Lower-power Bluetooth

Oct. 3, 2007
Low power consumption is a critical product differentiator for all types of battery-powered wireless devices.

For handheld computers or mobile phone handsets, power consumption limits the service period of the device, because it cannot be used effectively while it is recharging. Adding extra battery capacity adds volume, cost and weight to the device, all of which are undesirable. Manufacturers need an industrial handheld computer that can operate untethered for a complete work shift before needing an overnight recharge.

Most of the low-power industrial wireless devices now installed use proprietary radios. The only standardized radios now on the market offering extreme low-power performance are IEEE 802.15.4 radios, a standard promulgated by the Institute of Electrical and Electronics Engineers, which are used in some recent field transmitter products and in ZigBee-compliant products. Bluetooth radio technology, while very common in commercial markets, has been used in mains-powered industrial applications and in applications in which communication with handheld computers is important.

Suppliers such as ABB and Coronis have adapted Bluetooth radios for sensing applications, but have discarded the Bluetooth stack. Coronis’ Wavenis product adapts Bluetooth for low-power applications with very low data rates. ABB’s WISA wireless sensors require high data rates, so ABB designed a dedicated wireless power supply for them.

Wibree announced

In October 2006, mobile telephone handset manufacturer Nokia announced plans to commercialize a new low-power complement to Bluetooth. The company formed yet another cutely named wireless technology consortium (Wibree,) and began work. The plan was to develop two different device types. “Dual Mode” devices such as telephone handsets and mobile computers would be able to communicate to all types of Bluetooth devices. “Stand-alone” Wibree devices would communicate only with Dual Mode masters, and would be able to operate for long periods (roughly one year) on battery power.

Nokia’s announcement was received respectfully, if not with enthusiasm. The formation of another consortium and associated technology development was, for many, not appetizing. Yet Bluetooth is the most pervasive form of wireless, due to its penetration into the 1 billion mobile handsets manufactured each year. When combined with Nokia’s large share of the handset market, this made Wibree a factor in personal area network (PAN) market road maps.

While the technology development remained on schedule, the politics of the situation have now changed. The Wibree organization announced that it will merge with the far larger Bluetooth Special Interest Group (SIG). Its technology will become a designated ultra-low power (ULP), low-data-rate extension to Bluetooth, and will be incorporated into the existing Bluetooth specification. These specifications will be merged in early 2008, with silicon samples available late this year and in volume during 2008.

This addition means that Bluetooth will have three different physical layers by the end of 2008. The “Bluetooth Classic” (now IEEE 802.15.1), the new ULP, and the WiMedia Alliance ultra-wideband technology, which the Bluetooth SIG chose in 2006 to serve as its high-data-rate solution.

The new technology is not suited for most existing wireless sensing applications, and is certainly unsuited for industrial applications. The radios have a much smaller range than IEEE 802.15.4, and a star-type network is the only supported topology. Thus, a ULP PAN could be only 20 meters in diameter and include only seven devices, maximum. Existing industrial wireless sensing products (for example ABB, Accutech, Coronis, Emerson and Honeywell) all support far larger networks and longer ranges, even in only star-type networks.

Medical device manufacturers should evaluate Bluetooth ULP in comparison to other solutions for product designs created after 2007, but manufacturers should expect no impact from Bluetooth ULP on their wireless sensing plans for the foreseeable future. 

Harry Forbes, [email protected], is a Senior Analyst at ARC Advisory Group Inc., in Dedham, Mass.