Windows XP SP1 will be Microsoft's first PC operating system to support the Bluetooth wireless networking protocol. Designed for low cost and minimal power requirements, Bluetooth can help consumers and mobile workers reduce the number of cables snaking through their work areas, and can help mobile devices, such as wireless phones and laptops, work better together. However, while Microsoft supports Bluetooth for simplifying physical connections, it favors other protocols for more complex networking tasks, such as data synchronization.

Windows Support for Three Device Types

Bluetooth is a suite of wireless networking protocols that enable devices to exchange data over distances of up to 30 feet at rates of up to 723Kbps. Ericsson and Bluetooth's other leading backers view it as an enabler for "spontaneous networking," in which devices such as wireless phones, headsets, printers, PCs, and handhelds all exchange data without any prior setup by the user. The goal of these proponents is to make devices more useful by combining device capabilities in new ways: enabling a user to wirelessly connect a laptop to a dial-up Internet account over a mobile phone, for instance.

To enable such synergies, Bluetooth defines a set of base protocols for discovery of devices and data exchange, and over 20 optional "profiles" for specific tasks, such as synchronizing data between a handheld device to a PC; transferring files; printing, sending, and receiving faxes; dialing a phone; and much more. The large number of optional profiles, however, makes interoperability complex—in order for two Bluetooth devices to work together, both must support the profiles required for a given task. A Bluetooth mobile phone, for example, would be able to synchronize phone numbers with a Bluetooth PDA only if both devices supported the Bluetooth data synchronization profile.

Microsoft has recently released an update to Windows XP Service Pack 1 (SP1) that supports the base Bluetooth protocols and some optional profiles. However, unlike the "spontaneous networking" proponents, Microsoft primarily views Bluetooth as a cable replacement technology. As a consequence, the current update to SP1 only supports three main types of Bluetooth devices:

Printers (available from vendors such as Hewlett-Packard) that support the Bluetooth Hardcopy Cable Replacement Profile

Phones (such as Ericsson's T68) that support the Bluetooth Dial-Up Networking Profile as modems, something particularly useful with laptops

Input devices, such as keyboards and mice, that support the Bluetooth Human Interface Device Profile. Microsoft's hardware division has recently released a mouse and keyboard product line called the Wireless Desktop that supports this profile. These products also include a USB Bluetooth transceiver for the PC; eventually, PCs might include such transceivers on their motherboards.

Personal Area Networks Coming

Beyond cable replacement, Microsoft believes that Bluetooth could be an attractive solution for wireless connectivity to LANs and the Internet. Consequently, the company is working on Windows support for the Bluetooth Personal Area Network profile (PAN). PAN enables devices to communicate over Bluetooth with the standard Internet Protocol (IP) and to dynamically obtain configuration information such as Internet addresses, thereby allowing existing network-aware applications to work with Bluetooth devices.

Support for PAN reduces the need for Microsoft to support additional Bluetooth profiles. Instead, Bluetooth devices can use standard Internet protocols or proprietary Microsoft protocols on top of PAN. For example, Microsoft does not plan to support the Bluetooth data synchronization profile on Windows; instead, devices that need to synchronize data with PCs, such as Pocket PCs and Windows Smartphones, will use Microsoft’s own ActiveSync protocol over a PAN.

Microsoft's PAN-centric strategy reduces costs for PC software and hardware vendors, including Microsoft itself. Vendors can modify software that already does a task (such as file transfer or data synchronization) using Internet protocols to do the same task over PAN; this is simpler than rewriting the software to support a Bluetooth-specific protocol for the task. However, Microsoft’s strategy complicates "spontaneous networking." Handheld device users, for example, will have to install data synchronization software for their devices on their PCs (because Windows will not support Bluetooth's synchronization profile by default), even if the handheld device supports PAN.

Windows CE .NET, Microsoft's operating system for embedded systems and mobile devices, supports Bluetooth more completely than Windows does. For example, it supports Bluetooth Object Exchange (OBEX), a profile required for Bluetooth data synchronization and file transfer that won't be supported on Windows. More complete Bluetooth support enables hardware vendors to use Windows CE .NET in a wider range of devices, including devices that aren't powerful enough to support PAN and IP. However, Microsoft itself does not intend to use all of Windows CE .NET's Bluetooth capabilities in its own software platforms for mobile devices. For example, future Pocket PCs and Windows Smartphones built on Windows CE .NET will use ActiveSync and PAN for data synchronization, rather than Bluetooth's data synchronization and OBEX profiles.

A Wireless Hedge

The PAN strategy makes Bluetooth just another protocol for Internet traffic. Therefore, it's not clear why vendors or customers would choose Bluetooth and PAN over wireless LAN protocols, such as the 802.11 family. The 802.11 protocols support longer ranges and higher data rates than Bluetooth (up to 11Mbps, with 54Mbps versions on the drawing board) and are more widely used today. Bluetooth does offer some advantages over 802.11, including much lower power requirements and potentially much cheaper hardware, which make it ideal for low-priced devices such as headsets. However, for devices powerful enough to run Internet protocols, volume production of 802.11 chip sets and the steadily decreasing cost of processing power could quickly close any cost gap between 802.11 and Bluetooth.

For its part, Microsoft appears to be hedging its bets: supporting Bluetooth alongside 802.11 in Windows, while minimizing the amount of Bluetooth-specific code it has to write. The company's software and hardware partners should consider following its example.

Requirements, Availability, Resources

The Microsoft Wireless Desktop keyboard, mouse, and transceiver package has an estimated retail price of US$159; the mouse and transceiver cost US$84.95 without the keyboard. Both ship with Windows XP SP1 and the Bluetooth update; the Bluetooth update is not available for separate download.

Microsoft's site for vendors supporting Bluetooth in Windows is www.microsoft.com/hwdev.

Developer documentation for Bluetooth support in Windows CE .NET is at msdn.microsoft.com/library/en-us/wcebluet/htm/cmconBluetooth.asp.

General Bluetooth information is at www.bluetooth.com.

An index to the Bluetooth specifications is at www.bluetooth.org/specifications.htm.