Methods and systems are disclosed for performing seamless voice call handover and data handoff between a cellular network and a non-cellular (e.g., Wi-Fi) network, by a link budget limited user equipment device (UE) in standalone mode. The cellular radio may be maintained in a non-communication mode when not in use, to prevent power and peak power issues that may be unique to link budget limited devices. In response to poor non-cellular performance in support of a voice call, the UE may transition the cellular radio from the non-communication state to an online state. If the cellular network indicates that packet-switched calls are supported, then the UE may initiate handover of the voice call to the cellular network. Various methods for seamless handoff of data communications are also disclosed, in both the presence and the absence of a voice call. Various metrics are disclosed to enhance handoff determinations.