Difference between ACL and SCO Link in Bluetooth



Two types of data links are defined by Bluetooth link layers−

  • Synchronous Connection Oriented (SCO) Link

  • Asynchronous Connection-Less (ACL) Link

SCO is a symmetric, point-to-point link between the master device and the slave device connected via Bluetooth.

ACL is a point – to – multipoint link for transmitting general data packets using Bluetooth connection. ACL is used for irregular traffic between a master device and one or more slave devices.

Differences between SCO and ACL


SCO ACL
1 SCO provides a circuit switched connection, where a dedicated, point-to-point link is established between the master device and the slave device before communication starts.
ACL is a packet oriented link, i.e. the link establishes a packet – switched network.
2 SCO is a symmetric link, i.e. fixed slots are allocated for each direction.
Both symmetric and asymmetric traffic are supported. The master device controls the bandwidth of the ACL link.
3 SCO radio links are used for time critical data transfer, mainly voice data.
ACL is used for transmission of data traffic which are delivered at irregular intervals.
4 A master device can support three SCO links with the same or different slaves. A slave device can have a maximum of three SCO links with its master device.
One master device which connects with maximum seven slave devices via ACL links to form a Piconet.
5 The focus is minimization of time latency.
The main objective is to maintain data integrity rather than time latency.
6 The maximum data rate of SCO link is 64,000 bps (bits per second).
The maximum data rates of ACL links can reach a 57.6 Kbps in downlink and 721 bps in uplink.
7 Packet retransmissions are not allowed, for assuring real-time transfer of voice traffic.
Packet retransmissions are allowed to ensure data integrity.
8 Forward Error Correction (FEC) is applied for data reliability.
Both FEC as well as Backward Error Correction with retransmissions are adopted for data reliability.
Updated on: 2020-09-11T10:42:17+05:30

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