Ad hoc and Sensor Networks Chaiporn Jaikaeo chaiporn.j@ku.ac.th - - PowerPoint PPT Presentation

Wireless Embedded Systems (0120442x) Ad hoc and Sensor Networks

Chaiporn Jaikaeo chaiporn.j@ku.ac.th Department of Computer Engineering Kasetsart University

Materials taken from lecture slides by Karl and Willig

Typical Wireless Networks



Base stations connected to wired backbone



Mobile nodes communicate wirelessly to base stations

Ad hoc Networks



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

wired multi-hop wireless wireless

802.11 Ad hoc Mode



IEEE 802.11 already provides support for ad hoc mode



Computers can be connected without an access point



Only work with single hop

Possible Applications for Ad hoc Networks

Factory Floor Automation Disaster recovery Car-to-car communication

Characteristics of Ad hoc Networks



Heterogeneity ― sensors, PDAs, laptops



Limited resources ― CPU, bandwidth, power



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



Alternative concept: Instead of focusing interaction on humans, focus

• n interacting with enviro

ronme nment nt

• Network is embedde

ded d in environment

• Nodes in the network are equipped with sensin

ing g and actuati ation

• n to measure/influence environment
• Nodes process information and communicate

Remote monitoring

sensor field

Traditional Sensors

Network Local monitoring Data loggers

sensor field

Wireless Sensors



Sensors communicate with data logger via radio links

radio link

Remote monitoring Network

Wireless Sensor Networks



Wireless sensors + wireless network



Sensor nodes (motes) deployed and forming an ad hoc network

• Requires no hubs, access points
• Instantly deployable



Targeted applications

• Emergency responses
• Remote data acquisition

Sensor network

Sensor node/mote

Internet

Gateway

Remote monitoring

WSN Platforms



Most are based on IEEE 802.15.4 (Wireless Low-Rate Personal Area Network)

and many others…

WSN Application Examples



Agriculture

• Humidity/temperature

monitoring



Civil engineering

• Structural response
• Disaster management



Environmental sciences

• Habitat monitoring
• Conservation biology

WSN in Telemetry Applications

Sensor field Gateway

wireless sensor node sensor sensor

GPRS Network

• r Internet

Information Server Browser

Landslide Monitor



Real deployment scenario…



Sources rces of data: Measure data, report them “somewhere”

• Typically equip with different kinds of actual sensors



Sinks ks of data: Interested in receiving data from WSN

• May be part of the WSN or external entity, PDA, gateway, …



Actua uato tors rs (actor

• rs)

s): Control some device based on data, usually also a sink

Roles of Participants in WSN

WSN = WASN

Classifying Application Types

 Inte

teract raction ion pa patt tter erns ns between sources and sinks classify application types

• Event detection
• Periodic measurement
• Function approximation
• Edge detection
• Tracking

Deployment Options



Dropped from aircraft

• Rando

dom m deployme

• yment

nt



Well planned, fixed

• Regular

ar deploy

• yme

ment nt



Mobi bile le 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?

• Replace batteries
• Unattended operation
• Impossible but not relevant



Energy supply

• Limited from point of deployment
• Some form of recharging / energy scavenging

Characteristic Requirements



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



Fault tolerance



Lifetime: node/network



Scalability



Wide range of densities



Programmability



Maintainability

Required Mechanisms



Multi-hop wireless communication



Energy-efficient operation

• Both for communication and computation,

sensing, actuating



Auto-configuration

• Manual configuration just not an option



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

• Focusing network design on data, not on node

identifies (id-centric networking)

• To improve efficiency



Locality

• Do things locally (on node or among nearby

neighbors) as much as possible



Exploit tradeoffs

• E.g., between invested energy and accuracy

MANET vs. WSN - Similarities



MANET – Mobile Ad hoc Network



Self-organization



Energy efficiency



(Often) Wireless multi-hop

MANET vs. WSN - Differences



Eq Equipment: ipment: MANETs more powerful



Applicati lication

• n-spe

specific: cific: WSNs depend much stronger on application specifics



En Environ ironment ment in interacti raction:

• n: core of WSN,

absent in MANET



Sca cale: le: WSN might be much larger (although contestable)



En Energy: rgy: WSN tighter requirements, maintenance issues

MANET vs. WSN - Differences



Dependabili pendability/QoS: ty/QoS: in WSN, individual node may be dispensable (network matters), QoS different because of different applications



Addressing: dressing: Data centric vs. id-centric networking

Enabling Technologies for WSN



Cost reduction

• For wireless communication, simple

microcontroller, system on chip, sensing, batteries



Miniaturization

• Some applications demand small size
• “Smart dust” as the most extreme vision



Energy scavenging

• Recharge batteries from ambient energy (light,

vibration, …)

Conclusion



MANETs and WSNs are challenging and promising system concepts



Many similarities, many differences



Both require new types of architectures & protocols compared to “traditional” wired/wireless networks



In particular, application-specificness is a new issue

Demonstration

Sensor Modules



IWING-MRF modules from IWING LAB

• 250 kbps 2.4GHz IEEE 802.15.4
• 12MHz Atmel ATMega328P microcontroller
• Additional light and temperature sensors

Scenario

Monitor station Sensor nodes measuring light intensity