Bluetooth

2.4 GHz - 2.485 GHz

BDR  1 Mb/s throughput.  Basic data rate.

Frequency-hopping spread spectrum.
1600 hops per second.
  Only hops between packet transfers.

79 channels

Each channel - 1 MHz. 1 Mb/s throughput.

A 'piconet' network consists of 
1 master and up to 7 active slave devices.
  Can register 255 devices, swapping active and inactive.


Devices may switch between the function of a master and a slave,
  provided it has sufficient logic.

  e.g Wireless headset functions as master to couple with a cell phone (slave).
  Once connection completed, switches roles with cell phone.

A device may interact/connect with/to more than on piconet, establishing
a 'scatternet'. Device may fill different roles in different piconets.

Packet based transfer.

  Packets broken up into slots.

  1, 3, or 5 slots per packet transfer.
  Frequency hop only occurs between completed packet transfers.

  312.5 us clock generated by master.
  2 clocks per slot.

  Slots paired.
  Even slots used by master to transmit.
  Odd slots used by each of the 7 slave devices.
  Odd slot use distributed round robin to each possible active slave,
    whether used/existing or not. 

BDR - 64Kb/s maximum transfer - OK for audio.

EDR - extended data transfer. (Bluetooth 2.0)

  After 'header' information of initial slot of packet sent, if EDR 
  mode supported, switches to phase-keyed modulation combined with 
  frequency-keyed modulation. 

  Capable of doubling the rate of actual data transmission.

BLE - Bluetooth Low Energy. (Bluetooth 4)

  Alternative protocol.

  Lower data transfer rate.

  Much lower power draw.

  Commonly used in medical/fitness fields to link measurement devices
  to monitors.


3 transfer modes.

  Asynchronous Connection-Less (ACL)
    Lossless data transmission 
    - provides for retransmission of lost/corrupted packets.

    Suports encryption between master and each slave.

    Only one channel per device.

    Data transfer rate variable.

  Synchronous Connection-Oriented (SCO)
    Reserved time slot.
    No retransmission
    Does use Forward Error Correction.
      Allowing for recovery from some transmisson errors.
    1 slot in length
    No acknowledgement.
    Data transfer 64Kbit/s 

    Master may support up to 3 SCO connections (channels),
      may be to same slave.

  Enhanced Synchronous Connection-Oriented (eSCO)
    Allows retransmission 
      possibly by delaying transmission.