Bluetooth Speeds Up

by George Lawton 

The Bluetooth Special Interest Group (SIG) has ratified the Bluetooth 3.0 specification, which promises faster speeds and better power management. Chip makers Atheros, Broadcom, and CSR have already started implementing the new silicon, and Bluetooth 3.0 products are expected toward the end of this year.

A key feature of the new specification is Bluetooth 3.0 + High Speed (HS), which increases the connection from 3 to 28 Mbytes per second using 802.11, noted Mike Foley, executive director of the Bluetooth SIG. This will improve its utility in applications with large data requirements such as transferring files, printing, and synching devices.

The new version comes as smart phones are becoming minicomputers. Cellular phone owners have used Bluetooth for wireless headsets and to synchronize calendar and contact information. Now that smart phones are handling music, movies, and data, users want more speed.

Backward Compatibility

Bluetooth 3.0 will be backward compatible with 2.0, which will continue to be a mainstay of the mobile-phone industry for headsets and other basic devices. Brian O'Rourke, an In-Stat analyst, said about one billion Bluetooth 2.0 devices shipped in 2008. He expects a few million Bluetooth 3.0 devices to ship in 2009, ramping up to a few hundred million in 2011. Foley said the Bluetooth SIG would consider the specification a success once it’s deployed in 20 percent of all new Bluetooth devices.

The HS mode will be added to Bluetooth radios but turned on only during large file transfers. The existing Bluetooth radio technology will still be used for signaling and low-data-rate activities for headsets, mice, and keyboards. 

Chip manufacturers can use existing Bluetooth and 802.11 chips for the new specification. They only need to adjust the software, said Ron Wong, senior product-line manager at Broadcom. The major Bluetooth chip producers are already making integrated chips that support both radios. Existing devices with Bluetooth and Wi-Fi hardware could be upgraded to Bluetooth 3.0 with an update to the software that sits between applications and the radio. Mobile-application developers will continue to use the same Bluetooth APIs, noted Wong.

When a high-speed channel is required, the Bluetooth 3.0 software will use 802.11, if that mode is available on both devices. If one of the devices doesn’t support HS, the data will be sent via the Bluetooth 2.0 Enhanced Data Rate (EDR) protocol.

Bluetooth 3.0 supports the same range choices as Bluetooth 2.0—that is, either 10 or 100 meters, depending on the radio and application requirements. 

Sharing Spectrum

Both the existing Bluetooth and the HS radios share the same 2.4-GHz spectrum, which Wi-Fi and many other unlicensed radio devices use. Although both Bluetooth 3.0 and Wi-Fi use the same radio, they are different protocols and don't interoperate at the application layer.

Kevin Hayes, an Atheros technical fellow, said there were many challenges with getting the different protocols to coexist with each other. Bluetooth and Wi-Fi connections are typically not aware of each other, which can increase interference, particularly when they're used on the same device.

To reduce this interference, the Bluetooth SIG created activity reports that make Bluetooth applications aware of Wi-Fi applications on the same device. In most applications, the 802.11 radio will turn on for 10–20 seconds to transfer a file and then turn off again, said Wong.

Hayes said testing Bluetooth 3.0 applications has been one of the biggest challenges. "It's hard because there is nothing to interoperate with," he explained. "We have our own equipment to test against, but customers want to know it works between devices from different manufacturers. This will change as it becomes more widely deployed."

Better Power Management

Bluetooth 3.0 adds support for Unicast Connectionless Data (UCD) and Enhanced Power Control (EPC), two features that promise to reduce the power required for many applications. UCD lets a device transfer a small amount of data without a traditional connection's overhead.

EPC makes it easier to turn off the Bluetooth connection when it’s not actively sending data. Foley said this can reduce power requirements significantly for applications such as a keyboard, which doesn’t need to send data when you pause typing. "It gets you into sleep mode quicker," he said. "When you're typing, it seems like you're connected all the time, but there are significant pauses. All those 20- to 30-second pauses add up."

The Bluetooth SIG is also working on the Bluetooth Low-Energy Mode (LEM) specification, which it expects to finalize by the end of the year. Ultra-low-power devices can use LEM to save energy by going into long-term standby mode. Foley said it would let devices such as watches, heart-rate sensors, and pedometers run for long periods without having to change the batteries.