Methods, systems, and devices for wireless communications are described in which sequence groups, and sequence hopping patterns may be used to distinguish concurrent non-orthogonal multiple access (NOMA) transmissions. A wireless device, such as a user equipment (UE), may identify, for a message, a first transmission opportunity from a plurality of transmission opportunities associated with grant-free uplink contention-based transmissions (e.g., NOMA transmissions); select a multiple access (MA) signature sequence from a group of MA signature sequences associated with the first transmission opportunity; identify a hopping pattern associated with the MA signature sequence; and transmit one or more redundancy versions of the message in one or more of the plurality of transmission opportunities comprising the first transmission opportunity according to the MA signature sequence and the hopping pattern.