Wireless Sensor Wireless Sensor Networks (WSNs) Networks (WSNs) - PowerPoint PPT Presentation

Wireless Sensor Wireless Sensor Networks (WSNs) Networks (WSNs)

Technological Revolution Computer Networking 1. 1990 LAN � Internet � Wireless Communications 2. 2000 GSM/UMTS � WLAN � Wireless Sensing Technologies 2010 3. MEMS Technology � WSNs � 2005 Prof. I Stavrakakis 2

Applications for Wireless Sensor Networks Military Applications Military Applications o o (monitoring friendly forces, monitoring equipment, battlefield surveillance, reconnaissance of opposing forces and terrain) Environmental Monitoring Environmental Monitoring o o (flood/forest fire detection, space exploration, biological attack detection) ) Commercial Applications Commercial Applications o o (home/office smart environments, health applications. ( environmental control in buildings) Tracking Tracking o o (targeting in intelligent ammunition, tracking of doctors and patients inside a hospital) 2005 Prof. I Stavrakakis 3

Application Examples 2005 Prof. I Stavrakakis 4

WSN Model Terminology Sensors Sensors 1. 1. Make discrete, local samples ( measurements ) of the � phenomenon Communicate over wireless medium, forming a � wireless sensor network Disseminate information about the phenomenon to � the observer Observer Observer 2. 2. Is interested in measuring/ monitoring the � behaviour of a phenomenon Accepts measurements under specific performance � requirements (accuracy or delay ) Phenomenon Phenomenon 3. 3. Entity of interest to the observer � 2005 Prof. I Stavrakakis 5

System Architecture � Cheap, low Cheap, low- -power, tiny power, tiny � sensors used in sensors used in thousands thousands � Communication with Communication with � WSN the use of miniaturized the use of miniaturized wireless transceivers wireless transceivers S I N K Internet, � Data aggregation Data aggregation � Satellite, during data during data etc. propagation or at the propagation or at the sink sink � Unattended Unattended operation operation � WSN SINK of the sensor network of the sensor network � Sink transmits data to Sink transmits data to � the end- the end -user at the user at the USER other end of the world of the world other end 2005 Prof. I Stavrakakis 6

Sensors Hardware Platform Node Node Location Finding System Mobilizer characteristics characteristics Tiny size Tiny size • • Low power Low power • • Sensor, Low bit rate Low bit rate CPU, Digital • • A/D Real world data To user Memory Transceiver High densities Converter High densities • • Low cost Low cost • • (dispensable) (dispensable) Autonomous Autonomous • • Power Power Unit Generator Adaptive Adaptive • • 2005 Prof. I Stavrakakis 7

Communication Architecture Cross- -layer design layer design of of Cross • • protocol stack protocol stack Integration of routing Integration of routing • • Task Management Plane Task Management Plane functionality and power Mobility Management Plane Mobility Management Plane functionality and power Power Management Plane Power Management Plane awareness (energy- -aware aware awareness (energy Application Layer Application Layer routing) routing) Transport Layer Transport Layer Integration of routing of routing Integration • • functionality and data functionality and data Network Layer Network Layer transport (aggregation) transport (aggregation) Inclusion of mobility as a of mobility as a Inclusion • • Data Link Layer Data Link Layer network control primitive network control primitive Physical Layer Physical Layer Promotes cooperative Promotes cooperative • • efforts (task management efforts (task management plane) plane) 2005 Prof. I Stavrakakis 8

WSNs vs. MANETs WSNs and MANETs are equivalent networks build for different purposes! Similarities Similarities Data communication over wireless � medium Ad-hoc network topology � Power and bandwidth are scarce � resources 2005 Prof. I Stavrakakis 9

WSNs vs. MANETs Differences Differences WSNs are deployed and owned by a single user � Sensor nodes are extremely cheap, tiny � devices, not like ad-hoc network nodes (PDAs, laptops, etc.) No general purpose communication network, � but a data-gathering, surveillance network Number of nodes several orders of magnitude � higher than MANETs Energy and bandwidth conservation is a � primary concern in WSN protocol design 2005 Prof. I Stavrakakis 10

WSNs vs. MANETs Comparison Summary Features MANET WSN Features MANET WSN Multi- -hop routing protocols hop routing protocols Yes Yes Multi Yes Yes applicable applicable Ad- Ad -hoc deployment hoc deployment Yes Yes Yes Yes (unattended operation) (unattended operation) Extreme power constraints Extreme power constraints No No Yes Yes for nodes operation for nodes operation Low- Low -cost nodes of tiny size cost nodes of tiny size No No Yes Yes Robust to node failures Robust to node failures Yes Yes Yes Yes (self- -healing) healing) (self 2005 Prof. I Stavrakakis 11

WSNs vs. MANETs Comparison Summary Features MANET WSN Features MANET WSN General purpose Yes No General purpose Yes No communication network communication network Node density Node density <100 <100 <1000 <1000 Mobility of nodes Yes Yes Mobility of nodes Yes Yes In- In -network data network data No No Yes Yes processing processing Unique global IP addresses Yes No Unique global IP addresses Yes No 2005 Prof. I Stavrakakis 12

Sensor Network Protocols Design Challenges Energy depletion is the is the main resource main resource Energy depletion � � bottleneck bottleneck Reduce each sensor’s active duty cycle active duty cycle Reduce each sensor’s � � Minimize data communication over over Minimize data communication � � wireless channel wireless channel Use computation to reduce data size (data � aggregation) Communicate only network state summaries � instead of actual data Maximize total network lifetime Maximize total network lifetime � � Minimum energy routing � 2005 Prof. I Stavrakakis 13

Sensor Network Protocols Design Challenges � Robustness Robustness to dynamic environment to dynamic environment � � Network should be self-configuring � Network should be self-healing � Network should be adaptive (measure and act) � Scalable to thousands Scalable to thousands of nodes of nodes � � Organize network in a Organize network in a hierarchical hierarchical manner manner � (possibly with the use of clustering) (possibly with the use of clustering) � Use only Use only localized localized algorithms algorithms ; with localized ; with localized � interactions between nodes interactions between nodes 2005 Prof. I Stavrakakis 14

Sensor Network Protocols Design Characteristics � Data-centric operation • Focus on application data , not individual nodes: information gathering is the purpose of sensor networks Traditional networks: : “What is the temperature at sensor #27 at sensor #27 ? ? ” ” “What is the temperature Sensor Networks: : “ Where are Where are the the nodes nodes whose temperatures whose temperatures “ recently exceeded 30 degrees? ” ” recently exceeded 30 degrees? 2005 Prof. I Stavrakakis 15

Sensor Network Protocols Design Characteristics � Application Application- -specific design specific design � • WSN networks can be tailored to the sensing task at hand • Intermediate nodes can perform application-specific data aggregation and caching � Low energy expenditure at nodes Low energy expenditure at nodes � • Use of low duty-cycled sensors • Coordinate groups of sensors to fall to the sleep stated 2005 Prof. I Stavrakakis 16

Classification of Routing Protocols According to route discovery According to route discovery � � Proactive Proactive 1. 1. Reactive Reactive 2. 2. Hybrid Hybrid 3. 3. According to location awareness According to location awareness � � Location aware routing Location aware routing 1. 1. Location- -less routing less routing Location 2. 2. 2005 Prof. I Stavrakakis 17

Classification of Routing Protocols (cont’d) According to nodes’ participating style According to nodes’ participating style � � Direct communication Direct communication 1. 1. Flat routing Flat routing 2. 2. Clustering routing protocols Clustering routing protocols 3. 3. SINK SINK SINK 2005 Prof. I Stavrakakis 18

Sensor Network Communication Protocols Proposed Sensor Network Performance Performance Proposed Sensor Network � � Metrics Metrics Energy efficiency/system lifetime � Latency � Accuracy � Fault-tolerance � Scalability � 2005 Prof. I Stavrakakis 19

SPAN Problem: Need to : Need to minimize the minimize the Problem energy consumption of wireless of wireless energy consumption nodes in a wireless ad hoc nodes in a wireless ad hoc network! network! IDEA: IDEA: Leverage the time the network Leverage the time the network interface of a node remains idle idle interface of a node remains to power power- -down down the radio of the the radio of the to node. node. 2005 Prof. I Stavrakakis 20