Adaptive Frequency Hopping (Option 15) AFH in Bluetooth 1.2
MT8852B Operation Manual PN: 13000-00205 Rev. N 15-3
Channel map generation is illustrated in the figure below.
The channel map can be modified by the master device at any time during the life of a
connection and is adopted immediately upon transmission to the slave.
In addition to the channel map, AFH also requires that Bluetooth devices communicate using
the Same Channel Mechanism whereby, instead of changing frequency with each transmit
and receive slot, the frequency is only changed after each complete transmit and receive cycle.
15-3 AFH in Bluetooth 1.2
The Bluetooth Specification states that the master device creates the AFH Channel Map from
any of the three sources identified above, but it does not dictate the method of channel
assessment that should be used to identify the good and bad channels. Two common methods
for making this judgement are Received Signal Strength Indication (RSSI), and Packet Error
Rate (PER).
The following changes have been made to the 1.2 specification to enable the use of AFH.
• New messages have been added to the Link Manager Protocol to enable communication
of the channels that can be used and the channels that have been blocked.
• Commands have been added to the Host Controller Interface to allow the blocking of
"known bad" channels and to allow the host to obtain the channel map currently in use.
Figure 15-3. Channel Map Generation
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