DOES YOUR PCRF HAVE WHAT IT TAKES TO SUPPORT VOLTE?

DOES YOUR PCRF HAVE WHAT IT TAKES TO SUPPORT VOLTE? | 2

Table of Contents

EXECUTIVE SUMMARY ...........................................................................3

INTRODUCTION ......................................................................................3

WHAT’S SPECIAL ABOUT VOLTE TRAFFIC? ..........................................4

POLICY CONTROL INTEGRATION AS A REQUIREMENT TO SUPPORT VOLTE ............................................4

MEETING THE STRINGENT REQUIREMENTS FOR HIGH-QUALITY VOICE SERVICES ..................................................5

A NEW APPROACH TO VOICE SERVICES ..............................................5

SAFETY AND REGULATORY COMPLIANCE ...........................................6

POLICY DEPLOYMENT MODELS FOR VOLTE ........................................7

CONCLUSIONS ......................................................................................8

AMDOCS POLICY SOLUTIONS — A KEY ENABLER IN VOLTE DEPLOYMENTS ...........................................9

ABOUT AMDOCS ..................................................................................10

DOES YOUR PCRF HAVE WHAT IT TAKES TO SUPPORT VOLTE? | 3

Executive summary

Voice over LTE (VoLTE) brings voice to Long Term Evolution (LTE) networks, enabling service providers to manage voice and data traffic more efficiently, and to provide a wide range of new services. Launching VoLTE requires mobile operators to not only deploy the IP multimedia subsystem (IMS), but also to integrate it with the policy and charging rules function (PCRF) to offer high-quality, reliable voice services. A scalable and hardened policy controller that supports the latest standards and advanced VoLTE functionality is crucial to ensuring a smooth transition to VoLTE and a successful expansion of carrier based multi-media services.

With the integration of policy control and VoLTE, mobile operators can use their network resources more efficiently and create a new service framework for their voice services, which will lead to improved quality of experience (QoE) and subscriber retention. In addition, extending policy functionality to VoLTE enables service providers to meet safety and security requirements (e.g., emergency calls and lawful intercept), and to expand roaming service options and revenues.

Introduction

For decades, voice was the crucial growth driver for mobile services, as well as the mainstay of the wireless industry. The rise to prominence of data services introduces changes within the growth dynamics. With the widespread adoption of smartphones, the revenue contribution from non-voice data services has grown, along with those services’ perceived value to subscribers and the percentage of overall traffic they capture.

Yet even with the popularity of data services, voice retains a special prominence as a mobile service. Customer acquisition and retention will continue to depend on the quality of voice services, while at the same time the infrastructure supporting voice services is undergoing an overhaul in LTE. In LTE networks, VoLTE gives mobile operators the tools to move to higher-quality voice, richer services, and integrated voice-and-data service offerings – the first step toward a truly unified communications experience.

Subscribers are ready for change. In the last few years, they have started to migrate to over-the-top (OTT) apps that offer compelling and innovative voice, even though these services typically provide inferior quality. The move to VoIP

and messaging OTT services is only partially driven by the lower costs of OTT services, and more by the improved functionality, easier-to-use interface and social networking links. With VoLTE and rich communication services (RCS), mobile operators can reinforce their role as the main provider of voice and messaging services, both by introducing the same features that make OTT applications attractive to subscribers, and by providing a superior performance for these applications. Service providers have exclusive control over unique assets – their networks, a trusted relationship with subscribers, and knowledge about subscriber preferences and location – to deliver superior services using quality as a key differentiator.

To meet service providers’ requirements, VoLTE PCRF solutions have to provide a voice service over LTE that is at a minimum comparable, if not superior, to traditional circuit-switched voice. Specifically, VoLTE and the supporting IMS core have to be fully integrated with policy control and enforcement to prioritize traffic effectively in support of voice services. The PCRF has to have the scalability, flexibility and functionality required to support the unique requirements stemming from VoLTE traffic, such as high performance to meet the increased signaling, and the growing complexity of managing multi-service traffic flows.

We are at a crucial stage in VoLTE adoption today. According to the Global Mobile Supplier Association (GSA), more than 270 operators have deployed LTE with most others committed to introducing VoLTE. This is a complex transition where much is at stake, and mobile operators have to be careful not to degrade existing data services and legacy voice services while launching VoLTE.

VoLTE treats voice as a data service – although a special one, subject to more stringent performance requirements than other data services – leaving service providers to determine how to manage voice traffic in relation to other types of data traffic, such as web browsing, video content and social media.

This paper discusses the specific policy management requirements stemming from VoLTE, including quality of service (QoS) support, scalability and from mandated safety and security functionality, which dictate what it takes for a PCRF to fully support VoLTE.

DOES YOUR PCRF HAVE WHAT IT TAKES TO SUPPORT VOLTE? | 4

What’s special about VoLTE traffic?

LTE mobile networks no longer manage voice traffic separately from data traffic. LTE replaces the circuit-switched voice network with a packet-switched network that supports both voice and data, and optimizes the traffic mix. However to support the required high-quality voice

services, mobile operators need to have control tools to treat voice traffic differently from data traffic.

To provide high-definition (HD) voice quality, LTE operators need to assign the highest QoS (i.e., a QoS class identifier [QCI] of 1) to VoLTE traffic. To do so, multiple network elements are required (Figure 1):

FIGURE 1: MANAGING VOLTE TRAFFIC WITHIN AN LTE NETWORK

IMS (SIP)

eNodeBUE

MME / SGW

PGW (PCEF)

P-CSCF S-CSCF

HSS

LTE / EPC (DIAMETER)

SIP-DEDICATED BEARER (CONTROL PLANE)

VOICE-DEDICATED BEARER (USER PLANE)

PCRF

Rx

Cx

SGIS5S1-U, S1-MME

S6

Gx

Policy control integration as a requirement to support VoLTE

To manage voice traffic with VoLTE in an LTE network, mobile operators need to integrate the IMS within the LTE evolved packet core (EPC) because this allows them to apply QoS functionality to voice services.

The tight coordination between the proxy call session control function (P-CSCF) in the IMS, and the PCRF in the LTE/EPC network brings new challenges, because VoLTE generates high signaling volumes – up to 10 to 12 times the transactions per second (TPS) than non-voice data traffic generates. To avoid unsustainable signaling levels or signaling floods, which disrupt not only voice but also the entire network’s performance, mobile operators require a highly scalable PCRF with proven support of the Rx interface.

Once mobile operators have control over the increased complexity and signaling traffic volume that result from the integration of the IMS within the LTE/EPC, they can offer advanced voice services that are not available in a switched-voice environment.

Mobile operators can set policies, such as use multiple codecs within the network for different subscribers, or to negotiate QoS by traffic type and subscriber/device, in the PCRF to be applied to voice traffic through the Rx interface within the IMS. This policy-based approach to managing voice traffic enables mobile operators to optimize QoE, allocate network resources at peak times when capacity is limited, and tailor services based on subscribers’ individual plans, tier and device types.

DOES YOUR PCRF HAVE WHAT IT TAKES TO SUPPORT VOLTE? | 5

Meeting the stringent requirements for high-quality voice services

While subscribers attach increasing value to data services, their expectations about service voice availability and reliability remain stricter than those for data. To ensure high availability and quality of voice services, the PCRF has to support geo-redundancy for reliability, as well as Gx and Rx session continuity in case of local and geo-redundant fail overs. With geo-redundancy, a PCRF can preserve voice service reliability by handling requests originally directed to a nonresponsive PCRF to avoid VoLTE service outages.

To capitalize on the benefits of VoLTE, service providers cannot be constrained by legacy PCRF solutions that are incapable of handling the rigors of VoLTE’s added functionality, scalability and performance. They need a future-proof solution with full support for the Gx and Rx interfaces as defined in the latest Third Generation Partnership Project (3GPP) specifications, as well as GSM Association (GSMA) guidelines for manage dedicated bearers.

To accommodate current and future IP address allocations for VoLTE, and driven by the need to support an increasing number of devices, mobile operators have to choose a PCRF that supports IPv4, IPv6 and IPv4v6.

Standards support facilitates the easy integration of VoLTE into LTE networks and the adoption of new functionality. In turn, this leads to lower costs by reducing the complexity of customization and interoperability testing in multivendor environments.

A new approach to voice services

With VoLTE, the PCRF takes on a central role in defining and managing voice services, within the wider framework of IP-based mobile data services.

The first advantage gained is consistency across services. Data is no longer an add-on to the base plan. In some countries, most subscribers already have plans that include integrated voice and data allocations. With VoLTE, the distinction between a voice cap and a data cap may cease to exist, and service providers can treat voice traffic as data traffic if they so choose.

When offering bundled offers, location-based services, tiered plans, dynamic offerings based on real-time network load, or roaming offers, the service provider has the ability to use consistent (or the same) policy definitions for both voice and data. This may make the service offering more compelling and easier to communicate to subscribers, who are often overwhelmed by the complexity of mobile plans.

At the same time, because the value of voice and data services is not currently perceived as the same to subscribers, service providers need to retain the ability to meter and charge separately for voice and data – as well as for different VoLTE services, including basic voice, SMS, video calls, multimedia services, and other RCS (Table 1, Figure 2). For instance, a service provider may want to define a plan with separate caps – one for data, another for voice, and a third for video calls – and combine them with unlimited SMSs.

TABLE 1: VOLTE-ENABLED SERVICE OFFERINGS THAT REQUIRE POLICY INTEGRATION

VoLTE-enabled service offerings that require policy integration

Bundled offers Premium voice and data services, in combined plans

Time and volume offers Flexible voice charging that can be based on both time (minutes) and volume (bytes)

Location-based offers Differentiating voice charging based on congestion hotspots versus geography

Tiered services QoE based on different packages and plans

Dynamic offersReal-time value offerings promoted on a dynamic basis, based on real-time network performance and contextual information

Roaming offers Tailored offers based on partnerships with other service providers

DOES YOUR PCRF HAVE WHAT IT TAKES TO SUPPORT VOLTE? | 6

The wider opportunities to use policy to define new services with VoLTE extends to roaming as well. The Rx interface between the CSCF and the PCRF enables QoS support while roaming, extending tiering and other capabilities to the visited network for a consistent subscriber experience. Through the S9 interface between the home and visited PCRFs, mobile operators will be able to develop customized agreements with their roaming partners that require QoS functionality and that enable more sophisticated charging models, including local breakout (LBO) – either when they and their operator partners are ready, or when regulation mandates them. For instance, tiering functionality may expand to roaming, and roaming deals may be offered on the basis of the real-time network conditions of the visited network.

Safety and regulatory compliance

Service providers deploying VoLTE also need to be in compliance with safety and other regulatory requirements, such as emergency calls and lawful intercept. Service providers have to assign the highest QoS to emergency calls,

to ensure reliability and to provide precise location information. Emergency services and location information are not value-added services, but vital requirements for all voice networks. In most countries, they are legally regulated. To deploy VoLTE commercially, mobile operators have to be able to support emergency services that are always available and have the highest available reliability.

Even where regulation does not mandate strict requirements and allows service providers to fall back to legacy networks for emergency services, native support of these services within VoLTE is essential to a future-proof solution. As LTE coverage increases through network expansion or replaces legacy networks through spectrum refarming, emergency services become mandatory in locations where service providers have LTE-only coverage.

The mandated support of emergency calls, lawful intercept and other services requires full integration between the VoLTE/IMS and the LTE/EPC, and adherence to 3GPP standards to collect location information.

FIGURE 2: VOLTE AS A STEP TOWARD ENRICHED COMMUNICATIONS

EVOLVED

COMMUNICATIONSOLUTIONS

VIDEO

• Video Call• HD Video

GROUP COMMS

• Group Video Calls• Voice

Conference Call• Group Messaging• Family-Centric Comms

REACHABILITY AND ADD-ON SERVICES

• Simultaneous File Transfer• Share Location with Contact• One Number for all Devices• Social Network Integration

VOICE

• VoIP• HD Voice

MESSAGING

• SMS/MMS• Instant Messaging• One Inbox for all Messages

ADDRESS BOOK AND CONTACT MANAGEMENT

• Integrated Address Book• Shared Contacts• Status and Presence

•

s

Ad-Hoc

DOES YOUR PCRF HAVE WHAT IT TAKES TO SUPPORT VOLTE? | 7

To support emergency calls, the mobile device has to maintain a connection to an access point name (APN) for VoLTE to ensure that a call can be initiated at any time and directed to the nearest public safety answering point (PSAP). Operators have to enable PSAPs to call back subscribers if the call is interrupted, and to support emergency voice continuity so that VoLTE emergency calls can be handed off to legacy networks if the caller moves to an area without LTE coverage. This functionality has to be provided both within the home network and during roaming (i.e., allow emergency calls to be placed even when roaming is blocked).

In the emergency service context, the PCRF has to instantiate the appropriate policy to ensure that emergency calls receive the highest priority. It also has to provide the 3GPP-defined subscriber location information to the P-CSCF so that the call is correctly routed.

The control over traffic flows within the PCRF enables mobile operators to identify and filter targeted voice traffic and therefore to support lawful intercept and similar services.

To support lawful intercept, the P-CSCF sends a request over Rx to the PCRF, which in turn is routed to the PCEF for enforcement. Having a PCRF solution that supports regulatory requirements for lawful intercept enables the same level of support for VoLTE services as seen by traditional circuit switched networks.

Policy deployment models for VoLTE

The optimal approach for policy control and VoLTE is still being debated in the industry, but there is a growing shift towards a dual-PCRF model. In a model such as this, a legacy PCRF provides policy control functions for all LTE data traffic, such as bandwidth management, QoS control, and fair usage policy. A second, PCRF is deployed alongside the legacy PCRF, specifically designed to handle VoLTE (IP voice) traffic. Most service providers deploying VoLTE services plan to use a dedicated APN for VoLTE traffic, having a dual-PCRF model can utilize this dedicated APN to separate the voice and data traffic.

FIGURE 3: A DUAL-PCRF MODEL

Gx

Rx/SOAP

SPR

Sd

Sp

APPLICATION SERVERS(IMS, NON-IMS)

INTERNET

VoLTE PCRF

MOBILE DEVICES

eUTRAN (eNodeB)

S-GW P-GW

TDF/DPI

LEGACY PCRF

ONLINE CHARGING SYSTEM

VoLTE APNGx

Sy

DOES YOUR PCRF HAVE WHAT IT TAKES TO SUPPORT VOLTE? | 8

Industry research indicates that service providers are acknowledging that legacy PCRFs will need to be upgraded or replaced to meet the rigorous demands of VoLTE According to a recent Heavy Reading operator survey, 60 percent of service providers stated that they needed to upgrade their existing PCRF solution to handle VoLTE, another 10 percent stated that they had to replace their policy solution altogether (Source, Heavy Reading, 2013).

The consensus is that service providers can de-risk their VoLTE service launch by continuing to enforce data plan policies using their existing PCRF and introducing VoLTE with a VoLTE-specific PCRF. This dual-PCRF model also helps to provide a time-to-market advantage for VoLTE services.

As service providers consider their VoLTE launch plans, it makes sense to consider a dual-PCRF model. Benefits of this model include, a simplified, reduced risk launch with rapid time to market. As VoLTE services grow, service providers can ultimately evolve towards a unified policy control platform for both their data and VoLTE services.

Regardless of whether service providers choose a dual-PCRF model or not, it’s imperative the policy solution deployed to handle VoLTE traffic has what it takes to tackle the challenges of managing voice traffic within a data network and preserve the voice quality that subscribers expect.

Conclusions

VoLTE gives mobile operators the opportunity to chart a new strategy for voice – offering richer and more attractive services, and fully integrating voice traffic management with overall data traffic. A successful VoLTE implementation improves customer retention, as it extends 2G and 3G voice, and SMS services by providing better voice quality and reliable QoS. It also expands the scope for mobile operators and OTT providers to work together to define new services and establish new charging and revenue-sharing models. A carefully planned and executed integration of IMS and PCRF is required in order for a service provider to seamlessly insert VoLTE into LTE networks and leverage the functionality of VoLTE, and more generally IMS.

DOES YOUR PCRF HAVE WHAT IT TAKES TO SUPPORT VOLTE? | 9

Amdocs Policy Solutions — a key enabler in VoLTE deployments

The Amdocs Policy Solutions, including the Amdocs Policy Controller and the Amdocs VoLTE Controller, are powerful complements to the IMS core that gives mobile operators the functionality, reliability and scalability in their LTE networks to support VoLTE. Whether for initial deployments in which VoLTE coexists within circuit-switched legacy networks, or for mature deployments where VoLTE becomes the dominant voice interface, Amdocs Policy Solutions support the VoLTE functionality needed to successfully launch a new generation of voice services.

To provide the high-quality, rich, personalized voice services that VoLTE and HD voice enable, service providers cannot rely on legacy PCRF solutions. These legacy solutions limit service providers’ flexibility in defining and managing services, as well as their ability to leverage technology and standards to differentiate their offerings from those of their competitors.

The Amdocs Policy Controller and Amdocs VoLTE Controller provides the industry’s most comprehensive support for advanced functionality, evolving standards and interoperability, to ensure service providers will be at the leading edge in offering VoLTE services to their subscribers. The Amdocs VoLTE Controller also provides a time-to-market advantage, allowing service providers to launch VoLTE services in a matter of months, differentiating their services in an already competitive market. The Amdocs VoLTE Controller can be deployed alongside existing PCRF solutions in a coexistence strategy, ensuring all VoLTE traffic is handled by the purpose-built, VoLTE-specific PCRF. This approach to VoLTE policy support de-risks existing LTE data services and allows for simplified and cost-effective entry into the VoLTE market.

Feature Why is it needed?

ScalabilityAccommodate the increased Diameter signaling generated to manage VoLTE traffic within the LTE/EPC network

QoS, dedicated bearer support

Assign highest priority to voice traffic to ensure high quality and reliability in voice services

Policy definition for Rx call flows

Customize treatment of voice traffic (e.g., to allow codec selection)

Geo-redundancyMinimize network disruption to voice services caused by temporary unavailability of core network elements

Support for latest 3GPP standards

Support the most advanced functionality for new service creation and for interoperability

IPv4, IPv6, IPv4v6 dual-stack support

Deploy a future-proof solution for IP address allocation and to support multiple IP addresses in VoLTE devices

Emergency call support Comply with regulatory requirements, especially if planning spectrum refarming

3GPP location Provide location information to the P-CSCF for emergency call services

Consistent policy definitions

Enable combined or differentiated voice and data charging, and support bundling, tiering, dynamic services, location-based services, and roaming offers

Roaming supportIntroduce QoS functionality in roaming to widen the scope of services and revenue opportunity, and to support LBO

Voice traffic filtering Meet mandates for lawful intercept

ScalabilityAccommodate the increased Diameter signaling generated to manage VoLTE traffic within the LTE/EPC network

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