Bluetooth low energy - Devices go to deep sleep in transactions

Question

When I read the book about the Data Transactions,

It mentions that once the connection is made, both devices can go into deep sleep between transactions.

I dont quite understand how this could happen during the transaction. Can anyone explain this?

Thanks

Answer 1

A primary difference between Bluetooth and Bluetooth Low Energy is that the latter was not optimised for sending long data streams. In other words, Bluetooth Low Energy was optimised for sending blocks of data every "once in a while". The frequency of sending the data is application-dependent and can be modified by the user. For example, a BLE device can send a block of data (e.g. current temperature reading) once every five minutes, and then go to sleep (where there is very minimum power consumption) before waking up to send data again, and so on. This duty cycle is one of the main reasons of the Low Energy factor of BLE as opposed to traditional Bluetooth.

As you can see in the image above, BLE data transfer is in the form of data chucks, and the BLE device can go to sleep between the transmission of those chunks.

There are a couple of useful resources out there on the theoretical aspect of BLE, and I particularly found the following two useful:

• CSR: Bluetooth 4.0: Low Energy
• LitePoint: Bluetooth Low Energy

I hope that this helps.