Currently IWR6843 supports only BPM per the post below.
IWR6843 datasheet says
6.3.1 RF and Analog Subsystem
The RF and analog subsystem includes the RF and analog circuitry – namely, the synthesizer, PA, LNA,
mixer, IF, and ADC. This subsystem also includes the crystal oscillator and temperature sensors. The
three transmit channels can be operated up to a maximum of two at a time (simultaneously) for transmit
beamforming purpose as required; whereas the four receive channels can all be operated simultaneously.
Does this means BPM for 3 TX is not supported?