Wireless networks: Confusion and promise

NASA Tech Briefs, Aug 1999 by Ross, Steve S

Special Coverage: Wireless Communications

There's a revolution brewing in wireless networks - a revolution that promises a wide variety of network options: different speeds, operating systems, ranges, and number of network nodes. The ultimate goal - wireless networking so ubiquitous and seamless that all you have to do to connect is to bring your laptop, palmtop, or data collection appliance into the room - is still elusive.

Some devices aim for interoperability by formatting data into Internet-compatible packets. Intel has its Wired for Management (WfM) initiative, a hardware standard that allows any Windows "management" software (Excel, Word, WordPerfect, etc.) to communicate with a WfM-enabled PC.

The next step is the much-discussed Bluetooth, which is expected to start delivering products by mid-2000. There are more than 800 companies in the Bluetooth SIG (Special Interest Group), which aims at delivering a royalty-free open wireless specification. The idea is to embed tiny short-range transceivers into just about any mobile device. The transceivers may cost $20 to start, but the price will soon fall to about $5. Data throughput is a so-so 721 kilobits per second, along with three voice channels (voice and data use the same equipment). The transceivers use the unlicensed 2.45-GHz radio band and require 1/10 watt to transmit (at 8 to 30 milliamps). Standby power consumption should be as little as 1/1000 of that. This should make it possible to add Bluetooth to cameras, palm computers, pocket phones and other basic equipment (www.bluetooth.com).

Proxim's "Symphony" devices using that band (PCMCIA card, network base stations, and so forth) already are on the market. Typical throughput is 1.6 megabits per second with ranges up to 150 feet.

For shorter ranges and higher data throughput, there's infrared. Microsoft has pretty much run the standard there; its IrDA 1.2 driver kit is used by most vendors. Even so, you will find two versions of infrared transmission technology. There's Fast IR, which is on most of the newer laptops and on many printers. It transmits at up to 4 megabits per second. The older standard, serial IR, at 115 kilobits/second, is still in use as well. The range is about two feet, and the IrDA transceivers have to be lined up carefully. IrDA, the Infrared Data Association, does consist of many companies aside from Microsoft.

IrDA's next standard is Advanced Infrared, or AIr. It promises infrared connectivity up to 15 feet. The AIr ports can be offset by up to 120 degrees, far more than the 30 degrees allowed by the older standard. That's good, because you don't have to be as fussy about aligning the IrDA ports. It could be bad, because many transmitters can be "sensed" by one receiver, but software logic reduces or eliminates the potential for interference. The data transmission speed, for Fast IR, is 4 megabits per second. IBM is already selling AIr modules -- transceiver, single-chip controller, controller macro, and software (www.chips.ibm.com/products/infrared). The software is as impressive as the hardware. With an AIr-equipped laptop, users can download a file to a palmtop via infrared while also responding to hardwire network requests.

What's Next in Wireless

This year's PC Expo in New York also underlined the work of hardware and software developers who intend to use these new wireless technologies for data collection, internet connections, and other functions that once required hardwire installations.

Novatel Wireless of San Diego has a wide range of products based on CDPD -- Cellular Digital Packet Data - also known as Wireless IP. CDPD uses the existing cellular phone network (strictly speaking, it is a network overlay that coexists with regular "AMPS" cellular) to transmit small packets of data. If you lose the connection during a session, a CDPD "modem" automatically reconnects. Each one comes with its own IP address; service is available in most metropolitan areas. The "modem" is really a network interface connector.

Sierra Wireless introduced its CDPD AirCard 300 for Windows CE, 95, 98, and NT at PC Expo. It, too, is really a network interface card, not a modem. When used in a notebook computer, it automatically connects to the cellular network when the notebook is turned on. Sierra Wireless also has encryption software for its wireless devices (www.sierrawireless.com).

Qualcomm uses CDMA (Code Division Multiple Access, for PCS cellular) for a range of wireless "phones" for home and office.Just plug them into a power outlet - no phone needed (www.qualcomm.com/cdma).

Novatel has wireless modems on Type II PCMCIA cards (its Merlin line), and for Palm and Windows CE machines (the Minstrel line). The Minstrel E-15 wireless IP Modem is strictly for the Casio E-15 Palm PC. Its lightweight "Expedite" modem module can be embedded into OEM equipment. A larger version, the NRM-6812 line, can operate under a wider range of temperatures and voltages. Typically, devices using the Wireless IP network can expect throughput around 19.6 kilobits per second - adequate for most e-mail and data collection needs (www. novatelwireless.com).