Methods, systems, and devices for wireless communications are described. A communication device, such as a user equipment (UE) may transmit a message to a base station (e.g., a NodeB, an eNodeB (eNB), a next-generation NodeB or a giga-NodeB (either of which may be referred to as a gNB)) in wireless communications with the UE. The message may include a UE capability to append a preamble waveform to an uplink transmission to the base station. In some examples, a preamble waveform may include a Wi-Fi preamble or a new radio unlicensed (NR-U) preamble. Based on the UE capability, the base station may determine and transmit a preamble configuration to the UE, which the UE may use to generate and append a preamble waveform to another message for an uplink transmission to the base station.