The Bluetooth network uses an unlicensed radio frequency at 2.45 GHz. It is the same frequency used by WiFi networks, cordless phones, and microwave ovens. A Bluetooth device typically has a range of ten meters (32 feet), and a data rate close to 300kbps. Since the 2.45GHz radio wave can penetrate walls, you can connect Bluetooth devices across rooms.
Ad Hoc Network
Bluetooth networks are ad hoc networks. A Bluetooth device automatically detects devices within its range and forms networks with them. If a device goes out of range, the network automatically drops its membership.
The details of the Bluetooth network topology and discovery protocols are not important for most users. You just need to know that once a Bluetooth device joins a network, it can "see" all devices in the network. And Bluetooth networks can connect to each other via bridge devices. For instance, in a very large conference hall, the localized Bluetooth networks (devices within a ten-meter radius) can join each other and form a big network that covers the entire hall (much larger than ten meters). When a device at one of the end of the hall communicates with a device at the other end, the traffic might be relayed via several bridge devices. Any Bluetooth device can become the bridge, and the device owner does not need to know whether his/her device is a bridge--it is all done transparently at the network level.
Context Exchange Protocols
Most Bluetooth-enabled computers, PDAs, and smartphones support the basic serial communication profile. Potentially, Bluetooth applications on those devices can exchange arbitrary complex data via the serial port interface.
The Bluetooth specification defines not only low-level radio communication protocols, but also high-level content exchange protocols, known as profiles. Two Bluetooth devices supporting the same profile can exchange content with each other. For instance, a mobile phone and its wireless audio headset support the headset profile; Bluetooth digital cameras, including camera phones, and Bluetooth portable printers support the printing profile; PDAs, smartphones, and PCs support the synchronization profile for address book/calendar/to-do list/email synchronization; mobile phones supporting the dial-up network profile can be used as wireless modems for laptop computers; devices that exchanges file with each other, such as a smartphone, a PDA, a camera, and a PC, support the file transfer profile.
For your Bluetooth device, you can find its supported profiles, and how to set it up to work with other devices, in the owner's manual. You can also find out more information about Bluetooth profiles from this website.
As a network protocol uniting many different types of devices, Bluetooth is only useful when it enjoys wide industry support. In reality, Bluetooth is an industry standard supported by all major electronics and computer vendors. The industry-wide collaboration of Bluetooth is done through a forum called the Bluetooth Special Information Group (SIG). You can find Bluetooth specification documents and a list of Bluetooth devices on its website.
To use Bluetooth, you have to set up the devices and authenticate them with each other. The exact instructions, obviously, are different for each device, and you have to look them up in the device's manual. However, the same general principles apply. Below is a brief overview of the process.
Devices and Drivers
By default, Bluetooth is turned off on most handheld devices in order to reduce power consumption.
For most Bluetooth-compatible handheld devices, such as smartphones or PDAs, you do not need to install additional hardware or software to enable Bluetooth. You just need to navigate to the connectivity configuration menu on the device UI, and turn on the Bluetooth radio. Once Bluetooth is on, you can typically see a Bluetooth symbol or a small black dot on the idle screen. The device also has built-in Bluetooth utility software for changing the device name, changing the discovery mode, authenticating with other devices, sending files/messages, etc.
For computers, setting up Bluetooth is a little more complex. You first need to make sure that there is Bluetooth hardware installed on the computer. If not, you can easily purchase a USB-based Bluetooth dongle and just plug it in. If you do not want the dongle to stick out of your computer or have no spare USB port, you can purchase a Bluetooth card that can be installed inside of the computer. Different operating systems provide different levels of support for Bluetooth hardware.
Mac OS X: If you use a late-model Mac computer with the Mac OS X operating system, you can simply open System Preferences and click on the Bluetooth icon to turn on Bluetooth. The Mac OS X system has built-in Bluetooth utilities to perform common network tasks (e.g., searching for nearby devices, transferring files). It is recommended that you leave the Bluetooth icon in the system menu bar so that you can easily access the Bluetooth features with one click of the mouse.
Windows before XP with SP2 (Service Pack 2): If your Windows computer has an operating system older than Windows XP with SP2, you have to install the driver software that comes with your Bluetooth dongle or card. The driver software comes with common utilities to configure the Bluetooth properties of the PC and communicate with other devices on the Bluetooth network.
Windows XP with SP2 and later: A major new feature in Windows XP SP2 is the built-in Bluetooth support. When you plug in the Bluetooth dongle, Windows prompts you to install new hardware and select the appropriate driver already bundled in the operating system. After the hardware is successfully installed, you will see a Bluetooth icon in the system icon tray. Click on that icon to access Bluetooth network utilities.
Linux: To make Bluetooth work on a Linux box, you have to make sure that you have a recent Linux kernel (2.4.22 or the 2.6 series). Then, you can install the BlueZ Bluetooth support package. However, as a command-line tool, BlueZ is not particularly user-friendly. You have to issue multiple complex commands to complete simple tasks like authenticating a peer device or transferring files. If you use the GNOME or KDE desktop systems, you can download the GNOME Bluetooth Subsystem or KDE Bluetooth Framework packages to add an easy-to-use GUI for Bluetooth network utilities.
Since the Bluetooth drivers in the operating system must support Bluetooth profiles, those drivers come with native utilities for communication tasks defined in the profiles, such as device authentication, business card/file transfer, PIM synchronization, and so on. Nokia Smartphone Hacks covers details on how to set up Bluetooth on Mac, Windows, and Linux computers to connect to a smartphone.