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Drive Test/RF Optimization/RF Planning By: -Faisal Khan (RF Engineer) ontents: !"# Drive Test (TE#" $%&%' !EE* PROBE + ,"""T,T .%' #,PFO$% #O# 0%1) .) nstallation o2 TE#" $%&%' 1) ntro345tion to Drive Test an3 Types o2 Drive Test ("FT l4ster et5) ') Drive Test Parameters an3 ,nalysis 0) 6eri2ying 5l4tter type (4r7an s474r7an r4ral et5%) ) omplete 8or9ing o2 TE#" $%&'  ) Physi5al 6eri2i5ation + Pre an3 Post Drive ;) on2ig4ration o2 the Tems Kit 2or 2or . 1 ' 0 #o7ile + 3ata) =ith . 1 ' an3 0 mo7ile $) ?og File ,nalysis @) .6  which corresponds to /Dual of maD. . 12 MS Be&aior Modi" -" . Call can e originated on the 3CC7 or the TC7 fre!uencies. 7ence M%I8 values will e reFected only for calls on TC7 fre!uency and not on 3CC7 fre!uency . Step% ?or :T@6

Intra Site Handoer Intra 7andover is performed to chec) whether handover is ta)ing place oth ways on the Site. 7andover is performed among all the Sectors of the Site. Inter Site Handoer Inter 7andover is performed to chec) whether handover is ta)ing place oth ways on the Site with its adacent neighor. 7andover needs to chec)ed mandatorily for primary neighor.

7andover is performed with the entire dened neighorNs in the integration sheet.

Step% ?or :T@" Idle :rie i% per?ormed in t9o ?a%&ion%)@ !ormal :rie re,uen(' o( :rie !ormal :rie  This is done to frame the potential area of the new site planned. It also helps us to get to )now the important neighoring sites for which the handover has to ta)e place.

re,uen(' o( :rie  This is done y loc)ing the 3CC7 fre!uency of the serving cell and performing the drive for the same cell unless the moile enters into #o Service Mode. This is useful for ma)ing decision related to GSM antenna height" tilt" and orientation. :edi(ated :rie @edicated drive is an important part of @rive Test. 7ere call is made to a test numer and drive is done for the potential areas of  the Site. @uring drive eing carried out one has constantly monitor parameters such as /A $evel" /A uality" SI" @TA" C4I /atio" 7opping Channel" #eighor list" T% Timing %dvance;. Constant changes in this parameter are helpful for post 8ptimi?ation of  the site.

 Drive Test Learning: 1)

What is the motivation behind GSM Air Interface drive testing?

  Ans) GSM Drive testing is traditional and best way to verify networ !erformance for "ew Sites or #$isting sites. Drive testing can be ased for vario%s ob&ectives lie'    

(overage verification "ew site erformance *erification and +ield o!timi,ation "etwor roblem tro%ble shooting lie Dro! calls- andover fail%re- oor (overage !atches- oor /0 %ality !atches- etc 2enchmaring Drive test to find o%t (overage and %ality com!arison against com!etitors networs.

3) 4y!es of Drive 4ests?   Ans) 

"ew Site Drive 4est 5(overage Drive)



2ench6maring Drive 4est 5(om!arative Drive) Migration Drive 4est 5"ight activity and Software 7!6gradation) /o%te Drive 4est.

 

3) ow to do (overage verification Drive test?  Ans) 2est way to do it by !%tting 4#MS hone in Idle mode and drive across targeted ro%tes . 

In Idle mode- MS will meas%re 2(( 4/08s 4ime slot 9 and 4S 9 transmit always f%ll !ower  which is consider as real foot !rint of 2(( 5 which is call as (ell foot !rint ) and s%ch /0 :#*#: is /0 :#*#: +%ll beca%se 4IM#S4;: 9 doesn8t have D40 and ;W#/ (;"4/;:  2%t when yo% do Dedicate mode Drive testing then 4( 4/0 has most of the time D40 ;" and ;W#/ (ontrol too so that /0 :#*#: Meas%rement is /0 :#*#: S72 which is not gen%ine (ell foot !rint. ; W If the cell is really covering far away from the site" other options are reducing the coverage y down tilting the antennas" reducing antenna height" changing antenna or reducing output power W If it is a rural area and need to cover a larger area" EDtended /ange feature might e useful to e considered.

t&er Rea%on @rop due other reason e!ual to total numer of drops sutracts all drops with reason. If any of the aove drop reason didnLt meet the criteria" the reason for drop will e in the V8ther /easonL. roale /eason 74J fault

7ardware rolem Managed 8ect in 3TS;

@isturance

$in)4 Transmission disturance prolem

arameter Setting

Jrongly dened setting for e.g. $%C ' $ocation %rea Code;

Moile Station

MS prolem

Interference

Interference prolem Oplin);

7ow to analy?e: W Chec) the 3TS error log for hardware faults. /un commands: /AE$ = /AM2 to loo) the hardware faults log; W Chec) if ICM is indicating uplin) interference in the cell. W Chec) with 8=M regarding transmission prolems" 7J prolems and service aHecting maintenance wor) during the time period.  The average cell downtime and TC7 availaility should also e chec). It might e intermittent lin) connection. W Chec) oect type M8TS" which is ased on drop on Timeslot TS; in order to nd faulty devices.

TCH :rop Anal'%i% 1. Radio in Time@ut

Every time a S%CC7 message cannot e decoded the radio lin) time*out counter is decreased y 5. If the message can e decoded the counter is incremented y >. 7owever" the value cannot eDceed the initial value. The initial value is set y the parameter /$I#UT for radio lin) time*out in the moile station and y /$I#UO for timeout in the 3SC. If the moile moves out of  coverage and no measurement reports are received in the 3SC" there will e a radio lin) time*out and the message Channel /elease cause: anormal release" unspecied; is sent to the

moile station and the S%CC7 is deactivated in the 3TS. % Clear /e!uest message is sent to the MSC. To e sure that the moile has stopped transmitting" the 3SC now waits /$I#UT S%CC7 periods efore the timeslot is released and a new call can e estalished on the channel. 2. a'er 2 Time@ut

If the 3TS never get an ac)nowledgement on a $ayer > message after the time T>&&A#>&&" the 3TS will send Error Indication cause: T>&& eDpired; to the 3SC" which will send Channel /elease cause: anormal release" timer eDpired; to the moile station and a Clear /e!uest to the MSC. The S%CC7 is deactivated and the 3SC waits /$I#UT S%CC7 periods efore the timeslot is released and a new call can use the channel. This is only valid if the call is in steady state" i.e. not during handover or assignment. 3. Relea%e Indi(ation

Jhen the 3TS received a layer > @ISC frame from the moile it replies with a $ayer > O% frame to the moile station and a /elease Indication to the 3SC. The system does only react on /elease Indication if it is received during a normal disconnection situation. If such a message is received uneDpectedly this will usually cause radio lin) time*out or timer T>&& eDpiration as the moile station stops the transmitting of measurement reports. It is also possile that the release will e normal depending on when the /elease Indication is received. 4. MSC Time@ut #ormal /elease:

If the MSC never received a response on a message e.g. Identity /e!uest; and there is no radio lin) time*out or layer > time*out" the MSC will send a Clear Command to the 3SC. The time*out is depending on the message. Jhen receiving Clear Command" the

3SC will send a Channel /elease cause: normal release; and then deactivates the S%CC7. /eect only S@CC7;: If the MSC never receives a response on the rst message after Estalish Indication" the MSC will send a reect message. If the connection was a $ocation Opdate it will e a $ocation Opdate /eect cause: networ) failure; and if the connection was a moile originating call CM Service /e!uest; a CM Service /eect cause: networ) failure; will e sent. The MSC will then send a Clear Command to the 3SC and the call is cleared y Channel /elease cause: normal release;. 5. A%%i*nment to TCH

3efore sending an %ssignment Command from the 3SC at TC7 assignment" the following two criterions have to e fullled: a. There must e a TC7 channel availale" i.e. no congestion . The locating algorithm must have received at least one valid measurement report. If either of the criterions is not fullled" %ssignment Command will not e sent and a Channel /elease cause: anormal release" unspecied; will e sent to the moile station and a Clear /e!uest to the MSC. TCH :rop rea%on 01  The classication of TC7 @rop /easons are arranged in the order of priority: 5.EDcessiveTiming %dvance >.$ow Signal Strength -.3ad uality .Sudden $oss of Connection ,.8ther /easons 7-(e%%ie Timin* Adan(e

 The TC7 @rop counters due to EDcessive Timing %dvance will pegged when the during the time of disconnection" the last  Timing %dvance value recorded was higher than the  T%$IM arameter. This drop reason is commonly apparent to isolated or island sites with a wide coverage area. A(tion) Chec) if the cell parameter T%$IM is X Y+-Y Solution) Set T%$IM to a value close to +-.  Tilt antenna4reduce antenna height4output power" etc. for co* channel cells.

TCH :rop Rea%on% 02 o9 Si*nal Stren*t& on :o9n or Dplin or Bot& in%

 The drops counters due to $ow Signal  Strength will e pegged when the Signal Strength during the last Measurement /eport efore the call dropped is elow the $8JSS@$ and4or $8JSSO$  Thresholds. $8JSS@$ and $8JSSO$ are 3SC EDchange roperty parameter which is used only for statistics purposes and does not aHect the ehavior of calls. If oth O$ and @$ Signal Strength are elow the thresholds" only @rop due to $ow SS 3$ will pegged. #ormally a call is dropped at the order of large rural cell with insu9cient coverage. 3ad tunnel coverage ecause many dropped calls as well as so called coverage holes. 3ad indoor coverage will result in dropped calls. 3uilding shadowing could e another reason. A(tion) Chec) coverage plots. Chec) output power. Chec) power alance and lin) udget. Chec) if 8mni site. Chec) antenna conguration = type.

Chec) antenna installation. erform drive tests = site survey. Chec) T/A4TS with high C8#E//C#T. Solution) %dd a repeater to increase coverage in for eDample a tunnel. Change to a etter antenna with higher gain; for the ase station. %dd a new ase station if there are large coverage holes. 3loc)4@eloc) T/A TCH :rop Rea%on% 03 Poor ualit' on :o9n or Dplin or Bot& in%

 The drops counters due to 3ad uality will e pegged when the Signal Strength during the last Measurement /eport efore the call dropped is aove the 3%@@$ and4or 3%@O$ Thresholds. 3%@@$ and 3%@O$ eDpressed in @TO; are 3SC EDchange roperty parameter which is used only for statistics purposes and does not aHect the ehavior of calls. If oth O$ and @$ uality are aove the thresholds" only @rop due to 3%@ uality 3$ will pegged. rolem on 3ad uality is usually associated with Co*channel Interference on 3CC7 or TC7. 2aulty M%I8 assignment can cause fre!uency collisions on co*sited cells especially on 5D5 /euse. EDternal interference is also one possile cause of prolem on !uality. A(tion) Chec) C4I and C4% plots. Chec) 2re!uency lan Co*3CC7 or Co*3SIC rolem;. Chec) M%I8" 78" 7S# parameters. Chec) 278 if correctly congured 33 or S1;. Chec) for EDternal Interference.

erform drive tests. Solution) Change 3CC7 fre!uency. Change 3SIC. Change M%I8" 78" 7S#. Change 278. /ecord /I/ or on*site 2re!uency Scanning to identify source of interference. Ose availale radio features. TCH :rop Rea%on% 04 Sudden o%% o? Conne(tion

@rops due to Sudden $oss are drops that have not een registered as low signal strength" eDcessive timing advance" ad !uality or hardware other; reasons" and the locating procedure indicates missing measurement results from the MS.  There are some common scenarios that could lead to Sudden $oss of connections such as very sudden and severe drops in signal strength" such as when suscriers enter into uildings" elevators" par)ing garages" etc." very sudden and severe occurrence of interference" MS runs out of attery during conversation" 7andover $ost" 3TS 7J faults" Synchroni?ation or %* is lin) fault transmission faults;" and MS 2aults. A(tion) Chec) 3TS Error $ogs" %larms and 2ault Codes. Chec) C8#E//C#T per T/A and TS. Chec) Transmission $in) %*is;. Chec) for @I Slips. Chec) $%@ Congestion. Correlate 7andover $ost to @rops due to Sudden $oss

Solution) 2iD 7ardware 2aults and %larms. /eset T/A with high C8#E//C#T. Ensure that Synchroni?ation and %*is $in) are stale. Change /3$T with high @I Slips. Change C8#2%CT or increase Transmission Capacity Investigate 78 $ost rolem TCH :rop Rea%on% 05 TCH :rop% due to t&er Rea%on%  TC7 drops due to 8ther /easons are computed y sutracting the sum of drops due to EDcessive T%" $ow SS" 3ad uality and Sudden $oss from the Total TC7 @rop Counts. @rops due to 8ther /easons are generally associated with hardware prolems" transmission lin) prolems on %*is" %ter or %interfaces" and sometimes 7andover $ost. A(tion) Chec) 3TS Error $ogs. Chec) %larms and 2ault Codes. Chec) C8#E//C#T per T/A and TS. Chec) Transmission $in) %*is;. Chec) for @I Slips. Correlate 7andover $ost to @rops due to 8ther /easons Solution) 2iD 7ardware 2aults and %larms. /eset T/A with high C8#E//C#T. Ensure that Synchroni?ation and %*is $in) are stale. Change /3$T with high @I Slips. Investigate 78 $ost rolem

Pro+lem rea%on o? drop in S:CCH o9 Si*nal Stren*t& on :o9n or Dplin   The reason for poor coverage could e too few sites" wrong output power" shadowing" no indoor coverage or networ) e!uipment failure. A(tion: Chec) coverage plots.Chec) output power. erform drive tests. Chec) 3TS error log Solution: %dd new sites. Increase output power. /epair faulty e!uipment. Poor ualit' on :o9n or Dplin  A(tion: Chec) C4I and C4% plots. Chec) fre!uency plan. erform drive tests. Solution: Change fre!uency. Ose availale radio features. Too Hi*& Timin* Adan(e A(tion: Chec) if the cell parameter T%$IM is X styleRYfont* weight: oldQYSolution: Set T%$IM to a value close to +-. Tilt antenna4reduce antenna height4output power" etc. for cochannel cells. Mo+ile 7rror Some old moiles may cause dropped calls if certain radio networ) features are used. %nother reason is that the MS is damaged and not wor)ing properly. A(tion: Chec) MS Feet. Solution: Inform operator. Su+%(ri+er Be&aior oorly educated suscriers could use their handsets incorrectly y not raising antennas" choosing illadvised locations to attempt calls" etc. A(tion: Chec) customer complaints and their MS.

Batter' la9 Jhen a suscrier runs out of attery during a conversation" the call will e registered as dropped call due to low signal strength or others. A(tion: Chec) if MS power regulation is used. Chec) if @TA uplin) is used. Con*e%tion on TCH the S@CC7 is dropped when congestion on TC7. A(tion: Chec) TC7 congestion Solution: Increase capacity on TC7 or using features li)e %ssignment to another cell" Cell $oad Sharing" 7CS" @ynamic 7alf* /ate %llocation and 2/*7/ Mode %daptation etc

Summar') 1. S: :rop rea%on% and Solution%)@ 5.3ad uality @ownlin) >.$ow Signal strength

Interference i.e. fre!uency heating Site 8vershoot i.e. %dust Tilt

2. TCH :rop Rea%on% and %olution%)@ 5.$ow Signal strength @ownlin) >.$ow Signal strength Oplin)

Site 8vershoot i.e. Increase Tilt Site is not ServingMaDimum tilt; i.e. release tilt Tilt One!ual Connector loose 3TS Connection $oose

Tilt Con(ept) 0aMain always e (&& eDpansion can e (&& and 56&& " 0+In terms of coverage 56&&R(&&> i.e. (&& Mech. Tilt is  then 56&& Mech. Tilt will e >" 0(  Tilt for @ense areas ***-" Mechanical 0d Tilt for 8pen %reas****(&& has slight diHerence etween (&& = 56&& e.g. (&&Z. Chec) S@CC7 utili?ation and add S@CC7 if needed. -. Change T/ or change S@CC7 allocation on T/A with good !uality ased on #@ 5(+. . Chec) T/A alarm mostly