A pico network node sends to a UE an allocation of physical downlink shared channel PDSCH subframes on the SCell. The allocation has control signaling indicating a number of the allocated PDSCH subframes that lie within a multiplexing window. The pico network node sends to the UE data on each of the allocated downlink subframes. The UE is also configured for a PCell with a macro network node not co-located with the pico. The UE determines from control signaling the number of PDSCH subframes that are allocated; and checks the determined number against PDSCH subframes it's received, to detect whether any allocated PDSCH subframe is missed. In an embodiment the control signaling is two bits per allocated downlink subframe as an assignment indication.