challenge in wirless technology.pdf

7/29/2019 Challenge In Wirless Technology.pdf

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Challenges In Wireless Technology

Kumari PoonamVII Semester

Department Of Information science & Engineering

HKES Poojya Doddappa Appa College Of EngineeringAiwan-E-Shahi Road, Gulbarga

Email: [email protected]

Abstract:

Wireless technology has created arevolution in todays world.It offersmany features like mobility,

portability.

Wireless inspite of many uses,is notperfect.There are limitations, political,technical difficulties.That mayultimately prevent wireless fromreaching their full potential.Twoissues are incompatible standards &device limitations.

These and many other challenges are

discussed in the following section.

Introduction:

Let's assume that we want to build avery high-speed, ubiquitous wirelessdata network.

Most likely,no one wireless devicewill be able to meet every need.Thepotential of wireless can met but notwith a single product.

A device using one standard will notwork in area where the deployedtechology Is different eg: is theinability to use bluetooth & 802.11b inthe same device.These are theproblems when industry wide

standards do not exists.Hence wirelessis unable to provide ubiquitousaccess to data.Device limitations also

restrict the free flow of data .Thesmall lcd on a mobile telephone isinadequate for displaying more than afew lines of text.In addition ,mostmobile wireless devices cannot accessthe vast majority of www sites on theinternet.The browers use a speciallanguague,wireless markup language(WML) instead of HTML.

Wireless will succeed because it will

be integrated into a variety of devicesthat can meet a variety of needs. Thegrowth of wireless applications bringsexciting possibilities and significantchallenges in terms of security andmanagement of the data and networkaccess that will be wandering aroundin the big danger.Analysts saywireless LANs can be easily accessedby neighbors - friendly or not.According to analysts, information

technology managers can providerobust security by making surewireless users are authenticated,preferably with a user name andpassword as well as a token. They alsosay encryption should be used end-to-end in a connection.


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Security can even be made strongenough to allow purchases or moneytransfers over the Web, banks andretailers say. And need strongprotection. Encrypting connections

from end to end requires a developerto consider every device used toaccess a network, users and analystssay. In addition, the security standardsof each wireless network carrier mustbe understood. Many analysts say theyagree that WAP 1.1 presentsproblems, because a wirelesstransmission is vulnerable to a hack atthe WAP gateway server. Under thecurrent standard, the WAP gateway

server sits inside the premises of thewireless carrier.

The Top 12 Challenges inWireless:

1. Providing high level of security,since wireless technologies do notprovide reliable service, extensivesearch is needed to provide servicesmuch nearer to the performance of

wired services.

2. Integrate unlicensed wirelesssecurely and transparently intoexisting networking systems, such aswired enterprise Ethernets, the cellularsystem, and the public switchedtelephone network.

3. Develop algorithms for maximizingsystem throughput and capacity in

large meshed networks.

4. Provide a cheap, wired backbone toenable inexpensive connectivity to thewireless mesh.

5. Provide cheap, smart antennae andthe protocols that go with them.

Without directional antennae,interference problems becomeexponentially worse.

6. Create standard ad hoc routing and

MAC layers that work for largemeshed networks of mobile nodeswith high throughput and low delayover many hops.

7. Reduce power consumption of theentire system, especially user devices.

8. Coordinate individual radios so thatQuality of Service can be guaranteedin a mesh network.

9. Solve the hidden-terminal problem,which is really a question ofcoordinating a large number of radiosto reduce interference.

10. Provide the fast handoffs that willbe required for continuous mobileconnectivity, as cell sizes willcontinue to decrease.

11. Eliminate outdated systems that tieup spectrum (broadcast television andradio, any analog system, any systemthat is not spread spectrum).

12.Too Much Of Wireless demandschanges.

I will discuss each of these challengesin turn, point out likely approaches tosolve these problems, and discuss the

advances required to make theseapproaches viable.

1. Providing high Level Of security:

Reliability, secured and correct data isthe need of the hour. Also is biggestchallenge to the wireless world.


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Proper authentication, well designedpassword storage mechanisms,firewalls, hack proof access toimportant data, should be taken asprime objectives while designing any

wireless technology.

2. Integration of wireless data intoexisting systems:

The wireless meshed network mustintercommunicate with all the existinglegacy systems out there. Theinterconnections need to be efficientand economically practical. Themeshed network can't require the

legacy systems to be extensivelymodified. Several unexpectedproblems have come up. For example,TCP/IP was originally designed to runover lousy, highly variable delaynetworks and still deliver reasonableperformance. The biggest problem formost users of TCP/IP, however, turnedout to be that it was not efficient underthe load of multiple users. The designwas changed to make it efficient under

load now it doesn't work well overlousy networks with highly variabledelays. There are two avenues ofattack for these types of problems, andboth should be followed through inparallel:

Modify the existing protocolsto be more flexible.

Make the wireless meshnetwork look more like a wirednetwork with predictabledelays and minimal losses.

Several other systems integrationopportunities, ripe for solutions,present themselves. For example,voice over IP (VoIP) over WLAN andintegration of this feature

transparently into the existing cellularsystems is a problem within reach of asolution. Integration of WLANsystems into existing operators'service portfolios is also a difficult

problem that is spawning its ownindustry, whose designs are rapidlybecoming standardized .The wirelessdata industry has many challengesahead. Advances in other fields arebeginning to provide the necessaryfoundations for overcoming them inthe next few years. The problemspresented by unlicensed wireless dataare some of the most challenging inthe wireless world.

3. Maximizing system throughput ina meshed wireless network:

This is the key problem that must besolved to provide high-speedubiquitous wireless coverage in anefficient manner. It essentially takesall of the problems and puts them

together to produce the best and mostefficient system. This is an interestingproblem because the theoretical upperbounds have yet to be convincinglydetermined. Even to approach areasonable estimate, we must makemany simplifying assumptions. Myguess is that the theoretical limitsdefining this problem will bedetermined within the next few years,but that practical solutionsapproaching these limits are still adecade away.

3. Cheap wired backbone:

We would think that with the surplusof fiber supposedly installed in theworld, connecting a wireless meshed


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network of radios to the wiredbackbone would be no problem.Wrong. The apparent glut of fiber isreally a glut of bandwidth betweenspecific points and an absolute dearth

of high-speed connectivity everywhereelse. Meshed wireless networks canhelp solve this problem because theycan convey the signals to where thefiber exists. Because the fiber is hardlyanywhere (less than 1 percent ofcommercial buildings have fiber onpremises today and less than 5 percentof buildings have fiber that actuallypasses by their front doors), a cheap,wired backbone that is also relatively

ubiquitous would create a significantsavings.

A huge unmet need exists for high-speed wired connections, and wirelessnetworks will suffer because of it. Inreturn for the monopolies thetelephone companies have, it seems asmall price to pay to require them toprovide this service.

The phone companies cannot beentirely blamed, however.Competition has not brought about thedesired results. Cable companies havehuge amounts of bandwidth availableover their infrastructure but have beenable to provide only small data pipesfor their customers. Something iswrong with the incentives in thesystem. This is probably the mostdifficult problem on the entire list,because it requires changes in both thegovernment and the free market.

5. Smart antennae:

This is one of the key areas thatwireless engineers have yet to put intocommon use, especially in the area of

mesh network design, where it wouldbe extremely valuable this problembecomes extremely challenging whenthe radios in the mesh network aremoving. The research in this area has

been excellent, and the theoreticallimits of the technology in stationarysituations are well understood.Achieving a practical implementationthat comes anywhere near thetheoretical limit in a mobile ad hocenvironment, however, is largelyuncharted territory.

With increases in signal-processingpower, approaching the theoretical

limit at a reasonable cost should bepossible in the near future. Knowingthe theoretical limits may beintellectually satisfying but isinsufficient in a commercialenvironment unless you canimplement a design that producesthese results in a commercially viableconfiguration. This task isexponentially more difficult and, ofcourse, more satisfying and rewarding.

6. Designing mesh networkprotocols:

Designing efficient mesh networkingprotocols is critical. The industry stillhas a long way to go to standardize onanything approaching an efficientrouting protocol for mesh networks.The simplest way to approach meshnetworks today would be toimplement a meshed routing protocolon top of existing WLAN protocols.Progress has been made in thisdirection. Without some modificationsat the MAC or physical layer,however, this approach is doomed to


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system inefficiencies and possibletotal collapse in large networks,because of MAC layer problems

The MAC and routing layers must be

designed in conjunction with eachother to wring out the last bits ofefficiency. If it is not done carefully, adesign that works eminently well in aWLAN will collapse in a largemeshed network. To produce the idealsolution, the physical layer should alsobe designed from scratch. Individuallymaximizing the design of each layer isnot sufficient. An efficient designmust include maximized system

throughput. These challenges makethe design work a difficult, Pioneeringwork has been done but manyfundamental problems in this area arestill not understood.

7. Power consumption:

The need to reduce powerconsumption is one of the mostchallenging and interesting topics in

wireless engineering, which not onlytackles theoretical problems, but alsorequires complicated physicalsolutions before any real system canbe implemented. The designer isalways trying to push the entiresystem to its theoretical limits.Today's cell phone solutions havemade huge strides in conservingbattery power. This has been achievedwith a relatively fixed throughput. Thenext challenge is to keep this trendintact while increasing the throughputby several orders of magnitude.

One method of decreasing powerconsumption is to bring the radioscloser together or, in other words, tocreate a ubiquitous mesh network. To

bring radios closer together, they mustbecome exponentially cheaper, as thenumber required increases (at best) bythe square of the ratio of decrease intheir average separation. Thus, using

mesh architecture, you can decreasethe power consumption of a radiosystem simply by making the radioscheaper.

There is also a great push to increasethe power density of batteries or otherpower-storage devices for reasons ofportability. Wireless protocols andsystem design should always strive tominimize power consumption. It is

one of the key criteria when building asystem. In a wired system, thisrequirement is usually ignoredbecause it has little effect on theperformance of the system. For awireless mobile system, carefullymanaging this specification is crucialto making a usable system.

8. Coordinating QoS:

We promote the idea of providingQuality of Service by increasing theavailable bandwidth. That solutionworks well for wired connections,where you can easily increase theadditional bandwidth or add a link thatwon't interfere with the original one.For wireless, however, you want tomake the most efficient possible useof the airwaves because you can't justmagically add more links between tworadios to increase bandwidth. Theresearch that has already been doneusing asynchronous transfer mode(ATM) to determine how to provideQoS can now beapplied to the realproblem of making wireless linksmore efficient. The truly difficultproblem, which has only begun to be


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addressed, is how to provide QoS in ameshed network over multiple linksbetween multiple radios. Althoughsome preliminary work has been donein this area practical solutions have yet

to be produced. The additional level ofcomplexity makes this an interestingproblem to solve.

9. Hidden-terminal problem:

This problem is particularly difficultto overcome for a large group ofmeshed radios. It occurs because a

radio needs to receive a signal that isabove the noise level by a certainamount before it can decode itcorrectly. To maximize the capacity ofa mesh network, you never want apacket to fail. When a "hidden"terminal transmits a packet withoutcoordinating with other nearby radios,it can easily interfere with anotherconversation going on nearby. As theload on the network increases,

interference increases, and thecorresponding efficiency of thenetwork decreases, eventually drivingthe throughput of the network to zeroas everyone tries to transmit all thetime.

There are three potential ways to fixthis problem, and all of them aredifficult. Advances in processingpower will enable implementation inthe near future, however.

The first solution is tocoordinate all the radios'transmissions. The problemwith this is that radios caninterfere with each other butmay be incapable of talking to

each other; therefore, it may beimpossible for them to directlycoordinate with each other.The solution is to coordinatewith their distant neighbors

over the network. In cellularnetworks this is done byprogramming in differentfrequencies to be used by theradios in different positions.New algorithms need to beinvented to support mobilemesh networks. This increasesthe level of complexity,because the radios must knowwhere they physically reside

before they can perform thiscoordination. (Of course, thiscan be determined wirelesslyusing a system such as GPSone wireless technologyhelping another.)

Another way to address thehidden-terminal problem is tochange the carrier-to-noiseratio (CN) to a negative value.This simplifies one dimensionof the problem because the hopdistance (HD) can now belarger than 2*RI, and radioscan successfully talk to eachother from farther away thanthey can interfere with oneanother. This simplifiescoordination, but does notentirely solve the problem.Although difficult toimplement with spreadspectrum radios and advancedsignal processing, thisreduction in CN is possible.Nothing is free, however.When CN is negative, the nextlayer of the onion is the so-called "near-far" problem. Todecode a signal with a negative


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CN, all signals must arrive atthe receiver withapproximately the same powerlevel so that N, the noisegenerated by the other radio

signals, does not become toolarge. One large nearby signalcan drown out all the smallsignals from distant radios.Some form of coordinationstill must be implemented. Thebest way to perform thiscoordination has yet to bedetermined.

The final proposed solutiontakes into account the fact that

N is not really noise; it is thesum of the signals of all otherradios. Advanced signal-processing algorithms can takeadvantage of this andeffectively mask the competingsignals, thereby greatlyreducing N and effectivelyincreasing CN to reduce thechance of interference. This isnot as easy as it sounds .Thereceived signals must beprocessed once for eachinterfering signal, as onecannot tell a priori whichsignal is destined for thereceiver. With exponentialimprovements in signal-processing power, this problemcan be solved in the comingyears. It can be furthersimplified by supporting smartantennae at each radio.

10.Fast handoffs:

One of the greatest system designconcepts in the evolution of wirelesstechnology is the notion of cellulardeployment and the huge reuse of

spectrum it provides. Reusingspectrum every few miles or everyfew hundred feet provides anessentially unlimited capacity forwireless communications. The smaller

the cell size, the larger thecommunication capacity per unit area.This imposes huge pressure for veryhigh-speed, short-distance radios.Thus, as cell size naturally shrinks, theavailable data rate increases.

This is exemplified by the largedeployment of WLAN in homes andenterprises. This large market willdrive down the cost of deploying

cellular-type systems. Today themarket is rapidly approaching thepoint where it is less expensive to puta WLAN node on every streetlightthan to deploy a conventional cellularsystem to cover the same area(especially when taking into accountwireless backhaul).

So why isn't this done today? Themain limiting factor is the ability to

provide fast handoffs over cells sizeda few hundred feet in diameter.Typical vehicle speeds of a hundredfeet per second mean switching cellsevery few seconds. This seemsimpossible to contemplate today, butthink about the hundreds of millionsof decisions a 2-GHz processor canmake in a fraction of a second. Theability to find the radio in the next celland to hand off to it in this same shortperiod of time seems eminentlyfeasible. Standards bodies today aredefining the interfaces required tomake this possible


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11. Eliminating inefficient usage ofspectrum:

This is one of the most difficultproblems to solve, because

constituencies that have monopolieson using the spectrum benefit greatlyfrom them and will not easily givethem up. This problem has only twosolutions, and both must be appliedwith care. The first is slowly andsteadily to force technologies tochange by providing a combination ofthe right incentives and the rightthreats. Many countries have takenthis approach, attempting to redefine

the type of usage allocated to manyareas of spectrum.

This reallocation of spectrum is slow,with the "chipping away" of theinefficient usage of spectrumproceeding at a rate estimated to beless than one-fifth of 1 percent peryear. At this rate, it will take morethan three centuries to free up half ofthe spectrum suitable for ubiquitous-

coverage mesh networks. Fortunately,this process is beginning to accelerateas a result of the hard work of manydedicated people. In the long run,these efforts will have a huge effect oncommunication capacity forindividuals.

The second solution is a technical one,exemplified today by new standardsdefined for new types of spreadspectrum radios, particularly the newrules covering ultra-wideband (UWB)radios these radios spread their signalsover many gigahertz of spectrum, atsuch a low power level and duty ratethat other users of this spectrum areunaware they are transmitting. Othermodulation techniques allowing

multiple uses of the same spectrum(with manageable interference) are invarious stages of development.

12. Too Much Of Wireless.

If in a room their exists too manythings that work on wireless principlesthen it leads to collision of frequencyon which the devices work. For e.g.:Mobile phones, wireless keyboard,wireless mouse, T.V, D.V.D, wirelesslandline operate on similar frequency.

Hence we need to fix the frequencyranges on which wireless devices

work or else they may not workcorrectly.

Conclusion:

In this short article we discussedvarious challenges that await theupcoming wireless technologies.

Each problem has a possible solutionand only needs to be tested andpractically implemented.

Once these problems get solved then itwill be world that will be connectedwirelessly.

References:

Michel. W. Ritter

Currently working on Mobility OfNetwork.

William Stalling

Author Of best-selling wirelesscommunications and networks.

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