A user equipment (UE) comprises a radio having TX and RX paths that include a duplexer, thus facilitating a full-duplex mode. The radio may also have TX and RX paths that exclude the duplexer, and which thus facilitate a half-duplex mode. The UE may be configured to autonomously and opportunistically switch from the full-duplex mode (the paths that include the duplexer) to the half-duplex mode (the paths that exclude the duplexer) when the UE desires to avoid the path loss caused by the duplexer, e.g., to temporarily receive with greater sensitivity and/or transmit with more power, during poor channel conditions. At other times the UE may autonomously decide to remain in full-duplex mode to achieve reduced transmission time, e.g., during time-critical communications such as VoLTE. The UE may autonomously determine whether to use full or half-duplex mode, i.e., without requiring any coordination with network-side devices.