What is Bluetooth?
By John Anderson

There are lots of different ways that electronic devices can connect to one another. Your mouse, keyboard and printer are connected to your computer. Your personal digital assistant (PDA) can connect to the computer with a docking cradle. And of course, let’s not forget about the nest of wires connecting your TV, VCR, cable box and speakers.

The art of connecting things is becoming more and more complex every day. We sometimes feel as though we need a Ph.D. just to set up the electronics in our homes! Now there is a completely different way to connect electronic equipment together called Bluetooth. Bluetooth is wireless and automatic and has a number of interesting features that can simplify your daily life.

The Problems

When any two devices need to talk to each other, they have to agree on how they are going to communicate. All of the parties in an electronic discussion need to know whether the message they receive is the same message that was sent. In most cases, this means developing a language of commands and responses known as a protocol. Some types of products have a standard protocol used by virtually all companies so that the commands for one product will tend to have the same effect on another. Modems fall into this category. Other product types each speak their own languages, which means that commands intended for one specific product will seem like gibberish if received by another. Printers are like this, with multiple standards like PCL and PostScript.

In order to make home electronics more user-friendly, we need a better way for all the electronic parts of our modern life to talk to each other. That’s where Bluetooth comes in.

Bluetooth Basics

Bluetooth is a standard developed by a group of electronics manufacturers that allows any sort of electronic equipment – from computers and cell phones to keyboards and headphones – to make its own connections, without wires, cables or any direct action from a user. Bluetooth is intended to be a standard that works on two levels:

• It provides agreement at the physical level – Bluetooth is a radio-frequency standard.
• It also provides agreement on when bits are sent, how many will be sent at a time and how the parties in a conversation can be sure that the message received is the same as the message sent.

The more than 1,000 companies belonging to the Bluetooth Special Interest Group want to let Bluetooth’s radio communications take the place of wires for connecting peripherals, telephones and computers.

There are already a couple of ways to get around using wires. One is to carry information between components via beams of light in the infrared spectrum. Infrared is used in most television remote control systems, but it’s also used to connect some computers with peripheral devices.

Infrared is fairly reliable and doesn’t cost very much, but infrared is a “line of sight” technology that you have to point at a device to make things happen.

Cable synchronizing is a little more troublesome than infrared. If you have a Palm Pilot, a Windows CE device or a Pocket PC, you know about synchronizing data. In synchronizing, you attach the PDA to your computer (usually with a cable), press a button and make sure that the data on the PDA and the data on the computer match.

Bluetooth is intended to get around the problems that come with both infrared and cable synchronizing systems. The hardware vendors, which include Siemens, Intel, Toshiba, Motorola and Ericsson, have developed a specification for a very small radio module to be built into computer, telephone and entertainment equipment. From the user’s point of view, there are three important features to Bluetooth:

• It’s wireless. When you travel, you don’t have to worry about keeping track of a briefcase full of cables to attach all of your components, and you can design your office without wondering where all the wires will go.
• It’s inexpensive.
• You don’t have to think about it. Bluetooth doesn’t require you to do anything special to make it work. The devices find one another and strike up a conversation without any user input at all.

Bluetooth communicates on a frequency of 2.45 gigahertz, the same frequency as baby monitors, garage-door openers and the newest generation of cordless phones.

Avoiding Interference

With many different Bluetooth devices in a room, you might think they’d interfere with one another, but several devices operating on the same frequency at the same time is unlikely because Bluetooth uses a technique called spread-spectrum frequency hopping. The transmitters change frequencies 1,600 times every second, meaning that more devices can make full use of a limited slice of the radio spectrum. Since every Bluetooth transmitter uses spread-spectrum transmitting automatically, it’s unlikely that two transmitters will be on the same frequency at the same time.

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.

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

Why is It Called Bluetooth?

Harald Bluetooth was king of Denmark in the late 900s. He managed to unite Denmark and part of Norway into a single kingdom then introduced Christianity into Denmark. He left a large monument, the Jelling rune stone, in memory of his parents. He was killed in 986 during a battle with his son, Svend Forkbeard. Choosing this name for the standard indicates how important companies from the Baltic region (nations including Denmark, Sweden, Norway and Finland) are to the communications industry, even if it says little about the way the technology works.

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Publications : Bar Bulletin: April, 2003