VoLTE KPIs

Today we will discuss about the Various types of VoLTE KPIs. 
VoLTE KPI is mainly divided into three parts:

1.IMS KPI

2.EPC(Packet core) KPI

3.RAN KPI.


IMS KPI is further divided into 2 parts:- IMS Control plane KPI and IMS User Plan KPI.

IMS Control plane KPIs are as follows:

1.RSR:- Registration success rate.         

Formulae = Count of 200OK for Registration completed/Count of SIP register sent from UE excluding 401 error attempts*100

2.CSSR- Call setup success rate%           

Formulae = Count of (Normal end call+ call failed with user behaviour)/Sum of all call attempts*100

3.Call setup time:-          

Formulae= Avg of(Time(180 ringing)- Time(SIP INVITE request))


IMS User plane KPIs are as follows:

1.Mute rate(%)

Formulae= % of calls muted (samples >2 or 5s RTP loss in both direction)

2.MOS score

3.RTP packet loss %

Formulae = % of RTP packets lost in the uplink or downlink direction.

4.One way call %

Formulae = % of calls having no voice packets count for 2 or 5 Sec in either the downlink or uplink direction.


EPC(Packet core KPI):- This also classified further in 2 parts- MME generated and SGw/PGw generated.

MME generated KPI are as follows:-

1.VoLTE attach success rate% = % of PDN connect request responded successfully by MME for IMS APN.

2.VoLTE bearer Activation success rate:% of create request got successful.

3.Paging success rate%-= % of paging responses on QCI=5 received at MME.
SGw/PGw generated KPI are as follows:-
1. IMS IP Pool Utilization%


RAN KPI are as follows: 
1.Call drop rate % = % of calls getting dropped abnormally.
2.SRVCC Success Rate % = % of calls successfully transferred with SRVCC from VoLTE to legacy NW

3.Handover Success rate %(S1 and X2).

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