Ad hoc and Sensor Networks

brainybootsMobile - Wireless

Nov 21, 2013 (3 years and 7 months ago)

67 views

Protocols and Applications for
Wireless Sensor Networks (204525)


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
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


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

or Internet

Information

Server

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


M
obile
A
d hoc
Net
work


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