A first communication apparatus configured to operate as an Access Point, AP, and wirelessly communicate with a plurality of second communication apparatuses based on IEEE802.11 standard, the first communication apparatus comprising: a communication unit configured to - transmit a first trigger frame to the plurality of second communication apparatuses to request each of the plurality of second communication apparatuses to transmit a first frame; - receive the first frames from the plurality of second communication apparatuses in response to the transmitted first trigger frame, wherein the received first frame includes transmission data amount information for each of the plurality of second communication apparatuses; - transmit a second trigger frame to the plurality of second communication apparatuses, wherein the second trigger frame is generated based on the first frame and is a trigger for transmission of uplink data frames from the plurality of second communication apparatuses and the second trigger frame includes: identification information that indicates the plurality of second communication apparatuses which are destinations of the second trigger frame, transmission information related to a first transmission time period for the plurality of second communication apparatuses to transmit the uplink data frames, subcarrier information related to an allocated subcarrier for each of the plurality of second communication apparatuses to transmit each of the uplink data frames, and power information related to a transmission power for each of the plurality of second communication apparatuses to transmit each of the uplink data frames; and - receive data frames from the plurality of second communication apparatuses, wherein the uplink data frames are transmitted by the plurality of second communication apparatuses in response to the second trigger frame, based on the identification information, the transmission information, subcarrier information and the power information, and the first transmission time period is determined based on a maximum value of the transmission data amount information included in the first frames. a communication unit configured to - transmit a first trigger frame to the plurality of second communication apparatuses to request each of the plurality of second communication apparatuses to transmit a first frame; - receive the first frames from the plurality of second communication apparatuses in response to the transmitted first trigger frame, wherein the received first frame includes transmission data amount information for each of the plurality of second communication apparatuses; - transmit a second trigger frame to the plurality of second communication apparatuses, - transmit a first trigger frame to the plurality of second communication apparatuses to request each of the plurality of second communication apparatuses to transmit a first frame; - receive the first frames from the plurality of second communication apparatuses in response to the transmitted first trigger frame, wherein the received first frame includes transmission data amount information for each of the plurality of second communication apparatuses; - transmit a second trigger frame to the plurality of second communication apparatuses, wherein the second trigger frame is generated based on the first frame and is a trigger for transmission of uplink data frames from the plurality of second communication apparatuses and the second trigger frame includes: identification information that indicates the plurality of second communication apparatuses which are destinations of the second trigger frame, transmission information related to a first transmission time period for the plurality of second communication apparatuses to transmit the uplink data frames, subcarrier information related to an allocated subcarrier for each of the plurality of second communication apparatuses to transmit each of the uplink data frames, and power information related to a transmission power for each of the plurality of second communication apparatuses to transmit each of the uplink data frames; and - receive data frames from the plurality of second communication apparatuses, identification information that indicates the plurality of second communication apparatuses which are destinations of the second trigger frame, transmission information related to a first transmission time period for the plurality of second communication apparatuses to transmit the uplink data frames, subcarrier information related to an allocated subcarrier for each of the plurality of second communication apparatuses to transmit each of the uplink data frames, and power information related to a transmission power for each of the plurality of second communication apparatuses to transmit each of the uplink data frames; and - receive data frames from the plurality of second communication apparatuses, wherein the uplink data frames are transmitted by the plurality of second communication apparatuses in response to the second trigger frame, based on the identification information, the transmission information, subcarrier information and the power information, and the first transmission time period is determined based on a maximum value of the transmission data amount information included in the first frames.