TYPICAL RADIO PROBLEMS AND THIER OPTIMIZATION Posted on April 30, 2013 by TELNETWORK TYPICAL RADIO PROBLEMS Several sources of information for optimization: QoS indicators, Coverage predictions, Customer complaints,, Drive tests, Abis/A traces, Other teams information (SS statistics!" complaints
I. Coverage Problem Bad coverage : A net#or$ facing coverage problems has bad %&'ev" %&Qual can be bad at the same time" Sometimes the %&'ev can loo$ O on the street (i"e" from drivetest! but coverage inside the buildings can be poor due to building losses" )uilding losses can range from *+ to + d) or more"
Indication : - Customers complain about dropped calls and/or .o et#or$
- O0C QoS indicators 1 2C3 failure rate 1 Call drop rate 1 'o# proportion of better cell 3O 1 3igh rate of D' 4 5' 'evel 3O (possibl6 also D'/5' 7ualit6 3O! - A interface indicators 1 3igh rate of Clear %e7uest message, cause radio interface failure - Drive 2est 1 8oor %&'ev ( 9 ;< d)m! =nvestigation and Optimization : - =f actual coverage O compared to predicted ones 1 =mprove coverage b6 adding 0acro site, 0icrocell site ()order or Shado# areas!, or =)C site (=n building coverage!" 1 5se parameter setting e&" )ila6er 3andover"
- =f actual coverage is not the one predicted b6 planning tool 1 Chec$ antenna s6stem (azimuth, crossed sector>! 1 Chec$ prediction in the tool (?=%8, Clutter 26pe, Obstructing building>!" 0ost of the time the prediction #ill be incorrect, as it is onl6 a computer simulation 1 =ncrease or decrease antenna do#ntilt 1 Chec$ )2S output po#er set in the O0C% ()S@28B%@0A: should al#a6s be set at +! rom Drive test or Abis =nterface 1 %&'ev 9 ;< d)m and 1 %&Qual E II. Inter!erence Problem =nterference:
A net#or$ facing interferences problems presents good %&'ev and bad %&Qual in the same time on some areas" Indication: - Customers complain about bad speech 7ualit6 (nois6 calls! and/or call drops
- O0C QoS indicators 1 SDCC3/2C3 Drop 1 'o# proportion of better cell 3O 1 3igh rate of D'/5' 7ualit6 3O and interference 3O 1 'o# 3O success rate - A interface indicators 1 3igh rate of Clear %e7uest message, cause radio interface failure - Drive 2est
1 %&Qual E #ith %&'ev F< d)m 26pical causes: - GS0 interferences: Cochannel, adHacent" - on GS0 =nterference: Other 0obile et#or$, Other % sources" Cochannel interference: - C/= I Carriertointerference ratio - J*K d) is ta$en into account for Alcatel ( J; d) according to GS0 standard! (i"e" interference can be ; ◊ *K d) #ea$er than serving cell to cause poor %&Qual!" - =ndications: Do#nlin$ and/or 5plin$ =nterference, 3igh rate of 7ualit6 handover, call drop, and call setup failure" - =nvestigation: Drive test anal6sis, 'umpini: Cochannel chec$ing, Chec$ prediction to verif6 #hich cell could be causing the interference, re7uenc6 plan C/= 9 *K d)" - Optimization: Antenna optimization, Change fre7uenc6, %educe )2S po#er (not an option in 2A Orange net#or$!, Concentric cell" Ad"acent c#annel inter!erence: - C/A I CarriertoadHacent ratio
- L d) is ta$en into account for Alcatel ( ; d) according to GS0 standard!" - =ndications : Do#nlin$ and/or 5plin$ =nterference, 3igh rate of 7ualit6 handover, call drop, and call failure - =nvestigation: AdHacent 3O statistics (if the6 are deMned as neighbors!" =f the6 often handover, then adHacent channel interference could be a problem" Drive test anal6sis N 'umpini: AdHacent channel chec$ing N Cell coverage predictionN re7uenc6 plan C/= 9 L d)" - Optimization : Antenna optimization, Change fre7uenc6, %educe )2S po#er (not an option in 2A Orange net#or$!, use Concentric cell $on %SM inter!erence : - Other mobile net#or$ : =ntermodulation #ith GS0 )2S/0S receiver
- Other % interferers
1 %adar 1 Shop antitheft mechanism 1 0edical devices 1 Other manmade radio transmission 1 =llegal usage of GS0 fre7uencies (e"g" illegal imported devices, illegal usage of other organization, ! III. &nbalance 'o(er b)dget Problem 1 A cell facing unbalanced po#er budget problems presents a too high pathloss diPerence bet#een 5' and D' (often D'5'!
1 'o#er %& diversit6 gain of cross polarized antenna in rural area compared to dense area 1 Crossed feeders 1 2rac not directl6 in boresight of antenna, #here crosspolar discrimination is lo#er 1 'oose connectors 1 ault6 antenna, feeder, 20A 1 %ule : tr6 to have delta as small as possible to avoid access net#or$ possible onl6 in * direction (usuall6 )2S0S : O and 0S)2S : O!, i"e" uplin$ limited Indicator: - O0C QoS indicators
1 3igh ratio of 5plin$ level 3andover cause 1 'o# incoming 3O success rate 1 D' level loo$s O for 3O, but 5' is too #ea$ #hen 3O is attempted 1 Degradation of 2C3 failures and OC call drop indicators - A interface indicators 1 3igh rate of Clear %e7uest message, cause radio interface failure
- O40 Alarms 1 Roltage Standing Bave %atio (RSB%! 1 20A Invetigation : 1 Abis monitoring: A)S(delta 8ath loss! *+Chec$ if problem is occurring for * 2% or all"
1 A)S(delta path loss! I A)S(5' 8ath loss 1 D' 8ath loss! 1 5' 8ath loss I 0S transmitted po#er 1 measured received 5' level 1 D' 8ath loss I )2S transmitted po#er 1 combiner loss 1 measured received D' level 1 'arge diPerence bet#een uplin$ and do#nlin$ level triggered 3O" 1 5se 80 observation counter (in O0C%! 1 %2** O'timi*ation : T#i e+)i'ment #o)ld be c#ec,ed 1 2% t6pes (08, 38!
1 Antennas or common % components, 20A (common to all 2% of the )2S! 1 2% % cables, 'A I-. TC congetion Problem TC Congetion : - 2C3 Congestion rate (2C3 Assignment 8hase! is too high (more than K!
- %ule : tr6 to meet the oPered trac (as$ed b6 users! b6 providing the right number of resources (2% e&tension! Indication: 1 Customers complain about .et#or$ bus6
1 O0C QoS indicators: 3igh .2C3 Congestion rate, .%2C3 Assignment failCongestion, 'o# .incoming =ntra/=nter )SC 3O success rate (no 2C3 available!, 3igh .Directed %etr6 rate or Congestion %elief (0otorola! if activated, A interface indicators: .)SS Congestion failure in OC(3igh rate of Assignment ailure message, o radio resource available! 1 Drive 2est : 3andover to better cell is slo#, or never occurs
O'timi*ation: 1 Special events :
oreseeable: (footballs match, important meeting, ?&hibition, etc!: Add some e&tra 2%s, Add special mobile )2Ss (Cell on Bheel!, Activate 3% (ma6 not al#a6s be possible due to )SC capacit6 limitations! ot foreseeable: car crash on the high#a6 1 Dail6 periodic problems : At bus6 hour: 3ard#are solution: Add 2%(s!, concentric cell, ne# site, Optimize cell boundaries (i"e" antenna optimization! to share trac #ith surrounding cells" Soft#are solution: Directed %etr6, 2rac 3andover, 3alf %ate (Alcatel!, Congestion %elief (0otorola! lo# control (0otorola!" 8roblems and responsible parties - Coverage problem : =f the measured %&'ev does not match the prediction: 1 Chec$ the prediction, chec$ panoramic pictures for obstructions 1 ield Operation team to chec$ ph6sical conMguration (tilt, azimuth, antenna height!" Also chec$ for faults in the antenna s6stem (RSB%, s#eep antennas, D2 test, etc"! 1 =f ield Operation Mnd no problem, antenna optimization ma6 be re7uired (if necessar6! =f the Meld realities match the prediction: % team to add ne# sites (trisector, micro cellular, indoor cells! to improve poor/no coverage area (Optimizer re7uests for some ne# sites to % team regarding to the drive test result!" - =nterference problem : Optimization team to identif6 the interference source and re7uest Spectrum 0anagement team to correct it in case of internal source (ne# fre7uenc6 planning! - 5nbalanced po#er budget problem : ield Operation team to chec$ the impacted )2S (Antenna, 20A, % cables, 'A, diversit6 s6stem! according to re7uest from Optimizer"
- 2C3 Congestion problem : %egional % to re7uest 2% e&pansion"
