Transcript
POOJ A LECTURER SAS IIT& RESEARCH MOHALI
WIRELESS SENSOR
AGENDA y
Introduction
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Wireless network standards
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Topologies
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Synchronization
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Applications
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Blue tooth Vs Wi-Fi
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Conclusion
Introduction A wireless network operates using some sort of sensors and line of site topology where the two adjacent sensors are able to detect and interpret the messages/packets that are sent or received by the communicating terminals. The system operates using electromagnetic waves or radio waves for taking the signals from one terminal terminal to to the other. other. Two or more computers are said said to be connected with each other when there is a possible communication with each other and called wireless when there is no wire or any physical medium used for the communication.
Wireless Network Standards Before
we begin our discussion, it is important to understand that a number nu mber of different wireless network standards are available. These standards were established by the IEEE (Institution of Electrical and Electronic Engineers) and are commonly called the 802.11 x standards. These are presented in the following table.
Different Diff erent Wireless Standards
Protocol
Release Date
Op. Frequency
Throughput (Type)
Legacy
1997
2.4 GHz
0.9 Mbit/s
2 Mbit/s
802.11 a
1999
5 GHz
23 Mbit/s
54 Mbit/s
802.11 b
1999
2.4 GHz
4.3 Mbit/s
802.11 g
2003
2.4 GHz
802.1 802.11 1n
Sept Sept 2008 2008 (est.)
802. 802.1 11 y
Marc March h 2008 (est.)
Data Rate (Max)
Modulation Technique
(Indoor) Depends, #
Radius Outdoor) Loss includes
~ 20 Meters
~100 Meters
OFDM
~35 Meters
~120 Meters
11 Mbit/s
DSSS
~38 Meters
~140 Meters
19 Mbit/s
54 Mbit/s
OFDM
~38 Meters
~140 Meters
Sept 2008 (est.)
74 Mbit/s
248 Mbit/s
MIMO
~70 Meters
~250 Meters
3.7 GHz
23 23 Mbit/s
54 Mbit/s
~50 Meters
~5000 Meters
This Table show the various protocols that are relevant to our studies and after the the stud study y of this this tabl tablee we can can easi easily ly see see the the dif differe ferenc nces es that that have have been been introduced from the time to time. y
OFDM: In OFDM, the sub-carrier frequencies are chosen so that the subcarriers are orthogonal to each other, meaning that cross-talk between the sub-channels is eliminated and inter-carrier guard bands are not required. This greatly simplifies the design of both the transmitter and the receiver; unlike unlike conve conventi ntiona onall FDM, FDM, a separa separate te filt filter er for each each sub-c sub-chan hannel nel is not required. The orthogonality also allows high spectral efficiency efficiency
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(DSSS) S) is a modul odulat atio ion n DSSS: Direct-Sequence Spread Spectrum (DSS techn techniqu ique. e. As with with other other spread spread spect spectrum rum techn technolo ologie gies, s, the transm transmit itte ted d signal takes up more bandwidth than the information signal that is being modulated.
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MIMO(pronounced mee-moh or mai-moh): Mult Multiipleple-in inpu putt and and multi ultipl pleeoutput refers to the use of multiple antennas both at the transmitter and receiver to improve the performance of radio communication systems.
Topologies There are mainly three topologies that are applied in the establishment of a typical wireless network. These are a re Static: It is the Traditional topology that uses the wires for as the communication medium. Mobile: It is that topology that uses the microwave for the sending and receipt of data i.e. communication.
this topo topolo logy gy,, we find find the the comb combin inat atio ion n of both both the the Hybrid: In this topologies. The wireless systems operate on the outside world and the internal communication takes place through the wires.
The The figur figuree sho shows the the func functi tion onin ing g of a hybri ybrid d topo topolo logy gy,, it is as foll follo ows.
This arrangement of the computers shows that there is a central hub connecting all the systems in a closed system and on the outer side there is a broadband modem that is connected with the outer world using usi ng wi wirel reless ess sensor sensor sy syste stem m.
The various configurations are as follows y
Thee Poin Th Pointt To Poin Pointt Topol opolog ogy y This is one of the most reliable topology because there is only one point of failure in this this topology and that is the host itself. itself. This topology is simple enough and requires less expertise but when it comes to operate multiple hosts the complexity increases in geometric fashion.
In this topology, each sensor node needs a separate connection over a wire gene genera rall lly y twis twiste ted d pair pair shie shield lded ed wire wire.. Due Due to the the use use of this this,, the the cost cost increases and the management become difficult. Also in this case all the information information is processed by the host.
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Multi drop In this topology, the bus topology was used as to reduce the number of wires. It is more reliable than the point to point topology. The main problem that is observed is that of digitization of data. In the point to point topology, digitization occurred in the host, where a single clock could be used to time stamp when the analog signals from multiple sensors were acquired.
multi multidr drop op netw network, ork, each each senso sensorr node node puts puts its infor informa mati tion on onto onto a common medium. The single-wire connection represents a potential single-point single-point failure failure.
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The Web Technology It is that topology in which all the hosts must be operating and connected all the time. It is possible only when the vendors agree on a common protocol so that all the hosts can communicate with each other to server to their near system. The The Figur iguree sho show a typi typica call web topo topolo logy gy .
The introduction of wireless sensor networks brought a revolution in the the field field of netw networ ork king ing as they they are are inte intell llig igeent enou nough that that they they automa automatica tically lly make make a configu configura rati tion on for for the relia reliable ble service service. These sens se nsor orss are are co-ope o-operratin ating g and and form form a temp tempor orary ary configu onfigura rati tion on to repla replace ce the the host host and and in the the futu future re,, they they ma may als also o beco become me se self lf awar awaree .
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Figu Figure re show showss a typi typica call conf config igur urat atio ion. n. An arch archit itec ectu ture re cons consis isti ting ng of a decoder for each channel and a direct-sequence spread-spectrum receiver can perform simultaneous sampling because the same baseband signal goes to each decoder. But the decoders represent a significant cost, power, and size limitation The web topology is the most complicated as all the hops can¶t reach at a destination. So a repeating configuration is required. Also in this case the nodes come and go at random and thus there is need to reconfigure all the systems frequently that affect the performance
Synchronization Time Synchronization in wireless networks is extremely important for basic communication, but it also provides the ability to detect movement, location, and proximity proximity.. The synchroniza s ynchronization tion problem consists of four parts: send time, access time, propagation time, and receive time. Three current synchronization synchronization protocol .
The first is relative timing and is the simplest. It relies on the ordering of messages and events. The next method is relative timing in which the network clocks are independent of each other and the nodes keep track of drift and offset. The last method is global synchronization where there is a constant global timescale throughout the network. This is obviously the most complex and the toughest to implement.
Applications Environmental monitoring Habitat monitoring Acoustic detection Seismic Detection Military surveillance Process Monitoring Structural health monitoring Health Monitoring While mainstream computers have an abundance of standards, the only official standard that has been adopted for wireless sensor networks is Wireless HART. In figure are some other standards being investigated for use by researchers in the field : ZigBee Wibree 6lowpan
Blue
tooth Vs Wi-Fi Bluetooth-equipped
hardware devices contain a Bluetooth chip that will wirelessly connect them to the PC without any interaction necessary from the user. Bluetooth devices operate in the 2.45 Gigahertz frequency range. range. Other Other devic devices es curre currentl ntly y operat operatee in this this frequ frequen ency cy range range as well well,, including cordless phones. Bluetooth devices avoid interfering with other systems is by sending out a very weak 1 mill watt signal ² a cell phone by comparison can transmit up to 3 watts.
In addition to data, up to three voice channels are available, and each device is assigned a unique 48-bit address. Connections can be point-to point or multipoint. multipoint. Bluetooth devices have a maximum transmission rate of only 1 Mbps ² up to 2 Mbps in the second generation of the technology ² of which about 20 percent of this capacity is used for data headers and handshaking information. information. By
comparison, Wi-Fi wireless LAN adapters are much more powerful and capable of reaching data transmission rates approaching 54Mbps. The most popular Wi-Fi Wi-Fi standard is the one used in your D-Link D -Link router, router, 802.11b. This version provides users with 11 Mbps transmission speeds and also operates in the 2.4 GHz band. Products based on this specification have very good range and can commonly transmit data at distances of well over 100 feet. The most recently introduced specification, specification, 802.11g, offers users the best of both both world worldss by provi providin ding g users users with with highe higherr trans transmi missi ssion on rates rates yet yet 100 percent compatibility with existing 802.11b products.
Conclusion A wireless network is collection of objects in a system operate in harmony to achieve a common objective in a controlled fashion but still independent independent in their respective respective functioning functioning.. Thus a network network has more than one component, a common communication medium over which hich they they esta estab blish lish rela relati tion onsh ship ip,, perf erform orm thei theirr functi nctio ons at individual level and a well defined set of rules. The scope and objective of this paper is limited to the use of wireless networks that is with special reference to the computers and acquaint you with the current trends, technologies, management, problems using them. We provide ide proven experience in the design, development, test and implementation of wireless sensor networks in the the bioc bioche hemi mica cal, l, tele teleco comm mmun unic icat atio ions ns,, elec electr tro omech mechan anic ical al,, and and environmental industries.
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