1. Using Directional Antennas for Medium Access Control in Ad Hoc Networks Romit Roy Choudhury, Xue Yang, Ram Ramanathan. and Nitin H. Vaidya University of lllinois at Urbana-Champaign MOBICOM 2002

2. Outline  Introduction  Problems with Basic DMAC  Multi-Hop RTS MAC Protocol  Simulation  Future work & Conclusion

3. Introduction Antenna Model  Assumed antenna system  Omni antenna  Tx/Rx from all directions (360 degrees)  Directional antenna  Can point its main lobe towards any specified direction  Do not consider power control  Fixed beamwidth

4. Introduction Antenna Model A Directional modeOmni mode B  Benefits of directionality  Spatial reuse  Higher transmission range

5. Problems with Basic DMAC  Hidden terminal problems  Hidden terminal due to asymmetry in gain BE FA RTSCTSDATARx RTS

6. Problems with Basic DMAC  Deafness A B DC DATA

7. Multi-Hop RTS MAC Protocol  Protocol Description : Multi-Hop RTS  Direction-Omni (DO) Neighbor  Direction-Direction (DD) Neighbor CD TXRX DD Neighbor C D TX RX DO Neighbor

8. CTS RTS Multi-Hop RTS MAC Protocol D G B RTS F C RxDATA RX A

9. Simulation Results

10. Simulation

11. Future Work & Conclusion  Rely less on the upper layers for beamforming information  Replace the omni mode operation (tone)  Performance of the system improve in terms of aggregate throughput and end- to-end delay

12. Thank You !!

13. Problems with Basic DMAC  Hidden terminal problems  Hidden terminal due to unheard RTS/CTS D BF E DATA RTS CTS DATA