Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a user equipment (UE) may receive, from a base station, a random access channel (RACH) occasion (RO) configuration that includes information related to ordered preamble resources. The UE may generate a preamble resource index according to various parameters selected based on the RO configuration information that relates to the ordered preamble resources. The UE may generate an uplink RACH message that includes a preamble based at least in part on the preamble resource index and a payload associated with a physical uplink shared channel (PUSCH) resource unit (PRU) mapped to the preamble resource index. After decoding the uplink RACH message, the base station may send a response message including scrambled downlink control information (e.g., based on a scrambling identifier or payload information associated with the uplink RACH message). Numerous other aspects are provided.