A method of operating a station (STA) in a communications network is disclosed. A set of access categories of the STA that are enabled for unscheduled automatic power save delivery (U-APSD) are identified. Specifically, each access category in the set of access categories is associated with one or more user priority values. A lowest-priority access category is determined among the set of access categories. Specifically, the lowest-priority access category is associated with the lowest user priority value among the set of access categories. A trigger frame associated with the lowest-priority access category is then transmitted to an access point (AP) to initiate a first unscheduled service period with the AP.