Bluetooth adaptive frequency hopping and the low power modes
J. Nelson · 2004
In version 1.2 of Bluetooth, one of the new features adopted was adaptive frequency hopping (AFH). AFH enables a device to use a subset of the allocated 79 frequencies, by effectively detecting and eliminating interfering channels. Bluetooth devices can classify and report frequencies as good, bad or unknown. This improves Bluetooth co-existence in the 2.4 GHz ISM band with other users such as wireless LAN, and in particular with the 802.11 variants. A number of implementation issues and trade-offs arise when attempting to use AFH. These include calculating the hop indices, and communicating the changing frequency sets to all slaves to maintain hop synchronisation. This paper addresses these issues. The analysis of the new hop selection engine indicates that it can be simplified for implementation. The low power features defined in version 1.0 of Bluetooth, namely Hold, Sniff and Park, complicate the frequency set updating. The characteristics of these low power modes, which present challenges for consistent piconet updating are addressed. The target is to ensure improved interoperability.