1 Design study for multimedia transport protocol in heterogeneous networks Haitao Wu; Qian Zhang; Wenwu Zhu; Communications, ICC '03. IEEE International Conference on, Volume: 1, 2003 Page(s): Group Meeting Presenter: Sze-Horng Lee NCNU CSIE MCL Network Group

2 Outline Introduction Related Work Multimedia Transport Protocol Window Based EWMA filter with two weights Simulation results and Analysis Conclusions

3 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.

4 Introduction TCP Friendly Rate Control (TFRC) is an unreliable transport protocol, which is friendly to TCP by using TCP throughput equation in rate control.

5 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

6 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

7 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)

8 Fig.1 Round based rate control prototype

9 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)

10 Fig.2 Bandwidth measurement in MMTP

11 Window Based EWMA filter with two weights Weight old ↑  stability Weight new ↑  flexibility 3-sigma rule: µ ± 3c x µ : sample mean 3c x : sample standard deviation MR : moving range btw | x i – x i-1 |

12 A general form of EWMA filter is in the following equation: the control limit is y i-1 ± 3MR i-1 /d 2 y i-1 is last filtered value d 2 estimates the standard deviation of a sample given its range.

13 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

14 Simulation results and Analysis ns-2.1b7a IEEE DCF data packet length = 500bytes feedback packet size form MMTP = 50bytes each stream is backlogged throughout the duration.

15 Fig.3 Simulation Topology

16 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.

17 Performance under bandwidth transitions 4 streams Starts at 2s, 5Mbps to 500kbps at 22s and changes back at 42s. 5 streams, interval = 40s

18 Fig.4 Throughput comparison for x=25ms

19 Fig.5 Throughput comparison for x=50ms

20 n = stream number G i = throughput of a stream r i = weight In out cases, r i = 1 for all stream

21 Table 1. Simulations results under transitions

22 Performance and fairness under stable conditions 10 streams Warm up time is 40s, duration is 100s. MMTP needs larger feedback packets.

23 Table 2. Simulations results under stable conditions

24 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.