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1 May 2002

Bluetooth standard passes muster

The Standards Board of the Institute of Electrical and Electronics Engineers Standards Association has approved IEEE 802.15.1, a standard that provides wireless personal area networks (WPANs) for notebook computers, personal digital assistants (PDAs), cell phones, and other portable, handheld devices.

Called “Wireless MAC and PHY Specifications for Wireless Personal Area Networks,” the standard is adapted from portions of the Bluetooth wireless specification.

The Institute for Electrical and Electronics Engineers (IEEE) licensed wireless technology from Bluetooth SIG, Inc., to adapt and copy a portion of the Bluetooth specification as base material for IEEE 802.15.1-2002. IEEE said the approved IEEE 802.15.1 standard is fully compatible with the Bluetooth Version 1.1 specification.

Bluetooth technology defines specifications for small form-factor, low-cost wireless radio communications among notebook computers, PDAs, cellular phones, and other portable, handheld devices, as well as connectivity to the Internet.

While Bluetooth’s profile is predominantly consumer oriented, its industrial base is solid. Products include wireless data acquisition and monitoring systems for laptop and desktop users.

COMPATIBILITY IS SURE

The technology has a future in challenging measurement and wireless sensing applications working in and with data acquisition, process automation, factory automation, and supervisory control and data acquisition systems.

Compatibility with LAN access points, PDA, handheld access, and piconets is sure.

“Under the agreement between the IEEE and Bluetooth SIG, the IEEE brought together a great many experts from around the world to scrutinize and enhance the Bluetooth specification. We received thousands of comments, and the Bluetooth SIG applied more than 300 of them to the original Bluetooth spec,” said Ian Gifford, IEEE 802.15 working group vice chair.

Tom Siep, general manager of Bluetooth SIG, said, “The peer review process the IEEE-SA brought to bear in standardizing the lower layers of our specification was an invaluable service; it created many changes and additions that improved the overall document. We appreciate our ongoing relationship with the IEEE-SA.”

Bluetooth transcends the problems that come with both infrared and cable synchronizing systems. From a user’s point of view, Bluetooth’s three most important features are that it is wireless, it’s inexpensive, and one doesn’t have to think about it.

Bluetooth doesn’t require anything special to make it work. The devices find one another and commence communications without any user input at all.

Bluetooth broadcasts on a frequency of 2.45 gigahertz. The band also hosts industrial, scientific, and medical devices.

Some nodes that use this same radio frequency include baby monitors, garage door openers, and cordless phones. Making sure Bluetooth and these other devices don’t interfere with one another has been a crucial part of the design process.

One way Bluetooth devices avoid interfering with other systems is by sending out very weak signals of 1 milliwatt. In comparison, the most powerful cell phones transmit a signal of 3 watts. The low power limits the range of a Bluetooth device, which lessens the chance of interference.

With many different Bluetooth devices operating in the same locale, one might think they’d interfere with one another. But it’s unlikely several devices would be on the same frequency at the same time because Bluetooth uses spread-spectrum frequency hopping.

CREATE PERSONAL AREA NETWORK

Bluetooth nodes use 79 individual, randomly chosen frequencies within a designated range, changing from one to another regularly. Transmitters change frequencies 1,600 times every second, meaning more devices can make full use of a limited slice of the radio spectrum.

Every Bluetooth transmitter automatically uses spread-spectrum transmission. Thus it’s unlikely two transmitters would be on the same frequency at the same time. Were there to be interference on a particular frequency, it would last only a fraction of a second. If that period of time presented a problem to the application, software exists that would correct such errors and let the network pursue its mission.

When Bluetooth-capable devices come within range of one another, an electronic conversation takes place to determine whether they have data to share or whether one needs to control the other. The user doesn’t have to press a button or give a command. The electronic conversation happens automatically. Once the conversation has occurred, the devices form a network.

Bluetooth systems create a personal area network, or piconet, that may fill a room or encompass no more distance than that between a cell phone on a belt clip and the headset on your head.

Once a piconet is established, the members randomly hop frequencies in unison so they stay in touch with one another and avoid other piconets that may be operating in the same room.

Visit the official Bluetooth Web site and read the specifications. IT

InTech senior technical editor Nicholas Sheble edits Fieldbus News.