Wcdma Questions

7/25/2019 Wcdma Questions

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1. What is Significance of Eb/No? On what factors it is dependent? who providesEb/No? What is typical Eb/No for AM 1!.! for Node " and MS?

Answer - Eb_No is related to QOS of a service which in terms related to bit error rate.Technically it is the minimum signal to noise needed by infrastructure eui!ment after

des!reading it signal. This is a value used to com!are different infrastructurevendors. Eb_No changes with the service ty!e. Ty!ically Eb_No for A"# $%.% is & 'db for node ( and ) d( for "S. *t is infrastructure vendor +NSN, !rovides the Eb_Nofor Node (.The EbN value is the value that needs to be reached for insuring the targetedservice uality. This is the ratio between the energy !er bit for the related serviceover the noise s!ectral efficiency over the whole s!reading band.The s!read signal is characteri/ed by the ratio of the energy !er chi! over thes!ectral noise density EcN.!. What effect is there on signal by spreading and dispreading?

Answer - S!reading will increase the bandwidth of a as signal. A signal of $ 0bswill become ' 0bs after s!reading and will become $ 0bs after des!reading.The !rocessing gain term e1!resses the gain achieved by s!reading a narrow bandsignal over a wideband s!ectrum.This gain is the ratio between the s!reading chi! rate and the actual service bit ratemeasured at the #23 level#. $efine %rocessing &ain.

Answer - 4rocessing 5ain is ratio between rate of s!readed signal and rate of nons!readed signal.456 $ log +3hi! rate (it rate,'. What is a chip rate of W($MA Syste)? *ow )+ch is the bandwidth re,+iredfor W($MA?

Answer7 - 8)' 0cs. 9:: ; "


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%F +'8d(m, Node(@ 34*3< is around %F +8;.$ & 88d(m,.*n urban areas where in-building coverage is taen care of by in-building installations@the 34*3< may sometimes go as low as ; because7$, The coverage area is small since users are close to the site@ and%, "ore !ower can be allocated to traffic channels.1'. *ow )+ch power +s+ally a Node" is allocated to control channels?

Answer - The !ower allocated to control channels may de!end on eui!ment vendorrecommendation. Ty!ically no more than % of the total Node( !ower is allocatedto control channels@ including 34*31!.! %S>0' %S>1! and %S>#'?Answer - Fith same assum!tions as above73S-$%.%7 $%.C +D2,@ C'.$ +:2,.4S-C'7 8'.) +D2,@ $%.)+:2,.4S-$%)7 $C.% +D2,@ ).' +:2,.4S-8)'7 $C.% +D2,@ %.) +:2,.4S-8)' has only $%) on the u!lin@ therefore the u!lin ca!acity is the same forboth.


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%$. $ifferent 8dle )ode tas7s =E perfor)sAnswer - *n *dle mode@ the DE has no connection to the radio networ0ee!ing DEs in *dle mode minimi/es the use of resources both for the DEs and in thenetwor.


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interfere with one another. :ue to the !ro!agation !ath loss@ the signal received bythe base station from a DE close to the base station will be stronger than the Signalreceived from another terminal located at the boundary. far effect. To achieve aconsiderable ca!acity@ all signals@ irres!ective of distance@ should arrive at the basestation with the same mean !ower. A solution to this !roblem is power control@which attem!ts to achieve the same mean received !ower for each user.##. Na)e three loops in %ower control 8n W($MA? E6plain the) briefly.

Answer? - O!en 2oo!*nner 2oo!Outer 2oo!Open :oop %ower controlThe o!en-loo! !ower control techniue reuires that the transmitting entity measuresthe channel interference and adusts its transmission !ower accordingly. This can bedone uicly@ but the !roblem is that the interference estimation is done on thereceived signal@ and the transmitted signal !robably uses a different freuency@ whichdiffers from the received freuency by the systemPs du!le1 offset. As u!lin anddownlin fast fading +on different freuency carriers, do not correlate@ this methodgives the right !ower values only on average.8nner :oop

*n this method the received signal-to interference ratio +S*#, is measured over a CC-microsecond !eriod +i.e.@ one time slot,@ and based on that value@ a decision is madeabout whether to increase or decrease the transmission !ower in the other end of theconnection. Note that the delay inherent in this closed-loo! method is com!ensatedfor by maing the measurements over a very short !eriod of time. The transmit powercontrol +T43, bits are sent in every time slot within the u!lin and the downlin. Thereis not a neutral signal? all !ower control signals contain either an increase ordecrease command.O+ter :oopThe outer loo! !ower control functions within the base station system@ and aduststhe reuired S*# value +S*#target,@ which is then used in the inner loo! control.:ifferent channel ty!es@ which can be characteri/ed by@ for e1am!le@ differentcoding and interleaving methods@ constitute a channelPs !arameters. :ifferent

channel !arameters may reuire different S*#target values. The final result of thetransmission !rocess can only be nown after the decoding !rocess@ and theresulting uality !arameter is then used to adust the reuired S*# value. *f the usedS*# value still gives a low uality bit stream@ then the outer loo! !ower control mustincrease the S*#target value. This change in the outer loo! will trigger the inner loo!!ower control to increase the mobile station transmission !ower accordingly#'. What is S8?

Answer - S*# is the Signal-to-*nterference #atio G the ratio of the energy in dedicated!hysical control channel bits to the !ower density of interference and noise afterdis!reading.#-. *ow )any ti)e 8nner :oop %ower (ontrol happens and what type of fading itco)pensates?

Answer - $;


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4#A3< . This !arameter is configurable and decides at which level below #TF4!reamble ram!ing will start.#. What power A(* )essage (ontrol %art is sent?

Answer - The !ower of the control !art of the #A3< message is determined by the!ower of the last transmitted !reamble and by a configurable offsetpowerOffset%p)#3. "riefly describe why open loop power control is needed and how it wor7s?

Answer - O!en 2oo! !ower control is used when no feedbac mechanism is!ossible. An estimate of the reuired !ower is made from measurements andsystem information.This is used for initial networ access and finding initial !ower settings duringdedicated mode.'5. E6plain the f+nctionality of ;%(?

Answer G :uring 4ower 3ontrol@ Transmit 4ower control+T43, commands are usedto !ower u! or !ower down based on S*# target in the ste! of .; d( + $ d( if theconnection is made over *ur,.'1. *ow )any types of handovers are there in =M;S?

Answer GSoftSofter


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to transmit higher !ower to overcome the higher noise level. This means smaller!ath loss can be tolerated and the cell radius is reduced. To summari/e@ a highernoise rise means higher ca!acity and smaller foot!rint@ a lower noise rise meanssmaller ca!acity and bigger foot!rint.'0. What is %ilot %oll+tion?

Answer - Sim!ly s!eaing@ when the number of strong cells e1ceeds the active setsi/e@ there is H!ilot !ollutionI in the area. Ty!ically the active set si/e is 8@ so if thereare more than 8 strong cells then there is !ilot !ollution.:efinition of Hstrong cellI7 !ilots within the handover window si/e from the strongestcell. Ty!ical handover window si/e is between ' to Cd(. 9or e1am!le@ if there aremore than % cells +besides the strongest cell, within 'd( of the strongest cell thenthere is !ilot !ollution.'2. *ow )any fingers does a =E ra7e receiver have?

Answer G ''. What is Bco)pressed )odeC?

Answer - 3om!ressed mode is a !hysical layer function that allows the DE totem!orarily tune to another freuency@ and measure the #9 environment of anotherD"TS freuency +e.g. *9li)ited or downlin7>li)ited syste)?Answer G *nitially@ A ty!ical F3:"A networ is D!lin 2imited. 2ater a 2oadedNetwor becomes :ownlin 2imites.--. What is O(NS?

Answer - Orthogonal 3arrier Noise Simulator-0. "riefly describe (apacity Manage)ent and its f+nctions?

Answer - 3a!acity "anagement is res!onsible for the control of the load in the cell.*t consists of 8 main functions7$. :edicated "onitored #esource


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the system.%. Admission 3ontrol7 acce!tsrefuses admission reuests based on the current loadon the dedicated monitored resources and the characteristics of the reuest8. 3ongestion 3ontrol7 detectsresolves overload situations-2. What eso+rces are )onitored for (apacity Manage)ent?

Answer G:2 4ower#eceived Total Fideband !owerOBS9 3odes#(S 3hannel Elements-. What adio Meas+re)ents are +sed for (ongestion Monitoring?

Answer G:ownlin #eceived 4owerD!lin #eceived Total Fideband 4ower-3. Are Syste) 8nfor)ation "loc7s 9S8"< trans)itted all the ti)e?

Answer - es05. *ow does =E ca)p 9synchroni4e< to a Node"?

Answer G$. DE uses the !rimary synchroni/ation channel +4-S3


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Answer GEvents %a-%d are for inter-freuency handover measurements and events 8a-8d arefor *#AT handover measurements.e8a7 the D"TS cell uality has moved below a threshold and a 5S" cell uality hadmoved above a threshold.e8b7 the 5S" cell uality has moved below a threshold.e8c7 the 5S" cell uality has moved above a threshold.e8d7 there was a change in the order of best 5S" cell list.00. What )ay happen when thereFs a )issing neighbor or an incorrect neighbor?

Answer GLAccess failure and handover failure7 may attem!t to access to a wrongscrambling code.L:ro!!ed call7 DE not aware of a strong scrambling code@ strong interference.L4oor data through!ut.L4oor voice uality.LEtc.02. *ow is inter>fre,+ency *andover triggered?

Answer GThe networ decides that inter freuency measurements need to be !erformed andsends the "EASD#E"ENT 3ONT#O2 "ESSA5E with "easurement ty!e set to

*nter-9reuency measurements. 5enerally it will set an Event as well along with themeasurements. The following are list of Events that can trigger "easurement #e!ort.LEvent %a7 3hange of (est 9reuencyLEvent %b7 The estimated uality of the currently used freuency is below acertain threshold and the estimated uality of a non-used freuency is above acertain thresholdLEvent %c7 The estimated uality of a non-used freuency is above a certainthresholdLEvent %d7 The estimated uality of the currently used freuency is below acertain thresholdLEvent %e7 The estimated uality of a non-used freuency is below a certainthresholdLEvent %f7 The estimated uality of the currently used freuency is above a certain

thresholdThe *nter-9reuency


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3o-located 5S" cells are assumed to have similar coverage and accessibility astheir res!ective F3:"A cells.21. What can we try to i)prove when access fail+re is high?

Answer GLFhen access failure is high we can try the following to im!rove #A3

Answer GThe EbNo reuirement for


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