Changes with respect to Bluetooth 2.1
The major changes with respect to Bluetooth 2.1 has been mainly in Security and power saving. Few of the features like secure simple pairing are visible to the end user. And others indirectly aid better user experience though not measurable.
Below is the list of new features added for Bluetooth 2.1.
Secure Simple Pairing
The primary goal of Secure Simple Pairing (SSP) is to simplify the pairing procedure for the user. Secondary goals are to maintain or improve the security in Bluetooth wireless technology.
While in SSP mode user does not have to explicitly enter the predefined pass key. Bluetooth itself generates a random passkey and user is expected to confirm the same depending on I/O capabilities of the pairing devices. These I/O capabilities are Just works, Numeric Comparison, Pass Key entry and OOB.
If remote devices does not have any entry or display capabilities Just Works method is used. User just gets a pairing notification and both the devices are automatically paired. This is a typical use case scenario between a headset and a handset.
In numeric comparison user is shown a 6 digit number on both devices. Pairing is considered successful if both devices display same 6 digit number. User can accept pairing by confirming that both devices are displaying same 6 digit number. This is a typical user case scenario between 2 devices having display and input capabilities. Like 2 handsets or handset and PC.
In Pass key entry method display capable device displays the 6 digit number and other device with only input capabilities like Key Board should confirm the same by entering the displayed number.
In OOB method authentication information is exchanged using other technologies like NFC.
Sniff Subrating
Sniff subrating provides a mechanism for further reducing the active duty cycle, thereby enhancing the power-saving capability of sniff mode. Sniff subrating allows a Host to create a guaranteed access-like connection by specifying maximum transmit and receive latencies. This allows the basebands to optimize the low power performance without having to exit and re-enter sniff mode using Link Manager commands.
If both devices support Sniff subrating, these devices can negotiate sniff anchor points on which the devices will listen or transmit. Hence, instead of waking up for every sniff anchor point devices defer this to multiples of sniff anchor point slots. However this feature will be useful for only devices which will have longer sleep modes like HID devices.
Extended Inquiry
This feature provides more information during the inquiry procedure to allow better filtering of devices before connection. This information may include the name of the device; a list of services the device supports and the transmission power level used for inquiry responses. Hence for 2.1 devices an explicit SDP may not be required.
1.4 Erroneous Data Reporting
This feature is used to report erroneous data received during SCO and eSCO transmissions. With each SCO/eSCO packet being received or lost in SCO/eSCO slot, controller sends out status flag indicating whether packet is corrupted. Host can use this information to change SCO/eSCO packets.
Link Supervision Timeout Changed
The Link_Supervision_Timeout_Changed event is used to notify the slave's Host when the Link_Supervision_Timeout parameter is changed in the master Controller.
Enhanced Flush
This feature supports flushing specific Bluetooth packets.
Refresh Encryption Key
This is explicitly used by Host to pause and refresh the encryption keys. By using this command, devices can keep changing encryption keys time to time to avoid link being decrypted using persistent attacks.
