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Number of Devices within a Piconet
Original Post: devices / piconet (SIG Forum & eGroups Msg.)
Date: 2000-07-11
One misconception is that the Bluetooth spec allows
for a total of 8 devices (1 master plus 7 slaves) per piconet, and that
this is a direct limitation of the 3 bit address field (AM_ADDR)
This is partly incorrect. The limitation is 7 ACTIVE
slaves per piconet. There can be any number of parked slaves in a piconet
(up to 255 that are directly addressable by a parked slave address, but
even more
addressable by their BD_ADDR). The master can "swap out" active
slaves for parked slaves to manage piconets for situations that require a
large number of connected devices, such as providing data services to
people in hi-population areas such as airports
And there is also a practical limitation on the number
of devices that can be in a piconet, which influenced the design of
piconet architecture. When you consider the short range of Bluetooth
wireless communication, it would seem unusual to have many, many devices
all within range of each other in a piconet. It would have caused too much
demand on the master to service the requests of more than 7 active
devices,also throughput to an individual slave would be reduced to very
low levels if too many active slaves existed
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