@ I am sharing some questions of today interview conducted by people for L2
HRO...CA, Mimo, PCI,pilot pollution,throughout issues and resolution,different kpis, tilt
recommendation, reference signal,
--------L2 another interview questions
1: Scell criteria
2: MLB Mobility Load Balancing
3: PA PB
4: PCI clash and confusion
5: How to improve SDR Session Drop Rate
In LTE, SDR (Session Drop Rate) is a key KPI that measures the percentage of dropped sessions
before successful completion. A lower SDR indicates better network stability. Here’s how to improve it:
1. Optimize Radio Conditions

Enhance SINR & RSRP: Improve signal quality using better antenna tilt, power control, and
interference management.

Deploy Carrier Aggregation (CA): This helps maintain stable connections by using multiple
carriers.

Improve MIMO Configurations: Higher-order MIMO (e.g., 4x4) can enhance link stability.
2. Optimize Mobility & Handover

Reduce Ping-Pong Handovers: Tune A3/A5 handover parameters to avoid unnecessary
handovers.

Use Proper Hysteresis & Time-to-Trigger (TTT): Adjust values to ensure smooth handovers.

Enable X2-based Handovers: Reduces drop probability by ensuring seamless transitions
between eNodeBs.
3. Core Network Enhancements

Optimize S1 & X2 Interface Performance: Ensure minimal latency in handover signaling.

Monitor MME & SGW Load: Avoid overloads to prevent session drops.

Reduce Packet Loss & Jitter: Use QoS prioritization for critical signaling traffic.
4. Improve Hardware & Capacity Planning

Expand Network Capacity: Add more eNodeBs or small cells to handle congestion.

Upgrade to VoLTE for Voice Stability: If using CSFB (Circuit-Switched Fallback), optimize it to
avoid long call setup times.

Ensure Backhaul Stability: Optimize fiber/microwave links to reduce transmission delays.
5. Detect & Fix Faults Proactively

Monitor Alarms & Logs: Identify and fix hardware/software failures quickly.

Use AI-based Predictive Maintenance: Analyze trends to prevent outages.

Optimize RRC Connection Handling: Ensure RRC connections are properly maintained without
excessive releases.)
6: Erab improvement
7: MME drops how to resolve
8: CA type
-----------L2 Interview questions yesterday asked from someone
Answers
1: Handover,SRVCC & IRAT events?
Answer: A1 (measurement stop threshold) , A2 (Measurement start), A3 (Intrafreq) ,A4
(Load based), B1, B2 (used for SRVCC/IRAT based on InterRAT Event Type strategy)
2: Where B1 & B2 events used?
Answer: for SRVCC/IRAT
3: LTE Mobility (HO events (A1,A2,A3,A4,A5 & A6)
Threshold & Modification.
Answer: A1, A2 to retain or lose traffic from LTE
A3 is for Intrafreq HO, A4 is for load based and B1, B2 to retain traffic on LTE or to shift
on 3G/2G based on network strategy
4: LTE low Throughput Reasons
Answer: High PRB,High Users, poor CQI, poor MCS etc
5: 2G/3G/4G DCR Reasons & Solutions
Answer: 2G: Quality and levels drops. Check physical.designs and Interference and
frequency plan
3G. Check Interference, coverage and quality.
4G. Explained above
6: Modulation schemes & CQI range
Answer. 16 QAM, 64 QAM, 256 QAM. CQI range is from 1 to 15
7: what is Massive MIMO,4T4R,4T6S
Answer: Massive MIMO is a technique to improve Throughput, 4T4R is hard expansion,
4T6S is twin beam/ split sector
7: 3G (RRC,RAB,Power Congestion, Code Congestion, CE Congestion ( Reason &
Solution)
Answer: Power Congestion occur due to high users. Need to relax User num threshold,
Code Congestion can be reduced to reduce HSPDSCH codes from 5 to 1, CE
Congestion can be reduced to balance the boards, increase boards and replace it
8: LTE (ERAB,RRC) Reason & Solution
Answer: RRC degraded due to.no reply or license limit breach. Downtilt and increase
licenses can resolve this. Erab Explained previously
9: Volte introduction,
Answer: 4G having both data and voice on IMS
Difference between Volte & LTE
Answer: VoLTE having both data and Voice and HO happens in SRVCC phase
LTE having data only and CSF happen
10: Architecture of Volte/LTE/3G
Answer: Please Google this :)
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