1. Shou-Chih Lo and Chia-Wei Tseng National Dong Hwa University A Novel Multi-channel MAC Protocol for Wireless Ad Hoc Networks VTC 2007-spring

2. Outline Introduction Proposed Protocol Performance Evaluation Conclusions

3. Introduction IEEE 802.11 is designed for single channel access However, multiple channels can be used – Enhance network throughput IEEE 802.11a  12 channels IEEE 802.11b  3 channels 3

4. Introduction In a multi-channel MAC protocol, the most important work is to decide an appropriate channel for data exchanges between the transmission pairs – When? – Where?

5. Introduction The authors classify various multi-channel MAC protocols into two categories – Dedicated control channel – Common control period

6. Introduction – Dedicated control channel Advantages – Control channel can serve as a broadcast channel – Channel negotiations can be done anytime Disadvantages – The control channel can not be used for data packet It may cause lower channel utilization – The data capacity is dependent on the bandwidth of the control channel Can’t be dynamically adjusted

7. Introduction – Common control period Advantages – All channels can be used Increases channel utilization – The data capacity is dependent on the length of a control period Can be dynamically adjusted Disadvantages – Channel negotiations can not be done anytime – It may cause a longer delay

8. Proposed Protocol Combines the advantages of using the dedicated control channel and the common control period Uses two transceivers at each STA – Control transceiver – Data transceiver

9. Data cha 2 Data channel 1 Control channel Data cha 2 Data channel 1 Control channel Data cha 2 Data channel 1 Control channel Data cha 2 Data channel 1 Proposed Protocol Control channel A B C D ATIM(1) ATIM-ACK(1) ATIM(2) ATIM-ACK(2) ATIM Window RTS CTS DATA ACK RTS CTS DATA ACK

10. Proposed Protocol – feature 1. The authors enable the control channel to be a data channel 2. The authors propose to perform data retransmissions on the same selected channel without extra negotiations

11. Proposed Protocol – feature 1. The authors enable the control channel to be a data channel 2. The authors propose to perform data retransmissions on the same selected channel without extra negotiations

12. Data cha 2 Data channel 1 Control channel Data cha 2 Data channel 1 Control channel Data cha 2 Data channel 1 Control channel Data cha 2 Data channel 1 Proposed Protocol Control channel A B C D ATIM(1) ATIM-ACK(1) ATIM(2) ATIM-ACK(2) ATIM Window RTS CTS DATA ACK RTS CTS DATA ACK RTS CTS DATA ACK RTS(C) CTS(C)

13. Proposed Protocol – feature 1. The authors enable the control channel to be a data channel 2. The authors propose to perform data retransmissions on the same selected channel without extra negotiations

14. Data cha 2 Data channel 1 Control channel Data cha 2 Data channel 1 Control channel Data cha 2 Data channel 1 Control channel Data cha 2 Data channel 1 Proposed Protocol Control channel A B C D ATIM(1) ATIM-ACK(1) ATIM(2) ATIM-ACK(2) ATIM Window RTS CTS DATA ACK RTS CTS DATA ACK RTS CTS DATA ACK RTS(1) CTS(1) RTS CTS DATA ACK

15. Performance Evaluation Simulator – CSIM Topology – Fully connected Arrival rate – Poisson distribution Packet size – 1024 Bytes Others – Follow IEEE 802.11

16. Performance Evaluation – channels = 2

19. Performance Evaluation – STAs = 80

21. Conclusions The authors proposed a multi-channel MAC protocol in ad hoc networks. – Simple and efficient – Combines the advantages of control channel and control period The performance evaluation show the protocol can achieve – Higher throughput – Higher channel utilization – Lower average delay

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