scinetific presentation

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1
E2E Volte optimization- Offerings & Capabilities
Planning & implementation
1
KPIs
3
Challenges of implementation
4
Testing & Tools
2

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2
Introduction to VOLTE
 LTE is a packet only architecture designed to improve data performance. It does not support CS voice or video call.
 In order to accommodate voice on LTE, two approaches were taken i.e. CSFB(Circuit Switch Fall Back) and Volte.
 GSMA – Voice over LTE has evolved as the preferred standard for telephony solution in LTE that has been accepted by
the operator community.
 GSMA has defined Voice over LTE (Volte) in describing minimum set of requirements for delivering voice in an all IP
environment based on existing 3GPP IMS based multimedia telephony solution.
LTE Voice Solutions
Voice and Data Services
Provided
By the LTE Network
Data Services Provided
By the LTE Network and
Voice Services Provided
By the CS Network
IMS/SRVCC(Voice Solution Provided by IMS and Data by LTE
EPC.LTE Subscribers can Roam on 2G/3G network by SRVCC
Voice Services are Provided by OTT(Over the Top Content
Delivery of Audio and Video Over Internet with help of ISP)
Carrier
Voice Services Provided by CSFB (Subscribers Fall back to
Traditional 2G/3G Networks)
SVLTE: Dual Radio Terminals are required ,the 2G/3G
Network Provides Voice services and LTE Provides data

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VoLTE Phase-based Deployment Policy(Planning)
LTE
LTE
2G/3G
LTE
2G/3G
LTE
2G/3G
Phase 2:
Continuous LTE coverage
Phase 1:
Hot spot LTE
coverage
Phase 3:
Full LTE coverage
Pre-VoLTE Initial commercial use Large-scale commercial
deployment
 Terminals:
 Initial smartphone
 LTE data card and LTE
CPE(Customer premises
equipment (CPE)
 Deployment suggestions:
 CSFB
 CPEs subscribe to IMS-based
VoIP voice services.
 Soft clients subscribe to rich media
RCS services(Rich
Communication
Services) program is a GSM
Association (GSMA) .
 Terminals:
 Smartphone
 LTE data card and LTE
CPE(Customer premises
equipment (CPE))
 Deployment suggestions:
 IMS-based VoLTE voice services
 eSRVCC
 Convergent database SingleSDB
 LTE-based rich media RCS
services
 Terminals:
 Smartphone
 LTE data card and LTE
CPE(Customer premises
equipment (CPE))
 Deployment suggestions:
 The LTE network becomes the
mainstream.
 ICS(IMS Centralized Services)
 IMS roaming and interworking

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Overview of the Data collection Using Wireshark and
TEMS Discovery
TI
Logs
MME
Traces
collected 1) TI-Logs are Terminal Logs or UE Logs Collected during drive test and Analyses Using Tems Discovery Like
RRC Failure Analysis and L3 Message Analysis
2) 2)As a Part of Enode B Performance Analysis Wireshark Logs Collected at MME on S1 AP,X2 AP to
analyse the Performance issues happening on SIP protocols to identify UE and ENodeB Performance
issues

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High level Troubleshooting Guide For Performance
Analysis Collect Data
Analyze UE Layer 3
RF
Correlation
Found?
Correlate with Traces Evaluate in detail
Evaluate SIP Log
IMS
Correlation
Found?
Evaluate in detail
Potential MME/EPC
Issue?
RAN
ISSUE
CORE
ISSUE
Cascade to E2E Team
YES
NO
NO
YES
 Trouble Shooting to Improve Volte Performance are done Via Drive Test Logs an Logs Collected at MME
 Access ability and Retain ability are two main KPIs for LTE Layer 3 Analysis. Tems Discovery Volte report also
provides LTE RRC KPIs like RRC Setup Failure Rate, RRC Setup Attempts, RRC Setup Complete, RRC Drop Rate,
RRC Calls Successfully Completed, RRC Drops, etc.
 Wireshark Logs an Helps to Find out NON-RF issues like SIP Protocols Issues, Core Network Issues

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VOLTE Log Analysis Using Wireshark(SIP Messages)
UE Registration with IMS
The Above Snap shows the analysis of Packet Capture for SIP Messages done on ENodeB to MME S1 –AP Interface analysis done
using wireshark.The Log shows the UE is Registered in Volte Domain(registered with IMS) and IMS AKA-
Authentication(Authentication and Key Agreement) has been Completed by Core Network and UE is Ready to make Volte Calls

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RRC(L3) Analysis Procedure from Tems Discovery
The Above Snap shows the analysis of UE logs collected during drive test and analyzed using Tems discovery, the L3 analysis above
shows that the UE is started reading the System Information messages and ready for registration to LTE network

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LTE/VOLTE COUNTER KPI’S & THRESHOLD
LTE Counter KPI'S for 10 MHz KPI Target
% Accessibility >99%
% Retainability > 99 %
% HOSR
> 98.5 %
% IRAT Rate < 1%
DL Throughput (Mbps) > 11
UL Throughput (Mbps) > 5
CSFB Succ Rate > 98.5 %
VOLTE Counter KPI'S KPI Target
% Accessibility
QCI1
>99%
% Retainability
QCI 1
> 99 %
% HOSR
QCI1
> 98.5 %
%SRVCC Succ Rate > 98.5 %
LTE OSS KPI’s Volte OSS KPI’s
VOLTE Drive KPI KPI Threshold
VOLTE MO Accessibility >99%
VOLTE Retainability >99%
VOLTE MO Retainability >99%
VOLTE MT Retainability >99%
VOLTE MO Voice Setup
Time
<8.5 sec
VOLTE MT Voice Setup
Time
<3.5 sec
% of Samples with
MOS>2.1
> 98 %
% of call stayed on VOLTE >96%
VOLTE Drive Scenario
MS1 LTE_Scanner
MS2 Long Call DL (DO only)
MS3 Long Call UL (DO only)
MS4 MO CSFB Call
MS5 MT CSFB Call
MS6 VOLTE MO UE
MS7 VOLTE MT UE
Volte Drive Test KPI’s

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VOLTE OPTIMIZATION(Drive Test and OSS Statistics)
 Volte Performance can Analysed by Drive Test data and OSS Statistics
 The purpose of VOLTE drive test is to evaluate the coverage and performance of a network for voice call services. The Major VOLTE
drive test parameters are as RSRP, SINR, DL RSSI, MOS Score, RSRQ, UE TX Power etc.
 Techmahindra has to perform few basic checks with drive logs and parameter audit sheets like : Site are not radiating or radiating
with poor footprint, Antenna Swap, MIMO Swap, PCI Collision, Alarms, UL RSSI, VSWR, Cell Status, eNodeB Power and check for
Parameter.
 Session setup success (Accessibility), session completion failure (Retainability) and SRVCC success rate are two main KPI’s for analysis
from Drive Test data and OSS Stats
 With the help of drive test data and OSS Stats, Techmahindra can check below points:
– Coverage footprint of sites
– Accessibility
– Retain ability
– Mobility
– Quality
– MOS Score
– SRVCC
 If Any degradation in any drive KPI, then has to find out RCA and has to provide solution as per specific problems. Please find some
basic troubleshooting and recommendation for improvement of drive KPI in next slide:
 SRVCC - SRVCC is the Main KPI which needs to be Optimized when there is no Volte Coverage When the handset leaves the LTE
coverage area, then VOLTE connection can be handed over to a CS connection in a legacy network. This procedure is called SRVCC
(Single Radio Voice Call Continuity). If LTE coverage is extensive, then SRVCC probability is Low. It is beneficial to have a low SRVCC
probability to gain full benefit of VOLTE.
If SRVCC issue observed, need to check for A2 and B2 thresholds of QCI 1. Check for neighbor relations for SRVCC with legacy network

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VOLTE OPTIMIZATION(Flow Chart for Accessibility)
START
Call Access Failure?
Yes
HW Fault /Down Time?
Check Hardware Fault (RRU, Neighbor Cell fault or down),
Check current alarm, History & Activity logs
Yes
NO
is Accessibility fail to
Due o High/LOW RSSI
Yes
Check Media, S1 continuity, Tempoint status.
NO
Is Fails due to Poor
RF
Check PCI Collision, Interference (UL RSSI), overshooting and Hardware
As Fails due to
Congestion?
Yes
Try to offload Cell/Site, Apply Layer management strategy if multicarrier carriers
available, Apply Hi Cap settings & Do possible Physical Optimization.
Fails due to Other
Reasons?
Check for any Non RF Ready Or Pre launch sites nearby, Check layer management
strategy for Multicarrier sites, need to check core Network issues by UE traces or
MME traces analyzed using Wireshark.
END
Yes
Identify Poor RF Coverage, Check CQI & Power Limitation. Recommend Physical
Optimization of cells or Propose New Coverage sites. Check for faulty antenna,
High VSWR, damaged cables or connectors.
Yes
Tx Fault?
NO
NO
NO

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VOLTE OPTIMIZATION(Flow Chart for Retainability)
START
Call Drop?
Yes
No
HW Fault /Down Time?
Check Hardware Fault (RRU, Neighbor Cell fault or down),
Check current alarm, History & Activity logs
Yes
NO
Is Drop due to HO Fail
Or High UL RSSI?
Yes
Check Media, S1 continuity, Tempoint status.
NO
Is Drop due to Poor
RF
Check PCI Collision, Interference (UL RSSI) on target cell, overshooting Check UL
RSSI on cell. High Interference cause drops.
Is Drop due to
Congestion?
Yes
Try to offload Cell/Site, Apply Layer management strategy if multicarrier carriers
available, Apply Hi Cap settings & Do possible Physical Optimization.
Drops due to Other
Reasons?
Check for any Non RF Ready Or Pre launch sites nearby, Check layer management
strategy for Multicarrier sites, need to check core Network issues by UE traces or
MME traces analyzed using Wireshark.
END
Yes
Identify Poor RF Coverage, Check CQI & Power Limitation. Recommend Physical
Optimization of cells or Propose New Coverage sites. Check for faulty antenna,
High VSWR, damaged cables or connectors.
Yes
Tx Fault?
NO
NO
NO

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VOLTE OPTIMIZATION(Flow Chart for Mobility )
START
Poor HO Preparation
Yes
NO
NO
Overshooting
Yes
END
NO
Incorrect Parameter setting
in Target
Term point to MME missing on target cells. Check if all MME link is working if MME is
in Pool.
Check for Overshooting cells with drive plots/Prach Report ,Recommend Physical
Optimization of these cells and parameter optimization to restrict the Cell
footprint. Propose Coverage optimization for sites having coverage holes.
Target cell might be loaded
Handover preparation may fail because the target eNodeB cannot provide the
necessary resources for the handover during congestion or cannot interpret the
contents of the handover request message. Check Ho Parameters and Call traces
with log analysis to check the incorrect parameter
NO
Alarm in the target
Check for X2Failure alarm or S1 Failure alarm in
The target cell
Yes
Yes
NO
NOO
Yes
NO
Collectogs on X2 and S1
AP
Analyse using Wireshark and check for the Cause

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S. N Problem Description Troubleshooting Solution
1 TX Imbalance
If Both the Tx branches of Antenna or
RRU are not dominant in same
direction, it is refered as Tx Imbalance,
(Difference between two TX branches
< 10db).
It can we verified with scanner Tx1 & Tx2
RSRP plot in Tems discovery to see that the
difference between TX1 and TX2 rsrp should
not exceed 10db.
Inform customer so that the tower
crew can be sent to site for
rectification.
2 Feeder Swap
Feeder cables are physically
incorrectly connected between the
RRU and Antenna.
PCI plot need to be checked on Tems
discovery to see if the sectors are radiating in
the expected direction.
Inform customer so that the tower
crew can be sent to site for
rectification.
3 Azimuth Issue
If existing orientation of antenna are
different from the designed azimuth.
PCI distribution need to be check in PCI Plot.
PCIs are shifted either clockwise or anti
clockwise with respect to the azimuths
Inform customer so that the tower
crew can be sent to site for
verification.
4
Accessibility
Issue
Poor Accessibility observed during
Drive Test
Need to Check PCI collision. Check for UL
RSSI, Check for coverage, check for Alarm,
check for License capacity. Check for SIP
call flow, there can be several reason
observed from SIP messages.
Fix the problem after implementation
of recommendation on the basis of
analysis.
5
Retainability
Issue
Poor Retainability observed during
drive test
Check for coverage, Check for PCI collision,
check for UL RSSI, check for handover
parameters. Check for SIP call flow. If there
is no RTP packet for 10 sec then it will
pegged a drop.
Fix the problem after implementation
of recommendation on the basis of
analysis.
6 HO Failure
During the mobilty test when UE tries
to Handover from one PCI to another
PCI and it got failed.
Need to check the neighbor definition and
check for ANR parameters as well.
Need to check the basic Handover
Parameters.
Fix the problem after implementation
of recommendation on the basis of
analysis.
7
MOS Score
Issue
Poor MOS Score (<2.1)
Need to check RF conditions. Check for UL
RSSI, Alarms, VSWR and verify for codec
rate etc.
.
Fix the problem after implementation
of recommendation on the basis of
analysis.
VOLTE OPTIMIZATION CASE STUDIES during Drive Test

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Challenges To Deploying VoLTE
The “flipside” of being able to deliver voice and data over one network is that those networks must now be optimized for both voice
and data. Delivering high-quality voice is more challenging, and doing so in the form of data packets even more so.
Aside from the sheer novelty of this undertaking, VoLTE involves lots of new moving pieces, unproven technologies, and
interdependencies. Major challenges to ensuring successful
Deployments out of the gate include:
 Validating New Devices and Configurations
By 2016, ARC Chart expects the installed base of Volte-enabled handsets to top 74 million. Such devices are already available in Korea and other
countries leading adoption. Expects to see many more devices available in many more countries by the end of 2014, and
all of these new devices need to be evaluated for performance, interoperability, and reliability.
 Interoperability in Increasingly Multi-vendor Environments
the interfaces involved in Volte are also prone to customization by vendors, including critical Diameter protocols used in the EPC core, and
Session Initiation Protocol (SIP) implementations within IMS.
 Signaling
Spikes in hard-to-predict signaling traffic are already occurring due to smartphones generating up to 20x the signaling traffic of traditional
phones. Signaling volumes may actually overwhelm infrastructures, leading to costly and embarrassing outages.
 Fallback
Volte is not a forklift upgrade; it’s a whole new deal. Until every mobile phone in use supports it, operators will need to support legacy air-links and
provide seamless fallback to 2G/3G networks where LTE is unavailable.
 Ensuring Quality of Experience (QoE)
For Volte to be worth the formidable investment, it not only has to deliver better quality than what OTT players provide, but exceed what 2G/3G
networks deliver as well. Early indicators
 Impact on value-added services
What impact will increased complexity have on features like Call Waiting, forwarding, voicemail, and conferencing? In migrating voice to LTE,
operators need to be sure subscribers’ satisfaction with the features they’ve come to rely on won’t be compromised
 Stress / Scalability
Does voice get prioritized effectively as the network become stressed? Where are the new bottlenecks and congestion points? What happens
when failovers occur? QoS and reliability must be assessed under realistic load and high-stress conditions to ensure satisfaction and bring high-risk
surprises to light before they do damage.

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VOLTE – Key Optimization CHALLENGES
Metrics Characteristics impacting VoLTE KPIs Impacted
HO Performance
HO interruption time > 200 ms
HO Oscillation – In poor RF conditions/cell edge
Delayed/dragged HO – Slow fading signal
HO failures
Retainability
Accessibility
MOS Score
DL SINR
Degraded SINR - < 5 dB
High traffic sites impact overall DL SINR
SINR degradation during dragged HO – Intra/Inter
Frequency
Retainability
Accessibility
MOS Score
Multi-RAB throughput &
MBB Throughput
Core/IMS Issues
Packet loss and jitter – Non RAN related
Systemic Issues – Control Plane related
Functional aspects
Retainability
Accessibility
MOS Score
Call set up time
UL RSSI
UL RSSI > -110 dBm
High packet loss
Consistent RACH failures
Retainability
Accessibility
MOS Score
Coverage/RSRP -
SRVCC
Low RSRP levels
Fall back to UMTS – impacts perceived end user call
quality
MOS Score
Retainability