Methods, systems, and devices for wireless communications are described. A user equipment (UE) may identify that the UE is configured to use a two-step random access channel (RACH) procedure. The two-step RACH procedure may include an uplink request message and a downlink response. The UE may transmit the uplink request message as part of the two-step RACH procedure, and the uplink request message may include a preamble portion that is one of a set of predefined sequences and a payload portion that includes a physical uplink shared channel waveform. The UE may receive the downlink response as part of the two-step RACH procedure and in response to the uplink request message.