LYU9903 QoS Schemes in Wireless Networks Ho Pun Mo & Ng Maggie Supervised by Prof. Lyu R.T. Michael 21 March, 2000

Outline Introduction Review – What we have done in the last semester Preview – What we will have achieved at the end of this semester Current Status

Introduction

Our Targets Applying QoS in wireless environment Video application Integrating our QoS scheme (wireless) and LYU9802’s QoS scheme (wired)

Our Difficulties QoS in WLAN is a fresh topic Few papers/references are available Must tackle with hardware to achieve good result We have used a few weeks to ponder what we can do Need to deal with MAC layer Concern on quality control rather than producing a product/applying an algorithm! Must work on a “clean” environment

REVIEW What we have done in the last semester

Measurement Compare the bandwidth usage with and without QoS With QoS enabled Real-time audio application used more bandwidths The mp3 player could play smoothly Without QoS enabled Mp3 player and FTP competed for bandwidths The mp3 player had “click” sounds

Ported the System to Wireless Using LYU9802’s QoS scheme in the wireless environment and it works! Measurement just like the wired one, except that more time was needed to play the mp3 and FTP applications

PREVIEW What we will have achieved at the end of this semester

Overview of LYU9802’s Scheme Component of their QoS Scheme Bandwidth Reservation – RSVP Packet Scheduling – CBQ Application Mp3 player played through wired network

Bandwidth Reservation RSVP

Packet Scheduling CBQ

QoS Scheme = RSVP + CBQ       Server Client

QoS Scheme for WLAN We ain’t focusing on general methods (It is too harsh!  ) Ad-hoc method is used and therefore assumptions have been taken Many areas can be improved for the wireless environment – we will focus on a specific aspect For video/audio applications over WLAN

Schemes We Have Thought Of Decrease error rate Hardware-oriented!  Improve the hand-off mechanism Not enough reference!  Access points must be involved!  Use a workstation to simulate access point Overhead introduced!  etc.

Scheme We Are Implementing What to do? In one sentence Reserving bandwidth before sending How to do? Scenario At least two notebooks (with wireless equipment) An access point connecting to a wired network A server connecting to the wired network above

Algorithm Fact Packets are burst for real-time applications Objective Reducing collision probability when real-time packets are traveling through the air Method Broadcasting a “signal” packet between two consecutive real-time packets While receiving the “signal” packet, one would stop sending packets for a fixed time

Assumptions The environment is “clean” No node will remove from or enter into the coverage of the access point Only one real-time client is running

Implementation Frame structure

Implementation hcf_put_data() hcf_send() hcf_get_data()

Video Application Purpose Demonstration QoS is embedded! Design Client/server model Decoder is present on the client side

Video Application Implementation Detail Video Server Client MPEG file Buffer pipe mtv Wired network

Integration Integrating our QoS scheme and LYU9802’s QoS scheme LYU9802’s QoS scheme is applied within the wired network Our QoS scheme is applied in the wireless connection Of course, client is a wireless node while server is resided in the wired network

Current Status

Signal packets can be sent A client/server video application has implemented (only in wired network, and QoS is not ready!)

Q & A Thank You!