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Why we may never see Cat.8 cable
by Adrian Berry
There is a little-known network scheme on the horizon that may change network wiring forever. It's called Homeplug. And it involves running Ethernet signals over the same wiring used to deliver power to the average lightbulb - at the same time.
Several years ago Northern Telecom got involved with a company in Great Britain to attempt to deliver home Internet service over power company wiring. It had significant problems which were difficult to solve at the time, and the concept seemed to disappear under the radar. However it still exists, and is slowly gaining popularity in Europe and the Third World, as "Broadband over Powerline" (BPL), a delivery method for utilities to provide IP services as far as the home. But if you check Linksys's website today, you will find a transmitter-receiver pair offered which Linksys claims will provide up to 14Mb/s of Ethernet connectivity over regular house wiring inside the home. Moreover, some products now claim the capability of providing up to 150Mb/s on the same infrastructure. The list of companies involved includes not only Linksys (Cisco)
but also other heavy hitters such as GE, Motorola, Samsung and Sony. There is even a company (Avisto) offering software to control Homeplug devices in a commercial setting via SNMP (that's Simple Network Management Protocol - not, as I heard some 'expert' say a while back, "something to do with email").
While 14Mb/s is not earth-shattering, and certainly cannot compete with current Gigabit Ethernet offerings, it is a start. Given that Internet connectivity to most households is under 3Mb/s, this is more than enough to provide Internet service to a few PCs in a home.
But what other uses might there be for this technology? After all, most people these days have either run their Category 5/6 cable already, or have jumped to WiFi, so this would appear to be a non-starter right out of the gate.
When PCs were in the pioneering phase, a firm called BSR marketed a line of light switches, power receptacles and associated controllers under the brand name X-10. They even had a computer program to control these devices; it ran on an Apple II (you may have seen one in a museum). Compatible devices are still available today, sold by large electrical manufacturers right on down to Radio Shack. Each device, be it a wall switch or AC receptacle, contains an X-10 transceiver which transmits and receives a low-speed proprietary data signal over the same power lines that it is controlling. Consequently there is no secondary control network; the existing wall switch or AC receptacle is simply removed (after turning off the power, of course) and the X-10 device wired back in place. Then, from small control stations that simply plug into an AC socket anywhere in the house, the
homeowner can turn appliances on and off and dim lights, either individually, in groups or according to a schedule.
What if the X-10 transceiver inside these devices was replaced with a Homeplug transceiver? Each device so equipped would then be IP addressable. Full control of lighting and appliances from a PC on the same network; no extra cables to run. If your PC was connected via WiFi you could control everything while on the move.
Or perhaps you could replace a wall switch with an inwall PocketPC. Today's high-end home automation systems use both wireless and inwall touch-sensitive displays to control complete environments, including lighting, heating and cooling, entertainment and security. These systems also see service in the business world to control audio-visual systems in boardrooms, conference facilities and videoconference rooms. The one drawback to the inwall panels is that in most cases a separate proprietary control network is required, usually consisting of four wires (one power pair and one data pair). Even in the case where an inwall lamp dimmer is connected to one of these systems, that network is still required in addition to the power wires that the dimmer is controlling. Even though these companies are slowly moving towards Ethernet control, the power requirements of their touchpanels
are such that either the proprietary network or a local AC adapter is required to power the device.
And what of the devices that are being controlled? Well, they either need wires for a contact closure (such as is needed for a projection screen to be raised or lowered), wires for RS-232 control (such as a high-end video projector, video switching system, videoconference codec or audio system) or wires for an infrared emitter (to emulate the remote control for a VCR, DVD, CD or cassette deck). What if these devices were all Homeplug compatible? That would mean that in each case the control commands would be issued over the AC wiring as IP commands, and each device would receive the commands on it's power cord, and of course send responses back the same way.
So if the control functions are all handled via the power cords, all that is needed is the signal cables. But are they? HomeplugAV, the latest incarnation, has managed to achieve performance levels claimed to be greater than 100baseT. Current professional digital audio systems are capable of running 64 channels of digital audio over a single 100baseT connection - and that is to professional standards, i.e. 24bit at 48KHz (CD, by contrast, is 16bit at 44.1KHz). So the relatively modest requirements for business or home audio would be easy to handle: the source device (a DVD player, for example) would output it's multichannel audio signal over the ethernet on it's power cord, routed to a signal processor where volume, selection and equalisation would be performed (both input and output over that device's power cord) and the finished product would be finally picked up by powered
loudspeakers - once again over their power cords. You might want to check out Altec-Lansing's 'Commstar' system (not Homeplug, but getting there) to see the possibilities.
High-end video signals would still be a problem for this scenario. The bandwidth required for RGBHV (red, green, blue, horizontal and vertical sychronization) is still beyond 100baseT networks (I know they can be run over unshielded twisted-pair (UTP) directly, but that's cheating). But basic composite video, S-video and even component video are within the reach of current Ethernet speeds, and of HomelugAV. And with advances in compression algorithms, we may yet see full-motion computer monitor signals on 100-megabit ethernet before long.
So sooner than we think, we may see a house or office or boardroom full of ethernet-capable devices with only one plug - the AC power cord. And all of the information - data, control, sound and video - is being communicated over that one cord and one set of wires that has been there all along.
But only as long as it's plugged in.
Consumer Electronics Powerline Communication Alliance
