1. A wireless communication apparatus which communicates with one or more wireless station apparatuses by utilizing an enhanced distributed channel access (EDCA) mechanism, comprising: first channel state determining circuitry, which, in operation, determines, per time unit, a usage state of a communication channel which is used between the wireless communication apparatus and the one or more wireless station apparatuses in a contention period of the communication channel, in a situation where the wireless communication apparatus communicates with the one or more wireless station apparatuses, based on a usage by the wireless communication apparatus, a usage by the one or more wireless station apparatuses and an idling state; first terminal occupation time calculating circuitry, which, in operation, classifies, on the basis of the usage state, the contention period of the communication channel into a self-terminal occupation time used by the wireless communication apparatus, a different-terminal occupation time used by one of the one or more wireless station apparatuses, and an idle time, and calculates, on the basis of the usage state, a different-terminal occupation time used by one of the one or more wireless station apparatuses in the contention period of the communication channel; first traffic measuring circuitry, which, in operation, measures an amount of data received from the wireless station apparatus in the different-terminal occupation time; first parameter adjusting circuitry, which, in operation, adjusts an EDCA parameter set used in the EDCA mechanism, on the basis of the different-terminal occupation time and the amount of data received from the one or more wireless station apparatuses; parameter updating circuitry, which, in operation, updates the EDCA parameter set to an adjusted EDCA parameter set; feedback receiving circuitry, which, in operation, receives feedback information including information indicating a different-terminal occupation time and an amount of received data measured by the one or more wireless station apparatuses; and second parameter adjusting circuitry, which, in operation, adjusts the EDCA parameter set, on the basis of the different-terminal occupation time and the amount of received data indicated by the feedback information.