LYU9903 QoS Schemes in Wireless Networks

1. LYU9903QoS Schemes in Wireless Networks Ho Pun Mo & Ng Maggie Supervised by Prof. Lyu R.T. Michael 21 March, 2000

2. 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

3. Introduction

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

5. 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

6. REVIEWWhat we have done in the last semester

7. 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

8. 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

9. PREVIEWWhat we will have achieved at the end of this semester

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

11. Bandwidth Reservation • RSVP

12. Packet Scheduling • CBQ

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

14. 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

15. 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.

16. Scheme We Are Implementing • What to do? • In one sentenceReserving 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

17. 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

18. 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

19. Implementation • Frame structure

21. Implementation • hcf_put_data() • hcf_send() • hcf_get_data()

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

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

24. 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

25. Current Status

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

27. Q & A Thank You!