UMTS Basic Principle

8/12/2019 UMTS Basic Principle

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Section 4

W-CDMA Principles


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The Spread Spectrum Principle

The Channelization codes & Scrambling codes. Their main properties

The importance of Eb/No

The concept of Power Control

The coverage limits

The Rake Receiver

The macro-diversity

Handovers

Objectives

At the end of this session, you will be able to:

W-CDMA Principles


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Power

PowerPower

FDMA TDMA

W-CDMA

Dedicated Channel: An indiv idual ly-assigned, dedicated pathway

through a transm ission medium

for one users information

Access Technologies


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Je parle franais Ich spreche

deutsch

I speak

english

PARLO ITAL IANO!

Access Technologies

Analogy with the W-CDMA


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Duplex Spacing: 190 MHz

FDD

Time

Frequency

Power

5 MHz 5 MHz

Code Multiplex

UL DL

UMTS USER 1

UMTS USER 2

Time

Frequency

Power

TDD

5 MHz

Code Multiplex

&

Time Division

666.67 s

DL

UL

DL

DL

UL

UMTS USER 2

UMTS USER 1

Access Technologies

W-CDMA: FDD or TDD


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Binary data to transmit 0 1 0 0 1 0

The faster is the bit rate, the more the energy is spread on the spectrum

+ a

- a

a2T0

s(t)

T0

1/T0 2/T0Frequency

Time

0 1 0 0 1 0

+ a

- a

a2T1

s(t)

T1

1/T1 2/T1Frequency

NRZ

coding

Time

0 1 0 0 1 0

Power

spectrum

Spread Spectrum Principle

1 - Time - Frequency Duality


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Tbit

Tchip

Data sequence

spreading sequence

transmitted sequence

a2Tbit = Ebit

1/Tbit

Tchip = Echip

1/Tchip

Frequency

a2Tchip

1/Tchip

+a

-a

-1

+1

-a

+a

x

=

Data

sequenceTransmitted

signal

Spreading sequence generator

Modulation

x(t)Power spectrum


2 - Transmission


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Tbit

Tchip

Data sequence

spreading sequence

received sequence

a2Tbit = Ebit

Power spectrum

1/Tbit

Tchip = Echip

1/Tchip

Frequency

a2Tchip+a

-a

-1

+1

-a

+a

x

=

1/Tchip

Received

signal

Data

sequence

Spreading sequence generator

Demodulation

x(t)


3 - Reception


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4 - Code Multiplexing

Power spectrum

User 1

User 2

User 3

User 4

User 5

Spreading

Code 1

Code 2

Code 3

Code 4

Code 5

Composite signal

5 MHzCodes discriminate users


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Unwanted Power

from other sources

Using the right mathematical sequences

any Code Channel can be extracted

from the received composite signal


5 - Extraction


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Scrambling code

Channelization code 1



User 1 signal

User 2 signal

User 3 signal

BTS

Codes Multiplexing

1 - Downlink Transmission on a Cell Level


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BTS

Scrambling code 3

User 3 signal

Channelization code

Scrambling code 2

User 2 signal

Channelization code

Scrambling code 1

User 1 signal

Channelization code

Codes Multiplexing2 - Uplink Transmission on a Cell Level


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Cch,1,0=1

Cch,2,0=1 1

Cch,4,0=1 11 1

Cch,4,1=1 1-1 -1

Cch,2,1=1 -1

Cch,4,2=1 -1 1 -1

Cch,4,3=1 -1-1 1

SF = 1 SF = 2 SF = 4 SF = 8 SF = 16, 32, 64, 128, 256, 512

Cch,2,0=1 1

Cch,2,1=1 -1

Cch,4,0=1 1 1 1

Cch,4,1=1 1 -1 -1

Cch,4,2=1 -1 1 -1

Cch,4,3=1 -1 -1 1

Channelization Codes - OVSFOrthogonal Variable Spreading Factor: code tree generator


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+

-1 -1 -1

-1 -1 -1 -1

1 1 1 1

1 1 1 1

-1

*

1 1 1 1-1 -1 -1 -1

Cj

Ck

T0 synchronization

= 0+

-1 -1 -1

-1 -1 -1 -1

1 1 1 1

1 1 1 1

-1

*

1 1 1 11 -1 1 -1

Cj

Ck

no T0 synchronization

= 4

=> Orthogonal => Non orthogonal

No correlation Small correlation

Channelization Codes - OVSF

Orthogonality


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Physical Layer Structure

Frame #0 Frame #1 Frame #i Frame #4095

System frame = 4096 frames = 40.96 seconds

Slot #0 Slot #1 Slot #j Slot #14

Frame= 15 slots = 10 ms = 38400 chips

Slot= 0.667 ms = 2560 chips

Data or control or mixed: 10*2kbits, k from 0 to 6 (UL), from 0 to 7 (DL)

UMTS Frame Format


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A Tapped, Summing Shift Register

Sequence repeats every 2N-1chips,

where N is number of cells in register

Scrambling Codes

Scrambling codes Properties:

38 400 chip long sequences

Repeated every 10 ms

Issued form Pseudo Noise sequences


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Scrambling Codes Properties

Auto Correlation

Synchronized

=> Complete Correlation

Shifted

=> Almost Orthogonal

Almost orhtogonal

Cross Correlation

Random delay


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Uplink Scrambling Codes

Total of 224long scrambling codesof 38,400 chips

225-1 chip longsequences

X25+ X3+ 1

X25+ X3+ X2+ X + 1

I

Q


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Downlink Scrambling Codes

8192scrambling

codes

512 sets of 1primary and 15

secondarycodes

512 primarycodes dividedinto 64 groups

Possibility of 262,143 different downlink scrambling codes

Only 8192 different scrambling codes have been defined

8192 ...

Cell #1

Cell #512

...

Primary scrambling code

Secondary scrambling code #1




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Exercise

UE1

How do UE1and UE2get them bits?


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Channelization Codes Multiplexing

-11User 1

User 2

Code 1: Cch(SF= )

Code 2: Cch (SF= )

1-11 1-11

=

+

*

*

=

=2

-2

0

1

1-1 -1 1 1 1 -1-1

1 -1-11

-1

-1

UsersComposite

Signal

1

1


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Scrambling code

Users CompositeSignal

Scrambling

Code

*

2

0

-2

2

0

-2

=

1

-1

TransmittedSignal


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Radio Interferences2

0

-2

Transmitted

Signal

0

0

Noise

ReceivedSignal =

1

-1

1

-1

+


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UE1: Reception & Decoding

0

Received

Signal

1

-1

1

-1

1

-1

Scrambling Code

Channelization Code

Data

Extraction

*

*


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UE2: Reception & Decoding

0

Received

Signal

1

-1

1

-1

1

-1

Scrambling Code

Channelization Code

Data

Extraction

*

*


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Basic W-CDMA Elements

C

I

N

C

CEb/No

1 - Eb/NoW-CDMATDMA-GSM

Power spectrum

1

1

11

1

1

1

2

2

2

2

3

3

3

3

3

2

4

4

4

4

4


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Maximum noise level

Eb/No

required


Power spectrum

a2Tbit = Ebit

gain

Unwanted power

from other sources

2 - Eb/No

Echip

Eb / No = C / I x processing gain

Available power to share

between users


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a2Tbit = Ebit

Power spectrum

Maximum noise level

Eb/No

required

Unwanted power

from other sources

Eb/No

Powercontrol

Power , Interference , Capacity .


Eb/No & Power Control


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Power Control

1 - Open Loop

MS Access Pre Amble #1 with estimated power

MS Access Pre Amble #n with increased power

RNS Response with Power Control

MS Access Pre Amble #2 with increased power


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Power ControlClosed Loop (Uplink)

Inner Loop

Outer Loop

Service => QoS

RNC setsSIR target for service

Iub

BTS sendsPower Control bitsto UE(1500 times/second)

MS Tx

RNC sends new SIR target

BS continues Power Control

RNC calculatesBLER for Tx

BTS transmits the received blocks

RNC receives a Service Request


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Interference level

Example: 2 UEs at thesame distance from theBTS using 2 data rates

Eb/No

require

d

SF

=

128

Service provided: Speech

Interference level

Eb/No

required

Service provided: Data 144

User 2 needs more power for theUL & DL for the same quality as

user 1

BTS

Received powerReceived power

Coverage Limits (1)

UE2UE1

Speech 8 kbps Data 144 kbpsThe higher the SF, the less power required


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SF = 128

Speech 8 kbps Data 64 kbps Data 384 kbps

BTS

SF = 32

SF = 4

Coverage Limits (2)

The coverage limits are determined by

the Uplink link Budget


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Radio Resource Management

Mapping between demanded QoS, subscription type and allocated QoS

RAB QoS attri butesTraffic class

Maximum bitrate

Guaranteed bit rate

Delivery order

Maximum SDU size

SDU error ratio

Residual bit error ratio

Delivery of erroneous SDUs

Transfer delay

Traffic handling priority

Pre-emption Capability

Pre-emption Vulnerability

Queueing

Allocation/Retention

Priority(ARP)

(User Type)

Traffic Class

Traffic Handlingpriority(THP)

(Service Type)

MAC logical channel prioritySRB > C > S > I > B

Iub/Iur

Allocation/Retention Priority

Iub/IurFrame Handling Priority

Scheduling Priority Indicator

Common Transport Channel Priority Indicator

DCH/HSPA/MBMS

(Bearer Type)Scheduling Priority

Data Rate Application Priortiy

+

+

+

Basic Priority

Diff t T Of P i it


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Different Type Of Priority

Priority Function Case

Basic Priority Admission Control

HSDPA Schedule

HSUPA Schedule

(1).In case of admission control, RNC get AC thresholdthrough BP; so when cell load is high, high priority user

can be granted, while low priority user will be rejected.

(2) For HSDPA Service, when there is multiple users,

NODEB will allocate code and DL power based SPI

(associated with BP)

(3) For HSUPA ,when there are multiple users, NODEB

will allocate power grant based SPI (associated with BP).

SP of RNC Congestion Control (1)When cell is congestion, and user was pre-emption, RNC willselect user according to the SP

(2) When cell is congestion ,and user was queued, RNC will select

user in queue to execute Admission control according the SP

Application

Priority

Congestion Control

OverLoad Control

(1)When cell is congestion ,and trigger downgrade ,RNC will select

user to downgrade rate according the AP.

(2) When cell is overloaded , RNC will select user to do someaction , so the load can be down.

U li k Li it (1)


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UE2

UE3

UE2 UE3

BS Receiver

BTS

Maximum Noise Floor

Lowest Despread SignalEb/No

ProcessingGain

Uplink Limits (1)

UE1

Receiver sensitivityUE1

U li k Li it (2)


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Receiver sensitivity

BS Receiver

Maximum Noise Floor

Lowest Despread Signal

BTS

Cell Breathing

Eb/No

ProcessingGain

UE2 UE3

Eb/No

ProcessingGain

UE1 UE4

The more loaded the cell, the smaller the cell.

Uplink Limits (2)

UE4

C it Li it (1)


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BS Power Amplifier

50 W

0 W

BTS

BTS

UE1 UE2 UE3 UE4

Capacity Limits (1)

UE1

UE2

UE3

Capacity Limits (2)


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UE2 UE3UE1

BS Power Amplifier

50 W

0 W

UE4

BTS

BTS

Capacity Limits (2)

Rake Receiver


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TX

D(t)

Delay 0

Delay 1

C(t-0)

+C(t-1)

Delay (1)

RX

C(t-n)

Delay (0)

Delay (n)RX

RX

C(t)

0

1

n

Take advantage ofmultipath diversity

BTS

Rake Receiver

UE

Spreading &Scrambling

Macro Diversity


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Macro-Diversity

Softer Hand Over

Node B(BTS)

RNC

Data UL

Data UL1Data UL2 Data UL

Data UL

Data DLData DL

Data DL1

Data DL1

Data DL2

Data DL

UE

Data DL2

Data UL

Core

Network

Macro Diversity


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Macro-Diversity

Soft Hand Over Intra RNC

RNC

Data UL1

Data UL1Data UL2

Data UL

Data UL

Data DL

Data DL1

Data DL1

Data DL1Data DL2 Data DL

UE

Core

Network

Data DL2

Data UL

Data DL2

Data UL2

Data UL2

Data UL1

Node B(BTS)

Node B(BTS)

Macro-Diversity


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Macro Diversity

Soft Hand Over Inter RNC: Serving RNC (SRNC) and Drift RNC (DRNC)

Node B(BTS)

SRNC

DRNCNode B(BTS)

Data UL

Data UL

Data ULData UL1

Data UL2

Data UL2

Data UL1Data UL2 Data UL

Data UL

Data DLData DL2

Data DL2

Data DL1

Data DL2

Data DL1

Data DL1Data DL2 Data DL

UE

CoreNetwork

Different Types of Handover


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Different Types of HandoverSoft Handover Softer Handover Hard Handover

SRNC DRNC

Node B

UE

Core Network

SRNC

Node B

UE

Core NetworkSRNC

UE

Core Network

GSM / GPRSBSS

SRNC

UE

Core Network

GSM / GPRS

BSS

Inter RNC Intra Node B

W-CDMA Questions


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W-CDMA Questions

1. What is the link between bit rate, chip rate and SF?

2. What is the use of: the downlink & uplink channelization codes?

the downlink & uplink scrambling codes?

3. What is the relationship between Eb/No, Ec/No and the processing gain?

4. What are the different types of Power Control ?

5. The higher the user data rate:

the smaller is the cell?

the wider is the cell?

6. The more loaded the cell:

the smaller the cell?

the wider the cell?

7. Why is macro-diversity an important concept in UMTS?

UMTS Basic Principle

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