So what is the big deal? Well for many years telecommunications companies and ISPs have delivered data services and telecommunications services over entirely separate infrastructures, although over the Last Mile the copper local loop has served as the delivery medium for both a local telephone service and the provision of DSL (Digital Subscriber Line) services. Even prior to that, the old Dial-Up Internet services utilised the local loop to provide a very modest 56Kbps data service in addition to telephony.
Telephone signals, once converted from analogue to digital would be multiplexed using TDM (Time Division Multiplexing) techniques to forward telephone conversations from the local street cabinet to the local exchange and beyond using PDH (Plesiochronous Digital Hierarchy) or more recently SDH (Synchronous Digital Hierarchy) where each digitised telephone conversation comprised a 64Kbps digital stream.
A device known as a DSLAM (Digital Subscriber Line Access Multiplexer) connects the local copper loop connections and through the use of modems, converts the analogue signals into digital data streams downstream and upstream. The incoming streams are multiplexed and sent into the wider provider network for routing to the Internet. The telephone portion of the analogue signals on the local loop are filtered off to the PSTN (Public Switched Telephone Network).
An NGN is the design of an network architecture to transport all forms of media such as voice, data and video in order to offer all of these services over a single connection to the consumer. All services are designed to be delivered over an IP connection so that traditional voice services utilise VoIP (Voice over Internet Protocol) with SIP (Session Initiation Protocol) replacing the traditional methods of signalling and call setup.
Video services such as IPTV (Internet Protocol Television) and VoD (Video on Demand can share the same IP connections as the VoIP and general data services.
The NGN utilises an IP packet based network often running MPLS (Multiprotocol Label Switching) to QoS (Quality of Service) enable the network, ensuring each service is provided with the ideal network conditions for optimum transport with little of few errors. The provider backbone will comprise fibre optic connections and in areas of the network where large volumes of traffic are expected DWDM (Dense Wavelength Division Multiplexing) techniques are used to create many multiple Gigabit speed channels of single strands of fibre.
In the UK BT (British Telecommunications) designed it's NGN and labelled it 21CN (21st Century Network), and many other operators worldwide are deploying Next Generation Networks.
For the VoIP services Softswitches were developed for the control of the VoIP services and to provide an interface with the traditional telecommunications networks through the use of Signalling and Media Gateways. ETSI (European Telecommunication Standards Institute) and the 3GPP (3rd Generation Partnership Project) defined the use of an IMS (IP Multimedia Subsystem), essentially a framework for the delivery and control of multimedia services over IP. The IMS separates the control at the service layer from the delivery at the access layer.
So, in brief an NGN is an architecture used by telecommunications companies and services providers to deliver voice, data and video services to consumers and businesses over a single high speed network architecture utilising Internet Protocols. A clearly defined service layer sits separately above the connectivity or transport layer to allow for the services to be accessed and selected. These services are normally grouped together in blocks such as routing and transmission, provision and billing.
This article on Next Generation Networks was written by David Christie, MD at NSTUK Ltd, Website: http://www.nstuk.com