Home networking links with wireless

Home networking links with wirelessWith the development of a standard for the interconnection of domestic appliances using radio links, home networking can’t be that far away. Richard Ball reports
The networked house looms large as a consortium of heavyweight companies has developed a standard for the interconnection of domestic appliances using radio links.
The group includes Compaq, Ericsson, HP, Intel, Microsoft and Motorola and the standard covers more than obvious electronic devices like PCs, stereo systems, VCRs and Internet appliances.
Home networking will go further, linking other equipment in the home including the phone and even lighting and heating systems.
As the telephone rings then the volume of a stereo or TV can be automatically reduced. Or heating could be switched on remotely by phoning home and keying in a code.
Wireless technology has been chosen to reduce the mass of cabling that has already begun to build up around the home.
“There’s more computing power and equipment in the home now, and a lot of cabling comes with it,” said Symbionics’ Henk Koopmans.
The UK’s Symbionics, recently acquired by Cadence, has played an important role in developing this wireless home network standard.
“This needed industry to get together, primarily from the computer side, but they also needed people with wireless expertise,” Koopmans pointed out. “We helped to develop the protocol.”
Called the shared wireless access protocol (SWAP), the specification is based on a combination of IEEE802.11, or wireless LAN, and DECT. Both were originally developed with the help of Symbionics.
“The fact that we were very active in both technologies allowed us access to the group,” said Koopmans.
Wireless LAN provides the data service, while on top of this DECT allows real time data such as video and audio to be transferred.
Like wireless LAN, the service utilises the 2.4GHz band and uses frequency hopping spread spectrum radio. The transmitters will have a maximum power of 100mW, sufficient for home and garden use.
Normal packet data transfers use the carrier sense multiple access with collision avoidance protocol of LAN. Data rate is either 1 or 2Mbit/s.
For time deterministic data, such as a phone call to a mobile handset or stereo output, the system runs a DECT type service on top of the LAN service. This uses time division multiple access (TDMA) techniques.
For cheap systems, hardware can be designed that does not cope with the TDMA data. In this ad hoc type of system, all nodes are considered equal and control is distributed between the nodes.
For users wishing to add audio or other services that need the DECT-like TDMA service, a Connection Point is used to co-ordinate the system. This would be connected to a PC via universal serial bus and would act as the gateway to the telephone network.

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