University of Rostock Applied Microelectronics and Computer Science Dept. of Electrical Engineering and Information Technology Low Energy Adaptive Clustering Hierarchy with Deterministic Cluster-Head Selection M. J. Handy, M. Haase, D. Timmermann Institute of Applied Microelectronics and Computer Science University of Rostock

University of Rostock Applied Microelectronics and Computer Science Dept. of Electrical Engineering and Information Technology Outline  Introduction / Motivation  sensor networks, lifetime, communication models  Problem Formulation  cluster-head selection, LEACH algorithm  Contribution  improved CH-selection algorithm, definition of sensor network lifetime  Simulations  simulation tool, simulation set-up, results

University of Rostock Applied Microelectronics and Computer Science Dept. of Electrical Engineering and Information Technology - Only the sandbags know -Useful application of wireless microsensor networks -Equip each sandbag with a moisture sensor -Collect and evaluate data How do sensors collaborate efficiently? Introduction Where is the spot of leakage?

University of Rostock Applied Microelectronics and Computer Science Dept. of Electrical Engineering and Information Technology Efficient collaboration of sensors means: -Ensure connectivity -Efficient role assignment -Collect only significant data -Decrease latency -Save energy Our Goal: Extend network lifetime Introduction

University of Rostock Applied Microelectronics and Computer Science Dept. of Electrical Engineering and Information Technology Introduction How to increase sensor lifetime? Reduce energy consumption -Hardware issue (e.g. circuit design) -Software issue Applications / OS Algorithms Protocols Increase energy supply -Energy density is the problem -Battery capacity increases only by % in 5 years -Compare with Moore‘s Law -Micro-sensors vs. macro- batteries?

University of Rostock Applied Microelectronics and Computer Science Dept. of Electrical Engineering and Information Technology - Direct transmission - Multihop transmission - Clustering Communication Models [1] [1] Heinzelman, Chandrakasan `01

University of Rostock Applied Microelectronics and Computer Science Dept. of Electrical Engineering and Information Technology Cluster-Based Communication A Simple Algorithm The problem: Select j cluster-heads of N nodes without communication among the nodes The simplest solution: -Each node determines a random number x between 0 and 1 -If x < j / N  node becomes cluster-head...it‘s good, but: Cluster-heads dissipate much more energy than non cluster-heads! How to distribute energy consumption?

University of Rostock Applied Microelectronics and Computer Science Dept. of Electrical Engineering and Information Technology LEACH Communication Protocol Low-Energy Adaptive Clustering Hierarchy -Cluster-based communication protocol for sensor networks, developed at MIT -Adaptive, self-configuring cluster formation - The operation of LEACH is divided into rounds - During each round a different set of nodes are cluster-heads -Each node n determines a random number x between 0 and 1 -If x < T(n)  node becomes cluster-head for current round

University of Rostock Applied Microelectronics and Computer Science Dept. of Electrical Engineering and Information Technology Cluster-Head Selection LEACH Algorithm P = cluster-head probability ( j/N ) r = number of the current round G =set of nodes not been cluster-heads in the last 1/P rounds Every node becomes cluster-head exactly once within 1/P rounds

University of Rostock Applied Microelectronics and Computer Science Dept. of Electrical Engineering and Information Technology Cluster-Head Selection LEACH Algorithm P = cluster-head probability ( j/N ) r = number of the current round G =set of nodes not been cluster-heads in the last 1/P rounds Every node becomes cluster-head exactly once within 1/P rounds Drawback: Selection of cluster-heads is completely stochastic!

University of Rostock Applied Microelectronics and Computer Science Dept. of Electrical Engineering and Information Technology Cluster-Head Selection, Our Approach I E n_current = current energy of node n E n_max = initial energy of node n Simulations showed: + longer network lifetime -After a certain number of rounds the network is stuck, although there are still nodes alive -The reason: T( n ) is too low since the remaining nodes have very low energy level Basic Idea: Include the remaining energy level

University of Rostock Applied Microelectronics and Computer Science Dept. of Electrical Engineering and Information Technology Idea: Increase T(n) when network is stuck r s = number of rounds a node has not been cluster-head (reset to 0 when a node becomes cluster-head) -T(n) is increased when the network is stuck -Possible deadlock of the network is solved Significant longer network lifetime Cluster-Head Selection, Our Approach II

University of Rostock Applied Microelectronics and Computer Science Dept. of Electrical Engineering and Information Technology Lifetime of Microsensor Networks Introducing 3 New Metrics First Node Dies (FND) -Network quality decreases considerably as soon as one node dies Half of the Nodes Alive (HNA) -The loss of a single or few nodes does not diminish the QOS of the network Last Node Dies (LND) -Estimated value for overall lifetime of the network

University of Rostock Applied Microelectronics and Computer Science Dept. of Electrical Engineering and Information Technology Simulations Simulation Tool -YANASim (Yet Another Network Analyzing and Simulation Tool) -Simulates energy consumption of microsensor networks -Uses Clustering, Multihop and Direct Transmission -Visualisation of simulation results -Platform independent (Java)

University of Rostock Applied Microelectronics and Computer Science Dept. of Electrical Engineering and Information Technology Simulations Energy Model Transmit: Receive: k = message length d = distance λ = path-loss index

University of Rostock Applied Microelectronics and Computer Science Dept. of Electrical Engineering and Information Technology Simulations Simulation Results (1) Simulation Setup: Nodes: 200 Area: 200m*200m Base Station Pos.: (100,300)m Initial Energy / Node: 1 J Message Length: 200 bit CH-Probability: 0.05 Path-Loss (intra-cluster): 2 Path-Loss (to BS): % longer lifetime for FND, 20 % for HNA

University of Rostock Applied Microelectronics and Computer Science Dept. of Electrical Engineering and Information Technology Simulations Simulation Results (2) Simulation Setup: Nodes: 200 Area: 200m*200m Base Station Pos.: (100,500)m Initial Energy / Node: 1 J Message Length: 200 bit CH-Probability: 0.05 Path-Loss (intra-cluster): 2 Path-Loss (to BS): % longer lifetime for FND, 18 % for HNA

University of Rostock Applied Microelectronics and Computer Science Dept. of Electrical Engineering and Information Technology Contribution / Conclusions -Improvement of LEACH‘s cluster-head selection algorithm -30 % increase of lifetime of sensor networks -Only local information is necessary for cluster-head selection -Communication with the base station or an arbiter node is not necessary -Three new lifetime metrics FNA, HNA, and LND -Use of metrics depends on application.