1. Improving Routing in Sensor Networks with Heterogeneous Sensor Nodes Xiaojiang Du & Fengjing Lin Vehicular Technology Conference,2005 Spring,Volume 4

2. Outline Motivation Cluster Head Relay Routing Protocol –Cluster Formation –Intra-Cluster Routing –Inter-Cluster Routing Performance Conclusion

3. Motivation A homogeneous sensor network suffers from poor performance limit and scalability. In homogeneous sensor networks, all sensor nodes have the same capabilities in terms of communication, computation, energy supply, reliability etc.

4. Cluster Head Relay Routing Protocol Heterogeneous sensor networks with two types of nodes: a small number of powerful High-end sensors (H-sensors) and a large number of Low-end sensors (L-sensors). Cluster is formed around each H-sensor.

5. Cluster Formation All H-sensors broadcast Hello messages to nearby L-sensors with a random delay. The Hello message includes the ID and location of the H-sensor. Each L-sensor will select the closest H- sensor as the cluster head, and this leads to the formation of Voronoi diagram.

6. Cluster Formation H-sensor L-sensor sink

7. Intra-Cluster Routing When a L-sensor sends data to the cluster head for the first time, it uses a greedy geographic routing protocol (e.g., GPSR), and its location is included in the data packet. If a L-sensor does not have any data to send or forward after T seconds of deployment, it will send a specific location packet to CH, with its location information included.

8. Intra-Cluster Routing The cluster is divided into several sectors (e.g., 45 degrees for each sector as in Figure 2). For each sector, CH first broadcasts a short message indicating the receiving sector, then CH broadcasts a long message including the two routes for each sensor in this sector.

9. Intra-Cluster Routing

10. Inter-Cluster Routing When a cluster head wants to send data packets to the sink, it draws a straight line L between itself and the sink. Line L intersects with several Voronoi cells (clusters), and these cells are denoted as C 0,C 1, …,C k, which are referred to as Relay Cells.

11. Performance The default simulation testbed has 4 sinks and 300 sensor nodes randomly distributed in a 300m*300m area. For CHR, there are 25 H-sensors and 275 L- sensors. Each simulation run lasts for 600 seconds. The transmission range of a H-sensor and a L-sensor is 100m and 20m respectively.

12. Performance

13. Performance

14. Conclusion CHR has higher packet delivery ratio, lower total energy consumption, smaller end-to- end delay and better throughput than two popular sensor network routing protocols – Directed Diffusion and SWR. Why cluster divide into several sectors?