Articles and whitepapers

Wireless Networks (2/9/2004)

By James Hook, Architecta

In recent times, the advent of wireless technology is proving to be the cost-effective solution to cabling problems in homes. It allows the freedom for several computers to access the Internet, and to network other PCs and devices without the need for structured cabling and network points. The thought of installing a distributed home entertainment network in an existing home will no doubt fill most potential customers with dread. The cable installer turns up with a large hammer and chisel and begins chipping the plaster off the walls - the cost and the mess - who needs it? The solution is to turn to a wireless system so there is little disruption to the house.

The networked PC

The wireless network allows flexibility in the home so your PC does not need to be in a fixed location, and with laptops costing much less than ever before, portability is easy.

But your PC does more than connect to the Internet. Multimedia PCs play DVDs, store gigabytes of your favourite music, connect to your camcorder, and play radio stations from around the world. So it is obvious that the next step forward is to integrate all of these functions into your home as a multi-room distributed system. Home networks will be the fundamental backbone of any distributed system. For a wireless system, that is an awful lot of potential data being transmitted around your home, and the potential for interference and clashes grows. Any interruption in service will be a major annoyance to any customer.

Current wireless technology

Current wireless technology (the 802.11 family of specifications) can provide the same service that you receive through your Ethernet cabling. At present, there are three main specifications:

i) 802.11a - works in the 5GHz band and can achieve speeds up to 54Mb/s.
ii) 802.11b - this is the most commonly used form of the technology. Works in the 2.4GHz band and can achieve speeds of up to 11Mb/s.
iii) 802.11g - works in the 2.4GHz band but can achieve speeds of up to 54Mb/s.

This technology is derived from the PC platform, and is typically used to transmit PC files around the home. An example system would be the Barix Wireless Exstreamer, which is a versatile IEEE 802.11b- or Ethernet-connected MP3 audio player for a variety of applications. With the Wireless Exstreamer, the home user can listen to their MP3 collection through the living room stereo or powered speakers from almost any location. The Wireless Exstreamer plays MP3 files from sources such as digital audio servers, PCs or Internet radio stations.

Interference

802.11b networks can operate over 13 channels at 2.4GHz. To prevent interference, neighbouring equipment is usually configured with at least a 4-channel gap. This effectively leads to a maximum of 3 channels operating in any one area (e.g. Channels 1, 6 and 11). A network provider will usually allocate these channels in a hexagonal pattern (similar to that used by mobile telephone networks) to prevent overlap of matching channels. For a single system in an area, this is acceptable, but if another system appears, interference between systems will result unless the systems can be manually configured not to clash. However, because it is quite probable that the first system on site will have covered as much of the area as possible with access points, co-operation based solely upon channel allocation might not be possible as more systems are added.

One possible solution is a system implementation that caters for the range of possible uses demanded by the consumer. As yet however, this is not available for wireless applications since, until now, these have been developed with the PC in mind.

Non-PC applications

But what if you do not want to use your PC for music and entertainment, or you do not even have one? You have spent a lot of money on quality audio equipment and you want to be able to listen to your CD in another room. Although this end of the market is in its infancy, it is about to catch up. While wireless speaker systems are nothing new, thanks to the wireless links being analogue, they are notorious for poor sound quality, interference and sounding like transistor radios.

More robust digital wireless links are now available and are set to appear in some leading brand products in the near future. With some add-on equipment that is already available, the ARCHITECTA Wireless Link for example, takes line-level audio and reproduces it at multiple locations around the home in a format that does not clash with 802.11 systems.

Another example is Bang and Olufsen, which produces sound systems with a remote control interface that allows the consumer to place speakers in other rooms, and control the CD player via the speaker in that room.

The next logical step is to provide such control without the wire, and to control the DVD player, the DAB radio or the VCR, so you can choose to listen to or watch what you like, where you like, and without calling in the builders.

James Hook is the Managing Director of Architecta, electronics consultancy and specialist in CD-quality digital wireless transmission.

www.architecta.co.uk