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Bluetooth Smart,Bluetooth Low Energy tutorial,BLE tutorial

This page of tutorials section covers Bluetooth Smart or Bluetooth Low Energy tutorial. This BLE tutorial covers BLE technology features,BLE(Bluetooth Low Energy) network, BLE channels, BLE messages, BLE protocol stack, BLE Applications (BLE Apps) etc.

Also refer bluetooth tutorial covering following sub topics:
Main Page  Frequency  PHY Layer  MAC layer  Stack  Power classes  Security  products  versions  Bluetooth Vs BLE 

There are various applications of short range wireless communications such as voice, data, audio, video etc. Various standards have been developed to support these application areas such as bluetooth, wifi, zigbee, ANT etc. In bluetooth there are different versions based on data rate and distance coverage requirements such as version 1.2, 2.0, 2.1, 3.0, 4.0 and 4.1. Bluetooth version 4.0 is known as Bluetooth Low Energy (BLE). It is also known by the name Bluetooth Smart.

Bluetooth Smart is a low power, low bandwidth and low latency data communication technology. In conventional bluetooth connection is established between bluetooth devices for communication. Once the devices are connected with bluetooth link the connection is maintained even if there is no data to be transferred. Devices go to sleep in sniff mode and hence battery life can be enhanced. Here peak transmit current is less than 25 mA. Though this power is less, it is not low enough to run the coil cell based applications. Bluetooth Low Energy (BLE) standard has been mainly targetted for small chunks of data transfer.

Bluetooth Low Energy-BLE specifications

Specification BLE technology Support
Channel Frequency 40 channels (3 advertising, 37 data)
Distance coverage 50 meters (150 meters outdoor)
Current Consumption ~15 mA
Data rate of opeartion 1Mbps
Modulation scheme GFSK
Output Power 10 dBm
Device types Master and Slave
Device Modes Dual mode(Supports BLE and traditional bluetooth), single mode (Support BLE)
Wireless Network Modes Point to Point and Star
System Robustness Adaptive frequency hopping with 24 bit CRC in the packet
Security 128 bit AES CCM
Time for data to be transmitted from one end to the other (i.e. latency) 3 ms
Current consumption during sleep mode 1 µA

BLE Network Topology

BLE network topologies
Fig:1 BLE (Bluetooth Low Energy) Network

As shown in the figure-1 bluetooth low energy supports star and point to point topologies. Point to Point (P2P) is used for pairing two BLE devices. In this mode, one BLE device acts as master and the other BLE device acts as slave device. The other topology star is used when there are multiple BLE nodes. In this topology, one node functions as central node and acts as master while all the other nodes function as slave nodes.

BLE Frequency Channels

Bluetooth Smart or BLE frequency channels
Fig:2 Bluetooth Smart (BLE) Frequency Channels

As shown in the figure-2, Bluetooth Smart supports 40 channels, each with spacing of 2 MHz. There are 3 advertising channels and 37 data channels. Advertising channels are allocated in the frequency space other than the 802.11 allocated frequency spectrum space to avoid interference.

BLE Message Exchange

BLE messages
Fig:3 Messages exchanged between BLE devices

Figure-3 depicts messages exchanged between the BLE devices (master and slave).
• Once connection is established between master and slave using advertising channels following is done.
• Master informs slave about hopping sequence and when to wake up.
• All the subsequent transactions are performed using 37 data channels.
• Encryption can be applied to the data communicated.
• Both master and slave devices will go to deep sleep mode between the transactions.
It takes about 3 ms to have complete data transfer including initial message handshake to complete the connection between bluetooth low energy or bluetooth smart devices.

Bluetooth Smart (BLE) Protocol Stack

Bluetooth Low Energy, BLE stack
Fig:4 Bluetooth Smart or Bluetooth Low Energy or BLE Stack

Figure-4 depicts protocol stack for standard bluetooth device, dual mode device and single mode device. Dual mode device supports both BLE and Standard bluetooth protocols and hence it can interoperate with standard bluetooth devices as well as BLE devices.

Bluetooth Smart/Bluetooth Low Energy/BLE Applications(Apps)

Following are the BLE applications or use cases of Bluetooth Smart/Bluetooth Low Energy/BLE technology:
• Proximity  • Time
• Emergency  • Network availability
• Personal User Interface • Simple remote control
• Browse over Bluetooth • Generic I/O (automation)
• Temperature Sensor  • Humidity Sensor
• HVAC • Battery status
• Heart rate monitor • Physical activity monitor
• Blood glucose monitor • Cycling sensors
• Pulse Oximeter • Body thermometer
There are many more BLE apps other than the one mentioned above.

This BLE tutorial or Bluetooth Low Energy tutorial is useful for beginners as well as experienced bluetooth enthusiats. One can also refer standard or traditional bluetooth tutorial for more information as both bluetooth and BLE have some similarities and differences.
Refer Bluetooth tutorial and Difference between Bluetooth and BLE.

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