Post on 30-Jun-2020
transcript
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Host Controller Interface
Inside Bluetooth
RF (radio and antenna)
Audi
o (S
CO)
Cont
rol
Audi
o(S
CO)
Con
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L2CAP
BasebandLink Manager
Transport Interface
ApplicationRFCOMM SDP
Data (ACL)
Data (ACL)Host
Blue
toot
hM
odul
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Transport Bus
Host Application
API and Legacy Support Modules
Bluetooth HCI Driver
Physical I/F
Physical I/F
HCI Firmware
Logical Link Control & Data Adaptation
Physical Link Control
Data Processing & Transmission Mgmt.
Transmission/Reception
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L2CAP Logical Link Control and Adaptation Protocol
w Manages the creation and termination of virtualconnections with other Bluetooth devices— Negotiates and/or dictates parameters
– Including Security and Quality of Service (QoS)
w Manages ACL data flow between the host and LinkManager— Multiplixing of multiple concurrent host I/O operations— Segmentation And Reassembly (SAR) of various data
formats for baseband compatibility
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Link Manager
w Physically manages creation, configuration, andtermination of device to device links
w Also manages ACL data flow between the L2CAPand 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
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Baseband
w Performs all digital data processing operations— Speech coding— Data whitening— Optional encryption/decryption— Packetization— Header and payload error detection and correction
w Calculates and controls transmission frequency— Supporting Bluetooth’s 80 channel Frequency
Hopping (FH) spread spectrum transmission method
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How Does Bluetooth Work?
Master
Active Slave
Parked Slave*
Standby*
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Operational States
* Low power state
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In the Beginningw Initially Bluetooth devices only know about themselves
— Everyone passively monitors in Standby mode— No devices are synchronized
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InquiryDiscovering Who’s Out There
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w Inquiry discovers what other devices within range
10 meters
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PagingCreating a Piconet
w Paging creates a Master/Slave link called a Piconet
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10 meters
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Expanding a Piconet (1)w Successive Pages can attach up to 7 Active Slaves to a
Piconet at one time
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10 meters
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Parkingw To save power and/or to connect to even more devices
Active Slaves can be Parked (up to 256 total!)
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10 meters
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Expanding a Piconet (2)w Masters can then attach additional Active Slaves using
Active Member Addresses freed up through Parking
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10 meters
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Scatternets
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w Bluetooth devices can participate in multiple Piconetssimultaneously creating a topologies called Scatternets
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Advanced Scatternets
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w Scatternets can evolve into extremely complex structurescreating a rich fabric of many, many, devices
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Bluetooth Radio Basics
w Normal range: 10 meters
w Normal xmit power: 1 milliWatt
w Receiver sensitivity: -70 dB
w Frequency band: 2.4 GHz(ISM)
w Max data rate: 721Kbps + 56Kbps X 3 (voice)
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Bluetooth Radio Frequency Band
w ISM (Industrial, Scientific, Medical) band— 2.402GHz - 2.480GHz (79MHz total bandwidth)
w Advantages— Free— Open to everyone worldwide
w Disadvantages— Noise sources from everywhere
– Cordless phones, microwave ovens, garage door openers,other wireless LAN technologies, baby monitors,...
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Bluetooth’s Noise Solutions
w Frequency Hopping (FH) Spread Spectrumtechnology— Divides the band into 79 separate 1MHz channels
w Uses short packets and makes 1600 hops/second— Minimizes exposure to noisy channels— Enables bad voice packets to be discarded
w Forward Error Correction (FEC) of data packets— Data often recoverable even on a noisy channel
without retransmission
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Bluetooth Transmission ProtocolFrequency Hopping & Time Division Duplexing
fk+2
625 µsSlot 3
fk+3
Frame 2
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w Frequency hops from Slot to Slot to Slotw Frames define matched Master / Slave Slot transmissions
fk+1
Frame 1
Slot2
w Complete packet transmission occurs during a Slot
Master
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fk
625 µsSlot 1
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Piconet A Contention
Total Transmission Slots: 100 Transmission Slots Hit: 0 Transmission Efficiency: ~100%Active Piconets: 1
Frequency HoppingGraphically Illustrated
Transmission Channel (1 - 79)
Transmission Slot (time)
Each channel can carry a separateBluetooth transmission without contention
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Piconet A Contention
Total Transmission Slots: 100 Transmission Slots Hit: 0 Transmission Efficiency: ~100%Active Piconets: 1
Each Bluetooth Piconet RandomlyChanges Frequency Slot by Slot by Slot
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Piconet A Contention
Total Transmission Slots: 100 Transmission Slots Hit: 0 Transmission Efficiency: ~100%Active Piconets: 1
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Piconet A Contention
Total Transmission Slots: 100 Transmission Slots Hit: 0 Transmission Efficiency: ~100%Active Piconets: 1
Frequency Hopping Minimizes Exposureto Data Loss Due to Noise
7 ~93%
5MHz noise source
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Piconet A Contention
Total Transmission Slots: 100 Transmission Slots Hit: 0 Transmission Efficiency: ~100%Active Piconets: 1 7 ~93%
5MHz noise source
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Frequency Hopping WithMultiple Piconets
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Piconet A Piconet B Piconet C Piconet D Contention Contention Contention Contention
Total Transmission Slots: 400 Transmission Slots Hit: 20 Transmission Efficiency: ~95%Active Piconets: 4
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Bluetooth Piconets DegradeGracefully with Density...
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Piconet A Piconet B Piconet C Piconet D Piconet E Piconet F Piconet G Piconet H Piconet I Piconet JContention Contention Contention Contention Contention Contention Contention Contention Contention Contention
Total Transmission Slots: 1000 Transmission Slots Hit: 112 Transmission Efficiency: ~89%Active Piconets: 10
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...And Maintain ReasonablePerformance Even In High Densities
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Piconet A Piconet B Piconet C Piconet D Piconet E Piconet F Piconet G Piconet H Piconet I Piconet JPiconet K Piconet L Piconet M Piconet N Piconet O Piconet P Piconet Q Piconet R Piconet S Piconet TContention Contention Contention Contention Contention Contention Contention Contention Contention Contention
Total Transmission Slots: 2000 Transmission Slots Hit: 420 Transmission Efficiency: ~79%Active Piconets: 20