Adaptive Frequency Hopping in Bluetooth Module

Jency,

       Please find some comments below.

Jency MS said:

  How  BT module implement AFH?

Miguel said:

The full AFH mechanism is followed per the BT specifications with a special "sauce" from TI. Please note that the slave(s) recommend(s) the mapping  but the master decides ultimately. The TI propietary solution provides a very fast AFH algorithm with minimum adoption time.

Jency MS said:

  When does the Bluetooth device scan (“sniff”) the frequency space to determine which channels to omit from the hopping sequence?

Miguel said:

It occurs dynamically during a connection.

Jency MS said:

  Is this done only at the time the devices are paired? Or is it done periodically every "x "seconds?

Miguel said:

Yes, it is done continuously while the connection is alive.

Jency MS said:

  What criteria is used to determine whether a Bluetooth channel is to be removed from the hopping sequence?

Miguel said:

As mentioned early, it follows the BT specification from a system level where the slave recommends and master decides. In the case of TI devices, it accounts for different parameters in order to reduce adoption time, false interferers and other key features.

Jency MS said:

  Once a channel is removed from the hopping sequence, how long does it stay removed from the hopping sequence?

Miguel said:

 It depends on the scenario and environment conditions but it would usually be in the seconds range 

Jency MS said:

  Does it stay removed until the devices are re-booted or re-paired? Or does it stay removed until a sub sequence “sniff” of that channel determines the channel is now clear for use? If so, what is the criteria used for denoting a channel as “clear for use”? Or is the channel added back into the hopping sequence automatically after x seconds?

Miguel said:

No, the AFH map is updated continuously during a connection. It depends on the scenario and environment conditions to decide when to remove or add a bad channel from the list .

Regards,

Miguel

Jency,

Please find comments below:

Jency MS said:

Is any significantly degrade in Wi-Fi throughput when 30 Bluetooth devices are nearby transmitting data, It there any way to rectify it

Miguel said:

Since the WiFi is the affected device, I would recommend checking that with your WiFi vendor. If you want to have a complete WiFi-BT solution with coexistence integrated, I would recommend using our WiFi-BT radio, WL127x. http://processors.wiki.ti.com/index.php/ARM_Processor_Wireless_Connectivity_WL1271_device 

Jency MS said:

Does the channel selection criteria is based on the received signal strength of the other RF devices (i.e. Wi-Fi and other interferers) on that channel frequency? If so, at what dB level does this “interference” need to be at for the Bluetooth device to omit that channel from its hopping sequence.  Or does AFH use bad packet reporting from the slave device on the piconet to determine which channels to remove from the hopping sequence? In other words, the master Bluetooth device will only remove a channel from the hopping sequence if it receives X number of “bad packet” replies from the slave Bluetooth device

Miguel said:

It does use RSSI and PER reports but also it takes into consideration other parameters to avoid false alarms.e.g. It won't remove channels from other BT activities. 

Hello Carol,

     The CC2567 AFH mechanism is meant to protect and maintain a good BT connection. In your case, it seems that the WLAN device is the one having issues. You may want to use the standard "HCI_Set_AFH_Host_Channel_Classification" command if you want to block specific BT channels during this mode; however, this may cause some degradation in the BT performance if the host does not classify the channels correctly.

Regards,

Miguel