BLE Overview

URL : http://www.summitdata.com/blog/ble-overview/

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Differences Between Classic Bluetooth and BLE

 The classic Bluetooth specification defines a uniform structure for a wide range of devices that connect to each other. Bluetooth operates primarily using ad hoc piconets. A master device controls up to seven slaves per piconet; the slaves communicate with the master device but they do not communicate with each other. However, a slave device may participate in one or more piconets, essentially a collection of devices connected via Bluetooth. A summary of classic Bluetooth topology with multiple piconets, called scatternet, can be found below.

In a BLE topology, the slaves each communicate on a separate physical channel with the master. Unlike a classic Bluetooth piconet, where all slaves listen for incoming connections and therefore need to be on constant standby, a BLE slave invites connections and so is in total control of when to consume power. A BLE master, which is assumed to have less power constraints, will listen for advertisements and make connections on the back of an advertisement packet. A diagram of this can be found below.

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The table below compares classic Bluetooth and BLE.

Technical Specification	Classic Bluetooth	Bluetooth Low Energy
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 (depending battery life)	100 ms	3 ms, less than 3 ms
Voice capable	Yes	No
Network topology	Scatternet (See figures above)	Star-bus (See figures above)
Power consumption	1 as the reference	0.01 to 0.5 (depending on the use case)
Peak current consumption	Less than 30 mA	Less than 20 mA
Service discovery	Yes	Yes
Profile concept	Yes	Yes

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