Bluetooth low energy

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Bluetooth low energy (BLE) branded as Bluetooth SMART since 2011 is a wireless computer network technology which is aimed at novel applications in the healthcare, fitness, security, and home entertainment industries.[1] Compared to "Classic" Bluetooth, BLE is intended to provide considerably reduced power consumption and lower cost, whilst maintaining a similar communication range (see table below).

Bluetooth LE was originally introduced under the name Wibree by Nokia in 2006,[2] but it was merged into the main Bluetooth standard in 2010, when the Bluetooth Core Specification Version 4.0 was adopted.

Contents

Positioning [edit]

Compatibility [edit]

The Bluetooth low energy protocol is not backward compatible with the previous (often called 'Classic') Bluetooth protocol. The Bluetooth 4.0 specification permits devices to implement either, or both, of the LE and Classic systems. Those that implement both are known as Bluetooth 4.0 dual-mode devices.[3]

Bluetooth LE uses the same 2.4 GHz ISM band radio frequencies as Classic Bluetooth, which allows dual-mode devices to share a single radio antenna. LE does, however, use a simpler modulation system.

Bluetooth SMART branding [edit]

In 2011 the Bluetooth SIG announced[4] the Bluetooth SMART logo scheme, intended to clarify compability between LE devices.

  • Bluetooth SMART Ready indicates a dual-mode device - typically a laptop or smartphone - which operates with both Classic and LE Bluetooth peripherals.
  • Bluetooth SMART indicates an LE-only device - typically a battery-operated sensor - which requires either a SMART Ready or another SMART device in order to function.

Note that some 'SMART Ready' devices may need software upgrade to allow full connectivity; for instance, the Samsung Galaxy SIII is listed as SMART ready [5] but current (as of early 2013) versions of Android do not have Bluetooth LE support.

Target Market [edit]

The Bluetooth SIG identifies a number of markets for Low Energy technology, particularly in the 'Health & Wellness' and 'Sport & Fitness' sectors.[6] The claimed advantages are:

  • low power requirements, operating for "months or years" on a button cell
  • small size and low cost
  • compatibility with a large installed base of mobile phones, tablets and computers

One of the major adopters of the Bluetooth low energy protocol stack is the Continua Health Alliance targeting vital monitoring in healthcare.

History [edit]

former Wibree logo, abandoned for Bluetooth logo

In around 2001, researchers at Nokia determined that there were various scenarios that contemporary wireless technologies did not address.[7] The company 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 technology and the new technology. The results were published in 2004 using the name Bluetooth Low End Extension.[8]

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.[9] 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.[10][11]

Integration of Bluetooth low energy technology with version 4.0 of the Core Specification was completed in early 2010.[12] The first device to implement v4.0 spec was the iPhone 4S which came out in October 2011, with a number of other manufacturers bringing out v4.0 devices in 2012.[13]

Applications [edit]

The Bluetooth SIG defines many profiles for Low Energy devices: a profile is a specification for how a device works in a particular application. Manufacturers are expected to implement the appropriate specification(s) for their device in order to ensure compatibility. Bluetooth 4.0 provides low power conception with higher baud rate.

The GATT profile is a general specification for sending and receiving short pieces of data known as 'attributes' over an LE link. All current Low Energy application profiles are based on GATT.[14]

Note that individual devices may implement more than one profile - e.g. one unit could contain both a heart rate monitor and a temperature sensor.

Health care profiles [edit]

There are many profiles for Bluetooth LE devices in healthcare applications. The Continua Health Alliance is a consortium which promotes these, in cooperation with the Bluetooth SIG.

Amongst these profiles are:

  • HRP, the Heart Rate Profile, for devices which measure pulse rate
  • HTP, the Health Thermometer Profile, for medical temperature measurement devices
  • GLP, the Glucose Profile, for blood glucose monitors

Sporting profiles [edit]

Profiles for sporting and fitness accessories include:

  • CSCP, the Cycling Speed and Cadence Profile - allows a sensor attached to a bicycle or exercise bike to measure the cadence and wheel speed.
  • RSCP, the Running speed and cadence profile

Many consumer fitness devices also implement the Heart Rate Profile described above.

Proximity sensing [edit]

"Electronic leash" applications are well-suited to the long battery life possible for 'always-on' devices.[15]

Relevant application profiles include:

  • FMP, the Find Me Profile. Allows a button pressed on one device (e.g. a wristwatch) to cause an alert signal to be shown on another device (e.g. a phone). These devices are referred to as the 'Find Me Locator' and 'Find Me Target', respectively[16]
  • PXP, the Proximity Profile allows one device (the Proximity Monitor) to detect whether another device (the Proximity Reporter) is within a close physical range. Physical proximity can be estimated using the radio receiver's RSSI value, although this does not have absolute calibration of distances. Typically, an alarm may be sounded when the distance between the devices exceeds a set threshold.

Alerts and time profiles [edit]

The Phone Alert Status profile (PASP) and Alert notification profile (ANP) allows a client device (e.g. a wristwatch) to receive notifications from another device (e.g. a phone). This allows the client device to signal to a user that a phone is receiving an incoming call or email message.

The Time Profile (TIP) allows the time (and time zone information) on a 'client' device to be set from a 'server' device. Typically, this is used to allow the current time on a wristwatch to be synchronized to network time as received by a smart phone.B

Implementation [edit]

Bluetooth LE integrated circuit implementations were announced by a number of manufacturers (Broadcom,[17] Texas Instruments,[18] CSR[19] and Nordic Semiconductor[20]), starting in late 2009. An IP block implementation was announced by RivieraWaves in 2010. Commonly, these implementations use software radio, so that updates to the specification can be accommodated through a device firmware upgrade.

LE Compatible Products [edit]

This incomplete list is frequently updated to include new information.
IC Implementations Broadcom BCM20702 [21]
CSR CSR1000/CSR1001[22]
EM Microelectronic EM9301 [23]
Nordic nRF8001 [24]
Texas Instruments: CC2540/1[25]
Software support Apple's CoreBluetooth framework, iOS 5[26] onwards
Linux's Bluez protocol stack from 2011,[27] release 5.0[28] supports numerous profiles
Mobile devices Apple's iPhone 4S,[29] iPad (3rd gen & 4th gen),[30] iPad Mini[31] and others
Nokia Lumia 820 and 920[32]
Samsung Galaxy SIII, Galaxy S4[33], Note II [34]
Microsoft Surface Pro [35]
Blackberry Z10 [36] and Q10 [37]
Peripherals SOREX Bluetoth Door opener with Bluetooth Low Energy [38]
Wahoo Fitness Blue SC cycle cadence/speed sensor[39]
Polar H7 Heart Rate Sensor[40]
Pebble E-Paper Watch [41]
MetaWatch watches [42]
COOKOO smart watch [43]
Shutterbug Remote Shutter Release [44]
Modules RF Digital RFD51822 module[45] and others
Bluegiga BLED112 module[46] and others
Alpwise ALPW-BLEM001 modules[47]
Digi's ConnectCard for i.MX28 System-on-Module[48]
Panasonic PAN1720 series modules [49]
Blue Radio's BR-LE4.0 modules[50]

Status on Android [edit]

In May 2013, Google announced support for Bluetooth LE in the upcoming Android API Level 18 [51]. No support exists in earlier API levels,[52][53] although some devices (e.g. Samsung Galaxy Note 10.1[54]) have compatible hardware. Since BLE has been late to be included with Android, several manufacturers(Samsung [55] and HTC[56]) developed their own SDKs for BLE.

Technical Details [edit]

Bluetooth low energy technology operates in the same spectrum range (2402-2480 MHz) as Classic Bluetooth technology, but uses a different set of channels. Instead of Bluetooth technology's 79 1-MHz wide channels, Bluetooth low energy technology has 40 2-MHz wide channels. Bluetooth low energy technology uses a different frequency hopping scheme to Classic Bluetooth technology; as a result, while both FCC and ETSI classify Bluetooth technology as an FHSS scheme, Bluetooth low energy technology is classified as a system using digital modulation techniques or a direct-sequence spread spectrum.

Bluetooth low energy technology 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 available chips with the new low energy stack—enhancing the development of Classic Bluetooth devices with new capabilities.[57]

Technical Specification Classic Bluetooth technology Bluetooth low energy technology
Distance/Range 100 m (330 ft) 50 m (160 ft)
Over the air data rate 1-3 Mbit/s 1 Mbit/s
Application throughput 0.7-2.1 Mbit/s 0.27 Mbit/s
Active slaves 7 Not defined; implementation dependent
Security 56/128-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 3 ms[citation needed], <3 ms[58]
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
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 specification.

Low power consumption [edit]

Devices using Bluetooth low energy wireless technology are expected to consume a fraction of the power of Classic Bluetooth enabled products for Bluetooth communication. In many cases, products will be able to operate more than a year on a button cell battery without recharging. It will allow sensors such as thermometers to operate continuously, communicating intermittently with other devices such as a mobile phone. This may increase the concerns for privacy, as when the remote, low power, continuously on, sensor would be present in devices with BLE.[57]

Note that the lower power consumption is not achieved by the nature of the active radio transport, but by the design of the protocol to allow low duty cycles, and by the use cases envisaged. A Bluetooth low energy device used for continuous data transfer would not have a lower power consumption than a comparable Bluetooth device transmitting the same amount of data. It would likely use more power, since the protocol is optimised for small bursts.

The basic radio circuitry has almost similar power consumption as for standard Bluetooth radio (in dual-mode devices it is likely to be the same circuitry), but the overall power consumption is aimed to be lower, primarily by having a lower duty cycle. During transmission and reception these devices exhibit peak currents in the tens of milliamps (mA) range in both Bluetooth low energy technology and Bluetooth modes. In sleep modes, the aim is to have current consumption 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.

See also [edit]

References [edit]

  1. ^ www.bluetooth.com, What is Bluetooth Technology
  2. ^ HowStuffWorks.com
  3. ^ Bluetooth Smart Marks FAQ
  4. ^ Bluetooth SMART marks, Bluetooth SIG press release
  5. ^ Bluetooth list of Smart devices
  6. ^ Bluetooth SIG 'Markets' pages
  7. ^ The Future Of Things, Nokia's Wibree and the Wireless Zoo]
  8. ^ M. Honkanen, A. Lappetelainen, K. Kivekas, "Low end extension for Bluetooth", Radio and Wireless Conference, 2004 IEEE, 19–22 September 2004
  9. ^ "Bluetooth rival unveiled by Nokia", BBC News, 4 October 2006
  10. ^ Wibree Bluetooth press release 12 June 2007
  11. ^ "Wibree becomes Ultra low power Bluetooth technology". electronicsweekly.com. Retrieved 2008-09-09. 
  12. ^ "Bluetooth Low Energy". Bluetooth.com. Retrieved 2012-08-23. 
  13. ^ "iPhone 4S release article". Runningdigital.com. Retrieved 2012-08-23. 
  14. ^ Bluetooth SIG Adopted specifications
  15. ^ Casio watch with Bluetooth low energy profile
  16. ^ Find Me Profile specification
  17. ^ Broadcom press release, Feb 2010
  18. ^ TI press release Oct 2009
  19. ^ CSR press release Dec 2009
  20. ^ Nordic press release Nov 2009
  21. ^ Broadcom BCM20702
  22. ^ CSR CS1000
  23. ^ EM Micro EM9301
  24. ^ Nordic Semiconductor nRF8001
  25. ^ TI CC2540 page
  26. ^ What's new in iOS5
  27. ^ BlueZ blog post, Jan 2011
  28. ^ BlueZ 5.0 release announcement
  29. ^ iPhone 4S BLE software
  30. ^ iPad (3rd gen) Specifications
  31. ^ iPad Mini Specifications
  32. ^ Bluetooth 4.0 Certification comes to Nokia 920 and 820
  33. ^ [1]
  34. ^ [2]
  35. ^ Microsoft Surface Pro specifications
  36. ^ [3]
  37. ^ [4]
  38. ^ SOREX wireless key
  39. ^ Wahoo Fitness Blue SC
  40. ^ Polar H7 Heart rate sensor
  41. ^ Update #10: And one more thing...
  42. ^ MetaWatch specifications
  43. ^ Cookoo watch features
  44. ^ Shutterbug Remote Main Site
  45. ^ [5]
  46. ^ Bluegiga BLE modules
  47. ^ Alpwise Bluetooth low energy development kit and Bluetooth low energy module
  48. ^ Digi embedded System-on-Module with BLE
  49. ^ Panasonic PAN1720 RF module
  50. ^ BlueRadio BR-LE4.0 modules
  51. ^ https://developers.google.com/events/io/sessions/326240948
  52. ^ change.org petition - add Bluetooth LE support to Android
  53. ^ Android Needs To Get Serious About Bluetooth Low Energy, Jan 2013
  54. ^ Galaxy Note 10.1 specifications
  55. ^ http://developer.samsung.com/ble
  56. ^ http://www.htcdev.com/devcenter/opensense-sdk/partner-apis/bluetooth-low-energy/
  57. ^ a b Core Specification Version 4.0. https://www.bluetooth.org/Technical/Specifications/adopted.htm
  58. ^ Bluetooth Wireless Technology vs. ZigBee (IEEE 802.15.4) Specification Comparison

External links [edit]

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