Despite a tough economic environment, Bluetooth wireless technology is expecting to do well in 2010. According to US-based analysts IC Insights, Bluetooth chip revenues could hit US$3.2 billion next year. If the forecast is realised it will mean that annual production of the low power, short range RF technology would have more than doubled compared to 2006's US$1.47 billion of shipments.
Despite this impressive success, Bluetooth misses one key market that is currently dominated by proprietary technologies: ultra low power (ULP) wireless connectivity. Though not formally defined, ULP RF is invariably regarded as wireless connectivity powered by coin cell batteries, such as a standard sized CR2032 with 3V output. These devices can withstand a peak current of 22mA, but for practical applications with reasonable battery life, an RF transceiver should draw a peak current of less than 15mA, have very short transmit times (in the microsecond range), and feature a very low power consumption sleep mode (in the nanoamp range). The combination of these operating parameters leads to an average operating current in the microamp range and coin cell battery life of many months or even years in typical applications.
Bluetooth technology is unable to run on coin cells because it wasn't designed for ULP operation. For example, Bluetooth's power consumption rises to around 35 to 45mA when using the full transmission capability between a single master and slave for a contemporary Bluetooth Version 2.0 Enhanced Data Rate (EDR) device. This drops back to 5 to 10mA when simply maintaining synchronisation and down to microamp levels when in a sleep mode.
With lack of interoperability between products from different vendors a major downside of proprietary ULP wireless connectivity, Nokia decided to develop an interoperable ULP wireless technology in 2001. Later, to encourage wide adoption, the Finnish company decided to form an open industry initiative. Consequently, in October 2006, a group of like-minded companies, including Nordic Semiconductor, formed the Wibree Alliance, in order to coordinate the development of a specification and then hardware.
Meanwhile, the Bluetooth Special Interest Group (SIG) – a not-for-profit trade association comprising 13,000 member companies including such industry heavyweights as Ericsson, Intel, Lenovo, Microsoft, Motorola, Nokia and Toshiba – faced pressure from its members for an alternative to so-called 'Classic Bluetooth' technology that was able to run on coin cells. The SIG's members were keen to extend wireless connectivity to everything from biomedical monitors, watches, toys, sports goods and thousands of other consumer products, removing inconvenient wires and connectors, and opening up entire new product categories.
Sharing a common interest, the two groups merged in June 2007. Since then Bluetooth SIG members have been working on the specification for Bluetooth low energy technology, a ULP variant of Classic Bluetooth. Version 1.0 of the standard is nearing release and is expected to be available in early 2010.
So much for the history, what designers are now interested in is what the Bluetooth low energy wireless technology specification will look like, what problems the technology will solve and when it will be available.
Proprietary ULP fills the niche
Before Bluetooth low energy was a gleam in a researcher's eye, design engineers seeking to add wireless connectivity to their products faced a bewildering choice of options. Just taking into account the technologies based on open standards, there were WiMAX (based on IEEE802.16d and e), Wi-Fi (IEEE802.11b, g and n), Classic Bluetooth technology (formerly based on IEEE802.11.15.1) and ZigBee (IEEE802.15.4). At first glance, these technologies appear to cover the entire wireless communications spectrum from long-range, high-bandwidth to short-range, low-power consumption (suitable for battery-powered portable devices). However, none of these are suitable for wireless connectivity between small personal portable products with extremely limited battery power, such as a sportswatch communicating with a heart rate belt.
The lack of such an open standard has left a lucrative niche for proprietary solutions to fill. For example, Nordic Semiconductor's nRF24xxx family of 2.4GHz transceivers has been used in millions of wireless mice, keyboards, health sensors and sportswatches. The nRF24LE1 transceiver (which consumes around 13.5mA when transmitting or receiving at 0dBm and 2Mbps) runs the company's Gazell protocol and provides a wireless mouse with a battery life of a year on two AA batteries (under normal usage) compared to a month for an equivalent Classic Bluetooth-equipped mouse.
While the lack of interoperability is not a concern for manufacturers making both ends of a peer-to-peer link (who seek to benefit from a proprietary solution's superior price/performance ratio) it does prevent use by manufacturers intending to wirelessly connect to other company's products, or those looking for a second source of transceivers. These latter groups are the target customers for Bluetooth low energy.
