Park Mode

When a slave decides to remain inactive in the piconet for a period of time that is comparatively longer than the Sniff and Hold periods, it enters Park mode. The device maintains its synchronization in the piconet while remaining uninvolved in the traffic. In order to re-synchronize, parked devices surrender their MAC (AM_ADDR address) and occasionally listen to broadcast messages from the master. Of the three power-saving modes, it offers the highest power efficiency. Devices that occasionally need to communicate with a Master can be accommodated in park mode. Following a periodic beacon sent by the Master, a Slave exits Park mode by sending a packet to the Master requesting a transition from Park to Active mode. The beacon interval is programmable. Since parked members give up their MAC addresses, each of them is given two additional addresses to help Master keep track of them.

• PM_ADDR: Parked Member Address is an 8-bit long Master-local address used for the identification of parked slaves. The PM_ADDR is valid as long as the slave is parked. PM_ADDR being 8-bits long, allows as many as 256 devices to exist simultaneously in Park mode in a single piconet.
• AR_ADDR: Access Request Address is also an 8-bit long address that is used by parked slaves to determine the Slave-to-Master half slot within the access window in which it can transmit an access request

Bluetooth is a technology that almost every device is using in today’s world, it was the most popular and safe way of sharing data in the early times. Bluetooth uses a short-range wireless technology standard that is used for exchanging data between fixed and mobile devices over short distances and building personal area networks. Bluetooth holds a transmission limit of up to 2.5 milliwatts, the reason for its short-range transmission.
The state of any given Bluetooth unit (having a required power supply) can broadly be categorized as standby or connection. A device in standby state is not active in any network. A Bluetooth-enabled device in the connection state is synchronized to a piconet. Such a device can be in one of the following four modes:

• Active mode.
• Sniff mode.
• Hold mode.
• Park mode.