Theory of Operation for Bluetooth

FCC ID: C3KKB11

Operational Description

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FCCID_262354

Forall devices, the following items, 1—12, are commonto all Bluetooth devices and will not vary from one device to another. This list can be copied into thefiling. 1 Output power and channel separation of a Bluetooth device in the different operating modes: The different operating modes (data—mode, acquisition—mode) of a Bluetooth device don‘t influence the output power and the channel spacing. There is only one transmitter which is driven by identical input parameters concerning these two parameters.

Only a different hopping sequence will be used. For this reason, the RF parameters in one op—mode is sufficient. 2 Frequency range of a Bluetooth device: The maximum frequency of the device is: 2402 — 2480 MHz. This is according the Bluetooth Core Specification V 1.0B (+ critical errata) for devices which will be operated in the USA. Other frequency ranges ( e.g. for Spain, France, Japan) which are allowed according the Core Specification must not be supported by the device. 3 Co—ordination of the hopping sequence in data mode to avoid simultaneous occupancy by multiple transmitters: Bluetooth units which want to communicate with other units must be organized in a structure called piconet. This piconet consist of max. 8 Bluetooth units. One unit is the master the other seven are the slaves. The master co—ordinates frequency occupation in this piconet for all units. As the master hop sequence is derived from it‘s BD address which is unique for every Bluetooth device, additional masters intending to establish new piconets will always use different hop sequences. 4 Example of a hopping sequence in data mode: Example of a 79 hopping sequence in data mode: 40,21, 44, 23, 42, 53, 46, 55, 48, 33, 52, 35, 50, 65, 54, 67, 56, 37, 60, 39, 58, 69, 62, 71, 64, 25, 68, 27, 66, 57, 70, 59, 72, 29, 76, 31, 74, 61, 78, 63, 01, 41, 05, 43, 03, 73, 07, 75, 09, 45, 13, 47, 11, 77, 15, 00, 64, 49, 66, 53, 68, 02, 70, 06, 01, 51, 03, 55, 05, 04 5 Equally average use of frequencies in data mode and short transmissions: The generation of the hopping sequence in connection mode depends essentially on two input values: 1. LAP/UAP of the master of the connection 2. Internal master clock The LAP (lower address part) are the 24 LSB‘s of the 48 BD_ADDRESS. The BD_ADDRESS is an unambiguous number of every Bluetooth unit. The UAP (upper address part) are the 24 MSB‘s of the 48 BD_ADDRESS. The internal clock of a Bluetooth unit is derived from a free running clock which is never adjusted and is never turned off. For synchronization with other units, only the offsets are used. It has no relation to the time of the day. Its resolution is at least half the RX/TX slot length of 312.5 us. The clock has a cycle of about one day (23h30). In most caseit is implemented as 28 bit counter. For the deriving of the hopping sequence the entire LAP (24 bits), 4 LSB‘s (4 bits) (Input 1) and the 27 MSB‘s of the clock (Input 2) are used. With this input values different mathematical procedures (permutations, additions, XOR—operations) are performed to generate the sequence. This will be done at the beginning of every new transmission. Regarding short transmissions, the Bluetooth system has the following behavior: The first connection between the two devices is established, a hopping sequence is generated. Fortransmitting the wanted data, the complete hopping sequence is not used and the connection ends. The second connection will be established. A new hopping sequence is generated. Due to the fact that the Bluetooth clock has a different value, because the period between the two transmission is longer (and it cannot be shorter) than the minimum resolution of the clock (312.5 uis). The hopping sequence will always differ from the first one. 6 Receiver input bandwidth, synchronization and repeated single or multiple packets:

'The input bandwidth of the receiver is 1 MHz. In every connection, one Bluetooth device is the master and the other one is the slave. The master determines the hopping sequence (see chapter 5). The slave follows this sequence. Both devices shift between RX and TX time slot according to the clock of the master. Additionally the type of connection (e.g. single or multi—slot packet) is set up at the beginning of the connection. The master adapts its hopping frequency and its TX/RX timing is according to the packet type of the connection. Also, the slave of the connection uses these settings. Repeating of a packet has no influence on the hopping sequence. The hopping sequence generated by the master of the connection will be followed in any case. That means, a repeated packet will not be send on the same frequency, it is send on the next frequency of the hopping sequence 7 Dwell time in data mode The dwell time of 0.3797s within a 30 second period in data mode is independent from the packet type (packet length). The calculation for a 30 second period is a follows: Dwell time = time slot length * hop rate / number of hopping channels *30s Example for a DH1 packet (with a maximum length of one time slot) Dwell time = 625 us * 1600 1/s / 79 * 30s = 0.3797s(in a 30s period) For multi—slot packet the hopping is reduced according to the length of the packet. Example for a DHS packet (with a maximum length of five time slots) Dwell time = 5 * 625 us * 1600 * 1/5 *1/s / 79 * 30s = 0.37978 (in a 30s period) This is according the Bluetooth Core Specification V 1.08 (+ critical errata) for all Bluetooth devices. Therefore, all Bluetooth devices comply with the FCC dwell time requirement in the data mode. This was checked during the Bluetooth Qualification tests. The Dwell time in hybrid mode is approximately 2.6 mS (in a 12.8s period) 8 Channel Separation in hybrid mode The nominal channel spacing of the Bluetooth system is 1Mhz independent of the operating mode. The maximum "initial carrier frequency tolerance" which is allowed for Bluetooth is fcenter = 75 kHz. This was checked during the Bluetooth Qualification tests (Test Case: TRM/CA/OT—E) for three frequencies (2402, 2441, 2480 MHz). 9 Derivation and examples for a hopping sequence in hybrid mode For the generation of the inquiry and page hop sequences the same procedures as described for the data mode are used (see item 5), but this time with different input vectors: **For the inquiry hop sequence, a predefined fixed addressis always used. This results in the same 32 frequencies used by all devices doing an inquiry but every time with a different start frequency and phase in this sequence. **For the page hop sequence, the device address of the paged unit is used as the input vector. This results in the use of a subset of 32 frequencies which is specific for that initial state of the connection establishment between the two units. A page to different devices would result in a different subset of 32 frequencies. So it is ensured that also in hybrid mode, the frequency is used equally on average. Example of a hopping sequence in inquiry mode: 48, 50, 09, 13, 52, 54,41, 45, 56, 58, 11, 15, 60, 62, 43, 47, 00, 02, 64, 68, 04, 06, 17, 21, 08, 10, 66, 70, 12, 14, 19, 23 Example of a hopping sequence in paging mode: 08, 57, 68, 70, 51, 02, 42, 40, 04, 61, 44, 46, 63, 14, 50, 48, 16, 65, 52, 54, 67, 18, 58, 56, 20, 53, 60, 62, 55, 06, 66, 64 10 Receiver input bandwidth and synchronization in hybrid mode:

The receiver input bandwidth is the same as in the data mode (1 MHz). When two Bluetooth devices establish contact for the first time, one device sends an inquiry access code and the other device is scanning for this inquiry access code. If two devices have been connected previously and want to start a new transmission, a similar procedure takes place. The only differenceis, instead of the inquiry access code, a special access code, derived from the BD_ADDRESS of the paged device will be, will be sent by the master of this connection. Due to the fact that both units have been connected before (in the inquiry procedure) the paging unit has timing and frequency information about the page scan of the paged unit. For this reason the time to establish the connection is reduced. 11 Spread rate / data rate of the direct sequence signal The Spread rate / Data rate in inquiry and paging mode can be defined via the access code. The access code is the only criterion for the system to checkif there is a valid transmission or not. If you regard the presence of a valid access code as one bit of information, and compareit with the length of the access code of 68 bits, the Spread rate / Data rate will be 68/1. 12 Spurious emission in hybrid mode The Dwell in hybrid mode is shorter than in data mode. For this reason the spurious emissions average level in data mode is worst case. The spurious emissions peak level is the same for both modes.


Document Created: 2002-06-05 16:18:55
Document Modified: 2002-06-05 16:18:55
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