1. Seungnam Yang, Kyungsoo Lee, Hyundoc Seo and Hyogon Kim Korea University VTC Spring 2008 SPLASH: a Simple Multi-Channel Migration Scheme for IEEE 802.11 Networks

2. Introduction SPLASH Performance evaluation Conclusion Outline

3. IEEE 802.11 MAC – High collision probability It is exacerbated in multi-hop wireless networks – Mesh networks – Overall throughput decrease Introduction

4. One attractive solution approach – Multiple channels IEEE 802.11a standard – 12 orthogonal channels Introduction

5. The authors propose a novel channel migration scheme – SPLASH No use a special signaling channel No use a special time window No use a channel switching schedule SPLASH

6. Whenever a pair of stations starts communication on a channel – All other stations jump to another channel next in priority SPLASH – Core Idea

7. One assumption of the SPLASH – The channel priority is predetermined 6  11  1(Ex: in IEE 802.11) Channel 6 serves as the default channel SPLASH

8. Another assumption – Once the communication begins The channel occupation is typically longer than a single frame exchange In order to avoid suboptimal throughput performance due to framing and channel access overhead – Frame aggregation(IEEE 802.11n) – Transmission Opportunity (TXOP)(IEEE 802.11e) SPLASH

9. WAIT-s = DATA+SIFS+ACK WAIT-c = DATA+DIFS WAIT-s = DATA+SIFS+ACK WAIT-c = DATA+DIFS

10. The time duration a station occupy the channel – TXOP – Conveyed in the Duration/ID field of the first frame SPLASH

11. Analysis – The throughput S of single channel Performance Evaluation Ptr: the probability that there is at least one transmission in a slot Ps: the probability of one success E[P]: the average frame size σ: the average free slot time Ts: transmission time Tc: the time wasted by collision Ptr: the probability that there is at least one transmission in a slot Ps: the probability of one success E[P]: the average frame size σ: the average free slot time Ts: transmission time Tc: the time wasted by collision

12. Analysis – The throughput S of single channel Performance Evaluation Ptr: the probability that there is at least one transmission in a slot Ps: the probability of success E[P]: the average frame size σ: the average free slot time Ts: transmission time Tc: the time wasted by collision Ptr: the probability that there is at least one transmission in a slot Ps: the probability of success E[P]: the average frame size σ: the average free slot time Ts: transmission time Tc: the time wasted by collision The transmission attempt probability The length of the PHY/MAC header

13. Analysis – In a single-channel scenario, the throughput formula under TXOP Performance Evaluation Ptr: the probability that there is at least one transmission in a slot Ps: the probability of one success E[P]: the average frame size σ: the average free slot time Ts: transmission time Tc: the time wasted by collision Ptr: the probability that there is at least one transmission in a slot Ps: the probability of one success E[P]: the average frame size σ: the average free slot time Ts: transmission time Tc: the time wasted by collision

14. Analysis – We extend above equation for the multi-channel operation of Splash Performance Evaluation Ptr: the probability that there is at least one transmission in a slot Ps: the probability of one success E[P]: the average frame size σ: the average free slot time Ts: transmission time Tc: the time wasted by collision Ptr: the probability that there is at least one transmission in a slot Ps: the probability of one success E[P]: the average frame size σ: the average free slot time Ts: transmission time Tc: the time wasted by collision

15. Analysis – We extend above equation for the multi-channel operation of Splash Performance Evaluation Ptr: the probability that there is at least one transmission in a slot Ps: the probability of one success E[P]: the average frame size σ: the average free slot time Ts: transmission time Tc: the time wasted by collision Ptr: the probability that there is at least one transmission in a slot Ps: the probability of one success E[P]: the average frame size σ: the average free slot time Ts: transmission time Tc: the time wasted by collision

16. Simulation – IEEE 802.11a Data rate = 54Mbps Tsw = 80μs Packet size = 1000Bytes TXOP = 3ms TR (54Mbps)= 80m Performance Evaluation

17. Aggregate throughput in 802.11a with SPLASH

18. Performance Evaluation DelayCollision

19. This paper discusses a simple channel migration scheme for multi-channel wireless networks Simulation and analysis show that this simple scheme – Boosts the throughput by 4 to 5 times – With tantamount reduction in delay Conclusion

20. Thank You for Your Attention Thank You for Your Attention