Project proposal Multi-stream and multi-path audio transmission

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Project proposalMulti-stream and multi-path
audio transmission
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Outline

• Multi-stream audio transmission
• Multi-stream vs. FEC
• Rate and error control
• Multi-stream using path diversity
• Multi-path to improve QoS
• Proposed work

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Multi-stream audio transmission

• The incentives
• Best-effort services vs. strict QoS requirements
  of real-time speech communication, e.g. latency,
  loss, rate variation etc.
• Low bandwidth of the voice stream

• The scheme

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of consecutive lost packet 1 2 3 n
Loss length after recovery (packet) 0 .5 1 n/2-.5
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QoS improvement with multi-stream (1) loss
recovery

• Loss recovery
• With m streams, when having n consecutive lost
  packet, the loss after recovery is
  max(n/m1/m-1,0)
• Stronger protection at the cost of higher data
  rate
• Lower loss rate indicates delay reduction

loss
delay
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QoS improvement with multi-stream (2) delay
reduction

• Reduction of delay and playout rate variation

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Multi-stream vs. FEC (1)
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Multi-stream
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Delay0
FEC protected single-stream Bolot, 96
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Packet Loss
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Reconstructed
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Two copies of payload data Delay1 packet
of consecutive lost packet 1 2 3 n
Loss length after recovery (packet) 0 1 2 n-1
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Multi-stream vs. FEC (2)

• Both add redundancy for data protection
• Pros of multi-stream
• Introduces lower delay for loss recovery
• Provides stronger protection
• Cons of multi-stream
• Overhead from packet header is higher
• Smaller transmission interval

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Joint rate and error-protection control for
multi-stream

• What if network congestion?
• Decreasing audio stream rate does not necessarily
  alleviate the problem

• Add stronger protection against loss and delay
  variation without increasing the total rate
• Solution use more streams with different speech
  codec
• One more issue header compression

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Multi-stream with path diversity

• Packets from source to destination sent
  explicitly over different links to use path
  diversity
• Previous work on path diversity
• Internet path selection Savage, 99
• One paper on reliable video comm. using MSE
  Apostolopoulos, VCIP 01
• Network behavior averaged
• Burst loss converted to isolated loss
• Outage probability decreased

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Multi-stream audio transmission using path
diversity

• Path diversity for real-time speech
  communication reduced variation of network delay
  by selecting path
• Can reduce playout delay and speech rate variation

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Relay
Relay
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Internet traffic
Internet traffic
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The bottleneck
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Path diversity to improve QoS

• Loss recovery stronger protection than single
  path multi-stream
• Reduction of delay and playout rate variation

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Delay reduction (2)

• Adaptive playout scheduling and speech scaling
  makes seamless switching between streams possible

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Proposed work (1)

• For single path multi-stream
• Compare the performance of multi-stream and
  single-stream FEC at the same rate. Find the the
  packet loss/delay jitter behavior by ns
  simulation.
• - Has to use ns simulator must compare the
  two schemes under the same traffic statistics.
  Experiments must be repeatable.
• Study on the optimal rate and error control.

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Proposed work (2)

• For multi-path transmission
• ns simulation based on reasonable network
  topology and traffic model.
• - Network measurement in the real world is
  difficult. Relay server network, opt. path
  selection not available at present.
• Design of the adaptive playout scheduling
  algorithm suitable for multi-stream.
• Study the QoS improvement by using path diversity.