Annex B: Telecom Document: How An NGN-Based Local Service Differs From PSTN Local Telephone Service
Introduction
The following seeks to describe characteristics of NGN-based services, in particular noting differences between this future world and current services.
These changes reflect both the deployment of services based on NGN technology, and the changing service models arising from an "unbundled" market environment with separation of LLU, wholesale access and retail services elements.
Access Connections in an NGN World
The NGN model is based on delivery of multiple services over a single broadband access connection, typically based on DSL technology,25 connected to a core network based on Internet Protocol (IP) technology, from which all services will be provided.
Thus the service will comprise:
- An unbundled copper local loop, as an input to
- An unbundled bitstream Wholesale access service such as Enhanced UBA, as an input to
- A retail service incorporating core network and customer premises-located equipment and associated service and support functions
» Today, voice and broadband services are delivered over the same pair of wires, but by different connections to different networks and can be readily treated separately – in future they will be more closely linked.
» DSL technology does not generally support line powering, unlike today's telephone service in which phones can be powered from the network (see later discussion on CPE power requirements).
Retail products from difference service providers will support different combinations of core network and customer premises equipment capabilities, which will be integral to their product offerings. The underlying wholesale access service may also vary between retail service providers, as they choose access products appropriate to their retail offerings.
Similarly, some service providers may choose to use their own DSL (or similar) equipment on unbundled local loops, along with their own core network and other capabilities.
Diagram 1: Service is Provided Over a DSL Connection and Terminating Device
A terminating device (sometimes called an IAD or Residential Gateway - RGW) will be deployed in the home and services are provided from that device. The device can connect to existing home wiring existing phones can continue to be used throughout the home.
» The RGW is part of the retail product ― it is part of the way the retail service set is defined
» The RGW changes the nature of the home network (from just wires, to a network connected by electronics) and needs to be powered from within the home (see later discussion on line powering)
Connections to a PC or new devices such as SIP phones will be via a LAN connection to the RGW, which may need new cabling or a wireless LAN.
An NGN equivalent of today's single analogue line would be provided as an analogue phone connection to the RGW (there is no analogue voice connection from the network as with the PSTN). Other NGN-based services would be available though the RGW, though additional equipment may also be required.
It will be possible for customers to use their existing touch tone (DTMF) telephones. However, modern technologies do not support decadic (pulse-dialling) phones, and some devices which use an analogue modem (e.g. faxes, computer dial-up modems) may not function as previously.
» The Voice over IP (VoIP) technology used in the NGN to provide voice services will impose some constraints on services and devices which can carried over from PSTN to NGN
An NGN Calling Product
The NGN can provide the equivalent of today's single telephone line (i.e. a combination of access to the network and the calling product). It can support the use of existing phone numbers and existing billing constructs such as free local calls.
National, international and fixed to mobile phone calls could still be made, the price will be determined by the market at the time.
It will still be possible to support dialling 111 for emergency services. You may need to provide your location information to the operator as customer location information may be difficult to capture or become less meaningful as the number of calling products offered by internet based service providers grows.
» VoIP-based services are inherently less tied to a particular physical line than a PSTN-based service, and may become increasingly "nomadic".26 As a result, location will be less able to be inferred from phone numbers.
A range of value added services (for example voicemail or caller ID) will be available depending on customer and market demand.
Ability to Connect to the Internet via Internet Products
In the NGN, Internet access (if provided) is a retail service provided over the underlying broadband access service. However, whilst the access service and Internet access are independent, service implementation generally links the retail services collectively provided over the access connection. A "primary line" voice service also needs to be closely linked to the underlying access service to provide the desired service level characteristics.
» A "primary line" voice service would most likely have to be obtained from same provider as an Internet access service.
» Supplementary services (including voice) not requiring specific traffic handling will most likely be available from other service providers, accessed via the generic Internet Access.27
With VoIP, support for analogue modems (e.g. PC modems) is limited. Instead, PC's should connect directly to the RGW (or via a LAN in the home) to the native IP connectivity use the broadband IP connectivity of the DSL line.
» Internet access over the DSL connection can be provided at a similar speed to existing dial up connections. With removal of the PSTN, dial-up Internet access will not be available.
» Connecting via the RGW instead of via dial-up modem may require some changes to the customer's PC, depending on RGW capabilities
Quality of Service
Service standards are likely to be a key differentiator between different retail service offerings in the NGN world, with service offerings likely to range from basic Voice over Internet offerings (e.g. Skype), to higher quality (and most likely, higher priced) offerings intended to mimic or even exceed the traditional PSTN user experience.
These offerings will reflect choices of both suppliers and customers, including choices in technology and operating models on the part of service providers, and which underlying wholesale access products they may choose to use (or build themselves). Customers' choices will reflect choice of retail access provider, choice of providers of any supplementary services, and choices in CPE.
» Service quality will likely be reflected in a range of service offerings from different providers with different performance and user experience.
» Customer choices in relation to both service and service provider choice, and their own choices in customers devices, will influence their own user experience, and to some extent that of those people they communicate with.
Telecom anticipates that overall product availability and performance for any NGN-based primary line voice service will be comparable to that provided today. This assumes defined service levels for connectivity which require differentiation of voice traffic in the access network.
Whilst the NGN is a fundamentally different network to the PSTN, and there will inevitably be differences in user experience in terms of features and performance, it will have many similar characteristics to the current networks including duplication of key elements, and generator or battery backup for equipment in exchange buildings and cabinets.
» Service availability and performance is expected to be broadly similar to today's PSTN, though there will be differences in customer experience.
Remote Customers
Different technologies will be used for some rural customers and customers currently served by long copper lengths. For example, where wireless access is used to provide service, the service may be provided directly to a handset or terminating device in the home.
Whilst different "last mile" technologies may be used and each introduce their own peculiarities, the core of the NGN will be common, and consequently many of the differences described above will apply regardless of the access technology used.
CPE Power Requirements
Most of the "last mile" technologies which will be used in the NGN have one common feature: they require local power for a device at the customer premises. This is true of DSL,28 fibre and wireless-based access technologies. Furthermore, end user devices in the home increasingly require local powering to operate, be they existing cordless phones, or new devices such as IP phones or PC-based software phones.
» Line powering is not a feature of Telecom's wholesale DSL access services
» Providing continued operation of telephone service in the event of mains power failure at the customer premises will require local battery backup for devices at the home.
A backup battery pack option is technically feasible for mains-powered devices. Such devices may incorporate an integrated re-chargeable battery pack, or such a facility could be provided by a third party device available through mass market electronic consumables stores (such as Dick Smiths).
Those familiar with such devices as cordless phones will recognise that in time, rechargeable batteries may maintenance or replacement. Service providers may choose to offer support arrangements or other assistance to customers (e.g. alerts when batteries require replacement). Customers may also choose not to have any backup capability, and instead rely on such things as mobile phones to provide service in the event of power outages.
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