handover optimisations

7/27/2019 Handover Optimisations

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Handover Optimisations

February 13 2008


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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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Peter Price

Feb 13 2008

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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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Peter Price

Feb 13 2008

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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


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Peter Price

Feb 13 2008

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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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Peter Price

Feb 13 2008

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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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Peter Price

Feb 13 2008

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Vocoder change in ATC During Activation Period


Handover

Re-Invite

OK

60 mS

60 mS

Activation Handover to SAS

Handover Access


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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+ 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



+ Downlink RTP propogation 270 mS


Significant Downlink Improvement Small Uplink Improvement

660 ms 120 mS


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Peter Price

Feb 13 2008

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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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Peter Price

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Satellite Timing During Activation Period


Handover

Handover to SAS

Handover Access


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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+ Satelite Reconfiguration 320 + 20 mS+ SAS Processing 50 + 20 mS



+ Downlink RTP propogation 270 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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Peter Price

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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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Synchronise SAT Timing Acquistion


Handover

Handover to SAS

Handover Access


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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Peter Price

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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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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

handover optimisations

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