At a Glance
1. Enhanced Attribute Protocol
An improved version of the Attribute protocol (ATT), called the Enhanced Attribute protocol (EATT),
has been introduced along with some associated improvements to the Generic Attribute
Profile (GATT).
EATT supports concurrent transactions, allows the interleaving of L2CAP packets relating to ATT
packets from different applications, and allows the ATT Maximum Transmission Unit (MTU) to be
changed during a connection. Collectively, these changes can provide an improved user experience
on devices where there are multiple applications using the Bluetooth Low Energy (LE) stack at the
same time, through reducing instances where one application’s use of the stack temporarily blocks
that of another. This can reduce the end- to- end latency of one or more of the applications and
improve the user’s experience of responsiveness.
In support of EATT, a new L2CAP mode has been defined. The new mode is called the L2CAP
Enhanced Credit Based Flow Control Mode. This mode provides flow control and so allows
applications to regard the protocol as reliable.
EATT has security advantages over unenhanced ATT as it may only be used over an
encrypted connection.
2. LE Power Control
The new LE Power Control makes it possible for devices to dynamically optimize the transmission
power used in communication between connected devices. Bluetooth LE receivers may now monitor
signal strength and request transmission power-level changes in connected devices, typically to
maintain an optimal signal strength from both a signal quality and low- power-use perspective.
The Bluetooth controller can monitor and report path loss changes to the Bluetooth host using the
concept of zones, which some application types will find useful.
Benefits of the LE Power Control feature include:
1. The reduction of overall power consumption by transmitters through dynamic power
management conducted between connected devices.
2. Improvements in reliability through the active maintenance of receiver signal strength so that
it stays within the optimal range supported by the receiver.
3. Improvements relating to coexistence with other wireless devices that are in the environment
and are using the 2.4 GHz frequency range. This benet applies to all such devices, not just
those that are using Bluetooth.
bluetooth.com | 5
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