Coverage determination and switching between overlay communication systems

For coverage determination and system switching, a terminal obtains pilot strength estimates for base stations in first and second wireless communication systems (e.g., packet data system and voice/data system) and received signal quality estimates for at least one serving base station in the first system. The terminal derives various metrics based on the received signal quality estimates and pilot strength estimates. The terminal may perform handoff to the second system if weak coverage is detected for the first system, a received signal quality metric (Q) for the first system is below a Qth-dn threshold, and a pilot strength metric (V) for the second system exceeds a Vth-dn threshold. The terminal may perform handoff to the first system if good coverage is detected for this system, metric Q exceeds a Qth-up threshold, or a maximum pilot strength metric (M) for the first system exceeds a Mth-up threshold.