Let's add the missing neighbor to the neighbor list. This will allow the UE to add the strong neighbor cell to its active set and maintain the call quality.

1. Radio Network Tuning and
Optimization for Universal
Mobile Telecommunications
System (UMTS)
Osama Bilal
Thesis Worker
Ericsson Finland
1

2. Radio Network Tunning and Optimization for
UMTS
Author: Osama Bilal
Supervisor: Prof. Sven-Gustav Häggman
Instructor: B.Sc. Jukka Möykkynen
Carried out for Ericsson Finland
Tuning Activity for a UMTS Operator
2

3. AGENDA
• Motivation
• 2G-3G, What is different
• Tuning Process Flow
• Tools used for Tuning Activity
• Equipments Configuration
• Pilot Tuning
• UE Tuning
• Final Words
3

4. MOTIVATION
• 3G networks are becoming commercially available all over
the world
• To check the functionality of the networks before
commercial launch
• Network designs are based on propagations models and
simulations (coverage verification)
• 3G technology (WCDMA) is different from 2G
• Tools and methods for 3G Networks
4

5. Differences compared to 2G
• In General
- The Technology is more complicated (Overlapping cells,
soft hand over, power control, cell breathing etc)
- High performance requirements on products (UE & Network
nodes)
- In Particular for Tuning & Optimzation
- Process & tools are under development
- Co-located GSM/3G sites
- Shared Antenna System
- Inter-working with GSM
5

6. Tuning or Optimization, What is the difference
• During Tuning
No traffic in the network, No subscribers
Network tuned only based on drive test data
Labour intensive with repeated drive test
All is about Pre-launch activities
• During Optimization
Commercial traffic, subscribers using the network
Statistics used widely to monitor network performance
Drive testing just in case
All is about Post–launch activities
6

7. Tuning Process Flow
Radio Network Initial Tuning for WCDMA
Drive Testing & Analysis & Change
Preparations Parameter
Post Change Verification
Audit
Processing Proposals & Reporting
Commercial
Launch
7

8. Tuning Process Flowchart
8

9. Tools For Tuning/Optimization & Data Post
Processing
Active measurement needed due to lack of statistics
• TEMS Investigation for WCDMA (Software)
• TEMS Scanner (Software + HW)
• External GPS
• User Equipment (UE)
• TEMS DeskCat for post processing
• MCOM3g/Mapinfo
• MS Access/Excel based tools
9

10. Drive test tools configuration
Drive Test Equipments for Voice, CS64 & PS call
Short call Long Call
CS64 PS
USB1 USB2
USB1
USB1
GPS
Com 1
scanner
10

11. Drive Test Routes
11

12. PILOT TUNING
The basic measurements of scanner are
• CPICH_RSCP (received signal code power)
• CPICH_Ec/No (received energy per chip divided by the
power density in the band)
• RSSI (received signal strength indicator)
What can you achieve with scanner?
• Crossed feeder issues (DL)
• Coverage verification
• Interference problems (overshooting cell, pilot pollution)
• Missing neighbours
12

13. COVERAGE VERIFICATION - Primary Common
Pilot Channel
Verify P-CPICH detection to minimize coverage holes
• P-CPICH RSCP
• P-CPICH Ec/No
Coverage level RSCP [dBm] Ec/N0 [dB]
Sufficient RSCP ≥ −100 Ec/N0 ≥ −14
Poor −115 ≤ RSCP <−100 −16 ≤ Ec/N0 < −14
No coverage RSCP < −115 Ec/N0 <−16
13

14. Best Server Signal Strength (RSCP)
• Yellow is
good
• Blue can
generate
problems
• Grey is bad
14

15. Pilot Ec/No Measurements
• Green is
good
• Blue can
generate
problems
• Orange is
bad
15

16. INTERFERNECE
By correlating low Ec/No with high RSCP, areas with high
interference can be detected
-30
-40
-50
-60
RSCP [dBm]
High interference
-70
-80
-90
-100
-25 -20 -15 -10 -5 0 5
Ec/Io [dB]
16

17. INTERFERENCE (RSCP > -90 dBm AND Ec/No < -9 dB)
17

18. Primary Common Pilot Channel (P-CPICH) –
OVERSHOOTING
18

19. OVERSHOOTING
Change Proposal: Site-D, Sector-1, Antenna Down-tilt 8 Degrees
19

20. Primary Common Pilot Channel (P-CPICH) –
PILOT POLLUTION
High CPICH reception levels from many • P-CPICH RSCP
Cells, (more than MAX_ACTIVE_SET) • P-CPICH Ec/No
Ec E c
Pilot count ( ≥ − threshold ) > AS size
N 0 N 0 serving
20

21. PILOT POLLUTION
21

22. PILOT POLLUTION
22

23. PILOT POLLUTION
Change Proposals
Proposed
Height of Antenna
Site Sector SC of Antenna
Antenna Tilts
Name Number Pilot Tilts
(meters) (degree)
(degree)
A 1 173 38 2 5
A 2 76 38 2 4
1
D 485 47.3 2 8
C 2 24 39.2 3 5
B 3 79 27 2 3
23

24. PILOT POLLUTION
35
30
25
Numbers of 20
Samples 15
10
5 Verification Drive Test (after tuning)
0
173 76 485 79 24
40
SC of Pilots
35
30
Initial Drive Test (before tuning) 25
Number of
20
Samples
15
10
5
0
173 76 79 24
SC of Pilots
24

25. UE TUNING
• Voice /Video/PS calls
– Long calls
– short calls
• Identify problem areas
– Blocked calls
– Dropped calls
– Delay/Throughput
25

26. Short Calls Analysis
Set-up a call and maintain it for a pre-defined time duration
(for 15-60 s)
Call set-up failure and drops during short calls can be mainly
used to analysis Accessibility failure due to:
• UE Failure
• Unsuitable Parameters Setting
• Coverage Problem
• Interference
• Others
26

27. Long Calls Analysis
Set-up a call and maintain it until it is drop (used for
the analysis of Retainability performace)
Drops during long call can be used to identify:
• Missing Neighbor Relation
• Coverage Problem
• UE Problems
• Network Characteristics
• Best Parameter Setting
• Others
27

28. KEY PERFORMANCE INDICATORS
• Accessability (Call set-up success rate)
• Retainability (Dropped calls)
• Mobility (Handover success rate)
• Integrity (BLER and throughput)
28

29. 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
29

30. Case 1: Drop due to missing neighbor
DL BLER gets worse
“DN” cell better than the serving cell
30

31. 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.
31

32. Case 2: Drop due to DL Poor Coverage
UE max Tx power
and
high DL BLER
Very bad RSCP
32

33. Case 3:
PS: Session Error due to Poor DL Coverage
UE enters a very low coverage area (RSCP < – 105 dBm).
The packet connection is carried on a 64/64 DCH Channel
as consequence of the low coverage conditions.
The UE will likely ramp up its power to the maximum, goes
to Idle Mode and the Application and RLC throughputs go
to zero.
At this point the RAS application will start the Session
Timeout timer, if the throughput is not resumed the Session
Error event is triggered with cause “session timeout”.
33

34. PS: Session Error due to Poor DL Coverage
App throughput ~64kbps
Very low RSCP
34

35. FINAL WORDS
• For network tuning, we need to relay on field measurements which
require extensive drive tests
• Finding the best possible configuration for antenna heights, tilts,
azimuths and parameter setting for all the present cells/sectors in the
network and also for any new sites that might be needed to improve
coverage
• Power adjustment can also be used for network tuning but can become
complicated and result in poor network performance
• Use of Remote Electrical Tilt (RET) Antenna is preferred over mechanical
tilt antenna
• Neighbour definition is of prime importance in UMTS network (Soft
handover gain and interference reduction). Keep neighbour list upto 20.
• Automated tools are needed that could suggest the best possible
neighbour relations, antenna heights and tilts by using both the field
measurements and the propagation models & simulations
• Skilled people, right methods and advanced tools are needed to perform
3G tuning and optimisation
35

36. Comparison of Mechanical and Electrical Down-tilts
36