Wireless Embedded Systems ( x) Ad hoc and Sensor Networks Chaiporn Jaikaeo Department of Computer Engineering Kasetsart University Materials taken from lecture slides by Karl and Willig

Typical Wireless Networks Base stations connected to wired backbone Base stations connected to wired backbone Mobile nodes communicate wirelessly to base stations Mobile nodes communicate wirelessly to base stations

Ad hoc Networks Networks without pre-configured infrastructure Networks without pre-configured infrastructure  require no hubs, access points, base stations  are instantly deployable  can be wired or wireless Initially targeted for military and emergency applications Initially targeted for military and emergency applications wiredmulti-hop wirelesswireless

Ad hoc Mode IEEE already provides support for ad hoc mode IEEE already provides support for ad hoc mode Computers can be connected without an access point Computers can be connected without an access point Only work with single hop Only work with single hop

Possible Applications for Ad hoc Networks Factory Floor Automation Disaster recovery Car-to-car communication

Problems/Challenges for Ad hoc Networks Lack of central entity for organization available Lack of central entity for organization available Limited range of wireless communication Limited range of wireless communication Mobility of participants Mobility of participants Battery-operated entities Battery-operated entities

Self-Organization Without a central entity, nodes must organize themselves into a network Without a central entity, nodes must organize themselves into a network Examples: Examples:  Medium access control  Finding a route

Characteristics of Ad hoc Networks Heterogeneity ― sensors, PDAs, laptops Heterogeneity ― sensors, PDAs, laptops Limited resources ― CPU, bandwidth, power Limited resources ― CPU, bandwidth, power Dynamic topology due to mobility and/or failure Dynamic topology due to mobility and/or failure  Mobile Ad hoc Networks (MANETs) A B C

Sensor Networks Participants in the previous examples were devices close to a human user, interacting with humans Participants in the previous examples were devices close to a human user, interacting with humans Alternative concept: Alternative concept: Instead of focusing interaction on humans, focus on interacting with environment  Network is embedded in environment  Nodes in the network are equipped with sensing and actuation to measure/influence environment  Nodes process information and communicate

Remote monitoring sensor field Traditional Sensors NetworkNetwork Local monitoring Data loggers

sensor field Wireless Sensors Sensors communicate with data logger via radio links Sensors communicate with data logger via radio links radio link Remote monitoring NetworkNetwork

Wireless Sensor Networks Wireless sensors + wireless network Wireless sensors + wireless network Sensor nodes (motes) deployed and forming an ad hoc network Sensor nodes (motes) deployed and forming an ad hoc network  Requires no hubs, access points  Instantly deployable Targeted applications Targeted applications  Emergency responses  Remote data acquisition Sensor network Sensor node/mote Internet Gateway Remote monitoring

WSN Platforms Most are based on IEEE (Wireless Low-Rate Personal Area Network) Most are based on IEEE (Wireless Low-Rate Personal Area Network) and many others…

WSN Application Examples Agriculture Agriculture  Humidity/temperature monitoring Civil engineering Civil engineering  Structural response  Disaster management Environmental sciences Environmental sciences  Habitat monitoring  Conservation biology

WSN in Telemetry Applications Sensor field Gateway wireless sensor node sensor GPRS Network or Internet Information Server Browser

Landslide Monitor Real deployment scenario… Real deployment scenario…

WSN Application Scenarios Facility management Facility management  Intrusion detection into industrial sites  Control of leakages in chemical plants, … Machine surveillance and preventive maintenance Machine surveillance and preventive maintenance  Embed sensing/control functions into places no cable has gone before  E.g., tire pressure monitoring Precision agriculture Precision agriculture  Bring out fertilizer/pesticides/irrigation only where needed Medicine and health care Medicine and health care  Post-operative or intensive care  Long-term surveillance of chronically ill patients or the elderly

WSN Application Scenarios Logistics Logistics  Equip goods (parcels, containers) with a sensor node  Track their whereabouts – total asset management  Note: passive readout might suffice – compare RF IDs Telematics Telematics  Provide better traffic control by obtaining finer-grained information about traffic conditions  Intelligent roadside  Cars as the sensor nodes

Sources of data: Measure data, report them “somewhere” Sources of data: Measure data, report them “somewhere”  Typically equip with different kinds of actual sensors Sinks of data: Interested in receiving data from WSN Sinks of data: Interested in receiving data from WSN  May be part of the WSN or external entity, PDA, gateway, … Actuators (actors): Control some device based on data, usually also a sink Actuators (actors): Control some device based on data, usually also a sink Roles of Participants in WSN WSN = WASN

Classifying Application Types Interaction patterns between sources and sinks classify application types Interaction patterns between sources and sinks classify application types  Event detection  Periodic measurement  Function approximation  Edge detection  Tracking

Deployment Options Dropped from aircraft Dropped from aircraft  Random deployment Well planned, fixed Well planned, fixed  Regular deployment Mobile sensor nodes Mobile sensor nodes  Can move to compensate for deployment shortcomings  Can be passively moved around by some external force (wind, water)  Can actively seek out “interesting” areas

Maintenance Options Feasible and/or practical to maintain sensor nodes? Feasible and/or practical to maintain sensor nodes?  Replace batteries  Unattended operation  Impossible but not relevant Energy supply Energy supply  Limited from point of deployment  Some form of recharging / energy scavenging

Characteristic Requirements Type of service of WSN Type of service of WSN  Not simply moving bits like another network  Rather: provide answers (not just numbers)  Geographic scoping are natural requirements Quality of service Quality of service Fault tolerance Fault tolerance Lifetime: node/network Lifetime: node/network Scalability Scalability Wide range of densities Wide range of densities Programmability Programmability Maintainability Maintainability

Required Mechanisms Multi-hop wireless communication Multi-hop wireless communication Energy-efficient operation Energy-efficient operation  Both for communication and computation, sensing, actuating Auto-configuration Auto-configuration  Manual configuration just not an option Collaboration & in-network processing Collaboration & in-network processing  Nodes in the network collaborate towards a joint goal  Pre-processing data in network (as opposed to at the edge) can greatly improve efficiency

Required Mechanisms Data centric networking Data centric networking  Focusing network design on data, not on node identifies (id-centric networking)  To improve efficiency Locality Locality  Do things locally (on node or among nearby neighbors) as much as possible Exploit tradeoffs Exploit tradeoffs  E.g., between invested energy and accuracy

MANET vs. WSN - Similarities MANET – Mobile Ad hoc Network MANET – Mobile Ad hoc Network Self-organization Self-organization Energy efficiency Energy efficiency (Often) Wireless multi-hop (Often) Wireless multi-hop

MANET vs. WSN - Differences Equipment: MANETs more powerful Equipment: MANETs more powerful Application-specific: WSNs depend much stronger on application specifics Application-specific: WSNs depend much stronger on application specifics Environment interaction: core of WSN, absent in MANET Environment interaction: core of WSN, absent in MANET Scale: WSN might be much larger (although contestable) Scale: WSN might be much larger (although contestable) Energy: WSN tighter requirements, maintenance issues Energy: WSN tighter requirements, maintenance issues

MANET vs. WSN - Differences Dependability/QoS: in WSN, individual node may be dispensable (network matters), QoS different because of different applications Dependability/QoS: in WSN, individual node may be dispensable (network matters), QoS different because of different applications Addressing: Data centric vs. id-centric networking Addressing: Data centric vs. id-centric networking

Wireless Fieldbuses Fieldbus: Fieldbus:  Network type invented for real-time communication, e.g., for factory-floor automation  Inherent notion of sensing/measuring and controlling Wireless fieldbus: Real-time communication over wireless Wireless fieldbus: Real-time communication over wireless

Wireless Fieldbuses vs. WSNs Scale – WSN often intended for larger scale Scale – WSN often intended for larger scale Real-time – WSN usually not intended to provide (hard) real-time guarantees as attempted by fieldbuses Real-time – WSN usually not intended to provide (hard) real-time guarantees as attempted by fieldbuses

Enabling Technologies for WSN Cost reduction Cost reduction  For wireless communication, simple microcontroller, system on chip, sensing, batteries Miniaturization Miniaturization  Some applications demand small size  “Smart dust” as the most extreme vision Energy scavenging Energy scavenging  Recharge batteries from ambient energy (light, vibration, …)

Conclusion MANETs and WSNs are challenging and promising system concepts MANETs and WSNs are challenging and promising system concepts Many similarities, many differences Many similarities, many differences Both require new types of architectures & protocols compared to “traditional” wired/wireless networks Both require new types of architectures & protocols compared to “traditional” wired/wireless networks In particular, application-specificness is a new issue In particular, application-specificness is a new issue

Demonstration

Sensor Modules IWING-MRF modules from IWING LAB IWING-MRF modules from IWING LAB  250 kbps 2.4GHz IEEE  12MHz Atmel ATMega328P microcontroller  Additional light and temperature sensors

Scenario Monitor station Sensor nodes measuring light intensity