Cable modems - standards sustain optimism

May 2002

Despite an on-going split over its central network standard, the European cable modem industry is finally reaching agreement on common standards for media delivery. It needs to, if it is to stand any chance of competing with incumbent DSL operators which have superior market share advantage

Headlines torn from business journals and research papers bring good news and bad to the broadband cable sector. The good news: demand for broadband across Europe seems to be entering a new phase where dramatic growth is a fact of life. Analyst Screen Digest reports that combined cable and DSL penetration into European households stands at 1.79 per cent - itself a significant rise from 1999's 0.48 per cent - but that it expects penetration to reach 21 per cent during 2003. The bad news, if it can be labelled as such, is that dramatic growth brings its own problems, in particular making finding an equitable balance between costs and revenues more urgent.

For operators, the means to this end is to be able to deliver a broader range of services to its customers. Many operators have already added Internet access - typically at 0.5 or 1 megabit per second - to their existing television channels, encouraging existing customers to spend more. This has led to the use of two devices for sending and receiving cable-based signals:

• the set-top box for television sets
• the cable modem for PCs

Most cable modems are self-contained devices that plug into a PC through an Ethernet network point or a USB connection port, although the latter is not an ideal mechanism. Moreover, the use of the term 'modem' is not wholly accurate for a device that is just as close to a network router in nature - but it does help explain its function to consumers. In one sense, the use of the cable modem as a stand-alone device is a blip in the development of set-top boxes. The split distribution of content between different devices is seen as a barrier to the development of new services, but convergence between the cable modem and the set-top box depends on common standards and subsequent cost efficiencies.

Establishing standards

Standardisation has moved to the top of the cable sector's agenda in recent times. It is an issue on which there was once little consensus: operators entering the early cable market had to source network infrastructure and connection equipment through the same manufacturer to guarantee compatibility, such were the limits of cross-platform cooperation.

It was finally operators in the US, however, frustrated by the lack of progress in establishing cable modem data standards, that banded together in 1997 to establish the DOCSIS (Data Over Cable System Interface Specification) standard. Recently rebranded as the 'Certified Cable Modem Project', DOCSIS manages issues like data transmission and prioritisation of different classes of service.

Released this year, DOCSIS 1.1 is the current implementation of the standard. While DOCSIS 1.0 was a no-frills initiative to quickly establish a common vanguard against rival technologies to cable, this new specification provides support for packet-based services such as IP-telephony and multimedia delivery, allowing operators to evolve the services they offer customers.

DOCSIS 1.1 is the first implementation to guarantee Quality of Service for IP voice applications, designating voice packets with a higher priority identification tag than data packets such as emails to better enable real-time delivery. Distinguishing these services to prioritise them also enables operators to charge separately for different levels of service. In Europe, the 'EuroModem' standard was the first to be established; it was originally known as DAVIC/DVB, after the two cable TV groups that drafted the specifications. However, those manufacturers that were more geared towards PC-based cable modems than TV-based set-top boxes opted to draft a rival specification, based on the successful DOCSIS formula.

The 'Euro-DOCSIS' standard sees slight alterations to the DOCSIS specifications, to fit European frequency allocations and to deliver the higher bandwidth needed for video feeds encoded in PAL or SECAM. Additionally, Euro-DOCSIS takes a broader view of cable network standardisation than EuroModem, although neither has a clear lead.
The divide is broadly regional in nature, with the UK established as the heartland of Euro-DOCSIS. One of the first European networks to support IP-telephony was announced recently in Germany, where PrimaCom AG will use Tellabs cable modems certified for Euro-DOCSIS 1.1.

Standards in support

Whatever the merits of the rival specifications are, at least the effort to define services to operate over these standards seems to be going more smoothly. PacketCable is a standard defining IP-based multimedia services. Voice-over-IP (VoIP) telephony is the first such service to receive a detailed specification in PacketCable 1.0; prospective services in future drafts include media streaming, video-conferencing and multi-player gaming.

As with DOCSIS, there is a European equivalent for PacketCable. The EuroPacketCable Forum is a body publishing specifications for VoIP services, as well as advanced data IP services. Founding members include Broadcom, Motorola, Pace Micro Technology and Thomson Multimedia. The standards are derived from the existing US PacketCable specification, designed to operate over DOCSIS, but are equally compatible with Euro-DOCSIS and EuroModem, which should assure EuroPacketCable's acceptance in the marketplace.

Also able to work with either Euro-DOCSIS or EuroModem, DVB-MHP is the interactive media component of the far-reaching Digital Video Broadcast project. It is intended to cement interoperability between digital media broadcast across all platforms, including terrestrial, satellite and cable. MHP defines the framework for interactive applications within DVB's MPEG-2 networks.

The software for delivering MHP applications uses Java Virtual Machine (JVM) technology, which enables a single software standard to be deployed across different platforms. The DVB-J standard ensures that if a platform can support JVM, it can deliver MHP. The use of JVM separates software from hardware, so that operators are free to shop around for applications from different vendors.

Hardware integration

The Euro-DOCSIS certification body is tCableLabs in Belgium, which has so far certified cable modems from 19 vendors. It also awards qualification to products that integrate additional functions: this had been confined to cable modem termination systems, but December 2001 saw the first qualification of an integrated consumer set-top box from Motorola.

Motorola's DVi 5000+ set-top box vividly demonstrates the future of cable modem deployment, merging the technology with broader digital platforms. The set-top box delivers DVB-C video streams and cable modem data from a single box, allowing broadband data services to be delivered to a wider range of devices.

Such integration is set to define cable modem rollout in the future, allowing operators to meet the customer need to receive services through multiple devices, particularly the axis of the PC and the television set. The ultimate aim should be to offer the full portfolio of services across any platform, but for now the imperative is to permit more flexible delivery of services into multi-device homes.

Wireless standards should also play an important role as soon as cost efficiencies permit integration. Emerging as the dominant wireless standard, 802.11b is fast enough to support Internet and VoIP services, while successive standards (802.11a awaits European certification) will support packet-based video delivery.

IEEE 1394 is a cable-based technology used to link devices together for data exchange, and can deliver full-screen video in real time. As the use of IP to deliver all services spreads, these technologies will allow for in-home redistribution of data - moreover, the presence of these technologies in customers' existing PC equipment should ease adoption.