Design study for multimedia
transport protocol in
heterogeneous networks
Haitao Wu; Qian Zhang; Wenwu Zhu;
Communications, 2003. ICC '03. IEEE International
Conference on , Volume: 1 , 2003
Page(s): 567 -571
Group Meeting Presenter: Sze-Horng Lee
2003.10.15 NCNU CSIE MCL Network Group
1
Outline
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•
•
•
Introduction
Related Work
Multimedia Transport Protocol
Window Based EWMA filter with two
weights
• Simulation results and Analysis
• Conclusions
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Introduction
• The adaptability of transport layer is
based on its sensibility to the changing
network conditions.
• For a TCP connection, it uses slow start
to probe available network bandwidth
and packet los is regarded as the
congestion indication.
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Introduction
• TCP Friendly Rate Control (TFRC) is an
unreliable transport protocol, which is
friendly to TCP by using TCP throughput
equation in rate control.
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Related Work
• Previous work on wireless network focus
on improving TCP performance includes
end-to-end approach, split connection and
link layer approaches.
• TFRC, AIMD, WTCP
• A packet interval measurement approach
• Packet-pair technique
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Multimedia Transport Protocol
• MMTP is a receiver based rate control
protocol
• Receiver is responsible for monitoring
the receiving rate by window based
EWMA filter, detecting bandwidth
transition and feeding back the
information to sender for rate adjustment.
• round
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Multimedia Transport Protocol
Sender functionality
• the RTT value will be used to increase the
sending rate slowly.
• 2 x RTT value lost  sending rate x 0.75
• TFRC  0.5 x sending rate
• slow start to probe available bandwidth
•△ = L / rtt_ (L: packet size, rtt_ :RTT)
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Fig.1 Round based rate control prototype
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Multimedia Transport Protocol
Receiver functionality
• if sending rate > receiving rate (2 △), it
feedbacks to make the sender slow down.
•2 filters, packet-pair (PP), available
bandwidth (AB)
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Fig.2 Bandwidth measurement in MMTP
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Window Based EWMA filter
with two weights
• Weight old ↑  stability
• Weight new ↑ flexibility
• 3-sigma rule:
µ ± 3cx
µ : sample mean
3cx : sample standard deviation
• MR : moving range btw | xi – xi-1|
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A general form of EWMA filter is in the
following equation:
the control limit is yi-1 ± 3MRi-1/d2
yi-1 is last filtered value
d2 estimates the standard deviation of a
sample given its range.
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Window Based EWMA filter
with two weights
• if fall within 3-sigma limits, system state
 followed, α=0.9 and β= 0.6
• if fail, kept in system output, system state
 lost
• windows  fixed size W
• α=0.1
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Simulation results and Analysis
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•
•
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ns-2.1b7a
IEEE 802.11 DCF
data packet length = 500bytes
feedback packet size form MMTP =
50bytes
• each stream is backlogged throughout the
duration.
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Fig.3 Simulation Topology
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Performance under
bandwidth transitions
• A rate measurement based protocol reacts
much quickly than an equation based
protocol, because equation based protocol
relies on packet loss count to detect the
congestion or bandwidth changes and to
calculate the new rate.
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Performance under
bandwidth transitions
• 4 streams
• Starts at 2s, 5Mbps to 500kbps at 22s and
changes back at 42s.
• 5 streams, interval = 40s
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Fig.4 Throughput comparison for x=25ms
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Fig.5 Throughput comparison for x=50ms
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n = stream number
Gi = throughput of a stream
ri = weight
In out cases, ri= 1 for all stream
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Table 1. Simulations results under transitions
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Performance and fairness
under stable conditions
• 10 streams
• Warm up time is 40s, duration is 100s.
• MMTP needs larger feedback packets.
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Table 2. Simulations results under stable
conditions
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Conclusions
• Using online passive bandwidth measuring
results in rate control algorithm, which
consists of the bottleneck capacity
measurement and network available bandwidth
measurement.
• A window based EWMA filter, which has two
weights to achieve stability and flexibility at
the same time.
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