5G III

Question 1

What are the key communication changes with 5G?

Answer 1

The network functions are becoming software only

Network functions can be installed in compute nodes at the edge of the network

Development of new types of local access networks (and integrating existing ones)

Question 2

What are the main advantages of the 5G evolution?

Answer 2

Communication can be executed through dedicated networks

Local access networks can use carrier-grade network technologies

Network functions can be placed in different network locations

Question 3

How is the 5G system seen from a network functions perspective?

Answer 3

The 5G system is a distributed system

The 5G system is a software system

New mechanisms for ensuring the resilience and the security

Question 4

Why use a 5G system instead of a 4G one?

Answer 4

Network functions can be customized depending on the communication requirements

The system can use the infrastructure available at the location

The system can integrate with different access network
or the local access networks

Question 5

Describe the high-level functionality of a 5G system

Answer 5

Security (Data plane)

Access Control (Data plane)

Transparency to applications (Data plane)

Basic Connectivity (Data plane)

Authentication and authorization (Control plane)

Mobility Management (Data plane)

Question 6

What are the key 5G network principles?

Answer 6

Control-User Plane Separation (CUPS)

Modularized function design

Minimize the dependencies between access and core

Enable direct interaction between functions as much as possible

Support a unified authentication framework

Support capability exposure

Support concurrent access to local and centralized services

Question 7

Describe the network functions AMF

Answer 7

Represents the main control entity within the 5G system

Question 8

Describe the network functions SMF

Answer 8

Represents the separate management functionality for sessions

Question 9

Describe the network functions UPF

Answer 9

Represents the data plane functionality of the 5G System

Question 10

Describe the network functions PCF

Answer 10

Represent the policy-based functionality of the network

Question 11

How is session continuity achieved in 5G

Answer 11

Full session continuity: IP connectivity maintained regardless of UE mobility events

Break-before-make: The network instructs the UE to immediately reconnect and disconnects it.

Make-before-break: A new connectivity is established before the previous is release

Question 12

How is QoS achieved in 5G?

Answer 12

prioritizing traffic flows and providing preferential forwarding for higher-priority packets

Question 13

NAS

Answer 13

NAS: used to communicate with both the AMF (NAS-MM) and SMF (NASSM)

Question 14

NG-AP

Answer 14

NG-AP protocol interconnects the NG-RAN with the AMF and UPF

Question 15

GTP-U

Answer 15

5G AN will speak GTP-U towards the network

Question 16

State modes for UE and AMF

Answer 16

Registration Management state machine

Connection management state machine

No. 69

Question 17

Describe the integration of non-3GPP accesses

Answer 17

An interworking gateway enabling the anchoring of the non-3GPP networks into the 5G system

Question 18

What is the Service Based Architecture?

Answer 18

SBA represents a radical re-thinking of the packet core network towards an efficient micro-services architecture

Question 19

Compare the service-based architecture with the classic architecture

Answer 19

Classic Architecture

i. Based on telecom protocols
ii. Easy to develop starting from existing architecture
iii. Naturally integrating with the 5G RAN
iv. Easy to migrate and interoperate with LTE

Service Based Architecture

i. Based on optimized internet protocols
ii. Easy to interact with the service administrator and application functions
iii. Following the micro-services approach
iv. Using a uniform easy to automate protocol in the control plane
v. Maintains most of the complexity

Question 20

What are the Service Based Architecture specific network functions? Please describe them

Answer 20

Network Exposure Function (NEF): Provides the interworking with third party functionality

NF Repository Function (NRF): Acts as a network discovery function for dynamic network infrastructures

Network Data Analytics Function: Acts as a new insight component, taking pre-emption on events

Question 21

What are the interactions between network functions (services) in SBA?

Answer 21

“Request-Response” − Based on the producer-consumer model

“Subscribe-Notify” − Based on an event-based mechanism − May include implicit subscriptions

Question 22

SMS

Answer 22

SMS messages are passed through the N1 interface to the AMF

AMF will have to forward them to the SMSF which on its turn will forward them appropriately to the next hop

Question 23

location services

Answer 23

The Location Management Function (LMF) acquires location information with different granularity from the AMF

AMF receives the information on the location from the RAN (not from the UE!)

Question 24

Describe the RAN flexibility of 5G, which other accesses can be integrated, how does the integration look like for each

Answer 24

Fixed Wireless Access: Providing Fixed-like connectivity over the wireless access

OTT 5G: 5G networks are flexible enough to support as to be transported over other access networks

Non-3GPP accesses: The UE must be able to create NAS messages and transmit them through the available accesses

Integrated Access Backhaul: Intermediary CPE-like node proxying the connectivity for other UEs

Satellite direct access: Providing a Non-Terrestrial Network for 5G with gNB at Hub Location