Your Birthpath or Destiny number, derived from your date of birth, is the single most influential number of the numeroscope. It symbolizes your characteristic approach to life and describes those v...
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What is CPT or Call Path Trace by Dr. Hatem MOKHTARI • These are BSS statistics showing the performance of a cell in terms of : • Link Balance : DL Path Loss – UL Path Loss • Distribution of DL RXQUAL/RXLEV samples • Distribution of Timing Advance • Drive Tests alone cannot help assess all the problems especially UL performance • It is important to compare DL AND UL : • RF Losses in view of detecting HW Problems such as TRX, TMA, cables, etc • Quality and Level to assess accurately which link is defficient and correct it • Timing Advance stats will help understand Ping-Pong HO and the extent of a cell and compare it according to marketing
Signal strength (SS) and quality measurements principles BSC DL SS DL Qual
DL SS(1) DL SS(2) . . DL SS(6)
UL SS UL Qual
Σ
neighbours
Number of defined neighbours
Number of measurements per neighbour
32
20
16
10
3
5
6
10
Fo r all rep orted n eigh b our cells n
No D iscard n
M in im u m sign al stregth criterio n fu lfilled ? D iscard n Y es No
R an kin g acco rd in g to P o w er B u d get?
No
S tro n ger th an servin g cell + h o M argin L ev/Q u al?
Y es
No D iscard n
Y es
P o w er b u d get evalu ation > h oM argin PB G T ?
Y es
No
L oad < Load th resh old?
Y es R ed uce rank in g accordin g to h oLoad Factor
K eep ran kin g accord ing to h oP riorityLev el
R an k accordin g to signal stren gth w ith in ow n p riority level R an k accordin g to signal stren gth w ith in red uced p riority level
H andover can did ate list
Definition of Link Balance • Link Balance equation is given by :
∆(dB) = DLPL − ULPL
Where DLPL is : DLPL = EIRP( BTS ) − Sensitivity ( MS ) • EIRP(BTS) : EIRP( BTS ) = Pout ( BTS ) + Gant ( BTS ) − LCCC • Sensitivity(MS) = Sstatic(MS) + Lccc(=0) – Gant(MS) – DiversityGain(=0) • And the DLPL : ULPL = EIRP( MS ) − Sensitivity ( BTS ) • EIRP(MS) : EIRP( MS ) = Pout ( MS ) + Gant ( MS ) − LCCC (= 0) • Sensitivity(BTS) = Sstatic(BTS) + Lccc – Gant(BTS) – DiversityGain
∆ (dB) = Pout ( BTS ) − Pout ( MS ) + S static ( BTS ) − S static ( MS ) − DiversityGain
Link Balance (self-test) • Compute the Link Balance ∆(dB) using the following assumptions : • • • • •
BTS : Sstatic = -110 dBm Pout = 20 W Cable losses = 2.5 dB Antenna Gain = 18 dBi XPOL Diversity Gain = 3 dB
• • •
MS : Sstatic = -100 dBm Pout = 1 W Antenna Gain = 0 dBi
• In case where no diversity is involved, what solution do you propose to keep the path balanced?
Uplink and Downlink Quality Samples Are balanced => no Quality problem seemingly !
Most of the calls are Completed at about 1.5 km !
High amount of Low level samples : Coverage problem in a high traffic area Few calls made at the vicinity of the cell With high DL Level because UL is Power-controlled
Mean Link Balance Centered around 2.5 dB
Call Path Trace (Self-Test) • Given the Histograms in the figure below what problems do we have and how can we solve them? Do we need additional data to solve the problem?
Worst Cell List • This is the list of the cells for which have two major concerns : – Substantial Amount of Traffic – Bad Quality Performance
• The Worst cells are ranked based upon : – Carried Traffic – Percentage of HO causes due to : • DL/UL Quality • DL/UL Level • Power Budget
• Good cell statistical performance would lie within the following : – % of HO due Power Budget : > 80 % – % of HO due to DL/UL Quality and/or DL/UL Level : within 20 %
HO Causes • High % of HO Causes due to Quality : – DL => Generally CCI and/or ACI – UL => Generally a Hardware Problem : • TMA (if any) alarms • BTS RX problem (check TRX) • Double check with CPT the Link balance
• High % of HO causes due to Level – DL => • Due to terrain and lack of best servers • Hardware problem : check the connectors, PA, Antenna connections, etc.
– UL => • Due to TMA (if any) Problem • Due to Hardware Problem
Worst Cell List (an example)
WCL Self-Test • Given the WCL Chart in the figure below, analyse the 10 Worst Cells and especially for which reason this ranking is done ? – What kind of action do you propose for each cell given the comments supplied ? – Cell with CI = 46623 has a coverage problem, what indication explains this ? – What do you propose to remove the cell with CI = 46623 from this list ? – Cell with CI = 46462 has a PBGT HO cause about 60% and about 40% combination of DL Qual and DL Level • Why this cell is ranked 10 instead of 2 or 3 for example ? • Does this cell need a frequency retune ?
