RE: Antenna Diversity questions

Kenneth — Tue, 30 Apr 2024 13:14:38 GMT

Hello,

There is an antenna diversity example for 802.15.4:
https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrfxlib/nrf_802154/doc/antenna_diversity.html

We don't have a similar example for other protocols. The reason is really because the 802.15.4 have a very long pre-amble. This allows you to sample the pre-amble with both antennas and decide during the pre-amble which has the best signal strength and used this. This can be done for every packet received. Bluetooth has a very short pre-amble so you can't change antenna during the packet reception so you can only switch antenna in between packets -> moving the antenna diversity out of the controller and onto the application space. You would then have to run something to a QoS service on the antennas and then switch antennas based on the QoS of each. This is not something we have.

Another complicating factor for Bluetooth (and other short pre-amble protocols): if you receive from multiple transmitters you will need to run a separate QoS algorithm for each transmitter. This is not the case if you have long pre-amble as you can do it per packet.

Also have in mind, for Bluetooth you are also frequency hopping, so the deep "nulls" will be different on each frequency. Antenna diversity is primarily useful if you have two stationary devices communicating on a single frequency; if you are moving or frequency-hopping, you might as well retransmit as change antennas.

Kenneth