Rugby2004

Streaming Video over aWireless NetworkSo what is the problem!!: 

Streaming Video over a Wireless Network So what is the problem!! WPI CS Research Rugby Bob Kinicki November 30, 2004

CC-Wireless Rugby Team: 

CC-Wireless Rugby Team prop hooker Feng Li Mingzhe Li wireless measurement wireless bandwidth estimation flanker flanker Jae Chung Yubing Wang congestion control retransmissions scrumhalf Robert Kinicki protocols flyhalf Huahui Wu weak side wing FEC Emmanuel Agu low-level wireless fullback Mark Claypool multimedia

Outline: 

Outline Motivation – the Future Streaming Video over Wireless What Problems? Background Layered network architecture Networking ‘religious’ tenets Measurement and Tools Streaming multimedia primer Introduction to wireless networks Focus: Wireless Bandwidth Estimation Discussion ??

Streaming Video: 

Streaming Video Video Frames

Streaming Video over Wireless: 

Streaming Video over Wireless Video Frames Wired network AP

Networking Protocol Layers: 

Networking Protocol Layers Application Layer: Real Player,Windows Media Player, MPEG Transport Layer: TCP, UDP Network Layer: IP Data Link Layer (MAC): 802.3, 802.11b, 802.11g

Measurement and Tools: 

Measurement and Tools

Wireless Streaming Multimedia Lab Topology : 

Wireless Streaming Multimedia Lab Topology Slide courtesy of Mingzhe’s PEDS presentation Monday October 25,2005

Wireless Measurement Study: 

Wireless Measurement Study

Preliminary Wireless Measurements: 

Preliminary Wireless Measurements Application Layer Network Layer Data Link Layer

Video Streaming Choices: 

Video Streaming Choices Media Player or Real Player TCP or UDP Single layer encoding or multilayer encoding

MediaPlayer™ vs. RealPlayer™ A Comparison of Network Turbulence: 

MediaPlayer™ vs. RealPlayer™ A Comparison of Network Turbulence

Real vs WMP Playout Rate: 

Real vs WMP Playout Rate RealPlayer buffers at a higher rate

Video Compression Standard: 

Video Compression Standard MPEG Popular compression standard Intra-compression and inter-compression Three types of frames: I, P and B Group Of Pictures (GOP)

340 Kbps Clip - Bottleneck Capacity 725 Kbps: 

340 Kbps Clip - Bottleneck Capacity 725 Kbps andlt; 0.001 packet loss After 15 seconds TCP Friendly?

548 Kbps Clip - Bottleneck Capacity 725 Kbps: 

548 Kbps Clip - Bottleneck Capacity 725 Kbps ~ 0.003 packet loss for WSM ~ 0.006 packet loss for TCP after 15 seconds Not TCP- Friendly!

1128 Kbps Clip - Bottleneck Capacity 725 Kbps: 

1128 Kbps Clip - Bottleneck Capacity 725 Kbps Responsive to Capacity?

Wireless Networks: 

Wireless Networks

Wireless Issues: 

Wireless Issues Higher error rates - Bursty? Hidden terminal problem Variable bandwidth Mobile versus stationary MAC layer saturation

Hidden Terminal Problem: 

Hidden Terminal Problem 802.11 Solution to the Hidden Terminal Problem Use a four-way handshake: RTS-CTS-DATA-ACK where the RTS and CTS packets are significantly smaller than the average data packet. The maximum number of RTS retransmissions is set to 7. However, the 802.11 protocol will still have problems if the MAC layer becomes saturated!!

Rate Constrained TFRC: 

Rate Constrained TFRC A seven-hop chain network was simulated. The TFRC sending rate is manually constrained. The MAC layer saturates at 300Kbps.

Wireless Bandwidth Estimation: 

Wireless Bandwidth Estimation

Performance Definitions: 

Performance Definitions The capacity, Ci , of hop i is the maximum possible IP layer transfer at that hop. Namely, the bit rate for transferring MTU-sized IP packets. The available bandwidth, Ai , of a link relates to the unused capacity of a link during a time period. The Bulk-Transfer-Capacity (BTC) is the maximum throughput obtainable by a single TCP connection.

Bandwidth Estimation Techniques: 

Bandwidth Estimation Techniques Variable Packet Size (VPS) probing: used to measure minimum RTT’s to all hops on path. pathchar, pchar, ... Packet pair probing: each packet pair consists of two packets of the same size sent back-to-back. The goal is to measure the dispersion of a packet pair. Packet train probing: extends packet-pair probing by using multiple back-to-back packets. Self-Loading Periodic Streams (SLoPS): send a train of packets (k=100) equal-sized packets at a rate R. Sender continues to vary R to get it close to A. Trains of Packet Pairs (TOPP): send many packet pairs at gradually increasing rates from source to sink.

Packet Dispersion: 

Packet Dispersion

Bandwidth Estimation Techniques: 

Bandwidth Estimation Techniques pathchirp: uses an exponentially spaced chirp probing train and launches m packet chirps where each chirp is made up of N UDP probe packets each of size P bytes. pathchirp discards all chirps with dropped packets!

Bandwidth Estimation and Video: 

Bandwidth Estimation and Video Currently, bandwidth estimation used in Windows Media Player Capacity estimation before streaming starts Uses packet pair Mingzhe’s Research : new approach to bandwidth estimation to improve performance of video over wireless networks.

Discussion ?: 

Discussion ?