bluetooth

wireless personal area networks (WPANs) aka piconets (coverage < 10m diameter, no more than 8 dvices per piconet)

• 1 central role
• 7 peripheral roles

operates in unlicenseced ISM(industrial, scientific, medical) band: 2.4Ghz → a lot of interference BT device has unique 48-bit address

wireless ad hoc netowrk: no APs

→ the need for bluetooth

• is packed with many link-level networking technqieus:
  • time division multiplexing
  • frequestion division multiplexing
  • randomized backoff

channel allocation technqiues: frequency hoping → according to patterns

bluetooth stack

classic came before ble

• no layer 4 or layer 3
• no routing in classic BT(ble has managed flooding → multiple devices in a bluetooth network )

bluetooth packets

HCI packets : host controller interface packets

• host controller exchange HCI packets across internal interface

L2CAP similar to the transport layer

• createa of end-end L2CAP channels btw 2 devices (end-end network == no storage capabilities)
  • channes for E2E application/user data
  • reliability 1 bit (se number, acknowledgement) flow control, segmentation

channels types:

• connection oritented
• connectionless
• synchronous

is the sequence number here 1 bit ? same as tcp? (channel utilization)

• ack0, ack1
• when multiple packets are sent out simultaneously

bt link layer

• link manager
  • create, modify, release logical links
  • update PHY link parameters btw evices

• baseband resoruce manager

• link controller
  • encoding/ decodeing(up_ bt packets from data payload)

wireless channel 2.4-2.5 GHz ISM radio band - classic bt: 79 channles/frequencies - ble: 40 channels

• BT channel: TDM, 625 $\mu sec$ slot length
• channel access via ⇒ no collision btw networks → no collision btw bt devices
• frequency hopping
  • spread spectrum
  • stems from military’s idea
  • is there retransmission ????????
  • why 4g,5g not use frequency hopping???
• recovery mechanism at a higher layer

polling

• central sends packet to peripheral, peripheral responds
  • except
• interaction style :

creating BT network:

ad-hoc network:

scheduler?

5g fsm?