient for call setupIt provides protection against slow fading and fast fading.Efficient power control avoids the near-far problem.Power control works efficiently during transmission gap in compressed mode by bring the SIR back close to the target SIR.It helps reducing the battery consumption

AgendaWCDMA Air InterfaceWCDMA Principles & Spreading codesOverview of Radio Resource Management (RRM)Load controlAdmission ControlPacket SchedulerResource ManagerPower ControlHandover ControlCapacity limitation and Cell breathing Rake receiver

Handover Control (HC)HC is responsible for:Managing the mobility aspects of an RRC connection as UE moves around the network coverage areaMaintaining high capacity by ensuring UE is always served by strongest cell

Soft handoverMS handover between different base stationsSofter handoverMS handover within one base station but between different sectorsHard handoverMS handover between different frequencies or between WCDMA and GSM

Soft/Softer HandoverSoft/softer handover is important for efficient power control. Without soft/softer handover there would be near-far scenarios of a UE penetrating from one cell deeply into an adjacent cell without being power controlled by the latter.

Soft Handover: UE connected to two or more NodeBs at the same time.

Softer Handover: UE connected to two or more sector of the same NodeB.

Macro-DiversitySofter HandOverNode B(BTS)RNCData ULData UL1Data UL2

Data ULData ULData DLData DLData DL1Data DL1Data DL2Data DL

Data DL2Data UL

Macro-DiversitySoft HandOver Intra RNCRNCData UL1Data UL1Data UL2

Data ULData ULData DLData DL1Data DL1Data DL1Data DL2Data DL

Data DL2Data ULData DL2Data UL2Data UL2Data UL1

Soft Hand Over Inter RNC: Serving RNC (SRNC) and Drift RNC (DRNC)Node B(BTS)SRNCDRNCNode B(BTS)Data ULData ULData ULData UL1Data UL2Data UL2Data UL1Data UL2

Data ULData ULData DLData DL2Data DL2Data DL1Data DL2Data DL1Data DL1Data DL2Data DL

UESoft HandOver Inter RNC

Hard HandoverHard handovers are typically performed between WCDMA frequencies and between WCDMA and GSM cellsGSM/GPRSGSM/GPRSf1f2f1f2f2f2Inter-System Handovers (ISHO)Inter-Frequency Handovers (IFHO)

In UL selection of the best signal on a frame basis at RNC level - selection diversityIn DL Maximum Ratio combining due to RAKE receiver at UEFor UL & DL good decorrelation due to different locations of Node Bs many multipathsIn UL Maximum. Ratio Combining at Node B

In DL Maximum Ratio combining due to RAKE receiver at UE

For UL & DL less decorrelation due to same location of sectors less multipathsSoft HOSofter HOSoft/Softer Handover

Soft/Softer Handover Power ControlUplink Power is based on information (TPC bits) from both NodeBs to which the UE is connected. The UE will decrease its output power in all cases except when both NodeBs send increase power commands.Downlink Power control for both NodeBs is based on one signal (TPC bits) from the UE (it does not distinguish between NodeBs and the decision is base on the combined output from the RAKE receiverUL Power controlDL Power control

AgendaWCDMA Air InterfaceWCDMA Principles & Spreading codesOverview of Radio Resource Management (RRM)Capacity limitation and Cell breathing Rake receiver

Few Basics.COVERAGE

CAPACITY

QUALITY

POWER

Understanding Power Control LOWER Power Per User HIGHER Number of Users

HIGHER Power Per User LOWER Number of Users

Interference No or Improper Power Control leads to High interference that impacts Coverage, Capacity and Quality

Power Ctrl ON OFF

UL/DL Capacity LimitationScenario 1: Capacity limitation due to UL interference The cell cant serve UE1 because the increase in UL interference by adding the new user would be too high, resulting in a high risk of drops Scenario 2: Capacity limitation due to DL powerThe cell cant serve UE2 because its using all its available power to maintain the connections to the other UEs UE1UE2Scenario 1Scenario 2

Node BNode BFully loaded systemUnloaded systemCell BreathingThe more traffic, the more interference and the shorter the distance must be between the Node B and the UE.The traffic load changes in the system causes the cells to grow and shrink with time

AgendaWCDMA Air InterfaceWCDMA Principles & Spreading codesOverview of Radio Resource Management (RRM)Capacity limitation and Cell breathing Rake receiver

Multipath Propagation2tTime DispersiontMaximum ratio combining1t0t3tMultiple paths possibly cause destructive interference between different replica of the desired signal

The Rake ReceiverEach multi-path component is called a finger

Estimation of radio channel properties for each finger:delayamplitude and PhaseThe Rake receiver combines multi-path components by coherent combining of multi-path components belonging to the respective user.

Maximum ratio combining RAKEEach finger tracks a different multipath component and other cells during Soft Handover A maximum ratio combining produces the outputSearch Finger is used to determine when to perform handoversCOMB INERPower measurements of neighbouring NodeBsSum of individual multipath componentsFinger #1Finger #2Finger #3Finger #NBuffer/delayCorrelatorsChannelSearcher Finger

TXD(t)Delay 0Delay 1C(t-0)+C(t-1)Delay (1)RXC(t-n)Delay (0)Delay (n)RXRXC(t)01nTake advantage of multipath diversityTaking advantage of Multipath: Rake ReceiverUESpreading &Scrambling

www.mcpsinc.com

*Sween J Ambat2006-09-07*The transmission medium is a resource that can be subdivided into individual channels according to different criteria that depend on the technology used.Heres how the three most popular radio technologies establish channels:FDMA (Frequency Division Multiple Access)Each user is on a different frequencyA channel is a frequency.TDMA (Time Division Multiple Access)Each user is on a different window in time (time slot)A channel is a specific time-slot on a specific frequency.W-CDMA (Wide-band Code Division Multiple Access)Each user uses the same frequency all the time, but it is mixed with different distinguishing code patterns.A channel is a unique (set of) code pattern(s).WCDMA Basics and Comparison with GSM2005-09-26*The possibility to operate in either FDD or TDD mode is allowed for efficient utilization of the available spectrum according to the frequency allocation in different regions. FDD and TDD are defined as follows: FDDA duplex method whereby the uplink and downlink transmissions use 2 separate frequency bands: Uplink: 1920 MHz - 1980 MHzDownlink: 2110 MHz - 2170 MHzEach carrier is 5 MHz wide and the uplink channel is 190 MHz away from the downlink. So there are up to 12 pairs of carriers.

TDDA duplex method whereby the uplink and downlink transmissions are carried over same frequency using synchronized time intervals. The carrier still uses a 5 MHz band. FDD mode is the preferred mode for macro-cellular applications.TDD mode is the preferred mode for the unpaired part of the spectrum. Because each time-slot can be assigned a different direction, the TDD mode offers a great flexibility to manage duplex and asymmetric traffic. The TDD spectrum will be used for low mobility coverage in urban areas.

*two modes -> multi mode terminals!compromise! Two proposalsThe Guard Bands are needed to reduce the interference b/w different 5 MHz WCDMA carriers.The allocation of frequency bands for FDD WCDMA is specified by 3GPP in TS25.104.3GPP release 99 specifies operating bands I and II. Release 5 specifies operating bands I, II and III. Release 6 specifies operating bands I, II, III, IV, V and VI.Operating band I is at 2100 MHz and represents the core 3G spectrum allocation. Operating band II is at 1900 MHz and helps to satisfy the requirements of America. Operating band V is at 850 MHz and represents an extension band for future use.Duplex spacings vary from 45 MHz for operating bands V and VI, to 400 MHz for operating band IV. Larger spacings increase the importance of treating the uplink and downlink propagation separately.NSN supports WCDMA 2100 with RAN1.5.2.ED2, WCDMA 1900 with RAN04 (Node B software WN2.ED2) and WCDMA 850 with RAS05 (Node B software WN3).The UARFCN identifies the RF carrier on a 200 kHz raster. The 200 kHz raster can be used for fine tuning the position of the RF carrier. Operating bands II and IV, V and VI have additional RF carrier positions defined with a different UARFCN numbering scheme.Directed Emergency Call Inter-System Handover (EMISHO) is supported by NSN for WCDMA 1900 and 850. EMISHO allows GSM location based services to be used in American markets where there are stringent location based service requirements for emergency calls.NSNs solution for WCDMA 2100 supports both 20 W and 40 W WPA. NSNs solution for WCDMA 1900 and 850 supports only 40 W WPA.The majority of link budget assumptions are the same for all operating bands. Antenna gains and feeder losses tend to be lower at lower frequencies. Building penetration losses and indoor standard deviations can be assumed to be equal for each of the frequency bands although these assumptions tend to be country specific. The use of 40 W WPA for WCDMA 1900 and 850 means that downlink transmit powers are typically 3 dB greater. MHA may not be used in band V as a result of the reduced feeder loss at 850 MHz.The air-interface propagation loss is less for the lower operating bands. In the case of Okumura-Hata, the frequency dependant terms result in approximately 12 dB difference between the WCDMA 2100 and 850 path loss figures for a specific cell range. Propagation model, clutter dependant correction factors may be assumed to increase at lower frequencies, i.e. for WCDMA 850.

The NSN Flexi WCDMA Base Station will be available for frequencies 2100 MHz, 1700 MHz, 1800 MHz and 1700/2100 MHz in the second half of 2006. In the first half of 2007, further frequencies, including 850 MHz, 900 MHz and 1900 MHz will be available, where after other frequencies will be added based on market need. WCDMA is a wideband Direct-Sequence Code Division Multiple Access (DS-CDMA)system, i.e. user information bits are spread over a wide bandwidth by multiplying theuser data with quasi-random bits (called chips) derived from CDMA spreading codes.

Antenna Hopping (DL Tx Div in GSM)Sween J Ambat2006-09-07*Sween J Ambat2006-09-07*Sween J Ambat2006-09-07*Sween J Ambat2006-09-07*Modulated data is known as Symbol.*The processing gain is calculated as follows: 10*log10128=21db

*Block diagram for digital communcation.Coding scheme voice: AMR , 8 rates(4.75 12.2kbps)CRC attachmentTo check, if error then retransmit.But if just use error checking mechanism, too much retransmission, then reduce total throughput.So, introduce more powerful/effective mechanism, called FEC, by introducing redundant bits.

Channel coding:Purpose: for data protection/error correction1. Convolution coding ( , 1/3 rate). Introduce redundancy bits. For voice & low speed signaling. or Turbo coding (data encoding)2. Interleaving : distribute error over data transmitted3. Rate matching : match symbol rate to that accepted by spreading

Spreading:Spreading : OVSF codesScramblingDifferent codes for different purpose in downlink and uplink.

*AMR rate: bit rate controlled by RNC. As users increases, RNC can dynamically reduces user AMR rate;Depending on air interface load and speech quality on the connection.

CRC attachmentTo check, if error then retransmit.But if just use error checking mechanism, too much retransmission, then reduce total throughput.So, introduce more powerful/effective mechanism, called FEC, by introducing redundant bitsChannel coding:Purpose: for data protection/error correction1. Convolution coding ( , 1/3 rate). Introduce redundancy bits. For voice & low speed signaling. or Turbo coding (data encoding)2. Interleaving : distribute error over data transmitted3. Rate matching : match symbol rate to that accepted by spreading

Spreading:Spreading : OVSF codesScramblingDifferent codes for different purpose in downlink and uplink.

Sween J Ambat2006-09-07**Spreading is applied to the physical channels. It consists of two operations. The first is the channelization operation, which transforms every data symbol into a number of chips, thus increasing the bandwidth of the signal. The number of chips per data symbol is called the Spreading Factor (SF). The second operation is the scrambling operation, where a scrambling code is applied to the spread signal.

If code do not match means less interferance.( Orthogonality advantage)*Auto correlation : multipath components . Correlate a signal with time delay version of itself.If multipath components are a multiple of chips, then can be separated into multipath components, to be combned at RAKE receiver, to produce stronger received signal.Crosscorrelation : multi-access . Differentiate one user from another

Sween J Ambat2006-09-07*Sween J Ambat2006-09-07*Sween J Ambat2006-09-07*SALAF HAYATSween J Ambat2006-09-07*Sween J Ambat2006-09-07*Sween J Ambat2006-09-07*Sween J Ambat2006-09-07*Rb_phy includes DPDCH (User data + L3 control) + Error protection + DPCCH (L1 control)Long scrambling codes created from the Gold pseudo-noise sequence (length of 38 400 chips)Short scrambling codes generated by the quaternary S(2) pseudo-noise sequence (256 chips are periodicaly repeted to get the scrambling code of the frame length)For the common physical channels long scrambling codes must be usedFor the dedicated channels both long and short scrambling codes can be used

In conventional radio technologies (AMPS, TDMA and GSM), the desired signal must be strong enough to override any interference. The figure of quality is the C/I (signal power divided by co-channel interference power).Co-channel users are kept at a safe distance by careful frequency planning to keep interference at low levels. Nearby users and cells must use different frequencies to avoid interference.In W-CDMA all users occupy the same frequency at the same time! W-CDMA interference comes mainly from nearby users (UE and BTS). Each user is a small voice in a roaring crowd, but with a uniquely recoverable code. The figure of quality is the Eb/No (Energy per bit over the interference [noise] spectral density).

At the receiver, as the codes are different and are known, only the power of the intended user is de-spread.After despreading (decoding), correct data recovery requires a given value for the Eb to No ratio. Under this Eb/No ratio the noise will generate too many errors. The noise is mainly generated by the other users transmitting at the same time and at the same frequency but using different spreading codes. Therefore, in order not to cross this maximal noise level, all the users have to share their power: In W-CDMA the Time-Frequency plane is not divided among the mobile subscribers as is done in TDMA or FDMA. So the common shared resource is power.The de-spreading process gives processing gain proportional to the bandwidth of the spreading signal. The larger the spreading factor, the larger the gain. This means that by using a larger spreading factor, we can reduce the power (and therefore the background noise). Thanks to this property, spread signals can operate at negative signal-to-noise ratios provided that they possess enough gain.

Example:The narrow-band signal requires an Eb/No of 12 dB to achieve a certain bit-error rate performance. What is the required Ec/No, knowing that the processing gain is 20 dB?For a given noise level, as the processing gain is smaller for a high rate user data, the acceptable path loss is lower and therefore so is the range of the cell.

The radius of a cell varies with the SF (Spreading Factor) and, as we will see, the noise level or, as a matter of fact, the number of active subscribers in the cell. The figures are given for a traffic load of 50% of the maximum traffic acceptable in the cell.A mobile station or UE is surrounded by BSs (Base Station), all of which transmitting on the same W-CDMA frequency. It must be able to discriminate between the different cells of different base stations and listen to only one set of code channels. Therefore two types of codes are used:ChannelizationThe user data are spread synchronously with different channelization codes. The orthogonality properties of OVSF enable the UE to recover each of its bits without being disturbed by other user channels.ScramblingScrambling is used for base station identification. It reduces the interference with neighboring cells since the same channelization codes are used.It is important to maintain good cross correlation characteristics between the different scrambling codes in order not to decode an interferer.Once allocated to the UEs, these codes, remain the same during the whole communication. Otherwise, the base station must be notified of the change.Similar to the reuse of frequency in GSM, scrambling codes are necessarily reused.The W-CDMA system must be able to uniquely identify each UE that may attempt to communicate with a BS.The different uplink code channels are distinguished by different UE scrambling codes. They may be scrambled by either long or short scrambling codes.Orthogonality from channelization codes is lost because there is no longer synchronous transmission.Nevertheless UE scrambling codes reintroduce some kind of reduced orthogonality thanks to their good cross-correlation properties.Sween J Ambat2006-09-07*Scrambling code work like ciphering.The UTRA/FDD Transmission is a continuous transmission. The Spreading factor has to be chosen so that the transmission is compliant with the UMTS Frame Format.

A slot is equal to 2560 chips. The number of bits per slot is variable and depends on the Spreading Factor.A Radio Frame is equal to 15 slots, or 38.400 chips, during 10 ms. It corresponds to a processing time element.The System Frame Number is a counter used for a time reference in one cell. SFN value is given in the BCH (from 0 to 4095 frames).Sween J Ambat2006-09-07*Sween J Ambat2006-09-07**RSCP received signal code power**Located in BTS & UE.Controls power of dedicated physical channels.

Inner loop power controlThe base station compares the measured Eb/Nt with the corresponding objective and the mobile station will be ordered to decrease the transmission power if the measured Eb/Nt exceeds the objective. Otherwise, the mobile station will be ordered to increase the transmission power. The adjustment frequency is 1500HZ.Outer loop power controlEstimate Eb/Nt objective based on the measured Frame Error Rate(FER) Eb/Nt=bit energy/density of interference power spectrum, similar to signal-to-noise ratio.

*Sween J Ambat2006-09-07*During softer handover, a mobile station is in the overlapping cell coverage area of two adjacent sectors of a base station.The communication between mobile station and base station take place concurrently via two air interface channels, one for each sector separately. This requires the use of two separate scrambling codes in the downlink direction, so that the mobile station can distinguish the signals. The two signals are received in the mobile station by means of Rake processing, very similar to multipath reception, except that the fingers need to generate the respective codes for each sector for the appropriate descrambling and despreading operations.In the uplink direction, a similar process takes place at the base station: the code channel of the mobile station is received in each sector, then routed to the same baseband Rake receiver.During soft handover, a mobile station is in the overlapping cell coverage area of two sectors belonging to different base stations.As in softer handover, the communications between mobile station and base stations take place concurrently via two air interface channels from each base station separately. As in softer handover, both channels (signals) are received at the mobile station by Rake combining. Seen from the mobile station, there are very few differences between softer and soft handover.In the uplink direction, soft handover differs significantly from softer handover: the code channel of the mobile station is received from both base stations, but the received data is routed to the RNC for selection. This is typically done so that the same frame reliability indicator as provided for outer loop power control is used to select the better frame between the two possible candidates within the RNC.When soft handover is used, and when two cells belong to two node Bs, that each belong to two different RNCs, these RNCs have a specific functionality described below:SRNC (Serving RNC)This a role an RNC can take with respect to a specific connection between a UE and the UTRAN. There is one SRNC for each UE that has a connection to UTRAN. The SRNC is in charge of the radio connection between the UE and UTRAN. The SRNC terminates the Iu for this UE.DRNC (Drift RNC)This a role an RNC can take with respect to a specific connection between a UE and the UTRAN. An RNC that supports the SRNC with radio resources when the connection between the UTRAN and the UE needs to use cell(s) controlled by this RNC, is referred to as a drift RNC.HHO also applies to same frequency Inter-RNC HO without IurSween J Ambat2006-09-07****Sween J Ambat2006-09-07*Sween J Ambat2006-09-07*Sween J Ambat2006-09-07*Sween J Ambat2006-09-07*Sween J Ambat2006-09-07*In a multi-path environment, the original transmitted signal is reflected by obstacles such as buildings or mountains, and the receiver has to treat several copies of the signal with different delays. Actually, from each multi-path point of view, other multi- path signals are considered as interference and are partially suppressed after de-spreading thanks to the processing gain. However, a further benefit is obtained if several multi-path signals are combined together using a rake receiver.The rake receiver has multiple fingers (4 to 8), each for a multi-path component. In each finger, the received signal is de-spread by the code which is time aligned with the delay of the multi-path signal. After despreading, the signals are combined using either equal gain or maximum ratio combining. This technique provides a more stable transmission channel.Rake receivers are used in the uplink and the downlink. In addition to multi-path combination the rake receiver is used by the UE to communicate with several cells (macro-diversity). A trade-off has to be made between the multi-path gain and the capacity loss due to the use of multiple channels.