Bluetooth Low Energy

Bluetooth low energy (BLE) is a feature of Bluetooth 4.0 wireless radio technology, aimed at new, principally low-power and low-latency, applications for wireless devices within a short range (Up to 50 meters / 160ft -see table below). This facilitates a wide range of applications and smaller form factor devices in the healthcare, fitness, security and home entertainment industries.

Lower power consumption

Devices using Bluetooth low energy wireless technology are expected to consume a fraction of the power of classic Bluetooth enabled products. In many cases, products will be able to operate more than a year on a button cell battery without recharging. It will be possible to have sensors such as thermometers operating continuously, communicating with other devices like a mobile phone. This may increase the concerns for privacy, as when the remote, low power, continuously on, sensor would be presence sensors or similar devices.

CSR, Nordic Semiconductor and Texas Instruments have released Bluetooth low energy chips. Other semiconductor companies are expected to release Bluetooth low energy chips in 2011.

During transmission and reception these devices exhibit peak currents in the tens of milliamps (mA) range. In sleep modes, current consumption is reduced to tens of nanoamps (nA). Because of very low duty cycles (of the order of 0.25%) average currents are therefore in the microamp (μA) range enabling button cell battery power sources to last up to a year.

Bluetooth vs NFC

	Bluetooth V2.1	BLE	NFC
RFID mode	active	active	ISO 18000-3
Standardisation body	Bluetooth SIG	Bluetooth SIG	ISO/IEC
Network Standard	IEEE 802.15.1	IEEE 802.15.1	ISO 13157 etc.
Network Type	WPAN	WPAN	Point-to-point
Cryptography	available	available	not with RFID
Range	~30 m (class 2)	~50 m	< 0.2 m
Frequency	2.4-2.5 GHz	2.4-2.5 GHz	13.56 MHz
Bit rate	2.1 Mbit/s	~200 kbit/s	424 kbit/s
Set-up time	< 6 s	< 3 ms	< 0.1 s
Power consumption	varies with class	< 15 mA (xmit)	> 15mA (read)

Bluetooth (2.45 GHz) and Near Field Communication (NFC 13.56 MHz) may both be used as short-range communication technologies. However, allowed transmission power for NFC 13.56 MHz is strongly limited implying short range, whilst Bluetooth has a range exceeding 10 m. Integration with mobile phones is increasing, where Bluetooth is already part of almost all phone types. BLE set-up time has been designed to be faster than traditional BlueTooth.

There is no aim to make Bluetooth's WPAN implementation compatible with passive RFID. However Bluetooth defines a well standardized new class of active RFID which requires comparably lower power consumption than NFC in passive read mode, due to different physical coupling: far field is used for Bluetooth, whilst near field/inductive is used for NFC.

History

former Wibree logo, abandoned for Bluetooth

In 2001, Nokia researchers determined that there were various scenarios that contemporary wireless technologies did not address. To address the problem, the Nokia Research Center started the development of a wireless technology adapted from the Bluetooth standard which would provide lower power usage and price while minimizing difference between Bluetooth and the new technology. The results were published in 2004 using the name Bluetooth Low End Extension.^[2] After further development with partners, e.g., within EU FP6 project MIMOSA, the technology was released to public in October 2006 with brand name Wibree.^[3] After negotiations with Bluetooth SIG members, in June 2007, an agreement was reached to include Wibree in future Bluetooth specification as a Bluetooth ultra-low-power technology, now known as Bluetooth low energy technology.^[4]

In December 2009, the Bluetooth SIG announced the adoption of Bluetooth low energy wireless technology as the hallmark feature of the Bluetooth Core Specification Version 4.0. Samples of sensors utilizing this specification are available from some silicon manufacturers today and shipments are anticipated to follow closely behind.

Integration of Bluetooth low energy technology with the Core Specification will be completed in early 2010 and the first Bluetooth low energy enabled products should be available before the end of the calendar year. Upon completion, mobile phone and PC manufacturers may enhance their Bluetooth product offerings with support for Bluetooth low energy wireless technology. End-user devices with Bluetooth v 4.0 are expected to reach the market in late 2010 or early 2011.

Actual status

The Bluetooth low energy specification is available to the general public as part of Bluetooth Core Specification Version 4.0. Actual stage of specification includes some optional features. No commonly published document currently discloses which of these options will be included in the decided chip implementations.

Partners that currently license the technology and cooperate in defining the specification are Alpwise, Broadcom Corporation, CSR, Epson, MindTree, Nordic Semiconductor, and Texas Instruments. Other contributors are Suunto and Taiyo Yuden.^[5]

The first Bluetooth low energy chips, from CSR, Nordic Semiconductor and Texas Instruments, were released to mass-market in late 2010 and early 2011. Bluetooth low energy chips from other semiconductor manufacturers are expected to follow.

Currently (2010–12) the definitions of respective application profiles still are not fulfilled work-items of the standardisation bodies. The first consumer products using Bluetooth low energy are expected to debut in first half of 2011.

Market demand

The Bluetooth SIG follows the market demand for low energy consumption respectively lesser battery wear out. This 2007 Bluetooth SIG adoption move for the 2001 Nokia 'Wibree' proposal was necessary to include low battery consumption operational modes for newly designed devices to communicate with other Bluetooth devices yet deployed. However, the compatibility depends on applications that run on existing Bluetooth devices and made capable for digesting the respective low energy transmissions with software updates. In addition to creating a market for sensors, watches and other existing devices, Bluetooth low energy’s ability to connect low power devices to mobile phones offers a great variety of new applications.

The big advantage is the commonly available equipping of mobile appliances with Bluetooth chips, thus requiring no additional infrastructure for any ad-hoc networking in topologies of peer networking, scatter networking or meshed networking. Technically comparable solutions with other industry groups' standards (e.g. ZigBee, ANT) under the umbrella of the international standard IEEE 802.15.4-2006 show further paths, relying of special infrastructures..

Technical details

BLE operates in the same spectrum range (2402-2480 MHz) as classic bluetooth, but uses a different set of channels. Instead of BT's 79 1 MHz wide channels, BLE has 40 2 MHz wide channels.

Bluetooth low energy is designed with two equally important implementation alternatives: single-mode and dual-mode. Small devices like tokens, watches and sports sensors based on a single-mode Bluetooth low energy implementation will enjoy the low-power consumption advantages enabled for highly integrated and compact devices. In dual-mode implementations Bluetooth low energy functionality is integrated into Classic Bluetooth circuitry. The architecture will share Classic Bluetooth technology radio and antenna, enhancing currently chips with the new low energy stack—enhancing the development of Classic Bluetooth devices with new capabilities.

Technical Specification	Classic Bluetooth	Bluetooth low energy
Distance/Range	100 m (330 ft)	200 m (660 ft)
Over the air data rate	1-3 Mb/s	1 Mb/s
Application throughput	0.7-2.1 Mb/s	0.26 Mb/s
Active slaves	7	Not defined; implementation dependent
Security	64/128-bit and application layer user defined	128-bit AES with Counter Mode CBC-MAC and application layer user defined
Robustness	Adaptive fast frequency hopping, FEC, fast ACK	Adaptive frequency hopping, Lazy Acknowledgement, 24-bit CRC, 32-bit Message Integrity Check
Latency (from a non connected state)	Typically 100 ms	6 ms
Total time to send data (det.battery life)	100 ms	6 ms
Voice capable	Yes	No
Network topology	Scatternet	Star-bus
Power consumption	1 as the reference	0.01 to 0.5 (depending on use case)
Peak current consumption	<30 mA	<20 mA (max 15 mA to run on coin cell battery)
Service discovery	Yes	Yes
Profile concept	Yes	Yes
Primary use cases	Mobile phones, gaming, headsets, stereo audio streaming, automotive, PCs, security, proximity, healthcare, sports & fitness, etc.	Mobile phones, gaming, PCs, watches, sports and fitness, healthcare, security & proximity, automotive, home electronics, automation, Industrial, etc.

More technical details may be obtained from official specification as published by the Bluetooth SIG. Note that power consumption is not part of the Bluetooth spec.

Compatibility

While Bluetooth low energy will be able to coexist with classic Bluetooth devices, it will not be able to communicate with them. Therefore, Bluetooth low energy is not backward compatible with classic Bluetooth devices, but it will be compatible with newer dual-mode devices. For example, for a mobile phone to be able to communicate with Bluetooth low energy devices in addition to classic Bluetooth devices such as Bluetooth headsets, a dual-mode chip is required. Classic Bluetooth hardware cannot be upgraded to dual-mode or low energy compatibility via a software upgrade.

Application profiles

Currently there are no application profiles commonly published. The specification of such profiles has to be expected prior to commonly available appliances.

Health care profiles

Main focus in health care with BLE is vital monitoring. The promoter of such applications is The Continua Health Alliance as an industrial standardisation body.

Sporting profiles

Main focus in sports with BLE is locating as well as vital monitoring. The promoter of such applications is Bluetooth Special Interest Group (SIG) as an industrial standardisation body as well as Continua Health Alliance.

Use cases

Bluetooth low energy is the hallmark feature of v4.0 of the Bluetooth Core Specification. This enhancement to the Bluetooth wireless technology Core Specification that will enable new functionality and applications for remote controls, healthcare monitors, sports sensors and other devices. Bluetooth low energy will enhance existing use cases and will enable new ones, widening the applicability and functionality of Bluetooth.

The respective chips may be integrated into products such as tokens, watches, manual controls, wireless keyboards, gaming pads and body sensors, which may then connect to host devices such as mobile phones, smartphones, personal digital assistants (PDAs), tablet PCs, notebook PCs, laptop PCs and other grades of and personal computers (PCs).

However, currently in the tenth year after earliest publication with inventor Nokia in 2001 (Wibree) there is no implementing on chip-basis or on protocol-basis to any of the current PC-like or PDA-like products or with any mobile phones nor any of the announced appliance products neither disclosed nor announced. All announcement but one is recognised still just with Bluetooth SIG and not beyond (2010-01-27). The notified exception is with a wireless velo-odometer, probably not recognised as the killer-application with mobilephones.

Bluetooth low energy technology hence may extend any personal area network according to the intentions with IEEE 802.15 WPAN to include watches and toys, sports and health care equipment, human interface (HIDs) and entertainment devices.

Electronic leash

Existing solutions of the electronic leash concept get improved with the better economised battery consumtion of the Bluetooth V4.0 low energy protocols. Several suppliers yet offer the so-called electronic leash solution based on standard Bluetooth V2.1 protocols. This serves for wirelessly tethering mobile appliances with each other. The RSSI estimate serves for a radial metrics, but without any certified calibration. Setting an alam on unintentional loss is the key servcice offered with this concept. An advanced aspect has recently been launched with Bluetooth low energy for better economised battery life cycle. Special trimming serves for two years operation from a button cell.

Automatic authentication

Connection-based communication allows for design of secure communication under the qualification schemes of ISO/IEC 15808 Common Criteria standard, however connection-free communication limits the suitability of low energy for secure communications. Beyond classic configurarion of appliances, a personally carried duet of Bluetooth enabled smartphone and a Bluetooth enabled watch allow for an automatic two-factor authentication en passant. Then the watch delivers just an identity in the mode of active RFID.

Automatic context detection and automatic log-off

Detecting operational context may be implemented by detection of coincidence of two or more Bluetooth V4.0 low energy protocol enabled tokens, appliances ans smartphones. This qualifies for better protection of private and corporate data upon access for log-on to networked work positions as well as with mobile network clients.

Whereas currently known solutions rely just on transmission range limitations, the new Bluetooth V4.0 low energy protocol enables for qualified segregation of various operational distances based on assessment of received signal strength. In contrast to known proposals for locating, such unilateral estimation serves for good discrimination of cohesion in operational context, but does not pretend to deliver a certified accuracy, which is impossible due to variations in transmission conditions.

Keeping pace

The community openness of the standard with Bluetooth SIG and compatibility with wireless regulations under the IEEE framework as well as the downward compatibility of the chips allows for a wide acceptance of the additional protocol stack.

Downloading software updates

Presuming the availability of the low energy enabled chip and low energy protocol stack on the target device, the respective applications with existing and deployed devices may be opened to Bluetooth low energy by updates. This will enable the Bluetooth software defined radio to receive signals from Bluetooth low energy devices. However, the capability to communicate in duplex mode is limited with the defined frequency allocation schemes for traditional Bluetooth. The common appliances such as mobile phones, personal digital assistants (PDAs) and personal computers (PCs) may then receive as host devices for complex applications the signals transmitted from Bluetooth low energy devices.

Bluetooth low energy technology hence may extend any personal area network according to the intentions with IEEE 802.15 (WPAN) to network personally carried simple devices with other appliances for complex local applications as well as for gateway support to transfer information to other networked entities.

Standardization

In the market of proprietary connectivity solutions, Bluetooth low energy technology differentiates itself through its:

• widely adopted industry standard for protocols (Bluetooth SIG Bluetooth V4.0 and future later versions)
• widely commonalised application profiles agreed under the auspices of Bluetooth SIG
• multi vendor availability of respective chips
• internationally adopted industry standard for transmission (IEEE 802.15.1)
• possibility to emulate the protocol stack with compliant 2.45 GHz chips (IEEE 802.15)
• low price through single chip integration
• availability of new application via applet downloads
• continuous compatibility with yet deployed Bluetooth devices (V4.0 or later) via software updates

See also

• DASH7
• IEEE 802.15
• Ultra wideband (UWB)
• UWB Forum
• WiMedia Alliance
• WirelessHD
• Wireless USB
• ZigBee – IEEE 802.15.4
• ANT+

References

1. ^ M. Honkanen, A. Lappetelainen, K. Kivekas, "Low end extension for Bluetooth", Radio and Wireless Conference, 2004 IEEE, 19–22 September 2004
2. ^ "Bluetooth rival unveiled by Nokia", BBC News, 4 October 2006
3. ^ Wibree Bluetooth press release 12 June 2007
4. ^ Wibree press release 3 October 2006
5. ^ "Nokia's Wibree and the Wireless Zoo", by Iddo Genuth, The Future of Things (TFoT) online magazine, 16 November 2006
6. ^ "Nordic Semiconductor becomes a member of the open Wibree industry initiative", Nordic Semiconductor press release, 3 October 2006

External links

Official:

• Bluetooth Low Energy website

Websites:

• Wibree news site
• UK Wibree Guide
• HowStuffWorks (How Wibree Works)
• What is Wibree?

News:

• "Bluetooth rival unveiled by Nokia", BBC News, 4 October 2006
• "Nokia's Wibree and the Wireless Zoo", The Future of Things (TFOT), 16 November 2006, An interview with Nokia and a comparison to other wireless technologies