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7/27/2019 Handover Optimisations
1/15
Handover Optimisations
February 13 2008
7/27/2019 Handover Optimisations
2/15
HandoverOptimisations
Peter Price
Feb 13 2008
Page 2
Overall Handover Sequence
1. Decision to perform SRNS
Relocation (UE Involved)
11. Routing Area Update
UTSource
RNC
Target
RNC (S-BSS)SGSN
2. Relocation Required
3. Relocation Request
3. Relocation Request Ack
4. Relocation Command
5. Forwarding of data6a. HO FROM UTRAN
COMMAND (25.331)
7. Forward SRNS Context
7. Forward SRNS Context
8. Relocation Detect
9. Relocation Complete
10. Iu Release Command
10. Iu Release Complete
Establishment of Radio
Access Bearers
6b. Handover Access (44.160)MAC
RRC
MAC6c. Physical Infomation (44.160)
[incl. RADIO BEARER
RECONFIGURATION]
6d. RADIO BEARER RECONFIGURATION
COMPLETE (44.118)RRC
Synch to
satellite
(FCCH and
BCCH)
HO
Measurement
Ini t iat ion &
Decis ion
Phase
0. Inter-system Measurements
HO
Preparat ion
Phase
HO
Execut ion
Phase
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HandoverOptimisations
Peter Price
Feb 13 2008
Page 3
Handover Execution Phase
UTATC Source
RNC
Target
S-BSS
6a. HO From UTRAN Command
[Radio Bearer Reconfiguration]
6b.HandoverAccess (onDCH)
MAC6c.Phy
sicalInformatio
n(onPDCH)
6d.RadioBearerReconfigurationComplete(onDCH)
270 ms
50+20 ms
50 ms
4. Relocation Command (from CN)
160+100 ms
Data (Voice) Traffic
RRC
MAC
250+20 ms
8.
Relocation
Detect270 ms
270 ms
250 ms
9.
Relocation
Complete
RRC
Rx Synch to
satellite
(FCCH and
BCCH)
UL/DL Data
Stopped
5. Forwarding of data
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HandoverOptimisations
Peter Price
Feb 13 2008
Page 4
No Activation Time
UAS SASRNC S-BSSU-IMS N-IMS
Handover
Handover to SAS
Handover Access
Physical Information
RBR Complete
Re-Invite
270 mS
270 mS
270 mS
270 mS
250 + 20 mS
50 mS
160 + 100 mS
50 + 20 mS
60 mS
60 mS
OK
Downlink Disruption
1850 mS
Uplink Disruption
2120 mS
Uplink Restarted
Downlink Restarted
270 mS
Synchronisation
7/27/2019 Handover Optimisations
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HandoverOptimisations
Peter Price
Feb 13 2008
Page 5
Contributions to Length of Disruption
+ Satellite Timing 1000 + 120 mS+ SAS processing 50+ Satellite Synchronisation 160 + 100 mS
+ Handover Access propagation 270 mS
+ S-BSS Timing calculation 250 + 20 mS
+ Physical Information Propagation 270 mS
+ Satellite Reconfiguration 320 + 20 mS+ SAS Processing 50 + 20 mS
+ RBR Propagation 270 mS
+ VoIP Reconfiguration DL:390 / UL:660 mS
+ Trigger Re-Invite 60 mS
+ Network reconfiguration 60 mS
+ Downlink RTP propogation 270 mS+ OK propagation 270 mS
+ Uplink RTP propagation 270 mS
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HandoverOptimisations
Peter Price
Feb 13 2008
Page 6
What can we do
+ Problem is sequential nature of activities
+ Network signals Activation Time for Handover
+ Move VoIP reconfiguration forward into Activation Period
+ Use ATC network for VoIP reconfiguration
+ High speed connection low transmission time
+ Close to RNC low propagation time
+ Minor voice disruption due to this reconfiguration
+ Voice maintained to Activation time
+ No VoIP reconfiguration to perform on (slow) SAT network
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HandoverOptimisations
Peter Price
Feb 13 2008
Page 7
Vocoder change in ATC During Activation Period
UAS SASRNC S-BSSU-IMS N-IMS
Handover
Re-Invite
OK
60 mS
60 mS
Activation Handover to SAS
Handover Access
Physical Information
RBR Complete
270 mS
270 mS
270 mS
250 + 20 mS
Synchronisation50 mS
160 + 100 mS
50 + 20 mS
Downlink Disruption
1730 mS
Uplink Disruption
1460 mS
270 mSDownlink Restarted
Uplink Restarted
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HandoverOptimisations
Peter Price
Feb 13 2008
Page 8
Contributions to Length of Disruption
+ Satellite Timing 1000 + 120 mS+ SAS processing 50
+ Satellite Synchronisation 160 + 100 mS
+ Handover Access propagation 270 mS
+ S-BSS Timing calculation 250 + 20 mS
+ Physical Information Propagation 270 mS
+ Satelite Reconfiguration 320 + 20 mS
+ SAS Processing 50 + 20 mS
+ RBR Propagation 270 mS
+ VoIP Reconfiguration DL:270 / UL:0 mS
+ Downlink RTP propogation 270 mS
+ Uplink RTP propagation 0 mS
Significant Downlink Improvement Small Uplink Improvement
660 ms 120 mS
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HandoverOptimisations
Peter Price
Feb 13 2008
Page 9
What else can we do
+ Network signals longer Activation Time for Handover
+ Move Acquistion of Satelite Timing into Activation Period
+ Maintains voice through longest task
+ Reconfigure VoIP in parallel
+ Voice maintained to Activation time
+ Shorter delay in SAT system
+ No VoIP reconfiguration to perform on (slow) SAT network
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HandoverOptimisations
Peter Price
Feb 13 2008
Page 10
Satellite Timing During Activation Period
UAS SASRNC S-BSSU-IMS N-IMS
Handover
Handover to SAS
Handover Access
Physical Information
RBR Complete
270 mS
270 mS
270 mS
250 + 20 mS
50 mS
160 + 100 mS
50 + 20 mS
Synchronisation
Activation
270 mSDownlink Restarted
Uplink Restarted
Downlink Disruption
630 mS
Uplink Disruption
340 mS
Re-Invite
OK
120 mS
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HandoverOptimisations
Peter Price
Feb 13 2008
Page 11
Contributions to Length of Disruption
+ Satelite Reconfiguration 320 + 20 mS+ SAS Processing 50 + 20 mS
+ RBR Propagation 270 mS
+ VoIP Reconfiguration DL:270 / UL:0 mS
+ Downlink RTP propogation 270 mS
+ Uplink RTP propagation 0 mS
Major Downlink Improvement Major Uplink Improvement
1000 + 120 ms 1000 + 120 mS
Optimal Solution
Can do nothing about propagation delays
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HandoverOptimisations
Peter Price
Feb 13 2008
Page 12
Potential Problems
+ Activation Time >1200 mS required
+ Could lose ATC cell before activation time
+ Will not always happen
+ No worse than original case
+ Simultaneous SAT and ATC transmit/receive
+ Give SAT capability to preempt ATC
+ VoIP Disruption
Will result in clicks due to missing packets not total loss
+ VoIP Reconfiguration Disruption
Complete VoIP reconfigure before allowing SAT transmit
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HandoverOptimisations
Peter Price
Feb 13 2008
Page 13
Synchronise SAT Timing Acquistion
UAS SASRNC S-BSSU-IMS N-IMS
Handover
Handover to SAS
Handover Access
Physical Information
RBR Complete
270 mS
270 mS
270 mS
250 + 20 mS
50 mS
160 + 100 mS
50 + 20 mS
Synchronisation
Activation
270 mS
Downlink Restarted
Uplink Restarted
Downlink Disruption
630 mS
Uplink Disruption
340 mS
Re-Invite
OK
120 mS
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HandoverOptimisations
Peter Price
Feb 13 2008
Page 14
Comments on Synchronisation Timing
+ Apparently no difference
+ Allows for IMS timing to be significantly longer
+ PDP Context reconfiguration should also happen in ATC
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HandoverOptimisations
Peter Price
Feb 13 2008
Page 15
Changes Required
+ UMTS AS
+ Modify handling of Handover to allow overlap+ Additional state(s) for handling IMS
+ Additional state(s) for handling PDP Context reconfigure
+ SAT AS+ Additional state(s) to handle Timing Acquistion synchronisation
+ Additional state(s) to handle Activation Time synchronisation
+ UMTS Layer 1 / Layer 2+ ? Support SAT preemption of TX
+ SAT Layer 1+ Preemption control of ATC Layer 1
+ IPC and Proxy
+ Few additional simple messages to process
+ Network+ Configuration of Activation Time
+ Configuration of appropriate measurement thresholds