Whitepaper

VoLTE/VoWi-Fi: Crucial deployment

and assurance considerations for

operators

March 2015

Anil Rao

VoLTE/VoWi-Fi: Crucial deployment and assurance considerations for operators | i

© Analysys Mason Limited 2015 Contents

Contents

1. Executive summary 2

2. VoLTE uptake will increase with LTE but the business case remains unclear 3

The current state of LTE 3 2.1

VoLTE forecast 3 2.2

The cost of deploying IMS and technological complexity are inhibitors 4 2.3

3. Operators must get it right first time 5

VoLTE increases network complexity and presents new assurance challenges 5 3.1

Vigorous pre-launch service validation testing can mitigate the risks 6 3.2

IP probes will be crucial for assuring VoLTE post-launch 6 3.3

4. Operators should focus on a holistic customer experience 7

Deploy advanced analytics and service management applications to measure end-to-end QoS 7 4.1

Compensate for poor coverage with small cells and VoWi-Fi 7 4.2

5. Vendor solution overview – Polystar Group 8

Network and Customer Insight solutions 8 5.1

Solver 9 5.2

ODIN 10 5.3

About Analysys Mason 11

About Polystar Group 12

List of figures

Figure 1.1: VoLTE challenges [Source: Analysys Mason, 2015] .................................................................... 2

Figure 2.1: LTE connections forecast [Source: Analysys Mason, 2015] .......................................................... 3

Figure 2.2: VoLTE connections forecast [Source: Analysys Mason, 2015] ..................................................... 4

Figure 2.3: Current state of VoLTE launches [Source: Analysys Mason, 2015] .............................................. 4

Figure 5.1:Polystar solution [Source: Polystar, 2015] ...................................................................................... 8

Figure 5.2: Validation test methodology [Source: Analysys Mason and Polystar, 2015] ................................ 9

Figure 5.3: ODIN pre-IMS [Source: Polystar, 2015] ...................................................................................... 10

Figure 5.4: ODIN post-IMS [Source: Polystar, 2015] .................................................................................... 10

Analysys Mason does not endorse any of the vendor’s products or services discussed in this whitepaper.

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© Analysys Mason Limited 2015 Executive summary

1. Executive summary

Voice over LTE (VoLTE), the next-generation voice service delivered over the LTE infrastructure, is slowly

gaining traction. Many operators, especially in developed markets, have already launched the service, and many

more in other markets are expected to follow as LTE penetration increases and coverage improves. Increased

spectral efficiency and improved voice-domain efficiency are the main business benefits of migrating to

VoLTE, in addition to the savings that can be achieved by retiring legacy 2G infrastructure. However, an

uncertain business case and the high costs of deploying an IP multimedia subsystem (IMS) platform, the

backbone of VoLTE, continue to be significant inhibitors, especially for Tier 2 and Tier 3 operators.

Despite the rise of data services, voice continues to be a significant source of revenue for mobile operators.

Given the proliferation and consumer affinity for OTT voice and messaging services, the onus is firmly on the

operators – they cannot afford to go wrong with VoLTE. Exacerbating the situation is the technological

complexity introduced by VoLTE. Single radio voice call continuity (SRVCC), for example, has been

introduced to provide seamless voice service across both legacy and LTE networks. Voice over Wi-Fi (VoWi-

Fi) offers another viable solution to the larger challenge of ensuring sufficient outdoor and indoor coverage, but

will require additional call handover capabilities to VoLTE. Ultimately, operators should be aiming to

collectively improve the user experience of the voice service.

Figure 1.1: VoLTE challenges

[Source: Analysys Mason,

2015]

Figure 1.1 summarises the challenges facing VoLTE. To counter some of these challenges, operators need a

robust pre-launch test and validation strategy, and a post-launch comprehensive service assurance capability to

assure end-to-end quality of service. Operators who want to launch VoLTE should consider cost-efficient and

lightweight IMS solutions that can enable them to quickly deploy and offer the service, while providing a clear

migration path to a full IMS solution.

VoLTE

challenges

Technological

complexity

High deployment

costs

Ensuring QoS and

customer experience

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© Analysys Mason Limited 2015 VoLTE uptake will increase with LTE but the business case remains unclear

2. VoLTE uptake will increase with LTE but the business case

remains unclear

The current state of LTE 2.1

VoLTE is the new incarnation of the native mobile voice service delivered over LTE networks. The last five

years have seen significant investment in and proliferation of LTE networks with mobile operators in South

Korea, Japan and later North America deploying LTE networks to accelerate the take-up of data services and

increase revenue. The ability to create larger data allotments compared with 3G supported by ever more capable

devices will continue to accelerate the uptake of LTE technology in emerging markets over the next five years.

At the end of 2014, there was an estimated 498 million LTE connections (handsets and mobile broadband), and

this is expected to grow to 2.463 billion connections by 2019.

Figure 2.1: LTE

connections forecast

[Source: Analysys

Mason, 2015]1

VoLTE forecast 2.2

Many LTE smartphones that were early entrants did not have native support for voice services and relied on the

circuit-switched (CS) network to deliver voice and SMS services either by running two radios simultaneously or

through the circuit-switched fallback (CSFB) mechanism. The 3GPP has specified a native LTE voice service,

VoLTE, which includes SRVCC, a mechanism to interwork with existing network functions to provide service

continuity both in terms of coverage (supporting voice services when outside LTE coverage) and also in terms

of feature support (such as emergency calls, interconnection and roaming).

1 Refer to Global telecoms market: interim forecast update 2014–2019, available at

http://www.analysysmason.com/Research/Content/Regional-forecasts-/Global-telecoms-forecasts-Feb2015-RDDG0

498

861

1279

1692

2086

2463

0

500

1000

1500

2000

2500

3000

2014 2015 2016 2017 2018 2019

LT

E c

onn

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ns (

mill

ions)

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© Analysys Mason Limited 2015 VoLTE uptake will increase with LTE but the business case remains unclear

By 2018, it is expected that about 600 million smartphone users worldwide will use VoLTE as their default

voice service (Figure 2.2). Following from their leadership in LTE, the developed Asia–Pacific region and

North America will maintain their lead in VoLTE. In other regions, limited LTE coverage will give operators

little choice but to rely on 2G and 3G networks for voice services in the near term (Figure 2.3).

Figure 2.2: VoLTE connections forecast [Source:

Analysys Mason, 2015]2

Figure 2.3: Current state of VoLTE launches [Source:

Analysys Mason, 2015]

The cost of deploying IMS and technological complexity are inhibitors 2.3

VoLTE promises important business benefits, prime among them are:

Operators can achieve increased spectral efficiency because they can free up 2G and 3G carriers by

moving voice traffic to LTE networks, freeing up capacity and allowing them to reuse the valuable

spectrum for revenue-generating data services.

Operators can harness increased efficiency in the voice domain because the LTE interface is very

efficient and can support up to twice as many voice users in a given bandwidth (per megahertz) as circuit-

switched services.

Additionally, the higher voice quality promised by VoLTE adds impetus to the marketing position for operators,

especially for those aiming to position the service against the established OTTs such as Skype, Viber, etc. Given

the perceived benefits, one would expect a faster adoption of the VoLTE service. However, the roll-out of

VoLTE services is not necessarily straightforward because it requires considerable investment in an IMS core

that is designed to support multimedia sessions in an all-IP environment. Analysys Mason estimates that for a

typical Tier 1 operator, the cost of deploying and operating an on-premise IMS solution would be about

USD9 million–USD10 million3 for an initial VoLTE subscriber base of around 2.5 million, and the annual cost

can rise to about USD45 million in 5 years, for a subscriber base of around 75 million. In the long run, the

operator would break even by harnessing the spectrum benefits, but the business case tends to be complicated

and uncertain. The scale of the problem becomes even more magnified in the case of smaller Tier 2 and Tier 3

operators, as they cannot afford such high deployment costs and long implementation times with unclear

business benefits.

2 Refer to OTT communication services worldwide: forecasts 2013–2018, available at

http://www.analysysmason.com/Research/Content/Reports/OTT-communication-services-worldwide-forecasts-20132018

3 Refer to VoLTE business cases: the value of spectrum reuse, an enhanced feature set and virtualisation, available at

http://www.analysysmason.com/Research/Content/Reports/VoLTE-business-cases-Feb2015-RMA04-RDMV0

0

100

200

300

400

500

600

700

2010 2011 2012 2013 2014 2015 2016 2017 2018

Users

(m

illio

ns)

31

16

10

0

5

10

15

20

25

30

35

In deployment Launched Trialling

Nu

mb

er

of

op

era

tors

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© Analysys Mason Limited 2015 Operators must get it right first time

3. Operators must get it right first time

Despite showing a declining trend, voice is still the highest revenue-generating service for mobile operators.

Moreover, customers still expect a high-quality voice service. This, together with the established quality of

service (QoS) expectations of CS voice, places significant pressure on operators to get VoLTE right first time.

However, operators face the difficult task of implementing an expensive and extremely complex network

technology and an unclear business case.

VoLTE increases network complexity and presents new assurance challenges 3.1

Because of the inherently complex nature of the technology, operators face a variety of network and operation

support system (OSS) challenges to successfully launch, operate and assure VoLTE. Some of these key

challenges are discussed below.

Call handover in the RAN – In a scenario in which a user has initiated a call in an LTE cell but moved out

of LTE coverage mid-call, the call must be seamlessly handed over from LTE packet-switched (PS)

network to the 2G/3G CS voice network. Call drops must be avoided and the expected call quality in terms

of latency and QoS must be maintained.

Call anchoring in the core network for SRVCC – As the calls can be either PS or CS depending on the

radio coverage, all calls must be anchored by the IMS. As calls are handed over from PS to CS voice

network and vice-versa, the IMS needs to accurately maintain the state of the call and provide control for

both outgoing and incoming calls.

Expected signalling overloads – Operators have deployed diameter routing agents (DRA) for load

balancing of signalling overload from smartphones. It is expected that VoLTE will further increase the

signalling load and any DRA failure will have a significant impact on the VoLTE service.

End-to-end quality of service – Voice being real time in nature, any degradation in network performance

can have a noticeable impact on call quality. The network has to be optimally tuned to ensure voice packets

get the highest priority (assigning the appropriate QoS Class Identifier (QCI)). Some of the network

performance KPIs such as bit-rate, latency, jitter and packet loss must be monitored and actioned in real

time. Application KPIs such as call set-up delay, call set-up success rates, failed calls, dropped calls and

mean opinion score (MOS) can be used for further analysis to both reactively and proactively assure the

service.

Network performance – The network performance and optimisation and self-organising network (SON)

capability will enable operators to monitor and assure the VoLTE service in real time.

Assuring QoS in the RAN and at cell edge – Assuring QoS in the RAN is a significant challenge for

operators, which is further accentuated as customers move to the edge of the cell, as low reliability of the

connection and interference from neighbouring cells can result in dropped calls.

Operators face a significant risk of launching an ill-conceived service and failing to meet customer expectations

if they do not carefully plan for all failure scenarios.

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© Analysys Mason Limited 2015 Operators must get it right first time

Vigorous pre-launch service validation testing can mitigate the risks 3.2

Operators can partly minimise the risks by following a thorough service validation test regime before the launch.

In doing so, they must consider a plethora of factors and scenarios. Consider, for example, the different call

scenarios that are possible, such as VoLTE to VoLTE, VoLTE to 2G/3G/CDMA and vice-versa, VoLTE to

PSTN and vice-versa, E911 and lawful intercept, among others. Furthermore, many legacy network components

must be tested because of the software upgrades related to SRVCC.

The regime needs to cover a wide range of both test methods and scenarios, including handover between

different networks and domains. For example, such a test regime should include the simulation of individual

user sessions from both real and test devices. Test devices can be simulated in sophisticated equipment that can

generate both signalling and media plane traffic, to ensure consistent end-to-end performance. Flows can be

examined at various points across the network to verify compliance with relevant standards and interworking.

Individual test cases and scenarios should also be complemented by high volume stress testing, which can

include mass call or session generation. As VoLTE promises higher quality service, it is also essential to

validate session quality, for both voice and video. This can be achieved through the use of algorithms such as

PESQ/POLQA and PEVQ. If operators intend to position VoLTE as a best-in-class solution, then they must be

able to guarantee that it performs as expected.

IP probes will be crucial for assuring VoLTE post-launch 3.3

As operators look to launch VoLTE, they must deploy and scale IP probes that are capable of monitoring the

key interfaces, IP voice traffic and the related protocols to support voice transmission over a PS network. In

VoLTE, the control plane is used for authentication, mobile attach and bearer creation, while the SIP signalling

and the IP voice traffic is carried over the user plane. Probe solutions that are capable of correlating control-

plane and user-plane data for effective troubleshooting will be needed.

A network call set-up for VoLTE requires significant levels of co-ordination among disparate network elements.

Signalling for attach registration and call control must be monitored for troubleshooting. A call handover

scenario (SRVCC) is even more complex as it involves more signalling complexity between the IMS, core

network and RAN. IP probe solutions cover most of this functionality and are going to be an important part of

operators’ service assurance strategy.

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© Analysys Mason Limited 2015 Operators should focus on a holistic customer experience

4. Operators should focus on a holistic customer experience

The ability to offer a high-quality voice service and superior customer experience is vital for operators to be able

to compete with the OTT VoIP service providers. As operators prepare to launch VoLTE or scale up the service,

they will need a two-pronged strategy to ensure that customer experience is not compromised.

Deploy advanced analytics and service management applications to measure end-4.1

to-end QoS

By design, VoLTE with SRVCC utilises both the PS and CS network infrastructure to deliver the voice service.

Calls handed over to the CS voice network will need to be monitored and assured for the QoS that has been

traditionally delivered. From an end-to-end perspective, where a call was initiated in LTE and handed over to

the CS network, the solution needs to be in a position to perform root cause analysis and cross-domain

correlation across LTE, 2G/3G and IMS components.

From a customer experience management perspective, a VoLTE service management application providing per-

customer KPI reporting as well as additional guidance on likely reasons for service degradation enables both

operations and customer care personnel to better troubleshoot issues and manage customer relationships

effectively. Such reporting applications enable other internal organisations such as network engineering to better

plan and optimise network resources for optimum customer experience. Marketing teams would also potentially

benefit from this insight.

Compensate for poor coverage with small cells and VoWi-Fi 4.2

Mobile data consumption will continue to grow rapidly as the LTE networks expand, and the take-up of

smartphones and other mobile broadband devices increase, causing coverage and capacity problems for mobile

operators. As VoLTE becomes more mainstream, operators will be particularly hard pressed to address this

issue because an inability to make voice calls due to poor coverage issues will result in poor customer

experience and cause churn. Operators must plan to minimise the network blind-spots and provide sufficient

coverage at the most likely places where customers are expected to use the VoLTE service – for example, at

indoor and outdoor locations such as city centres, central business districts or sports arenas.

Operators can achieve this by supplementing their macro network by deploying small cells in dense locations.

However, deploying small cells is a complex and expensive exercise as operators may encounter many

challenges such as identifying appropriate locations for installations; providing the necessary backhaul, network

and traffic planning; and minimising opex associated with large numbers of small cells. Mobile operators can

also address the coverage issue for voice by implementing the VoWi-Fi service and support seamless call

handovers between the LTE network and Wi-Fi, and vice-versa. By allowing customers to use the Wi-Fi access

network for voice calls, operators can also reduce pressures on the LTE bandwidth and capacity. Admittedly,

VoWi-Fi solutions only address the coverage issue from the voice service perspective, and operators will still

need to deploy small cells to tackle the broader issue of coverage for data services.

The launch of the new iPhone 6 with iOS 8, which supports VoWi-Fi (and VoLTE), strengthens the confidence

of operators in rolling out the service and increases the chances of accelerating the service take-up.

Both Three UK and T-Mobile USA have live VoWi-Fi services, and more American operators such as AT&T

and Verizon have announced plans to launch the service to complement their VoLTE plans.

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© Analysys Mason Limited 2015 Vendor solution overview – Polystar Group

5. Vendor solution overview – Polystar Group

It is clear that the launch of VoLTE is not without challenges. To successfully launch VoLTE/VoWi-Fi, it is

essential for operators to build partnerships with vendors that can offer the necessary tools, capabilities and

resources to ensure that the investment objectives are met, and the service is delivered with the required level of

performance. Among many vendor options available in the marketplace, one vendor is the Polystar Group.

Polystar Group offers a complete range of solutions to support the entire lifecycle of VoLTE, including service

deployment, validation and testing, service assurance, growth and monetisation. Polystar’s solutions have been

specifically designed to minimise the risk of service launch, enable rich services to be delivered and ensure that

customer experience is optimised.

Polystar’s solutions enable:

Operators to rapidly launch VoLTE/VoWi-Fi services

Validation and verification of VoLTE/VoWi-Fi

Real-time service assurance for VoLTE/VoWi-Fi

Actionable intelligence to enhance customer service.

Figure 5.1:Polystar solution

[Source: Polystar, 2015]

Network and Customer Insight solutions 5.1

The Network and Customer Insight solutions enable operators to monitor the overall performance of the VoLTE

network. Operations personnel and engineers can obtain an end-to-end view of the network through a wide

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© Analysys Mason Limited 2015 Vendor solution overview – Polystar Group

range of KPIs and parameters, presented in the form of clear visual dashboards and displays. The dashboards

offer high levels of flexibility allowing users to modify existing reports and to create dashboards of their own.

The solution consists of both probes and call-trace applications. It supports all relevant signalling and

protocols/interfaces for VoLTE/VoWi-Fi, including IMS. The solution provides detailed, real-time insight from

the network, enabling operators to detect and act on potential network issues with a minimum of delay.

Additionally, all monitoring is performed with the same components, allowing for easy correlation of signalling

across different interfaces.

Operators can use the Network and Customer Insight solutions in tandem to quickly troubleshoot emerging

network problems that could impact VoLTE/VoWi-Fi services. Upon discovering KPI threshold breaches on the

dashboards, operations personnel can drill deeper to view granular network level information captured by the

probe. The ability to gain an end-to-end network view as well as deeper network insight enables operators to

effectively monitor and troubleshoot VoLTE and VoWi-Fi services.

Solver 5.2

Implementing VoLTE with SRVCC is a complex process because existing networks and nodes require upgrades

and configurations to support new functions. New nodes and functions also need to interact seamlessly with

existing ones and a multi-vendor network environment adds further complexity to the challenge. By planning

and executing a thorough test strategy, operators can minimise the risks of failure.

Figure 5.2: Validation

test methodology

[Source: Analysys Mason

and Polystar, 2015]

Performing tests with real terminals (user equipment) can be a time-consuming task. By using simulated

terminals and a simulated RAN, the functions in the core network can be validated much faster. In the first

phase of the implementation, it is sufficient to simulate a few users as the volumes are enough to test basic

functionality. The second phase of the testing could include several hundreds of users, to validate all the

network functions to ensure end-to-end functional compliance. This phase will form the crux of the validation

strategy as it will include testing of the numerous legacy network functions that have been upgraded to support

SRVCC. The final phase will focus on a full system load test to make sure that all network nodes and functions

deliver the planned capacity. Quality measurements for voice and video should be carried out during all the

phases to determine that QoS does not degrade with increased traffic volume.

Solver supports key IMS interfaces as defined by 3GPP, such as Mb, Ix and Iq; with support for RTP/SRTP and

H.248 protocols, as well as voice and video quality algorithms. With Solver, operators can execute all required

tests for a successful VoLTE and SRVCC implementation from a single platform. Using the intuitive user

interface, test cases can be built and executed within minutes and without the need for extensive training.

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© Analysys Mason Limited 2015 Vendor solution overview – Polystar Group

ODIN 5.3

ODIN is an out-of-the-box software platform that provides a cost-efficient alternative to the expensive IMS,

enabling operators to quickly launch VoLTE and VoWi-Fi services. It is also future-proof because, if and when

the operator decides to deploy a complete IMS platform, ODIN can assume the role of an application server in

the IMS network. It is fully virtualised, running on commodity hardware, offering flexible deployment options,

either on-premise or delivered from the cloud. Because ODIN comes as a single node, it requires minimal

integration, costing much less to integrate into the network environment than traditional IMS solutions. In

addition, the integration of ODIN requires significantly less time.

Odin is compliant with a range of 3GPP standard interfaces, including MAP, CAPv2, Cx, Dx, Sh, Gy, SIP (IMS

profile) and ISC. It can be integrated into the core network as a standard SS7 node, combined S-CSCF and AS

or as a standalone IMS AS. This flexibility provides a smooth deployment capability with a clear evolution path

should the core be upgraded to support a full IMS. Currently, ODIN supports VoLTE (IR.92), VoWi-Fi,

MMTEL, SRVCC and Service Centralisation and Continuity. Figure 5.3 and 5.4 depict the pre-IMS and post-

IMS deployment scenarios of ODIN.

Figure 5.3: ODIN pre-IMS

[Source: Polystar, 2015]

Figure 5.4: ODIN post-IMS

[Source: Polystar, 2015]

Post-IMS

Pre-IMS

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© Analysys Mason Limited 2015 About the author

About the author

Anil Rao (Senior Analyst) is a member of Analysys Mason’s Telecoms Software research

team and is the lead analyst for the Service Assurance programme, focusing on producing

market share, forecast and research collateral for the programme. He has published research on

IP probes, real-time network analytics and the importance of service assurance in reducing

churn and improving customer experience. He holds a BEng in Computer Science from the

University of Mysore and an MBA from Lancaster University Management School, UK.

4

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© Analysys Mason Limited 2015 About Polystar Group

About Analysys Mason

Research

We analyse, track and forecast the different services accessed by consumers and enterprises, as

well as the software, infrastructure and technology delivering those services.

Research clients benefit from regular and timely intelligence in addition to direct access to our

team of expert analysts.

For more information, please visit www.analysysmason.com/research.

About Polystar Group

Polystar Group enables communications service providers to achieve excellence in CEM, big data

analytics, service assurance, network monitoring and high performance testing. Polystar helps CSPs to

simplify their CEM strategies and drive operational efficiency through real-time network analytics.

Polystar’s real-time Network and Customer Insights uncover a goldmine of data, which yields

indispensable insights to CSPs. Polystar is recognised as one of the fastest-growing companies in

Sweden. Since its inception in Stockholm in 1983, Polystar has experienced continuous and

sustainable growth, and evolved to a global presence, serving customers in over 50 countries.

For more information, please visit www.polystar.com.