Inside Bluetooth. Host. Bluetooth. Module. Application RFCOMM SDP. Transport Interface. Transport Bus. Host Controller Interface

Transcription

1 Inside Bluetooth Application Host Application Host Audio (SCO) RFCOMM SDP Data (ACL) Control API and Legacy Support Modules Bluetooth HCI Driver Transport Interface Physical I/F Transport Bus Bluetooth Module Audio (SCO) Host Controller Interface Data (ACL) L2CAP Link Manager Baseband RF (radio and antenna) Control Physical I/F HCI Firmware Logical Link Control & Data Adaptation Physical Link Control Data Processing & Transmission Mgmt. Transmission/Reception

2 L2CAP Logical Link Control and Adaptation Protocol Manages the creation and termination of virtual connections with other Bluetooth devices Negotiates and/or dictates parameters Including Security and Quality of Service (QoS) Manages ACL data flow between the host and Link Manager Multiplixing of multiple concurrent host I/O operations Segmentation And Reassembly (SAR) of various data formats for baseband compatibility

3 Link Manager Physically manages creation, configuration, and termination of device to device links Also manages ACL data flow between the L2CAP and Baseband through established links Forwards data from the L2CAP to the Baseband with its associated link specific transmission parameters Forwards data from the Baseband back to the L2CAP associated to its specific source link

4 Baseband Performs all digital data processing operations Speech coding Data whitening Optional encryption/decryption Packetization Header and payload error detection and correction Calculates and controls transmission frequency Supporting Bluetooth s 8 channel Frequency Hopping (FH) spread spectrum transmission method

5 How Does Bluetooth Work? Operational States D F Master Active Slave M N O J Parked Slave* Standby* * Low power state I C P Q

6 In the Beginning Initially Bluetooth devices only know about themselves Everyone passively monitors in Standby mode No devices are synchronized D F H G M N O J E I A K C B L P Q

7 Inquiry Discovering Who s Out There Inquiry discovers what other devices within range D F H G M N O J E I A K C B L P Q meters

8 Paging Creating a Piconet Paging creates a Master/Slave link called a Piconet D F H G M N O J E I A K C B L P Q meters

9 Expanding a Piconet (1) Successive Pages can attach up to 7 Active Slaves to a Piconet at one time D F H G M N O J E I A K C B L P Q meters

10 Parking To save power and/or to connect to even more devices Active Slaves can be Parked (up to 256 total!) D F H G M N O A B P J E I K C L Q meters

11 Expanding a Piconet (2) Masters can then attach additional Active Slaves using Active Member Addresses freed up through Parking D F H G M N O A B P J E I K C L Q meters

12 Scatternets Bluetooth devices can participate in multiple Piconets simultaneously creating a topologies called Scatternets D F H G M N O J E I A K C B L P Q

13 Advanced Scatternets Scatternets can evolve into extremely complex structures creating a rich fabric of many, many, devices D F H G M N O J E I A K C B L P Q

14 Bluetooth Radio Basics Normal range: meters Normal xmit power: 1 milliwatt Receiver sensitivity: -7 db Frequency band: 2.4 GHz(ISM) Max data rate: 721Kbps + 56Kbps X 3 (voice)

15 Bluetooth Radio Frequency Band ISM (Industrial, Scientific, Medical) band 2.2GHz GHz (79MHz total bandwidth) Advantages Free Open to everyone worldwide Disadvantages Noise sources from everywhere Cordless phones, microwave ovens, garage door openers, other wireless LAN technologies, baby monitors,...

16 Bluetooth s Noise Solutions Frequency Hopping (FH) Spread Spectrum technology Divides the band into 79 separate 1MHz channels Uses short packets and makes 16 hops/second Minimizes exposure to noisy channels Enables bad voice packets to be discarded Forward Error Correction (FEC) of data packets Data often recoverable even on a noisy channel without retransmission

17 Bluetooth Transmission Protocol Frequency Hopping & Time Division Duplexing f k f k+1 f k+2 f k+3 Master Slave1 625 µs Slot 1 Slot2 625 µs Slot 3 Slot4 t Frame 1 Frame 2 Complete packet transmission occurs during a Slot Frequency hops from Slot to Slot to Slot Frames define matched Master / Slave Slot transmissions

18 Frequency Hopping Graphically Illustrated Each channel can carry a separate Bluetooth transmission without contention Transmission Channel (1-79) Transmission Slot (time) Piconet A Contention Active Piconets: 1 Total Transmission Slots: Transmission Slots Hit: Transmission Efficiency: ~%

19 8 Each Bluetooth Piconet Randomly Changes Frequency Slot by Slot by Slot Piconet A Contention Active Piconets: 1 Total Transmission Slots: Transmission Slots Hit: Transmission Efficiency: ~%

20 Frequency Hopping Minimizes Exposure to Data Loss Due to Noise MHz noise source Piconet A Contention Active Piconets: 1 Total Transmission Slots: Transmission Slots Hit: 7 Transmission Efficiency: ~% ~93%

21 8 Frequency Hopping With Multiple Piconets Piconet A Piconet B Piconet C Piconet D Contention Contention Contention Contention Active Piconets: 4 Total Transmission Slots: Transmission Slots Hit: Transmission Efficiency: ~95%

22 8 Bluetooth Piconets Degrade Gracefully with Density Piconet A Piconet B Piconet C Piconet D Piconet E Piconet F Piconet G Piconet H Piconet I Piconet J Contention Contention Contention Contention Contention Contention Contention Contention Contention Contention Active Piconets: Total Transmission Slots: Transmission Slots Hit: 112 Transmission Efficiency: ~89%

23 ...And Maintain Reasonable Performance Even In High Densities Piconet A Piconet B Piconet C Piconet D Piconet E Piconet F Piconet G Piconet H Piconet I Piconet J Piconet K Piconet L Piconet M Piconet N Piconet O Piconet P Piconet Q Piconet R Piconet S Piconet T Contention Contention Contention Contention Contention Contention Contention Contention Contention Contention Active Piconets: Total Transmission Slots: Transmission Slots Hit: 4 Transmission Efficiency: ~79%