Asynchronous Connection-Less

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Asynchronous Connection-Less (ACL) is a communications protocol. It is used as a transmission link used for data communication in the Bluetooth system or as a definition with access code(72bit) + packet header(54bit) + payload + CRC(16bit).

Asynchronous Connection-Less Link[1] (ACL) is used when data integrity is more important than avoiding latency. In this type of link, if a payload encapsulated in the frame is corrupted, it is retransmitted. A secondary returns an ACL frame in the available odd-numbered slot if and only if the previous slot has been addressed to it. ACL can use one, three or more slots and can achieve a maximum data rate of 721 kbit/s.

Packet types[edit]

DM1, DH1, DM3, DH3, DM5, DH5, AUX1

D(1)(2) (1) M : rate 2/3 FEC used H : no FEC used

(2) 1 : 1 slot used for one frame 3 : 3 slots used for one frame 5 : 5 slots used for one frame


  1. ^ Data Communications and Networking, 4th Edition — Chapter 14 Wireless LANs, Section 14.2 Bluetooth, Page 439