A method by a wireless transmitting device is disclosed for indicating a partial traffic identifier (PTID) or an access category index (ACI) in a header compression element. The method includes generating a frame that includes the header compression element, wherein the header compression element includes a first subfield that is for indicating a PTID of a quality of service (QoS) data frame or an ACI of a QoS management frame and a second subfield indicating whether the first subfield indicates the PTID of the QoS data frame or the ACI of the QoS management frame. The method further includes transmitting the frame through a wireless medium.