Thanks to an emerging communications standard, low-power radios will soon connect laptops and other portable devices without
a rat's nest of cables.
In an increasingly
plugged-in society, plugging things in is an increasing headache. To pick up email, laptop users must search for jacks or hook up to a cell phone. Personal digital assistants (PDAs) have to be cabled to desktops to pick up and drop off data. But IBM, as part of a five-company consortium, is developing a way to overcome these constraints with a low-power wireless connectivity solution called Bluetooth.
Bluetooth uses very-short-distance radio to allow any electronic device to communicate with any other within 10 meters, even in the presence of dozens of other users. By eliminating hard connections, Bluetooth would erase the difference between mobile and stationary computing -- the device would be "plugged in" wherever it was. In a train, for example, Bluetooth would connect a laptop or PDA to the Internet via a cell phone in a briefcase (a concept called "hidden computing"), while at the office the link would be a data access point.
The Bluetooth consortium -- formed by IBM, Ericsson, Intel, Nokia and Toshiba in February 1998 -- is close to formulating an industry standard. Eventually, Bluetooth systems, perhaps mounted on a single chip, could find their way into virtually every electronic device.
Bluetooth can ease connection not only to the phone system or the Internet but also between devices. Indeed, says Mahmoud Naghshineh, manager of the pervasive networking and communication systems group at the Thomas J. Watson Research Center, "Bluetooth's focus on low-cost, high levels of integration and ease of configuration has the potential to change current mobile computing and network connectivity paradigms." Moreover, because Bluetooth supports both voice and data and a wide range of applications -- from file synchronization and business card exchange to Internet access -- it will strengthen IBM's mobile computing offerings. These include not only devices like ThinkPad® computers but also wireless connectivity solutions such as Wireless Domino™ Access and IBM Mobile Connect.
IBM Research, together with the IBM Personal Systems Group, SecureWay Business Unit and pervasive computing organization, are contributing to the specifications of Bluetooth technology. At the same time, Research is developing prototypes to address a variety of networking and connectivity problems and to demonstrate novel usage scenarios.
Since Bluetooth would be used in conference rooms, where many devices may be communicating at once, system designers had to come up with a way to avoid interference. This was a tall order, since Bluetooth has to function in an unlicensed part of the radio spectrum around 2.4 gigahertz, which is used by microwave ovens and other radio-noisy sources. The solution was to adapt "spread spectrum" technology developed by the military to counter jamming. Instead of staying on one frequency, each device will hop 1,600 times a second among 79 frequencies. The device initiating the connection will tell the other device what sequence of hops to use. "If there is too much interference at one frequency, the transmission is lost only for a millisecond," Naghshineh explains. To increase reliability, the system can send each data bit in triplicate. The result is that several dozen people in a room can use Bluetooth without significant interference.
CONTAINING COSTS
Another technical challenge was to keep the system inexpensive enough to become ubiquitous. So IBM's design team had to keep the communication protocol simple. At the same time, the protocol had to be highly reliable and to incorporate encryption techniques to make messages difficult to intercept. The protocol is almost ready to be adopted as an industry standard.
An equally important goal is to implement Bluetooth on a single chip, both to save cost and to avoid draining device batteries. "The challenge here was to eliminate as many 'off-chip' components as possible," says Modest Oprysko, senior manager of communication technology at Watson. "These are among the largest contributors to a radio's cost." Such trimming was possible because of Bluetooth's short range, which allows a receiver to be an order of magnitude less sensitive than a cordless phone. The transmission rate -- no more than 720,000 bits per second -- is also modest, less than a tenth that of wireless LANs.
To make this "cheap radio on a chip," Oprysko and colleagues are defining a radio architecture that will use IBM's high-performance silicon-germanium (SiGe) technology. SiGe allows radio-frequency (RF) and logic components to be combined on the same chip.
IBM ships millions of infrared (IR) transceivers that provide high-speed (4-megabit-per-second) short-range connectivity for devices and peripherals. With Bluetooth, IBM would be one of the few companies able to offer a comprehensive set of cordless solutions based on both IR and RF technologies. In a few years, such solutions could make the cable tangle obsolete.
Eric J. Lerner is a freelance writer who lives in Lawrenceville, New Jersey.
