Things to know about Bluetooth Low energy
- For BLE, specification limits the maximum transmit power to +10dBm.
- For BLE, specification limits the minimum transmit power to -20dBm.
- Receiver sensitivity means : how sensitive the radio is to detecting wireless transmissions from another device. This is measured in dBm and is very small number. The required sensitivity for BLE is -70 dBm i.e. it has to be able to pick up 0.0000001mW of electromagnetic energy to be able to work.
- When a peripheral device is advertising , central device which is active scanning will send SCAN_REQ and receive SCAN_RSP on advertising channels.
- To calculate the range of bluetooth, link budget of the system has to be calculated.
- The main contributor to the Link budget is path loss.
- Path loss is measure of how much the radio signal has reduced in power from Tx antenna to Rx antenna.
- path loss iss calculated as (only applicable to isotropic antennas):
- path loss = 40 + 25log(d)
- where d is the distance between transmitter and receiver.
