|Topic:||NGN voice migration|
|Author:||Dr Ing. Ziaedin Chahabadi|
Dr Ing. Ziaedin Chahabadi is the CEO of Keymile. Dr Chahabadi is also the Chairman and CEO of the Executive Board of Keymile International GmbH., Dr Chahabadi served previously as a member of the of the Quante group’s Executive Board. Prior to Quante, Dr Chahabadi was one of the founding members of Kommunikations-Elektronik GmbH, where he was the Head of the Technology section and Deputy Managing Director. Upon earning his doctorate, Dr Chahabadi joined Kabelmetal Electro GmbH in Hanover, a subsidiary of the Alcatel group, as Head of the Department of Transmission Technology. Dr Ing. Ziaedin Chahabadi earned his doctorate at the University of Hanover in high-frequency engineering.
IP networks lets operators provide a great many advanced services using a single network. This reduces both capital expenditures and operational expenditures since single, converged, IP networks’ architectures are much cheaper to run than the separate networks traditionally used for voice, data and video services. Operators with heavy investments in traditional networks can use IP-based Multi-Service Access Platforms to convert from traditional voice to VoIP and use IP-based Multi-Service Access Node (IP-MSAN) to integrate fixed line networks within an IP framework.
Looking back ten years ago, the only telephony service a residential customer had available was voice service. Bringing DSL to the customers increased the bandwidth and enabled the concurrent use of telephony and Internet services. For the service providers, Internet service provisioning implied building a data network based on packet transmission in parallel to the voice network, based on TDM transmission. The ever-increasing data bandwidth of broadband access lines has now reached a point where, in most cases, voice services can easily be transmitted over the broadband lines, without using much bandwidth. To remain successful in a competitive environment, the network and service providers must reduce their capital expenditures by sharing a single, joint, network infrastructure. There is also a need to cut operating expenses by simplifying operation and maintenance and to increase revenues by offering new services. In other words, the existing parallel networks have to be converged – merged – into a single, universal, network that can offer all the services customers need today and tomorrow. Implementing VoIP Legacy, TDM-based, PSTN (public switched telephone network) voice networks are taking two different approaches to evolve into packet-based networks that offer voice over IP (VoIP): The next generation network (NGN) approach treats NGN as a service application that transmits voice over managed and secured IP networks, with well-defined guarantees for end user reachability, communication quality, reliability and connectivity, while supporting services inherited from the PSTN. The Voice over Internet approach provides Internet telephony with voice traffic routed on a best effort basis as an end-user, peer-to-peer, application that works through the Internet; it offers limited service quality. From a telephone service provider’s perspective, as they migrate to an end-to-end IP-based infrastructure, the NGN approach becomes a more efficient way of routing and delivering voice traffic, since the Internet calls share bandwidth on the network with other applications. Voice migration An IP-based Multi-Service Access Platform is an advantage when converting from TDM-based voice to VoIP services. The fundamental goal of an IP-based Multi-Service Access Node (IP-MSAN) is to integrate all service groups usually available on fixed line networks – i.e. voice, data and video and provide all the associated services. Telephony is one of the most important services. On the one hand, because today most revenue still stems from the standard telephony service, and on the other, because this segment is where operators need to act most urgently – due to the potential to enhance voice services in public networks. In the future, operators must still be in a position to implement, with relative ease, a full range of ‘cash cow’ services, which comprise the greatest share of revenue and profit. In fixed line networks, such services include POTS (Plain Old Telephone Service) and ISDN (Integrated Services Digital Network) telephony, as well as the two Mbps standard fixed line connection to link up private branch exchanges, mobile base stations, surveillance technology and much more. These services should also be available in an IP-based access network. Quality of Service and VoIP Looking at quality of service (QoS) in the VoIP application, a distinction must be made between the core IP network and the access network. Concerning the core network, IP QoS is based either on MPLS (Multi Protocol Label Switching), or by over-provisioning the available bandwidth. Guaranteeing QoS in the access network requires more attention, as the available bandwidth is in general much lower than in the core network. The traffic requirements for the voice service are quite predictable, enabling service providers to introduce QoS by static provisioning in the network. When using an IP-MSAN at the interface between access and core network, with the aid of advanced prioritising, filtering and queuing methods, voice and data can be gradually transmitted, with differing quality, to ensure end-customers obtain the best service quality. VoIP-gateways Many operators nowadays still use 64-kbit TDM technology in their voice exchanges. This will continue to be true for some time to come, due to the great investments they have in this sort of equipment and its long-term depreciation. As a result, in addition to modern Voice-over-IP technology, modern IP-MSAN platforms will continue to use TDM interfaces – between subscribers and the exchange. As the name IP-MSAN already suggests, this category of access solutions also includes IP functionality. VoIP gateway functions are very important. They convert POTS and ISDN subscriber interfaces to RTP (real time protocol) Ethernet packages and make them manageable by using signalling via a softswitch, or call server. This sophisticated type of telephony saves substantial network operating costs, as Ethernet transmission technology is used and the traditional digital exchanges can be replaced by just a few softswitches. As far as subscribers are concerned, the same familiar services (i.e. POTS or ISDN) are implemented that the customer recognises from TDM technology. Ideally, subscribers will notice no difference after network conversion from TDM to IP and can continue to use their favourite terminal equipment (like DECT telephones, ISDN private exchanges, fax machines etc.) without any problems. However, many network operators have not yet migrated their TDM voice network entirely to VoIP technology. There are many reasons for this. To supply these providers with problem-free access to modern NGN technology, advanced applications of IP-MSAN use a hybrid backplane architecture, which can also provide POTS and ISDN subscriber interfaces. The TDM interfaces use the TDM backplane in this architecture and the packet-driven interface boards use the Ethernet backplane. Therefore, since both TDM and Ethernet technology are supported by hardware, they can be used together without complex emulation technology. With hybrid boards that can access both backplanes, migration scenarios can be easily and efficiently implemented – without exchanging existing hardware. This route protects the operator’s existing investment and provides the opportunity to enter the convergent all-IP world gently. Everything a fully functioning NGN requires is fulfilled. The outstanding success of VoIP technology in public and private networks is unstoppable. Using carrier-class IP-MSANs in the access networks exploits the advantages of two technological worlds. The IP-MSAN converts the existing POTS and ISDN connections into VoIP and at the same time implements broadband All-IP-connections via copper or fibre optic lines. This allows operators to migrate their networks today to more affordable, scaleable and future-proof VoIP technology, without affecting quality. Good arguments can be made to counteract customer scepticism re safety, quality and stability. Setting up IP-MSANs during the migration to an IMS network architecture is an important and necessary step that prepares the access network for future conversion to an all-IP operation. Thanks to the ETSI TISPAN-Standard, in the future, an IMS-Media Control Layer will be able to manage IP-MSANs as full network elements. Finally, it is worth noting that many network operators worldwide are already aware of the advantages of using the IP-MSAN and in the next few years will convert their access networks entirely to IP. From marketing, technical and business standpoints, the potential to gain a competitive edge with IP is extremely high, so it is particularly important not to compromise when selecting the technology for the access network.