After years of what seemed like endless hype, Bluetooth wireless technology has become a mass-market consumer product technology, having shipped in more than 240 million units with price points of less than $3 per chip. It is the only wireless technology that enables interoperable wireless headsets for use with many different manufacturers’ mobile phones and is driving the adoption of wireless telephony in automobiles. These applications and others like synchronization of personal information and access to the Internet with a laptop anywhere a user has cellular coverage, have pushed adoption of Bluetooth technology.
Bluetooth has reached an inflection point where usefulness, robustness and costs have combined to make the technology compelling. It’s hard to find a smartphone launched during the past six months that does not come standard with Bluetooth, and the technology’s appeal has resulted in about 150 million units shipped in 2004.
Bluetooth is a cable replacement technology-one that is lower power than Wi-Fi and has comparable power to Zigbee when transferring the same amount of data. Bluetooth supports older industrial standards using protocols based on RS232, or in Bluetooth speak “serial port profile.” This allows replacement of delicate wires with robust wireless technology that frequency hops around interferers, adapts to the environment of static interferers like 802.11, has sufficient bandwidth for these protocols, and quickly retransmits corrupted packets.
Bluetooth, having come from the standards-based mobile-phone industry, is built on a large number of interoperable profiles. These are regularly tested-typically three times a year at Bluetooth Special Interest Group SIG-sponsored Unplugfests-and are qualified using a set of test cases with excellent interoperability.
Bluetooth has been improved by the addition of enhanced data rate, which extends the raw data rate up to 3 megabits per second. The addition of EDR will further decrease current consumption in designs by allowing shorter transmission times and therefore longer times of inactivity while consuming only A in Bluetooth designs.
Enhancements scheduled for 2005 will further decrease power consumption, allowing Bluetooth-enabled sensors to last for multiple years on one AA battery, and increase the size of a single piconet, from seven to 255. These are small changes to the existing specification, as most Bluetooth products can already get reasonably close to this performance.
The Bluetooth SIG is extending the specification to enhance current applications and expand into new areas. This includes features like sniff sub-rating, allowing asymmetric power consumption, fast data transactions in less than 50 ms, and extended addressing with unlimited addressing. Extended addressing will allow more than seven nodes, yet still permit low-latency data transmission.
Another new development coming to the Bluetooth specification is improved quality of service. This will allow bandwidth to be partitioned between devices so latency and data rates can be tuned to each device’s requirements. Predictable quality of service will improve performance of many applications. Gamers will be able to get the low-latency response times they need, sensors will be able to predictably deliver data, high-priority applications requiring a high bandwidth will not be starved out by lower priority applications. Feature-rich wireless standards such as 802.11 also are developing quality-of-service specifications that are anticipated on a similar timeline to the Bluetooth releases, though less-feature-rich specifications such as ZigBee have abandoned mechanisms to deliver data with predetermined timing. Given the relative price points of 802.11 and Bluetooth, this will leave Bluetooth as the only low-cost wireless technology capable of delivering data with a specified quality of service.
The battery life of any wireless device is related more to the duty cycle than the technology for transmitting the data. Bluetooth can use low duty-cycle modes of operation, connecting quickly, robustly transmitting the data required and disconnecting. Bluetooth is low power when sending data. Wireless headsets using Bluetooth have longer battery lives and talk times than the cell phones to which they are connected.
Although Bluetooth is able to talk to more devices, is robust and low power, as well as a fantastic technology for cell phones, wireless headsets, PCs, access points and hands-free driving in automobiles. But it is not a panacea for all wireless solutions; some technologies like ZigBee will be able to find a particular niche.
However, Bluetooth is already a 100-meter technology with built-in standard CMOS and multiple upper layer stacks, produced in millions of chips a month by multiple silicon vendors in a competitive market. Can ZigBee do all this, for less money? RCR
Eric Janson is CSR plc vice president of North America writing on behalf of the Bluetooth SIG. CSR is a Bluetooth solutions provider.
