A common uplink timing adjustment parameter value is estimated for UE transmissions in the multi-RAT communications network and provided for transmission to one or more UEs. That signaling parameter value is common to both the first and second RATs and useable by the one or more UEs to adjust transmit timing of uplink carriers belonging to the different RATs. The common timing adjustment parameter value may be provided, for example, in order to coordinate UE transmit timing of a first uplink carrier associated with the first RAT and of a second uplink carrier associated with the second RAT. A multi-RAT UE concurrently receives a first downlink carrier associated with the first RAT and a second different downlink carrier associated with the second RAT. The UE receives the common timing adjustment parameter value on one of those downlink carriers and adjusts a transmit timing of a first uplink carrier associated with the first RAT and of a second uplink carrier associated with the second RAT.