Piconets

Designating one device as master and networking it with slave device(s) forms a piconet. The maximum number of slave devices is restricted to seven in a piconet. The slaves follow the master's frequency hopping pattern. Also, the master allocates time slots to the slave devices by employing Time Division Multiplexing (TDM).

The transmission by slaves can take place either in synchronous mode or in asynchronous mode. In asynchronous mode, the slaves have to wait to be polled by the master. In synchronous mode, the slave transmits regularly in the allocated time slot.

The master controls the time slot allocation to each device based on the device's required data rate. The slaves communicate only with the Master. The limited area of coverage provided by piconets can be extended by the use of scatter nets formed by member(s) common to two or more piconets. However, a device cannot be a master in more than one piconet.

Drawbacks of Bluetooth standard

While the frequency hopping prevents loss of data due to interference to an extent, presence of unsynchronized piconets can lead to a great reduction in data rates. Data rates are reduced also by the overhead in encoding and frequency hopping.   In spite of the above and other shortcomings, Bluetooth is increasingly becoming popular in PANs.