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 Call test case.

1. 1
The challenges of VoLTE Service
Monitoring
LTE rollouts supported by TEMS around the world
Ensure
QoE
Understand
Scenarios
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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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Understand
Test Scenarios
VoLTE Service Monitoring
Challenges
TEMS™ VoLTE Service Monitoring: The VoLTE Voice Call

2. 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

3. Introduction
#2 in a series of brief articles about
the 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 Call
test case.
Copyright 2016, Ascom Network Testing Ltd 3

4. 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

5. The Agent: Software and Hardware layers
TMM SW
agent
TMM HW
agent
Test Suites
IMDN
CPIM
SMSoIP
L3 Radio
USSDoIP
L3 Radio
FEMTOCELL
L3 Radio
SIP Procedures
SIP
OMA DM
provision
XCAP
HTTP
TLS
IMS Procedures
RTP
AMR H.264
MSRP
MEDIA Procedures
GSMA IR.92
(VoLTE)
GSMA IR.94
(Video over LTE)
OMA SIMPLE OMA CPM
VoWiFi
GSMA 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.

6. 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-CSCF
TAS
TOOL SUT (System Under Test)
Rx
Gx
LTE
Emulated Interface
Internal Interface
Media Path
TMM
SW
1. UE simulation
or 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

7. Emulated Interface
Internal Interface
Media Path

8. TEMS Tracker: VoLTE to VoLTE calls
Element Service Metrics for MO and MT
Ascom TEMS Monitor Master
Active 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 Party
Passive Probe
• Collect signalling related S11, Gm, Gx and Rx network interfaces
• Call trace
TEMS Tracker
Analysis 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

9. The VoLTE to VoLTE Call test case
The Overview Dashboard
• Provides an availability summary
and lists any issues for each service:
IR.92, IR.94, IMS, & Supplementary
Services
• Displays service status by region
Copyright 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

10. The VoLTE Voice Call test case
The 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

11. The VoLTE Voice Call test case
The 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

12. The VoLTE Voice Call test case
Service Steps
The Agent monitors the most relevant Service Steps within each Test Case to
help identify what is failing and affecting the customer’s 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

13. The VoLTE Voice Call test case
Quality 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

14. The VoLTE Voice Call test case
Signal Flow
This test case consists of six steps which generate this exchange of
messages:
Each step is monitored separately so that overall status and timings
can be broken down into more meaningful elements.
Copyright 2016, Ascom Network Testing Ltd 14

15. The VoLTE Voice Call test case
Diagnostics
This test case can detect a wide range of problems in each service step and
report them as detailed Warning or Error Messages:
• A Warning Message describes a problem that may affect performance but
may not be noticed by customers; it could indicate an opportunity for
improving efficiency or the early stages of a more serious problem.
• An Error Message describes a failure, a serious problem that was detected
and will be noticed by customers.
You can configure the system to raise an Alarm for specific warnings or errors,
reporting them via emails or SNMP traps.
Copyright 2016, Ascom Network Testing Ltd 15

16. VoLTE Service Monitoring – Related posts
Articles:
• Day 1. VoLTE Service Monitoring
• Day 2. How critical is the VoLTE Service for my company?
• Day 3. New generation VoLTE Service Monitoring solution
• Day 4. I already monitor LTE, so I must be good for VoLTE?
• Day 5. Monitoring VoLTE Customer Experience
• Day 6. how can you uncover hidden areas of your VoLTE network and services to
deliver the customer experience you really want?
Check the VoLTE Service Monitoring posts for links to subsequent articles.
TEMS VoLTE Service Monitoring solution:
1. A New Standard & the Test Cases Overview
2. Solution architecture & the VoLTE Voice Call test case
Additional details will be published every 1-2 weeks to describe this proposal, including test case flow,
metrics, diagnostics and reporting.
Copyright 2016, Ascom Network Testing Ltd 16