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
2 Master’s Thesis seminar ISHO
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
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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
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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
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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
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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
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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
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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
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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
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ISHO Data Outage Time
Data Outage Time WCDMA -> EGPRS, TCP vr. UDP
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Data Outage time, combined RAU/LAU Data Outage time, separated RAU/LAU
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TCP
UDP
Data Outage Time EGPRS -> WCDMA, TCP vr. UDP
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Data Outage time, with IS-NCCR Data Outage time, without IS-NCCR
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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
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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
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Throughput – WCDMA vr. EGPRS
40 seconds
Link adaptationcauses the variationin Modulation andCoding Schemes
MCS
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Throughput - pingponging
• Poor WCDMA qualitymay cause downgrade384 kbit/s -> 128 kbit/sin the RAB.
• EGPRS throughputmay be better thanWCDMA
• Bad networkoptimizationmay causepingponging
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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
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Questions and comments?
Thank you!
Enjoy the summer!
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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
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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
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Extras, EGPRS -> WCDMA in generalIntersystem handover EGPRS -> WCDMA using TCP
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RRCConnection
Request
RRCConnection
Setup
RRCConnection
Setup Complete
LAU Request RAU Request LAU Accept RAU Accept RAB SetupComplete
1st IP packet
Ou
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[ms]
Average with IS-NCCR
Average without IS-NCCR
Intersystem handover EGPRS -> WCDMA using UDP
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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
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Extras, WCDMA -> EGPRS in generalIntersystem handover WCDMA -> EGPRS using TCP
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ChannelRequest
FirstImmediate
Assignment
LAU Request LAU Accept RAU Request Packet UplinkAssignment
PacketDownlink
Assignment
RAU Accept LastImmediate
Assignment
1st IP packet
Ou
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[ms]
Average combined RAU/LAU
Average separated RAU/LAU
Intersystem handover WCDMA -> EGPRS using UDP
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ChannelRequest
FirstImmediate
Assignment
LAU Request LAU Accept RAU Request LastImmediate
Assignment
Packet UplinkAssignment
PacketDownlink
Assignment
RAU Accept 1st IP packet
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[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
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Extra, delays TCP - EGPRS -> WCDMATCP Application delay EGPRS -> WCDMA
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1st IP packet, with IS-NCCR
1st IP packet, without IS-NCCR
Bearer delay EGPRS -> WCDMA
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15#Intersystem handovers
Bea
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ay [
ms]
Bearer delay, with IS-NCCR
Bearer delay, without IS-NCCR
Inter - SGSN intersystem change time EGPRS -> WCDMA
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3500
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15#Intersystem handovers
Inte
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[ms]
Inter-SGSN intersystemchange time, with IS-NCCR
Inter-SGSN intersystemchange time, without IS-NCCR
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Extra, delays TCP - WCDMA -> EGPRS
Inter-SGSN intersystem change time WCDMA -> EGPRS
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#Intersystem handovers
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Inter-SGSN intersystemchange time, combined
Inter-SGSN intersystemchange time, separated
TCP Application delay WCDMA -> EGPRS
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1 2 3 4 5 6 7 8 9 10 11 12 13 14#Intersystem handovers
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1st IP packet, combined
1st IP packet, separated
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Extra, delays UDP - WCDMA -> EGPRS
Inter-SGSN intersystem change time WCDMA -> EGPRS
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1 2 3 4 5 6 7 8 9 10#Intersystem handovers
Inte
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Inter-SGSN intersystemchange time, combined
Inter-SGSN intersystemchange time, separated
UDP Application delay WCDMA -> EGPRS
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1 2 3 4 5 6 7 8 9 10Data outage time [ms]
#In
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1st IP packet, combined
1st IP packet, separated
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Extra, delays UDP - EGPRS -> WCDMAUDP Application delay EGPRS -> WCDMA
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16#Intersystem handovers
Dat
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1st IP packet, with IS-NCCR
1st IP packet, without IS-NCCR
Bearer delay EGPRS -> WCDMA
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4000
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16#Intersystem handovers
Bea
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ms]
Bearer delay, with IS-NCCR
Bearer delay, without IS-NCCR