1. 1 A Topology Control Approach to Using Directional Antennas in Wireless Mesh Networks Umesh Kumar, Himanshu Gupta and Samir R. Das Department of Computer Science State University of New York at Stony Brook ICC 2006

2. 2 Outline  Introduction  Background and Problem formulation  Algorithm  Performance evaluation  Conclusion

3. 3 Introduction  Direction vs. Omni-direction Spatial reuse The transmission range of direction antennas are longer than one of omni-direction antennas Improving capacity

4. 4 Background and Problem formulation --Assumption  The transmission range of direction antenna : Rd  The transmission range of omni-direction antenna : Ro  Rd / Ro = 2/tan(θ/2)

5. 5 Interference model  The number of nodes are hear this transmission u v e A G B E C D F |Interfer(e)| =2

6. 6 Problem formulation  k -direction antennas on each node kθ < 360  max node degree is k  Maximizing throughput Minimizing interference  Smaller interference caused path lengths increasing

7. 7 Spanning Tree Algorithm  Furer and Raghavachari ’ s algorithm G=(V,E) Input : random spanning tree T=(V,E) Let S be the set of vertices having degree d or d- 1 (d is the degree of T) Let T1, …,Tr be the subtrees comprising T-S If there is an edge between Ti and Tj, the edge is inserted in T Output: minimum degree spanning tree T=(V,E)

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11. 11 Using direction antenna  A centralized algorithm  Using k arcs of angle θ and radius Rd on each node to cover all edges in E ’

12. 12 Performance evaluation : Simulation environment SimulatorQualnet The number of node100 Transmission range70m Network size300 m 2 or 500 m 2 Average node degrees5 or 13 Antenna beamwidth30,45 and 60 The number of antennas3 or 4

13. 13 Performance evaluation: Topological properties  Average interference per network link  Average stretch factor The ratio of the shortest path lengths with directional antennas and omni-directional antennas in the mesh network

14. 14 Average interference per link with different beamwidths 3 antennas per node 4 antennas per node

15. 15 Average Stretch factors with different beamwidths 3 antennas per node 4 antennas per node

16. 16 Packet delivery fraction for qualnet simulations (4 antennas per node) Dense network Sparse network 100 nodes and50 flows

17. 17 Packet delivery fraction for qualnet simulations (3 antennas per node) Dense network Sparse network 100 nodes and50 flows

18. 18 Conclusion  This paper presented a topology control approach to using directional antennas in wireless multihop networks. Low interference Reasonable stretch factor Increasing the end to end throughput

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