cs9251 mobile computing university questions with answers

7/26/2019 Cs9251 Mobile Computing University Questions With Answers

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CS9251 MOBILE COMPUTING UNIVERSITY QUESTIONS WITH

ANSWERS (ALL UNITS) M.E (CSE)

UNIT I

PART-A

1. What are the two kinds of mobility?User Mobility :- refers to a user who has access to the same or similar telecommunicationservices at different places, i.e the user is mobile and the service will follow him or her.Device Portability:- refers to the movement of communication devices e.g. Mobile phones.

. What are the !hara!teristi!s of !omm"ni!ation de#i!es?Fied and wired.Mobile and wired.Fied and wireless.Mobile and !ireless.

$. What are the !ate%ories of wireless de#i!e?"ensor.#mbedded $ontrollers.Pager.Mobile Phones.Personal Digital assistant.Poc%et computer.&oteboo%'laptop.

&. 'efine (i%nal. "ignals are the physical representation of data. "ignals are functions of time andlocation. Users of a communication system can only echange data through the transmission ofsignals.

). What are the *roblems of wireless si%nals?Path loss of radio signalsPropagation effect on signalsMultipath propagation

+. What is meant by line-of-si%ht? ( straight line eists between a sender and a receiver it is called line-of-sight.

,. 'ifferentiate *eriodi! si%nal and a*eriodi! si%nal? )n a signal if a particular signal pattern repeats over a time period systematically it is aperiodic signal. )n a signal if the same signal pattern does not repeat itself over a time period it is%nown as *(periodic+ signal.

. i#e an e/am*le for a *eriodi! and a*eriodi! si%nals.a. periodic signal - t / 0 t/. where - 1 2 t 2 1b. (periodic signal - t / 3 t/.

0. What is delay s*read? (t the receiver, due to the different paths with different length the signals reach thedestination at different times. his is called delay spread.

1.

(tate Ad#anta%e of !ell"lar system.4igher $apacity.5ess transmission power.5ocal interface only.6obustness.

11. Tab"late two differen!es between analo% and di%ital si%nals.Analo% si%nal 7. )t is a continuously varying signal 8. Media used for signal propagation is li%e a. "pace propagation
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b. $opper wire media.'i%ital si%nal 7.)t is a regular se9uence of voltage pulses. 8.Media used for propagation is li%e a. $opper wire medium

1. 'efine atten"ation.

(ttenuation is a reduction in signal strength mainly at higher fre9uency ranges, and atreceiving end this attenuated signal has reduced voltage levels.

1$. i#e the e2"ation for si%nal to noise ratio. "ignal to noise ration "&6/ 0 7 log7 &oisepower' "ignalpower )t is epressed indecibel units.

1&. What is the normal o*eratin% ran%e of fre2"en!y for !ell *hones and mi!rowa#etransmission? he operating fre9uency range for cell phones is ;8< M4= to ;>< M4= appro/.he fre9uency of microwave transmissions is 8 ?4= to > ?4=.

1). 'efine a !ell. What are the sha*es related to a !ell? he smallest geographical area covered by wireless communication is said to be a cell.he shapes related to a cell are: a. $ircle

b. "9uarec. 4eagon

1+. 'efine wa#elen%th. he wavelength of a signal represents its distance or range it ta%es for one cycle. )t isdenoted as *@+. !avelength @ 0 c'f.

1,. What is a bandwidth? Aandwidth is the range of fre9uencies and represented as A! 0 f8 B f7, where f7 B f8are the first and last fre9uencies of the signal graph.

1. 'ifferentiate between si%nal and data. he term *data+ represents message or information where the signal is the representationof the data, and it is also termed as information bearing signal.

10. What is the *rin!i*le "sed in m"lti*le/ers? he principle used in multipleer is *many to one+ concept. Many inputs are combined as

one lin% or one output from a MUC unit where a D#MUC unit at the receiver reproduces the samemany units at the end entity. Multipleing tells how many users can share the medium withminimum of no interference.

. What are the im*ortant m"lti*le/in% s!hemes in wireless !hannel?"pace Division Multipleingime Division MultipleingFre9uency Division Multipleing$ode Division Multipleing

1. What are the m"lti*le a!!ess s!hemes?a/ FDM(b/ DM(c/ $DM(d/ "DM(

. 'efine %"ard band. )t is unused dummy/ fre9uency inserted with actual spectrum to reduce adacent channelinterference to enhance accuracy.

$. What are the ty*es of s*read s*e!tr"m?a/ F4"" - Fre9uency 4opping "pread "pectrumb/ D""" B Direct "e9uence "pread "pectrum.

&. What are the basi! shift keyin% methods?i/ (mplitude shift %eying.ii/ Fre9uency shift %eying


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iii/ Phase shift %eying.

). (tate in#erse s2"are law.#ven if no matter eists between the sender and the receiver i.e, if there is a vacuum/,the signal still eperiences the free space loss. he received power Pr is proportional to 7'd8 withd being the distance between sender and receiver.

+. 3lassify the radio wa#es based on the fre2"en!y "sed.

i/ ?round wave uses 28M4=ii/ "%y wave uses 8-E M4=iii/ 5ine of sight uses E M4=

,. (tate the different ty*es of additional *ro*a%ation effe!ts of a si%nal.i/ Aloc%ing or/ shadowingii/ 6eflectioniii/ 6efractioniv/ "catteringv/ Diffraction

. Why is di%ital mod"lation not eno"%h for radio transmission?(ntenna height is based on the signal+s wavelength.FDM can+t be applied.Medium characteristics li%e path-loss, penetration of obstacles, reflection, scattering and diffraction

depend on the wavelength of the signal.0. What are the $ f"ndamental *ro*a%ation beha#iors de*endin% on their fre2"en!y?

?round wave"%y wave5ine of sight

$. What is m"lti*ath *ro*a%ation? (s there is the atmosphere between the sender and the receiver the radio waves do notfollow line of sight. he propagation effects leads to channel impairment called multipathpropagation.

$1. What is %"ard s*a!e? 4ow are %"ard s*a!es reali5ed between "sers in 3'6A? ?uard space is the space between the interference regions. ?uard spaces are needed toavoid fre9uency band overlapping is also called channel interference. ?uard spaces are reali=edby using codes with the necessary distance in code space.

$. What is the $ differen!e basi! s!hemes analo% mod"lation?(mplitude modulationFre9uency modulationPhase modulation

$$. What is the "se of *hase lo!k loo* 7P889? o receive the signal correctly, the receiver must synchroni=e in fre9uency and phase withthe transmitter.

$&. What is ho**in% se2"en!e? ransmitter and receiver stay on one of these channels FDM and DM. he pattern ofchannel usage is called the hopping se9uence.

$). What is dwell time? he time spend on a channel with a certain fre9uency is called the dwell time.

$+. What are the disad#anta%es of small !ell"lar systems?

he disadvantages of cellular systems are 7. )nfrastructure needed 8. 4andover needed E. Fre9uency planning

$, What are the ad#anta%es of !ell"lar systems? 7. 4igher capacity 8. 5ess ransmission power E. 5ocal interference >. 6obustness


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$ What is browsin% !hannel allo!ation and fi/ed !hannel allo!ation? $ells with more traffic are dynamically allotted more fre9uencies. his scheme is %nownas browsing channel allocation, while the first fied scheme is called channel allocation.

$0 What is di%ital sense m"lti*le a!!ess? he scheme which is used for the pac%et data transmission service cellular digitalpac%et data in the (MP" mobile phone system is also %nown as digital sense multiple access

D"M(/.& What is network and swit!hin% s"bsystem?

he heart of the ?"M is formed by the networ% and switching system &""/. &""consists of the following switches and database: o Mobile services switching center M"$/ o 4ome location registers 456/ o Gisitor location registers G56/

&1 What is !alled b"rst and normal b"rst? Data is transmitted in small portions called burs, normal burst are used for datatransmission inside a slot user and signaling data/.

& (*e!ify the ste*s *erform d"rin% the sear!h for a !ell after *ower on?

Primary synchroni=ation

"econdary synchroni=ation

)dentification of the scrambling code&$ :/*lain abo"t trans*arent mode?

he transparent mode transfer simply forwards M($ data without any furtherprocessing. he system then has on the F#$ which is always used in the radio layer.

&& 8ist o"t se#eral ser#i!es that mi%ht de*end on the a!t"al lo!ations !an be distin%"ished?

Follow on services

5ocation aware services

Privacy

)nformation services

"upport services

&) 'es!ribe lower se!"rity; sim*ler to atta!k? &ot only can portable devices be stolen more easily, but the radio interface is also

prone to the dangers of eavesdropping. !ireless access must always include encryption,authentication, and other security mechanisms that must be efficient and simple to use.

&+ What are the benefits of reser#ation s!hemes?

)ncreased no other station is allowed to transit during this slot

(voidance of congestion

!aiting time in clearly %nown

&, What limits the n"mber of sim"ltaneo"s "sers in a T'6


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) 8ist o"t some a**li!ations !an benefit from wireless networks and mobile3omm"ni!ations?

Gehicles

#mergencies

Ausiness

6eplacement of wired networ%s

)nfotainment and more 5ocation dependent services

Mobile and wireless devices

PART->

1. Discuss briefly the multipleing techni9ues.

. #plain about the signal propagation.

$. Discuss about the cellular system.

&. 5ist the difference between "DM( 'DM( 'FDM('$DM(

). !hat is spread spectrum with its types.

+. #plain about the DM(.

,. !hy $DM( is needed and eplain it with an eampleJ

. !hy do M($ scheme in wired networ% fail in wireless networ%s and how does the multipleaccess with collision avoidance M($(/ scheme wor%J

0. Define modulation and eplain the method for analog modulationtechni9ues in details.

1. Discuss briefly the code division multipleing techni9ues

11. Discuss briefly the advanced phase shift %eying.

1. a. #plain about cellular wireless networ%.b. #plain about wireless transmission.

1$. $onsider three users and Aar%er code of si bits each for the userstransmitting the signals, introduce noise and near ' far problem whiletransmitting and reconstruct the data in the receiving side providing

the proper counter measures for the complications.1&. a. able the fre9uency bands used for wireless applications with their

ranges, propagation models and applications.b. 6epresent diagrammatically the protocol machines for multiple access

with collision avoidance.

1). #plain the followinga/ M($b/ "DM(

1+. #plain the various applications of mobile computing.

UNIT IIPART A

7. 'efine (6. )n early ?"M was called as ?roupe "peciale Mobile was founded on 7K;8, lateral it wasrenamed as ?lobal "ystem for Mobile $ommunication ?"M/. he primary goal of ?"M is toprovide a mobile phone system that allows user to roam throughout #urope and P"& systems.

8. What are the reasons for delays in (6 for *a!ket data traffi!? he data traffics in asymmetric at the wireless channels which means the down lin%traffic volume is much higher than the one in the uplin%. he aggregated data traffic within onerouting area is usually different with the one in the other 6(, in which case will cause differenttraffic load on "?"& and $?"& nodes. he $?"& with high traffic load will cause more pac%et


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delay.

E. 8ist o"t the different !ate%ories of ser#i!es offered by (6.

Aearer "ervices.

ele "ervices.

"upplementary "ervices.

>. What is the fre2"en!y ran%e of "*link and downlink in (6 network?

he fre9uency range of uplin% in ?"M networ% is ;K-KL M4=. he fre9uency range of downlin% in ?"M networ% is KE


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Pac%et Data Optimi=ed PDO/.

7. What is meant by >earer (er#i!es? ?"M specifies different mechanisms for data transmission, the original ?"M allowing fordata rates of up to KL bits's for non-voice services. Aearer services permit transparent andnontransparent, synchronous or asynchronous data transmission.

8


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8L. What is meant by Non-Trans*arent bearer ser#i!es? &on-ransparent bearer services use protocols of layers two and three to implementerror correction and flow control. hese services use the transparent bearer services, adding aradio lin% protocol 65P/. his protocol comprises mechanisms of high-level data lin% control4D5$/.

8. 'efine Tele ser#i!es.

?"M mainly focuses on voice-oriented tele services. hese comprise encrypted voicetransmission, message services, and basic data communication with terminals as %nown fromthe P"& or )"D&.

8;. 'efine ("**lementary ser#i!es. ?"M providers can offer supplementary services. "imilar to )"D& networ%s, theseservices offer various enhancements for the standard telephone service, and may vary fromprovider to provider. ypical services are user identification, call redirection or forwarding ofongoing calls.

8K. :/*lain the (6 ("b-(ystems. ( ?"M system consists of three subsystems, the radio sub system 6""/, the networ%and switching subsystem &""/ and the operation subsystem O""/. ?enerally a ?"M customeronly notices a very small fraction of the whole networ% the mobile stations M"/ and someantenna masts of the base transceiver stations A"/.

E.

'efine Radio s"bsystem. he radio subsystem 6""/ comprises all radio specific entities, the mobile stations M"/and the base station subsystem A""/. )t has the connection between the 6"" and &"" via the( interface solid lines/ and the connection to the O"" via the O interface Dashed lines/.

E7. What is meant by >ase station s"bsystem 7>((9? ( ?"M networ% comprises many A""s, each controlled by a base station controllerA"$/. he bss performs all functions necessary to maintain radio connections to an M",coding'decoding of voice and rate adaptation to'from the wireless networ% part, besides a A"$,the A"" contains several A"s.

E8. 'efine >ase trans!ei#er station 7>T(9. ( A" comprises all radio e9uipment, antennas, signal processing, amplifiers necessaryfor radio transmission. ( A" an form a radio cell or, using sectori=ed antennas, several cells andis connected to M" via the Um interface and to the A"$ via the (bis interface.

EE.

'efine >ase station !ontroller 7>(39. he A"$ basically manages the A"s. )t reserves radio fre9uencies, handles thehandover from one A" to another within the A"", and performs paging of the M". he A"$also multiplees the radio channels onto the fied networ% connections at the ( interface.

E>. What is meant by 6obile station 76(9? he M" comprises all user e9uipment and software needed for communication with a?"M networ%. (n M" consists of user independent hard and software and of the subscriberidentity module ")M/, which stores all user specific data that is relevant to ?"M. M" can beidentified via the international mobile e9uipment identity )M#)/, a user can personali=e any M"using his or her ")M.

E


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E;. What are the ser#i!es offered by Tele ser#i!es.

#mergency number

"hort message service "M"/

#nhanced message service #M"/

Multimedia message service MM"/

?roup fa

EK. 'efine Proto!ols. he main interest lies in the Um interface, as the other interfaces occur between entitiesin a fied networ%. 5ayer 7, the physical layer, handles all radio-specific functions. his includesthe creation of bursts according to the five different formats, multipleing of bursts into a DM(frame, synchroni=ation with the A", detection of idle channels, and measurement of the channel9uality on the downlin%.

>. What are the n"mbers needed to lo!ate an 6( and to address the 6(? o Mobile station international )"D& number M")"D&/ o )nternational mobile subscriber identity )M")/ o emporary mobile subscriber identity M")/ o Mobile station roaming number M"6&/

>7. What are the two basi! reasons for a hando#er? he mobile station moves out of the range of a A" or a certain antenna of a A"

respectively. he received signal level decreases continuously until it falls below the minimalre9uirements for communication. he error rate may grow due to interference, the distance to theA" may be too high. he wire infrastructure may decide that the traffic in cell is too high andshift some M" to other cells with a lower load if possible/. 4andover may be due to loadbalancing.

>8. 'efine 4(3('. ( straightforward improvement of ?"M+s data transmission capabilities is high speedcircuit switched data 4"$"D/, which is available with some providers. )n this system, higherdata rates are achieved by bundling several $4s. (n M" re9uests one or more $4s from the?"M networ%, i.e., it allocates several DM( slots within a DM( frame.

>E. What is meant by PR(? he net step toward more fleible and powerful data transmission avoids the problems of4"$"D by being fully pac%et-oriented. he general pac%et radio service ?P6"/ provides pac%et

mode transfer for applications that ehibit traffic patterns such as fre9uent transmission of smallvolumes according to the re9uirement specification.

>>. 'efine ':3T. Fully digital cellular networ% is the digital enhanced cordless telecommunicationsD#$/ system specified by #"). D#$ is also a more powerful alternative to the digital system$8 which ismainly used in the U and has even been selected as one of the E? candidates in the )M-8family.

>L. 'efine Proto!ol Ar!hite!t"re.

he D#$ protocol reference architecture follows the O") reference model. he physicallayer, medium access control, and data lin% control for both the control plane $-plane/ and theuserplane U-plane/.

>. What are the three *hysi!al !hannels "sed for the data transmission?7/ Dedicated physical data channel DPD$4/8/ Dedicated physical control channel DP$$4/


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E/ Dedicated physical channel DP$4/

>;. What is meant by U6T(?UM" Universal Mobile elecommunications service/ is a third-generationE?/ broadband,pac%et-based transmission of tet, digiti=ed voice and multimedia at data rates up to 8 megabitsper second. UM" offers a set of services to mobile computer and phone users, no matter wherethey are located in the world.

>K. Why Intra-!ell hando#er *ro!ed"re is needed for !ell"lar system?!ithin a cell, narrow band interference could ma%e transmission at a certain fre9uencyimpossible. he A"$ will decide to change the carrier fre9uency.


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8. Discuss about Digital video broadcasting.

E. Discuss about Digital audio broadcasting.

>. #plain "atellite networ%s in detail.

. 4ow is Mobility Management done in ?"M J

UNIT IIIPART A

7. What is W8AN?!5(&s is to replace office cabling, to enable ether less access to the internet and, tointroduce a higher fleibility for ad-hoc communication in e.g., group meetings.

8. 8ist o"t the ad#anta%es of W8ANs.

a. Fleibilityb. Planningc. Designd. 6obustnesse. $ost

E. 8ist o"t disad#anta%e of W8ANs.a. Nuality of serviceb. Proprietary solutionsc. 6estrictionsd. "afety and security

>. 8ist o"t W8ANs to ens"re their !ommer!ial s"!!ess.a. ?lobal operationb. 5ow power

c. 5icense free operationd. 6obust transmission technologye. "implified spontaneous cooperationf. #asy to useg. Protection of investmenth. "afety and security


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L. 'efine intra red.)nfra red technology uses diffuse light reflected at walls, furniture, etc. or directedlight if a line of sight 5O"/ eists between sender and receiver. "enders can be simple lightemitting diodes 5#Ds/ or laser diodes. Photodiodes act as receivers. Details about infra redtechnology, such as modulation, channel impairments etc.

. 8ist the ad#anta%es of infra red.

a. )nfra red technologies are its simple and etremely cheap senders and receiverswhich are integrated into nearly all mobile devices available today.b. PD(+s laptops, noteboo%s, mobile phones etc. 4ave an infra red data association)rD(/ interface. Gersion 7. of this industry standard implements data rates of upto 77< %bit's, while )rD(7.7 defines higher data rates of 7.7 Mbit's.c. &o licenses are needed for infra red technology and shielding is very simple.#lectrical devices do not interfere with infra red transmission.

;. 8ist the disad#anta%es of Infra red.a. )t has low bandwidth compared to other 5(& technologies. ypically )rD( devicesare internally connected to a serial port l imiting transfer rates to 77< %bit's.b. #ven > Mbit's is not a particularly high data rate. 4owever, their main disadvantageis that infra red is 9uite easily shielded. )nfra red transmission cannot penetrate

walls or is 9uite shielded.c. )nfra red transmission cannot penetrate walls or other obstacles. ypically, for goodtransmission 9uality and high data rates a 5O", i.e., direct connection, is needed.

K. 8ist the ad#anta%es of radio transmission.a. )t includes the long-term eperiences made with radio transmission for wide areanetwor%s and mobile cellular phones.b. 6adio transmission can cover larger areas and can penetrate walls, furniture, plants,etc.c. (dditional coverage is gained by reflection. 6adio typically does not need a 5O" ifthe fre9uencies are not too high. Furthermore, current radio based products offermuch higher transmission ta%es than infra red.

7. 8ist the disad#anta%es of radio transmission.

"hielding is not so simple, 6adio transmissin can interfere with other senders or

electrical devices can destroy can destroy data transmitted via radio.

6adio transmission is only permitted in certain fre9uency bands, very limited rangesof license free bands are available worldwide and those that are available are notthe same in all countries.

77. 'efine infrastr"!t"re.)nfrastructure networ%s not only provide access to other networ%s, but also includeforwarding functions, medium access control etc. )n these infrastructure based wirelessnetwor%s, communication typically ta%es place only between the wireless nodes and theaccess point, but not directly between the wireless nodes.

78. 'es!ribe ad-ho! networks.(d-hoc wireless networ%s, however, do not need any infrastructure to wor%. #achnode can communicate directly with other nodes, so no access point controlling mediumaccess is necessary.

7E. 'efine I::: .11.

his means that the standard specifies the physical and medium access layeradapted to the special re9uirements or wireless 5(&s, but offers the same interface as theothers to higher layers o maintain interoperability.

7>. :/*lain (ystem Ar!hite!t"re.!ireless networ%s can ehibit two different basic system architectures ofinfrastructure or ad-hoc. )t shows the components of an infrastructure and a wireless partas specified for )### ;8.77. "everal nodes, called stations "(i/, are connected to accesspoints (P/. "tations are terminals with access mechanisms to the wireless medium andradio contact to the (P.


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7l"etooth.

he history of Aluetooth starts in the tenth century, when 4arald ?ormsen, ing ofDenmar%, erected a rune stone in Relling, Denmar%, in memory of his parents. he stone hasthree sides with elaborate carvings. One side shows a picture of $hris, as 4arald did notonly unite &orway and Denmar%, but also brought $hristianity to "candinavia. 4arald has

the common epithet of *Alatand+, meaning that he had a rather dar% compleion.

8


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8L. What are the ad#anta%es of W8AN(?

Fleibility

Planning

Design

6obustness

$ost

8. 6ention some of the disad#anta%es of W8AN(.

Nuality of service

Proprietary solutions.

6estrictions

"afety and "ecurity

8;. 6ention the desi%n %oals of W8AN(.

?lobal operation

5ow power

5icense-free operation

6obust transmission technology

"implified spontaneous cooperation

#asy to use

Protection of investment

"afety and security

ransparency for applications.

8K. What is the differen!e between infrastr"!t"re and ad-ho! networks?Infrastr"!t"re-based wireless networks$ommunication ta%es place only between the wireless nodes and the accesspoint, but not directly between the wireless nodes.Ad-ho! wireless networks$ommunication ta%es place directly with other nodes, so no access pointcontrolling medium access is necessary.

E. i#e the *rimary %oal of I:::.11.he primary goal of the standard was the specification of a simple and robust !5(&

which offers time-bounded and asynchronous services.E7. 6ention the feat"res of infrared transmission.

"imple

#tremely cheap

licenses are not needed

#lectrical devices do not interfere

E8. What are the disad#anta%es of infrared transmission?

5ow bandwidth

$annot penetrate walls or other obstacles.

EE. 6ention the feat"res of radio transmission.

$over large areas.

$an penetrate walls, furnitures.

Does not need a 5O".4igher transmission rates.

E>. What are the disad#anta%es of radio transmission?

"hielding is not so simple.

$an interfere with other senders.

5imited ranges of license-free bands.

E


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EL. 'efine random ba!k off time.)f the medium is busy, nodes have to wait for the duration of D)F", entering acontention phase afterwards. #ach node now chooses a random bac% off time within acontention window and delays medium access for this random amount of time.

E. What is Traffi! Indi!ation 6a*?he )M contains a list of stations for which unicast data frames are buffered in the

access point.E;. What is 'eli#ery Traffi! Indi!ation 6a*?

he access point maintains a D)M interval for sending broadcast'multicast frames.he D)M interval is always a multiple of the )M interval.

EK. What is Ad-ho! TI6?(ll stations announce a list of buffered frames during a period when they are awa%e.destinations are announced using ()Ms.

>. What is meant by roamin%?)f a user wal%s around with a wireless station, the station has to move from oneaccess point to another to provide uninterrupted service. Moving between access points iscalled roaming.

>7. 6ention the feat"res of 4IP:R8AN1.

(bility to forward data pac%ets using several relays.

#tend communication beyond radio range.>8. What are the three *hases of medi"m a!!ess in :B-NP6A?

Prioriti=ation.

$ontention

ransmission

>E. 6ention the elements of >l"etooth !ore *roto!ols.

6adio

Aase band

5in% manager protocol

5ogical lin% control and adaptation protocol

"ervice discovery protocol

>>. What is the *"r*ose of sniff state?

he sniff state has the highest power consumption. he device listens to the piconetat a reduced rate.

>L. What is the *"r*ose of *ark state?)n this state the device has the lowest duty cycle and the lowest powerconsumption. he device releases its (M( and receives a par%ed member address. hedevice is still a member of the piconet, but gives room for another device to become active.

>. (tate the modes *ossible when the sla#e is in !onne!tion state in >l"etooth.

(ctive

"niff

4old

Par%

>;. What are elements a#ailable "nder link se!"rity of >l"etooth te!hnolo%y?7/ (uthentication 8/ ey management E/ #ncryption

>K. What is a 86P?)t is Hlin% manager specificationI that is responsible for radio lin% between the masterand slave in Aluetooth. his protocol also involves message echanges in the form of5MPPDU+s.


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b/ $hange lin% %eyc/ #ncryption

PART->

7. #plain in detail the system architecture of )### ;8.77 7L/

8. !ith a focus on security, what are the problems of !5(&J

E. !hat are the advantages and problems of forwarding mechanism in Aluetooth networ%sregarding power saving and networ% stabilityJ

>. #plain the M($ layer in )###;8.77 7L/


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re9uirements of mobile )P was to support hiding the mobility of the M&. $& does not need to%now anything about the M&+s current location and sends the pac%et as usual to the )P addressof M&.

>. What is meant by a%ent dis!o#ery?One initial problem of an M& after moving is how to find a foreign agent. 4ow does theM& discover that it has movedJ For this purpose mobile )P describes two methods:

(gent advertisement(gent solicitation

, )P version L ma%es life much easier. "everal mechanisms thathad to be specified separately for mobility support come free in )PvL. One issue is security withregard to authentication, which is now a re9uired feature for all )PvL nodes. #very )PvL nodecan send binding updates to another node so the M& can send its current $O( directly to the $&

and 4(.. 8ist o"t mi!ro mobility *roblems *resents a !om*arison of the three a**roa!hes.

a. $ellular )Pb. 4awalic. 4ierarchical mobile )PvL 4M)PvL/

;. :/*lain '43P.he dynamic host configuration protocol is mainly used to simplify the installation andMaintenance of networ%ed computers. )f a new computer is connected to a networ%, D4$O canprovide it with all the necessary information for full system integration into the networ%, e.g.,addresses of a D&" server and the default router, the subnet mas%, the domain name and )P(ddress.

K. What is meant by mobile ad-ho! network?here may be several situations where users of a networ% cannot rely on an

)nfrastructure. he ad-hoc setting up of a connection with an infrastructure is not the main issue4ere. hese networ%s should be mobile and use wireless communications.

7. 'efine ro"tin%.6outing is needed to find a path between source and destination and to forward thePac%ets appropriately. )n wireless networ%s using an infrastructure, cells have been defined.!ithin a cell, the base station can reach all mobile nodes without routing via a broadcast.

77. 8ist o"t some f"ndamental differen!es between wired networks and Ad-ho! WirelessNetworks related to ro"tin%.a. (symmetric lin%sb. 6edundant lin%sc. )nterference andd. Dynamic topology

78. 'efine '('C.

Destination se9uence distance vector D"DG/ routing is an enhancement to distancevector routing for ad-hoc networ%s. Distance vector routing is used as routing informationprotocol 6)P/ in wired networ%s. )t performs etremely poorly with certain networ% changesdue to the count to infinity problem.

7E. What are the re2"irements of mobile IP?

$ompatibility

ransparency

"calability and efficiency

"ecurity


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7>. 6ention the different entities in a mobile IP.

Mobile &ode

$orrespondent &ode

4ome &etwor%

Foreign &etwor%

Foreign (gent

4ome (gent

$are-Of address

Foreign agent $O (

$o-located $O(

7indin% "*date?his message sent by the 4( to $&s reveals the current location of the M&.he messagecontains the fied )P address of the M& and the $O(.he binding update can re9uest anac%nowledgement.

8. :/*lain bindin% a!knowled%ement.)f re9uested, a node returns this ac%nowledgement receiving a binding update message.

8;. 'efine bindin% warnin%.


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)f a node decapsulates a pac%et for a M&, but it is not the current F( for this M&, thisnode sends a binding warning. he warning contains M&+s home address and a target nodeaddress.

8K. :/*lain !ell"lar IP.$ellular )P provides local handovers without renewed registration by installing a singlecellular )P gateway for each domain, which acts to the outside world as a foreign agent.

E. What are the ad#anta%es of !ell"lar IP?Manageability

#fficiency

ransparency and "ecurity

E7. What is known as mobility an!hor *oint?4M)PvL provides micro-mobility support by installing a mobility anchor point, which isresponsible for a certain domain and acts as a local 4( within this domain for visiting M&s.

E8. :/*lain destination se2"en!e distan!e #e!tor ro"tin%.Destination se9uence distance vector routing is an enhancement to distance vector routingfor ad-hoc networ%s and is used as routing information protocol in wired networ%s.

EE. What are the two thin%s added to the distan!e #e!tor al%orithm?

"e9uence &umbers

Damping

E>. 4ow the dynami! so"r!e ro"tin% does di#ide the task of ro"tin% into two se*arate*roblems?

6oute discovery

6oute Maintenance

E. What are the messa%es "sed for mobile IP o*timi5ation?

Ainding re9uest

Aiding update

Ainding ac%nowledgement

Ainding warning

>7. (tate the reasons for re#erse t"nnelin%.

Firewalls

Multi-cast


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5

>8. (tate any & feat"res of IP#+.a. &o special mechanisms as add-ons are needed for securing mobile )P registration.b. #very )PvL node masters address auto configuration B the mechanisms for ac9uiring a $O(are already built in.c. &eighbor discovery as a mechanism mandatory for every node is also included in the

specificationT special foreign agents are no longer needed to advertise services.d. $ombining the features of auto configuration and neighbor discovery means that everymobile node is able to crate or obtain a topologically correct address for the current point ofattachment.e. #very )PvL node can send binding updates to another node, so the M& can send its current$O( directly to the $& and 4(.

>E. (tate the ad#anta%es of !ell"lar IP.Manageability: $ellular )P is mostly self-configuring, and integration of the $)P?! into a firewall

would facilitate administration of mobility-related functionality.

>>. (tate the disad#anta%es of !ell"lar IP.

#fficiency : (dditional networ% load is induced by forwarding pac%ets on multiple paths.

ransparency: $hanges to M&s are re9uired.

"ecurity : 6outing tables are changed based on messages sent by mobile nodes. (dditionally,

all systems in the networ% can easily obtain a copy of all pac%ets destined fro an M& by sendingpac%ets with the M&+s source address to the $)P?!.

>;. (tate the disad#anta%es of 46IP#+.ransparency : (dditional infrastructure component M(P/.

"ecurity : 6outing tables are changed based on messages sent by mobile nodes. his re9uires

strong authentication and protection against denial of service attac%s. (dditional securityfunctions might be necessary in M(Ps.

>K. (tate the "ses of mobile ad ho! networks.

)nstant infrastructure

Disaster relief

6emote areas

#ffectiveness

PART >7. !hat are the re9uirements of a mobile )PJ

8. Describe Dynamic host configuration protocol.

E. Discuss the routing algorithm in ad-hoc networ%.

>. !hat are the entities in mobile )PJ


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;. Discuss and detail the differences in topology reorgani=ation in D"DG and D"6 routing protocols.

K. !hat are the general problems of mobile )P regarding security and support of 9uality of serviceJ

7. &ame the inefficiencies of mobile )P regarding data forwarding from a correspondent node to amobile node. !hat are optimi=ations and what additional problems do they causeJ

77. !hat are the types of registration in mobile )PJ #plain.

78. #plain the different routing techni9ues available for mobile ad hoc networ%

with an eample.7E. #plain the agent discovery process in mobile )P.

7>. #plain the different approaches available for )PvL to support mobility.

7. What is the %oal of 6-T3P?he goal of M-$P is to prevent the sender window from shrin%ing if bit errors ordisconnection but not congestion cause current problems. )t wants o provide overall throughput o lower the delay

o maintain end-to-end semantics of $P o provide a more efficient handover.


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#fficient

6eliable

"ecure

K. Name the layers of WAP.

ransport layer

"ecurity layer

ransaction layer

"ession layer

(pplication layer

7. Name some I36P messa%es.

Destination unreachable

Parameter problem

Message too big

6eassembly failure

#cho re9uest'reply

77. What is WTP? What are its !lasses?!P stands for !ireless ransaction Protocol. )t has been designed to run on very thinclients such as mobile phones. )t has three classes.

$lass : provides unreliable message transfer without any result message.

$lass 7: provides reliable message transfer without eactly one reliable result

message.

$lass 8: provides reliable message transfer with eactly one reliable result message.

78. What is W(P?he !ireless "ession Protocol has been designed to operate on top of the datagramservice !DP or the transaction service !P. )t provides a shared state between a client and aserver to optimi=e content transfer.

7E. Name some feat"res of W(P ada*ted to web browsin%.

4P'7.7 functionality

#change of session headers

Push and pull data transfer

(synchronous re9uest7>. What is W68?

he !ireless Mar%up 5anguage is based on the standard 4M5 %nown from the www andon 4DM5. !M5 is specified as an CM5 document type.

7


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!M5 Arowser

Dialogs

7;. What are the !lasses of libraries?

$ommon networ% services

&etwor% specific services

Public services

7K. Name the o*erations *erformed by PAP.Push access Protocol performs the following operations: Push submission 6esult notification Push cancellation"tatus 9uery $lient capabilities 9uery

8. What are the !om*onents of WAP.?he protocol framewor% of !(P8. consists of four components: Aearer networ%s ransport services ransfer services "ession services

87. (tate any & im*ro#ements to the !lassi!al T3P.7. )ndirect $P 8. Mobile $PE. "nooping $P >. Fast retransmit ' Fast recovery.

88. (tate any ad#anta%es of I-T3P.

)-$P does not re9uire any changes in the $P protocol as used by the hosts in the fied

networ% or other hosts in a wireless networ% that do not use this optimi=ation.

Due to the strict partitioning into two connections, transmission errors on the wireless lin%,

i.e., lost pac%ets cannot propagate into the fied networ%.

8E. (tate any disad#anta%es of I-T3P.

he loss of the end-to-end semantics of $P might cause problems if the foreign agent

partitioning the $P connection crashes.

)n practical use, increased handover latency may be much more problematic.

8>. (tate any ad#anta%es of (-T3P.he end-to-end $P semantic is preserved. &o matter at what time the foreign agent

crashes if this is the location of the buffering and snooping mechanisms/, neither thecorrespondent host nor the mobile host have an inconsistent view of the $P connection asis possible with )-$P.

he correspondent host does not need to be changedT most of the enhancements are in the

foreign agent.

8


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8;. (tate any ad#anta%es of Transmission < time o"t free5in%.

he advantage of this approach is its simplicity. Only minor changes in the mobile host+s

software already result in a performance increase. &o foreign agent or correspondent host hasto be changed.

he main disadvantage of this scheme is the insufficient isolation of pac%et losses.

8K. (tate any ad#anta%es of Transmission < time o"t free5in%.

o he advantage of this approach is that it offers a way to resume $P connections evenafter longer interruptions of the connection.o )t is independent of any other $P mechanism, such as ac%nowledgements or se9uencenumbers, so it can be used together with encrypted data.

E. (tate any disad#anta%es of Transmission < time o"t free5in%.

&ot only does the software on the mobile host have to be changed, to be more effective the

correspondent host cannot remain unchanged.

(ll mechanisms rely of the capability of the M($ layer to detect future interruptions.

Free=ing the state of $P does not help in case of some encryption schemes that usetimedependentrandom numbers. hese schemes need resynchroni=ation after interruption.

E7. (tate any ad#anta%es of sele!ti#e retransmission.

he advantage of this approach is obvious: a sender retransmits only the lost pac%ets. his

lowers bandwidth re9uirements and is etremely helpful in slow wireless lin%s.he gain in efficiency is not restricted to wireless lin%s and mobile environments. Using

selective retransmission is also beneficial in all other networ%s.

E8. (tate any disad#anta%es of sele!ti#e retransmission.

More buffer is necessary to re-se9uence data and to wait for gaps to be filled.

Aut while memory si=es and $PU performance permanently increase, the bandwidth

of the air interface remains almost the same.

herefore, the higher compleity is no real disadvantage any longer as it was in the

early days of $P.

EE. (tate any ad#anta%es of Transa!tion oriented T3P.he obvious advantage for certain applications is the reduction in the overhead whichstandard $P has for connection setup and connection release.

E>. (tate any disad#anta%es of Transa!tion oriented T3P.his solution no longer hides mobility. Furthermore, '$P ehibits several security problems.

E. "ession layer


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EK. What are the ser#i!e *rimiti#es a#ailable in T-(AP?7. VD Unit data.re9D(, DP, "(, "P, UD/8. VD Unit data.ind"(, "P, UD/E. VD#rror.ind#$/D( B destination address "( B "ource (ddressDP B destination port "P B "ource Port

UD B user data #$ B #rror code.>. What are the different se!"rity le#els offered by WT8(?7. Privacy 8. data integrity E. authentication

>7. What are the different ser#i!es offered by WTP?7. $lass B unreliable message transfer without any result message.8. $lass 7 B reliable message transfer without any result message.E. $lass 8 B reliable message transfer with eactly one result message.

>8. 4ow is reliability a!hie#ed in WTP?7. duplicate removed8. retransmissionE. ac%nowledgements>. uni9ue transaction identifier.

>E. What are the ty*es of P'U e/!han%ed between WTP entities?

7. invo%e PDU.8. ac% PDUE. result PDU.

>>. What are the f"n!tions of W(P?7. session management8. $apability negotiationE. content encoding

>. $ontet management.

>. 8ist any & !a*abilities of W68 s!ri*t.7. Galidity chec% of user input8. (ccess to device facilitiesE. 5ocal user interaction>. #tension to the device software

>;. What are the standard libraries a#ailable for W68 s!ri*t?7. 5ang.8. FloatE. "tring>. U65K. What are the libraries a#ailable for WTA?7. $ommon networ% services8. &etwor% specific servicesE. Public services.


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ransport service

ransfer service

"ession service.

PART >

7. #plain in detail about traditional $P in details. 7L/

8. #plain classical $P improvements and snooping $P

E. #plain the function of the components of the !(P architecture.

>. #plain the concept of wireless mar%up language.

cs9251 mobile computing university questions with answers

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