1. Angular MAC: a framework for directional antennas in wireless mesh networks Erdem Ulukan and Özgür Gürbüz Faculty of Engineering and Natural Sciences, Sabanci University, Turkey ACM Journal of Wireless Networks vol. 14 no.2 (April 2008) (SCI 2008=0.741)

2. Outline Introduction Proposed Mechanism – Angular MAC Evaluation Analysis – Throughput Enhancement Conclusion

3. Introduction Capacity of wireless mesh networks can be enhanced through the use of smart directional antennas. High quality links Throughput enhancement by spatial reuse Lots of previous works suffer from Hidden terminal problem Deafness problem Head-of-line blocking problem

4. Each node is equipped with a multi-beam antenna. The multi-beam antenna either transmit or receive data packets at a time, but not both. Introduction – Antenna Model a a 01 23

5. Introduction – Related Work D-CSMA All nodes are 1-hop neighbor. Nasipuri, A., Ye, S., You, J., & Hiromoto, R. E. A MAC protocol for mobile ad hoc networks using directional antennas. IEEE WCNC, 2000. a 01 23 c 01 23 b 01 23 d 01 23 Directional RTS Directional CTS Data (a  b) Directional RTS Directional CTS Data (c  d)

6. Introduction – Related Work D-CSMA Deafness problem Nasipuri, A., Ye, S., You, J., & Hiromoto, R. E. “A MAC protocol for mobile ad hoc networks using directional antennas.” IEEE WCNC, 2000. a 01 23 c 01 23 b 01 23 d 01 23 Directional RTS Data (c  d) Deafness in node c

7. Introduction – Related Work Head-of-line blocking problem Result from transmission queue (FIFO) Optimal scheduling is a  b, a  c Kolar, V., Tilak, S., & Abu-Ghazaleh, N. B. “Avoiding head of line blocking in directional antenna.” IEEE LCN, 2004. a 01 23 c 01 23 b 01 23 d 01 23 Data (c  d) Queue(1) Queue(2)

8. Goal Proposed Angular MAC (ANMAC) Hidden terminal problem is alleviated Deafness problem is prevented Head-of-line blocking problem is alleviated

9. Proposed Mechanism Angular MAC (ANMAC) All nodes are single hop. a 01 23 c 01 23 b 01 23 d 01 23 AN-RTS [1,a,b] [2,a,b] [3,a,b] [0,a,b] Data (a  b) [b,a,2,1,3] AN-CTS [b,a,3,1,3] [b,a,0,1,3] [b,a,1,1,3]

10. Proposed Mechanism Angular MAC (ANMAC) T defer =SIFS+T ACK a 01 23 c 01 23 b 01 23 d 01 23 Data (d  c) ANRTS time d to c a to b ANRTS SIFS ANCTS SIFS DATA SIFS ACK DIFS CW SIFS ANCTS SIFS DATA SIFS ACK DIFS CW T defer

11. Proposed Mechanism Angular MAC (ANMAC) Network Allocation Notification (NAN) a 01 23 c 01 23 b 01 23 d 01 23 Data (c  d) NAN ANRTS time c to d a to b ANRTS SIFS ANCTS SIFS DATA SIFS ACK SIFS DIFS CW SIFS ANCTS SIFS DATA SIFS ACK DIFS CW NAN T defer

12. Evaluation SimulatorOPNET Competitions 802.11b D-CSMA Parameters Physical layer data rate11 Mbps Packet generate rate1450 bytes at a Poisson distribution All transmissions are single hop.

13. Cross-like Topology

15. Random Topology

16. Analysis – Throughput Enhancement (Contention Window) According to success ratio (N c /N s ) for tuning optimal contention window to maximize the throughput. N c – the number of collided packets N s – the number of successful packets Define τ– the probability that a node transmits in a randomly chosen slot p – the probability that a transmitted packet encounters a collision P s – the probability of successful transmission From: IEEE Std 802.11 Figure. 51

17. Analysis Figrue. Markov Chain model for the backoff window size i,w i -2 i,w i -1 i as backoff stage k as backoff time counter W as CW min W i as 2 i W, i ∈ (0,m), so CW max =2 m W

19. Analysis

20. Evaluation for Contention channel enhancements Omni 802.11b Directional ANMAC-LS Optimal CW min is for 802.11b.

21. Conclusion ANMAC’s contributions are self configuring nature with neighbor discovery immunity to deafness optimal selection and dynamic adaptation of contention window to maximize the network throughput

22. Thank you~