Sensor network routing protocol for underground robot remote control Demonstration picture (IDF)

The scenario An underground, remote controlled robot is travelling under the ground. Remote controlling the robot is done wirelessly. PROBLEM- direct, one- hop receive/ transmit is impossible due to tunnels hiding and blocking radio waves.

Solution- Multi hop routing Robot is dropping motes behind, leaving a trail of motes capable of routing a multi hop communication between user in the tunnel entrance and robot.

Routing topology One hop communication path Low SNR/ Link quality Tunnel Getting new ID from robot Two hop communication path

Multi hope routing in sensor Networks Wireless Sensor Networks (WSN) Characteristics: – Energy constrains – Wireless medium – Unknown Topology – Routing capability Examples of known algorithms Source Routing Geographical Routing

Our challenge Design and implement specific routing algorithm. Routing and forwarding should be: – Simple – Fast – Considering the specific spatial case topology. Network should be robust.

Our challenge (cont.) Equipment : – Low power wireless sensor: Tmote Sky – Implementing IEEE – 2 KB RAM – Not supporting debug Software platphorm : – Sentilla mote software architecture includes JVM – Sentilla programming model – special API – Multi Threaded Programming (less then 4 at a time). – Poor support

Basic components (basic mote) Router Neighbors lookup thread Forwarding thread Routing algorithm thread Neighbors table (ID,isAlive) Look and update Sending beacons periodically Receiving and forwarding Simple greedy logic Simple hash function Choose candidates

Basic components Example 3 way hand check ID = X,Y Sending beacon ID = X+1,Z Beacon reply Routing table ID = X+1,Z Time = … isAlive = true … Hash function

Router class diagram

Characters of our solution Multi threaded prioritized implementation. Memory and runtime complexity efficient. Five different kinds of hierarchical messages. Simple handling of multiple access to the medium. Three way hand shake to join the network.

Conclusions 1.Implementing a reliable routing application over a limited resources' system (i.e. memory, CPU, energy etc.) can be very challenging in a sensor network, even with a simple topology. 2.Sentilla JAVA platform allows rapid development though the lack of a hardware debugging equipment slows it significantly. 3.JVM overhead hurts performance badly. This platform can serve as a POC utility but not for high throughput communication.

Future Work 1.Use another OS (tiny OS) to improve performance. 2.Implement a reliable application in the protocol sub layer or MAC layer, suitable for wireless medium. 3.Use this application to explore a chain topology throughput (e.g. signaling tradeoff, collision probability etc.). 4.Enhance routing algorithm to support smarter neighbor selection (energy, RSSI awareness). 5.Caching neighbors messages to improve robustness (AODV style).

Questions??.