Proprietary and Confidential

IRAT Handover

Northeast RAN Performance

IRAT

• IRAT handover was successfully tested on 01/09/06 in the UMTS FOA network in Queens.

• All UMTS cells except for BQU4363C was locked for testing.

• Call was originated on BQU4363C and then handover to BQ04744B was performed.

IRAT Handover – Site Location

3G Cell

BQU4363C

2G Cell

BQ4744A

and

BQ4744B

Site Address:

77-16 101st Ave,

Queens, NY

For 3G: Only BQU4363C

needs to be on-air and

the remaining cells

should be off.

UMTS & GSM Cell Information

3G

Sector Scrambling Code Cell ID LAC RNC MSC

BQU4363A 76 28631 52153 NYRNC003 NYMSS900

BQU4363B 84 28632 52153 NYRNC003 NYMSS900

BQU4363C 92 28633 52153 NYRNC003 NYMSS900

2G

Sector BCCH BSIC Cell ID LAC BSC MSC

BQ04744A 594 45 27441 32121 112 NYMSC04

BQ04744B 601 07 27442 32121 112 NYMSC04

BQ04744C 606 62 27443 32121 112 NYMSC04

Active Set – Ec/Io

UMTS Call Initiated

Handover

completed

to GSM

Handover Command

from RNC to UE

RSCP: -102dBm

Ec/Io: -5 dB

UE starts

compressed mode

measurements to

start measuring

GSM neighbors

RSCP: -96dBm

Ec/Io : -4 dB

Event 2d: When estimated quality

of currently used freq is below a

certain threshold, UE sends a

event 2d to SRNC, which on

receiving this message asks the

UE to set up event 3a

IRAT Events

Contd…

RNC send a Physical

channel reconfiguration

message to UE which tells

the UE to enter

compressed mode to

measure GSM neighbor

cells.

The method to

induce

compressed

mode is SF/2

IRAT Events Contd..

Contd…

IRAT Events Contd..

Event 3a -> Event trigger for IRAT; RNC asks

UE to report GSM neighbors fulfilling a

minimum criteria for signal quality

Time to trigger: 100 s

UE sends a

measurement report to

RNC reporting the RSSI

measurements of all the

GSM neighbors fulfilling

the criteria

IRAT Events Contd..

Handover to GSM

command sent by

RNC to UE

IRAT handover successfully completed. A more detailed analysis

will be done for parameter optimization and to control IRAT

boundaries as part of FOA

IRAT Analysis – RNC Log

• The figure shows the IRAT handover sequence

• A brief analysis of the corresponding RNC log is attached with all the messages showing the successful IRAT HO.

Path Forward

• For this IRAT testing, the UMTS network was changed to 2 digit MNC – the same as the 2G network.

• After the testing, the UMTS network was reverted back to 3 digit MNC.

• The way forward is to standardize the MNC length to ensure that both UMTS and GSM networks have the same length MNC for successful IRAT handovers.

Appendix

Tables illustrating the concept of

Handover events 2d and 3a

related to IRAT.

Taken from Ericsson ALEX

library