5G RRC Layer Interview Questions – Expert Scenario Based (20 Q&A)
This page provides expert-level 5G RRC layer interview questions covering connection management, mobility, bearer configuration, real-field failures and lab troubleshooting. These questions are designed for RAN development, system integration, optimization and L2/L3 support roles.
Conceptual & Design-Level Questions
Q1. What is the primary role of RRC in 5G NR?
RRC manages connection setup and release, radio bearer configuration, mobility control, security activation and overall control-plane signaling between UE and gNB.
Q2. How does 5G RRC differ from LTE RRC?
5G RRC supports flexible numerology, multiple BWPs, beam-based measurements, enhanced mobility and tighter interaction with 5G Core.
Q3. Why is RRC considered a control-plane heavy layer?
RRC carries all signaling procedures such as connection management, measurements, mobility, security and bearer configuration.
Q4. What triggers RRC reconfiguration?
Mobility decisions, QoS changes, BWP switching, DRB/SRB setup or optimization actions trigger RRC reconfiguration.
Connection & Bearer Management
Q5. What happens during RRC connection establishment?
UE and gNB exchange RRC messages to establish SRBs, configure initial radio parameters and transition UE to connected state.
Q6. Difference between SRB and DRB?
SRBs carry RRC and
NAS signaling,
while DRBs carry user-plane data with specific QoS.
Q7. How does RRC configure QoS?
RRC configures QoS parameters such as 5QI, priority and mapping to lower layers for each DRB.
Q8. What causes RRC connection release?
Inactivity, radio link failure, handover failure or explicit network-triggered release.
Mobility & BWP Scenarios
Q9. How does RRC support mobility?
RRC configures measurements, evaluates events and issues handover commands to maintain session continuity.
Q10. What is the role of measurement events?
Measurement events trigger reports based on signal conditions, enabling mobility and optimization decisions.
Q11. Why do handovers sometimes fail?
Poor radio conditions, delayed measurement reports, incorrect thresholds or signaling interruption.
Q12. How is BWP switching controlled by RRC?
RRC configures multiple BWPs and activates them dynamically based on traffic demand, UE capability and power efficiency.
Real Field & Log Analysis Scenarios
Q13. UE drops after RRC reconfiguration – why?
Misconfigured parameters, security mismatch with
PDCP
or lower-layer reconfiguration failure can cause drops.
Q14. How do you analyze RRC issues in logs?
Analyze message sequence, timers, failure causes and interaction with MAC, RLC and PDCP layers.
Q15. Why does UE frequently move between states?
Aggressive inactivity timers, unstable radio conditions or poor mobility configuration.
Q16. What causes delayed RRC procedures?
Signaling congestion, retransmissions at lower layers or processing latency.
LAB & Hands-On Scenarios
Q17. In lab, handover succeeds but throughput drops – why?
RRC may have reconfigured BWPs or QoS incorrectly during handover, impacting throughput.
Q18. How do you test RRC mobility in lab?
Vary signal strength, trigger measurement events and monitor handover success and delay.
Q19. Lab shows repeated RRC reconfigurations – debugging steps?
Check measurement thresholds, timer values and optimization parameters.
Q20. How do you design an RRC stress test?
Generate frequent mobility events, bearer modifications and state transitions while monitoring signaling load.
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