According to one aspect of the disclosure, a radio node for Time Division Duplex, TDD, communications is provided. The radio node includes processing circuitry configured to inject a signal into a time window where the time window is positioned, in a time domain, between a TDD first direction subframe to a TDD second direction subframe and the time window has a time duration less than the TDD first direction subframe and TDD second direction subframe, and perform at least one function using the injected signal.