1. Link Layer Multicasting with Smart Antennas: No Client Left Behind Souvik Sen, Jie Xiong, Rahul Ghosh, and Romit Roy Choudhury Dept. of Electrical and Computer Engineering, Duke University, USA IEEE ICNP 2008 YearAccept rate 200614.2% 200714.5% 200816.3%

2. Outline Introduction Proposed Mechanism – Beamcast Evaluation Conclusion

3. Introduction Wireless link layer multicast is an important service for emerging applications. However, multicast throughput degrades severely. Diverse channel conditions The transmission rate is bottlenecked by the weakest client Smart antennas are allowing a single transmission to only serve a subset of the multicast group.

4. An access point (AP) is equipped with a smart beamforming antenna. All the clients have simple, omnidirectional antennas. The clients are scattered around the AP. Introduction – System model 11Mbps directional beam time 11Mbps Omni 1 2 Header 3 AP:

5. To serve the weaker ones with high data-rate beamformed transmissions. Introduction – Motivation 11Mbps directional beam Header time 11Mbps Omni 1 2 1Mbps Omni 1 2

6. Introduction – Problem Formulation 1 2 3 4 5 9 Mbps 7 Mbps 3 Mbps 6 Mbps 11 Mbps Beam 1 Beam 2 Beam 3 Beam 4 The optimal choice of beam-sets and corresponding data rates will maximize multicast throughput.

7. Proposed Mechanism – Overview Beamcast Link Quality Estimator Multicast Scheduler Retransmission Manager

8. Beamcast Link Quality Estimator Multicast Scheduler Retransmission Manager 11Mbps 1 2 8 6 7 5 3 4 2Mbps 5.5Mbps2Mbps 1Mbps 5.5Mbps 11Mbps5.5Mbps

9. Beamcast Link Quality Estimator Multicast Scheduler Retransmission Manager 1 2 8 6 7 5 3 4 11Mbps 2Mbps 5.5Mbps2Mbps 1Mbps 5.5Mbps 11Mbps5.5Mbps Beam 1 (B 1 ) Beam 2 (B 2 ) Beam 3 (B 3 ) Beam 4 (B 4 ) Beam 5 (B 5 ) Beam Grouping 827451 B5B5 B1B1 B2B2 B4B4 B3B3 θ0θ0 θ1θ1 θ2θ2 θ3θ3 θ4θ4 θ5θ5

10. Beamcast Link Quality Estimator Multicast Scheduler Retransmission Manager 8  11Mbps 7  2Mbps 7  5.5Mbps 4  2Mbps 5  1Mbps Beam Grouping 827451 B5B5 B1B1 B2B2 B4B4 B3B3 1  5.5Mbps Beam set rate Remaining clients when beam B k covered a client at θ i using a rate r.

11. Beamcast Link Quality Estimator Multicast Scheduler Retransmission Manager 8  11Mbps 2  2Mbps 7  5.5Mbps 4  2Mbps 5  1Mbps Beam Grouping 827451 B5B5 B1B1 B2B2 B4B4 1  5.5Mbps 827451 B5B5 B1B1 B2B2 B4B4 827451 B5B5 B1B1 B2B2 B4B4 B3B3 B3B3 < Set I Set II

12. Beamcast The AP receives feedback from clients at the end of every batch transmission. Link Quality Estimator Multicast Scheduler Retransmission Manager

13. Evaluation SimulatorQualnet 4.0 Parameters Nodes10~100 (randomly deployed) TX range of AP250 m Path Loss ModelTwo-ray Antenna Beamwidth45 o, 60 o, 90 o

14. Throughput decreases with increase in client density Multicast Throughput

15. Increased delivery ratio for all clients, hence, No Client Left Behind Delivery Ratio

16. Conclusion To execute multiple high data rate transmissions using a combination of omnidirectional and beamformed antenna modes.

17. Thank you~