Systems and methods for determining a mapping that associates a plurality of preambles to a plurality of channel resource units used to carry a plurality of payloads associated with the plurality of preambles, including but not limited to, determining that the plurality of channel resource units is carrying the plurality of payloads, determining that a set of preambles of the plurality of preambles is associated with a same beam, and prioritizing mapping the set of preambles to reference signals of the plurality of channel resource units corresponding to different code division multiplexing (CDM) groups.