LTTS- 4G & 5G LTE_NR RAN Engineering Training_Week 3 Assesssment LTTS_Week3 The number of attempts remaining is 1 1 / 30 1. A 5G SA UE is registered, but no user-plane traffic can reach the data network. Which procedure should be investigated separately from Registration? a. SSB transmission only b. PDU Session Establishment and N3/user-plane setup c. RRC cell search only d. PRACH preamble generation only 2 / 30 2. Which statement best distinguishes F1 from Xn? a. They are identical interfaces with different names b. F1 connects CU and DU within a split gNB; Xn connects NG-RAN nodes for inter-node procedures such as mobility c. F1 connects gNB to UPF; Xn connects UE to gNB d. F1 is LTE-only; Xn is EPC-only 3 / 30 3. In an F1 split gNB architecture, which pairing is correct? a. F1-C: CU control-plane signaling; F1-U: CU/DU user-plane connectivity b. F1-C: EPC; F1-U: MME c. F1-C: PHY; F1-U: RRC d. F1-C: UE-to-AMF; F1-U: AMF-to-UPF 4 / 30 4. In LTE Attach, which sequence correctly represents the major control-plane progression after initial radio access? a. RRC Setup → NAS Attach Request → Authentication/Security → Attach Accept b. Authentication → PRACH → RRC Setup → Attach Accept c. NAS Attach Request → RRC Setup → Attach Accept → Authentication d. RRC Release → NAS Attach → Security → Attach Accept 5 / 30 5. In an LTE X2-based handover, what is the main architectural advantage of X2 compared with S1-based preparation? a. It guarantees zero packet loss b. It allows direct source-target RAN preparation without requiring MME to relay the preparation signaling c. It eliminates the EPC completely d. It eliminates target-cell admission 6 / 30 6. Which combination correctly associates the handover architecture with the preparation interface? a. NR-Xn: AMF-mediated; NR-N2: gNB-only b. LTE-X2: core-mediated; LTE-S1: direct RAN c. X2 and S1 are user-plane interfaces only d. LTE-X2: direct RAN preparation; LTE-S1: core-mediated preparation 7 / 30 7. In 5G SA registration, which entity primarily acts as the NAS registration endpoint toward the UE? a. UPF b. AMF c. SMF d. gNB 8 / 30 8. A CFRA UE sends the correct dedicated preamble, but no RAR is received. Which conclusion is strongest? a. Collision is necessarily the cause b. CFRA eliminates contention but not RF, timing, beam, configuration, or response-window failures c. Msg4 must have been corrupted d. The AMF must be unreachable 9 / 30 9. What is the fundamental distinction between SIMD and ordinary scalar execution? a. SIMD requires multiple different instructions for each data element b. SIMD applies one instruction to multiple data elements simultaneously c. SIMD executes only integer operations d. SIMD eliminates memory access 10 / 30 10. A UE successfully completes 5G authentication but fails during NAS Security Mode Control. Which interpretation is most appropriate? a. PRACH must always be retried b. Security capability, algorithm, key/context, or implementation handling may be faulty c. Authentication success guarantees security activation d. UPF routing must be the root cause 11 / 30 11. A handover completes at the target, but the UE experiences RLF several seconds later. Which KPI combination is most useful for identifying a mobility-robustness problem? a. Post-HO RLF combined with elevated ping-pong b. High registration success only c. Low paging load only d. High PRACH success only 12 / 30 12. In EN-DC, why can an NR measurement configuration appear in LTE RRC signaling? a. Measurements are always configured by the UPF b. LTE acts as the Master Node and controls the EN-DC connection c. NR has no RRC d. NR measurements are generated by the EPC 13 / 30 13. A UE repeatedly transmits Msg1 but never receives a valid RAR. Which failure domain should be examined first? a. UPF routing b. Msg4 contention-resolution identity c. PRACH detection, configuration, power, occasion, or RAR monitoring d. PDCP ciphering 14 / 30 14. In CBRA, which stage primarily resolves the contention between UEs that may have responded to the same RAR? a. Msg4 b. Msg1 c. Msg3 d. Msg2 15 / 30 15. During NR handover completion, why is Path Switch important even after the UE has successfully accessed the target gNB? a. It releases the UE's SIM b. The core/user-plane path must be updated so traffic is associated with the target gNB c. It assigns the original SSB d. It performs the UE's first authentication 16 / 30 16. In a modern Intel Xeon processor, why can a workload with many CPU cores still fail to scale linearly? a. More cores always reduce memory latency to zero b. Each core must execute the same scalar instruction c. Memory bandwidth, cache contention, synchronization, instruction dependencies, or vector-unit limits can become bottlenecks d. SIMD disappears when multiple cores are used 17 / 30 17. Which statement about Msg3 and Msg4 in CFRA is most accurate? a. They may be unnecessary for the contention-resolution portion because the resource is dedicated b. They contain the dedicated preamble c. They replace Msg1 and Msg2 d. They are always mandatory for contention resolution 18 / 30 18. A UE loses its NR SCG in EN-DC but continues exchanging user-plane traffic through LTE. Which conclusion is most accurate? a. The entire UE connection necessarily failed b. The UE must have deregistered c. The LTE anchor and configured bearer path may still support service d. NR SCG loss always triggers LTE handover 19 / 30 19. In 5G SA registration, which sequence is most consistent with the control-plane architecture? a. UE → UPF → UDM → gNB → Registration Accept b. UE → SMF → gNB → AUSF → Registration Accept c. UE → gNB → AMF → AUSF/UDM → security → Registration Accept d. UE → UPF → AMF → gNB → Registration Accept 20 / 30 20. Which workload is most likely to benefit strongly from SIMD execution on a Xeon processor? a. A single scalar comparison b. A branch-heavy algorithm where every element follows a different unpredictable path c. Serial linked-list traversal with dependent pointers d. Applying the same arithmetic operation independently to thousands of signal samples 21 / 30 21. An LTE UE successfully completes RRC establishment, but the MME never receives the NAS Attach Request. Which fault domain is most directly suspected? a. PRACH collision b. UE RF receiver only c. NAS/RRC transport or RAN-to-core signaling path d. SGW user-plane tunnel 22 / 30 22. In a handover trace, the UE receives the handover command but T304 expires before successful target access. Which phase has primarily failed? a. Execution b. Post-handover KPI accounting c. Long-term load balancing d. Preparation 23 / 30 23. In an NR Xn-based handover, what is the primary role of the AMF during the radio preparation phase? a. It performs UE synchronization b. It directly controls every UE PRACH preamble c. It is generally not the direct source-target radio preparation path; core involvement becomes important for path switching/context procedures d. It replaces the target gNB 24 / 30 24. In 4-step contention-based random access, which message first carries scheduled UL resources allocated through the RAR? a. Msg2 b. Msg1 c. Msg4 d. Msg3 25 / 30 25. Why does LTE Attach completion not by itself prove that the UE has an active user-plane bearer? a. User plane is created by the UE without EPC signaling b. Attach establishes registration/control context; dedicated EPS bearer establishment is a separate step c. Attach occurs after user-plane establishment d. Attach only configures PRACH 26 / 30 26. Why is CFRA particularly useful during handover? a. CFRA bypasses all PHY procedures b. CFRA removes the need for target synchronization c. The UE has no identity d. The network already knows the UE context and can assign a dedicated random-access resource 27 / 30 27. In NSA EN-DC, which event represents a change of the NR secondary leg without necessarily changing the LTE control anchor? a. SCG/SgNB mobility b. N2 inter-system handover c. EPS detach d. LTE MCG handover 28 / 30 28. Which statement best distinguishes 5G Registration from PDU Session Establishment? a. Registration establishes UE registration with the network; PDU Session Establishment creates the session/user-plane connectivity b. PDU Session Establishment always precedes registration c. Registration only configures the UPF d. They are exactly the same procedure 29 / 30 29. Two UEs select the same CBRA preamble in the same PRACH occasion. Why might the collision not be immediately obvious from Msg1? a. PRACH always rejects duplicate preambles immediately b. Msg1 is encrypted c. PRACH correlation can detect a common preamble/occasion without uniquely identifying both UEs d. Msg1 contains each UE's IMSI 30 / 30 30. A vector loop processes 16 independent floating-point values with one instruction on a sufficiently wide vector register. What is the primary advantage? a. Elimination of cache misses b. Potentially higher arithmetic throughput through data-level parallelism c. Elimination of all instruction overhead d. Guaranteed 16× application speedup Your score is
