In case you're still weighing the alternatives, take a look at these wireless technologies competing with Bluetooth in the personal area network (PAN) space:
Induction Wireless: This technique uses magnetic induction rather than radio for close-range communications. In radio, both electric and magnetic fields make up the signal, while in induction wireless, only the magnetic field is transmitted. The transmitter is a radiating coil that's more like the primary winding of a transformer than an antenna.
Invented and patented by Aura Communications (www.auracomm.com), this system has about a 3-m range. A typical unit transmits up to 204.8-kbit/s data rates via GMSK modulation on 11.5 MHz. Its key benefits are extremely low power consumption, low cost, and the inherent security that accompanies short range.
Infrared Wireless: This was probably the first PAN technology for use over short distances. The IrDA infrared (IR) standard appeared during the early 1990s, thanks to Hewlett-Packard, and it is still supported by Agilent Technologies (www.agilent.com). IrDA initially offered a 115.2-kbit/s data rate over a range of up to 1 m. A 4-Mbit/s version was soon developed and has been widely incorporated in laptops and PDAs for printer connections and short-range PANs. A 16-Mbit/s version is available too.
The problem with IrDA isn't just its very short range, but also its need for a line-of-sight (LOS) connection. Of course, Bluetooth doesn't need LOS, and it can blast through walls. A more recent IR development is IrGate, which was produced by Infra-Com Technologies (www.infra-com.com). It uses arrays of high-powered IR LEDs to emit coded baseband IR in all directions. Then it relies on an array of photodetectors and super-sensitive receivers to pick up the diffused IR within the networking space. Thus, the LOS problem is mitigated, and a data rate of up to 10 Mbits/s is possible.
Ultra Wideband: UWB transmits data by way of baseband pulses applied directly to the antenna. The narrow pulses (less than 1 ns) create an extremely broad bandwidth signal. The pulses are modulated by pulse position modulation (PPM) or binary phase-shift keying (BPSK). The FCC permits UWB in the 3.1- to 10.6-GHz band. Its primary application to date has been short-range, high-resolution radar and imaging systems that penetrate walls, the ground, and the body. In addition, this new technology is useful for short-range LANs or PANs that require very high data rates (over 100 Mbits/s). UWB is still new in the commercial and consumer world, but it's well known in military and government applications. New UWB products are expected soon.
ZigBee: A simpler, slower, lower-power, lower-cost cousin of Bluetooth, ZigBee (www.zigbee.org) was created by Philips. It's supported by a mix of companies that are targeting the consumer and industrial markets. It may be a better fit with games, consumer electronic equipment, and home-automation applications than Bluetooth. Short-range industrial telemetry and remote control are other target applications.
Previously called RF-Lite, ZigBee is like Bluetooth because it uses the 2.4-GHz band with frequency-hopping spread-spectrum with 25 hops spaced every 4 MHz. The basic data rate is 250 kbits/s, but a slower 28-kbit rate is useful for extended range and greater reliability. With a 20-dBm power level, ZigBee can achieve a range of up to 134 meters at 28 kbits/s. It additionally lets you network up to 254 nodes. While no chips are yet available, ZigBee bears watching.
