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1 © 2005 Nokia V1-Filename.ppt / yyyy-mm-dd/ Initials

UMTS Radio Path and TransmissionUMTS Radio Path and Transmission




Topics

• Quick review of air interface technologies

• The WCDMA (Air/Uu) interface and its properties• Radio resource management introduction (RRM RNC Functions)

• Briefly about issues related to network planning (optional topic)

• Nokia Smart Radio Concept (optional topic)




Module objectives

After completing this module, the participant should be able to:

• Explain the terms carrier, spreading, power, FDD, cell characteristics,

channelisation code, and scrambling code.

• List and identify the structure of the UMTS air interface. The student should

be capable of following a model and explaining what is happening to data

at every phase in the Uu interface for the UMTS-FDD implementation.

• List and clearly explain the key functions and tasks in radio resource

management (6 functions)




Power (P)

Frequency (f)

Time

Now, imagine if all the users sharedthe same frequency, at the sametime.

Radio path basics (review)

Frequency 2 - Channel 2




FDMA - Frequencies are allocated oneper user.

f1 - Ch 1 f1 - Ch 2 f1 - Ch 3 f1 - Ch 4

f2 - Ch 1 f2 - Ch 2 f2 - Ch 3 f2 - Ch 4

f3 - Ch 1 f3 - Ch 2 f3 - Ch 3 f3 - Ch 4

f4 - Ch 1 f4 - Ch 2 f4 - Ch 3 f4 - Ch 4

TDMA - Several users share the samefrequency, only divided by time.

f

t

How do you determine thedifferent users?

(spreading)codes

By allocating each channel a uniquecode, known as the spreading code.




Basic WCDMA theory (review)

Frequency Band

Spreading Factor

Power

WCDMAOriginating Bit Received Bit

+1

Power

FrequencyBand

FrequencyBand

Power

Power

FrequencyBand




Variable slices are allocated (review)

Frequency

5MHz

Power

Time

Users Separated byCodes

High bit rate user

Low bit rate user



7

©

2 0 0 5 N ok i a

V 1 - F i l e n a m e . p p t / y y y y - mm- d d / I ni t i a l s

J a p a n

I MT -2 0 0 0

PHS

I MT -2 0 0 0

p

(FDD )

UM

1 8 0 0

UMT

(FDD )

U S A

PCSunlicensed

P C S

P C S

UMTS (TDD)IMT-2000 (TDD)

MSa

MSa

MobileSatellite

MobileSatellite

MobileSatellite

MobileSatellite




UMTS-FDD(Frequency Division Duplex)

GuardPeriod

f

t

Uplink

Downlink

Bandwidth 5MHz

Uplink Downlink

Bandwidth 5MHz

Separation 190MHzf

t Bandwidth 5MHz

UMTS-TDD(Time Division Duplex)




Basic WCDMA terminology

5 MHz

3.84 MHz

WCDMA Carrier (in one direction)

F r e q u e n c y

TimeDS = Direct Sequence

CDMA Sequencing Principles




WCDMA frame structure

f

t

Middlepoint of WCDMA Carrier

WCDMA Frame 10 ms

15 slots, each of them 2/3 ms




Air interface structure

Channel Coding

TxRAKE

Signalling Data

Channels

Radio Framing

Spreading &Channelisation

Scrambling

Modulation

Air interface

SMSSMS

define the UE actions

The user data is coded,depending on the

applicationThe specifications

1Different channels carry

different information

2

Data is coded, framed,

spread and channelised

The signal is now

scrambled

3

The signal is modulatedon a frequency torepresent binary values4

The UE uses a special

receiver to RAKE throughthe air interface

5




Simplified

structureof airinterface

Channel Coding

TxRAKEAir Interface

Signalling Data

Call set-up,SMS, etc.messages

Voice, videoand other user

data

Channels

Radio Framing


Scrambling

Modulation




Channel coding, rate matching

• 1/2 and 1/3 rate convolutional channel coding and

turbo coding will be implemented.

• Rate matching is used to "fit" the data bit rate so that it

corresponds to the pre-defined fixed bit rates of theair interface. Also puncturing can be used.

Rate

Matching- Convolutional coding

- Interleaving

Baseband data (n kb/s)

- 30 kb/s

- 60 kb/s

- 120 kb/s

- 240 kb/s- 480 kb/s

- 960 kb/s




Simplified

structureof airinterface

Channel Coding

TxRAKEAir Interface

Signalling Data

Call set-up,SMS, etc.messages

Voice, videoand other user

data

Channels

Radio Framing


Scrambling

Modulation




Channelisation and scrambling

SF=1 SF=2 SF=4

ch,1,0=(1)

ch,2,0=(1,1)

ch,2,1=(1,-1)

ch,4,0=(1,1, 1,1)

ch,4,1 =(1,1,-1,-1)

ch,4,2 =(1,-1,1,-1)

ch,4,3 =(1,-1,-1,1)

Data (Baseband, Channel Coded & Rate-Matched)

Spread and Combined with Channelisation Code

Data is Spread...

…by a certain factor. The channelisation codeis selected based upon how much the data is

spread

Data

Channelisation Code Scrambling Code

Downlink Example

Bit rate Chip rate Chip rate




Channelisation code tree

SF = 1 SF = 2 SF = 4

ch,1,0 = (1)

ch,2,0 = (1,1)

ch,2,1 = (1,-1)

ch,4,0 = (1,1,1,1)

ch,4,1 = (1,1,-1,-1)

ch,4,2 = (1,-1,1,-1)

ch,4,3 = (1,-1,-1,1)




Code

-1

Data xCode

Code

Data

+1

+1

+1

+1

+1

-1

-1

-1

-1

ChipChip

DespreadingDespreadingUu

WCDMA terminology - Chips & SymbolsSymbols (In this drawing, 1 Symbol = 8 Chips)

Rate

matchedbaseband

Data

Scrambling




Spreading Factor = Processing Gain

Factor Spreading Rate Bit Bearer

RateChipSystem

B

BG

Bearer

Uu p ===




Where are codes used?

In the Uplink (UE → BTS),the user's data and

signalling information isseparated by

Channelisation Codes

datasignalling

In the Downlink (BTS→UE),cells are seperated byScrambling Codes

In the Uplink (UE → BTS),terminals are separated by

Scrambling Codes

In the Downlink (BTS → UE),user connections are separated

by Channelisation Codes

Dedicated User Channel

Channel Coding

TxRAKEAir interface

Signalling Data

Call set-up,SMSetc.messages

Voice,videoandotheruser data

Channels

Radio Framing

Spreading &

Channelisation

Scrambling

Modulation




Channelisation and scrambling codes

Ch annelisation code Scrambling cod e

Usage Uplink: Separation of physical data andcontrol channels from the same terminal

Downlink: Separation of downlinkdedicated user channels

Uplink: Separation of terminals

Downlink: Separation of sectors (cell)

Length Variable (depends on the user allocation) Fixed

Numberof codes

Depends on the spreading factor (SF) Uplink: Several millions

Downlink: 512




Modulation

Bit combinations in Radio Path:

'10'

135°

'00'

45°

'11'

225°

'01'

315°

Rx

TxQPSK

QPSK

BTSUE

DataData




Channel Organisation in UMTSUE

Node BRNC

Logical channelscontent is organised in separate channels, e.g.

user data, paging information, radio link control information

Transport channelslogical channel information has to be organised (e.g. in time)

before it is physically transmitted

Physical channels

(frequency band &spreading code)

Frames

transmission organisedbased via the Iubinterface




Downlink Uplink

LogicalChannels

Channels DS-WCDMA-FDD

BCCH PCCH DCCH DTCH CCCH DTCH DCCH

TransportChannels

BCH PCH DCH DCHRACH CPCH

PhysicalChannels

CCPCH-1 CCPCH-2 PRACH DPDCH DPCCH

CCCH CTCH

FACH DSCH

PDSCH PCPCHDPCH(DPDCH+DPCCH)

CCPCH-1 : Primary Common Control Physical Channel

CCPCH-2 : Secondary Common Control Physical Channel

DPDCH/DPCCH : Dedicated Physical Data/Control Channel

PDSCH : Physical Downlink Shared Channel

PRACH : Physical Random Access Channel

PCPCH : Physical Common Packet Channel




Downlink

LogicalChannels

Channels DS-WCDMA-FDD

TransportChannels

PhysicalChannels

SCH CPICH PICHAICH

SCH : Synchronisation Channel

CPICH : Common Pilot ChannelAICH : Acquisition Indication Channel

PICH : Paging Indication Channel

No Logical andTransport Channels




FDD-mode: Logical and Transport Channel DL

BCCH

Broadcast Control Channel,(system information)

PCCHPaging Control Channel(paging & notification)

CCCHCommon Control Channel(control information withoutRRC connection)

DCCHDedicated Control Channel(power control, TFI, etc.)

DTCHDedicated Traffic Channel(user data)

Logical Channels (content)

BCH

Broadcast Channel,

PCHPaging Channel

FACHForward Access Channel

DSCHDownlink Shared Channel

DCHDedicated Channel

Transport Channels

dedicated

transportchannels

commontransportchannels




FDD-mode: Logical and Transport Channel UL

CCCH

Common Control Channel(control information withoutRRC connection)

DCCHDedicated Control Channel(power control, TFI, etc.)

DTCHDedicated Traffic Channel(user data)

Logical Channels (content)

RACH

Random AccessChannel

CPCHCommon Packet Channel

DCHDedicated Channel

Transport Channels

dedicatedtransportchannels

commontransportchannels




FDD-mode: Physical Channel DL

how to getsynchronised

?

SCH-1Primary Synchronisation Channel(chip & timeslot synchronisation)

SCH-2Secondary Synchronisation Channel(frame and scrambling class synchronisation)

CPICHCommon Pilot Channel(for power measurement and scramblingcode determination; channelisation code

is CCH,256,0)

Node B

RNC




Scrambling Code group into Code sets

Primary Scrambling Code

Secondary Scrambling Code #1



Channelisation Code Set (256 Codes)




Primary Scrambling Code








- 512 Code Sets x 16 Scrambling Codes = 8192 Codes numbered from 0 ... 8191 available




FDD-mode: Physical Channel DL

how to getsystem

information?

Node B

CCPCH-1Primary Common Control Physical Channel(UE knows scrambling code from CPICH,channelisation code always CCH,256,1,system information)

CCPCH-2Secondary Common Control Physical Channel(for paging and notification; channelisationcode delivered as system information)

BCCH

RNC

BCH

PCCH PCH

CCCH

DCCH

DTCH

FACH




FDD-mode: Physical Channel

how to makethe firstcontact?

Node B

RNC

P RA C H Pre am b le

P RA C H Pre am b l

e

P RA C H Me s s age P

ar t

AI C H

CCCH RACHDCCHDTCH

PRACHPhysical RandomAccess Channel

AICHAcquisition IndicationChannel




Example of channel usage

UplinkDownlink

LogicalChannels

TransportChannels

PhysicalChannels

SCH BCCH PCCH CCCH DCCH DTCH CCCH DTCH DCCH

SCH BCH PCH FACH DCH DCHRACH CPCH

SCH1/2CCPCH-1 CCPCH-2 DPCH(DPDCH+DPCCH)

PRACH DPDCH DPCCH PCPCH

CTCH

Signalling to Terminal

User Data to Terminal

SMSSMS

Signalling to Network

User Data to Network

DSCH

PDSCH




Receiving signals at the UE

UE listening toseveral BTS's

Attached BTSPath of user




Simplified diagram of the RAKE Receiver

D e

l a yCode used

for theconnection

Rx

Output

Finger

t

Cell-x

Cell-x

Cell-x

Cell-y

Rx

Rx

Rx

Finger

Finger

Finger

D e

l a y

D e

l a y




Radio Resource Control (RRC) states

Idlemode

Connected Mode

Cell DCH

URA PCH

Cell PCH

Cell FACH




Management of channels in RRC

RLC RLC RLC

RRCsignalling

CS RAB(speech)

PS RAB(data)

MAC

L1

Iub/IurMAC forCommonChannels

• Segmentation• Retransmission across the air• Ciphering of NRT data• Buffering

Iu

2. Transport channels

3. Physical Channel(s) (Radio)

1. Logical Channels

RLC: Radio Link Control

MAC: Medium Access Control

• Selection of the data to be insertedin the Radio Frame

• Selection of common or dedicated channels• Multiplexing of logical channels into

same transport channels• Ciphering for RT




Radio Resource Management

Iub Iu

Iur

In

te

rface

Un

its

In

te

rface

Un

its

(Wideband)Switching

ControlUnits

Radio

Resource

Management

O&MInterface

to/from Network

Management

to/fromotherRNCs

to/fromCore

Network

to/fromthe BSs



37 © 2005 Nokia V1-Filename.ppt/ yyyy-mm-dd/ Initials

Radio Resource Management

• It is responsible for utilisation of the air interface

• It is needed to guarantee QoS, to maintain the planned coverage area andto offer high capacity.

• Management of Traffic

Network Based function

(Cell Resource Management)

• Load Control (LC)

• Admission Control (AC)

• Packet Scheduler (PS)

• Resource Manager (RM)

Connection Based function

• Power Control (PC)

• Handover Control (HC) PC

HC connectionbasedfunctions

LC

AC networkbasedfunctions

PS

RM

PC

HC connectionbasedfunctions

LC

AC networkbasedfunctions

PS

RM

Trainer comment

•The RRM deals with means of establishing, maintaining, balancing, modifying, and releasing the basic

means of communication on the radio interface and through the RAN.

•It provides procedures during system information broadcasting, connection establishment, connected

session, and connection release session.

•It is needed to guarantee QoS, to maintain the planned coverage area and to offer high capacity.

•In addition, the RRM performs actions to prevent the overloading of the radio network according to the

interference measurements.

•To be more specific, we can list the following functions:

⇒ Cell resource management functions (LC, AC, PS, RM)

⇒ HC and PC




RRM Function in Brief

1. Admission Control• Admit or reject request of Radio Access Bearer (RAB)

2. Load Control• Ensure the system is not overloaded and remains stable

3. Packet Scheduler• Ensure availability of air interface and select Transport Channel for packet

data

4. Power Control• Keep interference level minimum and maintain QoS

5. Resource Manager• Code management for Channelisation code and Scrambling code

6. Handover Control• Handover action




1. Admission Control (AC)

Radio Access Bearersin Uu Interface

U u I n t e r f a

c e B a n

d w i d t h

SIR - Allowed RangeAdmission Control

Interference Margin (dB) and Load Factor

0

5

10

15

20

25

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Load Factor

I n t e r f e r e n c e M a r g i n ( d B )

−

⋅=

Factor Load Log I

_1

110

Admit or reject request of Radio Access Bearer (RAB)




TRHO_threshold

Prx_target

Prx_target_BS

UL interference power

Load

Planned load area

Marginal load area

planned uplinkinterference power

Defines the limit (the first UL overload threshold) for theUL interference power, after which the BTSBTS starts its loadcontrol actions to prevent overload.

Prx_offset

Uplink Admission Control

Prx_target defines the optimal operating point of the cell interfernce power, up to which theAdmission Control of the RNC can operate.




• The purpose of load control is to optimise the capacity of a cell andprevent overload situation.

• Load control consists of Admission Control (AC) and Packet Scheduler(PS) algorithms, and Load Control (LC), which updates the load status of

the cell based on resource measurements and estimations provided by

AC and PS.

LC

AC

PSNRT load

Load changeinfo

Load status

2. Load Control (LC)




The restriction of CDMA system is interference

The more transmission poweris required to achieve certainquality

The further awayusers are connected

The more usersthat are connected

Finally the capacity is filled




• The traffic can be divided into two groups:

Real Time (RT) and Non-Real Time (NRT).

• Thus some slide of capacity must be reserved for the RT traffic for mobilitypurposes all the time. The proportion between RT and NRT traffic varies allthe time.

Capacity

Time

Overload

Load Target

Overload Margin

P o w e r

Estimated capacity forNRT traffic.

Measured load causedby non-controllable load




Load Control Description

• Load Control's (LC) task is to make sure that the system is not overloaded

and remains stable.

• LC can be divided into two functions:

1. Preventive control = Guards the system from overload.

2. Overload control = Returns the system from a overload state to normalstate in a fast and controlled way.

• Since interference is the main resource criteria for CDMA, the load controlmeasures:

• UL total received wideband interference power

• DL total transmission power

• Periodically under one RNC on cell basis.

• Radio Resource Manager (RRM) acts according to these measurements andparameters set by Radio Network Planning.




Relation of AC, PS and LC

Load

Power

Threshold

Offset

Target

Packet ScheduleLoad ControlAdmissionControl

No ActionAdmits RT

normally

Increase amount

of NRT bearer

No ActionNot admitsnew bearer

Not IncreaseNRT bearer

Not admitsnew bearer

Loadpreventive

Decrease NRTbit rate

Overloadaction

Decrease NRTbit rate and Drop

How does the packet scheduling work during a soft handover? Let us assume that there are three cellsin the active set. There is now one UE specific part, but three cell specific PSs interacting with eachother. The scheduling procedure is mostly the same as in the single cell case, except that now all threecell specific parts generate independent responses to the capacity request from the UE specific PS. Inthis case the lowest scheduled bit rate of the three is selected. This may require the downlink spreadingcodes to be reallocated in some cells in the active set; and, for this purpose, an additional request-response round is needed. A key point to remember here is that cell specific parts of the PS function asindependent entities.




• Ensure availability of Air Interface capacity for all packet data users

• Select which transport channel is used for the packet data transmission

• ( I.e. Common Ch, Dedicated Ch, Shared Ch, Common Packet Ch)

3. Packet Scheduler (PS)

time

packet service session

packet call

reading time

packet size packet arrival interval




4. Power control (PC)

Open Loop Power Control (Initial Access)

Closed Loop Power Control

Outer Loop Power Control

BTS RNC

Without Power Control system,Cell capacity will decrease.

1. UL Open loop PC ( For Initial Tx power of UE)

2. Fast closed loop PC (DCH; DL →UE, UL →BTS)

3. Outer loop PC (DCH; DL →UE, UL →RNC)




UL Outer Loop PC during Soft Handover




CELL 1 CELL 3CELL 2

1. Scrambling codes

2. Channelisation codes

full code set / cell

SUBS2SUBS1

5. Resource Management (RM)

Assign UL Code

to UE

Cell ID

allocated by

O&M

Scrambling

Code

Assign UL Code

to UE

- Allocate Code

- Re-arrange of

the code tree

Channelisation

Code

UplinkDownlink

Code Management




Tree of Channelisation Code in downlink

• Hierarchical selection of short codes from a "code tree" to maintain

orthogonality.

• Several long scrambling codes can be used within one sector to avoidshortage of short codes.

C1(0) = [ 1 ]

C2(0) = [ 1 1 ]

C2(1) = [ 1 0 ]

C4(0) = [ 1 1 1 1 ]

C4(1) = [ 1 1 0 0 ]

C4(2) = [ 1 0 1 0 ]

C4(3) = [ 1 0 0 1 ]

C8(0) = [ 1 1 1 1 1 1 1 1 ]

C8(1) = [ 1 1 1 1 0 0 0 0 ]

. . .

. . .

Spreading factor:

SF = 1 SF = 2 SF = 4 SF = 8

C8(2) = [ 1 1 0 0 1 1 0 0 ]

C8(3) = [ 1 1 0 0 0 0 1 1]

. . .

. . .

C8(4) = [ 1 0 1 0 1 0 1 0 ]

C8(5) = [ 1 0 1 0 0 1 0 1 ]

. . .

. . .

C8(6) = [ 1 0 0 1 1 0 0 1 ]

C8(7) = [ 1 0 0 1 0 1 1 0 ]

. . .

. . .

Example of code allocation




6. Handover Control (HC)

Soft Handover

4

Hard/Inter-Frequency Handover

Softer Handover

Inter-SystemHandover

BTSBTS

Frequency f1

Frequency f1

BTSBTS

Frequency f1 Frequency f2

BTSBTS

WCDMA GSM900/1800

BTSSector 1

f1

Sector 2

f1

Sector 3f1

Multipath Signal

through Sector 1

Multipath Signal through Sector 3

BTSBTS

Frequency f1

Frequency f1

RNC RNCIur

Iu b Iub




Handover types

CNRNC

MSCBSC

GSM900/1800GSM900/1800

WCDMA FDDWCDMA FDD

Inter-SystemInter-System

Intra-SystemIntra-System

WCDMA TDDWCDMA TDD

Inter-SystemInter-System




Active Set and Soft Handovers

CNRNC

f r a m e r e l i a b i l i t y i n f o

f ra m e r e l ia b i l

i t y i n f o

frameselection / duplication

BS1 BS2

Soft handover window

P2) Add BS2

1) Connection to BS1

3) Drop BS1

4) Connection to BS2

Active Set is list of cell(s) that UEhas connection to network.Maximum 3 cells / active set




Handover control

MeasurementReports

Handover

Algorithm:

Criteria fulfilled?

- Activate new BTS

- Update Active Set

Measurement Phase

Decision Phase

Execution Phase

- Signal Strength

- Quality

- Interference

YES

NO

Created & collectedby the UE and the BTS

Investigated by the RNC

Commanded by the RNC,

performed by the UE

Procedure: Functional Split:




Iur-Interface & Soft HandoverCN (Core Network)

circuit switched (cs)

domain

packetswitched (ps) domain

3GMSC/VLR

3GSGSN

UTRAN

RNC

Node B

Node B

RNC Radio Network ControllerUE User Equipment = Mobile Equipment (ME) + UMTS SIM (USIM)

RNC

Node B

Node B(RNS)

Radio Network Subsystem (RNS)

Iub

Iub

Iur

Iu-PS

Iu-CS

Uu

Uu

UE

I can beconnected toseveral cells

simultaneously

Duplication of DL traffic,selection of UL traffic




Micro Diversity Combining

BTS Receiver (RAKE)

Same signal propagating different ways in the Radio Path

Summed signal

Uplink Direction (Micro) Diversity Point

Sum up of received signals at BTS by RAKE receiver

BTS




Macro Diversity Combining (MDC)

BTS

BTS

BTS

RNC

RNC

Macro Diversity Point

CoreNetwork

Active

Set RNC evaluates the frames from all BTSsand choose the best one send to CN

RNC




GSM BCCH or SACHH

System information

GSM SACHH Measurement Report

Resource Reservation

Resource Reservation acknowledge and Handover command

GSM DCCH Inter-system Handover command

DCCH/DCH Handover to UTRAN complete

Node B

GSM900/1800 GSM900/1800

Intersystem handover from GSM

UE GSM BSS MSC UTRAN

Release resources




Node B

BCCH system information or

DCCH measurement control

DCCH/DCH measurement report

Resource Reservation

Resource Reservation acknowledge and Handover command

DCCH Inter-system Handover command

GSM DCCH Handover Access

GSM900/1800 GSM900/1800

Intersystem handover from UTRAN

UE GSM BSSMSCUTRAN

Release resources

RNC




Differences between WCDMA and GSM

WCDMA GSM

Carrier spacing 5 M Hz 200 kHz

Frequency reuse factor 1 1–18

Power controlfrequency

1500 Hz 2 Hz or lower

Quality control Radio resourcemanagement algorithms

Network planning(frequency planning)

F req uen cy d ive rsity 5 M Hz ba nd wid th giv esmultipath diversity with

Rake receiver

Frequency hopping

Packet data Load-based packetscheduling

Time slot basedscheduling with GPRS

Downlink transmitdiversity

Supported forimproving downlink

capacity

Not supported by thestandard, but can be

applied

High bit rates

Spectralefficiency

Different qualityrequirements

Efficientpacket data

Downlinkcapacity




UMTS & GSM network planning (Optional Topic)

GSM900/1800: 3G (WCDMA):




Characteristic of a cell

Dedicated Channels

Common Channels

Coverage and capacity are related.

The more capacity used, the cellshrinks. This is known as cellbreathing.

Cell Breathingis phenomenon of cellshrink when morecapacity is apply tothe cell




Coverage & Capacity

f1

128 kbps

64 kbps

8 kbps

f1

144 kbps

64 kbps

64 kbps

144 kbps

'Cell breathing'

The size of cell variesaccording the traffic load

High load 800 kbps→→→→ smaller coverage

Low load 200 kbps-> large coverage

144 kbps

64 kbps

64 kbps

• Load factor directly corresponds to the supported traffic per cell.• More traffic means more interference →→→→ cell breathing




Area type Dense

Urban

Urban Suburb Rural

Speech 92 93 95 95 %

144 kb/s NRT 85 85 85 85 %

GSM1800 speech 85 85 85 85 %Cell range 1 1.6 2.3 5.2 km

Factors affecting cell size include:

Frequency band - 2000MHz muchhigher than GSM networks.

Traffic types - WCDMA user datarates drop off as the user movesfurther away from the Node B

User levels - Demand for mobileservices will increase, leading to muchgreater user densities

Fast DataUsers

Voice andSlow Data

Users

average projected coverage

WCDMA Cell Coverage




Processing gain

Frequency (Hz)

Voice user (12,2 kbit/s)

Packet data user (384 kbit/s)

P o w e r d e n s i t y ( W / H z )

W

R

Frequency (Hz)

Unspread narrowband signal

Spread wideband signal

Processing GainG=W/R=25 dB

P o w e r d e n s i t y ( W / H z )

W

R

Unspread"narrowband"signal

Spread wideband signal

Processing GainG=W/R=10 dB

• Spreading sequences of different length

• Processing gain is dependenton the user data rate

(User data rate) x(spreading ratio)=

const.=W=3,84 Mcps




Different UMTS cells and BTS

F1

F2

F2

F3

F3

F3

Micro BTSMacro BTS

Pico BTSs

1 - 10 km

50 - 100 m200 - 500 m




Power control in network planning(Near-Far example)

SBS

MS1

MS2

If the power of MS1 is not properly controlledit will jam the weaker signal of MS2.




Physical layer bit rates (Downlink)

Spreading

factor

Channel

symbolrate

(ksps)

Channel

bit rate(kbps)

DPDCH

channel bitrate range

(kbps)

Maximum user

data rate with ½-rate coding(approx.)

512 7.5 15 3–6 1–3 kbps

256 15 30 12–24 6–12 kbps

128 30 60 42–51 20–24 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

parallelcodes

2880 5760 5616 2.3 Mbps

• The number of orthogonal channelisation codes = Spreading factor• The maximum throughput with 1 scrambling code ~2.5 Mbps or ~100 full rate speech users

Half rate speech

Full rate speech

128 kbps

384 kbps

2 Mbps




Uplink coverage of different bit rates




RNC capacity planning

BS Speech Traffic:

Kbit/s /Cell & Code Channel Amount

BS Data Traffic:Kbit/s /Cell & Code Channel Amount

Packet Switched Traffic:

Kbit/s

Circuit Switched Traffic:

Erlangs [Kbit/s]

Concentration

RNC




Smart Radio Concept (SRC)

• Beam steering: optimal baseband combining of 4

uplink signals forms the beam

• can utilise both space and polarisation diversity

• estimated uplink improvement is 6 dB comparedto single antenna operation

WCDMA

ReceiverCombinedreceived

signal




Increase uplink coverage by SRC

Coverage

Capacity

Uplink

Downlink Estimated average gain2.5-3.5 dB compared to2-way diversity

UPLINK relate to Coverage

Parameters :

Uplink:

• Bit rate 144 kbps

• Eb/N0 = 1.5 dB

• Base station noise figure = 4.0 dB

• i=0.65 (3-sector macro)

• Antenna gain 18.0 DBE

• No cable loss = MHA used

• Fast fading margin = 4.0 dB + Soft handover gain = 2.0 dB

• 30% loading -> Interference margin = 1.5 dB

• Max. path loss = 154.4 dB with SRC and 156.9 dB with SRC

Downlink

• Eb/N0 = 5.5 dB

• Mobile station noise figure = 8.0 dB

• i=0.65• Orthogonality = 0.60

• Base station antenna gain 18.0 DBE

• Mobile antenna gain 2.0 DBE

• Cable loss = 4.0 dB

• Max./average path loss = 6 dB

• Soft handover overhead = 40%, Soft handover gain = 2.5 dB




Using downlink diversity

Open loop Closed loop

Feedback used forphasing transmittedsignals→ beam steering

No feedback,time switchedtransmission

Parameters :

Uplink:

• Bit rate 144 kbps

• Eb/N0 = 1.5 dB

• Base station noise figure = 4.0 dB

• i=0.65 (3-sector macro)

• Antenna gain 18.0 DBE

• No cable loss = MHA used

• Fast fading margin = 4.0 dB + Soft handover gain = 2.0 dB

• 30% loading -> Interference margin = 1.5 dB

• Max. path loss = 154.4 dB with SRC and 156.9 dB with SRC

Downlink

• Eb/N0 = 5.5 dB

• Mobile station noise figure = 8.0 dB

• i=0.65• Orthogonality = 0.60

• Base station antenna gain 18.0 DBE

• Mobile antenna gain 2.0 DBE

• Cable loss = 4.0 dB

• Max./average path loss = 6 dB

• Soft handover overhead = 40%, Soft handover gain = 2.5 dB




Estimated achieved gain

Coverage

Capacity

Uplink

Downlink Estimated capacity gainas high as 75%

DOWNLINK relate to Capacity




3G-UMTS Radio Path & Transmission Key Points 1

• UMTS FDD & TDD

• WCDMA Carrier 5 MHz (3,84 MHz)

• Direct Sequencing

• Codes: Channelisation Code:

—Spreading

—Separation of user connections

Scrambling Code:

—Separation of users (UL)

—Separation of cells (DL)

• SF= Spreading Factor

• If SF=low => Bit Rate=high + Power=high

• If SF=high => Bit Rate=low + Power=low

• 3 layers of channels: Logical, Transport & Physical




3G-UMTS Radio Path & Transmission Key Points 2

• Receiver in UE and BS: Antimultipath RAKE receiver

• Radio Resource Management in RNC:

• Packet Scheduler => For NRT traffic

• Admission Control => Load target

• Power Control => Open Loop, Closed Loop & Outer Loop

• Load Control => Load target, Interference level

• Resource Management =>Code Allocation

• Handover Control and Macro Diversity

=> Soft, Softer, Hard & Inter System

• Cell Breathing:

• Cell capacity and coverage are related.




3G/UMTS Radio Path &Transmission

Review Questions




1. In UMTS, there are two methods used for transport through the air interface.

The first is UMTS-FDD. What is the second one?

a. TDD, Time Doubled Division

b. CDD, Code Division Duplex

c. TDD, Time Division Duplex

d. CDD, Code Divided Data

2. Which of the following sentences best describes the phenomenon called cellbreathing?

a. When more capacity is used, the cell spreads in size.

b. When more capacity is used, the cell shrinks in size.

c. The cell will adjust its size in line with the furthest users. For example, if the user is

5 km away, the cell is 5 km. If the user is 2 km away, the cell is 2 km.

d. Cell breathing is the height of the cell: from 2 - 3 km towards the atmosphere.

Review (1/8)




3. There are two types of codes used in WCDMA. These are the channelisation

and scrambling codes. Why are the scrambling codes used?

a. To separate downlink physical channels in a cell.

b. To separate user data and signalling in the network.

c. As security to check if the User Equipment (UE) is not stolen.

d. To separate different cells in the downlink direction.

4. In UMTS, there are three layers of channels (logical, transport and physical).Which of the following is not a physical channel?

a. BCCH

b. CCPCH

c. DPCH

d. DPDCH

Review (2/8)




5. Which of the following statements about channelisation is true?

a. The lower the bit rate, the more data can be spread.

b. Before spreading, an error-protection code needs to be added to the

baseband data to ensure a safe path through the air interface.

c. The channelisation code is added as part of the spreading function.

d. The channelisation code depends on the spreading factor used.

e. All of the above.

6. What type of modulation is used in UMTS?

a. GMSK

b. QPSK

c. 8PSK

d. BPSK

Review (3/8)




7. For which of following tasks is the RAKE receiver not responsible?

a. Multipath Propagation Delay

b. Listening to surrounding BTSs

c. Channel coding

d. Speech coding

8. Which of the following is a true statement about Admission Control?

a. The UEs handle resource allocation.

b. The RNC makes the decision of resource allocation, based uponinterference.

c. The RNC will not limit the number of the users on a cell.

d. As more users are allocated a code, the load on a cell remains the same.

Review (4/8)




9. The RNC is responsible for the allocation of codes. Which of the following

sentences (only one) is true?

a. Each cell has a scrambling code that acts like a cell ID.

b. Channelisation codes are dependent upon the subscribers' identity.

c. Scrambling codes are generated randomly.

d. Scrambling codes are used in channelisation.

10. When a mobile is in idle mode, which of the following power controls

is used?

a. Closed loop power control

b. Outer loop power control

c. Internal loop power control

d. Open loop power control

Review (5/8)




Review (6/8)

11. Select the right handover type.

1. Soft 2. Softer 3. Hard

4. Inter-system 5. Not possible

a. Sector 1 to Sector 2 (same BTS)

b. BTS x to BTS y

c. RNC to RNC with Iur interface

d. RNC to RNC with no Iur interface

e. UMTS-FDD to UMTS-TDD

f. WCDMA to GSM

g. WCDMA to IS-95

2

1

1

3

4

4

5






14. Which of the following sentences is true about WCDMA radio network

planning?

a. Capacity is linked to the number of time slots.

b. Power should be as high as possible to ensure good quality.

c. Coverage and capacity are linked.

d. The size of a cell remains constant.

15. When planning the Iub Interface in UMTS, which of the following

sentences true?

a. Cellular transmission is based upon ATM.

b. GSM and UMTS sites cannot be co-located.

c. Radio links cannot be used to connect BTS together.

d. It is easy to plan the capacity requirements.

Review (8/8)

Date post:	14-Apr-2018
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