Some embodiments are directed to grouping electronic devices into contention groups to reduce uplink Orthogonal Frequency-Division Multiple Access (OFDMA) random access (OFDMA-RA) collisions. An access point may explicitly assign an electronic device to a contention group, or the electronic device may implicitly determine an assignment to the contention group. To explicitly assign a device to a contention group, the access point may randomly assign or assign based on a criteria of the electronic device. Examples of criteria include an association identifier (AID), a traffic type/quality of service (QoS) category, a power saving preference, and an association status. The electronic device may implicitly determine a contention group assignment based on the total number of contention groups. The electronic device may use the explicitly or implicitly assigned contention group number to determine whether the electronic device may contend for a given trigger frame random access (TF-R) frame.