Efficient Path Aggregation and Error Control for Video Streaming

Shivkumar KalyanaramanRensselaer Polytechnic Institute

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Efficient Path Aggregation and Error Control for Video Streaming

OMESH TICKOO, Shiv Kalyanaraman, John Woods

Rensselaer Polytechnic Institute (RPI)

Sponsors: ARO, DARPA-NMS, Intel

: “shiv rpi”


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Introduction Motivation: Video over best-effort Internet

Broadband => more access bandwidth End-to-end (E2E) => constraints due to path

congestion Virtual extension of broadband access pipe E2E using

multi-paths

Path Diversity: dimensions Aggregate Capacity Delay diversity Loss diversity Correlations in path performance characteristics

Key: Match inherent content diversity to path diversity


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Motivation: Internet Path Congestion limits E2E bandwidth

Internet

Server Access Link

Client Access Link

Per

form

ance

Access Link Speed

Performance Saturation (even w/ many flows/path)


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Multi-paths?

Overlays or peers can provide path diversity even if multi-paths not available natively in the Internet.

Issue: diversity of performance (b/w, delay, loss), possible correlations…


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Path (Flow) Aggregator/ Multiplexer

Path (Flow) Aggregator/ De-multiplexer

Internet

E2E Broadband Virtual Pipe Abstraction!!

Server Access Link

Client Access Link

Per

form

ance

Access Link Speed

Smart Multi-path Capacity Aggregation (SMCA): Motivation

Performance Scaling


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Time

Lossy

Low Capacity

High Delay/Jitter

Network paths usually have:• low e2e capacity, • high latencies and • high/variable loss rates.

Single path issues: capacity, delay, loss…


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SMCA: Leverage Diversity!

Low Perceived Delay/Jitter

Low Perceived Loss

High Perceived Capacity


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Delay Diversity Unit

Loss Diversity Unit

Network

Receive Buffer

Content

SMCA: Framework


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Paths Ranked by LatencyApplication Data

Low DelayRANK

High DelayRANK

SMCA: Delay Diversity Unit


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Paths Ranked by LatencyApplication Data

Low DelayRANK

High DelayRANK

Early deadline packets mapped to low-delay paths



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Paths Ranked by LatencyTransmit Queue

Low DelayRANK

High DelayRANK

Early deadline packets (in order of rank) mapped to low-delay paths (in order of rank)



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Low DelayRANK

High DelayRANK

Late deadline packets mapped to high-delay paths…

Note: these packets leave the sender roughly at the same time as the early-deadline packets



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Low Delay

High Delay

Consider a delay-based group of paths and the associatedpackets…

SMCA: Delay Diversity Loss Diversity


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Low Delay

High Delay

Consider a delay-based group of paths and the associatedpackets…

SMCA: Delay Diversity Loss Diversity


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Paths Ranked by Loss Raten GOPs

Low LossRANK

High LossRANK

Re-rank Paths within this group based upon packet loss rates

SMCA: Loss Diversity Unit


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I


Low LossRANK

High LossRANK

Enlarged View of Packets (with content labels) and Paths

P

BBPBB



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I


Low LossRANK

High LossRANK

P

BBPBB

Map high priority packets (eg: I-frame packets) to low loss rate rank paths



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I


Low LossRANK

High LossRANK

P

BBPBB

Continue map packets to low loss rank paths based upon priority(Eg: P-frames get the next set of loss-ranked paths)



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I


Low LossRANK

High LossRANK

P

BBPBB

Lowest priority packets get high loss rate paths(within the delay-based group of paths)



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I


Low LossRANK

High LossRANK

P

BBPBB

FEC (unequal FEC) for a GOP mapped within the same delay-group, but mapped to the higher loss paths

SMCA: Loss Diversity Unit + FEC

I-FEC

P-FEC


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SMCA: Performance with increasing number of Paths

Num. Of

Paths

1

2

3

4

5

PSNR (dB)

20.98

22.48

25.42

26.02

28.04

Table 1. Average PSNR Variation with Number of Paths

Background traffic

generatorBackground traffic sink

Content Source Content Sink


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Topology to test delay diversity and loss diversity gains

Content Source Content Sink

Background traffic generator Background traffic

sink

5 paths


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SMCA gains with delay diversity

Avg. Delay(ms)

SMCAPSNR(dB)

PTPSNR(dB)

OPMSPSNR(dB)

300 21.78 18.73 11.03

100 25.12 24.21 19.19

50 28.32 29.46 24.33

30 30.12 31.63 27.96

Table 3. Gains with Delay Variation

SMCA achieves even better performance (than simple multi-path mapping: OPMS) when average delay and jitter is higher


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SMCA gains with loss diversity

Avg. Loss Prob.

SMCAPSNR(dB)

PTPSNR(dB)

OPMSPSNR(dB)

0.4 22.78 20.31 11.64

0.35 26.32 26.86 18.21

0.1 29.03 29.02 24.43

0.05 29.32 31.82 26.06

Table 2. Gains with Loss Variation

SMCA achieves even better performance (than simple multi-path mapping: OPMS) when average loss and loss variations are

higher!


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Summary Multi-path performance diversity can be leveraged E2E

Key: must be mapped to content diversity (Similar to lessons learnt from content-driven unequal FEC protection

vs uniform FEC protection)

Ideas: Map late deadline packets to high latency paths Map higher priority packets to lower loss rate paths (within a delay-

based group of paths) FEC packets sent on paths different from that of associated content

(FEC: lower priority)

Our scheme can scale to handle lots of paths Possible with p2p networks (eg: 10-100 kbps from single path, but 10s

of paths) Does not require MD coding, or high complexity optimization

Documents

Efficient Path Aggregation and Error Control for Video Streaming