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Wired, Wireless and IEEE1394 Networking (18/10/2003)

By David Stone CEng MIEE

The home entertainment network is poised to make a debut, but what will it offer the consumer? At present, the consumer does not know what a network can offer, and is probably confused by talk of the Internet-connected fridge. So let us look to the future and think of the possibilities:

The first function of a network is to extend the sphere of the entertainment equipment, possibly from the living room to the kitchen. A remote in the kitchen could select the radio channel or CD track on the equipment in the living room and play the sound in the kitchen. It could alter the volume or mute the sound when the phone rings. These are useful features and are already available from specialist suppliers. The system could easily be extended to cover the bedroom and bathroom, so that the news programme can follow the people preparing for work, or the music follow from the living room to the bedroom. The next stage is to add video, so that the satellite receiver can be shared between the children's room and the lounge, or the DVD can be watched in the bedroom. But how do the signals travel between rooms? Is it wired or wireless?

Wireless and Wired Options

Wireless connections between electronic equipment sound like a good idea. They have no visible medium, which is aesthetic, but are they adequate to transport the data? Present technology dictates that IEEE802.11 (Wi-Fi) radio links are used, operating at around 2.5 or 5GHz. These microwave frequencies are reflected from solid materials, such as walls and floors, and do not penetrate very far. They do pass through timber fairly well, but aluminium-backed plasterboard is an almost ideal reflector! The effect of this is to make coverage unreliable throughout a house, some places in each room work and others will not, some places also give error-prone paths due to the reflections. Thus the ideal of freely-sited equipment is not realised. It is convenient to use wireless in one or two rooms for a laptop-to-Internet connection, and in this case, one may move slightly if the link is not working. However, between fixed items of equipment, which have power and aerial connections anyway, a wired network will probably work better. A single wire between each piece of equipment is simple and cheap, with radio connections to portable controlling devices such as remote controls, the webpad or laptop computer.

The Benefits of IEEE1394

A common criticism of wiring is that it is unsightly and difficult to install, but real networks such as IEEE1394 (FireWire or I-link) use a thin cable which can be hidden under carpets, and can be made in a flat shape which is even less visible. Link length between rooms is also often mentioned, but this is also easily overcome with 1394 networks. Each equipment has either two or three connectors, and these are simply daisy-chained together with branches wherever is convenient - the network is fully self-configuring. Long runs would need a special cable, but again, these could be made available at low cost.

Quality of service

IEEE1394 also has another big advantage, and this is that it delivers a consistent quality of service to the connected devices. Video transfer can take large bandwidths on the network, and in practice, a network will be required to support several video sources. The network allocates a fixed bandwidth for each link, which is always available, whatever other traffic is being carried; non-real-time services, such as remote control data, are then free to use whatever is left over. The real-time data, video and audio, use isochronous (regularly-timed) transport mechanisms whilst the Internet data or control information use an asynchronous protocol. Other types of network, such as Ethernet or 802.11 use a random mechanism to control the transfer of data, all data will be carried at some time, but when, is not specified. This means that connected devices need to buffer a lot of data which is then used up whilst waiting for the next data to arrive. Isochronous transport devices know exactly when to expect the next block of data, so the maximum buffer is defined. The impact of this to the consumer is lower costs of equipment and defined performance, no matter how many devices are connected to the network.

It is important to remember consumers in this discussion. They will not be interested in the above issues, but expect products to work together immediately, out of the box. They expect devices to connect to one another with an absolute minimum of setting up. They will not tolerate having to install new software in old products, or for these products not to understand their new equipment and what it can do.

adding speaker audio to a notebook computer using a single cable with IEEE1394

Standards

Underlying any networking system are the standards, which define operation and protocols at all network levels, from user controls to data transport. The network with these standards in place and implemented by all the manufacturers is the one that consumers will want. Wireless and Ethernet for home networks, do not have many of these standards in place, and so are likely to offer poor functionality. IEEE1394 does have standards for everything, and these are implemented in many available high-end products. It has a strong trade association that leads interoperability testing between manufacturers, and has many years of the standardisation process behind it.

Conclusion

Customer satisfaction and quality of service are the two factors which will control the uptake of home networking of entertainment equipment. The risks of difficulty are much greater with a wireless network delivering AV content, although it is nearly ideal for remote controls and two-way portable items such as webpads. Internet content delivery is close to commercial adoption, and this will require that AV equipment has web access, and will be automatically connected for AV networking. IEEE1394 has several years of track record of AV networking, and is the leading contender for the home market. Proponents of other network technologies have to prove that their networks will satisfy the consumer, provide quality of service, and will enable out-of-the-box operation. Computer and software companies are trying to take over consumer electronics with buzz phrases such as 'home server' and 'wireless connectivity,' but they fail to explain their offerings in consumer terms. If the consumer is satisfied, the home network will sell, if not, then networking will be a problem for everyone.

David Stone CEng MIEE is Principal Engineer at Oxford Semiconductor Ltd. Oxford Semiconductor designs and manufactures communication bridge and connectivity ICs for interconnecting a broad range of consumer electronic products, from disk drives and computer peripherals to digital cameras and MP3 players.

www.oxsemi.com