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Taking advantage of Bluetooth LE advertising mode

Posted: 22 Apr 2013 ?? ?Print Version ?Bookmark and Share

Keywords:Bluetooth 4.0? BLE? protocol stack? wireless sensor networks?

Unique modes of operation defined in the Bluetooth 4.0 specification enable a Bluetooth Low Energy (BLE) device to be a TX-only device with minimal required software support. It enables ultra-low-cost devices with limited resources to have BLE advertising functionality and broadcast their status information. This article describes BLE architecture and the protocol stack in general and focuses on Advertising mode and required software implementation.

What is Bluetooth LE
A few years ago, in 2010, Bluetooth Special Interest Group (SIG), a regulatory body for the Bluetooth standard, adopted the long-expected Bluetooth 4.0 specification. The cornerstone of this release is the Bluetooth Low Energy (BLE) specification, with functionality that opens doors for Bluetooth in the area of low-power, low-cost sensors and provides good leverage to compete with 802.15.4, Zigbee, Ant, Z-Wave, and other proprietary formats typically presented in that field.

Undoubtedly, Bluetooth is a dominant player in personal area networks (PAN) when applications require bulk data transfer, cable replacement, audio streaming, etc. Proliferated over the last 10 years in most cellular phones and PCs, Bluetooth has over a 2B installed base.

Bluetooth evolution over the years demonstrated improvement in data transfer rates from the original 1 Mb/s to 3 Mb/s as an Enhanced Data Rate (EDR) feature in release 2.0+EDR to 54Mb/s as Alternate MAC/PHY (AMP) in release 3.0+HS.

While pursuing applications that required a high data-transfer rate, Bluetooth was offering standard cable replacement functionality for applications that required a small, unfrequented exchange of information but were proven to be less optimal for this type of application.

At the same time, ZigBee, Ant, Z-Wave, and other proprietary wireless solutions based on 802.15.4 optimised for low-power wireless sensor networks (WSN) were offered to the industry. They carved a good slice of the pie in the field of industrial and home automation, HVAC and building monitoring. In the area of consumer electrics, ANT protocol proliferated in a number of products related to body area networks (BAN), but still could not make it into mass produced cell phones.

In the Bluetooth 4.0 release, Bluetooth closed the gap by offering a new evolution of protocol highly optimised for battery operated, low-power, low-cost/disposable sensors that could seamlessly operate with the vast majority of cell phones.

It may take awhile to fully update the existing pool of cell phones with models supporting BLE, but it's just a matter of time: the latest Bluetooth technology is already proliferated into products from major players in the cellular industry like Apple and Google with Samsung and Blackberry following suit. Apple products have stable BLE support while Android platforms are still struggling to provide good API to hardware functionality. The beauty of BLE is in its ability to support an asymmetrical hardware implementation: a complex multi-functional device like a cell phone will support the full spectrum of the Bluetooth 4.0 specification, while sensor nodes may be implemented as an inexpensive resource limited design, supporting just a subset of the 4.0 specification but sufficient for the purpose of that device/sensor.

The focus of this article is on the advertising broadcast BLE functionality that could be used in low-cost or disposable devices with extremely low power consumption.

BLE stack
The BLE software stack has been described in great details in a number of publications, e.g., [2], [3] and it is touched upon in this article only in generic terms to compare with the SW requirements for implementation in reduced or limited functionality devices, e.g., using advertising only or scanner only modes.

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