A transmission apparatus (190, 1800) comprising: a transmitter which, in operation, transmits a Trigger Frame (510, 900) for allocating resources for Uplink Multi User, UL MU, transmission, the Trigger Frame comprising a common information field that includes a type subfield indicating one of a plurality of trigger types, and the Trigger Frame being for soliciting a UL MU response frame from a recipient terminal station wherein the plurality of trigger types includes a first trigger type indicating a basic trigger used for soliciting any type of the UL MU response frame from the recipient terminal station wherein the basic trigger does not impose a restriction on a response type of the solicited UL MU response frame, and a second trigger type indicating a specific trigger used for soliciting a specific type of the UL MU response frame from a plurality of terminal stations (110, 120, 130, 140, 150, 160,1900); and a receiver which, in operation, receives the specific type of UL MU response frame from the plurality of terminal stations when the type subfield indicates the second trigger type; characterized in that when the type subfield indicates the second trigger type, the Trigger Frame comprises a frame type subfield indicating a frame type, and a frame subtype subfield for further restricting the specific type of the UL MU response frame that is requested to each of the plurality of terminal stations, wherein the frame type is one of a management frame defined in IEEE 802.11 and a data frame; and when the frame type subfield indicates the frame type being the data frame, the frame subtype subfield indicates a traffic identifier, TID, of the data frame; and when the frame type subfield indicates the frame type being the management frame, the frame subtype subfield indicates a subtype of the management frame. a transmitter which, in operation, transmits a Trigger Frame (510, 900) for allocating resources for Uplink Multi User, UL MU, transmission, the Trigger Frame comprising a common information field that includes a type subfield indicating one of a plurality of trigger types, and the Trigger Frame being for soliciting a UL MU response frame from a recipient terminal station wherein the plurality of trigger types includes a first trigger type indicating a basic trigger used for soliciting any type of the UL MU response frame from the recipient terminal station wherein the basic trigger does not impose a restriction on a response type of the solicited UL MU response frame, and a second trigger type indicating a specific trigger used for soliciting a specific type of the UL MU response frame from a plurality of terminal stations (110, 120, 130, 140, 150, 160,1900); and a receiver which, in operation, receives the specific type of UL MU response frame from the plurality of terminal stations when the type subfield indicates the second trigger type; characterized in that when the type subfield indicates the second trigger type, the Trigger Frame comprises a frame type subfield indicating a frame type, and a frame subtype subfield for further restricting the specific type of the UL MU response frame that is requested to each of the plurality of terminal stations, wherein the frame type is one of a management frame defined in IEEE 802.11 and a data frame; and when the frame type subfield indicates the frame type being the data frame, the frame subtype subfield indicates a traffic identifier, TID, of the data frame; and when the frame type subfield indicates the frame type being the management frame, the frame subtype subfield indicates a subtype of the management frame.