Document of Utran (1)

8/11/2019 Document of Utran (1)

1/23

What is a typical NodeB sensitivity level?

The service and load determines the NodeB sensitivity; in general, in a no-loadcondition, the sensitivity is between -115dBm to -125dBm. For Ericsson, the NodeBsensitivity level is calclated at arond!

"#12.2! -12$ dBm%#-&$! -11' dBm%#-12(! -115 dBm%#-)($! -115 dBm

What is a typical UE sensitivity level?

The service and load determines the *E sensitivity; in general, in no-load condition,the sensitivity is between -1+5dBm and -12+dBm. For Ericsson, the *E sensitivitylevel is calclated at arond!

"#12.2! -11' dBm

%#-&$! -112 dBm%#-12(! -11+ dBm%#-)($! -1+5 dBm#%!-'5 dBm

What is a typical NodeB maximum output power?

The ma/imm NodeB ot0t 0ower is sally 2+ or $+, that is, $)dBm or$&dBm.

What is UE maximum transmit power in your link budget?

21dBm.

What is a typical antenna gain?

The antenna gain de0ends on antenna model; in lin bdget we se arond 13dBi.

What is a typical maximum path loss?

The ma/imm 0ath loss is de0endent on the service and vendor recommendations;ty0ically it is in between 1)5 to 1$+dB 4or rban areas and between 15+ to 1&+dB4or rral areas.

What is diference between dBi and dBd?

dBi is the gain in dB 4rom isotro0ic sorce; dBd is the gain 4rom a di0ole sorce.

dBd 2.15 6 dBi.

What is the diference between dB and dBm?

dBm is a nit o4 0ower level, measred in milli-watts in logarithm scale, that is,


2/23

dBm 6 1+ 7 log871+++9 where is the 0ower in atts dB is not a nit, it is thedi:erence in dBm.

What is 0dBm?

+dBm 6 1 milli-watt.

ow does !"# work?

T redces system noise, im0roves 0lin sensitivity and leads to longer *Ebattery li4e. #ensitivity is the minimm in0t 0ower needed to get a sitable signal-to-noise ratio 8#Ngre, thermo noise 0ower and re?ired #Ngre.

The cascading noise >gre can be calclated by Friis e?ation 8erald Friis9!

NFt 6 NF1 8NF2-19@A1 8NF)-19@8A17A29 ... [email protected]

s the e?ation shows, the >rst bloc im0oses the minimm and the most0rominent noise >gre on the system, and the 4ollowing blocs im0oses less andless im0act to the system 0rovided the gains are 0ositive. inear 0assive deviceshave noise >gre e?al to their loss. T ty0ically has a gain o4 12dB.

There are ty0ically to0 Cm0er, main 4eeder and a bottom Cm0er between antennaand BT#. T 0laced near antenna with a short Cm0er 4rom antenna 0rovidesthe best noise >gre im0rovement D the noise >gre will be restricted to the to0

Cm0er loss 8NF19 and T 88NF2-19@A19, and the remaining blocs 8main 4eeder andbottom Cm0er9 have little e:ect.

To smmarie, a T has a gain thats close to 4eeder loss.

What are the pros and cons $advantages and disadvantages% o& !"#?

Gn the 0side, a T redces system noise, im0roves 0lin sensitivity and leads tolonger *E battery li4e. Gn the downside, T im0oses an additional insertion loss8ty0ically +.5dB9 on the downlin and increases site installation and maintenancecom0le/ity.

What is typical !"# gain?

T ty0ically has a 12 dB gain; however, the e:ective gain comes 4rom noise >gre

redction and the gain is close or e?ivalent to the 4eeder loss.

Why !"# are installed at the top near the antenna and not the bottomnear the NodeB?

Based on Friis E?ation, having a T near the BT# will have the to0 Cm0er andmain 4eeder losses 8noise >gres9 cascaded in and a T will not be able to hel0s00ress the losses.


3/23

What is U"!' chip rate?

).($.

What is processing gain?

%rocessing gain is the ratio o4 chi0 rate over data bit rate, sally re0resented indecibel 8dB9 scale. For e/am0le, with ).($ chi0 rate and 12.2 data rate, the0rocessing gain is!

%A12.26 1+ 7 log 8),($+,+++ @ 12,2++9 6 25dB

What are the processing gains &or (' and )' services?

"#12.2!25dB%#-&$! 1(dB%#-12(! 15dB%#-)($! 1+dB#%! 2dB

ow to calculate maximum number o& users on a cell?

To calclate the ma/imm nmber o4 sers 8M9 on a cell, we need to now!

W! chi0 rate 84or *T# ),($+,+++ chi0s 0er second9EbNo! Eb@No re?irement 8assming )dB 4or "#-12.29i! other-cell to in-cell inter4erence ratio 8assming &+H9R! ser data rate 8assming 12,2++ b0s 4or "#-12.29I! loading 4actor 8assming 5+H9

Tae 12.2b0s as e/am0le! 6 @ 8EnNo 7 81 i9 7 nition Eb@No is energy bit over noise density, i.e. is the ratio o4 the energy 0erin4ormation bit to the 0ower s0ectral density 8o4 inter4erence and noise9 a4terdis0reading.

Eb@No 6 %rocessing Aain #=ned as between $ and 25&. =n the downlin the lengthis de>ned as between $ and 512.

#re channeliation codes mutually orthogonal? ,& so- why is

9@rthogonality Aactor: re+uired in the link budget?

Qes, channeliation codes are mtally orthogonal. Nonetheless, de to mlti-0athwith variable time delay, channels 4rom the same cell are no longer 0er4ectlyorthogonal and may inter4ere with each other.

Lownlin Grthogonality FactorM, ty0ically 5+-&+H, is there4ore needed in the linbdget to accont 4or the inter4erence D and hence redces 0ole ca0acity.

What is scrambling code? ow many scrambling codes there are?

#crambling codes are sed to se0arate cells and *Es 4rom each other, that is, each

cell or *E shold have a ni?e scrambling code. There are 512 scrambling codeson the downlin and millions on the 0lin.

What is scrambling 9code group:?

The 512 scrambling codes are divided into &$ code gro0s D each code gro0 has (scrambling codes.

"ode gro0 i8i6 + to &)9 has codes 4rom i7( to 8i197(-1, i.e. 8+-39 8(-159R85+$-5119.

;o you divide scrambling code groups into subgroups? )lease give anexample4

Qes, we divide the &$ code gro0s into sbgro0s!

K acro layer gro0! 2$ code gro0s reserved 4or macro 8otdoor9 sites.K icro layer gro0! 1& code gro0s reserved 4or micro 8in-bilding9 sites.K E/0ansion gro0! 2$ code gro0s reserved 4or 4tre e/0ansion sites.

Which service usually needs higher power- (' or )'?


9/23

"onsider downlin and tae "#-12.2 and %#-)($ 4or e/am0le. The 0rocessing gainis 25 4or "#-12.2 and 1+ 4or %#-)($. The Eb@No re?irement is 3 4or "#-12.2 and 54or %#-)($. There4ore the 0ower re?irement is higher 4or "#-12.2 than %#-)($.

What is Eb*No re+uirement &or ';)#?

The Eb@No re?irement 4or #% varies with ser bit rate 8data rate9, ty0ically 2 4or3&(b0s and 5 4or 2b0s.

What is 9noise rise:? What does a higher noise rise mean in terms o&network loading?

For every new ser added to the service, additional noise is added to the networ.That is, each new ser cases a Lnoise riseM. =n theory, the Lnoise riseM is de>nedas the ratio o4 total received wideband 0ower to the noise 0ower. igher LnoiseriseM vale im0lies more sers are allowed on the networ, and each ser has totransmit higher 0ower to overcome the higher noise level. This means smaller 0athloss can be tolerated and the cell radis is redced. To smmarie, a higher noise

rise means higher ca0acity and smaller 4oot0rint, a lower noise rise means smallerca0acity and bigger 4oot0rint.

What is 9pilot pollution:?

#im0ly s0eaing, when the nmber o4 strong cells e/ceeds the active set sie, thereis L0ilot 0olltionM in the area. Ty0ically the active set sie is ), so i4 there are morethan ) strong cells then there is 0ilot 0olltion.

e>nition o4 Lstrong cellM! 0ilots within the handover window sie 4rom the strongestcell. Ty0ical handover window sie is between $ to &dB. For e/am0le, i4 there aremore than 2 cells 8besides the strongest cell9 within $dB o4 the strongest cell then

there is 0ilot 0olltion.

What is a typical handover window sie in your network?

handover window sie is sally between $ to &dB.

What is 9so&t handover: and 9so&ter handover:?

L#o4t handoverM is when *E has connection to mlti0le cells on di:erent NodeB.

L#o4ter handoverM is when *E has connection to mlti0le cells on same NodeB.

=n downlin a *E can combine signals 4rom di:erent cells, im0roving the signal?ality. For 0lin and so4t handover,


10/23

%ower down. s long as a good lin can be maintained it is not necessary to 0ower0 in order to maintain mlti0le lins. aintaining nnecessary mlti0le linsincreases noise rise and shall be avoided.

'uppose we are designing a (' network and a )' network- is there ama


11/23

K The 0r0ose o4 o0en loo0 0ower control is to minimie the chance o4 collision andminimie the initial *E transmit 0ower to redce inter4erence to other *E.

K =nitial *E transmit 0ower 6 %rimaryS"%="S%ower D "%="S/ed 0ower. =n a 4ading chennel a *E reacts to0ower control commands and sally increases the transmit 0ower. The di:erencebetween the average 0ower levels o4 4ading and non-4ading channels is calledL0ower riseM or LheadroomM.

When in 81way so&t handover- i& a UE receives power down re+uest &rom

one cell and power up re+uest &rom the other 3 cells- should the UE powerup or down and why?

%ower down. aintaining one good lin is sOcient to sstain a call and havingnnecessary stronger lins creates more inter4erence.

'uppose two UE are served by the same cell- the UE with weaker link $poor.A condition% uses more 9capacity:- why does this mean?

The *E with weaer


12/23

=n the downlin, the NodeB also needs to transmit higher 0ower as more *E arebeing served. s a conse?ence *E with weaer lin 8greater distance9 may not bereachable by the NodeB.

,s U"!' an uplink1limited or downlink1limited system?

*T# system cold be either 0lin-limited or downlin-limited de0ending on theloading. =n a lightly loaded system, the *E transmit 0ower sets a coveragelimitation there4ore it is 0lin-limited. =n a heavily loaded system, the NodeBtransmit 0ower limits the nmber o4 *Es it can serve there4ore it is downlin-limited.

What is the impact o& higher data rate on coverage?

igher data rate has lower 0rocessing gain and there4ore a NodeB needs totransmit more 0ower to meet the re?ired Eb@No; this means the coverage issmaller 4or higher data rate.

What is @(N'?

G"N# stands 4or Grthogonal "hannel Noise #imlator. =t is a simlated networ loadsally by increasing the noise rise >gre in the NodeB.

What are the inter&aces between each U!.#N component?

*! *E to NodeB=b! NodeB to


13/23

Briey describe U"!' air inter&ace channel types and their &unctions4

There are ) ty0es o4 channels across air inter4ace D 0hysical channel, trans0ortchannel and logical channel!

K %hysical "hannel! carries data between 0hysical layers o4 *E and NodeB.

K Trans0ort "hannel! carries data between 0hysical layer and " layer.K ogical "hannel! carries data between " layer and


14/23

ow many @D'A code spaces are available?

K Total GJ#F codes 6 25&.K


15/23

"a0acity anagement is res0onsible 4or the control o4 the load in the cell. =tconsists o4 ) main 4nctions!

edicated onitored


16/23

Qes.

,n ,'1G> we have a )N reuse &actor $)N step sie% and there&ore cannot useall >23 )N codes- why isnHt it necessary &or U"!' scrambling codes?

Becase =#-'5 is a synchronied networ, di:erent %N codes have the same code

se?ence with a time shi4t, there4ore we need to maintain a certain %N ste0 sie toavoid mlti-0ath 0roblem. For e/am0le, i4 two sectors in the neighborhood have asmall %N se0aration then signal arriving 4rom cell may rn into the time domain o4cell B, casing inter4erence.

*T#, on the other hand, is not a synchronied networ and all scrambling codesare mtally orthogonal so no need to maintain a ste0 sie.

What are coverage thresholds in your U"!' design and why?

The coverage thresholds are based on *E sensitivity, 4ading and 0enetration loss.ssming *E sensitivity o4 -11+dBm, 4ade margin o4 5dB!

K Gtdoor! -11+dBm sensitivity 5dB 4ade margin 6 -1+5dBm.K =n-vehicle! -11+dBm 5dB (dB in-vehicle 0enetration loss 6 -'3dBm.K =n-bilding! -11+dBm 5dB 15dB in-bilding 0enetration loss 6 -'+dBm.

What is the Ec*,o target in your design?

The Ec@=o target ty0ically is between -12 to -1$dB. owever, i4 a networ isdesigned 4or data then the Ec@=o target cold go higher to arond -1+dB becaseserver dominance is more critical 4or a data networ D since there isnt so4tware inthe downlin.

What is 9"onte (arlo simulation:?

#ince *T# coverage is de0endent on the loading, static coverage and ?alityanalysis 8


17/23

K #0read the traOc.K e>ne terminal ty0es.

ow many snap shots and iteration do you usually have when running"onte (arlo simulation?

8e0end on so4tware tool recommendations9.

What are the design ),Hs?

8


18/23

). *E then ses scrambling code = to obtain "%=", ths cam0ing to aNodeB.

What could be the cause o& so&t handover &ailure?

K *E isse.

K ned.K Etc.

What are the three sets in handover?

The ) sets in handover are!

K ctive set D the list o4 cells which are in so4t handover with *E.K onitored set D the list o4 cells not in active set bt


19/23

K e)d! there was a change in the order o4 best A# cell list.

What may happen when thereHs a missing neighbor or an incorrectneighbor?

K ccess 4ailre and handover 4ailre! may attem0t to access to a wrong

scrambling code.K ro00ed call! *E not aware o4 a strong scrambling code, strong inter4erence.K %oor data throgh0t.K %oor voice ?ality.K Etc.

What can we try to improve when access &ailure is high?

hen access 4ailre is high we can try the 4ollowing to im0rove

What is the typical UE transmit power?

Jaries - most o4 the time below +dBm.

ave your used Ericsson !E"'? ,& so=K o yo now how to create command se?enceYK hat are the call se?ences yo ty0ically haveY "# long call, "# short call,

%# call, etc.K hat are the ty0ical commands yo have 4or "# and %# callYK o yo reglarly sto0 and restart a new log >leY hy and when to sto0 and

start a new >leY


20/23

K ow do yo sto0 a log >leY #to0 command se?ence >rst, wait and maesre all e?i0ment are in idle mode be4ore sto0 logging.

;id you work on neighbor prioritiation?

%lease e/0lain.

What is the typical event se+uence o& ,.#! andover &rom 8/ to 3/

K Event 2d D entering into com0ressed mode D measrement o4 2Acandidates D Event )a D Jeri>cation o4 2A resorces D andover 4rom*T


21/23

# UE is served by 3 or 8 '( in #'4 ,t is identi&ying a '( &rom 8rd tier-'tronger and meets the criteria &or Event2a or Event2c4 But '@ did nothappen because o& missing neighbor relations? ow do you optimie thisissue?

K #tdy the %ilot s0illover 4rom the )rdTier #" and control its coverage

K Even a4ter controlling the coverage, i4 the s0illover is there, dd theneighbor.

# UE is served by 3 '( in #'- a '( is coming in to "onitored 'et andEvent2a is triggered4 But UE is not receiving #ctive 'et Update &romNodeB and the call drops4 What could be possible causes &or this drop?

K elayed andoverK oss o4 #ynchroniationK Fast FadingK %ilot %olltion @ #0illover isses

What is ard andover in U"!'? When will it happen?

K ard andover in *T# is a brea be4ore mae ty0e andover K =t can ha00en in the inter


22/23

K ith G"N#, the inter4erence 8load9 increases. This leads to redction in Ec@=o o4 a%ilot, which redces the 0ilot s0illovers.


23/23

K dmission "ontrol is an algorithm which controls the

Document of Utran (1)

Documents

Transcript of Document of Utran (1)