5G Network Architecture


Introduction 

The exponential growth of wireless data services driven by mobile Internet and smart devices has triggered the investigation of the 5G cellular network. Around 2020, the new 5G mobile networks are expected to be deployed.

5G networks will have to support multimedia applications with a wide variety of requirements, including higher peak and user data rates, reduced latency, enhanced indoor coverage, improved energy efficiency and so on.

5G Converged Architecture

5G promises ubiquitous wireless coverage.

Radios leveraging licensed and/or unlicensed spectrum, small cells, macro LTE eNodeBs, fiber, microwave, leased Ethernet, or satellite backhaul will be considered when offering services.

Given the service performance requirements, it is possible that not all services will be available in all areas of ubiquitous coverage.

It will be essential to maintain continuity, as devices change locations and move between different types of networks.

5G Network Architecture

The 5G-RAN will include both a 5G New Radio (currently being called a (gNB) and/or LTE Radios (eNBs) connected to the Next Generation 5G Core (NG Core). 

The gNBs and/or eNBs provide the user plane and control plane protocol terminations towards the UE. 

5G Architecture Options

  • Two Radio technologies have to be considered in the 5G discussions
  • LTE (in its Rel-15 version).
  • Next generation Radio (“NR”)
  • Two Core Network concepts have to be considered in the 5G discussions
  • EPC (with potential evolution)
  • Next Generation Core (“nGCN“)


5G Core Network

  • The 5G NGC architecture is defined as service-based and the interaction between network functions are represented in two ways:

          – Network functions within the 5G Control Plane (5GC).

          – Network Functions connecting to the 5G Control Plane from the RAN network.

  • Network Functions within the 5G CP shall only use service-based interfaces for their interactions. This is different than LTE architecture where all of the core has a reference point representation.
  • Reference point interfaces will continue to exist within the Radio and User Plane (UP).
  • In addition to SBA, two other new concepts have been included: Control Plane / User Plane (CP/UP) split; and Network Slicing.

CORE NETWORK FUNCTIONS

#Authentication Server Function (AUSF)

  • Contains mainly the EAP authentication server functionality.
  • Storage for Keys Core.

#Access and Mobility Management Function (AMF)

  • Termination point for RAN CP interfaces (N2).
  • UE Authentication & Access Security.
  • Mobility Management (Reachability, Idle/Active Mode mobility state handling).

#Data Network (DN)

  • Services offered

          o  Operator services.      o Internet access.          o 3rd party services.

#Network Exposure Function (NEF)

  • Provides security when services or Application Functions (AF) access 5G Core nodes.
  • Can be thought of as a proxy, or API aggregation point, or translator into the Core Network.

#NF Repository Function (NRF)

  • Provides profiles of Network Function (NF) instances and their supported services within the network.

#Policy Control Function (PCF)

  • Expected to have similarities with the existing policy framework (Policy and Charging Rules Function – PCRF) in 4G.
  • Updates to include the addition of 5G standardized mobility based policies

#Session Management Function (SMF).

  • Idle/Active aware.
  • UE IP address allocation & management .
  • Policy and Offline/Online charging interface termination. 

#Unified Data Management (UDM)

  • Expected to have similar functionality as the HSS in Release 14 for the Evolved Packet Core (EPC).

#User Plane Function (UPF)

  • Allows for numerous configurations which essential for reduction of latency in 5G.
  • Anchor point for Intra-/Inter-RAT mobility.
  • External IP point of interconnect.
  • Packet routing and forwarding.
  • QoS handling for User Plane.

#Application Functions (AF)

  • Services considered to be trusted by the operator .
  • Can access Network Functions directly or via the NEF.

4G to 5G Networks : Expected Evolution

Summary

• 5G will address enhanced Mobile Broadband (eMBB), Ultra-Reliable Low Latency
  Communications (URLLC) and massive Machine Type Communications (mMTC).
• 5G requires a new network architecture.
• The functional decomposition of the RAN results in DU and CU network elements.
• Next Generation Core network can be grouped into two functional blocks CPF and UPF.
• Some RAN functionality will move towards the core whilst the core will move towards the RAN.
• Small cells are an essential component of 5G.
• URLLC is an overlay and requirements will vary based on use cases.

#References

  • 3GPP TR 23.501 
  • Nokia.
  • 5G on the horizon: Key challenges for the radio-access network,” IEEE Vehicular Technology Magazine.
  • Towards converged 5G mobile networks – Challenges and current trends.
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