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Copper: the road ahead

Communicate - April 1, 2000

Malla Lakso explains digital subscriber line (DSL technology which has given life to copper local loops.

THE GOOD OLD TELEPHONE LINE is ubiquitous. With more than 600m copper phone lines installed globally, the world has a major resource which will still play an important role in the future of communications in this century. Just as it has done during the last.

Digital subscriber line (DSL) is the technology to breathe new life into the copper pair, bringing together more cost-efficient voice services and a high-speed transmission pipe for bandwidth hungry applications and their end-users. But more importantly, the combination of the humble copper pair and DSL will provide the wires behind today's wireless revolution, enabling network and service providers to bring their services, brand and mobility to fixed locations at a reasonable price.

WHAT IS DSL?

DSL technology allows network operators to effectively boost the bandwidth capacity of their existing copper phone lines to deliver data speeds of megabits per second. It also enables voice and data to be carried over the same copper line together, making use of the copper phone line much more cost-effective than today.

Moreover and perhaps more importantly, DSL provides always-on connectivity for end-users which in effect means there is no need to go through the laborious dial-up sequence every time the end-user wishes to check out a new service. This, in turn, has implications for billing and charging, providing greater scope for a variety of charging models. Flat fee billing is therefore not necessarily the only model. For example, the always-on connectivity provided by DSL means network operators and service providers could offer a flat rate fee for a certain amount of data downloaded per month plus x-amount of Euro's-per-megabit exceeding the agreed monthly amount.

DSL also delivers the pipe that will enable service providers to provide `richer' content and the best solutions on the market today that take advantage of the newest technologies, such as point-to-point protocol over Ethernet (PPPoE) that cater for service selection and multi-user sessions over the same connection.

Finally, DSL can be integrated with the latest wireless technologies, such as wireless LAN, to bring mobility to fixed locations, whether home, SME or SoHo.

VOICE AND DATA INTEGRATION

Although broadband IP access based on DSL enables service such as always-on Internet access, remote working, e-commerce and streaming media, voice services can also be combined with these new services in new innovative ways. End-users, whether residential or business, require integrated data and voice applications. Voice, the most traditional service of all, has emerged as a major application for DSL.

Not only is copper available to millions of residential homes but it also reaches many business and by bundling voice with the existing data services over DSL, network operators and service providers can gain additional revenue.

Competitive local exchange carriers (CLECs) in the US have already paved the way and started deploying DSL successfully for both data and voice services. In Europe, deregulation has also changed the competition. Incumbent operators can protect their market share by pre-emptive DSL deployment, to save copper pairs and cost, whereas challengers are interested in maximising the utilisation of rented copper pairs.

Voice over DSL (VoDSL) enables the sharing of one copper pair between several lines and data connections. DSL provides the means for local loop emulation of PSTN service with all voice calls transmitted to the PSTN network, which provides the voice services.

VoDSL means transmitting voice in packets over DSL. It enables operators to provide multiservice access to small businesses and provides easy evolution by replacing TDM transport with DSL. Voice switching and services are provided by the existing PSTN network. This is important for incumbent operators who have made enormous investments into the installed base of PSTN equipment. There is no need to replace PSTN equipment that has not as yet been depreciated.

For small and medium-sized enterprises (SMEs), Voice over DSL allows them to receive one managed service for both voice and data. This creates new markets for application service providers (ASPs). ASPs can use more bandwidth at a reasonable price and offer new services to the SMEs, services such as web page hosting, bookkeeping, IT management, enabling the SMEs to use their resources to concentrate on their actual business.

For SMEs, Voice over DSL provides four to 16 voice phone lines. Integrated access devices with phone and LAN interfaces allow voice and data services to dynamically share the DSL access line. Voice is always given a higher priority to guarantee toll-quality voice. When adding integrated wireless LAN to this combination, SMEs and residential end-users gain the benefits of mobility in a wireless environment with high-speed voice and data services.

THE EVOLUTION OF VOICE SERVICES

The data networking market is growing much faster than wireline voice. The IP protocol dominates in data networks, and convergence towards IP is taking place both in fixed and mobile networks. New networks are being built based on the needs of data networking. A single network for voice and data enables more efficient use of bandwidth than two separate networks.

IP-based traffic and services are growing fast in proportion. IP telephony bypass solutions allow service providers to transport voice and fax traffic over an IP infrastructure connecting to PSTN/GSM exchanges in various countries. In the IP telephony industry this has been the first step in converging PSTN/GSM and IP networks, allowing operators and service providers to optimise their transport of voice and data services and gain initial understanding of offering voice services in an IP environment.

At a later date, the network is expanded to include IP originated calls from the service provider's IP network. This phase expands the network to include IP telephony client-side terminals. Voice services will eventually migrate towards IP, when appropriate, reliable services become available in the IP network. DSL networks will support this natural evolution path.

Service continuation through evolution rather than revolution is a key requirement especially for corporate customers as they put high emphasis on maximising the return on investments already made. Likewise it is crucial for established operators that they can provide a smooth expansion and evolution from the current PSTN/GSM voice service to `rich services' enabled by IP. Lack of standardisation has created single-vendor implementations, but support for standards will be crucial.

DSL technology comes in a variety of different `flavours', each suitable for various needs. The main ones are:

* Asymmetric (ADSL) -- Full-rate ADSL delivers asymmetric, high-speed transmission, providing speeds up to 8 Mbps downstream, i.e. towards the end-user. ADSL supports real-time broadcast services and prerecorded interactive video services; and multiple video and data activities can be underway simultaneously. Primarily aimed at residential and SoHo customers for web surfing, file downloads, distance learning, real-time broadcast, and interactive video.

* ADSL Lite (G.Lite) -- A standardized asymmetric high-speed service that provides roughly 1.5 Mbps downstream and 0.5 Mbps upstream and is ideal for the cost-conscious mass-market consumer and Internet user. ADSL Lite provides for splitterless installation which means there should be little need for a truck roll to customer premises. ADSL Lite is seen as the more economical version of full-rate ADSL and therefore likely to be most attractive to casual Internet users for basic web surfing and remote data access.

* High bit-rate DSL (HDSL2) -- HDSL2 is a standards-based technology that uses a single twisted copper pair (rather than two twisted pairs required by HDSL) to deliver symmetrical high-speed DSL service at rates up to 2.3 Mbps), or 24 voice channels. HDSL2 enables service providers and operators to deliver twice the bandwidth on the same number of pairs used to deliver traditional HDSL. Standardised technology provides for vendor interoperability. HDSL2 is of particular interest to businesses and teleworkers for such services as high-speed file transfer, and voice and data integrated access.

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