SIP/VOIP transformation towards IMS (Total IP)


The telecommunications industry has been going through a significant transformation over the past few years. At the outset incumbent operators used to focus on mainly basic voice services and still remained profitable due to the limited number of players in the space and requirement of huge amounts as initial investment.

However, with the advent of competitive vendors, rise in consumer base, and introduction of cost effective IP based technologies a major revolution has come about. This has enabled operators to come out of their traditional business models to maintain and enhance subscriber base by providing better and cheaper voice, multimedia and data services in order to grab the biggest possible share in this multi- billion dollar industry.

The evolution in Telecom industry has been accelerating all the time. The Next-Generation Operators wants to keep pace with the rapidly changing technology by, adapting to market needs and looking at the system and business process from multiple perspectives concurrently. Communication Service Providers (CSPs) need to consider several factors in mind before proposing any solution. They need to deploy solutions which are highly automated, highly flexible, caters to customer needs coupled with ultra low operating costs.

Upgrading a softswitrch solutions to IMS

The Softswitch is decomposed into two logical components of a subscriber-facing unit and a PSTN-facing unit. 

  • Subscriber facing unit in Softswitch is upgraded to AGCF (Access Gateway Control Function) 
  • PSTN facing unit is upgraded to MGCF (Media Gateway Controller Function) to interwork with IMS as shown.

By separating the Softswitch into these components, the network can be more easily scaled for better overall network efficiencies. More AGCFs can be added as required, allowing the network to scale with an increase in subscribers. Similarly, More PSTN trunks can be added as traffic increases. Once PSTN and subscriber control functions are separated, the IMS elements, CSCF and BGCF functions can be introduced. BGCF is the interface for interconnecting IMS with legacy PSTN networks.

New SIP-based services can now be rapidly rolled out by deploying new Application Servers (AS) and its integrations to other SBC for UCC( unified communication and colloboartion ) systems. IMS has 3GPP specified ISC interface, which is a SIP-based interface for interfacing-to-application servers. Using these constructs, multiple application servers from multiple vendors can be interconnected over the IMS ISC interface.

Intelligent Networks( IN)

Telecom networks (2014) are made up of integrated service digital network (ISDN), the public switched telephone network (PSTN) ,the Public Land Mobility Network (PLMN) and many others. Intelligent networks (IN) ensures that call control is handed over to a control platform. The control platform determines how the establishment of this call shall continue. Applying IN to any of these networks has in common that call establishment is intercepted at a designated node in the network

By hosting new services on the new platform and combining new and old services CSP‟s aim to provide service bundles that would generate new revenue streams. This process is largely dependant on IMS ( IP Multimedia Subsystem ) architecture .

Transformation towards IMS (Total IP)
Transformation towards IMS (Total IP)

Optimization in operator landscape evolve as result of synergistic technologies that come together to address the innovation and cost optimization needs of operator for better user experience. In following sections different technological evolutions that are affecting overall operator ecosystems have been discussed with focus towards Service Layer.

Fixed/mobile convergence(FMC) with IMS

“Fixed Mobile Convergence is a transition point in the telecommunications industry that will finally remove the distinctions between fixed and mobile networks, providing a superior experience to customers by creating seamless services using a combination of fixed broadband and local access wireless technologies to meet their needs in homes, offices, other buildings and on the go.”

 Fixed-Mobile Convergence Alliance (FMCA)  2004

System can communicate over the cellular network, or act as a new endpoint on the IP network. Home Subscriber Server (HSS) manages subscriber data uniformly between the cellular and IP worlds. The Handoff Server runs on top of the ISC interface, and provides a seamless experience when subscribers move from the cellular network to a Wi-Fi network. The AGCF remains the functional centre of the network, but with the introduction of the HSS, has added the Cx and Sh interfaces defined by the IMS.

Legacy to IP transformation

This section broadly covered the aspects of migration from legacy IN solution to new age JAINSLEE framework based one. Applies to Legacy IN hosting voice based services mostly  such as VPN, Access Screening ,Number Portability, SIP-Trunking,Call Gapping.

Most operator environments have seen a rise in the number of service delivery platforms. Also complexity of telecom networks have increased manifold hence CSPs are facing multiple challenges. Increased efforts and costs are required for maintaining all the SDP platforms. These platforms are generally of different vendors and cater to different technologies thereby greatly increase chances of limiting the scalability and flexibility of the operator landscape. More effort required for sustaining the life cycle of the platform and challenges in integrating non compatible SDPs due to proprietary design have been stumbling blocks in the progress of CSPs across the world.

To overcome these challenges there is trend in the market to move towards SDP consolidation wherein instead of maintaining several SDPs with their proprietary design CSPs prefer maintaining a single or less number of SDPs having standardized interfaces.

SDP consolidation
SDP consolidation (1)
SDP consolidation (2)

As illustrated in the above figure there is a transition that is taking place in the industry towards consolidation of service delivery session control. This would provide a cost effective sustenance of existing applications and the rapid creation and deployment of new services leading to increased revenue recognition by CSPs.

  • Agile Development
  • Innovative services
  • open SOA based architectures
  • IN/NGN Platform and Services
  • Reuse of existing investments in legacy service platforms
  • low cost of new service development
  • faster time to market
  • Monetize investment in Network Infrastructure uplift – SIP trunking, VoLTE etc.

Services that should be covered  in the Scope of Migration from fixed line to IP telephony are:

  • Virtual Private Network (VPN) : An Intelligent Network (IN) service, which offers the functions of a private telephone network. The basic idea behind this service is that business customers are offered the benefits of a (physical) private network, but spared from owning and maintaining it.
  • Access Screening(ASC): An IN service, which gives the operators the possibility to screen (allow/barring) the incoming traffic and decide the call routing, especially when the subscribers choose an alternate route/carrier/access network (also called Equal Access) for long distance calls on a call by call basis or pre-selected.
  • Number Portability(NP) : An IN service allows subscribers to retain their subscriber number while changing their service provider, location, equipment or type of subscribed telephony service. Both geographic numbers and non-geographic numbers are supported by the NP service.

 

WebRTC based Unified Communication platform

Using WebRTC Solution for Delivering In Context Voice which provides new monetizing benefits to the Enterprise customers of Service Providers. This includes following components:

  • WebRTC Gateway for implementation for inter-connect with SIP Legacy
  • Enhancement of WebRTC Client with new features like Cloud Address Book, Conferencing & Social Networking hooks.
  • Cloud based solutions
INtoJAISNLEE

Challenges in Migration to IMS  (Total IP )

Since long I have been advocating the benefits of migration to IMS  from a current fixed line / legacy/ proprietary VOIP / SS7 based system . However I decided to write this post on the challenges in migration to IMS system from a telecom provider’s view.  Though I could think of many , I have jot down the major 4 . they are as follows :

Data Migration challenges

  • Establishing a common data model definition
  • Data migration seamlessly
  • Configuration management
  • Extracting data from multiple sources and vendors , that includes legacy systems
  • Extracting data due to its large scale and volume

Training

  • Creating an effective knowledge share and transfer for live operations
  • Training in fallback plans, standards and policies .

Customer impact

  • Minimized customer outage
  • Enhance customer experience by delivering quality services on schedule
  • Ensuring security of customer’s confidential data
  • Transfer of customer services without any impact.

Testing in replicated environment

  • Physical pre-transfer test
  • Reducing cycle time
  • Verification and validation at every change in data environment
  • Detect production issues early in the test -lifecycle

Fallback plans

  • Pilot program and real network simulation for ensuring preparedness
  • Tracking changes in new network

 


Evolution of voice Communication


From ARPANET(Advanced Reseracha nd Prjects Agency Network) in 1973 by US dept of defence , invention of HTTP in 19196 and finally evoluation of SIP in 2000 and availiability of broadband ethernet services, the telecom landscape has evolved. As far as infrastructure, services, and contents are concerned, the VoIP industry is witnessing a migration from POTS / PSTN/  Legacy integrations to  NGN (Next Generation  Network).

NGN was implemented globally as a means to change the cost base, agility and service capabilities of telecoms providers. The evolved architecture for the transition is one that provides flexibility to service providers by enabling them to deploy new services on IP based technologies, while leveraging existing services and infrastructure as long as it makes sense. This post describes the evolution of voice communication in access , transport and  session layers respectively.

1G2G3G4G5G
Year of dev1970-19841980-19991990-20022002-20102010-2015
Launch year1987 by Telstra Australia 1991 in Finland by Elisa1998 pre-commercial launched by NTT DoCoMo in Japan , branded as FOMA.2009 in Stockholm (Ericsson and Nokia Siemens Networks systems) 2019, in South Korea,
TechologyAMPS, NMT , TACSGSMWCDMALTE, WiMAXMIMO , mm Waves
Frequency30 Khz1.8 Ghz1.6 – 2 Ghz2- 8 Ghz3 – 30 Ghz
bandwidth2.4 Kbps14.4 – 50 Kbps ( GPRS)
64 Kbps – 1 Mbps ( EDGE)
144 Kbps – 2 Mbps100 Mbps – 1 Gbps> 1Gbps
upto 35.46 Gbps
Access LayerFDMATDMA/CDMACDMACDMAOFDM/BDMA
Core LayerPSTNPSTNpacketinternetinternet
Compiled by @altanai

Access Layer

We see that the speed enhances considerably with every generation- 1G offerd 2.4 kbps, 2G offered 64 Kbps based on GSM, 3G offered 144 kbps – 2 mbps whereas 4G offers 100 Mbps – 1 Gbps with LTE technology.

It is to be noted that  one of requirements set by IMT-2000 was that speed should be at least 200Kbps to call it as 3G service and 384kbps ( wth stationary speeds of 2Mbps) for a “true” 3G.

ip transformation in access layer
IP transformation in access layer

Note that voice calls in GSM, UMTS and CDMA2000 were circuit switched but with newer technology voice calls became packet switched too and a lot of rereginerring was required.

LTE (Long Term Evolution) is a series of upgrades to existing UMTS technology involving OFDM and MIMO and newer upgrade were called LTE advanced also. Upcoming 5G offers speeds upto 35.46 Gbps.

Transport Layer

ip transformation in transport layer
IP transformation in transport layer

Session Layer

While 2G introduced services like SMS , MMS , internal roaming , conference calls, call hold and billing based on services e.g. charges based on long distance calls and real time billing which were unheard of in 1G , there were challenges in terms of page load speed for interactive websites .

As 3G came into picture, usecases also enhanced with multimedia features siuch as fast web browsing, maps navigation, email, video downloading, picture sharing and other Smartphone technology

ip transformation in session layer
ip transformation in session layer

Read more about IMS ( IP multimedia System ) IP Multimedia Subsystem ( IMS )

IMS at work from visiting to home location
Access network agnostic

It is noteworthy that SKYPE provided VoIP services ( since 2003) much before mobile phone had 2G/3G ( 2010). In current times with many fantastic options to choose from( whatapp , FB messenger , insta cht , Viber , Hangouts ..) given the high bandwidth with 4G/5G and mych advanced media / signal processing tech , the glocal voip scene is touching 400 mililion subscribers and looks very attractive with 1.5$ billion market.

Bodies and projects behind the evolutions

GSMA

The GSM Association (GSMA) of mobile operators and related companies are devoted to supporting the standardising, deployment and promotion of the GSM mobile telephone system. The GSM Association was formed in 1995. It organises GSMA Mobile World Congress, in addition to smaller, targeted events GSMA Mobile Asia Expo and the GSMA NFC & Mobile Money Summit. Spanning more than 220 countries, the GSMA unites nearly 800 of the world’s mobile operators, as well as more than 200 companies in the broader mobile ecosystem, including handset makers, software companies, equipment providers, Internet companies, and media and entertainment organisations.

3GPP

The 3rd Generation Partnership Project (3GPP) is a collaboration between groups of telecommunications associations, known as the Organizational Partners. The initial scope of 3GPP was to make a globally applicable third-generation (3G) mobile phone system specification based on evolved Global System for Mobile Communications (GSM) specifications within the scope of the International Mobile Telecommunications-2000 project of the International Telecommunication Union (ITU). The scope was later enlarged to include the development and maintenance of the Global System for Mobile Communications (GSM) including GSM evolved radio access technologies (e.g. General Packet Radio Service (GPRS) and Enhanced Data Rates for GSM Evolution (EDGE)) an evolved third Generation and beyond Mobile System based on the evolved 3GPP core networks, and the radio access technologies supported by the Partners (i.e., UTRA both FDD and TDD modes). It is an evolved IP Multimedia Subsystem (IMS) developed in an access independent manner

3GPP standardization encompasses Radio, Core Network and Service architecture. The project was established in December 1998 and should not be confused with 3rd Generation Partnership Project 2 (3GPP2), which specifies standards for another 3G technology based on IS-95 (CDMA), commonly known as CDMA2000. The 3GPP support team (also known as the “Mobile Competence Centre”) is located at the European Telecommunications Standards Institute (ETSI) headquarters in Sophia-Antipolis (France).

OMA

The Open Mobile Alliance (OMA) is a standards body which develops open standards for
the mobile phone industry. Network-agnostic : The OMA only standardizes applicative protocols; meant to work with any cellular network technologies being used to provide networking and data transport. These networking technology are specified by outside parties. In particular, OMA specifications for a given function are the same with either GSM, UMTS or CDMA2000 networks.
Legal status :The OMA is a British limited company.

Standard specifications The OMA maintains a number of specifications, including

  • Browsing specifications, now called “Browser and Content”, previously called WAP browsing. In their current version, these specifications rely essentially on XHTML Mobile Profile.
  • MMS specifications for multimedia messaging
  • OMA DRM specifications for Digital Rights Management
  • OMA Instant Messaging and Presence Service (OMA IMPS) specification, which is a system for instant messaging on mobile phones (formerly known as Wireless Village).
  • OMA SIMPLE IM Instant messaging based on SIP-SIMPLE
  • OMA CAB Converged Address Book, a social address book service standard.
  • OMA CPM Converged IP Messaging
  • OMA Client Provisioning (OMA CP) specification for Client Provisioning.
  • OMA Data Synchronization (OMA DS) specification for Data Synchronization using SyncML.
  • OMA Device Management (OMA DM) specification for Device Management using SyncML.
  • OMA BCAST specification for Mobile Broadcast Services.
  • OME RME specification for Rich Media Environment.
  • OMA PoC specification for Push to talk Over Cellular (called “PoC”).
  • OMA Presence SIMPLE specification for Presence based on SIP-SIMPLE.
  • OMA Service Environment
  • FUMO Firmware update
  • SUPL, an IP-based service for assisted GPS on handsets
  • MLP, an IP-based protocol for obtaining the position/location of mobile handset
  • WAP1, Wireless Application Protocol 1, 5-layer stack of protocols

IR 92 IMS

The IP Multimedia Subsystem (IMS) Profile for Voice and SMS, documented in this Permanent Reference Document (PRD), defines a profile that identifies a minimum mandatory set of features which are defined in 3GPP specifications that a wireless device (the User Equipment (UE)) and network are required to implement in order to guarantee an interoperable, high quality IMS-based telephony service over Long Term Evolution (LTE) radio access. The scope includes the following aspects:

· IMS basic capabilities and supplementary services for telephony.
· Real-time media negotiation, transport, and codecs.
· LTE radio and evolved packet core capabilities.
· Functionality that is relevant across the protocol stack and subsystems.

IR 94 Profile for Video Services

This document defines a voice over IMS profile by listing a number of Evolved Universal Terrestrial Radio Access Network (E-UTRAN), Evolved Packet Core, IMS core, and UE features which are considered
essential to launch interoperable IMS based voice. The defined profile is compliant with 3GPP specifications.

Enterprise communication systems

On premise private branch exchanges ( PBX ) were the first kind of business telephone systems to which the analog PSTN systems of the company were conneced. These analog circuits were then replaced by digital PBX which provided enhanced features liek screening , voicemails , shared lines.

In the current landscape , the digital PBX of the company is connected to the external telco privider via a SBC or SIP trunking service .

An ompremise LAN based voIP system can be accessed from outside via a VPN on SSL/ IPsec. Although it incures greater CAPEX but ensufe maximum control and ownership of the data . Many time the local laws mandate the server to be hosted with a partuclat geographical area too where an on premise setup and data centre is used.

Enterprise communication shifts from on-premise to SaaS (cloud)

As for remote worksforce and employees working from home (such as during lockdown , pandemics ) it is even more crticial for enterprises to maange inter communication between teams and keep the communication private ie not using piblic messaging platforms , hence the role of cloud based PBX integrated with secure and end to end encrypted telco providers is of prime importance .

To read how a SME can setup their own flexible and scable enterprise comunication system read –

VoIP/ OTT / Telecom Solution startup’s strategy for Building a scalable flexible SIP platform https://telecom.altanai.com/2013/11/21/what-should-a-telecom-solution-startup-do/

With the advent of other disruptive technologies such as free and opensource codecs in browser with WebRTC and well defined framework and standards, voIP definetly looks detsined to expand by leaps and bounds.

References