1. A New Link Scheduling Algorithm for Concurrent Tx/Rx Wireless Mesh Networks Author: Kwan-Wu Chin University of Wollongong, Australia From: ICC 2008 Speaker: Chen-Yan Wu

2. Outline Introduction Related Work Motivation Antenna Model － Smart Antenna Assumptions and Problem statement Proposed Mechanism Simulation Conclusions

3. Introduction Wireless mesh networks offer significant benefits in environments that lack communication infrastructures. For example, the applications include ad-hoc video surveillance systems. To increase the capacity of mesh networks is to equip routers with smart antennas.

4. Related Work B. Raman and K. Chebrolu, “Design and Evaluation of a New MAC Protocol for Long- Distance 802.11 Mesh Networks”, MobiCom 2005 2P, two-phase: Tx/Rx Each node equipped with smart antenna (k-beam) for concurrent transmission. The network environment requires bipartite topology. s1s1 s4s4 s3s3 s2s2 s1s1 s4s4 s3s3 s2s2 Odd slotEven slot

5. Motivation The protocol, 2P, is the shortest schedule under bipartite network topology. and by graph coloring theory, the bipartite is 2-colorable. But the full connected graph, K 5, is not 2-colorable. The author removes cliques in topology to reduces the chromatic number of a graph for minimizing transmission slots. K5K5

6. Goal Proposed a schedule to maximize the number of scheduled links within a time slot. s1s1 s4s4 s3s3 s2s2 Bipartite Remove cliques Tx Rx Tx Rx Tx Rx

7. Antenna Model － Smart Antenna The antenna system can either transmit or receive data at a time in multiple directions (include all directions), but cannot do both simultaneously. There will be a collision, when different data from two senders at the same beam. s1s1 s2s2 s3s3 s4s4 data 1 data 2 data 3

8. Assumptions and Problem statement Assumptions There are n stationary nodes. Each node has less than k neighbors and equips k-element in its smart antenna. There is just a neighbor in each beam of every node. Problem statement Give a wireless mesh network running spatial TDMA, determine a maximal concurrent transmit and receive schedule that satisfies constraints: Each link must receive two time slots: transmit and receive. Either transmit or receive Maximum of k concurrent links at every node.

9. Proposed Mechanism A connected graph G=(V,E), where V and E denote the set of vertices and edges respectively. Proposed algorithm: MAX_DEG returns the vertex with the highest degree. CHILDREN returns the set of vertices adjacent to V h. COLOR returns the chromatic number of graph G.

10. Example s4s4 s5s5 s2s2 s1s1 s6s6 s3s3 c=2 c=1c=3 c=1 c=2c=4 Before (4 color) s4s4 s5s5 s2s2 s1s1 s6s6 s3s3 c=2 c=1c=2 Before (2 color)

11. Simulation Simulator: MatGraph (a Matlab tookit) Compare to five graph coloring algorithms

15. Conclusions Proposed a algorithm to reduce the frame size of a spatial TDMA based concurrent transmit/receive wireless mesh network, and the network capacity increased. The future works is to consider traffic demands.

16. Thank you~