The term wireless is generally used to refer to the wireless Ethernet standards, also known as Wi-Fi (or 802.11), but this is in fact just one of the wireless technologies available to devices around the home.
The 2.4GHz spectrum is a non-regulated range of radio frequencies used internationally for domestic devices such as cordless phones and baby monitors, as well as cordless mice, keyboards and joysticks. Generally, these devices are not capable of interacting with each other -- in fact, they have a tendency to produce nasty interference.
The group of standards known collectively as 802.11, Wi-Fi, or more broadly as "wireless", offer Ethernet connectivity to computers equipped with wireless network cards or WNICs. Generally, wireless is used to connect notebooks to existing wired networks via access points or specialised routers, although ad-hoc networks can be formed between multiple computers with WNICs. Most wireless Ethernet occupies the same 2.4GHz spectrum as cordless devices (excluding 802.11a) and can be used by compatible devices for digital home networking. The bandwidth of wireless networks ranges from 11Mbps (802.11b) to 54Mbps (802.11a and 802.11g). Although this is slower than the 100Mbps available to most wired networks, it is fast enough for Web browsing and streaming multimedia content. Some proprietary standards have also emerged that can double these speeds to up to 108Mbps.
Ultrawideband (UWB) is a wireless technology that provides a maximum throughput of 1 gigabit per second. Like 802.11, UWB uses radio frequencies but in a much wider spectrum than the 2.4GHz range used by conventional wireless and cordless devices. As these frequencies are restricted by most international authorities, the future of UWB is uncertain. If the fears of UWB interfering with existing systems are overcome, then it may emerge as the wireless technology of the future.
HomeRF is a wireless networking standard developed by a working group of vendors in 1998. Version 2.0 is capable of speeds up to 20Mbps. As it offers similar capabilities within the same frequency range as 802.11b, HomeRF was once considered a competitor to Wi-Fi. With the emergence of Wi-Fi speeds of 56Mbps and greater, however, HomeRF is largely a redundant technology.
Bluetooth is another radio frequency technology used by compatible computers, mobile phones and other handheld appliances for data transfer. Although capable of 723kbps over a range of up to 10m, Bluetooth is intended to be a short range and low speed standard to connect devices. While not suitable as the centrepiece of a digital home, Bluetooth does provide the option of using a PDA or mobile phone to interact with computer-controlled devices over a wireless or wired Ethernet network.
IrDA is an infra-red technology for transferring data between devices such as laptops, PDAs and digital cameras. It is very short range but offers speeds up to 1.152 Mbps (in version 1.1). Like Bluetooth, it is not particularly useful as a basis for networking, but does offer remote control possibilities to networked devices.
The least hi-tech contender is arguably the most convenient means of beaming digital media around the home. Pocket-sized FM transmitters available for less than $50 can plug into portable digital media players or PC sound cards, allowing any FM radio receiver to be tuned to play MP3 files. This is also an excellent alternative to in-dash car MP3 players or CD tuners. Additionally, FM video transmitters, available for around $100, let you use your TV to watch AVI and Quicktime movies playing on your PC. Although no match for the new wave of wireless digital media players, it is to home cinema what X10 is to home lighting!
Z-Wave is a proprietary wireless technology that is like a radio frequency version of X10. Using inexpensive RF enabled devices attached to appliances around the home, Z-Wave can be used to automate lighting, thermostats, alarms and other mains power operated appliances. The latest version includes support for UPnP and .NET extensibility, making it a candidate for an integrated digital home system.
HomePlug, HomePNA, CEBus and Neverwire
Inspired by X10, but aiming for better networking capabilities, a range of new protocols have emerged in recent years that utilise conventional electrical wiring for PC networks. HomePNA and HomePlug (also known as Powerline) are two competing standards that provide Ethernet connectivity using existing power circuits, adapters for which are available from major vendors. Another variation on this theme is the CEBus Home Plug'n'Play standard, which lacks the vendor support of the competing technologies. The Phonex Neverwire devices employ the same concept, but provide integrated broadband sharing capabilities for networking PCs over power cables.
Although a proprietary technology in its early stages, Readywire, from the makers of Neverwire, looks set to bridge the integration abyss between the limited realities of X10 and the unrealised possibilities of UPnP. Similar to X10, Readywire is capable of delivering home automation controls to up to 250 devices in 15 domains. Additionally, the USB adapter is equipped with an ARM 946 processor and up to 8MB of RAM. This delivers 168bit encryption to safeguard your appliances from hijacking. It can also drive 15 near-CD quality audio streams and seven full-duplex voice lines around your home -- all using standard power lines. Add to that, shared phone line and V90 modem functionality via any power outlet, and Readywire could become the easiest way to integrate home automation, networking and audio distribution in one easy package.