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5G NR interview questions and answers | 5G New Radio

This page describes 5G NR (New Radio) questionnaire written by specialists in 5G domain. This top 5G NR interview questions and answers will help interviewee pass the job interview for 5G NR job position.

Question -1: What is 5G NR ?
Answer -1: 5G stands for Fifth Generation and NR stands for New Radio. This technology is evolution to LTE-advanced and LTE-advanced Pro. The standard is published with 3GPP release 15 and above.
Refer 5G NR Features ➤.

Question -2: What is the difference between 5G NR and 4G (LTE) ?
Answer -2: 4G LTE and LTE-advanced follows 3GPP Rel.8 and Rel.12 respectively. 5G follows Rel 15 and above. 4G operates below 6 GHz where as 5G NR operates at various frequency bands viz. Sub-1 GHz, 1 to 6 GHz, above 6 GHz in mm wave bands (28 GHz, 40 GHz etc.). 5G supports higher data rate than 4G. 5G delivers about 10 Gbps where as LTE-a pro delivers 3 Gbps. 5G offers latency of less than 1 ms where as LTE-adv pro delivers less than 2 ms.
Refer 4G vs 5G ➤ and 4G vs 4.5G vs 4.9G vs 5G ➤ and LTE vs 5G NR vs 5G TF ➤ for more difference between them.

difference between 5G NR and 4G LTE

Question -3: Explain 5G NR network architecture, its elements and its network interfaces ?
Answer -3: There are three elements in 5G NR architecture viz. UE (User Equipment), RAN and Core Network. NG RAN houses gNB radio (i.e. base station), Control Unit and data Unit. Here AMF stands for Access and Mobility Management Function and UPF stands for User Plane Function.
Refer 5G NR architecture ➤.

5G NR Overall architecture

Question -4: Explain difference between TDD and FDD in 5G NR ?
Answer -4: In FDD mode, both uplink and downlink can transmit at the same time at different spectrum frequencies. In TDD mode, both uplink and downlink use the same spectrum frequencies but at different times. 5G FDD is used where both uplink and downlink data rates are symmetrical. Interference is less in FDD topology where as it is more in TDD topology. 5G TDD is used where both uplink and downlink data rates are asymmetrical.
Refer 5G TDD vs FDD ➤.

Question -5: Define use cases of 5G NR viz. eMBB, mMTC and URLLC.
Answer -5: eMBB refers to Enhanced Mobile Broadband which is used to support peak data rate of 10 to 20 Gbps. mMTC refers to Machine Type Communications which is used to support low data rates (1 to 100 Kbps) in M2M applications. URLLC refers to Ultra Reliability and Low Latency Communcations which is used for ultra responsive connections with latency of less than 1 ms. URLLC offers low to medium data rates.
Refer 5G Use cases ➤.

5G eMBB mMTC URLLC

Question -6: What are the different types of handover in 5G NR? Explain each in brief.
Answer -6: There are two types of 5G NR handovers viz. network controlled and UE controlled. The other types mentioned in the standard are 5G NR Inter gNB handover and 5G NR intra RAN handover (C-Plane Handling).
Refer 5G Handover types ➤.

Question -7: What are the functions of MIB and SIB in 5G ?
Answer -7: 5G Master Information Block (MIB) includes system information transmitted on xBCH transport channel and xBCCH logical channel. The IE (Information Element) XSystemInformationBlock contains RRC (radio resource configuration) information which is common for all UEs. It is transmitted on xBCCH logical channel and xBCH transport channel.
Refer 5G MIB SIB Blocks ➤.

Question -8: Explain 5G NR deployment scenarios or modes viz. NSA (Non-Standalone), SA (Standalone), Homogeneous mode and Heterogeneous mode.
Answer -8: • In SA mode, UE works by 5G RAT alone and LTE RAT is not needed. 5G cell is used for both C-Plane (Control Plane) and U-Plane (User Plane) to take care of both signaling and information transfer.
• In NSA mode, connection to both LTE cell and 5G cell are mandatory. In this Non-standalone mode, LTE is used for control (C-Plane) functions e.g. call origination, call termination, location registration etc where as 5G NR will focuse on U-Plane alone.
Refer 5G NR Deployment Modes ➤.

Question -9: What is the range and speed in 5G NR technology ?
Answer -9:• 5G Speeds of about 20 Gbps in the downlink and 10 Gbps in the uplink are benchmarked by 5G operators once the 5G network matures. Recently many operators have achieved 5G throughput or 5G speed in the range of about 5Gbps.
•  5G range is lesser than supported by 4G LTE or 3G networks. It is more of equivalent to wifi range than cellular range. Refer 5G speed vs range ➤.

5G range

Question -10: What are the functions of RRC layer in 5G NR ? Explain RRC states with state diagram.
Answer -10: Following are the functions of RRC layer.
Following are the functions performed by RRC layer in 5G NR protocol stack.
➨ Broadcast SI (System Information) messages to AS (Access Stratum) and NAS (Non-Access Stratum).
➨ Handles paging initiated by 5GC (5G Core Network) or NG-RAN (Radio Access Network).
➨ Establishment, maintenance and release of RRC Connection between 5G NR UE and NG-RAN. This includes addition, modification and release of CA(carrier aggregation) and Dual connectivity in NR or between E-UTRA and NR.
➨ Security related functions including key management
➨ Establishment, configuration, maintenance and release of SRBs (Signaling Radio Bearers) and DRBs (Data Radio Bearers).
➨ Mobility functions such as handover, context transfer, UE cell selection/re-selection, control of cell selection/re-selection, Inter-RAT mobility etc.
➨ QoS management
➨ UE measurement reporting, control of reporting
➨ Detection of radio link failure and recovery from radio link failure
➨ NAS message transfer to/from NAS from/to UE

5G NR UE RRC States

There are three states in RRC viz. RRC_IDLE, RRC_INACTIVE and RRC_CONNECTED. Refer RRC states ➤.

Question -11: Which are the KPIs used in 5G NR ?
Answer -11: 5G KPIs are categorized into eMBB, URLLC and mMTC. The common KPIs are peak data rate, peak spectral efficiency, latency, traffic capacity, connection density, energy efficiency, reliability and so on.
Refer 5G NR KPIs ➤.

Question -12: What are the frequency bands of 5G NR used in various parts of the world such as USA, Europe, China, Japan, Korea, INDIA, and so on ?
Answer -12: Following table mentions 5G NR frequency bands used in above regions of the world.
Refer 5G Bands ➤.

5G frequency bands

Question -13: What is CORESET in 5G ?
Answer -13: Resource allocation unit in 5G NR is CORESET ( Control Resource Set ). Time domain and frequency domain parameters of CORESET are defined in TS 38.211 document.
Refer 5G CORESET ➤.

Question -14: What is Mini slot in 5G ?
Answer -14: Figure below depicts frame, subframe and slot structure used in 5G NR technology. Mini-slot occupies 2, 4 or 7 OFDM symbols. It enables non-slot based scheduling. It is minimum scheduling unit used in 5G NR. As mentioned mini-slots can occupy as little as 2 OFDM symbols and are variable in length.
Refer 5G NR Mini Slot ➤.

5G NR Frame Structure-slot,mini-slot

Question -15: Explain 5G NR frame and subframe structure with possible combinations.
Answer -15: The figure depicts 5G NR frame/subframe structure with possible combinations.
Refer 5G NR frame subframe structure ➤.

5G Frame Structure 5G Subframe Structure possible combinations

This set of 5G NR interview questions and answers are useful for freshers and experienced level of job positions. Following are the useful resources to learn more on 5G technology.



5G NR Numerology | 5G NR Terminology


5G NR Control channels | 5G NR Traffic Channels | 5G NR Reference Signals and sequences


5G TECHNOLOGY RELATED LINKS

This 5G tutorial also covers following sub topics on the 5G technology:
5G basic tutorial    5G Frequency Bands    5G millimeter wave tutorial    5G mm wave frame    5G millimeter wave channel sounding    Difference between 4G and 5G    5G testing and test equipments    5G network architecture    5G NR Physical layer    5G NR MAC layer    5G NR RLC layer    5G NR PDCP layer   

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