3 g drive test

Radio Network Initial Tuning for WCDMA
Preparations Parameter
Audit
Commercial
Launch
Drive Testing &
Post
Processing
Change
Verification
& Reporting
Analysis &
Change
Proposals

Tools For Drive Test and Analysis
 TEMS Investigation, Nemo, Probe for WCDMA
(Software)
 Scanner (Software + HW)
 External GPS
 User Equipment (UE)
 MCOM3g/Mapinfo/Actix
 MS Access/Excel based tools

Serving/Active Set + Neighbors

Layer 3 Messages
Layer 3 Messages are the messages on the Uu interface i.e between Mobile station
and the Node B.

WCDMA HSPA/GSM Data Line
Chart

GSM Neighbors
This window is very helpful in case of 2G – 3G Handovers as we can see all
the 2G neighbors of that particular 3G cell in the compressed mode state.

 Cell I.D – This is the identity or name given to
a particular Node B and its cell by the
operator.
 UARFCN – It is the frequency band allotted to
the operator. One spectrum bandwidth is of
5MHz in WCDMA or 3G.This window shows
us the centre frequency of the bandwidth
allotted to the operator.

 Cell Name – It is the name given to particular
Node B’s by the operator generally along the
lines of the name of the area the Node B is
located in.
 Scrambling Code – Scrambling code is a
code assigned to a particular cell. There are
512 such codes for the network to differentiate
among different Node B’s and these codes can
be repetitive. They are of two types primary
and secondary.

 AS – This stands for Active Set. Active Set is
the set of Scrambling Code which the U.E is
currently latched on and there can be a
maximum of 3 Scrambling codes in Active Set.
 MN – MN Stands for monitored neighbor i.e.
the neighbor cell that is detected by the U.E as
a neighbor and is also defined as a neighbor in
the network. U.E will initiate a Handover onto
the monitored neighbor in case the monitored
neighbor has a stronger RSCP or EcNo than
the AS.

 DN - DN stands for Detected Neighbor and as
the name suggests it is the neighbor detected
by the UE but, is not defined in our network .
Hence, the U.E does not handover to the
detected neighbor. It can be because of
Overshooting of a site, incomplete neighbor
list or in case of a new site. It is very important
to optimize and have no DN’s as they are one
of the major reasons of Call drops in 3G.

Radio Parameters
 CPICH Ec/No – Common Pilot channel Ec/No
is the ratio of energy of the chip and the
combined power of all the signals including the
pilot itself received by the UE at that particular
point. It is a very important factor for call
quality.
 CPICH RSCP – Received Signal Code Power
is the level of the signal received by the U.E
from a particular pilot.

Radio Parameters
Radio parameters are the parameters of a Mobile
equipment –
Tx Power – As the name suggests it is the
transmitting power of a Mobile Station. Its value
can vary from
-50 to 50. The minimum the Tx power of the Mobile
station the better it is for call quality.
UTRA Carrier RSSI - It is the Received Signal
Strength Indicator of the Mobile Station or the
U.E. It tells us the total Power Received by the
Mobile Station from all the Pilots including itself at
that particular location.

Radio Parameters
 SIR – It is the signal to interference Ratio is
the ratio of Energy in the DPCC(Dedicated
Physical Control Channel) to that of the
interference and noise received by the U.E.
 Target SIR – It is the target Signal to
Interference ratio that Mobile Equipment is
supposed to achieve by increasing or
decreasing its power. It is set by the use of
Power Control procedure.

Radio Parameters
 SQI - It is the speech Quality Index which is a
parameter to rate the voice Quality on that
particular call. It ranges from 0 – 30 with 30
being the best quality.
 RRC State – It tells the current state and
channel as in Idle or dedicated.
 Mode – It is the mode that we are using GSM
or WCDMA.

HSPA/GSM Line Chart
 This window gives us the data speed for both
3G and 2G modes depending on which mode
the mobile equipment is.
 RLC DL Throughput – This is the total
throughput on the downlink at that particular
point.
 The speed shown in this window as
throughput is in Kilobits/sec.

Handovers
In UMTS there are the following type of Handovers-
Intra Frequency Handovers-
 Softer Handover – The HO’s that take place
between any sectors of the same node B come
under this category.
 Soft Handover – The HO’s that take place
between different Node Bs running on same
frequency are called soft HOs.
Inter Frequency Handover-
 Hard Handover – The HO’s that take place
between Node Bs running on different
frequencies. HOs from 2G-3G fall under this
category.

Active Set Update
 In 3G there can be 6 pilots in the active set. But, we
generally set it at maximum of three(depends on the
operator) to avoid Pilot pollution. In case of soft
Handover all the cells which are in MN can be entered
into Active set but, only till the maximum limit of three.
This procedure of soft HO from monitored to Active set
is called Active set update.

Active Set Update(Soft HO)
Monitored Neighbor
Current Location

Active Set Update(Soft HO)
Current Location
Added to Active Set
Active Set
Update

Pilot Pollution
 The Cells with which the UE is communicating form
the UE’s Active Set
 This Active Set is made typically of 3 cells/pilot signals
 Any Pilot which is not a member of a UE’s Active Set
and exceeds a certain threshold (typ. Ec/Io>-15dB) is
considered a Polluter
 Pilot Pollution is a common WCDMA issue that needs
to be sorted immediately.
 Pilot pollution should not be confused with poor
coverage, where there is poor coverage, there is
generally pilot pollution/bad Ec/Io.

Pilot Pollution
There are various means of reducing pilot pollution
▪New Sites: Additional sites may reduce pilot pollution by bringing dominance to an area
(before optimizing for pilot pollution, always check that a new site is not about to be
brought on air in the locality)
▪Antenna Down tilts: By adjusting tilts on the best servers, or worst interferers, pilot
pollution can be removed.
▪Azimuth Change: Azimuth can be adjusted to other direction after discussing with RF
Planning Team.
▪Reduce Power: Power of overshooting cell ( Pilot Polluter ) can be reduced but it is last
step to reduce coverage but in day to day optimization its not much recommended.

Case 1: Drop due to missing
neighbor
Problem: Detected Nighbor (DN)
 UE sends a Measurement Report that contains an
event1a means adding a new RL (cell) to Active Set
 If the reported cell is not in the current neighbor cell list
and the reported Ec/No is better than the best serving
cell Ec/No in AS by some dBs (set by a RNC
parameter)
 If for any reason the new cell can not be added to AS,
call will be released

Case 1: Drop due to missing neighbor
“DN” cell better than the serving cell
DL BLER gets worse
“DN” cell better than the serving cell
DL BLER gets worse

Case 2: Drop due to Poor Coverage
(low RSCP)
Problem: Poor DL coverage
When UE gets to an area with low RSCP ( < -105 dBm)
regardless Ec/No values there is high risk for drop.
UE will likely ramp up the transmitted power and reach its
max power. The DL BLER will probably increase and SIR
target cannot maintain anymore, finally the call drops.

Case 2: Drop due to DL Poor
Coverage
Very bad RSCP
UE max Tx power
and
high DL BLER
Very bad RSCP
UE max Tx power
and
high DL BLER

Drive Test Route with Drop Calls:
Cluster 1
30

Quality Comparison
(Long Call) (Scanner)
EcNo of UE dedicated mode is quite low in many areas, main reasons are missing neighbors
and overshooting, all cases are discussed later.

Coverage Comparison
(Long Call) (Scanner)RSCP of UE dedicated mode is quite low in many areas, main reasons are missing. All cases
are discussed later.

Best SC Comparison
(Long Call) (Scanner)Scrambling code of UE dedicated mode and Scanner:

Quality Check Comparison
(Long Call) (Scanner)Quality Check of UE dedicated mode and Scanner:

DXB2314-7 (SC -91)Down tilt from 4 degree to 7 degree

DXB2314-8 (SC -92)Down tilt from 4 degree to 7 degree

DXB2309-7
Down tilt from 4 degree to 7 degree

DXB2309-9

DXB2802-8

DXB2802-9

DXB2307-7

DXB2308-7
Down tilt from 4 degree to 7 degrees. High Call Drop Cell.

DXB2308-8
Down tilt from 4 degree to 7 degree. High Call Drop Cell.

DXB2765-7

DXB2765-8

DXB2307-8

DXB2766-7

DXB2766-8
Down tilt from 4 degree to 6 degree.

DXB2766-9

DXB2420-7

DXB2420-8

DXB2420-9

DXB2425-7

DXB2425-8

DXB2425-9

Down tilt Recommendations for Overshooting Cells
Cell Name Current E-Tilt Proposed E-Tilt
DXB23147 4 7
DXB23148 4 7
DXB23097 4 7
DXB23099 4 7
DXB28028 4 6
DXB28029 4 6
DXB23077 4 5
DXB23087 4 7
DXB23088 4 7
DXB27657 4 6
57
Cell Name Current E-Tilt
Proposed E-
Tilt
DXB27658 4 6
DXB23078 4 7
DXB27667 4 7
DXB27668 4 6
DXB27669 4 7
DXB24207 4 6
DXB24208 4 6
DXB24209 4 6
DXB24257 4 6
DXB24258 4 6
DXB24259 4 6

Missing Neighbors
59
SRNC SCELL SPSC NRNC NCELL NPSC
1 31263 442 1 31323 501
1 31263 442 1 31311 496
231 23147 91 1 31261 440
231 23148 92 1 31311 496
231 23148 92 1 31102 41
231 23148 93 1 31102 41

Missing Neighbors
60
231 23088 185 1 48011 11
231 23089 186 1 48011 11
231 27658 353 1 48011 11
231 27657 352 1 48011 11
231 27477 27 1 48011 11
231 23088 185 231 27657 353
231 27657 352 1 48013 13
231 23087 184 231 27657 352
231 23077 405 231 27477 27
231 23077 405 231 23089 186
231 23078 404 231 27658 353

Missing Neighbor
61
231 28598 36 1 32342 100
1 31673 306 231 28598 36
1 31591 288 231 28598 36
1 31592 289 231 28598 36

Missing Neighbor
62
231 23097 459 1 34071 291
231 23099 461 1 34071 291
1 31362 145 231 23099 461
231 24207 115 1 40082 476
231 24208 116 1 40082 476
231 24208 116 1 33341 299
231 24207 115 1 33322 260
231 24207 115 1 33323 261

Neighbor Addition
SCELL SPSC NCELL NPSC
31263 442 31323 501
31263 442 31311 496
23147 91 31261 440
23148 92 31311 496
23148 92 31102 41
23148 93 31102 41
23088 185 48011 11
23089 186 48011 11
27658 353 48011 11
27657 352 48011 11
27477 27 48011 11
23088 185 27657 353
27657 352 48013 13
23087 184 27657 352
23077 405 27477 27
23077 405 23089 186
23078 404 27658 353
63
SCELL SPSC NCELL NPSC
28598 36 32342 100
31673 306 28598 36
31591 288 28598 36
31592 289 28598 36
27668 425 34762 172
27668 425 48011 11
30152 265 23077 405
23097 459 34071 291
23099 461 34071 291
31362 145 23099 461
24207 115 40082 476
24208 116 40082 476
24208 116 33341 299
24207 115 33322 260
24207 115 33323 261
40081 475 24258 505
33351 208 24259 506
Following Neighbors are found missing from Drive Test Analysis :

65
5 Sec Before Drop Call
5 Sec After Drop Call
Line Chart
RSCP(A,N,D)
EcIo (A,N,D)
Best SC
UE TXPO, SIR, BLER

Drop Call#1
Observations & Recommendations
•Call was dropped on Nokia site DXB2061 overshooting from 2.8km and there are missing NHBRs in the vicinity i.e.
DXB20617 and DXB 21357.
•Also Nokia site DXB2125 is down.
DXB23147 needs to be down-tilted from 4 to 6.

67
Drop Call#2 (Dropped, Coverage hole)
•This drop happened in Nokia cluster where there are no
sites in the vicinity.
•It’s a coverage hole and future site DXB2606 will
improve the situation.
During Drop CallLine Chart
RSCP(A,N,D)
EcIo (A,N,D)
Best SC
UE TXPO, SIR, BLER
RSC
P EcIo

Drop Call#4 (Dropped on Nokia, re-Established on Nokia)
5 Sec Before Drop Call 5 Sec After Drop Call5 Sec Before Drop Call
5 Sec After Drop Call
•Missing Neighbor DXB40082 and DXB24257.
RSCP(A,N,D)
EcIo (A,N,D)
Best SC
UE TXPO, SIR, BLER

3 g drive test

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