1. Cooperation and Directionality: Friends or Foes? Zhifeng Tao, Thanasis Korakis, Feilu Liu, Shivendra Panwar, Jinyun Zhang, Leandros Tassiulas IEEE ICC 2008

2. Outline Introduction Proposed Method Performance Evaluation and Comparison Conclusions

3. Introduction Benefits of Directional Antennas Spatial reuse Longer transmission and reception range Higher network capacity Less interference Fewer transmission hops

4. Introduction Benefits of Cooperative Communication Spatial diversity Higher capacity Reliability Extended coverage

5. Introduction Distinction Directional antenna relies on directional transmission of wireless signal Cooperative communications depend on the broadcast nature of wireless channel

6. Motivation and Goal Motivation Although a handful of MAC protocols have already been proposed to support either directional antenna or cooperative communications, nothing exist that can exploit both simultaneously Goal Proposed a MAC that taps into the combined potential of both transmission directionality and cooperation diversity

7. Network Model Two hosts are said to be neighbors if they can communicate with each other over a wireless link. We assume that each node knows its neighbors‘ location as well as its own location. AB AB phy layer MAC layer Data Flow

8. Antenna Model

9. Proposed Methods O-CoopMAC Cooperative MAC with Omni-directional antenna D-NoopMAC Non-Cooperative MAC with Directional antenna D-CoopMAC Cooperative MAC with Directional antenna

10. O-CoopMAC (Cooperative MAC with Omni-directional antenna) SsSs SrSr SdSd Cooperation Table of Ss Index (MAC address)LinkRate SsSs L sr R sr SsSs L sd R sd SrSr L rd R rd … … … SdSd L dr … … … RTS HTS CTS 1 st hop data@R sr 2 nd hop data@R rd ACK

11. D-NoopMAC (Non-Cooperative MAC with Directional antenna) RTSCTSACK A B Data

12. D-CoopMAC (Cooperative MAC with Directional antenna) SsSs SrSr SdSd Cooperation Table of Ss Index (MAC address)LinkRate SsSs L sr R sr SsSs L sd R sd SrSr L rd R rd … … … SdSd L dr … … … RTSHTS CTS 1 st hop data@R sr 2 nd hop data@R rd ACK

13. Performance Simulation and Comparison Simulation Settings BaselineIEEE 802.11g DeploymentRandom Network size (in radius)350m Radius of omnidirectional antenna100m Directional antenna's lobe of radius119m and 141m beams number of directional antenna2 and 4

14. Throughput versus Number of Stations

15. Channel access delay

16. Throughput versus Traffic Load (100 stations)

17. Throughput versus Traffic Load (300 stations)

18. Conclusions This paper has presented three new MAC protocol for ad-hoc networks To establish a deeper understanding of the relative performance of cooperative communications and directional transmission Cooperation and directionality can be rather foes than friends

19. Thank you