蓝牙协议栈

benben3956

               

• 
  The radio layer is the physical wireless connection. To avoid interference with other devices that communicate in the ISM band,
  the modulation is based on fast frequency hopping. Bluetooth divides
  the 2.4 GHz frequency band into 79 channels 1 MHz apart (from 2.402 to
  2.480 GHz), and uses this spread spectrum to hop from one channel to
  another, up to 1600 times a second. The standard wavelength range is 10
  cm to 10 m, and can be extended to 100 m by increasing transmission
  power.
  
• 
  The baseband layer is responsible for
  controlling and sending data packets over the radio link. It provides
  transmission channels for both data and voice. The baseband layer
  maintains Synchronous Connection-Oriented (SCO) links for voice and
  Asynchronous Connectionless (ACL) links for data. SCO packets are never
  retransmitted but ACL packets are, to ensure data integrity.
  SCO links are point-to-point
  symmetric connections, where time slots are reserved to guarantee
  timely transmission. A slave device is allowed to respond during the
  time slot immediately following an SCO transmission from the master. A
  master can support up to three SCO links to a single slave or to
  multiple slaves, and a single slave can support up to two SCO links to
  different slaves.
  Data transmissions on ACL links, on the other hand, are established on a
  per-slot basis (using slots not reserved for SCO links). ACL links
  support point-to-multipoint transmissions. After an ACL transmission
  from the master, only a slave addressed specifically may respond during
  the next time slot; if no device is addressed, the message is treated
  as a broadcast.
  
• 
  The Link Manager Protocol (LMP)
  uses the links set up by the baseband to establish connections and
  manage piconets. Responsibilities of the LMP also include
  authentication and security services, and monitoring of service quality.
  
• 
  The Host Controller Interface (HCI) is
  the dividing line between software and hardware. The L2CAP and layers
  above it are currently implemented in software, and the LMP and lower
  layers are in hardware. The HCI is the driver interface for the
  physical bus that connects these two components. The HCI may not be
  required. The L2CAP may be accessed directly by the application, or
  through certain support protocols provided to ease the burden on
  application programmers.
  
• 
  The Logical Link Control and Adaptation Protocol (L2CAP)
  receives application data and adapts it to the Bluetooth format. Quality
  of Service (QoS) parameters are exchanged at this layer.
  

Basically, the layers above HCI is implemented in software while LMP,baseband and radio layers are provided by bluetooth modules.
               
               
               
               
               

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