Présentation_UMTS

8/6/2019 Prsentation_UMTS

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UMTS

Introduction

and

WCDMA Channels


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GSM Radio Access Network

Core Network

BSC

BSC

A/Gb

Abis

UmBTS BTS

BTS

MS


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WCDMA Radio Access Network

Iu= Iu PS - Gb

Iu CS - A

Core Network

RNC

RNC

Iu

Iur

Iub

Uu

NodeBUE

UTRAN

Core Network

NodeB

NodeB


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RN Interfaces

Iu Iu PS

Connection to the packet switched core network domain SGSN/GGSN

Iu CS Connection to the circuit switched core network domain

MSC Protocol RANAP

Iur RNC interconnection

for SHO support Protocol RNSAP

Iub

Protocol NBAP Uu

Protocol RRC, RLC, MAC

Core Network

RNC

RNC

Iu

Iur

Iub

UuNodeB UE

NodeB

NodeB


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Comparison, GSM - WCDMA

GSM

Neighbor cell planning (BCCH/BSIC

planning)

8 timeslots, repetition pattern 4.6 ms

200 kHz carrier separation

Frequency Hopping

Power Control

Hard (non-continuous) handover

Timeslot based Admission

WCDMA

Neighbor cell definitions/Scrambling

code planning

Channels(/users) are separated by

different codes 5 MHz carrier separation

Fast Power Control

Soft/Softer Handover

Admission Control

Congestion Control


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Codes in WCDMA

Codes are used for two purposes: Differentiate channels and users

Spreading the data over the entire bandwidth

Spreading code = Scrambling code + Channelization code

Scrambling codes Separates different mobiles (in uplink)

Separates different cells (in downlink)

Good correlation properties

Channelization codes Separates different channels that are transmitted on the same scrambling code

Orthogonal Variable Spreading Factor (OVSF) codes

Period depends on data rate


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Reception

Takes advantage of multipath propagation

The Rake receiver combines multipath components

Need to estimate delay, amplitude and phase for each

multipath ray


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Power Control

Open loop power Control

Initial power setting

Outer Loop (RNC)

Adjust quality target

dependent on performance Inner Loop (fast power

control-NodeB)

compensates for fading

channels

needs dedicated controlchannel for power control

commands

Without power control

PTX

tfading

channel

t

PRX

fading

channel

t

PTX

t

PRX

With power control


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Soft Handover

Soft handover reception

combines signals from different base stations

BS 1 BS 2

RNC


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WCDMA use a 1-frequency reuseNeighbor cell definitions

Scrambling code planning is replacing BSIC/frequency planning

WCDMA separate users and channels with codes rather than

timeslots/frequencies

WCDMA is dependent on a number of key functions in the radio

network

Power Control

Soft Handover


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RAB: Radio Access Bearer

Owned by the core network (CN)

CN determines traffic class and QoS

Real-TimeApplications

Streaming Class: Preserve time relation between entities (packets) in

a data stream

Conversational Class: Preserve time relation between entities within

a certain delay

Non-RealTimeApplications Background Class: Destination is not expecting data. Preserve Payload

Interactive Class: Request / Response Pattern with preserved payload


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The WCDMA radio interface has three channels: Physical Channel, Transport

Channel and Logical Channel:

Logical channel: Carrying user services directly.

* Control channel and service channel.

* is transferred.

Transport channel: It is the interface of radio interface L2 and physical layer.

* Dedicated channel and common channel.

* and with data is transmitted

Physical channel: It is the ultimate embodiment of all kinds of information

when they are transmitted on radio interfaces.

* InUMTS, it corresponds on a frequency, a specific set of codes and phase.

* Information container.


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Logical Channel (1)

Defined by which type of information that is transported:

Control Channels

Broadcast Control Channel (BCCH, DL)

Paging Control Channel (PCCH, DL)

Dedicated Control Channel (DCCH, UL/DL)

Common Control Channel (CCCH, UL/DL)

Traffic Channels

Dedicated Traffic Channel (DTCH, UL/DL)

Common Traffic Channel (CTCH, DL)

Medium AccessControl

Logical

Channels

Transport

Channels

BCCH PCCH DCCH CCCH DTCH

Control Plane User Plane


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Logical Channel (2)Control channels:

Broadcast ControlChannel (BCCH):

It broadcast system control information for all mobiles in a cell like: Code values in the cell,

neighbors information, allowed power levels in downlink direction.

PagingControlChannel (PCCH):

* It transfer paging information in downlink direction.

* Network page the mobile to discover the UE location or UE in a cell connected state.

CommonControlChannel (CCCH):

* Network may have certain tasks which are or may be common to UE in the cell.

* Its being used in both direction downlink & uplink.

* The CCCH is also used when UE is accessing a new cell after cell reselection.

Dedicated ControlChannel (DCCH):

Bi-directionnel channel, transmits dedicated control informationb

etween UE and the network


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Logical Channel (3)

Traffic channels:

Dedicated Traffic Channel (DTCH):

It is used transfer the user data between the network and theUE in both uplink and downlink directions.

CommonTraffic Channel (CTCH):

It is used to transfer the data from one point to all mobiles or

a specified group of mobiles.


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Transport Channels (1)

The services offered by the physical layer to the MAC layer

Characterized by howandwithwhat characteristicsdata is transferred over the air

Common Transport Channels:

Broadcast Channel (BCH, DL)

Paging Channel (PCH, DL)

Forward Access Channel (FACH, DL) Random Access Channel (RACH, UL)

High-Speed Downlink Shared Channel (HS-DSCH, DL)

Dedicated Transport Channels: UE identified by the physical channels

Dedicated Channel (DCH, UL/DL)

MAC

PhysicalLayer

Transport Channels


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Dedicated Traffic Channels:

Dedicated Channel (DCH):

It is the channel used to send dedicated control and user data

between UE and the network in both uplink & downlinkdirections

CommonTransport Channel:

Random Access Channel (RACH):

It is used for initial access of for transmission of relatively

small amounts of data.


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Forward Access Channel (FACH):It is a downlink common channel used for dedicated signalling, or

transmission of relatively small amouts of data.

Broadcast Channel (BCH):

It broadcasts system information in the downlink direction for all mobile

stations in a cell.

Paging Channel (PCH):

Its a downlink common channel used to send paging notification

messages.Downlink Shared Channel (DSCH):

It is common channel used to send dedicated control and user data.


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Mapping of Logical Channels toTransport Channels

CCCH

CommonControlChannel

DCCH

DedicatedControlChannel

PCCH

PagingControlChannel

BCCH

Broadcast ControlChannel

DTCH

DedicatedTraffic Channel

PCH (DL)

PagingChannel

FACH (DL)

ForwardAccessChannel

BCH (DL)

Broadcast Channel

RACH (UL)

RandomAccessChannel

DCH (DL/UL)

DedicatedChannel

CommonTransport Channels

Transport Channels Logical Channels


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Physical Channels (1)

Physical Channels are the L1 realizations ofTransport channels

Defined by specific carrier frequency, code, timing andphase

The Physical layer provides:

Channel coding, interleaving

Mapping of transport channels to physical channels

Mapped into 15 slots in a radio frame pattern (10 ms)

Spreading

Modulation


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Physical Channels (2):

Dedicated Physical Control Channel

For each radio link, there is one DPCCH, it carries control

information like:

Pilot bits (used to support channel estimation at rake receiver)

Transmit Power Control (TPC) commands (Used power control)

Feedback information (FBI) needed with transmit diversity

Transport Format Combination Indicator (TFCI)

Spreading factor is always 256.


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Dedicated Physical Data Channel

Each radio link may have no DPDCHs or several DPDCHs.

Spreading factor for the DPDCH can be between 256 and 4.

DPCCH & DPDCH are time multiplexed in downlink but

uplink these are I/Q modulation.


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Slot #0 Slot #1 Slot #14Slot #n

Data1 TPC [TFCI] Pilot

Oneradioframe (10 ms)

20*2k bits (k=0, , 6)

Data2

QPSK modulation,

i.e. 2 bits/symbol

-Downlink DPCH

-Downlink DCH is transmitted on the Downlink DPCH; thus, DPCCH

and DPDCH are time multiplexed .



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Common Pilot Channel

It has pre-defined bit sequence transmitted with a bit rate of 30 Kbps

(Fixed Scrambling code 256)

CPICH is divided into pilot channels:

Primary Common Pilot Channel (P-CPICH)

Secondary Common Pilot Channel (S-CPICH)

Reason for low bit rate as it is transmitted with high power to reduce

the interference.

It is phase reference, must be transmitted in whole cell.


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Primary Common Pilot channel (P-CPICH)

It has following characteristics:

The same channelization code is always used

The P-CPICH is scrambled by primary scrambling code

There is only one P-CPICH per cell

The P-CPICHbroadcast over the entire cell


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Secondary Common Pilot Channel (S-CPICH)

It has following characteristics:An arbitrary channelization code is used SF256

A S-CPICH may scrambled with primary or secondary

scrambling code

There may be zero, one or several S-CPICH per cellA S-CPICH transmitted over the entire cell or part of

the cell



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Primary Common Control Physical Channel (P-CCPCH):

* It has fixed bit rate of 30 Kbps (Fixed Scrambling code 256)

* There are no TPC, Pilot bits and first 256 chips of the slot are

used for the primary and secondary synconization Channel.

* Used to carry the BCH transport channel.


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Synchronization Channel:

This channel used in the cell search procedure. It is divided into

the Primary Synchronization and Secondary Synchronization

Channel

Primary Synchronization ChannelIt carries primary synchronization codes transmitted in each slot of

a radio frame. It is same for cells in the network.

Secondary Synchronization Channel

It consist of the secondary Synchronization codes (SSC). Systemselects the SSC to be transmitted in a slot, based on the

scrambling code group and the slot number.


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Secondary Common Control Physical Channel (S-CCPCH):

It carries FACH and PCH Transport channels.

It has variable bit rate from 30kbps to 1,920 kbps. There

are data bits, pilot bits and optional TFCI bits.

It is transmitted only to smaller are of the cell.



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Paging Indicator Channel (PICH)

It carries indication informing the UE that paging information

is available on the S-CCPCH


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Acquisition Indicator Channel (AICH)

It is used in a random access procedure by the network to indicate

that the RACH preamble was detected.

It has 15 consecutive access slots.

Length of access slot is 5120 chips

Each access slot is further divided into 32 Acquisition indicators

and one part has no transmission.


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HSDPA Channel Structure

RBS ARBS A

High-Speed Downlink Shared Channel HS-DSCH

-High-Speed Physical Downlink Shared Channel HS-PDSCH : DLData

-High-Speed Shared Control Channel HS-SCCH: Scheduling

Associated Dedicated Channel- A-DCH: Data inULand control inDL

RBS BRBS BRBS B

A-DCH

-Multiplexed with High-Speed Dedicated Physical Control Channel:

ACK/NACK + CQI


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HS-DSCH - High Speed Downlink Shared Channel:

* Provides the logical transport mechanism for data transfer.

* Transport channel carrying the user data with HSDPA operation.

HS-SCCH - High Speed Shared Control Channel

* Provides timing and coding information to the User Equipment (UE).

* This allows the UE to listen to the HS-DSCH at the correct time and

using the correct codes to allow successful decoding of received data.


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HS-PDSCH:High Speed Physical Downlink Shared Channel:

* The transport mechanism for the new HSDPA logical channels.

* This channel will be both time and code shared between users

attached to a Node-B.

HS-DPCCH:High Speed Dedicated Physical Control Channel:

Uplink channel that carries packet acknowledgment signaling for

each transportb

lock and a Channel Quality Indicator (CH

I) usedby the Node-B to perform AMC.


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Channel Mapping (1)

The data can be sent through logical layer via different channels in

the transport layer.

And also one transport channel can be sent via different physical

channels.

These selection of channels in the transport and physical layer

depends on the data itself and radio resource management and its

parameters.


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Channel Mapping (2)

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