UMTS Interview QA.doc

8/13/2019 UMTS Interview QA.doc

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General

1. What is the experience and involvement in your current and previous UMTS design projects?

Talk about your current and previous projects, your responsibilities, design objectives, tools used, activities involved, challenges,objectives met, etc.

Lin !udget

". What is a typical #ode! sensitivity level?

The service and load determines the NodeB sensitivity; in general, in a no-load condition, the sensitivity is between -11 dBm to-1! dBm. "or #ricsson, the NodeB sensitivity level is calculated at around$

%&1!.!$ -1!' dBm(&-)'$ -11* dBm(&-1!+$ -11 dBm(&- +'$ -11 dBm

$. What is a typical U% sensitivity level?

The service and load determines the # sensitivity; in general, in no-load condition, the sensitivity is between -1 dBm and-1! dBm. "or #ricsson, the # sensitivity level is calculated at around$

%&1!.!$ -11* dBm(&-)'$ -11! dBm

(&-1!+$ -11 dBm(&- +'$ -1 dBm/&0( $-* dBm

&. What is a typical #ode! maximum output po'er?

The ma2imum NodeB output power is usually ! 3 or ' 3, that is, ' dBm or ')dBm.

(. What is U% maximum transmit po'er in your lin )udget?

!1dBm.

*. What is a typical antenna gain?

The antenna gain depends on antenna model; in link budget we use around 14dBi.

+. What is a typical maximum path loss?

The ma2imum path loss is dependent on the service and vendor recommendations; typically it is in between 1 to 1' dB 5or urbanareas and between 1 to 1) dB 5or rural areas.

,. What is di--erence )et'een d!i and d!d?

dBi is the gain in dB 5rom isotropic source; dBd is the gain 5rom a dipole source.

dBd 6 !.1 7 dBi.

. What is the di--erence )et'een d! and d!m?

dBm is a unit o5 power level, measured in milli-watts in logarithm scale, that is,dBm 7 1 8 log9381 : where 3 is the power in 3atts

dB is not a unit, it is the di55erence in dBm.

1/. What is /d!m?

dBm 7 1 milli-watt.

11. 0o' does TM 'or ?

T reduces system noise, improves uplink sensitivity and leads to longer # battery li5e.

&ensitivity is the minimum input power needed to get a suitable signal-to-noise ratio 9&N<: at the output o5 the receiver. =t isdetermined by receiver noise 5igure, thermo noise power and re>uired &N<. Thermo noise power is determined by bandwidth andtemperature, &N< is determined by modulation techni>ue, there5ore the only variable is noise 5igure.



The cascading noise 5igure can be calculated by "riis e>uation 9/erald "riis:$

N" t 7 N" 1 6 9N" ! -1:?@1 6 9N" -1:?9@18@! : 6 ... 6 9N" i-1:?9@18@! 8...8@i:

s the e>uation shows, the 5irst block imposes the minimum and the most prominent noise 5igure on the system, and the 5ollowing blocks imposes less and less impact to the system provided the gains are positive. Ainear passive devices have noise 5igure e>ual totheir loss. T typically has a gain o5 1!dB.

There are typically top jumper, main 5eeder and a bottom jumper between antenna and BT&. T placed near antenna with ashort jumper 5rom antenna provides the best noise 5igure improvement the noise 5igure will be restricted to the top jumper loss9N" 1: and T 99N" ! -1:?@1:, and the remaining blocks 9main 5eeder and bottom jumper: have little e55ect.

To summariCe, a T has a gain thatDs close to 5eeder loss.

1". What are the pros and cons 2advantages and disadvantages3 o- TM ?

En the upside, a T reduces system noise, improves uplink sensitivity and leads to longer # battery li5e. En the downside,T imposes an additional insertion loss 9typically . dB: on the downlink and increases site installation and maintenancecomple2ity.

1$. What is typical TM gain?

T typically has a 1! dB gain; however, the e55ective gain comes 5rom noise 5igure reduction and the gain is close or e>uivalentto the 5eeder loss.

1&. Why TM are installed at the top near the antenna and not the )ottom near the #ode!?

Based on "riis #>uation, having a T near the BT& will have the top jumper and main 5eeder losses 9noise 5igures: cascaded inand a T will not be able to help suppress the losses.

1(. What is UMTS chip rate?

.+' /C.

1*. What is processing gain?

(rocessing gain is the ratio o5 chip rate over data bit rate, usually represented in decibel 9dB: scale. "or e2ample, with .+' /Cchip rate and 1!.!k data rate, the processing gain is$(@ 1!.!k 7 1 8 log 9 ,+' , ? 1!,! : 7 ! dB

1+. What are the processing gains -or 4S and 5S services?

%&1!.!$ ! dB(&-)'$ 1+dB(&-1!+$ 1 dB(&- +'$ 1 dB/&0( $ !dB

1,. 0o' to calculate maximum num)er o- users on a cell?

To calculate the ma2imum number o5 users 9 M : on a cell, we need to know$W $ chip rate 95or T& ,+' , chips per second:

EbNo $ #b?No re>uirement 9assuming dB 5or %&-1!.!k:i$ other-cell to in-cell inter5erence ratio 9assuming ) F:

R$ user data rate 9assuming 1!,! kbps 5or %&-1!.!k:G$ loading 5actor 9assuming F:

Take 1!.!kbps as e2ample$ 7 3 ? 9#nNo 8 91 6 i: 8 <: 8 G 7 ,+' , 9 8 91 6 .): 8 1!,! : 8 . 7 !.+

The number o5 users could also be hard-limited by EH&" code space. Take %&1!.!k 5or e2ample$ %&-1!.!k bearer needs 1 &"1!+ code. Total available codes 5or %&-1!.!k 7 1!+ ! 91 &")': ! 9' &"! ): 7 1!'. %onsider so5t-handover 5actor o5 1.+ and loading 5actor o5 F$ 1!' ? 1.+ 8. 7 ' uers?cell.

1 . What is %)6#o?

By de5inition #b?No is energy bit over noise density, i.e. is the ratio o5 the energy per in5ormation bit to the power spectral density9o5 inter5erence and noise: a5ter dispreading.



The power allocated to control channels may depend on e>uipment vendor recommendation. Typically no more than ! F o5 thetotal NodeB power is allocated to control channels, including %(=%/. /owever, i5 /&0( is deployed on the same carrier thenthe total power allocated to control channel may go up to ! to F because o5 the additional /&0( control channels re>uired.

&/. What is a typical 45840 po'er?

%(=%/ power typically takes about 1 F o5 the total NodeB power. "or a ! 3 9' dBm: NodeB, %(=%/ is around !3 9 dBm:.

=n urban areas where in-building coverage is taken care o5 by in-building installations, the %(=%/ may sometimes go as low as F because$

The coverage area is small since users are close to the site, and ore power can be allocated to tra55ic channels.

&1. 0o' much is your 0S>5 2max3 lin po'er?

/&0( link power is typically ' to dB below the ma2imum NodeB ma2imum output power. "or e2ample, 5or ' dBm ma2imum NodeB power the /&0( link power is *dBm.

&". 4onsider do'nlin only9 'hat are the major components in calculating maximum path loss9 starting -rom #ode!?

NodeB %(=%/ transmit power. Lumper and 5eeder connector loss. ntenna gain. Ever-the-air loss.

Building ? vehicle penetration loss. Body loss. #tc.

&$. What is maximum path;loss?

The ma2imum path-loss is how much signal is allowed to drop 5rom a transmitter to a receiver and maintains as good signal.

&&. Simple lin )udget 'ith a $/d!m 45840 and a ;1//d!m U% sensitivity9 ignoring anything in )et'een9 'hat is themaximum path loss?

9 1 : 7 6 1 7 1 dB.

&(. Suppose 8 have a maximum path;loss o- 1$/d!m9 'hat is the ne' path;loss i- a (d! )ody loss is added?

1! dB.

&*. What is channeli@ation code?

%hanneliCation codes are orthogonal codes used to spread the signal and hence provides channel separation, that is, channeliCationcodes are used to separate channels 5rom a cell.

&+. 0o' many channeli@ation codes are availa)le?

The number o5 channeliCation codes available is dependent on the length o5 code. =n the uplink the length is de5ined as between 'and ! ). =n the downlink the length is de5ined as between ' and 1!.

&,. re channeli@ation codes mutually orthogonal? 8- so9 'hy is <Arthogonality Bactor= re7uired in the lin )udget?

Mes, channeliCation codes are mutually orthogonal. Nonetheless, due to multi-path with variable time delay, channels 5rom thesame cell are no longer per5ectly orthogonal and may inter5ere with each other.

I0ownlink Erthogonality "actorJ, typically -) F, is there5ore needed in the link budget to account 5or the inter5erence andhence reduces pole capacity.

& . What is scram)ling code? 0o' many scram)ling codes there are?

&crambling codes are used to separate cells and #s 5rom each other, that is, each cell or # should have a uni>ue scramblingcode. There are 1! scrambling codes on the downlink and millions on the uplink.

(/. What is scram)ling <code group=?

The 1! scrambling codes are divided into )' code groups each code group has + scrambling codes.



%ode group i 9i 7 to ) : has codes 5rom i8+ to 9i61:8+-1, i.e. 9 -4: 9+-1 : 9 '- 11:.

(1. >o you divide scram)ling code groups into su)groups? 5lease give an example.

Mes, we divide the )' code groups into subgroups$ acro layer group$ !' code groups reserved 5or macro 9outdoor: sites. icro layer group$ 1) code groups reserved 5or micro 9in-building: sites. #2pansion group$ !' code groups reserved 5or 5uture e2pansion sites.

(". Which service usually needs higher po'er9 4S or 5S?

%onsider downlink and take %&-1!.! and (&- +'k 5or e2ample. The processing gain is ! 5or %&-1!.! and 1 5or (&- +'. The#b?No re>uirement is 4 5or %&-1!.! and 5or (&- +'. There5ore the power re>uirement is higher 5or %&-1!.! than (&- +'.

($. What is %)6#o re7uirement -or 0S>5 ?

The #b?No re>uirement 5or /&0( varies with user bit rate 9data rate:, typically ! 5or 4)+kbps and 5or ! bps.

(&. What is <noise rise=? What does a higher noise rise mean in terms o- net'or loading?

"or every new user added to the service, additional noise is added to the network. That is, each new user causes a Inoise riseJ. =ntheory, the Inoise riseJ is de5ined as the ratio o5 total received wideband power to the noise power. /igher Inoise riseJ valueimplies more users are allowed on the network, and each user has to transmit higher power to overcome the higher noise level.This means smaller path loss can be tolerated and the cell radius is reduced. To summariCe, a higher noise rise means highercapacity and smaller 5ootprint, a lower noise rise means smaller capacity and bigger 5ootprint.

((. What is <pilot pollution=?

&imply speaking, when the number o5 strong cells e2ceeds the active set siCe, there is Ipilot pollutionJ in the area. Typically theactive set siCe is , so i5 there are more than strong cells then there is pilot pollution.

0e5inition o5 Istrong cellJ$ pilots within the handover window siCe 5rom the strongest cell. Typical handover window siCe is between ' to )dB. "or e2ample, i5 there are more than ! cells 9besides the strongest cell: within 'dB o5 the strongest cell then thereis pilot pollution.

(*. What is a typical handover 'indo' si@e in your net'or ?

handover window siCe is usually between ' to )dB.

(+. What is <so-t handover= and <so-ter handover=?I&o5t handoverJ is when # has connection to multiple cells on di55erent NodeB.

I&o5ter handoverJ is when # has connection to multiple cells on same NodeB.

=n downlink a # can combine signals 5rom di55erent cells, improving the signal >uality. "or uplink and so5t handover, <N%selects the best signal 5rom di55erent NodeB. "or uplink and so5ter handover, a NodeB combines the signal 5rom di55erent sectors.

(,. >uring a handover9 i- one cell sends a po'er do'n re7uest and t'o cells send a po'er up re7uest9 shall the U% po'er up orpo'er do'n?

(ower down. s long as a good link can be maintained it is not necessary to power up in order to maintain multiple links.aintaining unnecessary multiple links increases noise rise and shall be avoided.

( . Suppose 'e are designing a 4S net'or and a 5S net'or 9 is there a major di--erence in the design consideration?

&erver dominance is the key di55erence. =n a %& network we shall limit the number o5 strong servers in any given area to no morethan the active set siCe to avoid pilot pollution 9in the downlink:. =n a (& network, however, there isnDt so5t handover in thedownlink so the server dominance is very important meaning ideally there should be only one dominant server in a given area.

*/. What is the active set si@e on your net'or ?

.

*1. 0o' many -ingers does a U% ra e receiver have?

'.

*". What is <compressed mode=?



Be5ore # can per5orm inter-5re>uency or =< T handover, it needs to have some time to lock on to the control channel o5 the other5re>uency or system and listen to the broadcast in5ormation. %ertain idle periods are created in radio 5rames 5or this purpose and iscalled Icompressed modeJ.

*$. >escri)e the po'er control schemes in UMTS?

Epen loop 5or # to access the network, i.e. used at call setup or initial access to set # transmit power. %losed outer loop$ <N% calculates the &=< target and sends the target to NodeB 9every 1 ms 5rame:. %losed inner loop$ NodeB sends the T(% bits to # to increase or decrease the power at 1, times a second.

*&. What is the -re7uency o- po'er control 2ho' -ast is po'er control3? Epen loop$ depends on parameter setting$

T time to wait between <<% retries 91 ms to + ms, typical 1 ms: %losed outer loop$ 1 times a second. %losed inner loop$ 1, times a second.

*(. !rie-ly descri)e 'hy open loop po'er control is needed and ho' it 'or s?

3hen a # needs to access to the network it uses < %/ to begin the process. < %/ is a shared channel on the uplink used by all #, there5ore may encounter contention 9collision: during multiple user

access attempts and inter5ere with each other. #ach # must estimate the amount o5 power to use on the access attempt since no 5eedback 5rom the NodeB e2ists as it does

on the dedicated channel. The purpose o5 open loop power control is to minimiCe the chance o5 collision and minimiCe the initial # transmit power to

reduce inter5erence to other #.

=nitial # transmit power 7 (rimaryO%(=%/O(ower %(=%/O<&%( 6 AO=nter5errnce 6constantOHalueO%prach

=nstead o5 sending the whole message, a ItestJ 9preamble: is sent. 3ait 5or answer 5rom NodeB. =5 no answer 5rom NodeB increase the power. Try and try until succeed or timeout.

**. What is po'er control <headroom=?

(ower control IheadroomJ is also called Ipower riseJ. =n a non-5ading channel the # needs to transmit a certain 5i2ed power. =n

a 5ading chennel a # reacts to power control commands and usually increases the transmit power. The di55erence between theaverage power levels o5 5ading and non-5ading channels is called Ipower riseJ or IheadroomJ.

*+. When in $;'ay so-t handover9 i- a U% receives po'er do'n re7uest -rom one cell and po'er up re7uest -rom the other "cells9 should the U% po'er up or do'n and 'hy?

(ower down. aintaining one good link is su55icient to sustain a call and having unnecessary stronger links creates moreinter5erence.

*,. Suppose t'o U% are served )y the same cell9 the U% 'ith 'ea er lin 2poor :B condition3 uses more <capacity=9 'hy doesthis mean?

The # with weaker <" link will re>uire NodeB to transmit higher tra55ic power in order to reach the #, resulting in less power5or other # there5ore consumes more IcapacityJ.

* . Under 'hat circumstances can a #ode! reach its capacity? What are the capacity limitations?

NodeB reaches its ma2imum transmit power, runs out o5 its channel elements, uplink noise rise reaches its design target, etc.

+/. What is <cell )reathing= and 'hy?

The cell coverage shrinks as the loading increases, this is called cell breathing.

=n the uplink, as more and more # are served by a cell, each # needs to transmit higher power to compensate 5or the uplinknoise rise. s a conse>uence, the # with weaker link 9 # at greater distance: may not have enough power to reach the NodeB there5ore a coverage shrinkage.

=n the downlink, the NodeB also needs to transmit higher power as more # are being served. s a conse>uence # with weakerlink 9greater distance: may not be reachable by the NodeB.



+1. 8s UMTS an uplin ;limited or do'nlin ;limited system?

T& system could be either uplink-limited or downlink-limited depending on the loading. =n a lightly loaded system, the #transmit power sets a coverage limitation there5ore it is uplink-limited. =n a heavily loaded system, the NodeB transmit powerlimits the number o5 #s it can serve there5ore it is downlink-limited.

+". What is the impact o- higher data rate on coverage?

/igher data rate has lower processing gain and there5ore a NodeB needs to transmit more power to meet the re>uired #b?No; thismeans the coverage is smaller 5or higher data rate.

+$. What is A4#S?E%N& stands 5or Erthogonal %hannel Noise &imulator. =t is a simulated network load usually by increasing the noise rise 5igure inthe NodeB.

UT: #

+&. What are the inter-aces )et'een each UT: # component?

u$ # to NodeB=ub$ NodeB to <N%=ur $ <N% to <N%=u$ <N% to &%

+(. !rie-ly descri)e the U% to UT: # protocol stac 2air inter-ace layers3.

The radio inter5ace is divided into layers$1. 5hysical layer 9Aayer 1, A1:$ used to transmit data over the air, responsible 5or channel coding, interleaving, repetition,

modulation, power control, macro-diversity combining.

!. Lin layer 9A!:$ is split into ! sub-layers edium ccess %ontrol 9 %: and <adio Aink %ontrol 9<A%:.• %$ responsible 5or multiple2ing data 5rom multiple applications onto physical channels in preparation 5or over-the-

air transmition.

• <A%$ segments the data streams into 5rames that are small enough to be transmitted over the radio link.

. Upper layer 9A :$ vertically partitioned into ! planes$ control plane 5or signaling and user plan 5or bearer tra55ic.• ::4 9<adio <esource %ontrol: is the control plan protocol$ controls the radio resources 5or the access network.

=n implementation$1. # has all layers.!. NodeB has (hysical Aayer.. <N% had % layer and <<% layer.

+*. !rie-ly descri)e UMTS air inter-ace channel types and their -unctions.

There are types o5 channels across air inter5ace physical channel, transport channel and logical channel$1. (hysical %hannel$ carries data between physical layers o5 # and NodeB.!. Transport %hannel$ carries data between physical layer and % layer.. Aogical %hannel$ carries data between % layer and <<% layer.

++. Give some examples o- 5hysical9 Transport and Logical channels.

1. Aogical %hannel$• %ontrol channel$ B%%/, (%%/, %%%/, 0%%/.• Tra55ic channel$ 0T%/, %T%/.

!. Transport %hannel$• %ommon control channel$ B%/, " %/, (%/, < %/, %(%/.• 0edicated channel$ 0%/, 0&%/.

. (hysical %hannel$• %ommon control channel$ (-%%(%/, &-%%(%/, (-&%/, &-&%/, %(=%/, =%/, (=%/, (0&%/, (< %/, (%(%/,

%0?% -=%/.• 0edicated channel$ 0(0%/, 0(%%/.



+,. What are the ::4 operation modes?=dle mode and connected mode.

+ . What are the ::4 states?

There are ' <<% &tates$ %ellO0%/, %ellO" %/, < O(%/ and %ellO(%/.< 7 T< N <egistration rea.

,/. What are transparent mode9 ac no'ledged mode and unac no'ledged mode?

Transparent mode corresponds to the lowest service o5 the <A% layer, no controls and no detection o5 missing data.

nacknowledged mode o55ers the possibility o5 segment and concatenate o5 data but no error correction or retransmissionthere5ore no guarantee o5 delivery.

cknowledged mode o55ers, in addition to mode 5unctions, acknowledgement o5 transmission, 5low control, error correctionand retransmission.

,1. Which layer2s3 per-orm ciphering -unction?

<<% 5or acknowledged mode 9 : and unacknowledged mode 9 :.% 5or transparent mode 9T :.

,". What is ACSB?

Erthogonal Hariable &preading "actor.

,$. 0o' many ACSB code spaces are availa)le?

Total EH&" codes 7 ! ). <eserved$ 1 &")' 5or &-%%(%/, 1 &"! ) 5or %(=%/, (-%%(%/, (=%/ and =%/ each. Total available code space 7 ! ) ' 91 &")': ' 9' &"! ): 7 !'+.

,&. 4an code space limit the cell capacity?

Mes, cell capacity can be hard-limited by code space. Take %&-1!.!k 5or e2ample$ %&-1!.!k bearer needs 1 &"1!+ code. Total available codes 5or %&-1!.!k 7 1!+ ! 91 &")': ! 9' &"! ): 7 1!'. %onsider so5t-handover 5actor o5 1.+$ 1!' ? 1.+ 7 )+ uers?cell.

,(. 4an a user have ACSB code as <1111=?

No, because I1111 J 9! ) times: is used by %(=%/.

,*. What are the sym)ol rates 2)its per sym)ol3 -or !5SD9 E5SD9 ,5SD and 1*E M?

B(&P$ 1. Q(&P$ !. +(&P$ .



+. 8n 8S; ( 'e have a 5# reuse -actor 25# step si@e3 and there-ore cannot use all (1" 5# codes9 'hy isnFt it necessary -orUMTS scram)ling codes?

Because =&-* is a synchroniCed network, di55erent (N codes have the same code se>uence with a time shi5t, there5ore we need tomaintain a certain (N step siCe to avoid multi-path problem. "or e2ample, i5 two sectors in the neighborhood have a small (Nseparation then signal arriving 5rom cell may run into the time domain o5 cell B, causing inter5erence.

T&, on the other hand, is not a synchroniCed network and all scrambling codes are mutually orthogonal so no need to maintain astep siCe.

,. What are coverage thresholds in your UMTS design and 'hy?

The coverage thresholds are based on # sensitivity, 5ading and penetration loss. ssuming # sensitivity o5 -11 dBm, 5ademargin o5 dB$ Eutdoor$ -11 dBm sensitivity 6 dB 5ade margin 7 -1 dBm. =n-vehicle$ -11 dBm 6 dB 6 +dB in-vehicle penetration loss 7 -*4dBm. =n-building$ -11 dBm 6 dB 6 1 dB in-building penetration loss 7 -* dBm.

. What is the %c68o target in your design?

The #c?=o target typically is between -1! to -1'dB. /owever, i5 a network is designed 5or data then the #c?=o target could go higherto around -1 dB because server dominance is more critical 5or a data network since there isnDt so5tware in the downlink.

1//. What is <Monte 4arlo simulation=?

&ince T& coverage is dependent on the loading, static coverage and >uality analysis 9<&%( and #c?=o: represents the network per5ormance in no-load condition. onte %arlo simulation is there5ore used to illustrate network per5ormance under simulatedloading consition.

1/1. What is the ey di--erence )et'een a static analysis and a Monte 4arlo simulation?

&tatic analysis can only show <&%( and #c?=o in no-load condition. onte %arlo simulation not only can show <&%( and #c?=o insimulated loading condition but also can show many more others$ mean served, cell loading, uplink and downlink capacity limitsreached, etc.

1/". What should )e run -irst 2'hat in-ormation should )e ready and loaded3 )e-ore running a Monte 4arlo simulation?

Be5ore running onte %arlo simulation, the 5ollowing should be completed or in place. <un prediction.

&pread the tra55ic. 0e5ine terminal types.

1/$. 0o' many snap shots and iteration do you usually have 'hen running Monte 4arlo simulation?

90epend on so5tware tool recommendations:.

1/&. What are the design D58Fs?

9<&%(, #c?=o, mean served, so5t handover ratio :

1/(. What plots do you usually chec a-ter running Monte 4arlo -or trou)le spots?

9<&%(, #c?=o, service probability, reasons 5or 5ailure :

1/*. What are the typical reasons o- -ailure in Monte 4arlo simulation?

0ownlink #b?No 5ailure 9%apacity:. 0ownlink #b?No 5ailure 9<ange:. plink #b?No 5ailure. Aow pilot &=<. Noise rise limit reached. #tc.

1/+. What does <tra--ic spread= mean?

ITra55ic spreadJ means spreading tra55ic 9number o5 terminals: in a cell coverage area.



ccess 5ailure and handover 5ailure$ may attempt to access to a wrong scrambling code. 0ropped call$ # not aware o5 a strong scrambling code, strong inter5erence. (oor data throughput. (oor voice >uality. #tc.

11,. What can 'e try to improve 'hen access -ailure is high?

3hen access 5ailure is high we can try the 5ollowing to improve < %/ per5ormance$ =ncrease ma2imum # transmit power allowed$ a2OallowedO AOT O(ower. =ncrease power >uickly$ powerOE55setO( . =ncrease number o5 preambles sent in a given preamble cycle$ preambleO<etransO a2. =ncrease the number o5 preamble cycles$ ma2O(reambleO%ycle. =ncrease number o5 <<% %onnection <e>uest retries$ N .

11 . What are the conditions you typically set to trigger 8: T handover?

<&%( and #c?=o are used to trigger =< T handover$ <&%( U -1 dBm. #c?=o U -1)dBm.

1"/. What are the typical D58s you use to measure a net'or and 'hat criteria?

ccess 5ailure rate 9U !F:. %all setup time 9%&$ over * F o5 the time V )-second 5or mobile-to-(&TN, *-second 5or mobile-mobile. (&$ over * F o5 the

time V -second:. 0ropped call rate 9U !F:. BA#<$ over * F o5 the blocks U !F. verage 0A? A throughput 5or (&0$ !1 kbps 5or loaded, !' kbps 5or unloaded.

1"1. What is the typical U% transmit po'er?

Haries - most o5 the time below dBm.

1"". 0ave your used %ricsson T%MS? 8- so

0o you know how to create command se>uenceS 3hat are the call se>uences you typically haveS %& long call, %& short call, (&0 call, etc. 3hat are the typical commands you have 5or %& and (& callS 0o you regularly stop and restart a new log 5ileS 3hy and when to stop and start a new 5ileS /ow do you stop a log 5ileS &top command se>uence 5irst, wait and make sure all e>uipment are in idle mode be5ore stop

logging.

1"$. >id you 'or on neigh)or prioriti@ation?

1"&. What is the typical event se7uence o- 8: T 0andover -rom $G to "G

#vent !d entering into compressed mode measurement o5 !@ candidates #vent a Heri5ication o5 !@ resources /andover 5rom T< N %ommand 5rom @ <N% to #

1"(. What are the possi)le causes -or an 8: T Bailure?

issing !@ relations Non availability o5 !@ <esources (oor !@ %overage issing @ <elations

1"*. What is 5aging Success :atio? What is the typical 5S: that you have seen in a UMTS net'or ?

(&< (aging <esponses to the (aging ttempts bout * F



1"+. What are the possi)le causes -or a lo'er 5S:?

Non-continuous <" %overage # going in and out o5 coverage area 5re>uently Hery /igh W(eriodic Aocation pdate TimerD Peeping #s in HA< long time a5ter it moved out o5 coverage Aower (aging %hannel (ower ccess %hannel (arameter =ssues 0elayed Aocation pdate when crossing the A ? %N Boundaries

1",. What are the possi)le causes -or a >rop 4all on a UMTS net'or ?

(oor %overage 90A ? A: (ilot (ollution ? (ilot &pillover issing Neighbor &% %ollisions 0elayed /andovers No resource availability 9%ongestion: 5or /and in Aoss o5 &ynchroniCation "ast "ading 0elayed =< T Triggers /ardware =ssues #2ternal =nter5erence

1" . U% is served )y " or $ S4 in S. 8t is identi-ying a S4 -rom $ rd tier9 Stronger and meets the criteria -or %vent1a or%vent1c. !ut S0A did not happen )ecause o- missing neigh)or relations? 0o' do you optimi@e this issue?

&tudy the (ilot spillover 5rom the rd Tier &% and control its coverage #ven a5ter controlling the coverage, i5 the spillover is there, dd the neighbor.

1$/. U% is served )y " S4 in S9 a S4 is coming in to Monitored Set and %vent1a is triggered. !ut U% is not receiving ctiveSet Update -rom #ode! and the call drops. What could )e possi)le causes -or this drop?

0elayed /andover Aoss o5 &ynchroniCation "ast "ading (ilot (ollution ? &pillover issues

1$1. What is 0ard 0andover in UMTS? When 'ill it happen?

/ard /andover in T& is a break be5ore make type /andover =t can happen in the inter <N% boundaries where there is no =ur link.

1$". What is the typical 4all Setup Time -or a $G U% to $G U% 4all? What are the possi)le :B related causes -or a delayed 4STin this type o- call?

) to * seconds ultiple <<% ttempts 9 # is on poor coverage need more than ccess ttempt: 0elayed (age <esponses /igh Aoad on (aging and?or ccess %hannel (aging ? ccess (arameters

1$$. What is So-t 0andover Averhead? What is the typical value in UMTS net'or ?

&o5t /andover Everhead is calculated in two ways. 1: verage ctive &et &iCe Total Tra55ic ? (rimary Tra55ic. !:&econdary ? Total Tra55ic

Typical Halues are like 1.4 9 vg ctive &et &iCe: or F 9&econdary ? Total :

1$&. What 'ill happen to the So-t 0andover Averhead 'hen you apply A4#S on the net'or ? nd Why?



3ith E%N&, the inter5erence 9load: increases. This leads to reduction in #c?=o o5 a (ilot, which reduces the pilot spillovers.<eduction in (ilot &pillover will reduce the &o5t /andover Everhead.

1$(. What are the possi)le causes -or an ccess Bailure in UMTS?

issing Neighbors (oor %overage (ilot (ollution ? &pillover (oor %ell <eselection %ore Network =ssues Non availability o5 resources. dmission %ontrol denies /ardware =ssues =mproper < %/ (arameters #2ternal =nter5erence

1$*. 2BA: %:84SSA# % 5%:8%#4%>3 What is :TW5? What is the signi-icance o- it?

<eceived Total 3ide-band (ower =t gives the Total plink (ower 9=nter5erence: level received at NodeB

1$+. 2BA: %:84SSA# % 5%:8%#4%>3 What is the System :e-erence 5oint at 'hich all the 5o'er Levels are measured in%ricsson #ode!?

&ystem <e5 (oint 5or #??? NodeB is at the output o5 T 9Between T and ntenna:

1$,. What are the typical values -or Hreportingrange1aF and Hreportingrange1)F?

dB and dB respectively.

1$ . What 'ill )e the impact 'hen you change Hreportingrange1aF -rom $ to & d! and Htimetotrigger1aF 1// to $"/ ms9 'ithoutchanging any other parameters?

<eduction in number o5 #vent1a 0elayed #vent1a trigger <eduction in verage ctive &et &iCe

0elay in #vent1a could increase 0A inter5erence, which could lead to a drop call or increase in verage (ower (er ser9reduction in cell capacity:

1&/. What is dmission 4ontrol?

dmission %ontrol is an algorithm which controls the <esource llocation 5or a new call and additional resource allocation5or an e2isting call. =ncase, i5 a cell is heavily a loaded and enough resources in terms o5 power, codes or %#s are notavailable, admission control denies permission 5or the additional resource re>uirement.

1&1. What is 4ongestion 4ontrol?

%ongestion %ontrol monitors the dynamic utiliCation o5 speci5ic cell resources and insures that overload conditions do notoccur. =5 overload conditions do occur, %ongestion %ontrol will immediately restrict dmission %ontrol 5rom grantingadditional resources. =n addition, %ongestion %ontrol will attempt to resolve the congestion by either down switching, orterminating e2isting users. Ence the congestion is corrected, the congestion resolution actions will cease, and dmission%ontrol will be enabled.



>L Transmitted4arrier 5o'er

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*( Idmit? 2 ll Guaranteed3 K 2 ll #on;Guaranteed3 K 2 ll Guaranteed;0S3

dmit? 2 ll Guaranteed3 K 2#on;Guaranteed60andover3 K 2 ll Guaranteed;0S3

dmit? 2Guaranteed60andover3 K 2 ll Guaranteed;0S3

maximumTransmission5o'er

5o'er :eserved -or 5o'er 4ontrol

4ongestion Triggered 4ongestion :esolved

p'r dm J p'r dmA--set Jp'rA--set./ I

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dmit? 2 ll Guaranteed3 K 2#on;Guaranteed60andover3 K 2 ll Guaranteed;0S3

dmit? 2Guaranteed60andover3 K 2 ll Guaranteed;0S3

maximumTransmission5o'er

5o'er :eserved -or 5o'er 4ontrol

4ongestion Triggered 4ongestion :esolved

p'r dm J p'r dmA--set Jp'rA--set./ I

1&". What is the maximum num)er o- 4hanneli@ation 4odes that can )e allocated -or 0S9 as per $G55 standard?

1 codes o5 &" 1).

1&$. What is H4ode MultiplexingF in 0S>5 ?

&haring the /& %hanneliCation %odes among more than one /& users within the !ms TT= period.

1&&. 2BA: %:84SSA# % 5%:8%#4%>3 8n %ricsson System9 ho' is the 5o'er allocated -or 0S>5

Power unutilized by R99 PS, CS and Comman Channels, is used for HS (P HS = P max - hsPowerMargin - P non-HS)

1&(. What are %vents that can trigger the 0S>5 4ell 4hange?

#vent 1d /& %hange o5 Best %ell in the ctive &et

#vent 1b or #vent 1c <emoval o5 the Best %ell 5rom the ctive &et

1&*. 0o' is typically the 4all Setup Time o- a 4SC call calculated in UMTS using L$ messages?

%&T is calculated as the time di55erence between W lertingD and the 5irst <<% %onnection <e>uest 9%all =nitiation:

messages.

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