03 umts radio path and transmissionnew

1 © NOKIA

UMTS Radio Path and UMTS Radio Path and TransmissionTransmission

2 © NOKIA

Topics

• Quick review of air interface technologies (optional topic)

• The WCDMA (Air/Uu) interface and its properties

• Radio resource management introduction

• Appendix: Overview of UMTS-TDD solution (optional topic)

• Appendix: Low Chip rate TDD mode (TD-SCDMA, optional topic)

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

3 © NOKIA

Module objectivesAfter 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. These are admission, code, power, handover, and diversity control.

without using any references if not otherwise stated).

4 © NOKIA

Power (P)

Frequency (f)

Time

Now, image if all the users shared the same frequency, at the same time.

Radio path basics (review)

Frequency 2 - Channel 2




FDMA - Frequencies are allocated one per 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 same frequency, only divided by time.

f

t

How do you determine the different users?

(spreading) codes

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

What is the W in WCDMA?There is no limit - Its origin is from that the European & Japanese interfaces have a higher bandwidth than their US CDMA counterpart!

5 © NOKIA

Basic WCDMA theory (review)

FrequencyBand

duration(Spreading

Factor)

Power

WCDMAOriginating Bit Received Bit

6 © NOKIA

Variable slices are allocated (review)

Frequency

5MHz

Power

Time

Users Separated byCodes

High bit rate user

Low bit rate user

7 © NOKIA

IMT-2000 frequency allocations

2200 MHz20001900 1950 2050 2100 21501850

JapanIMT-2000

PH

S

IMT-2000

ITU

Mob

ile

Sate

llit

eIMT-2000 IMT-2000

EuropeUMTS(FDD)DEC

T

UM

TS

(T

DD

)

GSM1800 U

MTS

(T

DD

)

UMTS(FDD)

USA

PC

S

un

licen

sed

PCSPCS

UM

TS

(T

DD

)IM

T-2

00

0

(TD

D)

Mob

ile

Sate

llit

e

Mob

ile

Sate

llit

e

Mob

ile

Sate

llit

e

Mob

ile

Sate

llit

e

Mob

ile

Sate

llit

e

Mob

ile

Sate

llit

e

Mob

ile

Sate

llit

e

8 © NOKIA

UMTS-FDD and -TDD modes

GuardPeriod

f

t

Uplink

Downlink

Bandwidth 5MHz

Uplink Downlink

Bandwidth 5MHz

Separation 190MHzf

t Bandwidth 5MHz

9 © NOKIA

Air interface structure

Channel Coding

TxRAKE

Signalling Data

Channels

Radio Framing

Spreading &Channelisation

Scrambling

Modulation

Air interface

SMSSMSdefine the UE actions

The user data is coded,depending on the

applicationThe specifications

1Different channels carrydifferent information

2

Data is coded, framed,spread and channelised

The signal is nowscrambled

3

The signal is modulated on a frequency torepresent binary values4

The UE uses a specialreceiver to RAKE through

the air interface

5

11 © NOKIA

Modulation

Bit combinations in Radio Path:

'10'135°

'00'45°

'11'225°

'01'315°

Rx

TxQPSK

OQPSK

Node BUE

DataData

12 © NOKIA

Basic WCDMA terminology

5 MHz

3.84 M Hz

f

WCDMA Carrier (in one direction)

Freq

uenc

y

TimeDS = Direct Sequence

CDMA Sequencing Principles

13 © NOKIA

WCDMA frame structure

T y p e U n i t O r D e p a r t m e n t H e r eT y p e Y o u r N a m e H e r e

f

t

M i d d l e p o i n t o fW C D M A C a r r i e r

W C D M A F r a m e 1 0 m s

1 5 s l o t s , e a c h o f t h e m 2 / 3 m s

14 © NOKIA

Channelisation and scrambling codes

DOCUMENTTYPE 1 (1)

TypeUnitOrDepartmentHereTypeYourNameHere TypeDateHere

Channelisation code Scrambling code

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

15 © NOKIA

Where are codes used?

In the Uplink (UE Node B), the user's data and signalling

information is separated by

Channelisation Codes

datasignalling

In the Downlink (Node BUE), cells are

seperated by Scrambling CodesIn the Uplink (UE Node

B), terminals are separated by

Scrambling Codes

In the Downlink (Node B UE), user connections are

separated by Channelisation Codes

Dedicated User Channel

Channel Coding

TxRAKEAir interface

Signalling Data

Call set-up,SMS etc.messages

Voice, videoand other user data

Channels

Radio Framing

Spreading &Channelisation

Scrambling

Modulation

16 © NOKIA

Code

-1

Data xCode

Code

Data

+1

+1

+1

+1

+1

-1

-1

-1

-1

ChipChip

DespreadiDespreadingng

Uu

WCDMA terminology - Chips & SymbolsBits (In this drawing, 1 bit = 8 Chips)

Rate matched baseband Data

Scrambling

17 © NOKIA

Spreading

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

18 © NOKIA

Channelisation and scramblingRate

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

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

19 © NOKIA

Spreading Factor = Processing Gain

B

BG

Bearer

Uup

FactorSpreadingRateSymbolBearer

RateChipSystem

20 © NOKIA

Code sets

Prim ary Scram bling Code

Secondary Scram bling C ode #1



C hann elisatio n C od e S et (25 6 C od es)




Prim ary Scram bling Code








- 5 1 2 C o d e S ets x 1 6 S c ra m b lin g C o d es = 81 9 2 C o d es n u m b e re d fro m 0 ... 81 9 1 a va ilab le

21 © NOKIA

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)

22 © NOKIA

Receiving signals at the UE

UE listening toseveral Node Bs

Attached Node BPath of user

23 © NOKIA

Simplified diagram of the RAKE Receiver

Del

ay

Code usedfor the

connection

Rx

Output

Finger

t

Cell-x

Cell-x

Cell-x

Cell-y

Rx

Rx

Rx

Finger

Finger

Finger

Del

ay

Del

ay

24 © NOKIA

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

RateMatching

- 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

25 © NOKIA

Channel Organisation in UMTSUE

Node B RNC

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)

Framestransmission organised

based via the Iub interface

26 © NOKIA

The dedicated user traffic for one user service in the downlink direction is sent through the Dedicated Traffic Channel.

DS-WCDMA-FDD = Direct Sequencing, WCDMA Frequency Division Duplex. Suitable for outdoor use, and will be the first implementation in 3G. In the Case of DS, data is spread over the band as a function of time.

In the DS-WCDMA-FDD model, there are 3 layers. The first and top-most layer are the logical channels, which carry specific information per channel.

DS-WCDMA-FDD Channels

The network must inform the UE about the radio environment, the information consists of codes, power levels, neighboring information and etc.. The information for the UE is carried in the Broadcast Control Channel.

When there is need to reach the mobile station, the network pages the UE on the Paging Control Channel.

All common actions that the network must perform for all UE's in a cell are managed in the Common Control Channel. Common Traffic Channel is for traffic for all (or a specified group of) UEs in the cell

When there is a dedicated, active connection, the network sends control information through the Dedicated Control Channel.In the Uplink direction, there are the Common Control Channel, Dedicated Traffic Channel and the Dedicated Control Channel.The second level is known as the Transport Channels. In some cases, a transport channel may contain one or more logical channels.The BCCH and PCH Transport Channels carry their respective logical channels (Broadcast and Paging Channels).The FACH (Forward Access Channel) carries information (when specified by RNC) from the common and dedicated control channels.The DCH (Dedicated Channel) is the only dedicated transport channel, the rest are common. One DCH channel, may carry one or more DTCH.In the Uplink, and as in GSM, the RACH (Random Access Channel) carries initial access information when required.The Common Packet Channel is used to carry packet(s), providing the common resources of the system are used for this purpose.The final layer use in the channels, is known as the physical channels. These are the channels that are present on the air-interface of a cell.

The Network Synchronisation information is carried in the Synchronisation Physical Channel. This channel is created in Node B, so it does not need any logical or transport channels.

There are 2 Common Control Physical CHannels, primary and secondary. The primary carries the cell information, whereas the secondary carries other common control information.The DPCH (Dedicated Physical Channel) is a multiplexed combination of the DPDCH (dedicated user traffic) and the DPCCH (dedicated signaling channel)..The Physical Random Access CHannel carries the RACH data.The user's traffic and signaling information is divided in the uplink direction between the DPDCH and DPCCH physical channels.

Downlink Uplink

Logical Channel

sBCCH PCCH DCCH DTCH CCCH DTCH DCCH

Transport

Channels

BCH PCH DCH DCHRACH CPCH

Physical Channel

s

SCH1/2(createdin Node

B)

CCPCH-1 CCPCH-2 PRACHDPDCHDPCCH

CCCH CTCH

FACH DSCH

PDSCH PCPCHDPCH

(DPDCH+DPCCH)

When sending short packets, and a dedicated channel is not needed, then they are sent on the PCPCH (Physical Common Packet Channel).

DTCH is a point to point channel dedicatedto one UE for transfer of the user information

PDSCH is a downlink shared channel for user data.It carries the DSCH transport channel which is controlledOn a frame by frame basis thus allowing for variation in bitrates

27 © NOKIA

FDD-mode: Logical and Transport Channel DL

BCCHBroadcast 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)

BCHBroadcast Channel,

PCHPaging Channel

FACHForward Access Channel

DSCHDownlink Shared Channel

DCHDedicated Channel

Transport Channels

dedicatedtransportchannels

commontransportchannels

28 © NOKIA

FDD-mode: Logical and Transport Channel UL

CCCHCommon Control Channel(control information withoutRRC connection)

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

DTCHDedicated Traffic Channel(user data)

Logical Channels (content)

RACHRandom AccessChannel

CPCHCommon Packet Channel

DCHDedicated Channel

Transport Channels

dedicatedtransportchannels

commontransportchannels

29 © NOKIA

Downlink transport to the physical channel mapping

SCH-1/SCH-2 (created in NodeB)

BCCH

BCH

PCCH

PCH

CCPCH-1

CCCH

FACH

CCPCH-2

DCCH

(DPDCH+DPCCH)

DTCH Logical Channels

Transport Channels

Physical ChannelsDPCH

CTCH

DCH DSCH

PDSCHSCH-1/SCH-2 (created in NodeB)

BCCH

BCH

PCCH

PCH

CCPCH-1

CCCH

FACH

CCPCH-2

DCCH

(DPDCH+DPCCH)

DTCH Logical Channels

Transport Channels

Physical ChannelsDPCHDPCH

CTCH

DCH DSCH

PDSCH

34 © NOKIA

FDD-mode: Physical Channel

UE Node B

Downlink DPDCH & DPCCH

Uplink DPDCH

Uplink DPCCH

Slot Slot Slot DPDCHDedicated Physical Data Channel

DPCCHDedicated Physical Control Channel

35 © NOKIA

Physical uplink mapping

CCCH

PRACH

RACH

DTCH

DPDCH

DCH

DCCH

DPCCH PCPCH

CPCH

Logical Channels

Transport Channels

Physical Channels

38 © NOKIA

Radio Resource ManagementIub Iu

Iur

Interface

Units

Interface

Units

(Wideband)Switching

ControlUnits

Radio

Resource

Management

O&MInterface

to/from NetworkManagement

to/fromotherRNCs

to/fromCore

Network

to/fromthe BSs

Radio Resource Control (RRC) Admission Control Code Allocation Power Control Handover Control and Macro

Diversity

39 © NOKIA

Radio Resource Management functions

PC

HC connection basedfunctions

LC

AC network basedfunctions

PS

RM

Packet Scheduler - PS Resource Manager - RM Admission Control - AC Load Control - LC Code Allocation

Power Control - PC Handover Control, Macro Diversity - HC

40 © NOKIA

RRC states

Idlemode

Connected Mode

Cell DCH

URA PCH

Cell PCH

Cell FACH

41 © NOKIA

Management of channels in RRC

RLC RLC RLC

RRCsignalling

CS RAB (speech)

PS RAB (data)

MAC

L1

Iub/IurMAC for CommonChannels

• 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 ControlMAC: Medium Access Control

• Selection of the data to be inserted in the Radio Frame• Selection of common or dedicated channels• Multiplexing of logical channels into same transport channels• Ciphering for RT

42 © NOKIA

Admission Control

R ad io A cce ss B ea re rsin U u In te rface

S IR - A llo w e d R a n g eA d m iss ion C o n tro l

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

Inte

rfer

ence

Mar

gin

(d

B)

FactorLoad

LogI_1

110

43 © NOKIA

TRHO_threshold

Prx_target

Prx_target_BS

UL interference power

Load

Planned load area

Marginal load area

planned uplink interference power

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

Prx_offset

Uplink Admission Control

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

44 © NOKIA

Code allocation

CELL 1 CELL 3CELL 2

1. Scrambling codes

2. Channelisation codes

full code set / cell

SUBS2SUBS1

45 © NOKIA

Scrambling code planning

• 512 DL scrambling codes are used, 8 in each of the 64 code groups.

• All cells that MS is able to measure should have different scrambling codes.

1. Use different scrambling code groups in the neighbouring base stations.

2. Probably code group allocation will be done in network planning. Functionality needed in the network planning tool, which reminds of frequency planning in GSM planning tools.

3. The re-use factor could be 64 as there are 64 code groups. The scrambling code group planning for different carriers can be done independently. It is for further studies, whether or not more optimisation would be needed.

46 © NOKIA

Tree of orthogonal short codes 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 avoid shortage 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 ofcode allocation

47 © NOKIA

Power control

Node B

P1 P2

Open Loop Power Control (Initial Access)

Closed Loop Power Control

Outer Loop Power Control

Node B RNC

48 © NOKIA

Packet Scheduler• A non-real time call constitutes of a bursty sequence of packets.

• In the downlink, the Packet Scheduler decides which channel to use, DCH or FACH.

• The load target can be reached by scheduling the transmission of NRT packets .

time

packet service session

packet call

reading time

packet size packet arrival interval

49 © NOKIA

Handover types

CNRNC

MSCBSC

GSM900/1800GSM900/1800

WCDMA FDDWCDMA FDD

Inter-SystemInter-System

Intra-SystemIntra-System

WCDMA TDDWCDMA TDD

Inter-SystemInter-System

50 © NOKIA

Active cells and soft handovers

CNRNC

frame reliability info

frame reliability info

frame selection /duplication

BS1 BS2

Soft handover windowP

2) Add BS2

1) Connection to BS1

3) Drop BS1

4) Connection to BS2

51 © NOKIA

Handover types

Soft Handover

4

Hard/Inter-Frequency Handover

Softer Handover

Inter-System Handover

Node B

Frequencyf1

Frequencyf1

Frequencyf1

Frequencyf2

UMTS GSM900/1800

Sector 1f1

Sector 2f1

Sector 3f1

Multipath Signalthrough Sector 1

Multipath Signalthrough Sector 3

Frequencyf1

Frequencyf1

RNC RNCIur

Iub Iub

Node B

Node B Node B

Node BNode B

Node B

Node B BTS

52 © NOKIA

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

UMTS GSM900/1800UMTS GSM900/1800

Intersystem handover from GSM

UE GSM BSS MSC UTRAN

Release resources

53 © NOKIA

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

UMTS GSM900/1800UMTS GSM900/1800

Intersystem handover from UTRAN

UE GSM BSSMSCUTRAN

Release resources

RNC

54 © NOKIA

Micro Diversity control

Node BReceiver(RAKE)

Same signal propagating differentways in the Radio Path

Summed signal

Uplink Direction (Micro) Diversity Point

55 © NOKIA

Macro Diversity in the RNC

Node B

Node B

Node B

RNC

RNC

Macro Diversity Point

CoreNetwork

ActiveSet

56 © NOKIA

Handover control

MeasurementReports

HandoverAlgorithm:

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:

57 © NOKIA

Logical description of Load Control

• The purpose of load control is to optimise the capacity of a cell and prevent 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 change info

Load status

58 © NOKIA

Load Control• 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 normal state in a fast and controlled way.

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

• 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 and parameters set by Radio Network Planning.

59 © NOKIA

The restriction of CDMA system is interference

The more transmission poweris required to achieve certain quality

The further away users are connected

The more users that are connected

Finally the capacity is filled

60 © NOKIA

• 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 mobility purposes all the time. The proportion between RT and NRT traffic varies all the time.

Capacity

Time

Overload

Load Target

Overload Margin

Pow

er

Estimated capacity for NRT traffic.

Measured load caused by non-controllable load

61 © NOKIA

AdmissionControl

LoadControl

PacketScheduler

P rxTarget o rP txTarget

P rxTarget+P rxO ffse t o rP txTarget+P txO ffset

P rxThresho ld orP txThresho ld

P _C ellM ax

N o actionsP S increases theam ount o f N R T

bearersA C adm its R T

bearers norm ally

N o actions

Load preventive LCactions

O verload actions

A C does not adm itnew bearers

A C does not adm itnew bearers

P S decreases theb itra tes and drops

N R T bearers

P S decreases theb itra tes o f N R T

bearers

P S does notincrease N R T load,

but can changeN R T b itra tes

P ower

Load

Summary

62 © NOKIA

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

63 © NOKIA

3G-UMTS Radio Path & Transmission Key Points 2

• Receiver in UE and BS: Antimultipath RAKE receiver

• Radio Resource Management in RNC:• Radio Resource Control => States: Idle & Connected• Admission Control => SIR• Code Allocation• Power Control => Open Loop, Closed Loop &

Outer Loop• Handover Control and Macro Diversity

=> Soft, Softer, Hard & Inter System

• Cell Breathing:• Cell capacity and coverage are related.

65 © NOKIA

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 cell breathing?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)

66 © NOKIA

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)

67 © NOKIA

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)

69 © NOKIA

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 upon interference.

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)

70 © NOKIA

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)

72 © NOKIA

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

Review (6/8)

73 © NOKIA

12. What is the difference between micro and macro diversity?

a. There is no difference.

b. Micro diversity is the combination of signals between the BTS and the UE, whereas macro diversity is the combination of signals from many BTSs in the RNC.

c. Macro diversity is the combination of signals between the BTS and the UE, whereas micro diversity is the combination of signals from many BTSs in the RNC.

d. Macro and micro diversity are UE-specific functions.

13. In WCDMA, what is meant by the active set?

a. A group of UEs.

b. A group of Active RNCs.

c. A group of cells communicating with a UE.

d. It is the same as a location area.

Review (7/8)

75 © NOKIA

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)

81 © NOKIA

Characteristic of a cell

Dedicated Channels

Common Channels

Coverage and capacity are related. The more capacity

used, the cell shrinks. This is known as cell breathing.

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Differences between WCDMA and GSM

High bit rates

Spectral efficiency

Different qualityrequirements

Efficient packet data

Downlink capacity

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Different UMTS cells and BTS

F1

F2

F2

F3

F3

F3

Micro BTSMacro BTS

Pico BTSs

1 - 10 km

50 - 100 m200 - 500 m

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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.

86 © NOKIA

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

NOTE!WCDMA capacity is a function of radio environment, user mobility/location and propagation conditions. Examples above are just examples of WCDMA cell capacities of a 3 sector macro cell BS configuration.

87 © NOKIA

Cell load

0

5

10

15

20

25

0 0,2 0,4 0,6 0,8 1

Load factor

Lo

ss

(d

B)

• Max. recommended load: 70%, typically 30-50%

• 50% load means 3 dB loss in link budget

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Physical layer bit rates (Downlink)

• 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 speechFull rate speech

128 kbps384 kbps

2 Mbps

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Uplink coverage of different bit rates

0

0.5

1

1.5

2

2.5

3

3.5

32 kbps 64 kbps 144 kbps 384 kbps 1024 kbps 2048 kbps

Ra

ng

e [k

m]

Suburban area with 95 % outdoor location probability

Continuous high bit rate coveragein uplink is challenging Coverage solutions are important

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Node BNode B

UE

UE

Cell edge

2Mbps downlink coverage

2Mbps Uplink coverage

Possible Macro cell coverage example

Approximately2.2 Km

Approximately1.1 Km

144Kbps Uplink coverage

Downlink 2Mbps can be 50-100% of cell area

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Node BNode B

UE

UE

2Mbps downlink coverage

2Mbps Uplink coverage

Approximately2.2 Km

Approximately1.1 Km

144Kbps Uplink coverage

NOTE:Several assumptions combining the benefits of WCDMA have been made to create this simplified cell example•Cell coverage is purposely limited•Six sectors under one Node B•All users are evenly distrubuted over the cell area• 3dB interference margin assumed;but other values could be tolerated•Max Up Link output power 21dBm(125mW)•Several types of gains assumed:

• Variable processing gains for various bitrates• Multipath gains• User speed less than 3Km/h

Cell performance example; approximate capacities.Note that these numbers are alternative uses; not simultaneous• 98 Full Rate speech users/sector supported• 588 Full Rate speech user on the cell area• 96 144 Kbps users supported on the full cell area• DL 6 2Mbps users supported on 50-100 % of cell area• UL 6 2Mbps supported on 50 % of cell area. • UL main limitation is UE UL power

Possible Macro cell coverage example

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Processing gain

Frequency (Hz)

Voice user (12,2 kbit/s)

Packet data user (384 kbit/s)

Pow

er

den

sity

(W

/Hz)

W

R

Frequency (Hz)

Unspread narrowband signal

Spread wideband signal

Processing Gain G=W/R=25 dB

Pow

er

den

sity

(W

/Hz)

W

R

Unspread "narrowband" signal

Spread wideband signal

Processing Gain G=W/R=10 dB

• Spreading sequences of different length• Processing gain is dependent on the user data rate

(User data rate) x (spreading ratio)= const.=W=3,84 Mcps

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Distribution of load

Voice traffic Data Traffic

Soft Capacity

Cap

acit

y p

er c

ell

per

car

rier

More DataMore Voice

800kbps Air Interface (L1) rate50 Erlang

Not Real Time (NRT) Packet switched• greater efficiency• greater total capacity

Real Time (RT) circuit switched• low predictable delay• lower total capacity

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RNC capacity planning

BS Speech Traffic:Kbit/s /Cell & Code Channel Am ount

BS Data Traffic:Kbit/s /Cell & Code Channel Am ount

Packet Switched Traffic:

Kbit/s

C ircuit Switched Traffic:

Erlangs [Kbit/s]

Concentration

RNC

03 umts radio path and transmissionnew

Software

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