Based on the new convention of Cell Congestion KPI Method, a cell could be considered as a congested cell if the cell fulfilled the congestion factor. There are two factors that contribute the congested cell verdict, i.e.:
1) The status of cell congestion based on daily cell utilization
Average_Cell_Traffic
Average_Cell_Traffic = 
Remarks:
- For Daily Report or daily cell utilization, the granularity period = 24 hours
- For Weekly Report or weekly cell utilization, the granularity period = 24 * 7 hours
- For Monthly Report or monthly cell utilization, the granularity period =
24 * 7 * number of days in appropriate month
Cell Utilization
For Full Rate:
Or
For Half Rate:
Or
E.g. Table Erlang with GOS 2% of FR TCH
|
TRX |
TCH |
Erlang |
|
1 |
6 |
2.28 |
|
2 |
12 |
6.61 |
|
3 |
19 |
12.33 |
|
4 |
26 |
18.38 |
|
5 |
33 |
24.63 |
|
6 |
40 |
31.00 |
|
7 |
48 |
38.39 |
|
8 |
55 |
44.94 |
|
9 |
63 |
52.48 |
|
10 |
71 |
60.08 |
|
11 |
79 |
67.73 |
|
12 |
87 |
75.42 |
Example based on TCH Full Rate:
Cell A has two TRXs and implemented in Full Rate. The total traffic in one day is 11.19 Erl
So the cell utilization for cell A on that day is:
= 7.054% (Assumption the measurement period = 24 hours)
Note:
The granularity period is not always 24 hours, it depends on the measurement period
Based on the new convention of Cell Decongestion KPI Method, if the cell utilization in one day is more than 60% (for Java Area) or 70% (for outside Java), it could be considered that the utilization of that cell is Congested Utilization. Due to the calculation, it could be concluded, the utilization of Cell A on that day is Normal Utilization.
2) The status of cell congestion based on peak hourly utilization
Hourly cell utilization could be calculated from the hourly traffic volume.
For example (based on TCH Full Rate):
Traffic Cell A (same cell with the above sample) on 12 PM – 01 AM = 0.82 Erl
So the hourly utilization for cell A on that time is:
= 12.42%
And so forth for the next every hour (every hour has utilization; Erlang per hour could be seen on Metrica data sheet hourly_traffic)
If in one day, there are 2 (or more) peaks hourly utilization (> 100%); it could be categorized as Peak Congestion. But if in one day there is no peak or only one peak hourly utilization (>100%), it could be categorized as Normal Congestion.
The Congested Cell Final Conclusion:
A cell could be categorized as a CONGESTED CELL, if in two weeks period, there are 6 days (non consecutive) occurred when the cell stated as congested utilization based on daily cell utilization AND stated as Peak Congestion based on hourly utilization.
And for the calculation of congested cells percentage in one region is:
The calculation for TCH Half Rate is same with the calculation for TCH Full Rate.
TCH Available
Total number of TCH available will be used in calculation of cell utilization, but first, it converted to Erlang Table GOS 2%
The TCH available general formula could be calculated as follows:
1. For TCH Full Rate:
2. For TCH Half Rate:
For Half Rate, TCH Available depends on the Vendor Half Rate Specification.
2.1 For Nokia:
For Dual Rate:
The dual rate could be activated per Time Slot (TS), 1 TS dual rate = 2 TCH.
Example Nokia Dual Rate, TCH Available Calculation:
Cell B activated as dual rate and has Configuration 2 TRXs. So the TCH Available is:
Full Rate:
TCH Available = (2 * 8 TS) – (1 TS for BCCH + 1 TS for SDCCH + 2 TS for Dedicated PDCH)
= 12 TCH
Half Rate:
TCH Available = (2 * 8 TS) – (1 TS for BCCH + 1 TS for SDCCH + 4 TS for Dedicated PDCH)
= 10 TS Total
= 8 TS FR + 2 TS DR (the time slot sharing could be seen in the table below)
= 8 TCH FR + 4 TCH DR
= 12 TCH
Because the logical channel configuration could be different, thus the total number of TCH for Full Rate could be same with the total number of TCH for Half Rate.
|
Full Rate Configuration 2 TRX |
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TS1 |
TS2 |
TS3 |
TS4 |
TS5 |
TS6 |
TS7 |
TS8 |
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|
TRX1 |
BCCH |
SDC |
PDC dedicated |
PDC dedicated |
TCH/F |
TCH/F |
TCH/F |
TCH/F |
= 4 TCH |
|
TRX2 |
TCH/F |
TCH/F |
TCH/F |
TCH/F |
TCH/F |
TCH/F |
TCH/F |
TCH/F |
= 8 TCH |
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Half Rate Configuration 2 TRX |
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|
TS1 |
TS2 |
TS3 |
TS4 |
TS5 |
TS6 |
TS7 |
TS8 |
|
|
TRX1 |
BCCH |
SDC |
PDC dedicated |
PDC dedicated |
PDC dedicated |
PDC dedicated |
DR |
DR |
= 4 TCH |
|
TRX2 |
TCH/F |
TCH/F |
TCH/F |
TCH/F |
TCH/F |
TCH/F |
TCH/F |
TCH/F |
= 8 TCH |
2.2 For Alcatel
d. For Siemens
For TCH Available total could be seen in Metrica (Data Sheet Daily Analysis)
TCH Available total = TCH_FR + TCH_HR
d. For Ericsson & Huawei
The Data already provided by Vendor
