Bluetooth Low Energy Details: Bluetooth 4
SUMMARY
Bluetooth Low Energy is embodied in
the Bluetooth 4 protocol announced recently by the Bluetooth
Special Interest Group (SIG)
The major features are:
- Ultra-low peak, average and idle mode power consumption
- Ability to run for extended periods (years) on standard button batteries
- Low cost
- Interoperability between vendors
- Enhanced range
There are two implementations: single-mode and dual-mode:
Dual-mode implementation
Bluetooth low energy functions are integrated with standard
Bluetooth chips. All the features of standard Bluetooth
including Bluetooth V2.1 + EDR or Bluetooth V3.0 + HS are
available along with the new Bluetooth Low Energy functions at
essentially the same cost as conventional Bluetooth.
Single-mode Implementation:
These are single low cost Bluetooth Low Energy chips which
provide a Link Layer with ultra-low power idle, simple device
discovery, and point-to-multipoint data transfer including
power-save and updated security.
Bluetooth Low Energy Technical Details
- Data Transfer: very short data packets from 8 octet to 27 octets transferred at 1 Mbps. Connections use advanced sniff-subrating (a special sleep mode) for ultra low duty cycles.
- Frequency Hopping: Bluetooth Low Energy employs the same adaptive frequency hopping as is used in conventional Bluetooth. This serves to minimise any interference from other wireless technologies in the 2.4 GHz ISM Band.
- Host Control: Bluetooth low energy technology places a significant amount of intelligence in the controller, which allows the host to sleep for longer periods of time and be woken up by the controller only when the host needs to perform some action. This allows for the greatest current savings since the host is assumed to consume more power than the controller.
- Latency: Bluetooth low energy technology can support connection setup and data transfer as low as 3ms, allowing an application to form a connection and then transfer authenticated data in few milliseconds for a short communication burst before quickly tearing down the connection.
- Range: Increased modulation index provides a possible range for Bluetooth low energy technology of over 100 meters.
- Robustness: Bluetooth low energy technology uses a strong 24 bit CRC on all packets ensuring the maximum robustness against interference.
- Strong Security: Full AES-128 encryption using CCM to provide strong encryption and authentication of data packets.
- Topology: Bluetooth low energy technology uses a 32 bit access address on every packet for each slave, allowing billions of devices to be connected.The technology is optimized for one-to-one connections while allowing one-to-many connections using a star topology. With the use of quick connections and disconnections, data can move in a mesh-like topology without the complexities of maintaining a mesh network.
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