Bluetooth LE Targets Smart, Low-Power Applications

Since the Bluetooth standard was first published, Bluetooth Special Interest Group (SIG) members and developer communities have been quietly filling consumers’ lives with short-range wirelessly connectable products such as mobile phones, headsets, and PC dongles. According to InStat Research, more than 2 billion Bluetooth-enabled devices will ship in 2013.

As the middle member of a “holy trinity” of industry standards for wireless communication, sitting between ZigBee low-data-rate wireless and multi-gigabit Wi-Fi (IEEE 802.11x), Bluetooth supports data rates up to 2.1 Mbits/s and offers low design risks for product developers, fast time-to-market, access to a large pool of developer skills, and certified interoperability with certified compliant devices from other manufacturers.

Interoperability enhances the marketability of Bluetooth devices. It also encourages development of new and innovative products and applications, provides flexibility for end users to mix and match products from various manufacturers, and ultimately serves the Bluetooth SIG’s vision of enabling seamless ad hoc connectivity.

Bluetooth has become a key factor driving almost universal consumer awareness of and demand for wireless connectivity between personal and mobile devices. If the initial “killer app” was the mobile phone headset, aided by widespread legislation to prevent drivers using handheld mobiles, the subsequent growth of phenomena such as social media, smart metering, personal wellness monitoring, and home automation present a diverse and growing range of further opportunities for Bluetooth as a ubiquitous, low-cost, ad hoc wireless networking technology.

The World Moves On

Emerging applications could benefit from Bluetooth’s ability to exchange or collect information from a variety of sources for control, sensing, and measurement purposes. However, the legacy Bluetooth 2.0 and 3.0 standards are not well suited to ultra-low-power applications such as tiny sensors that may need to operate from a button cell for several years without requiring replacement of the cell.

To encourage selection of Bluetooth as the standard of choice for these applications, the Bluetooth SIG adopted the Bluetooth 4.0 standard in 2010. An important aspect of the latest update is the addition of low-energy technology to the Bluetooth core specification. Bluetooth Low-Energy (LE) enhances the standard’s scope to take advantage of established Bluetooth performance benefits in low-power battery-operated sensing applications.

Bluetooth LE significantly reduces peak, average, and idle-mode power consumption by speeding up connection and disconnection processes and enabling a lower total energy budget for the application. Figure 1 compares the time to execute corresponding processes in standard Bluetooth BR/EDR protocols and Bluetooth LE, showing that Bluetooth LE can be more than 10 times faster from connection setup to data transfer.

Bluetooth LE Applications

With this LE technology, the Bluetooth SIG is expecting the first new product introductions to be focused on healthcare and fitness products. This vision encompasses devices such as heart-rate monitors, watches, foot pods, GPS locators, and pedometers that will enable athletes to collect more accurate performance data. These products, as well as medical devices such as stethoscopes, glucose meters, and pulse oximeters, will deliver advantages such as more flexible, untethered use.

Many of these devices will leverage Bluetooth connectivity in devices such as PCs and mobile phones to permit easy wireless syncing so data can be collected, processed, analysed, and shared easily and simply. The first Bluetooth 4.0-enabled medical and fitness products are expected to reach store shelves by late 2011.

Many other applications are being considered or evaluated, such as a promising Bluetooth-based traffic detection system trial in Houston. Using low-power Bluetooth-enabled sensors positioned at the roadside in busy districts of the city, the pilot scheme tracks anonymous media access controller (MAC) addresses of Bluetooth devices in passing vehicles as they progress through the city’s traffic. Traffic conditions then can be assessed accurately in real time without the huge expense of automatic vehicle recognition technologies, such as visual number plate recognition.

Bluetooth LE operation is a key enabler of the system, as it permits small, battery-powered nodes positioned at the roadside to collect the information needed to monitor traffic movements. This saves the expense of providing wired connections to each node, also reducing installation and infrastructure costs.

Overcoming Implementation Challenges

Product developers are already coming to grips with the new Bluetooth 4.0 wireless standard. As markets for these new devices become established, and as further new application opportunities emerge, they will need to be able to add Bluetooth 4.0 capabilities to new products without becoming involved in low-level implementation challenges such as analogue and RF design, integrating the various required protocols, and implementing the host-controller interface supporting connection to the main application processor.

Frequently, product development teams are focused at the application level and do not have in-house expertise to complete these tasks. To overcome these barriers the organisation may choose to acquire the needed expertise organically or hire a consultant. In either case, this can add to development costs and delay market introduction. In the Bluetooth space, there is a precedent for semiconductor vendors to offer a system-on-a-chip (SoC) solution that builds in solutions to most or all of these challenges.

As a founding member of the Bluetooth SIG, Toshiba Electronics has been involved in Bluetooth standardisation and implementation for more than a decade. The company has delivered a number of Bluetooth LSI solutions that support the version 2.1 and 3.0+ Enhanced Data Rate (EDR) standards.

These products include the TC35655 single-chip CMOS IC with embedded ARM9 application processor, which supports Bluetooth profiles such as hands-free and audio streaming and targets applications requiring basic-level Bluetooth functionality. For high-performance Bluetooth applications, a chipset comprising the TC31299 RF IC and TC35658 baseband chip adds CPU support by middleware for text-to-speech and voice recognition.

Toshiba’s TC35661 supports Bluetooth 4.0 as well as Bluetooth 3.0 EDR, enabling use in single-mode or dual-mode applications. It is fabricated using 65-nm RFCMOS technology, which delivers die-size advantages, and features internal voltage management contributing to low overall power consumption and a minimum of external passive components. A 30-µA sniff mode also helps to minimise overall energy budget.

The TC35661 RF block offers a sensitivity of –90 dBm. The device also provides a high level of integration, with features such as a low-dropout (LDO) regulator and all of the necessary RF functionality including a balun, antenna switch, and low-noise amplifier (LNA) implemented on-chip (Fig. 2). The device can be used with the standard Bluetooth HCI UART host-controller interface or with Toshiba’s integrated Bluetooth stack with a selection of application profiles, which enables a complete Bluetooth solution without support from an external host (Fig. 3).

To simplify the design efforts for OEMs and free them from complex interoperability tasks, Toshiba offers a Bluetooth certified protocol stack that can be combined with its various application profiles depending on the target application type. An open application programming interface (API) is available, and a flexible integration into various operating systems is achievable (Fig. 4).

Since its arrival in the wireless networking marketplace, Bluetooth has been enthusiastically adopted within a relatively small world of applications. With the arrival of the version 4.0 standard featuring LE technology and new SoC devices supporting this enhanced functionality, Bluetooth will open up a much wider universe of applications based on smart, low-power devices.

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