ISHO –Intersystem handover from WCDMA to Enhanced _100505.pdf · PDF filethe radio...

1 Master’s Thesis seminar ISHO

ISHO – Intersystem handoverfrom WCDMA to Enhanced GPRS

Author: Janne Sipilä

Supervisor: Prof. Sven-Gustaf Häggman

Instructor: M.Sc Ville Salomaa


Agenda

1. EGPRS and WCDMA networks• Architecture• Routing Area and Location Area Update• PDP context

2. ISHO – Intersystem handover• General• ISHO Decision

3. Measurements• Test Cases• Tools and Environment

4. Test results• Delays• Throughput

5. Conclusions and Future Research

6. Extras


WCDMA - EGPRS Network Architecture

Focus on the packet switched network

• SGSN controls the packet switched network

• GGSN is only a gateway to theexternal networks i.e. Internet

• RNC and BSC are responsible forthe radio access network (RAN)

Most important interfaces

• In GERAN and UTRAN• Uu, Um and Abis, Iub

• In the Core Network• Iu-PS, Gb

GERAN, GSM/EDGE Radio Access NetworkUTRAN, UMTS Terrestrial RAN

GGSN, Gateway GPRS Support NodeSGSN, Serving GPRS Support NodeRNC, Radio Network ControllerBSC, Base Station ControllerMSC, Mobile Switching CenterVLR, Visitor Location RegisterHLR, Home Location Register


Routing Area/Location Area Update

• Relationship between LocationArea (LA) and Routing Areas (RA)

• Location Area / Routing Area updateis performed, when moving from oneRA/LA to another

• Separated RA/LA update (Network mode of operation (NMO) II)• LA is updated to the circuit switched

network (to the MSC/VLR)• After that RA is updated to the packet

switched network (to the SGSN)• Gs interface is not used

• Combined RA/LA update (NMO I)• Only RA is updated to the packet

switched network (to the SGSN)• SGSN updates the location to the MSC/VLR

via the Gs interface

LA RA RACell

CellCell

Cell

CellCell

Cell Cell


ISHO – Intersystem handover

The basic functionality:

1. Routing Area Update• After moving under EGPRS

coverage

2. Location change information• 3G-SGSN is resolved by using

old RAI (Routing Area Identity)

3. Downlink packet buffer forwarding• RNC buffers IP packets

4. PDP context update• GGSN is able to route IP packets to the correct SGSN

5. Location Update and Iu-PS release


ISHO Decision - EGPRS

• Mobile is able to measure WCDMA frequencies during the time slots that are not used for data transmission

• Mobile Controlled Cell Reselection• Mobile reselects a WCDMA cell, if the WCDMA signal quality (CPICH

Ec/No) is good enough• Intersystem Network Controlled Cell Reselection (IS-NCCR)

• BSC makes the decision based on the measurement reports received from the mobile

• Mobile is measuring WCDMA quality


ISHO Decision - WCDMA

• Network Controlled Cell Reselection• RNC makes the decision based on the measurement reports received

from the mobile• Compressed Mode should be used to measure EGPRS frequencies


Test Cases

TCP causes extra delays because of it behavior --> both TCP and UDP used• TCP Retransmission timeout, slow start etc.

• FTP DL 100 MB file from ftp server (TCP is used)• ISHO repeated 10 times, 5 times in both directions

• UDP Streaming• Streaming with UDP traffic generator and Helix server• ISHO repeated 10 times, 5 times in both directions

• Different cases (WCDMA network always separated RA/LA update): 1. Separated RA/LA update2. Combined RA/LA update3. IS-NCCR and Separated RA/LA update4. IS-NCCR and Combined RA/LA update


Tools and Environment

• In the terminal• Nemo Outdoor• CommView 5.0• UDP generator• Real One player

• Green route• Speed 0-5 km/h

• Blue route• Speed 50 km/h


ISHO Data Outage Time

Data Outage Time WCDMA -> EGPRS, TCP vr. UDP

0

5000

10000

15000

20000

25000

Data Outage time, combined RAU/LAU Data Outage time, separated RAU/LAU

Dat

a u

uta

ge

tim

e [m

s]

TCP

UDP

Data Outage Time EGPRS -> WCDMA, TCP vr. UDP

0

1000

2000

3000

4000

5000

6000

7000

8000

Data Outage time, with IS-NCCR Data Outage time, without IS-NCCR

Dat

a o

uta

ge

tim

e [m

s]

TCP

UDP

The advantage of using the combined RAU/LAU is really clear

The longer the delay, the biggerthe impact on application level

IS-NCCR causes extra delay beforesending the RRC connection setupto the WCDMA network.

On the application level the extra delayof IS-NCCR is even longer


UDP streaming

• UDP streaming during ISHO• Key frame interval 5 seconds

• Problems 20 seconds after ISHO• Packet were buffered

• Problems were over after 12 seconds

1.33 1.42 1.43 1.44 1.45


Throughput – WCDMA vr. EGPRS

40 seconds

Link adaptationcauses the variationin Modulation andCoding Schemes

MCS


Throughput - pingponging

• Poor WCDMA qualitymay cause downgrade384 kbit/s -> 128 kbit/sin the RAB.

• EGPRS throughputmay be better thanWCDMA

• Bad networkoptimizationmay causepingponging


Conclusions and Future Research

Conclusion

• Data outage time is remarkable for the end user

• Proper parametrization needed

• WCDMA is not always better than EGPRS• ISHO strategy should be planned

Future Research

• ISHO between Outdoor 3G cell and indoor 2G cell• Parameter optimization on cell border -> How to prevent

pingponging?• Ec/No is fluctuating a lot indoors

• IS-NCCR development

• 2G -> 3G trigger development, (specified but not implemented)• RSCP trigger should be implemented

• A too weak WCDMA cell with low RSCP and fluctuating Ec/No can be selected


Questions and comments?

Thank you!

Enjoy the summer!


Extras, KPIs

• Delays

• Throughput

• Success ratesPacket Cell Change Order

MS GERAN/UTRAN

RRC Connection Request

RAB Setup Complete

RRC Connection Setup

Location Area Update Request

Routing Area Update Accept

Routing Area Update Complete

First IP packets

Last IP packets

Inter-SGSN intersystem change delay

Application delay

Bearerdelay

Routing Area Update Request

Location Area Update Accept

Location Area Update Complete

RRC Connection Setup Complete


Extras, parameters

• Only Ec/No trigger was used• WCDMA quality is the reason for performing ISHO from EGPRS to

WCDMA and vice versa• Ec/No levels are really good in the test network

• Parameter optimization not possible

CPICH Ec/No WCDMA cellEc/No level

WCDMA cellEc/No level

Ec/No Threshold=-8 dBEc/No Threshold=-8 dB

time

ReselectEGPRS cell

ReselectEGPRS cell

Reselect WCDMA cell

Reselect WCDMA cell

ReselectEGPRS cell

ReselectEGPRS cell

FDD_Qmin=-6 dBFDD_Qmin=-6 dB


Extras, EGPRS -> WCDMA in generalIntersystem handover EGPRS -> WCDMA using TCP

0

1000

2000

3000

4000

5000

6000

7000

8000

RRCConnection

Request

RRCConnection

Setup

RRCConnection

Setup Complete

LAU Request RAU Request LAU Accept RAU Accept RAB SetupComplete

1st IP packet

Ou

tag

e ti

me

[ms]

Average with IS-NCCR

Average without IS-NCCR

Intersystem handover EGPRS -> WCDMA using UDP

0

1000

2000

3000

4000

5000

6000

7000

RRCConnection

Request

RRCConnection

Setup

RRCConnection

Setup Complete

LAU Request RAU Request LAU Accept RAU Accept RAB SetupComplete

1st IP packet

Out

age

time

[ms]

Average with IS-NCCR

Average without IS-NCCRIS-NCCR causes extradelay


Extras, WCDMA -> EGPRS in generalIntersystem handover WCDMA -> EGPRS using TCP

0

5000

10000

15000

20000

25000

ChannelRequest

FirstImmediate

Assignment

LAU Request LAU Accept RAU Request Packet UplinkAssignment

PacketDownlink

Assignment

RAU Accept LastImmediate

Assignment

1st IP packet

Ou

tag

e ti

me

[ms]

Average combined RAU/LAU

Average separated RAU/LAU

Intersystem handover WCDMA -> EGPRS using UDP

0

2000

4000

6000

8000

10000

12000

14000

ChannelRequest

FirstImmediate

Assignment

LAU Request LAU Accept RAU Request LastImmediate

Assignment

Packet UplinkAssignment

PacketDownlink

Assignment

RAU Accept 1st IP packet

Ou

tag

e ti

me

[ms]

Average combined RAU/LAU

Average separated RAU/LAU

Extra delay caused byseparated RAU/LAU can be seen really well

Time before sendingchannel request is reallylong ~3300 ms


Extra, delays TCP - EGPRS -> WCDMATCP Application delay EGPRS -> WCDMA

0

2000

4000

6000

8000

10000

12000

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15#Intersystem handovers

Dat

a o

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tim

e [m

s]

1st IP packet, with IS-NCCR

1st IP packet, without IS-NCCR

Bearer delay EGPRS -> WCDMA

0

1000

2000

3000

4000

5000

6000

7000

8000

9000


Bea

rer

del

ay [

ms]

Bearer delay, with IS-NCCR

Bearer delay, without IS-NCCR

Inter - SGSN intersystem change time EGPRS -> WCDMA

0

500

1000

1500

2000

2500

3000

3500


Inte

r-S

GS

N in

ters

yste

m c

han

ge

time

[ms]

Inter-SGSN intersystemchange time, with IS-NCCR

Inter-SGSN intersystemchange time, without IS-NCCR


Extra, delays TCP - WCDMA -> EGPRS

Inter-SGSN intersystem change time WCDMA -> EGPRS

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

1 2 3 4 5 6 7 8 9 10 11 12 13 14

#Intersystem handovers

Inte

r-S

GS

N in

ters

yste

m c

han

ge

tim

e [m

s]

Inter-SGSN intersystemchange time, combined

Inter-SGSN intersystemchange time, separated

TCP Application delay WCDMA -> EGPRS

0

5000

10000

15000

20000

25000

30000

1 2 3 4 5 6 7 8 9 10 11 12 13 14#Intersystem handovers

Dat

a o

uta

ge

tim

e [m

s]

1st IP packet, combined

1st IP packet, separated


Extra, delays UDP - WCDMA -> EGPRS

Inter-SGSN intersystem change time WCDMA -> EGPRS

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

1 2 3 4 5 6 7 8 9 10#Intersystem handovers

Inte

r-S

GS

N in

ters

yste

m c

han

ge

tim

e [m

s]

Inter-SGSN intersystemchange time, combined

Inter-SGSN intersystemchange time, separated

UDP Application delay WCDMA -> EGPRS

0

2000

4000

6000

8000

10000

12000

14000

1 2 3 4 5 6 7 8 9 10Data outage time [ms]

#In

ters

yste

m h

and

ove

rs

1st IP packet, combined

1st IP packet, separated


Extra, delays UDP - EGPRS -> WCDMAUDP Application delay EGPRS -> WCDMA

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16#Intersystem handovers

Dat

a o

uta

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tim

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s]

1st IP packet, with IS-NCCR

1st IP packet, without IS-NCCR

Bearer delay EGPRS -> WCDMA

0

1000

2000

3000

4000

5000

6000

7000

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16#Intersystem handovers

Bea

rer

del

ay [

ms]

Bearer delay, with IS-NCCR

Bearer delay, without IS-NCCR

ISHO –Intersystem handover from WCDMA to Enhanced _100505.pdf · PDF filethe radio...

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