Piconets
Bluetooth devices connected in an “ad-hoc” cell.
There is a master with up to 7 active slaves and several hundreds parked.
Slaves only communicate with master.
Slaves must wait for permission from master.
Master defines radio parameters (”clock” and “deviceID”).
Channel, hopping sequence, timing, ...
Each piconet has an unique FH pattern (e and a single ID).
Each piconet has a maximum bandwidth (1MSPS).
A slave in one piconet can also be part of another piconet.
Either as a master or as a slave.
If master, it can create scatternets.
Operation
FH-SS: all devices must share the same hopping pattern:
Master provides clock and deviceID such that:
deviceID (48-bits) defines hopping pattern.
Clock defines phase inside the pattern.
If a device is inside a piconet, and is not connected, sb it must be in standby.
There are two types of piconet addresses (7+200...).
Active Member Address (AMA, 3-bits).
Parked Member Address (PMA, 8-bits).
Before setup
In operation
Device states
Standby
Waiting to join a piconet.
Inquire
Ask about radios to connect to (discover nodes).
Page
Connect to a specific radio.
Connected
Actively on a piconet (master or slave).
Park/Sniff/Hold
Low Power connected states.
Connection Procedure
General Inquiry Access Code (GIAC).
Dedicated Inquiry Access Code (DIAC).
Low-Power Operation in BT classic
3 modes:
Hold: node sleeps for specified interval.
Master can put slaves in hold while searching for new members, attending another piconet, etc.
No ACL packets (Asynchronous Connection-Less) -> general data packets.
(there is also Synchronous Connection Oriented -> Audio).
Sniff: slave low-duty cycle mode.
Slave wakes up periodically to talk to master.
Fixed “sniff” intervals.
Park:
Very low power state.
Used to admit more than 7 slaves in piconet.
Slave gives up its active member address.
Receives “parked” member address.
Wakes up periodically listening for broadcasts which can be used to “unpark” node.
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