5G NR network Architecture

Below is the 5G NR architecture as per 3GPP standard.

Network nodes and their functions:

(UE)- User equipment

(gNB)- Next Generation Node Base station

Access and Mobility Management Function (AMF) – responsible for following

       – Termination of RAN Control Plane interface (NG2)

       – Termination of NAS (NG1), NAS ciphering and integrity protection

       – Mobility Management

       – Lawful intercept (for AMF events and interface to Lawful Intercept System)

       – Transparent proxy for routing access authentication and SM messages

       – Access Authentication

       – Access Authorization

       – Security Anchor Function (SEA): It interacts with the UDM and the UE, receives the       intermediate key that was established as a result of the UE authentication process; in case of USIM based authentication, the AMF retrieves the security material from the UDM

       – Security Context Management (SCM): it receives a key from the SEA that it uses to derive access-network specific keys

User plane Function (UPF) – functions are

       – QoS handling for User plane

       – Packet routing & forwarding

       – Packet inspection and Policy rule enforcement

       – Lawful intercept (User Plane)

       – Traffic accounting and reporting

       – Anchor point for Intra-/Inter-RAT mobility (when applicable)

       – Support for interaction with external DN for transport of signaling for PDU session authorization/authentication by external DN

Session Management Control Function (SMF) – supports following:

      – Session Management

      – UE IP address allocation & management (including optional Authorization).

      – Selection and control of User Plane function

      – Termination of interfaces towards Policy control and Charging functions

      – Control part of policy enforcement and QoS.

      – Lawful intercept (for Session Management events and interface to Lawful Intercept System)

      – Termination of Session Management parts of NAS messages

      – Downlink Data Notification

      – Initiator of Access Node specific Session Management information, sent via AMF over NG2 to Access Node

      – Roaming functionality

      – Handle local enforcement to apply QoS SLAs (VPLMN)

      – Charging data collection and charging interface (VPLMN)

      – Lawful intercept (in VPLMN for Session Management events and interface to Lawful Intercept System)

Data Network (DN): Operator services, Internet access or other services

Authentication Server Function (AUSF) – Performs authentication processes with the UE

Unified Data Management (UDM) – Supports:

      – Authentication Credential Repository and Processing Function (ARPF); this function stores the long-term security credentials used in authentication for AKA

      – Storing of Subscription information

Policy Control Function (PCF) – Provides:

     – Support of unified policy framework to govern network behavior

     – Policy rules to control plane function(s) that enforce them

Application Function (AF) – Requests dynamic policies and/or charging control

Advantage of 5G NR(New Radio) over LTE

Recently 3GPP has shared the Non-stand Alone 5G NR(New radio) in Rel15. I would write an article on Advantage of 5G over legacy LTE.

Major Goals for 5G:- There are many targets that need to achieve in 5G NR but the most important is higher throughput(in Gbps) and low latency(<1ms). 

          Below are the some features which makes 5G better than LTE.

eMBB(Enhanced Mobile Broadband):- Just like 4G where we have eNodeB in 5G NR we have eMBB. eMBB is the throughput oriented part of 5G NR. It has following characteristics:-

    1. Peak Data Rates- 10 to 20Gbps
    2. 10000 times more traffic.
    3. Supports macro and small cells.
    4. Supports high mobility of about 500Kmph.
    5. Helps in Network Energy saving by 100 times.

URLLC( Ultra reliable low latency communication):- In 5G NR E2E latency is <1ms while in LTE having around 20-100ms  and sometimes >100ms in case of congestion. To decrease/Improve the latency in 5G NR we have a dynamic structure of carrier spacing where symbol length can change along with the slot length.

   carrier spacing supported in 5G NR are: 15,30,60,120 and 240Khz.

In LTE there are fixed two slots/Subframe(0.5ms) but in 5G NR no. of slots may vary with carrier spacing( max upto 16 slots/subframe with 4.4microseconds).

Bandwith:- 5G NR supports a single carrier of 275RBs compared to 100 RBs in LTE.

Massive MIMO:- Greater than or equal to 8*8 MIMO we can implement in 5G NR.

Asynchronous HARQ:- Since we are using a flexible symbol length in 5G NR it also introduces a HARQ PDSCH feedback timing indicator. Consider a below example:
   Since we have a slot length of 0.0625ms and suppose UE sends the ACK in N+4 slot then the overall time would be 0.0625*4=0.25ms. 
So above example will ensure that the URLCC target is achieved.