Single-Hop vs Multi-Hop Star topology Every sensor communicates directly(single-hop with the base station May require large transmit powers and may be infeasible in large geographic areas ° Mesh topology Sensors serve as relays forwarders) for other sensor nodes(multi hop May reduce power consumption and allows for larger coverage Introduces the problem of routing Sensor Single-Hop Multi-Hop Aggregation Node Base station
Single-Hop vs. Multi-Hop • Star topology • Every sensor communicates directly (single-hop) with the base station • May require large transmit powers and may be infeasible in large geographic areas • Mesh topology • Sensors serve as relays (forwarders) for other sensor nodes (multihop) • May reduce power consumption and allows for larger coverage • Introduces the problem of routing
Challenges in WSNs: Energy Sensors typically powered through batteries replace battery when depleted recharge battery, e. g. using solar power discard sensor node when battery depleted For batteries that cannot be recharged sensor node should be able to operate during its entire mission time or until battery can be replaced Energy efficiency is affected by various aspects of sensor node/network design Physical layer switching and leakage energy of CMoS-based processors CPU E switch +e leakage C*V2+V米 leak 菜△
Challenges in WSNs: Energy • Sensors typically powered through batteries • replace battery when depleted • recharge battery, e.g., using solar power • discard sensor node when battery depleted • For batteries that cannot be recharged, sensor node should be able to operate during its entire mission time or until battery can be replaced • Energy efficiency is affected by various aspects of sensor node/network design • Physical layer: • switching and leakage energy of CMOS-based processors
Challenges in WSNs: Energy Medium access control layer: contention-based strategies lead to energy-costly collisions problem of idle listening Network layer responsible for finding energy-efticient routes ° Operating system: small memory footprint and efficient task switching ecurity fast and simple agorithms for encryption authentication etc Middleware. in-network processing of sensor data can eliminate redundant data or aggregate sensor readings
Challenges in WSNs: Energy • Medium access control layer: • contention-based strategies lead to energy-costly collisions • problem of idle listening • Network layer: • responsible for finding energy-efficient routes • Operating system: • small memory footprint and efficient task switching • Security: • fast and simple algorithms for encryption, authentication, etc. • Middleware: • in-network processing of sensor data can eliminate redundant data or aggregate sensor readings
Challenges in WSNs: Self-Management Ad-hoc deployment many sensor networks are deployed without design sensors dropped from airplanes(battlefield assessment sensors placed wherever currently needed (tracking patientsin disaster zone moving sensors( robot teams exploring unknown terrain sensor node must have some or all of the following abilities determine its location determine identity of neighboring nodes configure node parameters discover route(s) to base station initiate sensing responsibility
Challenges in WSNs: Self-Management • Ad-hoc deployment • many sensor networks are deployed “without design” • sensors dropped from airplanes (battlefield assessment) • sensors placed wherever currently needed (tracking patients in disaster zone) • moving sensors (robot teams exploring unknown terrain) • sensor node must have some or all of the following abilities • determine its location • determine identity of neighboring nodes • configure node parameters • discover route(s) to base station • initiate sensing responsibility
Challenges in WSNs: Self-Management Unattended operation Once deployed, WSN must operate without human intervention Device adapts to changes in topology density, and traffic load Device adapts in response to failures Other terminology Self-organization is the ability to adapt configuration parameters based on system and environmental state Self-optimization is the ability to monitor and optimize the use of the limited system resources Self-protection is the ability recognize and protect from intrusions and attacks Self-healing is the ability to discover, identify and react to network disruptions
Challenges in WSNs: Self-Management • Unattended operation • Once deployed, WSN must operate without human intervention • Device adapts to changes in topology, density, and traffic load • Device adapts in response to failures • Other terminology • Self-organization is the ability to adapt configuration parameters based on system and environmental state • Self-optimization is the ability to monitor and optimize the use of the limited system resources • Self-protection is the ability recognize and protect from intrusions and attacks • Self-healing is the ability to discover, identify, and react to network disruptions