1

The challenges of VoLTE Service Monitoring

LTE rollouts supported by TEMS around the world

Ensure QoE

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Currently no accepted standard for measurement, monitoring VoLTE Services

Ascom has defined a formal definition, implementation strategy to help Operations Covers issues related to EPC, IMS, Application Service

We will describe this solution in a number of short articles

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UnderstandTest Scenarios

VoLTE Service Monitoring Challenges

TEMS VoLTE Service Monitoring: The VoLTE Voice Call

Contents

1. Title

2. Contents

3. Introduction

4. 24 x 7 monitoring

5. SW and HW Layers

6. Multi-Layer Active Monitoring

7. TEMS Tracker: Adding Passive Monitoring

8. TEMS Tracker: VoLTE to VoLTE Calls

9. The Overview dashboard

10. The Test Case dashboard

11. The Test Run dashboard

12. Service Steps

13. Quality Metrics

14. Signal Flow

15. Diagnostics

16. Related Posts

17. Disclaimer

Copyright 2016, Ascom Network Testing Ltd 2

Introduction

#2 in a series of brief articles aboutthe challenges of VoLTE Service Monitoring.

There is currently no accepted standard for the measurement or monitoring of VoLTE Services, even though we believe that this is vital to assure the quality and reliability of such services - and to establish a framework for reliable comparison across implementations.

To this end Ascom has defined a formal definition and implementation strategy to help the Operations team solve a range of challenges, including issues related to EPC, IMS and the Application Server. We will describe this solution in a number of short articles.

This article describes the architecture of our solution and the VoLTE Voice Calltest case.

Copyright 2016, Ascom Network Testing Ltd 3

VoLTE Service Monitoring - 24 x 7

IMS Solution 2.7 for VoLTE, VoWiFi, RCS and VoB

Our VoLTE Service Monitoring Solution consists of a suite of test cases (described in a previous post), which is run to provide 24 x 7 monitoring of service availability and quality and additional diagnostics to investigate outages or other issues.

Test cases are run on a high-availability, multiply-redundant Cloud-based system with a 99.95% uptime guarantee, to maintain 24 x 7 operation.

Results are published in near-real-time to dashboards on a web portal with the same uptime guarantee and can be accessed from any compatible web browser.

Confidentiality is protected by physical security for the servers and user authentication for remote access; encrypted protocols and client IP whitelisting are also available to further secure remote access.

Test cases are run on TMM Agents using device simulation to emulate subscribers making and receiving VoLTE calls across the network, so testing is end-to-end.

Copyright 2016, Ascom Network Testing Ltd 4

The Agent: Software and Hardware layersTMM SW

agent

TMM HWagent

Test Suites

IMDN

CPIM

SMSoIP

L3 Radio

USSDoIP

L3 Radio

FEMTOCELL

L3 Radio

SIP Procedures

SIP

OMA DM

provisionXCAP

HTTP

TLS

IMS Procedures

RTP

AMR H.264MSRP

MEDIA Procedures

GSMA IR.92

(VoLTE)

GSMA IR.94

(Video over LTE)OMA SIMPLE OMA CPM

VoWiFiGSMA RCS

FEMTOCELL

Procedures

COM SERVER

(TMM) TEMS Monitor Master LTE ProceduresSRVCC

LAN adapter 2G/3G Modem 4G Modem

Test Cases

API Layer

Service Layer

Network Layer

Protocol Layer

Access Layer

PCC

Procs.

Gx App

Diameter

Base

Device/Client

Simulation

IPSec

Our Agents implement all these SW layers on top of a HW interface layer. By using an LTE modem to simulate a Smartphone we get optimum control, flexibility & low level access and a proven architecture refined by thousands of hours of testing.

Multi-Layer Active Monitoring

RTP

MRF

Mr

MME

S6a

Gm

S5/S8Uu S1-U

EnodeB

Rx ISC

EPC IMS

HSS

SGW PGW

PCRF P-CSCF S-CSCFTAS

TOOL SUT (System Under Test)

Rx

Gx

LTE

Emulated Interface

Internal Interface

Media Path

TMM

SW

1. UE simulationor real device

TMM

SW

Gx

Gm

TMM

SW

ISC

TEMS Monitor Master with IMS Agent runs on different Layers so it can test and monitor them all - to measure the reliability and performance of the many different Network Domains and Elements within the Network and help you identify any components that are failing in real time!

2. PGW simulation

3. IMS simulation

Copyright 2016, Ascom Network Testing Ltd 6

Emulated InterfaceInternal InterfaceMedia Path

TEMS Tracker: VoLTE to VoLTE calls

Element Service Metrics for MO and MT

Ascom TEMS Monitor MasterActive Agent

Call setup preconditions Call setup resources confirmation Call setup alerting Call setup answer Audio exchange Call release

Call setup time Audio POLQA score Audio average jitter Audio maximum jitter Audio minimum bit rate Audio average bit rate Audio maximum bit rate Audio packet loss rate

3rd PartyPassive Probe

Collect signalling related S11, Gm, Gx and Rx network interfaces Call trace

TEMS TrackerAnalysis of signalling collected by Passive Probing system

Call Routing (User1, PCSCF1, PCRF1, PGW1, MME1) MO and MT S11 LTE Tunnel Info S11 GTP Failure Cause Code S11 GTPv2 Qos info Gx Auth Info Gx Diameter Failure Cause Code L1 and L2 audio SDP Info L1 and L2 SIP Failure Cause Code L1 and L2 SIP Reason Header src audio RTP Info dst audio RTP Info

S11 GTPv2 Procedures Create Bearer Update Bearer Delete Bearer

Gx Diameter Procedures Auth Re-Auth Credit Control

L1 and L2 Call Start Time L1 and L2 Call Ringing/Progress Tim L1 and L2 Call Answer Time L1 and L2 Call Answer Confirm Time L1 and L2 Call End Tim

Ascom TEMS Monitor Master

IT Agent Subscriber profile within HSS database Subscriber profile within PCRF database

Analysis of Active Agent + Passive Signalling + Subscriber profile information

Automated Root Cause of Failure Analysis

Automated Service and Quality Degradation Analysis

Copyright 2016, Ascom Network Testing Ltd 8

The VoLTE to VoLTE Call test caseThe Overview Dashboard

Provides an availability summary and lists any issues for each service: IR.92, IR.94, IMS, & Supplementary Services

Displays service status by regionCopyright 2016, Ascom Network Testing Ltd

This summarises the status of the VoLTE Service, using results from all the VoLTE test cases:

Categorizes and lists all issues in the Failure Distribution table

Drill down to details of any service, period, test case, test run, or issue

9

The VoLTE Voice Call test caseThe Test Case Dashboard

Service availability over time when did the problem start?

Service availability per step where did the problem start?

Copyright 2016, Ascom Network Testing Ltd

Displays recent results for the selected (VoLTE Voice Call) test case:

Quality Metrics over time how well is the service operating?

VoLTE to VoLTE service status by region on a world map

10

The VoLTE Voice Call test caseThe Test Run Details dashboard

The Test Run Details dashboard displays details of a single test, including:

Copyright 2016, Ascom Network Testing Ltd

Subscriber details: network operator, MSISDN, IMS and bearer

Dependencies: the test cases run to support this test run: - LTE Attach, - IMS Entry Point Discovery, - IMS Registration and - IMS Subscription to Events

Links: to Radio Trace, IP Trace, and Audio files to download

Messages: information collected during this test run from a Passive Probe or CDR related to this scenario.

Root cause of failure: if there was an issue, an analysis of all the collected information designed to help identify what caused it.

Test Case Flow: a diagram of the test case steps, showing the message flow and status of each step. See Signal Flow

11

The VoLTE Voice Call test caseService Steps

The Agent monitors the most relevant Service Steps within each Test Case to help identify what is failing and affecting the customers Quality of Service:

Copyright 2016, Ascom Network Testing Ltd

Step 1: Call setup preconditions

Step 2: Call setup resources confirmation

Step 3: Call setup alerting

Step 4: Call setup answer

Step 5: Audio exchange

Step 6: Call release

Service Steps can be monitored from end to end or from the Network Interface layer - by using the new TEMS Tracker option

12

The VoLTE Voice Call test caseQuality Metrics

The Agent manages and measures independently 2 audio channels (in and out) for each Subscriber a total of 4 channels for each call and reports a range of Quality Metrics to measure the Quality of Service perceived by the customer:

Copyright 2016, Ascom Network Testing Ltd

Call setup time (ms)

Audio POLQA score

Audio average jitter (ms)

Audio maximum jitter (ms)

Audio minimum bit rate (kbps)

Audio average bit rate (kbps)

Audio maximum bit rate (kbps)

Audio packet loss rate (%)

Metrics can be combined or reported separately for each party in the VoLTE Call.

13

The VoLTE Voice Call test caseSignal