Apparatuses, systems, and methods for a wireless device to perform simultaneous uplink activity for multiple RATs in the same carrier using multiplexing at a layer above the physical layer. The wireless device may establish wireless links with first and second base stations, respectively, according to first and second radio access technologies (RATs), respectively. The first base station may provide a first cell operating in a first system bandwidth and the second base station may provide a second cell operating in a second system bandwidth. The wireless device may determine whether inter-RAT uplink coexistence in the same frequency band is enabled. If so, the wireless device may perform uplink activity for both the first RAT and the second RAT in the first system bandwidth by multiplexing uplink data for the first RAT and uplink data for the second RAT at a layer above the physical layer.