WiseNet technology

8/12/2019 WiseNet technology

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WISENET(WIRELESS SENSOR NETWORK)


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ABSTRACT

WISENET is a wireless sensor network that monitors the environmental

conditions such as light, temperature, and humidit ! This network is comprised o" nodes

called #motes$ that "orm an ad%hoc network to transmit this data to a computer that

"unction as a server! The server stores the data in a data&ase where it can later &e

retrieved and anal 'ed via a we&%&ased inter"ace! The network works success"ull with

an implementation o" one sensor mote!


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Introduction:

The "irst goal o" WISENET is to create a new hardware plat"orm to

take advantage o" newer microcontrollers with greater "unctionalit and more "eatures!

This involves selecting the hardware, designing the motes, and porting Tin (S! (nce the

plat"orm is completed and Tin (S was ported to it, the ne)t stage is to use this plat"orm

to create a small%scale s stem o" wireless networked sensors!

Wireless sensor%actuator networks can provide the a&ilit to continuousl monitor

the integrit o" structures in real%time, detect damage at an earl stage, and provide

ro&ustness in the case o" catastrophic "ailures with a "raction o" cost associated with

toda *s wired networks! +owever, sensor%actuator networks re uire a new paradigm o"

computing-one, which e)plicitl addresses less capa&le hardware, unrelia&le

communication with, limited &andwidth, and severe energ constraints! The algorithms

and so"tware tools will "acilitate monitoring and protection o" civil structures using such

networks!

Smart environments represent the ne)t evolutionar development step in &uilding,

utilities, industrial, home, ship&oard, and transportation s stems automation! .ike an

sentient organism, the smart environment relies "irst and "oremost on sensor data "rom

the real world! Sensor data comes "rom multiple sensors o" di""erent modalities in

distri&uted locations! The smart environment needs in"ormation a&out its surroundings as

well as a&out its internal workings/ this is captured in &iological s stems & the

distinction &etween exteroceptors and proprioceptors.

The challenges in the hierarch o"0 detecting the relevant uantities, monitoring

and collecting the data, assessing and evaluating the in"ormation, "ormulating meaning"ul

user displa s, and per"orming decision%making and alarm "unctions are enormous! The

in"ormation needed & smart environments is provided & 1istri&uted Wireless Sensor

Networks, which are responsi&le "or sensing as well as "or the "irst stages o" the

processing hierarch ! The importance o" sensor networks is highlighted & the num&er o"


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recent "unding initiatives, including the 1AR2A SENSIT program, militar programs,

and NS3 2rogram Announcements!

The "igure shows the comple)it o" wireless sensor networks, which generall

consist o" a data ac uisition network and a data distri&ution network, monitored and

controlled & a management center! The plethora o" availa&le technologies makes even

the selection o" components di""icult, let alone the design o" a consistent, relia&le, ro&ust

overall s stem!

The stud o" wireless sensor networks is challenging in that it re uires an enormous

&readth o" knowledge "rom an enormous variet o" disciplines! In this chapter we outline

communication networks, wireless sensor networks and smart sensors, ph sical

transduction principles, commerciall availa&le wireless sensor s stems, sel"organi'ation,

signal processing and decision%making, and "inall some concepts "or home automation!


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COMMUNICATION NETWORKS

The stud o" communication networks can encompass several ears at the college or

universit level! To understand and &e a&le to implement sensor networks, however,

several &asic primar concepts are su""icient!

Network Topolo !

The &asic issue in communication networks is the transmission o" messages to achieve a

prescri&ed message throughput 45uantit o" Service6 and 5ualit o" Service 45oS6! 5oS

can &e speci"ied in terms o" message dela , message due dates, &it error rates, packet

loss, economic cost o" transmission, transmission power, etc! 1epending on 5oS, the

installation environment, economic considerations, and the application, one o" several

&asic network topologies ma &e used!

A communication network is composed o" nodes, each o" which has computing power and can transmit and receive messages over communication links, wireless or

ca&led! The &asic network topologies are shown in the "igure and include "ull connected,

mesh, star, ring, tree, &us! A single network ma onsist o" several interconnected su&nets

o" di""erent topologies! Networks are "urther classi"ied as .ocal Area Networks 4.AN6,

e!g! inside one &uilding, or Wide Area Networks 4WAN6, e!g! &etween &uildings!


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"ull! connected network# su""er "rom pro&lems o" N2%comple)it 78are 9:;:


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Co unic%tion *rotocol# %nd Routin

The topics o" communication protocols and routing are comple) and re uire much stud !

Some &asics use"ul "or understanding sensor nets are presented here! +e%der#, Each

message generall has a header identi" ing its source node, destination node, length o"

the data "ield, and other in"ormation! This is used & the nodes in proper routing o" themessage! In encoded messages, parit &its ma &e included! In packet routing networks ,

each message is &roken into packets o" "i)ed length! The packets are transmitted

separatel through the network and then reassem&led at the destination! The "i)ed packet

length makes "or easier routing and satis"action o" 5oS! 8enerall , voice

communications use circuit switching, while data transmissions use packet routing!

separatel through the network and then reassem&led at the destination! The "i)ed packet

length makes "or easier routing and satis"action o" 5oS! 8enerall , voice

communications use circuit switching, while data transmissions use packet routing!

In addition to the in"ormation content messages, in some protocols 4e!g! 311I%

see &elow6 the nodes transmit special frames to report and identi" "ault conditions! This

can allow network recon"iguration "or "ault recover ! (ther special "rames might include

route discover packets or ferrets that "low through the network, e!g! to identi" shortest


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paths, "ailed links, or transmission cost in"ormation! In some schemes, the "erret returns

to the source and reports the &est path "or message transmission!

When a node desires to transmit a message, handshaking protocols with the

destination node are used to improve relia&ilit ! The source and destination might

transmit alternatel as "ollows0 re uest to send, read to receive, send message, message

received! +andshaking is used to guarantee 5oS and to retransmit messages that were not

properl received!

Switc$in

=ost computer networks use a store-and-forward switching techni ue to control the

"low o" in"ormation! Then, each time a packet reaches a node, it is completel &u""ered in

local memor , and transmitted as a whole! =ore sophisticated switching techni ues

include wormhole , which splits the message into smaller units known as "low control

units or "lits! The header "lit determines the route! As the header is routed, the remaining

"lits "ollow it in pipeline "ashion! This techni ue currentl achieves the lowest message

latenc ! Another popular switching scheme is virtual-cut-through ! +ere, when the header

arrives at a node, it is routed without waiting "or the rest o" the packet! 2ackets are

&u""ered either in so"tware &u""ers in memor or in hardware &u""ers, and various sorts o" &u""ers are used including edge &u""ers, central &u""ers, etc!

Multiple Acce## *rotocol# ! When multiple nodes desire to transmit, protocols are

needed to avoid collisions and lost data! In the A.(+A scheme, "irst used in the 9:;?*s

at the @niversit o" +awaii, a node simpl transmits a message when it desires! I" it

receives an acknowledgement, all is well! I" not, the node waits a random time and

retransmits the message!

In Frequency Division Multiple Access 431=A6, di""erent nodes have di""erent

carrier "re uencies! Since "re uenc resources are divided, this decreases the &andwidth

availa&le "or each node! 31=A also re uires additional hardware and intelligence at each

node! In Code Division Multiple Access 4C1=A6, a uni ue code is used & each node to

encode its messages! This increases the comple)it o" the transmitter and the receiver! In

ime Division Multiple Access 4T1=A6, the R3 link is divided on a time a)is, with each


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node &eing given a predetermined time slot it can use "or communication! This decreases

the sweep rate, &ut a ma or advantage is that T1=A can &e implemented in so"tware! All

nodes re uire accurate, s nchroni'ed clocks "or T1=A!

Open S!#te # Interconnection Re&erence Model (OSI-RM),

The International Standards (rgani'ation 4IS(6 (SI R= architecture speci"ies the

relation &etween messages transmitted in a communication network and applications

programs run & the users! The development o" this open standard has encouraged the

adoption & di""erent developers o" standardi'ed compati&le s stems inter"aces! The

"igure shows the seven la ers o" (SI R=! Each la er is sel"%contained, so that it can &e

modi"ied without undul a""ecting other la ers! The Transport .a er provides error

detection and correction! Routing and "low control are per"ormed in the Network .a er!

The 2h sical .a er represents the actual hardware communication link interconnections!The Applications .a er represents programs run & users!

Routin , Since a distri&uted network has multiple nodes and services man messages,

and each node is a shared resource, man decisions must &e made! There ma &e multiple

paths "rom the source to the destination! There"ore, message routing is an important topic!

The main per"ormance measures a""ected & the routing scheme are throughput 4 uantit

o" service6 and average packet dela 4 ualit o" service6! Routing schemes should also

avoid &oth deadlock and livelock 4see &elow6!


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Routing methods can &e "i)ed 4i!e! pre%planned6, adaptive, centrali'ed, distri&uted,

&roadcast, etc! 2erhaps the simplest routing scheme is the token ring 7Sm the 9:::

+ere, a simple topolog and a straight"orward "i)ed protocol result in ver good

relia&ilit and precomputa&le 5oS! A token passes continuousl around a ring topolog !

When a node desires to transmit, it captures the token and attaches the message! As the

token passes, the destination reads the header, and captures the message! In some

schemes, it attaches a >message received* signal to the token, which is then received &

the original source node! Then, the token is released and can accept "urther messages!

The token ring is a completel decentrali'ed scheme that e""ectivel uses T1=A!

Though this scheme is ver relia&le, one can see that it results in a waste o" network

capacit ! The token must pass once around the ring "or each message! There"ore, there

are various modi"ications o" this scheme, including using several tokens, etc!

"i.ed routin #c$e e# o"ten use Routing Ta&les that dictate the ne)t node to &e

routed to, given the current message location and the destination node! Routing ta&les can

&e ver large "or large networks, and cannot take into account real%time e""ects such as

"ailed links, nodes with &acked up ueues, or congested links!

Ad%pti/e routin #c$e e# depend on the current network status and can take

into account various per"ormance measures, including cost o" transmission over a given

link, congestion o" a given link, relia&ilit o" a path, and time o" transmission! The can

also account "or link or node "ailures!

Routing algorithms can &e &ased on various network anal sis and graph theoretic

concepts in Computer Science 4e!g! A%star tree search6, or in (perations Research

7Bronson 9::;< including shortest%route, ma)imal "low, and minimum%span pro&lems!

Routing is closel associated with d namic programming and the optimal control

pro&lem in "eed&ack control theor ! Shortest 2ath routing schemes "ind the shortest path

"rom a given node to the destination node! I" the cost, instead o" the link length, is

associated with each link, these algorithms can also compute minimum cost routes! These

algorithms can &e centrali'ed 4"ind the shortest path "rom a given node to all other nodes6

or decentrali'ed 4"ind the shortest path "rom all nodes to a given node6! There are certain

well%de"ined algorithms "or shortest path routing, including the e""icient 1i kstra

algorithm , which has pol nomial comple)it ! The Bellman%3ord algorithm "inds the path


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with the least num&er o" hops! Routing schemes &ased on competitive game theoretic

notions have also &een developed !

0e%dlock %nd Li/elock, .arge%scale communication networks contain c cles 4circular

paths6 o" nodes! =oreover, each node is a shared resource that can handle multiple

messages "lowing along di""erent paths! There"ore, communication nets are suscepti&le to

deadlock , wherein all nodes in a speci"ic c cle have "ull &u""ers and are waiting "or each

other! Then, no node can transmit &ecause no node can get "ree &u""er space, so all

transmission in that c cle comes to a halt! !ivelock , on the other hand, is the condition

wherein a message is continuall transmitted around the network and never reaches its

destination! .ivelock is a de"icienc o" some routing schemes that route the message to

alternate links when the desired links are congested, without taking into account that themessage should &e routed closer to its "inal destination! =an routing schemes are

availa&le "or routing with deadlock and livelock avoidance 7e!g! 1uato 9::

"low Control, In ueuing networks, each node has an associated ueue or &u""er that can

stack messages! In such networks, "low control and resource assignment are important!

The o& ectives o" "low control are to protect the network "rom pro&lems related to

overload and speed mismatches, and to maintain 5oS, e""icienc , "airness, and "reedom

"rom deadlock! I" a given node A has high priorit , its messages might &e pre"erentiall

routed in ever case, so that competing nodes are choked o"" as the tra""ic o" A increases!

3air routing schemes avoid this! There are several techni ues "or "low control0 In "uffer

management , certain portions o" the &u""er space are assigned "or certain purposes! In

choke packet schemes , an node sensing congestion sends choke packets to other nodes

telling them to reduce their transmissions! #sarithmic schemes have a "i)ed num&er o"

>permits* "or the network! A message can &e sent onl i" a permit is availa&le! In window

or kan"an schemes, the receiver grants >credits* to the sender onl i" it has "ree &u""er

space! @pon receiving a credit, the sender can transmit a message! In ransmission

Control $rotocol % C$& schemes 4Tahoe and Reno6 a source linearl increases its

transmission rate as long as all its sent messages are acknowledged "or! When it detects a


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lost packet, it e)ponentiall decreases its transmission rate! Since lost packets depend on

congestion, TC2 automaticall decreases transmissions when congestion is etected!

*ower M%n% e ent

With the advent o" ad hoc networks o" geographicall distri&uted sensors in remote site

environments 4e!g! sensors dropped "rom aircra"t "or personnel vehicle surveillance6,

there is a "ocus on increasing the li"etimes o" sensor nodes through power generation,

power conservation, and power management! Current research is in designing small

=E=S 4microelectromechanical s stems6 R3 components "or transceivers, including

capacitors, inductors, etc! The limiting "actor now is in "a&ricating microsi'ed inductors!

Another thrust is in designing =E=S power generators using technologies includingsolar, vi&ration 4electromagnetic and electrostatic6, thermal, etc!

R3%I1 4R3 identi"ication6 devices are transponder microcircuits having an .%C

tank circuit that stores power "rom received interrogation signals, and then uses that

power to transmit a response! 2assive tags have no on&oard power source and limited

on&oard data storage, while active tags have a &atter and up to 9=& o" data storage! R3%

I1 operates in a low "re uenc range o" 9??k+'%9!D=+' or a high "re uenc range o"

:?? =+'% !F8+', which has an operating range up to G?m! R3%I1 tags are ver

ine)pensive, and are used in manu"acturing and sales inventor control, container

shipping control, etc! R3%I1 tags are installed on water meters in some cities, allowing a


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metering vehicle to simpl drive & and remotel read the current readings! The are also

&e used in automo&iles "or automatic toll collection!

=eanwhile, so"tware power management techni ues can greatl decrease the

power consumed & R3 sensor nodes! T1=A is especiall use"ul "or power conservation,

since a node can power down or >sleep* &etween its assigned time slots, waking up in

time to receive and transmit messages!

The re uired transmission power increases as the s uare o" the distance &etween

source and destination! There"ore, multiple short message transmission hops re uire less

power than one long hop! In "act, i" the distance &etween source and destination is ' , the

power re uired "or single%hop transmission is proportional to '( ! I" nodes &etween source

and destination are taken advantage o" to transmit n short hops instead, the power

re uired & each node is proportional to '()n(. This is a strong argument in "avor o"

distri&uted networks with multiple nodes, i!e! nets o" the mesh variet !

A current topic o" research is active power control* where& each node cooperates

with all other nodes in selecting its individual transmission power level 7Humar ??9

This is a decentrali'ed "eed&ack control pro&lem! Congestion is increased i" an node

uses too much power, &ut each node must select a large enough transmission range that

the network remains connected! 3or n nodes randoml distri&uted in a disk, the network


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is as mptoticall connected with pro&a&ilit one i" the transmission range r o" all nodes

is selected using

1,1,2, Network Structure %nd +ier%rc$ic%l Network#

Routing ta&les "or distri&uted networks increase e)ponentiall as nodes are added! An n )

m mesh network has nm links, and there are multiple paths "rom each source to each

destination! +ierarchical network structures simpli" routing, and also are amena&le to

distri&uted signal processing and decision%making, since some processing can &e done at

each hierarchical la er!

It has &een shown 7.ewis and A&dallah 9::G< that a "ull connected network has ,$ %hard comple)it , while imposing routing protocols & restricting the allowed paths to

o&tain a reentrant flow topolog results in pol nomial comple)it ! Such streamlined

protocols are natural "or hierarchical networks!

Multic%#t S!#te # in mesh networks use a hierarchical leader%&ased scheme "or message

transmission 7Chen et al! ???

the same two messages &eing routed using a multicast protocol! Note that the total

transmission paths are signi"icantl shorter! =ulticast has &een implemented using tree

&ased and path%&ased schemes!


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+ier%rc$ic%l Network#, =uch work has &een done on "ormal hierarchical structures "or

distri&uted networks! Cao 79:::< studies how to determine optimal con"igurations "or

hierarchical routing! Shi 79::D< anal 'es hierarchical sel"healing rings! Shah%+e dari

7 ??9< shows the importance o" a consistent num&ering scheme in hierarchical s stems,

which allows "or a simpli"ied tree&ased routing scheme!

The "igure shows a &asic F% element ring element consisting o" "our nodes and

"our links! It shows

two wa s o" connecting these two rings, which results in two mesh networks o" di""erent

structures! The "irst network consists o" alternating one%wa streets, while the secondconsists o" alternatingdirection vortices! It is interesting to anal 'e these two structures

"rom the point o" view o" the notions o" "low "ield divergence and curl!

In an network, the phenomenon o" edge "inding means that much o" the routing

power o" peripheral stations is wasted &ecause peripheral links are unused! Thus,

messages tend to re"lect o"" the &oundar into the interior or to move parallel to the

peripher 7 !W! Smith, Rand Corp! 9: F

connects the nodes at one edge o" the network to nodes at the opposite edge! The "igure

shows the standard =anhattan geometr as well as a =anhattan net &uilt "rom the

alternating one%wa street mesh ust constructed!

As nodes are added, the num&er o" links increases e)ponentiall ! This makes "or

N2%comple)it pro&lems in routing and "ailure recover ! To simpli" network structure,

we can use hierarchical clustering techni ues! The hierarchical structure must &e

consistent , that is, it must have the same structure at each level! The "igure shows a F)F

mesh net and also a clustering into "our groups! Note that the clustered structure has a

dual ring S+R topolog ! To reduce the routing comple)it , we can disa&le one o"

the rings and o&tain a ring structure!

The ne)t "igure shows an J)J mesh net! Shown "irst are all the links, and then the

hierarchical clustering with some links disa&led to reduce comple)it ! We have chosen to


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keep the outer ring at each level! Note that the clockwise ring structure is the same at

each level, resulting in a regular hierarch !

Routing is ver eas in this hierarchical network 7Swam ??G

a consistent num"ering scheme ! 3or e)ample num&er the groups as 9, ,G,F &eginning in

the top le"t and going clockwise! This is done at each level! Then, re"erring to the J)J

mesh net in the "igure, node 9FG, shown in the "igure, is in the top le"t F)F group, within

which it is in the "ourth ) group, within which it is the third node! @sing this num&er

scheme one ma construct a simple routing scheme wherein the same &asic routing

algorithm is repeated at each level o" the hierarch ! This is not unlike uadtree routing in

mo&ile ro&ot path planning! 3ailure recover is also straight"orward! I" a link "ails, one

ma simpl switch in one o" the disa&led links to take over! Code "or this is ver eas to

write!

0i#tri uted Routin 3 0eci#ion'M%kin 3 %nd 0S*, It is natural in routing and "ailure

recover "or these hierarchical networks to designate the entr node "or each group as a

group leader. This node must make additional decisions &e ond those o" the other nodes,

including resource availa&ilit "or deadlock voidance, disa&led link activation "or "ailure

recover , and so on! This la s a ver natural "ramework "or distri&uted decision%making

and digital signal processing 41S26, wherein a group leader processes the data "rom the

group prior to transmitting it! The group leader "or communications should &e the entry

node o" each group, while the group leader "or 1S2 should &e the exit node "or each

group!

! +i#toric%l 0e/elop ent %nd St%nd%rd#

=uch o" this in"ormation is taken "rom 72C Tech 8uide


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Et$ernet ! The Ethernet was developed in the mid 9:;?*s & Kero), 1EC, and Intel, and

was standardi'ed in 9:;:! The Institute o" Electrical and Electronics Engineers 4IEEE6

released the o""icial Ethernet standard IEEE J? !G in 9:JG! The 3ast Ethernet operates at

ten times the speed o" the regular Ethernet, and was o""iciall adopted in 9::D! It

introduces new "eatures such as "ull%duple) operation and auto%negotiation! Both these

standards use IEEE J? !G varia&le%length "rames having &etween F and 9D9F%& te

packets!

Token Rin ! In 9:JF IB= introduced the F=&it s token ring network! The s stem was o"

high ualit and ro&ust, &ut its cost caused it to "all &ehind the Ethernet in popularit !

IEEE standardi'ed the token ring with the IEEE J? !D speci"ication! The 3i&er

1istri&uted 1ata Inter"ace 4311I6 speci"ies a 9??=&it s token%passing, dual%ring .ANthat uses "i&er optic ca&le! It was developed & the American National Standards Institute

4ANSI6 in the mid 9:J?s, and its speed "ar e)ceeded current capa&ilities o" &oth Ethernet

and IEEE J? !D!

4i % it Et$ernet ! The 8iga&it Ethernet Alliance was "ounded in 9:: , and the 8iga&it

Ethernet standards were rati"ied in 9:::, speci" ing a ph sical la er that uses a mi)ture

o" technologies "rom the original Ethernet and "i&er optic ca&le technologies "rom 311I!

Client'Ser/er networks &ecame popular in the late 9:J?*s with the replacement o" large

main"rame computers & networks o" personal computers! Application programs "or

distri&uted computing environments are essentiall divided into two parts0 the client or

"ront end, and the server or &ack end! The user*s 2C is the client and more power"ul

server machines inter"ace to the network!

*eer'to'*eer networkin architectures have all machines with e uivalent capa&ilities

and responsi&ilities! There is no server, and computers connect to each other, usuall

using a &us topolog , to share "iles, printers, Internet access, and other resources!

*eer'to'*eer Co putin is a signi"icant ne)t evolutionar step over 2 2 networking!

+ere, computing tasks are split &etween multiple computers, with the result &eing

assem&led "or "urther consumption! 2 2 computing has sparked a revolution "or the


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Internet Age and has o&tained considera&le success in a ver short time! The Napster

=2G music "ile sharing application went live in Septem&er 9:::, and attracted more than

? million users & mid ???!

561,77 Wirele## Loc%l Are% Network, IEEE rati"ied the IEEE J? !99 speci"ication in

9::; as a standard "or W.AN! Current versions o" J? !99 4i!e! J? !99&6 support

transmission up to 99=&it s! Wi3i, as it is known, is use"ul "or "ast and eas networking

o" 2Cs, printers, and other devices in a local environment, e!g! the home! Current 2Cs and

laptops as purchased have the hardware to support Wi3i! 2urchasing and installing a

Wi3i router and receivers is within the &udget and capa&ilit o" home 2C enthusiasts!

8luetoot$ was initiated in 9::J and standardi'ed & the IEEE as Wireless 2ersonal Area Network 4W2AN6 speci"ication IEEE J? !9D! Bluetooth is a short range R3 technolog

aimed at "acilitating communication o" electronic devices &etween each other and with

the Internet, allowing "or data s nchroni'ation that is transparent to the user! Supported

devices include 2Cs, laptops, printers, o sticks, ke &oards, mice, cell phones, 21As, and

consumer products! =o&ile devices are also supported! 1iscover protocols allow new

devices to &e hooked up easil to the network! Bluetooth uses the unlicensed !F 8+'

&and and can transmit data up to 9=&it s, can penetrate solid non%metal &arriers, and has

a nominal range o" 9?m that can &e e)tended to 9??m! A master station can service up to

; simultaneous slave links! 3orming a network o" these networks, e!g! a piconet, can

allow one master to service up to ?? slaves!

Currentl , Bluetooth development kits can &e purchased "rom a variet o"

suppliers, &ut the s stems generall re uire a great deal o" time, e""ort, and knowledge

"or programming and de&ugging! 3orming piconets has not et &een streamlined and is

undul di""icult!

+o e R" was initiated in 9::J and has similar goals to Bluetooth "or W2AN! Its goal is

shared data voice transmission! It inter"aces with the Internet as well as the 2u&lic

Switched Telephone Network! It uses the !F 8+' &and and has a range o" D? m, suita&le


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"or home and ard! A ma)imum o" 9 ; nodes can &e accommodated in a single network!

Ir0A is a W2AN technolog that has a short%range, narrow%transmission%angle &eam

suita&le "or aiming and selective reception o" signals!

, WIRELESS SENSOR NETWORKS

Sensor networks are the ke to gathering the in"ormation needed & smart environments,

whether in &uildings, utilities, industrial, home, ship&oard, transportation s stems

automation, or elsewhere! Recent terrorist and guerilla war"are countermeasures re uire

distri&uted networks o" sensors that can &e deplo ed using, e!g! aircra"t, and have sel"%

organi'ing capa&ilities! In such applications, running wires or ca&ling is usuall

impractical! A sensor network is re uired that is "ast and eas to install and maintain!

IEEE 7297 %nd S %rt Sen#or#

Wireless sensor networks satis" these re uirements! 1esira&le "unctions "or sensor nodes

include0 ease o"

installation, sel"%identi"ication, sel"%diagnosis, relia&ilit , time awareness "or coordination

with other nodes, some so"tware "unctions and 1S2, and standard control protocols and

network inter"aces 7IEEE 9FD9 E)po, ??9

There are man sensor manu"acturers and man networks on the market toda ! It

is too costl "or manu"acturers to make special transducers "or ever network on the

market! 1i""erent components made & di""erent manu"acturers should &e compati&le!

There"ore, in 9::G the IEEE and the National Institute o" Standards and Technolog

4NIST6 &egan work on a standard "or Smart Sensor Networks! IEEE 9FD9, the Standard

"or Smart Sensor Networks was the result! The o& ective o" this standard is to make it

easier "or di""erent manu"acturers to develop smart sensors and to inter"ace those devices

to networks!

S %rt Sen#or3 irtu%l Sen#or, =a or components include STI=, TE1S, TII, and

NCA2 as detailed in the "igure! A ma or outcome o" IEEE 9FD9 studies is the "ormali'ed

concept o" a mart ensor ! A smart sensor is a sensor that provides e)tra "unctions


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&e ond those necessar "or generating a correct representation o" the sensed uantit

73rank ???

making alarm "unctions! A general model o" a smart sensor is shown in the "igure!

(& ectives "or smart sensors include moving the intelligence closer to the point o"

measurement/ making it cost e""ective to integrate and maintain distri&uted sensor

s stems/ creating a con"luence o" transducers, control, computation, and communications

towards a common goal/ and seamlessl inter"acing numerous sensors o" di""erent t pes!

The concept o" a L irtual ensor is also depicted! A virtual sensor is the ph sical

sensor transducer, plus the associated signal conditioning and digital signal processing

41S26 re uired to o&tain relia&le estimates o" the re uired sensor in"ormation! The

virtual sensor is a component o" the smart sensor!

Tr%n#ducer# %nd *$!#ic%l Tr%n#duction *rinciple#

A transducer is a device that converts energ "rom one domain to another! In our

application, it converts the uantit to &e sensed into a use"ul signal that can &e directl

measured and processed! Since much signal conditioning 4SC6 and digital signal

processing 41S26 is carried out & electronic circuits, the outputs o" transducers that are

use"ul "or sensor networks are generall voltages or currents! Sensor transduction ma

&e carried out using physical principles* some o" which we review here!

=icroelectromechanical S stems 4=E=S6 sensors are & now ver well developed and

are availa&le "or most sensing applications in wireless networks! Re"erences "or this

section include 3rank 7 ???T$e *ie;ore#i#ti/e E&&ect converts an applied strain to a change in resistance that can &e

sensed using electronic circuits such as the Wheatstone Bridge 4discussed later6!


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1iscovered & .ord Helvin in 9JD , the relationship is , ' ' M M with ' the

resistance, M the strain, and the gauge "actor which depends on uantities such as the

resistivit and the 2oisson* ratio o" the material! There ma &e a uadratic term in M "or

some materials! =etals and semiconductors e)hi&it pie'oresistivit ! The pie'oresistive

e""ect in silicon is enhanced & doping with &oron 4pt pe silicon can have a gauge "actor

up to ??6! With semiconductor strain gauges, temperature compensation is important!

T$e *ie;oelectric E&&ect , discovered & the Curies in 9JJ?, converts an applied

stress 4"orce6 to a charge separation or potential di""erence! 2ie'oelectric materials

include &arium titanate, 2 T, and single%cr stal uart'! The relation &etween the change

in "orce F and the change in voltage / is given & M , where k is proportional to the

material charge sensitivit coe""icients and the cr stal thickness, and inversel

proportional to the cr stal area and the material relative permittivit ! The pie'oelectrice""ect is reversi&le, so that a change in voltage also generates a "orce and a corresponding

change in thickness! Thus the same device can &e "oth a sensor and an actuator.

Com&ined sensor actuators are an intriguing topic o" current research! F k / M M

Tunnelin Sen#in depends on the e)ponential relationship &etween the

tunneling current # and the tip sur"ace separation 0 given & , where k depends on the

tunnel &arrier height in ev! Tunneling is an e)tremel accurate method o" sensing

nanometer%scale displacements, &ut its highl nonlinear nature re uires the use o"

"eed&ack control to make it use"ul!

S!#te 0e#cription:

There are two primar su&s stems 41ata Anal sis and 1ata

Ac uisition6 comprised o" three ma or components 4Client, Server, Sensor =ote

Network6!

*ri %r! Su #!#te #:

There are two top%level su&s stems O

Data Analysis


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Data Acquisition.

0%t% An%l!#i#:

This su&s stem is so"tware%onl 4relative to WISENET6! It relied on e)isting

Internet and we& 4+TT26 in"rastructure to provide communications &etween the Client and Server

components! The "ocus o" this su&s stem was to selectivel present the collected environmental data

to the end user in a graphical manner!

0%t% Ac


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0%t% An%l!#i# Su #!#te 0%t% AcOutput#


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Re


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"i ure 2: Ser/er Co ponent 8lock 0i% r%

Sen#or Mote#:

The primar "ocus o" WISENET is the development o" the Sensor =ote

Network component! It is the component responsi&le "or collecting and transmitting raw

environmental data to the Server! There is also the potential "or the motes to receive commands

"rom the Server, although that "unctionalit ma not &e implemented in WISENET! @ses "or this

"eature would include server%&ased s nchroni'ation and wireless network reprogramming!

This component consists o" two parts! The "irst is the sensor mote! The primar

purpose o" the sensor mote is to collect and transmit raw environmental data! When not doing this, it

went into a low%power idle mode to conserve energ ! Another aspect o" the sensor motes involved ad%

hoc networking and ma &e "or multi%hop routing/


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The gatewa mote is the second part o" the Sensor =ote Network! Its purpose is to

serve as the liaison &etween the Server and the Sensor =ote Network and deliver all the data packets

to Wise1B! In theor &oth standard and gatewa motes could &e implemented on the same hardware

2CB and with the same so"tware! 3or WISENET, however, resource and time constraints necessitated

the use o" slightl di""erent hardware and so"tware con"igurations "or gatewa versus standard motes,

as descri&ed &elow!

+%rdw%re 0e#i n:

The selection o" components "or the sensor motes is a critical process in

the development o" WISENET! 8reat "unctionalit and low power are two o" the highest

priorities in evaluating the "itness o" &oth the microcontroller and the sensor candidates!

WISENET is introduced to the new state%o"%the%art Chipcon CC9?9? microcontroller

with integrated R3 transceiver! A"ter a little research it was decided the CC9?9? would

make the per"ect microcontroller!

It had the "ollowing "eature list0

9! (ptimi'ed J?D9%core

! Active 49F!J mA6, Idle 4 : MA6 and sleep 4?! MA6 power modes

G! G kB "lash memor

F! kB Q9 J & tes SRA=

D! Three channel 9?%&it A1C

! 3our timers Two 2W= s


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;! +ardware 1ES encr ption decr ption

J! +ardware random &it%generator

:! 3ull integrated @+3 R3 transceiver 4FGG =+' J J =+' nominal6

_ 2rogramma&le output power 4% ? to 9? dBm6

_ .ow current consumption 499!: mA "or RK, 9;!? mA "or TK at ?dBm6

_ RSSI output that can &e sampled & the on%chip A1C

WISENET includes a socketed evaluation &oard 4CC9?9?EB6 and two

evaluation modules 4CC9?9?E=6! The evaluation &oard provided access to all o" the

analog and digital pins on the CC9?9?, as well as two serial ports, a parallel

programming port, R3 network anal sis ports, and other peripherals! Each evaluation

module "eatured the CC9?9?, R3 network hardware, an antenna port, and an analog

temperature sensor! The modules connected to the evaluation &oard via two T3=%1

sockets! These sockets also allowed the possi&ilit o" designing a custom e)pansion

&oard!

WISENET is designed to measure light, temperature, and humidit !

There are man digital temperature sensors availa&le, &ut there is a much smaller

selection o" digital humidit and light sensors! A larger selection o" analog sensors areavaila&le/ however, analog sensors tended to re uire more power and &e less precise than

their digital counterparts, in addition to re uiring more comple) circuitr ! 3or these

reasons, digital sensors are given higher priorit ! Two new sensors provided the re uired


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"unctionalit ! 3irst, Sensirion released the S+T99, a digital temperature and humidit

sensor with ultra low power consumption 4DD? =icroA while measuring, 9 =icroA when

in sleep mode6, a 9F &it analog to digital converter, and the desired accurac 4 D

relative humidit , GUC6! It also "eatured a simple serial inter"ace! The light sensor chosen

was the Te)as Advanced (ptoelectonic Solutions 4TA(S6 TS. DD? am&ient light sensor

with S=Bus inter"ace! This sensor also "eatured ultra%low power 4 ?? =icroA active, 9?

=icroA power down6, a 9 %&it analog to digital converter, and dual photo diodes! The

TS. DD? uses &oth photo diodes to compensate "or in"rared light and to produce a

measurement that appro)imates the human e e response! The "inal stage o" hardware design involved creating the Add%on

module! The WISENET Add%(n =odule has the two digital sensors descri&ed a&ove!

The Sensirion S+T%99 humidit and temperature sensor has a %wire proprietar serial

inter"ace! The TA(S TS. DD? digital light sensor uses an S=Bus serial inter"ace!

S=Bus is a standardi'ed %wire serial inter"ace! The la out must &e care"ull designed

such that the light, temperature and humidit sensors does not underneath the evaluation

module when it is plugged into the &oard, which would make them useless!

So&tw%re 0e#i n'#$el& product#:

The server using "or WISENET should have "our commercial o"" the shel"

applications installed on it that worked together to create the 1ata Anal sis portion o" the

Server component! Apache, = S5., and 2+2 are open%source products "reel availa&le

on the Internet! In addition, Chart%1irector the trial version o" the commercial application

Chart%1irector was used!


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Ap%c$e is a standard we&%server, which makes a we& document availa&le on

the Internet!

*+* is a we& programming language, which allows d namic we&%pages! It

should also &e designed to use along with a data&ase and included man &uilt%in

"unctions "or inter"acing with = S5.!

M!S@L is a data&ase that can contain an t pe o" data and is accessed & a

TC2 I2 4Internet6 call!

C$%rt'0irector is a program that generates a graph "rom raw data! It is

availa&le in man languages such as 2+2, AS2, CQQ, and others!

So&tw%re Co ponent# Cu#to :

WISENET is also composed o" three custom so"tware components0

The Web program, WiseDB, and a port of TinyOS.

WISENET*s we& program was written in 2+2 and utili'ed the Chart%

1irector charting so"tware! The we& application ueried = S5. data&ase "or the data in

the re uested date range, then we use a Chart%1irector to generate a graph o" that data!

Wise1B is the custom so"tware component that inter"aced with the

Sensor =ote Network via a serial link to the gatewa mote and with the = S5. data&ase

via a TC2 I2 link to the = S5. server application! Alread we know a&out how

Wise1B interacted with the rest o" the s stem! Wise1B was written in CQQ and utili'ed

two open%source A2I*s 4application programming inter"ace6!

The "inal custom so"tware component involves porting Tin (S to the

CC9?9?%&ased hardware plat"orm descri&ed in the +ardware 1esign section! As

previousl mentioned, Tin (S is a real%time operating s stem designed "or use in sensor


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network applications where low%power, limited resources and hard real%time constraints

are critical parameters! A"ter implementing all the so"tware and em&edding in a single

s stem other important goal o" WISENET is to completel replace the lower%la er

"unctionalit to permit e)isting higher%level components and applications to &e

immediatel implemented on the new hardware plat"orm without modi"ication!

"uture Work:

There are a num&er o" "uture e)tensions "or this WISENET! A "ew are0

We can e)pand the sensor mote network & adding more motes! This

would allow the development and testing o" advanced network%la er "unctions, such as

multi%hop routing!

B creating a new 2CB design that integrates the CC9?9?E= design with

the sensors and power hardware on a single%&oard another interesting "eature can &e

developed or adopt a standard e)panda&le plug%in sensor inter"ace in &oth hardware and

so"tware

In researching alternative energ sources to e)tend mote &atter li"e!

2ossi&ilities include solar cells and rechargea&le &atteries !


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Conclu#ion#:

Wireless sensor networks are getting smaller and "aster, increasing their

potential applications in commercial, industrial, and residential environments!

WISENET, as implemented, represents one commercial application! +owever, the limit

o" applications depends onl upon the sensors used and the interpretation o" the data

o&tained! As the technolog improves and new low%power digital sensors &ecome more

readil availa&le, motes will increase "unctionalit without increasing power

consumption and will e)pand the wireless sensing market!

Re&erence#:

7!Atkin#on , M!S@LBB: A CBB A*I &or M!S@L3 /er# 7, , :,


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http://www.chipcon.com/files/"#_ $%_&ow_'ower_(ystems_)sin*_ he_

,,$ $ _$_$.pdf

D!=e3 +eide %nn3 et al! An Ener !'E&&icient MAC *rotocol &or Wirele## Sen#or

Network s,

http://www.isi.edu/ % weiye/pub/smac_infocom.pdf

or software shelf products downloads0 websites are:

www.apache.or*

www.php.net

www.mysql.comwww!advso"teng!com inde)!html

http0 Internetmaster!com installtutorial inde)!htm l
http://www.isi.edu/~weiye/pub/smac_infocom.pdfhttp://www.apache.org/http://www.php.net/http://www.mysql.com/http://www.advsofteng.com/index.htmlhttp://internetmaster.com/installtutorial/index.htmhttp://www.isi.edu/~weiye/pub/smac_infocom.pdfhttp://www.apache.org/http://www.php.net/http://www.mysql.com/http://www.advsofteng.com/index.htmlhttp://internetmaster.com/installtutorial/index.htm

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