Dynamic Leadership Protocol for S-nets Gregory J. Barlow, Thomas C. Henderson, Andrew L. Nelson, and Edward Grant North Carolina State University University of Utah

Introduction Distributed sensing is an alternative to using large amounts of on-board sensors on mobile robots Smart sensor networks can be used for distributed sensing, communication, and computation This work presents a leadership protocol that forms clusters in a smart sensor network for distributed sensing

S-nets S-element: a stationary agent capable of computation, communication, and sensing. S-elements have a limited communication range. S-net: a network of spatially distributed S-elements. S-cluster: a group of S-elements with one agent as the leader.

Dynamic S-net Leadership Algorithm The DSNL algorithm is a distributed algorithm run by each S-element Each S-element must have a unique identification number Our goal is to form S-clusters with one leader for each cluster As S-elements are added to and removed from the S-net, clusters should update dynamically

S-element State id_numunique ID number leaderBoolean, whether node is a leader resolvedBoolean, whether node is resolved nodelistlist of all nodes in communication range remaininglist of unresolved nodes clusterlist of resolved nodes in the cluster lastclusterlist of nodes in the cluster during the previous generation nonclusterlist of resolved nodes not in the cluster

DSNL Algorithm Update lists of S-elements Resolve the node’s leadership status Resolve nodes in remaining Execute task code once resolved

Objectives 1. The node that has the lowest ID number of all unresolved nodes in communication range should resolve as a leader 2. Any node that is in communication range of a leader should resolve as a follower 3. Every node should be a leader or a follower 4. When a follower is removed, its leader should remove it from cluster 5. When a node’s leader is removed, that node should re-resolve

S-nets implementation in simulation

Time Node LL 4LLFF 10LL 12LLF L = leader, F = follower

S-net implementation using a robot colony

S-nets implementation using 20 S-elements

Conclusions We developed a leadership protocol for S-nets that allows dynamic updating of clusters We also developed an implementation of algorithm for embedded systems We successfully tested the leadership protocol in simulation and on a colony of mobile robots