An Adaptive Multi-channel MAC protocol for Wireless Ad Hoc Networks

1. An Adaptive Multi-channel MAC protocol for Wireless Ad Hoc Networks Advisor: Wen-Tsuen Chen Student: Ting-Kai Huang

2. Outline • Introduction • Related works • Proposed method • Simulation results • Conclusion Ting-Kai Huang, MNET Lab

3. Introduction • Motivations: • the bandwidth requirement of applications nowadays is much more than before. =>trying to improve the channel utilization • The potential bandwidth of one channel in standard is limited and low • 802.11b: 1, 2, 5.5, and11(Mbit/s) • 802.11a: 6, 9, 12, 18, 24, 36, 48, and 54(Mbit/s) • 802.11g: 1, 2, 5.5, 6, 9, 11, 12, 18, 22, 24, 33, 36, 48, and54(Mbit/s) F. Cali, “Dynamic tuning of the IEEE 802.11 protocol to achieve a theoretical throughput limit,”IEEE Trans. Networking, Vol. 8, pp. 785-799, Dec. 2000. Ting-Kai Huang, MNET Lab

4. Introduction • The 802.11 standard provides multiple channels for use, but we use just only one channel at a time now. • 802.11b: 14 available channels, 3 non-overlap channels • 802.11a: 12 available channels( 8 channels for outdoor use , and 4 channel for indoor use) Channel 1 Channel 2 B A D C Ting-Kai Huang, MNET Lab

5. Introduction • Design a MAC protocol to exploit multiple channels in wireless ad hoc networks. • It is an effective way to increase the networks capacity. • Multi-channel MAC protocols can be divided into two parts: • Channel assignment • Medium access control Ting-Kai Huang, MNET Lab

6. Introduction • Channel assignment • Static • The number of channels is limited =>how to assign channel to each host with less interference between neighbors? • Mobility • Inefficient channel utilization • There are free channels but no hosts can use them. • Channel deadlock problem • dynamic Ting-Kai Huang, MNET Lab

7. Introduction Inefficient channel utilization A 1 4 E 3 2 B 1 D C Ting-Kai Huang, MNET Lab

8. Introduction Channel deadlock problem RTS2 A Ch = 1 B Ch = 2 RTS3 RTS1 C Ch = 3 D Ch = 4 RTS4 Ting-Kai Huang, MNET Lab

9. Introduction • Static • Dynamic • Hosts listen on the same channel when they don’t have packets to send. • A Host negotiates with its receiver to reserved a channel for data transmission and releases the channel when it finishes the transmission. Ting-Kai Huang, MNET Lab

10. Introduction • Medium Access Control • The Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA) is not suitable for multi-channel wireless networks. • New Multi-channel hidden terminal problem J. So “Multi-channel MAC for ad hoc networks: Handling multi-channel hidden terminal using a single transceiver,” ACM Int. Symp. Mobile Ad Hoc Networking and Computing, pp. 222-233, 2004. Ting-Kai Huang, MNET Lab

11. New multi-channel hidden terminal problem Ting-Kai Huang, MNET Lab

12. Related Works • In order to overcome the new multi-channel hidden terminal problem, =>Each host is equipped with multiple transceivers( as much as the number of channels.) Nasipuri, A.; Zhuang, and J.; Das, S.R.”A multichannel CSMA MAC protocol for multihop wireless networks,”IEEE Conf. WCNC, vol.3, pp. 1402-1406, Sept. 1999. Ting-Kai Huang, MNET Lab

13. Related Works • Take hardware costs and energy consumption into consideration => divide the channels into two classes: • Control channel • Data channels =>Each host is equipped with two transceivers, one for control channel and the other for data channels. S.-L. Wu, “A new nulti-channel MAC protocol with on-demand channel assignment for multi-hop mobile ad hoc networks,” Proc. Int. Sym. Parallel Architectures, Algorithms and Networks, pp. 232-237, Dec. 2000. Ting-Kai Huang, MNET Lab

14. Related Works • Each host is equipped with just one transceiver • not only divide the channels into two classes but also spilt the time into fixed interval • Channel Scheduling P. Bahl, R. Chandra, and J. Dunagan, "SSCH: Slotted seeded channel hopping for capacity improvement in IEEE 802.11 ad hoc wireless networks," ACM Int. Conf. Mobile Computing and Networking, pp 216- 230, 2004. Ting-Kai Huang, MNET Lab

15. Related Works • 802.11 power saving mode like • Fixed interval size limits the channel utilization J. So, “Multi-channel MAC for ad hoc networks: Handling multi-channel hidden terminal using a single transceiver,” ACM Int. Symp. Mobile Ad Hoc Networking and Computing, pp. 222-233, 2004. Ting-Kai Huang, MNET Lab

16. Proposed Method • Hosts negotiate with each other to choose the channel for data transmission. • Divide channels into the control channel and data channels • Divide each time frame into negotiation interval and data transmission interval : beacon Ting-Kai Huang, MNET Lab

17. Proposed Method • Channel Negotiation and data transmission • Channel selection • Channel status information • Channel selection rules • Dynamic Interval Adjustment • If any host needs to negotiate with someone, it sends a request to borrow some negotiation time from its neighbors. When the host finishes its work, it gives the time back to its neighbors. Ting-Kai Huang, MNET Lab

18. Channel Negotiation and Data Exchange Ting-Kai Huang, MNET Lab

19. Channel status information • This channel selection algorithm attempts to balance the channel load as much as possible, so that the bandwidth wastage caused by contention and backoff is reduced. • Each host maintains one in-use channel and two channel list , Free channel list , and Busy channel list, to keep track of necessary information for channel selection. • In-use channel: the channel that the host will use for data transmission in this time frame • Free channel list: the channels that no other neighboring hosts are using. • Busy channel list: the channels that are selected by host’s neighbors. • counter Ting-Kai Huang, MNET Lab

20. Channel selection A B MRTS MCTS RRTS Ting-Kai Huang, MNET Lab

21. Dynamic Interval Adjustment • Trying to optimize the size of negotiation interval that every host could negotiate once in a time frame. • In order to prevent extreme condition that may cause the adjustment mechanism working poorly, there are preset minimum and maximum values for the negotiation interval size. • If any host needs to negotiate with someone, it sends a request to borrow some negotiation time from its neighbors. When the host finishes its work, it gives the time back to its neighbors. Ting-Kai Huang, MNET Lab

22. Dynamic Interval Adjustment • The increment or decrement of the negotiation interval is a multiple of level of fixed size. Ting-Kai Huang, MNET Lab

23. Dynamic Interval Adjustment • Prerequisite: a host tries to negotiation for the first time. • Increase request is added in control messages. • Increase rules: • A host cannot announce a negotiation request in the last time frame • A host successfully makes the negotiation but senses that the continuous idle time of the negotiation interval in the current interval is not longer that a particular length. Ting-Kai Huang, MNET Lab

24. Dynamic Interval Adjustment • Increase rule Ting-Kai Huang, MNET Lab

25. Dynamic Interval Adjustment • Decrease rule: • A host finishes its data transmission and does not have any packet in the next time frame. • New type message, SHRINK . Ting-Kai Huang, MNET Lab

26. Dynamic Interval Adjustment • Decrease rule Ting-Kai Huang, MNET Lab

27. Dynamic Interval Adjustment • Further improvements • Making negotiation with multiple destinations in a time frame • Extending the data transmission time to next time frame • Each hosts negotiates with one destination once in a time frame. Ting-Kai Huang, MNET Lab

28. Simulations • Metric • Aggregate throughput over all flows in the network • total throughput of network • Average packets delivery delay over all flows in the networks • queuing, backoff, channel negotiation and transmission delay Ting-Kai Huang, MNET Lab

29. Simulations • Simulation model • All hosts are within each other’s transmission range. • In each case, half of the hosts are source hosts and the rest are destination, for the simulated flows • Each flow transmits Constant Bit Rate (CBR) traffic • The parameters we vary are: • number of hosts in the networks, • the networks load, and • the negotiation interval size. Ting-Kai Huang, MNET Lab

30. Simulations Ting-Kai Huang, MNET Lab

31. Simulations • Optimal negotiation interval size evaluation • Network traffic load is a fraction of aggregate bit rate of available channels • Example. 10% traffic load is 11*3*0.1=3.3 (Mbps), and the number of hosts is 8, => CBR of one sender is 3.3/4=0.825(Mbps). Ting-Kai Huang, MNET Lab

32. Simulations • The size of negotiation interval is correlated with number of hosts and network traffic load Ting-Kai Huang, MNET Lab

33. Simulations • D-MMAC • Increasing rules • Based on the number of pending packets that the host could not negotiate with their destination successfully • Overhearing the packets on the air • Receiving the negotiation packet in data transmission • Receiving the marked packets • Decreasing rule • If a host announces all the packets to the destinations, it sets it negotiation interval size to be minimum. E.-S. “An energy efficient MAC protocol for wireless LANs,”Proc. IEEE INFOCOM, Vol.3, pp. 1756-1764, June 2002. Ting-Kai Huang, MNET Lab

34. Simulations Aggregate throughput in TA-MMAC, D-MMAC, and MMAC (a)CBR is 400 Kbits/sec (b)CBR is 600 Kbits/sec Ting-Kai Huang, MNET Lab

35. Simulations Aggregate throughput in TA-MMAC, D-MMAC, and MMAC (c)CBR is 800 Kbits/sec Ting-Kai Huang, MNET Lab

36. Simulations Average latency in TA-MMAC, D-MMAC, and MMAC (b)CBR is 600 Kbits/sec (a)CBR is 400 Kbits/sec Ting-Kai Huang, MNET Lab

37. Simulations Average latency in TA-MMAC, D-MMAC, and MMAC (c)CBR is 800 Kbits/sec Ting-Kai Huang, MNET Lab

38. Conclusions • A new MAC protocol that can exploit multiple channels effectively by only using one transceiver per host. • Our protocol can adjust to different traffic load in order to maximize the channel utilization. Ting-Kai Huang, MNET Lab

39. Future works • Synchronization • Broadcast messages Ting-Kai Huang, MNET Lab

40. thank you ! Ting-Kai Huang, MNET Lab