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Design study for multimedia transport protocol in heterog

eneous networksHaitao 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

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Outline• 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

• 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.