wireless embedded systems (0120442x) ad hoc and sensor networks chaiporn jaikaeo [email protected]...
TRANSCRIPT
Wireless Embedded Systems(0120442x)
Ad hoc and Sensor Networks
Chaiporn [email protected]
Department of Computer EngineeringKasetsart 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 wirelesswireless
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
ad ho
c
ad ho
c
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
BC
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 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
Remotemonitoring
sensor field
Traditional Sensors
NetworkNetwork
Localmonitoring
Data loggers
sensor field
Wireless Sensors Sensors communicate with data
logger via radio links
radio linkRemote
monitoring
NetworkNetwork
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
Remotemonitoring
WSN Platforms Most are based on IEEE 802.15.4
(Wireless Low-Rate Personal Area Network)
and many others…
WSN Application Examples Agriculture
Humidity/temperaturemonitoring
Civil engineering Structural response Disaster management
Environmental sciences Habitat monitoring Conservation biology
WSN in Telemetry Applications
Sensor field
Gateway
wireless sensor node
sensor sensor
GPRSNetwork
or Internet
GPRSNetwork
or Internet
InformationServer
Browser
Landslide Monitor Real deployment scenario…
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 May be part of the WSN or external entity, PDA,
gateway, …
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 Event detection Periodic measurement Function approximation Edge detection Tracking
Deployment Options Dropped from aircraft
Random deployment Well planned, fixed
Regular deployment 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? 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 Equipment: MANETs more powerful Application-specific: WSNs depend
much stronger on application specifics
Environment interaction: core of WSN, absent in MANET
Scale: WSN might be much larger (although contestable)
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
Addressing: 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