The Bluetooth® data transmission system implements a layered structure. The description of the Bluetooth system explains the Bluetooth core transmission level (including the L2CAP channel). All Bluetooth operating modes follow the same general transmission structure.

Data transmission structure

Based on efficiency and traditional reasons, the Bluetooth transmission structure includes the hierarchical division of the logical layer, which is clearly distinguished from logical links and logical transmissions. This level division provides general and easy-to-understand concepts about logical links, which provide independent transmission for two or more devices. Based on the legacy behavior reasons, the logical transmission layering needs to describe the interdependence of some logical link types.

The Bluetooth version 1.1 specification stipulates that ACL and SCO links are physical links. In addition to the addition of extended SCO (eSCO) and future expansion, it is ideal to regard these two links as logical transmission types.