wcdma introduction

8/10/2019 WCDMA Introduction

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Recruitment and Development Team @2013

PT Nexwave Indonesia


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Internal use only Nexwave Indonesia @2013

CHAPTER 1: WCDMA Overview and Network Architecture

CHAPTER 2: WCDMA Wireless Overview

CHAPTER 3: Physical Layer and WCDMA Channel


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Overview


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What is 3G?

3rdGeneration of mobile communication based on IMT-2000 global standardization

3G characteristic:

Designed for multimedia communicationfrom the beginning

Provides more efficientmeans for image and video transfer

Variable bit rates up to 2 Mbps (Rel99)

Multiple access using Wideband CDMA (WCDMA) All cells are using same frequency band, no need Frequency planning

Using codes for separate user and channel

Effective Signal Bandwidth 3.84MHz (wider bandwidth compared to GSM)

Short time delay (compared to GSM), 10ms frame length with 15 time slots

Multiple carriers can be used to increase capacity

Inter frequency functionality to support mobility between frequencies carrier Compatibilitywith GSM technology

Inter System functionality to support mobility between GSM and UMTS

Soft Handover, add margin which improved performance

Overview


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Overview


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Architecture


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User Equipment (UE)

Mobile equipment (ME): Radio communication over Uu interface

UMTS Subscriber Identity Module (USIM): Subscriber identity information, authentication

algorithms, encryption keys, etc

UMTS Terrestrial Radio Access Network (UTRAN)

Node B (Base Station): Handles/manages the traffic between Uu and Iub interfaces. Basic

tasks like coding, interleaving, rate adaptation, modulation, spreading, closed loop power

control

Radio Network Controller (RNC): Control radio resources in its operation area. Provideservices for Core Network (CN). Load and congestion control, admissions control, code

allocation, radio resource management tasks.

Mobile Services Switching Centre (MSC) / Visitor Location Centre (VLR)

Handles switching in Circuit Switched (CS) connectionsand hold visitingusers service

profiles.

Serving GPRS Support Node (SGSN)

Similar functionality as in MSC/VLR but used for Packet Switched (PS) services

Other CN elements

Gateway MSC (GMSC): Handles incoming and outgoing CS connections

Gateway GPRS Support Node (GGSN): Like GMSC but in PS domain

Home Location Register (HLR): Master copy of users service profiles

Authentication Center (AuC): Handles authentication based on SIM data

Equipment Identity Register (EIR): Handles blacklist of Mobile Phone based on IMEI

Architecture



A method which allowed two ways communication between two points simultaneously.

Air Interface Overview

Ai I t f O i



5 3

3 1

4 52

3

5

4

3

Power

Frequency

1 2 3 4 5

1

2

3

4

5

1

2

2

1

TDM

-Time Division

Multiple Access-

2G e.g. GSM PDC

FDM

-Frequency Division

Multiple Access-

1G e.g. AMPS,

NMT, TACS

CDM

-Code Division

Multiple Access-

3G e.g. UMTS, CDMA2000

1 2 3UE 1 UE 2 UE 3 4 UE 4 UE 55

4 2

OFDM

-Orthogonal

Frequency

Division

Multiple Access-

e.g. LTE

multiple access method allows several users connected

to the same multi-point transmission medium to

transmit over it and to share its capacity

Each User has a unique

frequency

Each User has a unique

time slot

Each Transmitter has a uniquespreading code

Each Data Channel has a unique

orthogonal code

No dedicated physical

channel any more


Ai I t f O i



Spreading Code

Spread Signal

Data

Bits (In this drawing, 1 bit = 8 Chips SF=8)

Baseband Data

-1

+1

+1

-1

+1

-1

+1-1

+1

-1

ChipChip

Air Interface

Chips & Bits & Symbols


Ai I t f O i



Consist of two steps:

1. Channelization Operation; which transform data into chips

2. Scrambling Operation; which applied to the spreading signal

Spreading means increasing the bandwidth of the signal beyond the bandwidth normally required

to accommodate the information.

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 theSpreading Factor (SF). Channelization codes are orthogonal codes, meaning that in ideal

environment they do not interfere each other.

Scrambling is used on top of spreading, so it does not change the signal bandwidth but only

makes the signals from different sources separable from each other. As the chip rate is already

achieved in channelization by the channelization codes, the chip rate is not affected by the

scrambling.


Air Interface O er ie



SF = chip rate / symbol rate

High data rate Low SF code

Low data rate High SF code





Scrambling code: GOLD sequence

Not orthogonal

Does not change signal bandwidth and only make makes the signals from different

sources separable from each other

There are 224 long uplink scrambling codes which are used for scrambling of the

uplink signals. Uplink scrambling codes are assigned automatically by RNC.

For downlink, 512 primary scrambling codes are used. Downlink scrambling codes

must be planned carefully in network.

The scrambling code is always applied to one 10ms frame





WCDMA Codes:

In WCDMA two separate codes are used in the spreading operation: Channelization code

Channelization code is used to distinguish different physical channels of one transmitter

DL: separates different physical channels of one cell

UL: separates different physical channels of one user/UE

Scrambling code

Scrambling code is used to distinguish different transmitters

DL: separates cells in same carrier frequency

UL: separates users in same carrier frequency

Data

Bit Rate

ChannelizationCode

Scrambling Code

To be Transmit

Block Diagram:





Diversity technique is used to obtain uncorrelated signals for combining

Reduce the effects of fading

Fast fading caused by multi-path

Slow fading caused by shadowing

Improve the reliability of communication

Increase the coverage and capacity

Diversity techniques:

Time diversity

Frequency diversity

Space diversity

Polarization diversity




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Physical Layer


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y y

Physical Layer


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RAB (Radio Access Bearer) : The service that the access stratum provides to the non-access stratum for transfer of user data between User Equipment and CN.

RB (Radio Bearer) : The service provided by the layer 2 for transfer of user data

between User Equipment and Serving RNC.

RL(Radio Link) : A "radio link" is a logical association between single UserEquipment and a single UTRAN access point. Its physical realization comprises one ormore radio bearer transmissions.

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Physical Layer


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Radio Access Bearers are mapped onto these classes.

Traffic class Conversational class

conversational RT

Streaming class

streaming RT

Interactive class

Interactive best effort

Background

Background besteffort

Fundamental

characteristics

Preserve timerelation (variation)between informationentities of thestream

Conversationalpattern (stringentand low delay )

Preserve timerelation(variation)betweeninformation

entities of thestream

Requestresponse pattern

Preservepayload content

Destination isnot expectingthe data withina certain time

Preservepayload content

Example of the

application

- voice - streaming video - Web browsing - background down-load of emails

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Physical Layer


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Physical Layer


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WCDMA Channels


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Physical Channels

Transmission media.

Two types of physical channels defined in L1: FDD and TDD.

FDD is characterized by frequency, code, I/Q phase

Follow a layered structure of radio frames and time slots

Transport Channels describes the way information is transferred over the radio interface

Logical Channels the type of information transferred characterizes a logical channel

WCDMA Channels


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WCDMA Channels


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WCDMA Channels


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WCDMA Channels


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WCDMA Channels


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WCDMA Channels


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WCDMA Channels


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Synchronization Channel (SCH) Used for cell search

SCH is transmitted at the first 256 chips of every time slot

Common Pilot Channel(CPICH)

Carries pre-defined sequence

Fixed rate 30KbpsSF=256 The P-CPICH is a phase reference for SCH, Primary CCPCH, AICH, PICH.

Only one CPICH per cell

Broadcast over the entire cell

Primary Common Control Physical Channel (PCCPCH)

Carry BCH transport channel

Fixed rate30kbpsSF=256

WCDMA Channels


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Secondary Common Control Physical Channel (SCCPCH) Used to carry the FACH and PCH.

SF =256 - 4.

Paging Indicator Channel (PICH)

PICH is a fixed-rate (SF=256) physical channel used to carry the Paging Indicators (PI).

WCDMA Channels


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Physical Random Access Channel (PRACH) The Physical Random Access Channel (PRACH) is used by the UE to access the network and

to carry small data packets.

Acquisition Indicator Channel (AICH)

The Acquisition Indicator Channel (AICH) is a common downlink channel used to control the

uplink random accesses. When the NodeB receives the random access from a mobile, it sends back the signature of

the mobile to grant its access.

WCDMA Channels


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Uplink Dedicated Physical Channel DPDCH carries data generated at Layer 2 and higher layer

DPCCH carries control information generated at Layer 1

DPDCH is used to bear data at physical layer. DPCCH provide control data for DPDCH, such

as demodulation, power control etc.

Downlink Dedicated Physical Channel DCH consists of dedicated data and control information.

The functions of downlink DPDCH/DPCCH are similar with uplink DPDCH/DPCCH..

WCDMA Channels


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High-Speed Physical Downlink Shared Channel (HS-PDSCH) HS-PDSCH is a downlink physical channel that carries user data and layer 2 overhead bits

mapped from the transport channel: HS-DSCH.

SF=16, can be configured several channels to increase data service

High-Speed Shared Control Channel (HS-SCCH)

HS-SCCH is a fixed rate (60 kbps, SF=128) downlink physical channel used to carry downlinksignaling related to HS-DSCH transmission

Carries physical layer signaling to a single UE ,such as:

Modulation scheme (1 bit),

channelization code set (7 bit),

transport block size (6bit),

HARQ process number (3bit), redundancy version (3bit),

new data indicator (1bit),

UE identity (16bit).

WCDMA Channels


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wcdma introduction

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