Typical 5G LTE Network Engineer Interview Questions

1

How does LTE implement TTI bundling?

Reference answer

TTI bundling transmits the same data over multiple subframes for coverage enhancement.

2

Define Physical Cell Identity (PCI) in LTE.

Reference answer

PCI is a unique identifier for a cell, used for synchronization and reference signals.

3

What is an IP address and why is it needed?

Reference answer

An IP address is a unique logical address assigned to every device on a network. It allows devices to locate each other and exchange data across local networks and the internet. It works on Layer 3.

4

Describe how LTE handles paging messages.

Reference answer

LTE sends paging messages on PDSCH, scheduled by PDCCH, and UEs monitor paging occasions based on DRX.

5

What advantages does SA 5G offer over NSA deployments?

Reference answer

SA 5G deployments unlock the full potential of 5G by delivering improved performance, reduced latency, and advanced features like network slicing and edge computing. They provide a more future-proof solution.

6

What are the different CQI reporting modes in LTE?

Reference answer

CQI reporting modes include periodic (PUCCH) and aperiodic (PUSCH) with wideband or subband.

7

What Tools And Metrics Would You Use To Monitor Network Performance And Health?

Reference answer

Using a blend of tools and metrics allows you to maintain a pulse on network performance and health. Here are some of the most common ones (Keep in mind this answer will vary as there are many tools; the idea is that candidates are able to answer with their own toolkit and why they use it): Performance Monitoring Tools - Network Performance Monitors (NPMs): Tools like SolarWinds, Nagios, and PRTG Network Monitor offer real-time visibility into the performance of network devices and traffic patterns. They can track metrics such as bandwidth usage, packet loss, and latency. - Protocol Analyzers: Wireshark is a widely used protocol analyzer that helps in inspecting the details of network traffic at a granular level. It is instrumental in identifying anomalies and inefficiencies in data transmission. - Speed Test Tools: Tools such as Ookla's Speedtest provide quick assessments of internet connection speed, including download and upload speeds, which are critical for troubleshooting performance issues. Key Metrics for Network Health: - Bandwidth Utilization: This metric measures the amount of data being transmitted over a network connection in a given time frame, helping identify bottlenecks and ensure adequate bandwidth for critical applications. - Latency: Latency indicates the time it takes for a data packet to travel from source to destination. High latency can significantly impact applications requiring real-time communication. - Packet Loss: Packet loss occurs when packets fail to reach their destination, which can degrade network performance and affect application reliability. Monitoring packet loss helps in pinpointing unstable connections or hardware issues. - Jitter: Jitter measures the variability in latency over time in a network. Consistent jitter can cause issues in voice-over IP (VoIP) and video streaming services. Security Assessment Tools: - Intrusion Detection Systems (IDS) and Intrusion Prevention Systems (IPS): These tools, such as Snort or Cisco's Firepower, monitor network traffic for suspicious activities that could indicate a security threat, providing alerts and, in the case of IPS, taking actions to block the threat. - Firewall Management Tools: Tools like FireMon and AlgoSec manage firewall rules and policies, ensuring that firewalls are effectively protecting the network without unnecessarily impeding performance. - Vulnerability Scanners: Tools such as Nessus or Qualys scan network devices for known vulnerabilities, helping administrators to patch potential security holes before they can be exploited.

8

What is a WAN?

Reference answer

Our SD-WAN cut circuit costs 30 percent while improving failover. We used dynamic path selection for voice vs. bulk data. Translating savings into business value is crucial in WAN-focused network engineer interview questions.

9

Describe your experience with wireless networking and troubleshooting Wi-Fi issues.

Reference answer

I have extensive experience designing and implementing wireless networks, ensuring optimal coverage and performance. For troubleshooting Wi-Fi issues, I use tools like Ekahau and Wireshark to diagnose and resolve connectivity problems, resulting in a 40% improvement in network reliability.

10

Describe the Physical Hybrid ARQ Indicator Channel (PHICH).

Reference answer

PHICH carries HARQ ACK/NACK feedback for uplink transmissions.

11

What is SDN (Software-Defined Networking), and what are its benefits?

Reference answer

SDN separates the network control plane from the data plane. This allows for more flexible and programmable network management. Benefits include centralized control and increased network agility. It also enables more straightforward implementation of network-wide policies.

12

What is a VPN?

Reference answer

At my previous company, our sales force needed secure CRM access from hotels. I deployed an SSL VPN with two-factor authentication. Using split tunneling kept video calls on local internet while CRM traffic went through the tunnel, reducing data-center load by 40 percent. We monitored tunnels with SNMP and set alerts for failed logins. Demonstrating how I weigh usability against risk is crucial when answering network engineer interview questions about VPNs.

13

What does career progression look like for you?

Reference answer

The final question requires you to do some real thinking about your personal development and where you want to get to. Whether youâre applying for entry-level network engineer jobs or senior and executive roles within the field, each candidate is different and will have their own idea of what career progression looks like to them. The interviewer will know this and may ask this question to better understand your motivations and why youâre pursuing this particular role within your company. When youâve provided an answer, your future employer will be able to put measures in place to support you with your network engineer career progression, potentially through training or development. Unlike other questions listed in this guide, we're not going to give you the answer to how to prepare for network engineer interview questions like this. Why? Because we feel you're the only person that can answer this question if you truly want to progress in your network engineering career.

14

How do you optimize 5G coverage?

Reference answer

- Beam tuning (SSB, CSI-RS) - Antenna tilt and azimuth - Power optimization - Neighbor optimization - Proper LTE anchor planning (NSA) - mmWave-specific optimization (beam sweeping, etc.)

15

What is the role of virtualization in 5G networks?

Reference answer

Virtualization in 5G allows for the virtualization of network functions and resources, enabling flexible network management, scalability, and efficient resource utilization.

16

What is eMBB? Why it's use in 5G NR?

Reference answer

Enhanced mobile broadband (eMBB) focuses on supporting the ever-increasing end user data rate and system capacity. To fulfill this demand, eMBB introduces two major technology enhancements: Shift of frequency spectrum to cmWave and mmWave range to achieve much higher bandwidth allocations Advanced antenna array that includes tens or even hundreds of TX/RX antenna elements to enable massive MIMO and beamforming

17

What are the benefits of EN-DC?

Reference answer

The benefits of EN-DC include improved coverage, reduced latency, and faster data speeds, as well as the ability to use 5G-specific features and applications.

18

Explain LTE resource mapping for control channels.

Reference answer

Control channels (PDCCH, PCFICH, PHICH) are mapped to the first few OFDM symbols of a subframe.

19

Explain what is meant by "in-band" and "out-of-band" signaling.

Reference answer

In-band signaling uses the same channel as data, while out-of-band signaling uses a separate channel for control information.

20

Tell us a bit about you and your background

Reference answer

This question gives you the opportunity to tell your potential employer a bit about you, from your interests to how you got to where you are in your network engineering career, whether youâre a graduate or senior network engineer. Keep your answer concise without rambling off-topic, and remember itâs important to keep linking back to the role and any previous positions youâve had within the space that are relevant to the network engineer job youâre applying for.

21

What is the role of edge computing in 5G architecture?

Reference answer

Edge computing is a key feature of 5G architecture that enables data processing and storage to occur closer to the end user, reducing latency and improving overall network performance.

22

How do you ensure compliance with network security policies and regulations?

Reference answer

I ensure compliance with network security policies and regulations by implementing and enforcing security controls, conducting regular audits and vulnerability assessments, and staying updated with relevant laws and standards. I also provide training for users and staff on security best practices and monitor compliance through continuous monitoring and reporting.

23

What are the considerations for interoperability and roaming in the air interface of 5G?

Reference answer

The air interface in 5G takes into account interoperability and roaming standards, protocols, and mechanisms to enable seamless communication and mobility across different operators and networks.

24

Can EN-DC work with other technologies like Wi-Fi and Bluetooth?

Reference answer

Yes, EN-DC can work in conjunction with other wireless technologies like Wi-Fi and Bluetooth, allowing for seamless connectivity across different networks and devices.

25

Explain The Primary Function Of A Firewall In A Network

Reference answer

A firewall is a network security device that monitors incoming and outgoing network traffic to determine if it should be permitted or denied based on specific security protocols. Its main role is to serve as a barrier that separates secure internal networks from potentially hazardous external ones, like the internet, to protect the internal network from unauthorized access, cyberattacks and other security threats.

26

Explain the difference between SISO and MIMO.

Reference answer

SISO uses a single antenna for transmission and reception, while MIMO uses multiple antennas for improved performance.

27

Define "S1-flex" in LTE architecture.

Reference answer

S1-flex allows an eNodeB to connect to multiple MMEs/S-GWs for load balancing and redundancy.

28

What is the function of the PHICH in LTE?

Reference answer

PHICH carries HARQ ACK/NACK for uplink data.

29

Explain the primary role of the eNodeB scheduler in LTE.

Reference answer

The eNodeB scheduler allocates time-frequency resources to UEs based on QoS requirements, channel conditions, and buffer status.

30

Describe the derivation process for KeNB.

Reference answer

KeNB is derived from KASME for AS security, used to generate RRC and UP keys.

31

Define "resource mapping" in the context of LTE.

Reference answer

Resource mapping refers to assigning physical resource blocks to logical channels for transmission.

32

What is a hub?

Reference answer

I haven't deployed a production hub in years, but I keep one in my toolkit as a quick span alternative when the switch has no free port. By mirroring traffic through the hub, I captured a DHCP storm that was flooding our guest VLAN. Explaining legacy gear and why we replace it shows historical context and troubleshooting creativity that network engineer interview questions often probe.

33

What is mmWave? Why it doesn't it travels far from origin?

Reference answer

Millimeter waves, also known as extremely high frequency (EHF), is a band of radio frequencies that is well suited for 5G networks. Compared to the frequencies below 5 GHz previously used by mobile devices, millimeter wave technology allows transmission on frequencies between 30 GHz and 300 Ghz. millimeter waves can travel recorded up to 10.8 kilometers at 14 spots that were within line of sight of the transmitter, and recorded them up to 10.6 kilometers away at 17 places where their receiver was shielded behind a hill or leafy grove. Note: 5G signals can be blocked by physical barriers like walls and glass. Difficulty in moving found from outdoors to indoors that can be result, in poor coverage and slower download speeds.

34

What is a subnet mask?

Reference answer

A subnet mask is combined with an IP address to identify two parts: the extended network address and the host address. Like an IP address, a subnet mask is made up of 32 bits, and it determines the network and host portions.

35

What is the difference between static routing and dynamic routing?

Reference answer

Static routing involves manually configuring the routing table with fixed paths for data packets. It's simple and secure but requires manual updates when network changes occur. Dynamic routing, on the other hand, uses algorithms and protocols like OSPF or EIGRP to automatically adjust paths based on network conditions. It adapts to changes more efficiently and reduces administrative overhead, but it may be more complex and resource-intensive to manage.

36

Which deployment option is recommended for long-term 5G planning?

Reference answer

Standalone (SA) 5G deployments are recommended for long-term planning as they provide a more robust and scalable solution, supporting the full suite of 5G capabilities and enabling future network evolution.

37

What is data encapsulation?

Reference answer

Data encapsulation is the process of breaking data into smaller, manageable pieces before it is transmitted across the network. In this process, source and destination addresses are appended to the headers, along with error checks.

38

Have you led a team of engineers before?

Reference answer

This question assesses the candidate's leadership experience and capability to manage or guide engineering teams.

39

What is MIMO and how is it used in 5G?

Reference answer

MIMO (Multiple Input Multiple Output) uses multiple antennas at both transmitter and receiver to improve communication performance. In 5G, massive MIMO with dozens or hundreds of antennas enhances data throughput, spectral efficiency, and signal reliability by enabling beamforming and spatial multiplexing.

40

How does LTE handle idle mode handovers?

Reference answer

Idle mode handovers are cell reselections based on measurements and priorities.

41

Explain the UE measurement process for handover.

Reference answer

The UE measures neighbor cells and reports based on configured events.

42

Explain how HARQ feedback works.

Reference answer

HARQ feedback sends ACK/NACK on PUCCH or PHICH for received data.

43

Can You Walk Me Through The Process You Would Follow To Replace A Stack Of Switches In An Edge Wiring Closet?

Reference answer

This question is perfect for understanding the candidate's practical experience with network hardware and their understanding of physical network infrastructure. It also asses the engineer's awareness of the potential impact of such changes on the network's operations and their ability to mitigate disruptions. Answer sample: Initially, I would review the current network architecture and the specific role of the switches to be replaced. Understanding the configurations, VLANs, and routing protocols in use is crucial. I'd also inventory the physical connections and document the existing setup. Planning involves scheduling the replacement during off-peak hours to minimize impact and notify affected stakeholders of the planned downtime. Before proceeding with the replacement, I'd ensure that the current configuration of each switch is backed up. This step is vital for quickly restoring services in case of any issues during the transition. With preparations complete, I'd proceed to physically replace the old switches with the new ones. This involves carefully disconnecting and labeling cables, removing the old switches, mounting the new switches in the rack, and reconnecting the cables as per the documented setup. Once the new switches are physically installed, I'd configure them according to the documented settings of the old switches. This includes setting up VLANs, implementing security policies, and configuring routing protocols as necessary. Wherever possible, I'd leverage the backup configurations to expedite this process. After configuration, comprehensive testing is essential to ensure the new switches are correctly integrated into the network and operating as expected. This includes testing connectivity, bandwidth, and latency, as well as verifying that all security features are active and effective. With the new switches operational, I'd closely monitor the network performance to identify any issues early. This phase also allows for fine-tuning configurations to optimize network performance. Finally, updating network documentation to reflect the new hardware and configurations is crucial. I'd also conduct a post-implementation review to evaluate the replacement process, identify lessons learned, and make recommendations for future upgrades.

44

How does 5G facilitate network densification?

Reference answer

5G facilitates network densification by deploying a higher number of smaller cells in close proximity, ensuring better coverage, increased capacity, and improved user experiences, especially in densely populated areas.

45

Describe the LTE scheduling algorithms.

Reference answer

LTE scheduling algorithms include round-robin, proportional fair, and max-throughput, optimizing resource allocation based on channel conditions.

46

What is the purpose of DL Power Control?

Reference answer

DL power control adjusts eNodeB transmit power to optimize coverage and reduce interference.

47

Describe the main purpose of a longer sequence (T_SEQ) in certain preamble formats.

Reference answer

A longer T_SEQ improves detection in large cells or high-speed scenarios.

48

How do you integrate on-premises infrastructure with cloud resources?

Reference answer

To integrate on-premises infrastructure with cloud resources, skilled candidates would explain they'd need to: Use secure connections like VPNs or dedicated links to connect to the cloud; Implement hybrid architectures that combine local and cloud resources; Ensure data security with encryption and strong access controls; Optimize traffic flow with intelligent routing and load balancing; Monitor and manage cloud usage to ensure performance and cost-effectiveness.

49

What is the maximum data speed supported by EN-DC?

Reference answer

EN-DC can support data speeds of up to 2 Gbps, depending on network conditions and device capabilities.

50

What interests you about this network engineer position?

Reference answer

I am particularly interested in this network engineer position because it offers the opportunity to work with cutting-edge network technologies and innovative solutions. Your company's commitment to maintaining a robust and secure network infrastructure aligns with my professional values and career aspirations. I am excited about the potential to contribute to your team, enhance network performance, and ensure high availability and security. Additionally, the collaborative and dynamic work environment at your organization is very appealing to me.

51

Describe the function of the Physical Uplink Control Channel.

Reference answer

PUCCH carries control info like CQI, SR, and HARQ ACK/NACK.

52

Explain the UE Power On procedure in LTE.

Reference answer

Power On includes cell search, system information acquisition, and attach procedure.

53

Define the concept of "time domain scheduling."

Reference answer

Time domain scheduling allocates resources across subframes based on time-varying channel conditions.

54

Explain TCP/IP.

Reference answer

In a high-latency satellite link, file transfers crawled. Packet capture revealed small TCP windows and frequent retransmissions. By raising the window scale and enabling selective ACK, throughput tripled. Demonstrating deep TCP behavior, not just theory, is what makes answers to network engineer interview questions resonate.

55

What network engineering skills do you possess?

Reference answer

When answering this question, you could mention the more technical skills youâre equipped with, like your ability to troubleshoot hardware and software various types of network infrastructure issues as well as soft skills like organisational skills and your ability to manage projects on time. Hereâs one response: âI have the technical, analytical, and problem-solving skills to troubleshoot network problems and resolve issues quickly and efficiently with little to no downtime for the end user.â

56

What is the purpose of the TTI bundling in LTE?

Reference answer

TTI bundling transmits the same data over multiple subframes to improve coverage for voice services.

57

What does network topology dictate?

Reference answer

Network topology dictates what media you should use to interconnect devices. It also serves as a basis for selecting the materials, connectors, and terminations suitable for the configuration.

58

Can you describe a time when you had to resolve a major network outage?

Reference answer

In a previous role, we experienced a major network outage due to a misconfigured core switch. The outage affected multiple departments and critical services. I quickly identified the issue by reviewing configuration changes and network logs. I reverted the misconfiguration, restored connectivity, and conducted a thorough analysis to prevent future occurrences. I also communicated with stakeholders to keep them informed and implemented additional monitoring to detect similar issues early.

59

If there are 2 people standing at the same distance from a same cell tower and making a phone call at the exact same instant to their mutual friend. Their friend is at a different location connected to a different cell tower. Whose call will the receiver receive first? What will the basis of that?

Reference answer

Since both callers are at the same distance from the cell tower, the propagation delay is identical. The network processes both calls nearly simultaneously, and any difference in arrival time at the receiver would be negligible. If a choice must be made, it's practically random as modern networks are designed to ensure seamless and equal call delivery for both users.

60

What is the impact of DRX on real-time services?

Reference answer

DRX increases latency, which may affect real-time services like VoIP.

61

What are the different use cases supported by 5G NR?

Reference answer

5G NR supports different use cases like eMBB (Enhanced Mobile Broadband), URLLC (Ultra-Reliable Low-Latency Communications), and mMTC (Massive Machine Type Communications).

62

When would you use the FHSS technique, and when would you use the DSSS technique?

Reference answer

FHSS (Frequency Hopping Spread Spectrum) is used for robust, interference-resistant communication in noisy environments, while DSSS (Direct Sequence Spread Spectrum) is used for higher data rates and better performance in cleaner environments.

63

What does the E-UTRAN in LTE refer to?

Reference answer

E-UTRAN (Evolved Universal Terrestrial Radio Access Network) refers to the radio access network consisting of eNodeBs.

64

What is a DNS?

Reference answer

DNS stands for domain name system. Websites are accessed by their domain names such as google.com and yahoo.com. But these names are not understood by the computer. The DNS translates these names into IP addresses so that the browsers can load them for the users. DNS converts the hostname of the website into an IP address that is readable by the computer. The converting of hostnames into IP addresses is called forward lookup. Converting or resolving IP addresses into hostnames is called backward lookup.

65

How does ARFCN calculation differ between non-standalone (NSA) and standalone (SA) 5G deployments?

Reference answer

ARFCN calculation in NSA and SA deployments follows similar principles, but the specific frequency bands and carrier aggregation configurations may vary. Both deployments require accurate ARFCN calculation for effective spectrum utilization.

66

What does the Physical Layer do in the OSI model?

Reference answer

This is the lowest layer, and it deals with the physical connection between devices, such as cables, switches, and hubs. It's responsible for converting data into electrical signals and transmitting them over the network.

67

What is the backoff indicator, and when is it used?

Reference answer

The backoff indicator tells the UE to wait before retrying RACH after collision.

68

Define the difference between GBR and non-GBR bearers.

Reference answer

GBR bearers guarantee a minimum bit rate, while non-GBR bearers do not.

69

How Do You Evaluate The Security Posture Of Your Network? Discuss The Methodologies And Tools You Use For Penetration Testing And Vulnerability Assessments

Reference answer

This question is ideal for when you're trying to understand the candidate's expertise in network security and risk management. Answer sample: Evaluating the security posture of a network is a multifaceted process that requires a comprehensive approach. I employ various methodologies and tools for penetration testing and vulnerability assessments to ensure the robustness of our network security measures. One key methodology I use is penetration testing, which involves simulating real-world cyber attacks to identify potential vulnerabilities and assess the effectiveness of our defensive measures. I often conduct both internal and external penetration tests, leveraging automated tools like Metasploit and Burp Suite, as well as manual testing techniques to identify vulnerabilities that may evade automated scans. In addition to penetration testing, I regularly perform vulnerability assessments to proactively identify and remediate weaknesses in our network infrastructure. This involves using vulnerability scanning tools such as Nessus, OpenVAS, or Qualys to scan our network for known vulnerabilities in software, configurations, or system settings. These assessments provide valuable insights into areas of potential risk, allowing us to prioritize remediation efforts based on the severity and impact of identified vulnerabilities.

70

How does the RRC Connection Request message relate to the RACH procedure?

Reference answer

The RRC Connection Request is sent as message 3 in the RACH procedure.

71

Describe the overall structure of the 5G interface.

Reference answer

The overall structure of the 5G interface consists of the user plane, control plane, and management plane. The user plane handles data transmission, the control plane manages signaling and control information, and the management plane oversees network management and administration.

72

What is the use of the Control Resource Set (CORESET) in 5G NR?

Reference answer

CORESET defines the time-frequency resources for PDCCH transmission in 5G NR.

73

Describe the types of DRX timers in LTE.

Reference answer

DRX timers include onDurationTimer, drx-InactivityTimer, drx-RetransmissionTimer, and drx-Cycle.

74

Describe the sequence of steps in the LTE Attach process.

Reference answer

Steps: RRC setup, NAS attach request, authentication, security setup, bearer establishment.

75

What is a NOS?

Reference answer

I automated EOS upgrades via Ansible, backing up configs then staggering reloads to avoid downtime. That operational foresight aligns with the expectations behind NOS-oriented network engineer interview questions.

76

What is NAT and where is it commonly used?

Reference answer

NAT (Network Address Translation) is a networking technique that translates private IP addresses into a public IP address so devices can communicate with the internet. It helps conserve IPv4 addresses and improves network security by hiding internal IP addresses. NAT is commonly used in home routers, enterprise networks, and cloud environments where multiple devices share a single public IP.

77

Highlight the advantages of implementing 5G NR.

Reference answer

The adoption of 5G NR comes with advantages, shaping the future of communication Technology. Implementing 5G NR offers unparalleled speed, lower latency, and increased capacity, fostering innovation in diverse sectors. Enhanced Mobile Broadband, massive Machine-Type communication, and ultra-reliable low-latency communication open avenues for transformative applications, ranging from smart cities to autonomous vehicles.

78

What career goals do you have in the wireless network engineering space?

Reference answer

This question helps determine the candidate's long-term ambitions and alignment with the company's growth opportunities.

79

What network monitoring tools are commonly used and what features do they offer?

Reference answer

Expect candidates to mention software like SolarWinds, PRTG, and Nagios. Some key features they might talk about are: Network monitoring; Performance analysis; Traffic flow analysis; Alerting systems.

80

What triggers the RLF (Radio Link Failure) in LTE?

Reference answer

RLF is triggered by poor signal quality, T310 expiry, or maximum RLC retransmissions.

81

How do you handle network performance issues and optimization?

Reference answer

To handle network performance issues, I start by analyzing network traffic and identifying bottlenecks using monitoring tools. I then optimize configurations, such as adjusting QoS settings, load balancing traffic, and upgrading hardware if necessary. Regular performance reviews and proactive maintenance help ensure the network operates efficiently and meets performance requirements.

82

Describe the function of the Paging Indicator Channel (PICH).

Reference answer

PICH is not used in LTE; paging is indicated via PDCCH.

83

Define "preamble" in the context of LTE RACH.

Reference answer

A preamble is a sequence transmitted by the UE on PRACH to initiate random access.

84

Can you describe your experience with network automation and scripting?

Reference answer

I have experience with network automation and scripting using tools like Ansible, Python, and PowerShell. This includes automating routine tasks such as device configuration, software updates, and network monitoring. Automation improves efficiency, reduces errors, and allows for more consistent network management. I also develop custom scripts to address specific network needs and streamline operations.

85

Explain the function of GTP-U in LTE.

Reference answer

GTP-U (GPRS Tunneling Protocol-User) encapsulates user data packets for transport over the core network interfaces.

86

How does handover work in 5G?

Reference answer

- Measurement based (RSRP, RSRQ, SINR) - Events similar to LTE (A3, A5) - In NSA: LTE anchor controls mobility - In SA: gNB handles full mobility - Conditional handover (CHO) for improved mobility robustness

87

Describe the importance of ciphering in LTE.

Reference answer

Ciphering encrypts user and control data to prevent unauthorized access and ensure confidentiality.

88

How does the RACH assist with initial access?

Reference answer

RACH provides uplink synchronization and resource request for initial access.

89

What is NetFlow and how is it used?

Reference answer

NetFlow is a protocol for collecting IP traffic information. It provides visibility into traffic patterns and usage, helps identify traffic sources and destinations, and enables monitoring of bandwidth usage, detection of anomalies, and enhancement of network security.

90

Will 5G replace Wi-Fi?

Reference answer

The two technologies will probably coexist as network rollouts develop. Currently, 5G can replace Wi-Fi depending on the environment and coverage.

91

How does a longer cyclic prefix (T_CP) benefit RACH in fading environments?

Reference answer

A longer T_CP mitigates multipath delay spread, improving preamble detection.

92

What is the rate of the convolutional encoder for MIB?

Reference answer

The MIB uses a 1/3 rate convolutional encoder.

93

How does measurements work in LTE?

Reference answer

In LTE E-UTRAN measurements to be performed by a UE for mobility are classified as below - Intra-frequency E-UTRAN measurements - Inter-frequency E-UTRAN measurements - Inter-RAT measurements for UTRAN and GERAN - Inter-RAT measurements of CDMA2000 HRPD or 1xRTT frequencies

94

Explain how PRACH resources are allocated.

Reference answer

PRACH resources are allocated via the PRACH configuration index, defining time-frequency positions.

95

What is your experience in working with network protocols like TCP/IP, UDP, etc.?

Reference answer

This question will gauge the candidate's experience handling various network protocols, critical for seamless 5G network operations.

96

Describe LTE's approach to scheduling priority.

Reference answer

Scheduling priority is based on QCI, buffer status, and channel conditions.

97

When two UEs send an Initial RACH request at the same time, in the same slot, and with identical parameters, there can be two outcomes: The gNB rejects both RACH requests. The gNB selects one UE and rejects the other. In Case 1, it is clear that the gNB rejects both UEs. In Case 2, on what basis does the gNB select one UE and reject the other? How does the gNB make this decision?

Reference answer

Decision will be made at the gNB side. It may depend on many factors at both the gNBs. It's not very straightforward to answer. Depends on lot many factors, since decision will be at gNB side, factors like Call processing delay, allocation, scheduling. How fast CN is responding to each UE messages etc etc. At the instance of call there are ZERO issues in Network side( RAN, BH & CORE). MO Side- It depends on CBRA & CFRA process and UE Capabilities. MT Side- It depends on UE Mobility or Stationary RF conditions. Both UEs will send a sip invite message, it can be any UE which will be first in the IMS queue. There is no such thing as a message received at the same time there will be a delay at the second, micro second level In some queue. Either of their call will receive by receiver. A couple of factors from the physical layer perspective: 1. Network Latency: The paths taken by the calls through the network to reach the receiver's cell tower might differ. 2. Propagation Environment: Even if the callers are equidistant from their cell tower, environmental factors like signal interference, terrain, or obstructions could introduce tiny differences in propagation delay. Apart from that: 1. Call Setup Time: Each call involves a signaling process (e.g., setting up radio resources and establishing bearer paths). Variations in processing times at the caller's tower or the core network may introduce minor differences.

98

Describe the RACH preamble format for TDD mode.

Reference answer

TDD uses preamble formats 0-4, with format 4 for special subframes.

99

What is SON & how does it work in LTE?

Reference answer

Self-configuring, self-optimizing wireless networks is not a new concept but as the mobile networks are evolving towards 4G LTE networks, introduction of self configuring and self optimizing mechanisms is needed to minimize operational efforts. A self optimizing function would increase network performance and quality reacting to dynamic processes in the network. This would minimize the life cycle cost of running a network by eliminating manual configuration of equipment at the time of deployment, right through to dynamically optimizing radio network performance during operation. Ultimately it will reduce the unit cost and retail price of wireless data services.

100

Identify the primary components of the 5G Core Network (CN).

Reference answer

The 5G Core Network comprises the following key elements: a) Access and Mobility Management Function (AMF) b) Session Management Function (SMF) c) User Plane Function (UPF) d) Network Exposure Function (NEF) Each component plays a distinct role in managing network functions and ensuring seamless connectivity.

101

5G core major interfaces?

Reference answer

Major 5G core interfaces include N1 (UE-AMF), N2 (gNB-AMF), N3 (gNB-UPF), N4 (SMF-UPF), N6 (UPF-DN), N7 (SMF-PCF), N8 (AMF-UDM), N9 (UPF-UPF), N10 (SMF-UDM), N11 (AMF-SMF), N12 (AMF-AUSF), N13 (AMF-UDM), N14 (AMF-AMF), N15 (AMF-PCF), and N16 (SMF-SMF).

102

What is meant by the term "cell-specific reference signals"?

Reference answer

Cell-specific reference signals are used for channel estimation and measurements by all UEs.

103

SA and NSA mode operation

Reference answer

SA (Standalone) mode operates with a 5G core network and 5G NR (New Radio) access, providing full 5G capabilities. NSA (Non-Standalone) mode uses an existing LTE core and eNB as an anchor, with 5G NR added for enhanced data rates, allowing a gradual migration to 5G.

104

What are the core network components in 5G NR?

Reference answer

The 5G Core (5GC) includes key components such as the Access and Mobility Management Function (AMF), Session Management Function (SMF), User Plane Function (UPF), Policy Control Function (PCF), Network Slice Selection Function (NSSF), and Unified Data Management (UDM). These components support service-based architecture and enable functions like mobility, session management, and policy enforcement.

105

What is Sneakernet?

Reference answer

Sneakernet is believed to be the earliest form of networking where data is physically transferred using removable media, such as a disk or tapes.

106

What is latency in 5G?

Reference answer

Latency in 5G is as low as 1 millisecond (ms), which means there is very little delay in transmitting data over the network.

107

Explain the LTE system information blocks (SIBs).

Reference answer

SIBs broadcast system parameters, such as cell identity, scheduling, and access control, with SIB1 and SIB2 being essential.

108

What is the purpose of System Information Block Type 2 (SIB2)?

Reference answer

SIB2 provides common radio resource configuration, including RACH and timers.

109

Describe the purpose of the NG-U interface in 5G.

Reference answer

NG-U carries user plane data between gNB and UPF in 5G.

110

What happens if the eNodeB does not respond to the initial RACH request?

Reference answer

The UE retransmits the preamble with increased power after backoff.

111

How does the 5G interface support network slicing?

Reference answer

The 5G interface incorporates network slicing capabilities, allowing the partitioning of the network into multiple logical networks with different performance characteristics, catering to diverse service requirements.

112

Describe "standby mode" in LTE.

Reference answer

Standby mode is idle mode where the UE monitors paging and performs cell reselection.

113

Define the role of the MIB in initial UE attachment.

Reference answer

The MIB provides essential cell information for initial synchronization and access.

114

What does the RLF indication message do?

Reference answer

The RLF indication message informs the network of a radio link failure.

115

How do you troubleshoot and resolve issues with network latency?

Reference answer

To troubleshoot network latency issues, I use monitoring tools to identify the affected paths and measure latency. I analyze network traffic to identify congestion points, optimize configurations, and ensure that QoS policies prioritize critical traffic. Additionally, I review hardware performance and check for any misconfigurations or faulty equipment that could be causing delays.

116

What does an RRC message contain?

Reference answer

RRC messages contain control information for connection, mobility, and measurement management.

117

What is meant by "UE-specific beamforming"?

Reference answer

UE-specific beamforming directs the signal towards a specific UE, improving signal quality.

118

What are the main 5G frequency ranges?

Reference answer

- FR1 (Sub-6 GHz): 410 MHz – 7.125 GHz - FR2 (mmWave): 24.25 GHz – 52.6 GHz - FR3 (Mid-band): 7.125 GHz – 24.25 GHz (emerging)

119

What happens during X2 handover?

Reference answer

X2 handover involves direct signaling between source and target eNodeBs without MME involvement.

120

How does the RRC layer secure communication after attach completion?

Reference answer

RRC activates AS security using KeNB derived keys.

121

What is MCG? What kind of functionality it play in 5G NR?

Reference answer

MCG stands for Master Cell Group, in ENDC architecture the MCG node (MN) is LTE and SCG node (SN) is NR.* Please note that "node" here simply refers to a base station. Both nodes have a direct interface with the existing core network (EPC). * only master node has the direct interface towards EPC in the control plane that carries the signaling traffic between the mobile device and the core network. * The LTE node is responsible for maintaining the connection state transitions, handling the connection setup/release, and initiating the first-time secondary node addition, that is, the EN-DC setup. * The bearer became here called MCG bearer.

122

Explain the difference between NSA and SA architecture in 5G.

Reference answer

NSA (Non-Standalone) architecture uses existing LTE infrastructure for control signaling while adding 5G NR for data. SA (Standalone) architecture uses a 5G core network and 5G NR for both control and user plane.

123

What Is Port Aggregation And Why Would You Use It?

Reference answer

Port aggregation, also known as link aggregation or EtherChannel (Cisco terminology), combines multiple network connections in parallel to increase throughput beyond what a single connection could sustain or to provide redundancy in case one of the links fails. This technique is used to enhance network capacity and reliability, allowing for higher data rates and improved resilience by automatically redistributing load if a link goes down, thus ensuring continuous network operation.

124

Can you explain the role of DHCP in a network?

Reference answer

DHCP (Dynamic Host Configuration Protocol) is a network protocol that automatically assigns IP addresses and other network configuration parameters to devices on a network. DHCP simplifies network management by reducing the need for manual IP address configuration and ensures that devices can easily connect to the network with the correct settings.

125

Explain the concept of LTE layer 2 aggregation.

Reference answer

Layer 2 aggregation combines multiple carriers at the MAC layer for higher data rates.

126

How can wireless networks be protected?

Reference answer

Wireless protection is key to safeguarding confidential data. Passwords need to be strong (WPA2 and WPA3 encryption). Disabling SSID broadcasting reduces the network to hardcore scanners. MAC address filtering keeps other devices from connecting to your network Implementing a firewall is the second level of defence. Instead, Keep patching the firmware regularly to get rid of security holes. Putting guest networks separate from the main network removes clueless access. And we should never underestimate the importance of a security audit, in order for penetration testers help us identify any holes.

127

What's the biggest engineering challenge you have faced so far? How did you handle it?

Reference answer

This is a behavioral question. The candidate should describe a specific, real-world challenge, such as a major network outage, a complex migration, or a security breach. They should explain the situation, the actions they took (e.g., diagnosing the root cause, coordinating with team members, implementing a temporary fix, and deploying a permanent solution), and the outcome. The answer should demonstrate problem-solving skills, technical expertise, and the ability to work under pressure. For example, they might describe handling a DDoS attack by implementing rate limiting and filtering rules, or migrating a large enterprise network to a new architecture with minimal downtime.

128

What is the function of the drx-RetransmissionTimer?

Reference answer

The drx-RetransmissionTimer keeps the UE awake to receive HARQ retransmissions.

129

List three functions of the Packet Data Convergence Protocol (PDCP).

Reference answer

PDCP functions include header compression, ciphering and integrity protection, and in-order delivery of data packets.

130

Why sub carrier spacing is more for wifi than LTE

Reference answer

I think LTE support high mobility support compare to WiFi, which means LTE technology support you service even when you are moving with very high speed of the order of around 300Km/h. as we know as the high the mobility of channel less will be the coherence time ( high doppler shift), due to which we have keep sub-carrier spacing small for LTE.

131

What is a MAC address?

Reference answer

A MAC (Media Access Control) address is used for uniquely identifying a device on a network. Also called the physical address or ethernet address, MAC addresses are 48-bit numbers that are present in the NIC of the devices. This is an address given by the manufacturer of the device. The MAC sub-layer of the data link layer makes use of the MAC addresses. They are 12-digit hexadecimal numbers, where the first 6 digits identify the manufacturer.

132

Define LTE's "Paging Time Window."

Reference answer

The paging time window is the duration during which the UE monitors for paging.

133

Explain LTE paging load balancing.

Reference answer

Paging load balancing distributes paging across cells to avoid congestion.

134

What is the function of the Serving Gateway in LTE?

Reference answer

The Serving Gateway (S-GW) routes and forwards user data packets, acts as a mobility anchor during handovers, and buffers packets for idle UEs.

135

How does ARFCN calculation impact handover procedures in 5G networks?

Reference answer

Accurate ARFCN calculation is crucial for seamless handover between cells or base stations. It ensures uninterrupted communication and avoids disruptions during mobility scenarios.

136

Define DNS.

Reference answer

When our SaaS provider changed IPs without notice, users failed to connect. I reduced TTLs proactively during migration windows, then flushed caches during the switchover. The seamless transition highlighted foresight that scores well in network engineer interview questions.

137

Explain HARQ in LTE.

Reference answer

HARQ combines FEC and retransmissions to improve data reliability.

138

Explain the term "Cell-specific DL RS" in LTE.

Reference answer

Cell-specific downlink reference signals are used for channel estimation and measurement by all UEs in a cell.

139

What is 5G cell bandwidth, and why is it important in 5G networks?

Reference answer

5G cell bandwidth refers to the range of frequencies allocated to a 5G cell for communication. It is crucial in 5G networks as it determines the amount of spectrum available for transmitting data, which directly impacts network capacity, data rates, and overall performance.

140

How do you ensure compliance with industry standards and regulations in your network designs?

Reference answer

I stay updated with industry standards and regulations by regularly attending training sessions and reviewing compliance documentation. I also conduct periodic audits to ensure our network designs meet all necessary requirements, proactively addressing any potential issues.

141

Explain how the Timing Advance value is used in the RACH process.

Reference answer

Timing advance adjusts UE transmission timing to align with the eNodeB.

142

What is a tracert command?

Reference answer

The tracert command is used for displaying information about the path taken by a data packet to reach the destination network from the router. The total number of hops taken by the packet during the transmission is also displayed.

143

5G UE category types?

Reference answer

5G UE categories (e.g., NR FR1, NR FR2) define capabilities like supported bandwidth, MIMO layers, and modulation. Examples: Category 1 (low-end IoT), Category 2 (mid-range), Category 3 (high-end), with specific parameters per 3GPP Rel 15/16.

144

What is LACP and what are its benefits?

Reference answer

The Link Aggregation Control Protocol (LACP) combines multiple physical links into a single logical link, increasing bandwidth, providing redundancy, and balancing the traffic load across all available connections. This improves overall network performance, providing higher data transfer rates and robust fault tolerance, which is key for high-demand environments like data centers and enterprise networks.

145

What are some common network performance issues you have encountered, and how did you resolve them?

Reference answer

One common issue I've encountered is network congestion, which I resolved by implementing Quality of Service (QoS) policies to prioritize critical traffic. Additionally, I addressed latency problems by optimizing routing paths and upgrading network hardware.

146

Define the NAS EMM state machine.

Reference answer

The NAS EMM (EPS Mobility Management) state machine manages UE states like EMM-DEREGISTERED and EMM-REGISTERED.

147

Explain the difference between logical and transport channels in LTE.

Reference answer

Logical channels define the type of data (e.g., control or traffic), while transport channels define how data is transmitted over the air interface.

148

What is a subframe, and how long does it last in LTE?

Reference answer

A subframe is 1 ms long and consists of two slots, forming the basic scheduling unit in LTE.

149

What is beamforming in 5G?

Reference answer

Beamforming is a technique used in 5G networks to focus radio signals in specific directions, increasing signal strength, improving coverage, and enhancing network capacity.

150

Explain LTE's UL Power Control mechanism.

Reference answer

UL power control uses open-loop and closed-loop adjustments based on path loss and commands.

151

Describe the function of GTP-U in LTE.

Reference answer

GTP-U tunnels user data packets between eNodeB, S-GW, and P-GW.

152

What is an S1 bearer in the context of LTE?

Reference answer

An S1 bearer is a logical connection between the eNodeB and S-GW for user data transport.

153

How familiar are you with the architectural concepts and principles of 5G systems?

Reference answer

Understanding architectural concepts and principles is crucial in managing a 5G network. This question will test the technical knowledge of candidates.

154

What is Split Bearer in 5G NR? How's it works?

Reference answer

Split bearer is one of the finest technology which is introduced in 5g.* each node MN and SN have a additional bearer called Split bearer which is carry LTE as well as NR data and direct forward to relevant nodes. Now a question comes into mind how it's happen so without any doubt let's resolve this issue. Please refer below image. In above picture if you seen option3 and 3A MN receive data from epc and have a split bearer also that's have NR data which is directly forwarded to SN node via X2-U interface. In option 3x SN node (en-gNB) receive LTE data from epc and send it to LTE MN node (eNB) via X2-U interface.Now a another question here how layer works here: The answer is in below picture The MCG split bearer PDCP carry's the LTE and NR data. LTE data forward to LTE RLC and NR data forwarded to NR RLC layer. Same scenario follow in SCG split bearer, the SCG split bearer PDCP layer also carry's LTE and NR data which is also forwarded to respected RLC.

155

Outline the roles of MIB and SIB in the 5G framework.

Reference answer

Master Information Block (MIB) and System Information Block (SIB) play pivotal roles in 5G networks. MIB broadcasts fundamental information like cell identity and bandwidth, facilitating device synchronisation. SIBs, on the other hand, convey more detailed and dynamic information, allowing devices to optimise their connection parameters and efficiently utilise the network resources.

156

Describe how DCI is mapped to RNTIs.

Reference answer

DCI is scrambled with an RNTI (e.g., C-RNTI) to indicate the intended UE or function.

157

What is the function of TTI bundling in LTE?

Reference answer

TTI bundling improves coverage by transmitting the same data over multiple subframes.

158

What is NAT and how does it enhance security?

Reference answer

NAT (Network Address Translation) modifies IP addresses in packet headers while they transit through a router. It allows multiple devices on a local network to share a single public IP address for accessing the internet. It enhances security by masking internal IP addresses and conserves the number of public IP addresses needed.

159

How does PDCCH work in HARQ?

Reference answer

PDCCH schedules HARQ transmissions and retransmissions via DCI.

160

What is the function of LTE's RRC reconfiguration?

Reference answer

RRC reconfiguration modifies radio resources, mobility, and measurement settings.

161

How do switches work in a network?

Reference answer

Switches can connect two or more network segments. These are intelligent network devices that store information in their routing tables, like paths, hops, and bottlenecks. With this information, they can determine the best path for data to move. Switches work at the OSI Network Layer.

162

Explain the role of the Xn interface in 5G.

Reference answer

The Xn interface connects gNBs for handover and dual connectivity in 5G.

163

How does the eNodeB determine the paging occasion?

Reference answer

The eNodeB calculates the paging occasion based on UE ID and DRX cycle.

164

What is the role of the P-GW in an LTE network?

Reference answer

The P-GW provides connectivity to external networks, assigns IP addresses, and enforces QoS policies.

165

Describe LTE's data aggregation in MAC.

Reference answer

MAC aggregates data from multiple logical channels into transport blocks.

166

Do you have any questions for us?

Reference answer

This is usually the last question of your interview, and it's a good way to show your interest and knowledge of the company or organization you're interviewing with. Demonstrate your interest in the company by coming prepared with a few questions to ask or think about questions during the interview process that you'd like a potential employer to expand on. You may want to ask about how a network engineer fits into the company's overall goals, what the company culture is like, or questions about the company's role in its particular industry.

167

How does LTE use the PDCCH for HARQ?

Reference answer

PDCCH schedules HARQ retransmissions and carries ACK/NACK for uplink.

168

What is the range and speed in 5G NR technology?

Reference answer

- Speed: 5G networks are benchmarked to achieve speeds of approximately 20 Gbps in the downlink and 10 Gbps in the uplink as the network matures. Many operators have already reached throughputs around 5 Gbps. - Range: The range of 5G NR is generally shorter than that of 4G LTE or 3G networks, more comparable to Wi-Fi range.

169

How Do You Validate Throughput and Latency?

Reference answer

Throughput isn't just speed—it's protocol health. Discuss: Layer correlation Scheduling impact Packet loss Interviewers want analytical thinkers.

170

What is the role of eNodeB in paging?

Reference answer

The eNodeB transmits paging messages on PDSCH as instructed by the MME.

171

What Is DHCP, And Why Is It Used In Networks?

Reference answer

DHCP stands for Dynamic Host Configuration Protocol. It is a network management protocol used on IP networks whereby a DHCP server dynamically assigns an IP address and other network configuration parameters to each device on a network. This allows devices to communicate with other IP networks. DHCP is used to automate the process of configuring devices on the network, eliminating the need for manual IP address configuration, which can be time-consuming and prone to errors. By using DHCP, network administrators can ensure that devices are always given the correct IP settings, including subnet mask, default gateway, and DNS server information, facilitating a smooth and efficient network operation.

172

How does 5G support massive IoT deployments?

Reference answer

5G provides enhanced support for massive Internet of Things (IoT) deployments by offering low-power, low-cost, and wide-area coverage for a massive number of connected devices, enabling diverse IoT applications and use cases.

173

How is paging triggered in LTE?

Reference answer

Paging is triggered by incoming data or signaling for idle UEs.

174

What is 5G NR (New Radio)?

Reference answer

5G NR (New Radio) is the 5th generation cellular technology standard developed by 3GPP for broadband cellular networks. It operates at various frequency bands including below 6 GHz and above 6 GHz. 5G delivers higher data rates (up to 10 Gbps) and lower latency (<1 ms) than 4G LTE networks.

175

What is the role of the MME in handling UE states?

Reference answer

The MME manages UE states such as idle and connected, tracking location and initiating paging for idle UEs.

176

How does LTE use System Frame Numbers (SFN)?

Reference answer

SFN is used for timing reference, paging, and system information scheduling.

177

What is the role of the S1 interface in handover?

Reference answer

The S1 interface carries handover signaling between eNodeB and MME.

178

How do proxy servers enhance network security?

Reference answer

Proxy servers primarily prevent external users from identifying the IP addresses of an internal network. Without knowledge of the correct IP address, the physical location of the network cannot be determined. This data on IP addresses can help identify the network's location. Proxy servers can make a network invisible to external users.

179

What is the function of a Tracking Area Update (TAU)?

Reference answer

TAU updates the MME with the UE's current tracking area for paging and mobility management.

180

How do you approach documentation for network configurations and changes?

Reference answer

I use standardized templates to ensure consistency and clarity in documentation. Each configuration is accompanied by detailed descriptions and diagrams, and I regularly update the documentation to reflect any changes or improvements.

181

How do you start troubleshooting a wireless network issue?

Reference answer

This question assesses the candidate's systematic approach to diagnosing and resolving wireless network problems.

182

What is CS Fallback in LTE?

Reference answer

LTE technology supports packet based services only, however 3GPP does specifies fallback for circuit switched services as well. To achieve this LTE architecture and network nodes require additional functionality, this blog is an attempt to provide overview for same. In LTE architecture, the circuit switched (CS) fallback in EPS enables the provisioning of voice and traditional CS-domain services (e.g. CS UDI video/ SMS/ LCS/ USSD). To provide these services LTE reuses CS infrastructure when the UE is served by E UTRAN.

183

Can You Explain the OSI Model and How You Have Used It in Troubleshooting?

Reference answer

The OSI model has seven layers from Physical up to Application, and I use it as a troubleshooting framework every day. When users report connectivity issues, I start at Layer 1. Is the cable plugged in? Is there link light? Then I work my way up. Recently, we had users in one department lose network access. By working through the layers methodically, I found the issue at Layer 3. A routing table got misconfigured during maintenance, sending traffic to the wrong gateway. That systematic approach saved hours of guesswork.

184

Can network slices be dynamically altered or generated?

Reference answer

Yes, network slices can be dynamically altered or generated to adapt to varying demands. This dynamic nature allows operators to allocate resources based on real-time needs, ensuring efficient use of network resources and the ability to support evolving applications and services.

185

Can you describe a challenging network project you have worked on?

Reference answer

One challenging project involved migrating a large organization's data center to a new location while minimizing downtime. The project required meticulous planning, including network redesign, equipment procurement, and phased implementation. I coordinated with multiple teams to ensure seamless migration, conducted thorough testing, and provided support during the transition. The project was completed successfully with minimal disruption to business operations.

186

What are the benefits of EN-DC?

Reference answer

The benefits of EN-DC include improved coverage, reduced latency, and faster data speeds, as well as the ability to use 5G-specific features and applications.

187

Describe the concept of a mobility anchor in LTE.

Reference answer

A mobility anchor (e.g., S-GW) maintains the UE's IP address during handovers, ensuring session continuity.

188

Describe the purpose of the Public Warning Message (PWS) system.

Reference answer

PWS is used to broadcast emergency alerts, such as earthquake or tsunami warnings, to UEs in a specific area.

189

What is LTE's approach to resource block allocation?

Reference answer

Resource blocks are allocated via DCI using type 0, 1, or 2 allocation.

190

How do you troubleshoot RF issues?

Reference answer

This question evaluates the candidate's ability to diagnose radio frequency problems, including interference, signal degradation, and spectrum analysis.

191

Describe the HARQ process and how it is managed.

Reference answer

HARQ uses stop-and-wait processes with ACK/NACK feedback, managed by the MAC layer for retransmissions.

192

What's your experience with disaster recovery and business continuity planning?

Reference answer

I've been involved in DR planning from the design phase. The key questions I ask are: what's our RTO—how long can the network be down?—and what's our RPO—how much data can we afford to lose? For a financial services client, both of those were measured in minutes, so we designed with active-active redundancy and real-time replication. For less critical operations, we might have RTO measured in hours and use regular backups. Specifically, I've implemented redundant links between data centers so traffic can automatically failover. I've also worked on documenting recovery procedures and testing them regularly because a plan that's never tested doesn't work. We do a quarterly DR test where we actually fail over the network to the backup data center and measure how long services are down. Those tests have revealed issues we would have missed in a real crisis. One thing I learned the hard way is that having backups isn't enough—you need to test restoration regularly because I've seen situations where backups were corrupted and nobody knew until they tried to use them.

193

What is Wi-Fi?

Reference answer

I completed a predictive survey with Ekahau, adjusting AP placement to hit –67 dBm in all classrooms. Post-deployment metrics matched models, showcasing planning accuracy valued in network engineer interview questions.

194

What are the steps in contention-based RACH?

Reference answer

Steps: preamble transmission, random access response, scheduled transmission, and contention resolution.

195

Explain the difference between static and dynamic routing.

Reference answer

Static routing involves manually configuring the routing table with fixed paths for data packets. It's simple and secure but requires manual updates when network changes occur. Dynamic routing uses algorithms and protocols like OSPF or EIGRP to automatically adjust paths based on network conditions. It adapts to changes more efficiently but may be more complex to manage.

196

Explain the concept of CQI in LTE.

Reference answer

CQI indicates downlink channel quality, used for adaptive modulation and coding.

197

How many subcarriers are in a physical resource block in LTE?

Reference answer

A physical resource block in LTE consists of 12 consecutive subcarriers.

198

Explain the OSI model in simple terms.

Reference answer

The OSI model is a 7-layer framework that describes how data moves from one device to another across a network. Each layer has a specific role, from physical transmission to application-level communication, making it easier to design, troubleshoot, and understand network operations. Psychical, Data-Link, Network, Transport, Session, Presentation and Application are OSI model layers.

199

Explain NSA vs SA in 5G.

Reference answer

- NSA (Non-Standalone): - LTE core (EPC) - Faster rollout - Limited 5G features - SA (Standalone): - 5G Core (5GC) - Enables slicing, URLLC, low latency - Future-proof architecture - Enhanced network automation and management

200

Describe the role of gNB in 5G.

Reference answer

The gNB is the 5G base station that handles radio communication with UEs, similar to eNodeB in LTE.

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