adaptive dual-layered bucket synchronization control for distributed virtual environment
DESCRIPTION
APAN NRW 2005. Adaptive Dual-layered Bucket Synchronization Control for Distributed Virtual Environment. JaeYoun Kim, Seokhee Lee and JongWon Kim 2005/8/23 {jykim, shlee, jongwon}@netmedia.gist.ac.kr Networked Media Laboratory Dept. of Information & Communications - PowerPoint PPT PresentationTRANSCRIPT
DEPT. OF INFO. & COMM., GIST
Adaptive Dual-layered Bucket Synchronization
Control for Distributed Virtual Environment
JaeYoun Kim, Seokhee Lee and JongWon Kim2005/8/23
{jykim, shlee, jongwon}@netmedia.gist.ac.kr
Networked Media LaboratoryDept. of Information & Communications
Gwang-Ju Institute of Science & Technology
APAN NRW 2005
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Contents
BackgroundRelated WorkMotivations & ContributionsOverall FrameworkSimulation & Experiment ResultsConclusion
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Background
In these daysAdvances in computer graphics, parallel/distributed system and high-speed networkingDemands on building distributed virtual environments (DVEs) system
ConsistencyEnsure consistent view for each participant over time-varying Network
Tradeoff between responsiveness and consistency
Synchronization algorithmPlayout delay control
Network
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Playout Delay Control
Adaptation efficient playout delay
Event Generation
Event Execution
Small Playout Delay
Large Playout Delay
Large Network
Delay
Network delayNetwork delay
Synchronization delaySynchronization delay
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Related Work
Y. Ishibashi et al. Enhance a virtual-time rendering (VTR) algorithm for DVEs.The synchronization maestro
When the network load is heavy, gradually increases (i.e., delays) the target output time. When the network load becomes lighter, gradually decreases the target output time.
D. Lee et al.Add dynamic playout delay control scheme in bucket synchronization.
Current network state is estimated by measuring how many events have been lost.
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Motivations and Contributions
MotivationsEvent loss rate can not guarantee correct estimation of network state. Event loss when decreasing the playout delay because of skipping.
ContributionsAdaptive dual-layered bucket
Estimates network state based on one-way transmission delay and event loss rate.Decrease the playout delay for silence period in order to prevent from skipping (event loss).
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Synchronization System Model
< System model > < Block diagram >
System modelAll participants use a multicast address for event and report (Tmax)
Each participant is based on bucket-based synchronization layerAdaptation master among participants determine reference playout delay (Rdelay)
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Reference Playout DelayAdaptation master
Group maximum transmission delay (Gmax)Maximum value of Tmax
Smoothed current Gmax ( Cdelay )Filter out short-term fluctuations caused by jitter
Upper target threshold (UTT), Lower target threshold (LTT)Reference playout delay based on UTT and event loss rate
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Dual-layered Bucket Management
Each participantReceives the new playout delay (Rdelay) from adaptation master.
However, does not apply it directly.Prevent event loss when decreasing the playout delay
If there is sending idle time like silence period in DVE systems, apply the playout delay.
ERdelay
Virtual layer
Real layer
S 1 S 2
CRdelay
play out
play out
Event Buffer
Sending idle time
< Dual-layed Bucket management >
Virtual layer: provide guideline for possible playout delay
Candidate playout delay (CRdelay)
Real layer: detect sending idle time like silence period
Established playout delay (ERdealy)
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Dual-layered Bucket Management(cont’)
Insert event
CRdelay is equal to ERdelay
Locate event by ERdelay
on the real buffer layer
End of inserting eventto the real buffer layer
yes
no
CRdelay > ERdelay
Gradually extending ERdelay to CRdelay
yes
no
TRdelay := ERdelay ? BperiodTRdelay is equal
to CRdelay
yes
TRdelay := TRdelay ? Bperiod
Locate event by TRdelay
no
End of inserting eventto the virtual buffer layer
ERdelay : established playout delayCRdelay : candidate playout delay
TRdelay : temporal palyout delay Bperiod: bucket period
Locate event by TRdelay
on the virtual buffer layer
Adapitationcontroller
ERdelay := ERdelay + Bperiod
CRdelay == ERdelay
End of adaptation controller
Calculating new_ERdelay ,
ERdelay := new_ERdelay
CRdelay > ERdelay
no no
yes
Detecting empty bucket
yes
yes
Updating ERdelay
no
Inserting events coming from network
Updating new reference playout delay
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Simulation and Experiment
SimulationGenerate CBR traffic and TCP traffic (FTP) in NS-2 DVE systems( 4 nodes) communicate through single multicast addressCompare playout delay
ExperimentGenerate background UDP traffic (20Mbps~70Mbps) by iperfDVE systems( 2 nodes) communicate through multicast router(CISCO 2600)Compare skipping rate
Topologies
< Experiment>< Simulation NS-2>
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Simulation Result
<Comparison of playout delay>
Network state estimation based on delay and loss
(Proposed scheme)
Network state estimation based on loss rate
Proposed schemeProvides more correct estimation of current network stateGuarantees responsiveness and interactivity of DVEs
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Experiment Result
Comparison of playout delay Similar to simulation result
Event loss rateProposed scheme provides smaller loss rate
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Conclusions
Dual-layered Bucket ManagementProvides more correct network state estimation to determine playout delay.Reduces event loss in event buffer for consistent global state.
Future workImprove the proposed scheme for haptic-based DVEs.
Haptic interface : 1 kHz I/O rate.Haptic interaction : more sensitive to delay and jitter (about 30 ~ 6
0 ms).Current scheme can not guarantee consistency in haptic-based DV
Es.
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Thank You…
Question ?