A bio-medical unit includes a power harvesting module and an RF communication module. The power harvesting module generates a power supply voltage from the electromagnetic signal. The RF communication module interprets a predetermined pattern of the transmitting of the electromagnetic signal to determine null intervals； receives a downstream RF communication signal during at least one of the null intervals； converts the downstream RF communication signal into downstream information； converts upstream information into an upstream RF communication signal； and/or transmits the upstream RF communication signal during one or more of the null intervals.
