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Multiple Sender Distributed Video Streaming

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Addresses the problem of video streaming over best effort, packet ... In Kazaa, senders send contiguous blocks of data. Duplication of packets cannot occur. ... – PowerPoint PPT presentation

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Title: Multiple Sender Distributed Video Streaming


1
Multiple Sender Distributed Video Streaming
  • Nguyen, Zakhor
  • IEEE Transactions on Multimedia
  • April 2004

2
Agenda
  • Motivation
  • Proposed Approach
  • Rate Allocation Algorithm
  • Packet Partition Algorithm
  • Experimental Results
  • Conclusion

3
Motivation
  • Addresses the problem of video streaming over
    best effort, packet-switched networks.
  • Streaming of video requires high bit rates.
  • Packet loss and delay due to network congestion.

4
Aim of the proposed approach
  • Increase throughput in order to meet the high bit
    rate demands.
  • Reduce the probability of packet loss.

5
Proposed approach
  • Simultaneous video streaming from multiple
    senders to a single receiver.
  • Employs a receiver driven protocol
  • The distributed streaming protocol consists of a
    Rate Allocation Algorithm (RAA) and a Packet
    Partition Algorithm (PPA)

6
Assumption
  • The bandwidth bottleneck is not at the last hop.

7
Rate Allocation Algorithm (RAA)
  • Run at the receiver.
  • Determines the optimal sending rate for each
    sender.
  • Uses information about available network
    bandwidth, channel characteristics.
  • Receiver can also redistribute rates among
    existing senders.

8
Packet Partition Algorithm (PPA)
  • Run at the senders.
  • Ensures that every packet is sent by one and only
    one sender.

9
The distributed streaming framework
10
RAA A closer look
  • Goal of RAA is to determine how to split the
    total video rate among M senders in order to
    minimize the probability of packet loss.
  • Used in conjunction with Forward Error Correction
    (FEC).

11
FEC
  • Used at the receiver side for recovering lost
    packets.
  • A FEC block consists of a number of packets.
  • N packets in a block, K data packets, N-K
    redundant packets.
  • For recovery, any K packets in a block must be
    received.

12
RAA (contd.)
  • RAA used with FEC reduces packet loss as compared
    to single route streaming.

13
RAA (contd.)
  • Notations
  • N Total no. of packets in FEC block
  • K No. of data packets in FEC block
  • NA Number of packets sent by sender A in a FEC
    block
  • NB Number of packets sent by sender B in a
    FEC block

14
Rate Allocation Formula
  • We seek to minimize the probability of
    irrecoverable loss given by
  • NA NB j
  • C(K,N0,N1) ? ? P(A,i, NA)P(B,j-i,NB)
  • j NK1 i0

15
Packet Partition Algorithm (PPA)
  • Goal of the PPA is to determine which packets
    should be sent by which senders in order to
    prevent duplicate packets and minimize start up
    delay.

16
Minimization of start-up delay in PPA
  • In Kazaa, senders send contiguous blocks of data.
    Duplication of packets cannot occur.
  • In PPA, senders send interleaved packets. Reduces
    start-up delay, but packets may be duplicated.

17
Avoiding Packet Duplication in PPA
  • Each sender independently arrives at the same
    decision as to which packet to send next.
  • All senders use the same information to choose
    the next packet to send.
  • This information is sent to all senders by the
    receiver.

18
How PPA works
  • The receiver sends identical control packets to
    all senders.
  • The control packet contains
  • RTT of all senders.
  • Sending rate for all senders.
  • Starting sequence number.

19
How PPA works (contd.)
  • Each of the senders uses the information in the
    control packet to compute the estimated arrival
    time for packet k
  • The time difference between the arrival and
    playback time of packet k is then computed.
  • The sender that maximizes this time difference is
    chosen to send packet k

20
Illustration of how PPA works
21
Choosing the starting sequence no.
22
Irrecoverable loss probability for various FEC
levels as a function of bad times
23
Optimal sending rate for route A as a function of
bad times for route B
24
Irrecoverable loss probability ratio as a
function of average bad time of route B
25
Irrecoverable probability as a function of
sending rate of sender A
26
Number of lost packets per FEC block for a single
sender
27
No. of lost packets per FEC block for two senders
28
Throughput of two senders
29
Sequence No. difference of two consecutive
received packets
30
Conclusion
  • Inaccuracy in parameter estimation can skew the
    results.
  • Cannot protect against packet loss in case of
    coinciding congestion intervals on different
    routes.
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