doc.: IEEE /0127r0 Submission January 2009 John R. Barr, Motorola, Inc.Slide 1 Bluetooth AFH and IEEE Date: Authors:

doc.: IEEE /0127r0 Submission January 2009 John R. Barr, Motorola, Inc.Slide 2 Abstract Over 2.5 Billion Bluetooth® wireless devices have been shipped based on the IEEE Std ™ Many of these devices implement the Adaptive Frequency Hopping (AFH) mechanism recommended in IEEE Std ™-2003 subsequently incorporated into IEEE and all recent Bluetooth specifications. An overview of AFH mechanism and mapping of IEEE onto current Bluetooth specifications is provided to provide an understanding of the impact of new 2.4 GHz channel models on reliable operation of devices used every day by billions of satisfied users.

doc.: IEEE /0127r0 Submission Adaptive Frequency Hopping Definition: (From IEEE ) –IEEE systems frequency hop over 79 channels (in the U.S.) at a nominal rate of 1600 hops/second in connection state, and 3200 hops/second in inquiry and page states. By identifying the channels with interference, it is possible to change the sequence of hops such that those channels with interference (“bad” channels) are avoided. From traffic type and channel condition, a partition sequence is generated as input to the frequency re- mapper, which modifies hopping frequencies to avoid or minimize interference effects. January 2009 John R. Barr, Motorola, Inc.Slide 3

doc.: IEEE /0127r0 Submission Bluetooth AFH Summary Optional feature in current specifications, and under consideration to become mandatory feature in future specifications: –IEEE and Bluetooth v1.2 were first to implement feature. –IEEE based on and identical to PHY and MAC layers of Bluetooth v1.2. –Bluetooth v1.2 also includes high layer specifications required to implement service discovery and other interoperability features. AFH feature defines mechanisms to acquire channel characteristics and update hopping kernel based on local and remote channel characteristics Channel assessment methods are not defined in Bluetooth specifications, but left to implementations January 2009 John R. Barr, Motorola, Inc.Slide 4

doc.: IEEE /0127r0 Submission Bluetooth AFH Operation AFH only applied when devices are connected. Paging and Inquiry modes use all channels, but are only present when devices are searching for others. Master Bluetooth device operating using an adapted channel hopping sequence initiates connections using full 79 channel hopping sequence and then updates the channel hopping sequence using the AFH channel map. The AFH channel map is determined by master measurements and responses from slave devices requested by the master regarding which channels have acceptable performance levels. The adapted channel hopping sequence consists of the initial 79 channel hop sequence modified by the master’s AFH channel map AFH channel map indicated which RF channels shall be used and which shall be unused. Number of channels used shall be >20 to meet regulations. January 2009 John R. Barr, Motorola, Inc.Slide 5

doc.: IEEE /0127r0 Submission Effect of 40MHz n Channels Channel assessment methods in Bluetooth chip sets detect presence of RF energy in one or more of the 79 1 MHz channels in the 2.4 GHz band used for Bluetooth transmissions n signals from devices within 3-5 meters of a Bluetooth device will cause channels to be marked as occupied: –Number of channels detected can be more than 60 when devices are within 1-2 meters of each other. AFH channel map will be reduced to minimum of 20 channels to avoid 40MHz n transmissions January 2009 John R. Barr, Motorola, Inc.Slide 6

doc.: IEEE /0127r0 Submission Impact of 40MHz n Channels Bluetooth devices is close proximity may effectively reduce their adaptive hop sequence to best 20 channels. Some implementations may increase their minimum limit to greater than n devices will no longer detect presence of Bluetooth devices in their 40 MHz channel. Bluetooth devices will compete for access to 25% of the 2.5 GHz band and will not be able to recover from other interferers as quickly. Bluetooth devices may increase power levels to reduce packet loss which will further limit spectrum reusability for other Bluetooth device pairs in the same area. Bluetooth applications may experience increased levels of packet loss that can be recovered via retransmissions, but with an energy consumption impact. January 2009 John R. Barr, Motorola, Inc.Slide 7

doc.: IEEE /0127r0 Submission Bluetooth v2.1 + EDR Changes All Bluetooth specifications are backwards compatible with Bluetooth v1.2 that has same PHY characteristics as IEEE Bluetooth v1.2 modulation: –The Modulation is GFSK (Gaussian Frequency Shift Keying) with a bandwidth-bit period product BT=0.5. The Modulation index shall be between 0.28 and Bluetooth v2.1 + EDR Additions: –The PSK modulation format defined for the 2 Mbps transmission shall be π/4 rotated differential encoded quaternary phase shift keying (π/4-DQPSK). –The PSK modulation format defined for the 3 Mbps transmission shall be differential encoded 8-ary phase shift keying (8DPSK). January 2009 John R. Barr, Motorola, Inc.Slide 8

doc.: IEEE /0127r0 Submission References Specification of the Bluetooth System, Core V2.1 _ EDR.pdf, e_Specification_v21__EDR.htm e_Specification_v21__EDR.htm IEEE Std ™-2005 IEEE Std ™-2003 January 2009 John R. Barr, Motorola, Inc.Slide 9