3G Optimization Interview Topics
1. Important
parts of Benchmarking Report
a. RSCP
Coverage
b. Ec/Io
Coverage
c. CSSR
d. DCR
e. Retainability
f. Handover
(Mobility)
g. Call
Setup Time
h. ASU
Type
i. 3G-2G
Serving percentage
j. IRAT
Handover
k. BLER
and Quality statistics
2. UMTS
Channels
a. CPICH
b. SCH
c. AICH
d. BCH
– BCCH
e. FACH
– CCCH
f. RACH
– CCCH
g. DCH
– DCCH
3. HSDPA
Channels
a. HS-DPCCH
(uplink signaling)
b. HS-SCCH
(downlink signaling)
c. HS-PDSCH
or HS-DSCH (data channel)
4. HSUPA
Channels
a. E-DPDCH
b. E-DPCCH
c. E-DCH
d. E-AGCH
e. E-RGCH
f. E-HICH
5. Dropped
Call Types
a. Missing
Neighbor
b. Poor
Coverage
c. Pilot
Pollution
d. Congestion
e. Not
Radio Reasons
f. Equipment
Fault
6. Blocked
Call Types
a. Security
and Authentication Mode Failure
b. UE
Issues
c. Disconnect
on RAB Setup
d. Unavailable
Resource
e. UE
Sensitivity Fault
f. Unanswered
RRC requests
g. Barred
Network
7. Major
Network Problems
a. Poor
Coverage
b. Poor
Cell Dominance
c. Pilot
Pollution
d. Missing
Neighbors
e. Corner
Effects
8. Important
Events in PS Call
a. Attach
and Detach
b. PDP
Context Activation
c. Download
and Upload
d. Dual
Mode
9. HSDPA
Categories
a. 3.6
Mbps – Cat 5 & 6 (5 HS-DSCH Codes)
b. 7.2
Mbps – Cat 8 (10 HS-DSCH Codes)
c. 14.4
Mbps – Cat 10 (15 HS-DSCH Codes)
d. 21.1
Mbps – Cat 14 (15 HS-DSCH Codes,
MIMO and 64 QAM)
10. Number
of CE for PS 384 = 10
11. Number
of Users for PS 384 = 3
12. HSDPA
Factors
a. Number
of HSDPA Codes
b. Number
of HS-SCCH Codes
c. Max
HS-PDSCH Codes per Users
d. Algorithm
and Scheduling
e. Number
of HARQ Process
13. HSDPA
Parameters
a. HS-SCCH
Power Offset
b. Measurement
Power Offset
c. CQI
Feedback Cycle, Power Offset
d. ACK-NACK
Power Offset
e. Number
of HARQ Process
f. MAC-hs
window size
g. Tx-
Rx Window size
14. HSUPA
Parameters
a. E-DPCCH
to DPCCH Power Offset
b. Happy
Bit delay
c. E-TFCI
Power offset
d. E-AGCH
Channelization Code
e. E-AGCH
Power Offset
15. Reasons
of Low Throughput in HSDPA:
a. Poor
RF Conditions (Low CQI)
b. Frequent
Serving Cell Change (Low CQI)
c. Signaling
Delay
d. E1d
setting issues
e. TCP
segment loss outside air interface
f. TCP
Tx/Rx window setting
g. Iub
Flow Control
h. FTP
server issues
16. HSDPA
Scheduler Type
a. Max
C/I
b. Round
Robin
c. Proportional
Fair (mostly used)
17. Timers
and Counters
a. T300,
N300 (2sec) RRC Connection Retransmission
b. T312,
N312 (1 sec) “In Sync” establishment
c. T313,
N313 (5 sec) “Out of Sync” Failure
d. T314 (12 sec) Cell Update (CS)
e. T315 (180 sec) Cell Update (PS)
f. T302,
N302 (1.2 sec) Cell Update Confirm
18. Resources
for Each Call Type
a. AMR SF 128 CE 1 (UL) 1(DL)
b. VP SF 32 CE 3 (UL) 2 (DL)
c. PS
128 SF 16 CE 5 (UL) 4 (DL)
d. PS
384 SF 8 CE 10 (UL) 8 (DL)
19. Event
Thresholds
a. E1a 3dB
b. E1b 6dB
c. E2d -12dB and -101 dBm
d. E2f -10dB and -99dBm
20. NASTAR
a. Network
performance and monitoring tool
b. SQL
Based
c. Collect
data from M2000
d. Data
storage up to 3 months
e. Supports
5 RNC and 6000 Cells
21. NASTAR
Inputs:
a. RNC
performance data M2000 / BAM
b. Project
Parameters Manual
c. Configuration
Parameters M2000
d. CHR
Data M2000
/ BAM
e. Interference
data M2000 / BAM
f. Coverage
Data LMT client
g. NodeB
performance data M2000
22. NASTAR
Analysis:
a. Performance
Analysis
b. Neighbor
Cell Analysis
c. Call
Drop Analysis
d. Pilot
Pollution Analysis
e. Interference
Analysis
f. Resource
Monitoring
i. CPU
Utilization
ii. Iub
Utilization
iii. Traffic
Load
iv. Cell
Load
23. Monitoring
Levels
a. Level
1 – Statistics, Alarm Logs (M2000)
b. Level
2 – Sample tracing, CHR (M2000 and
NASTAR)
c. Level
3 – DT Data, Single UE Tracing
24. NASTAR
Performance Data:
a. RAN
Counters (KPI)
b. Call
History Records (CHR) CDR Analysis
c. System
History Records (SHR) Cell Status
d. Real-Time
User Monitor (RUM) IMSI Tracing
e. Real-Time
System Monitor (RSM) Load, Inference, etc
25. NASTAR
Counters:
a. For
calculating Call Drop Rate
b. For
calculating Handover Success Rate
26. LMT
Trace Message Levels:
a. To
or From NodeB NBAP
b. To
or From CN RANAP
c. To
or From UE RRC
27. Throughput
Types in Actix
a. Payload
L1 with CRC blocks
b. Throughput
L1 without CRC blocks
c. PDU throughput MAC/RLC Interface
d. SDU
throughput RLC/RRC Interface or
RLC/PDCP Interface
L1
Throughput > PDU Throughput >
SDU Throughput
28. Signal
Flow (R99 MO)
a. RRC
Connection Request (UL-CCH)
i. TMSI
and LAI info
ii. LAC
iii. PSC
info including Ec/Io and RSCP level
iv. Establishment
cause (CS, PS, VP)
b. RRC
Connection Setup (DL-CCH)
i. S-RNTI
ii. RLC
Mode (AM, UM, TM)
iii. Transport
Channel Type
iv. Timers
and Parameters
c. RRC
Connection Setup Complete (UL-DCCH)
i. Domain
Identity (CS or PS)
ii. Security
Parameter supported
d. Initial
Direct Transfer (UL-DCCH)
i. Notification
and Capabilities of UE
ii. Mobile
TMSI
e. Downlink
Direct Transfer (DL-DCCH)
i. RAND
Value, Authentication
f. Uplink
Direct Transfer (UL-DCCH)
i. Authentication
Response
g. Security
Mode Command (DL-DCCH)
i. Ciphering
and Integrity
h. Security
Mode Complete (UL-DCCH)
i. Response
from UE
i. Uplink
Direct Transfer (UL-DCCH)
i. Authentication
Code
j. Downlink
Direct Transfer (DL-DCCH)
i. CC
Call Proceeding
k. Radio
Bearer Setup (DL-DCCH)
i. Transport
Channel Info
l. Radio
Bearer Setup Complete (UL-DCCH)
i. Response
from UE
m. Downlink
Direct Transfer (DL-DCCH)
i. Alerting
n. Downlink
Direct Transfer (DL-DCCH)
i. CC
Connect
o. Uplink
Direct Transfer (UL-DCCH)
i. Connect
Acknowledgement
29. Load
Control
a. Load
Monitoring (LDM)
b. Load
Reshuffling (LDR)
c. Overload
Congestion Control (OCL)
30. Load
Reshuffling Actions:
a. First
Action – Code Tree Reshuffling
b. Second
Action – Inter Frequency HO
c. Third
Action – BE Service Rate reduction
d. Fourth
Action – Renegotiation of QoS real time services
31. Scanner
vs UE Data
Scanner
is used to scan all carriers and DL Scrambling codes, while UE measures only
codes of informed cells (through BCH and measurement control Neighbor List)
32. INTER
RAT Types:
a. IRAT
Handover (CS)
b. IRAT
Cell Change Order (PS)
33. Call
Flow for IRAT Handover:
a. RRC
Measurement Report UL
b. Physical
Channel Reconfiguration DL
c. Physical
Channel Reconfiguration Complete UL
d. Handover
from UTRAN Command GSM DL
e. Handover
Complete
34. Call
Flow IRAT Cell Change Order
a. RRC
Measurement Report UL
b. Physical
Channel Reconfiguration DL
c. Physical
Channel Reconfiguration Complete UL
d. Cell
Change Order from UTRAN DL
e. Immediate
Assignment DL
f. Authentication
Response UL
g. TMSI
Relocation Complete UL
35. Compressed
Mode Methods
a. SF/2 (CS, PS) Code
Compression
b. HLS (PS only) Higher Layer Scheduling
36. IRAT
HO due to Overload – event 3A
37. Physical
Channel Reconfiguration Message details
a. gsm-Carrier
RSSI Measurement
b. gsm-Initial
BSIC Identification
c. gsm-BSIC
Reconfirmation
38. Huawei
Tools :
a. Genex
U-Net (Planning
and Simulation)
b. Genex
WCDMA Probe (Drive Testing
and Logging)
c. Genex
Assistant (Post
Processing)
39. Huawei
NodeB Type
a. BTS3812 (GSM BTS
upgradable to WCDMA)
b. BTS3900
A (Macro
Indoor)
c. BTS3900
E (Macro
Outdoor)
d. BTS3900
C (Indoor
Compact – Micro)
e. DBS3900 (Distributed NodeB
with BBU and RRU)
1. The output of
coverage planning is needed for which one of the following processes?
A. Code planning.
B. Transmission
planning.
C. Propagation model
tuning.
D. Loading field
measurements.
Answer: A
2. If the cell range of
12.2 kbps voice service with 141.9 dB path loss is 2.3 km, what is the size of
the cell area with omni-directional site (k factor for site area is 2.6)?
A. 12.2 km?
B. 13.8 km?
C. 15.9 km?
D. 16.6 km?NP
Answer: B
3. Which one of the
following services has the HIGHEST processing gain?
A. 12.2 kbps AMR voice.
B. 64 kbps RT data.
C. 64 kbps NRT data.
D. 384 kbps NRT data.
Answer: A
4. Which one of the
following parameters can be measured with a UE connected measurement system but
NOT with a scanner measurement system?
A. P-CPICH Ec/No.
B. BLER.
C. SIR.
D. Scrambling code.
Answer: B
5. The possible pilot
pollution area can be detected from which one of the following?
A. Ec/No lower than
target and low number of scrambling codes seen.
B. Ec/No lower than target
and high number of scrambling codes seen.
C. Ec/No higher than
target and low number of scrambling codes seen.
D. Ec/No higher than
target and high number of scrambling codes seen.
Answer: B
6. How can capacity
(interference) be improved?
A. Usage of transmission
diversity.
B. Increasing
transmission power of UEs.
C. Decreasing speed of
UEs.
D. Increasing SHO.
Answer: A
7. For the use of a
shared antenna line between GSM and WCDMA, what is needed?
A. Coupler or splitter.
B. One shared BTS for
GSM and WCDMA.
C. Same output power
both GSM and WCDMA.
D. Diplexer or
triplexer.
Answer: D
8. Which one of the
following is NOT a method to decrease inter-system interference?
A. Tighter filtering for
the Tx signal of GSM BTS.
B. Proper frequency
planning in GSM.
C. Usage of shared
antenna line.
D. Careful antenna
selection and placing.
Answer: C
9. The most appropriate
reason for Power control headroom is to:
A. improve the downlink
reception.
B. maintain the fast
power control at the cell edge.
C. compensate slow
fading.
D. increase the
transmitting power of user equipment (Ue).
Answer: B
10. What is the MAXIMUM
number of P-CPICH signals, of similar strength, that the UE should measure?
A. 1 WBTS cell.
B. 2 WBTS cells.
C. 3 WBTS cells.
D. 4 WBTS cells.
Answer: C
11. Considering 1 site
(3 cells) with 1 only one carrier per cell, how many traffic hardware channels
are needed if in the site the active users are: 1.8 voice, 0.7 CS64, 0.7 PS64
and 1 PS384 and knowing that for each connection the following hardware channels
apply: 1 for voice, 4 for CS64, 4 for PS64 and 16 for PS384 are needed?
A. 4
B. 13
C. 24
D. 37
Answer: C
12. Considering 1 site
(3 cells) with 1 only one carrier per cell, what is the downlink throughput (in
Kb/s) PER CELL if in the site the active users are: 1.8 voice, 0.7 CS64, 0.7
PS64 and 1 PS384?
A. 64.94.
B. 165.19.
C. 194.82.
D. 514.76.
Answer: B
13. For what reason
should the power control strategy be changed?
A. UE location.
B. UE type.
C. UE service.
D. UE speed.
Answer: D
14. Which one of the
following network planning tasks is NOT normally performed with a radio network
planning tool?
A. Coverage planning.
B. Traffic calculation.
C. Hardware channel
calculation.
D. Monte Carlo
Simulation.
Answer: C
15. The Node B antenna
gain is 17 dB and receiver sensitivity 112 dBm, radiated power (EIRP) of user
equipment (Ue) is 18 dBm and feeder cable loss is 3 dB. What is the MAXIMUM
path loss?
A. 114 dB
B. 116 dB
C. 144 dB
D. 147 dB
Answer: C
16. If the cell radius
is 2 km and the required service area is 100 km2,how many 3-sector sites (in
coverage-limited case) are needed to provide the service for the area (k factor
for site area is 1.95)?
A. 5
B. 8
C. 13
D. 19
Answer: C
17. What is the
interference margin for 50% and 90% network loads?
A. 3.0 dB and 10.0 dB.
B. 5.0 dB and 1.5 dB.
C. 3.0 dB and 7.0 dB.
D. 4.0 dB and 10.0 dB.
Answer: A
18. When applying the
free space propagation loss formula both for GSM 1800 and WCDMA, what
APPROXIMATELY is the propagation loss difference between the systems, if the distance
from the BTS is 1500 meters? (Use frequency
2100 MHz for WCDMA.)
A. 5.5 dB.
B. 1.3 dB.
C. 7.4 dB.
D. 13.4 dB.
Answer: B
19. Which one of the
following does NOT make the UL adjacent channel interference worse?
A. UE transmitting with
maximum power.
B. UE uses hard
handover.
C. Other operator BTS in
a bad location.
D. Own BTS transmitting
with high power.
Answer: D
20. The required Eb/No
value is dependent on which one of the following factors?
A. Base station antenna
gain.
B. Speed of the user
equipment (Ue).
C. Fast fading margin.
D. Body loss.
Answer: B
1- What are the main KPI to measure the performance of 3G
cell
- Accessibility ( RRC , RAB , CSSR)
- Retainability (speech , Video , PS DCR)
- Mobility (SHO , IRAT HO success rate)
2- What resources affect HSDPA throughput in 3G system
- (DL power, DL code and transport capacity)
3- What parameter tuning can be done to improve HSDPA
throughput in any 3G cell
-
increase the DL channelization codes for HSDPA
-
changing the scheduling algorisms
4- How can we reach 21 Mbps in P7
- 15 codes in DL and 64 QAM
5- what is the usage of the following signaling messages
in RRC protocol
- Actives setup updates (ADD/Remove/Replace RL in SHO)
- RB reconfiguration (channel switching between Cell_DCH and
Cell_FACH RRC stats)
- Physical channel reconfiguration (IF HO)
6- what is the use of GPEH tool in Ericsson system
- tool used to record RAN and internal events in Ericsson
system and the tracing files can be analyzed by TEMS visualization
7- what types of congestion can affect the services
accessibility in any 3G cell
- DL power ( AMR - Directed retry - reducing High R.99
RAB users SFxx parameters)
- UL/DL CE ( reducing High R.99 RAB users SFxx
parameters)
- DL code (reducing static codes for HSDPA –AMR-Directed
retry)
- Transport capacity
8- what is the difference between RSCP and EC/No measures
for pilot channel
- RSCP is received signal code power for CPICH channel
- Ec/No is The received energy per chip divided by the
power density in the band . it reflects the quality of CPICH channel
9- what is the difference of using 2nd carrier and high
power amplifier in expanding the capacity for any 3G cell
- 2nd carrier gives capacity in DL power and DL codes
- High power Amplifier gives capacity in DL power only
10- what is the max bit rate that can be achieved in UL
when using 10ms EUL and 2 ms EUL
- 1.5 Mbps for 10 ms EUL
- 5.76 for 2 ms EUL
11- how many HSSCCH channel can be configured in HSDPA
cell (
- Four that allows four users per TTI
Good boy
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