2G vs3G Comparison Essentials

Multiwireless Sdn BhdPrepared by: Huzaini

Basic Fundamental

Course

BASIC CONCEPT

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22 May 20102

2G - GSM 3G - WCDMA

Frequency

FDD

Code

CDMA

time

frequency

time

frequency

Time

TDD

Maxis’ WCDMA frequencies*:f1 10686 (DL) / 9712 (UL) - primary

f2 10637 (DL) / 9687 (UL)

f3 10662 (DL) / 9736 (UL)

frequency

structure Network Element:

MSC

SGSN

RNC

NodeB

NodeB

NodeB

iubiuCS

iuPSUE

UEuu

* Note: Different operator have different frequencies and different strategy advice by Vendor (Huawei/Ericsson/NSN)

For CS

For PS

Bandwidth = 5MHzbandwidth

Chip rate = 3.84 Mchip/schip rate

Frame length = 10 msframe

Maxis’ GSM frequencies:900MHz, 1800MHz

frequency

Bandwidth = 200kHzbandwidth

SCRAMBLING CODES (SC)

Spreading Factor User DL Bit Rate (kbps) User UL Bit Rate (kbps)

8 384 128

16 128 64

32 64 32

64 32 16

128 16 8

3

SC: 1

SC: 17

Scrambling Code:• Using pseudo noise (PN) codes

• Used to differentiate cells in the downlink (DL)

• Range is 0 - 512

SC

SC: 9, Service: CS Call

DL Channelization code: C128,5

Spreading factor: 128

User bit rate: 12.2 kbps

SC: 9, Service: PS Download

DL Channelization code: C8,2

Spreading Factor: 8

User bit rate: 384 kbps

Channelization Code:• Using Orthogonal Variable Spreading Factor

(OVSF) codes

• Fully orthogonal, i.e. do not interfere with

each other

• Used to separate different users/cell

• Limited codes per cell

• Once a code is chosen, any codes on the

same branch above or below the used code

cannot be used (refer diagram below)

SF

SC: 418

C8,2C16,3

C32,5

C32,6

C64,9

C64,10

C64,11

C64,11

used

SC: 9

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22 May 2010

HANDOVER (1)

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22 May 20104

2G

Cell1

3G

Cell1

f1

IRA

T

Dedic

ate

d o

r id

le (

resele

ction)

Idle

(re

sele

ction)

3G

Cell2

f1

SOFT HANDOVERActive Set:Up to 3 cells in soft handover (sHO), i.e. 3 AS. This means

a UE can be served by up to 3 cells at the same time.

Note that 3 AS equals to using 3 cells’ resources at the

same time.

AS

Things to defineMotorola: inter_rat_enabled, 2g>3g neighbours1

Ericsson: qsi, 2g>3g neighbours

Parameter

2G vs 3GRxLev = Signal strength = RSCP

RxQual = Signal Quality = Ec/Io

BCCH/ARFCN = Frequency Channel / Code = Scrambling Code (SC)

Monitored Neigbour / Detected NeighbourMonitored Neighbour (MN): Neighbour already

defined2, can be added as an AS if criterion is met

Detected Neighbour (DN): Neighbour not defined in the

neighbour list, need to be added TWO-WAY if it is a

valid missing neighbour. A DN whose RSCP is too

close to the strongest server and not added as a

neighbour will become an interferer.

MN/DN

Add

Don’t Add

SOFT HANDOVER

IRAT

Dedicated

TEMS Snapshot

3G

Cell3

f2H

AR

D H

AN

DO

VE

R

Dedic

ate

d

Inte

r-frequency H

O

Intra-frequency HO

HA

RD

HA

ND

OV

ER

HANDOVER(2)

Parameter Meas. Q Eric NSN

e1a Ec/No 3 3

e1b Ec/No 5 6

e1c Ec/No 1 2

e1d Ec/No 7.5 4

e2d rscp -104 -102

e2f rscp -101 -97

e3a rscp -95 -100

5

Event 1a - A Primary CPICH enters

the Reporting Range e1a

Event 1b -A Primary CPICH leaves

the Reporting Range e1b

Event 1c - A non-active primary

CPICH becomes better than an

Active Primary CPICH

e1c

Event 1d - Change of Best Cell e1d

Event 2d - The estimated quality of

the currently used frequency is

below a certain Threshold

e2d

Event 2f - The estimated quality of

the currently used frequency is

above a certain threshold

e2f

Event 3a - The Estimated Quality of

the Currently Used UTRAN

Frequency is below a Certain

Threshold and the Estimated

Quality of the Other System is

above a Certain Threshold

e3a

Maxis default values

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22 May 2010

OPTIMIZATION

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22 May 20106

TEMS Snapshot

RSCP = COVERAGEIt is equivalent to RxLev in GSM

Coverage

Ec/No = QUALITYIt is equivalent to RxQual in GSM. Very important to

optimize network to have good quality (>-12dB)

Quality

OPTIMIZATION CONCEPT• To have best Ec/No (not necessarily RSCP) by

minimizing other cell’s interference. This means

optimizing a cell’s coverage with balancing between

RSCP and Ec/No.

• Ideally, at one point in time, you should have only 1AS

only. But for practicality, it should be less than 3 cells

(including best server) within 6dB of the best server’s

RSCP (above example would have 4 cells)

3G Opti METHODS OF OPTIMIZATION• Tilting of overshooting site

• Power down of overshooting site with max tilts

• Neighbour addition of DN’s

• Reengineering, e.g. antenna swing

Methods

Common Pilot ChannelUse for channel estimation reference at the terminal;

scrambled with cell specific primary SC; DL channel with a

fixed rate of 30 kbps or SF256

CPICH

RESOURCES & CAPACITY

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22 May 20107

NODE B

E1 CAPACITYType: Site-level

Note: This resource is for

signaling and traffic between

Node B and RNC (highest priority

among all resources mentioned

here).

Congestion Resolution: E1

upgrade

IUB

CHANNEL ELEMENTType: Site-level

Note: This resource shared between

sectors within one NodeB. It is used to

process different type of services, e.g.

CS, PS, HSDPA, 1 CE = 1 Voice Call

Congestion Resolution: Channel card

activation or addition

CE/CHC

POWERType: Cell-level

Note: Output power on

the downlink is shared

between UE’s.for their

respective traffic

Congestion Resolution:

Power upgrade or 2nd

Carrier

POWER

CODEType: Cell-level

Note: This is referring to the

channelization/OVSF code

resource which is one per

service (more codes for

HSDPA)

Congestion Resolution: 2nd

Carrier

CODE

RNC

RF Tools

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22 May 20108

TEMS Investigation

NEMO

Genex

Couei

ROMES Rodge & Schwarz

SwissQual

…

…

…

…

9

Basic Tems Investigation 7.1.3 Overview

What to focus on 3G tems?

Line Chart WCDMA/GSM

Radio Parameters WCDMA

Serving/ Active Set-

Neighbours WCDMA

Map

Layer 3

Layer 2

Radio Parameters GSM

Current Channel GSM

Serving – Neighbors By

Band GSM

10

Line Chart WCDMA/GSM

CPICH RSCP

UM

TS

GS

M

RxLevSub

UE Tx Power/

SIR/ SIR

Target/ Ec/NoRxQualSub

IRAT from UMTS to

GSM network

SQI

11

Radio Parameters WCDMA

Tx Power- UE

transmit power in

dBm. Valid only in

connected mode.

• This window presents a collection of information elements describing the status of the radio link and some

more general radio conditions.

UTRA Carrier RSSI-

Total energy

measured by the

UE in the 5 MHz

frequency band.

SIR-Signal-to-

interference ratio

measured by a UE

on the DPCH.

SQI- Speech Quality Index for

WCDMA. The range is different

depending on the AMR speech

codec mode. The maximum SQI

values are as follows:

12.2 kbit/s: 30 dBQ

10.2 kbit/s: 28 dBQ

7.95 kbit/s: 28 dBQ

7.40 kbit/s: 27 dBQ

6.70 kbit/s: 27 dBQ

5.90 kbit/s: 24 dBQ

5.15 kbit/s: 21 dBQ

4.75 kbit/s: 19 dBQ RSCP

Ec/No!!RSSI =

!!Target SIR should lower

than SIR- UE will power down

12

Serving/ Active Set- Neighbours WCDMA

Active Set

Monitored

Neighbours

Detected

Neighbours

13

Layer 3/ Layer 2

Layer 2 messages

Indicate the basic call event.

Example: Call setup, Handover, Dropped Call, Cell Reselection

etc.

Layer 3 messages

Indicates the system information & check the health of the call.

14

Case Studies

1. Voice Call

IRAT

Coverage (Low RF)

Missing Neighbour (Detected Neighbour)/ Overshooting Cell

2G-3G Idle Mode Reselection

3G-2G Idle mode Reselection

2. Video Call

What different between Voice call and Video call?

What is MOC and MTC?

3. Packet Service (PS)

What is PS?

PS vs Car speed during drive test?

15

IRAT

The IRAT threshold:

Base on Ec/No= -12

OR

Base on RSCP= -104 dBm

16

Coverage (Low RF)

Low RF in 3G?

AS/ MN with average RSCP < -100 dBm for

outdoor & with average Ec/No <-10

17

Missing Neighbour (DN)/ Overshooting Cell

DN/ Overshooting Cell?

It will be captured as DN with good RSCP

& Ec/No.

Based on local knowledge, the RF is

needed or it is an overshooting cell.

18

3G-2G Idle Mode Reselection

How?

Based on Ec/No threshold.

19

2G-3G Idle Mode Reselection

How?

Inter_rat parameter has to be enabled in 2G

cell.

A few parameters to be changed in 2G

system in order for reselection.

20

Video Call

How to differentiate between Voice Call/

Video Call?

DL Spreading Factor= 32 [ DL 64 kbps]

On video call, no IRAT.

Why? It is utilizing the CS64 RAB bearer.