Basic Concept of 3G Network.pptx

7/29/2019 Basic Concept of 3G Network.pptx

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Basic Concept of 3G Network


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3G rel99 Architecture (UMTS)

- 3G Radios

SS7

IP

BTS

BSCMSC

VLR

HLRAuC

GMSC

BSS

SGSN GGSN

PSTN

PSDN

CN

CD

GcGr

Gn Gi

Abis

Gs

B

H

BSS Base Stat ion System

BTS Base Transceiver Station

BSC Base Station Controller

RNS Radio Network System

RNC Radio Network Controller

CN Core Network

MSC Mobile-service Switching Controller

VLR Visitor Location Register

HLR Home Location Register

AuC Authentication Server

GMSC Gateway MSC

SGSN Serving GPRS Support Node

GGSN Gateway GPRS Support Node

AE PSTN

2G MS (voice only)

2G+ MS (voice & data)

Gb

3G UE (voice & data)

Node B

RNC

RNS

Iub

IuCS

ATM

IuPS


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WCDMA Specification


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4

Spreading process in WCDMA

1st Step: Channelization Variable Rate Spreading ( According to user data rate)

2nd Step: Scrambling Code Fixed Rate Spreading (3,840 Kchips)

S

Channelization

Code

Scrambling

Code

3,840 Kcps

Coding

&

Interleaving


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5

Downlink (NodeB to UE )

Scrambling Code:Identifies cell (sector). Channelization Code:Identifies user channels in cell (Sector).

Scrambling Code A

Scrambling Code B

Scrambling Code C

Channelization

Code 1

Channelization

Code 2 Channelization

Code 3

ChannelizationCode 1 Channelization

Code 2

Channelization

Code 2

Channelization

Code 1


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6

Up Link (UE to NodeB )

Scrambling Code:Identifies user terminal.

Channelization Code:Identifies channels in user terminal.

Scrambling Code A

Scrambling Code B

Scrambling Code C

Channelization

Code 1

Channelization

Code 2

Channelization

Code 1

ChannelizationCode 1


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Orthogonal Variable Spreading Factor [OVSF] codes are the channelization codes used for

signal spreading in the uplink and downlink


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8

The code used for scrambling of the uplink Channels may be of either long

or short type, There are 224 long and 224 short uplink scrambling codes.

Uplink scrambling codes are assigned by higher layers.

For downlink physical channels, a total of 218-1 = 262,143 scrambling

codes can be generated. Only scrambling codes k = 0, 1, , 8191 are used.

In the downlink direction 512 of scrambling codes are used to identify the

cells in the downlink so downlink planning is required


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Different Handover in 3G

1. Intra-system handovers

MS handover within one cell between different sectors: Softer handover

MS handover between different BS:

Soft handover

Hard handover

2. Inter-frequency handovers

Hard handover

3. Inter-system handovers

Handover between WCDMA GSM900/1800: Hard handover

Handover between WCDMA/FDD TDD: Hard handover


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Intra-system handovers

1. Intra-system handovers

I. Softer handover

II. Soft handoverIII. Hard handover


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Softer Handover

Softer handover refers to handover between cells with same frequency

and in same nodeB.

As we can say HO between Cell A to Cell B of SITE0001 at f1 or f2


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Soft Handover

Soft handover refers to adding a new serving cell and deleting the old one

after stabilization. Services continue in the handover without any

interruption. Its also known by term make before break.


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Hard Handover

Hard handover refers to deleting the old serving cell and then adding a

new serving cell. Services break off during the handover. Its also known by

term break before make.


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Events in 3G

Event Description

Event 1AQuality of target cell improves, entering a report range of relativelyactivating set quality

Event 1BQuality of target cell decreases, depart from a report range of relativelyactivating set quality

Event 1CThe quality of a non-activated set cell is better than that of a certain activatedset cell

Event 1D Best cell generates change

Event 1E Quality of target cell improves, better than an absolute threshold

Event 1F Quality of target cell decreases, worse than an absolute threshold

Event correlative to soft handover


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Events in 3GEvent Description

Event 2A Best band generates change

Event 2BQuality of currently-used band is worse than an absolute threshold andthat of non-used band is better than an absolute threshold

Event 2C Quality of non-used band is better than an absolute threshold

Event 2D Quality of currently-used band is worse than an absolute threshold

Event 2E Quality of non-used band is worse than an absolute threshold

Event 2F Quality of currently-used band is better than an absolute threshold

Event correlative to hard handover


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Events in 3G

Event Description

Event 3AQuality of currently-used UTRAN operator is worse than an absolutethreshold and quality of other radio systems is better than an absolutethreshold

Event 3B Quality of other radio systems is worse than an absolute threshold

Event 3C Quality of other radio systems is better than an absolute threshold

Event 3D Best cell in other systems generates change

Event correlative to handover between systems


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Common Pilot Channel (CPICH)

The CPICH is a fixed rate (30 kbps, SF=256) downlink physical channel that carries a pre-defined bit

sequence.

There are two types of Common pilot channels, the Primary and Secondary CPICH. They

differ in their use and the limitations placed on their physical features

Primary CPICH

Secondary CPICH


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Primary CPICH

An important area for the primary common pilot channel is the measurements for the

handover and cell selection/reselection. The use of CPICH reception level at the terminal for

handover measurements has the consequence that, by adjusting the CPICH power level, the

cell load can be balanced between different cells. Reducing the CPICH power causes part of

the terminals to hand over to other cells, while increasing it invites more terminals to hand

over to the cell, as well as to make their initial access to the network in that cell.

The Primary Common Pilot Channel (P-CPICH) has the following

characteristics:

The same channelization code is always used for the P-CPICH.

The P-CPICH is scrambled by the primary scrambling code.

There is one and only one P-CPICH per cell.

The P-CPICH is broadcast over the entire cell.


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Secondary CPICH

Secondary CPICH may be phase reference for the secondary CCPCH.

A Secondary Common Pilot Channel (S-CPICH) has the following

characteristics:

An arbitrary channelization code of SF=256 is used for the S-CPICH.

A S-CPICH is scrambled by either the primary or a secondary scrambling code.

There may be zero, one, or several S-CPICH per cell.

A S-CPICH may be transmitted over the entire cell or only over a part of the cell.


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Area type DenseUrban

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 moves

further away from the Node B

User levels - Demand for mobileservices will increase, leading tomuch greater user densities

Fast DataUsers

Voice andSlow Data

Users

average projected coverage

WCDMA Cell Coverage

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Basic Concept of 3G Network.pptx