In a first subframe determined from a first number of hops up to a concentrator and being among a plurality of subframes included in a first frame period, a first wireless communication apparatus transmits first data, a second wireless communication apparatus transmits second data, and a third wireless communication apparatus receives the second data. In a second subframe determined from a second number of hops different from the first number of hops up to the concentrator and not corresponding to the first subframe among a plurality of subframes included in a second frame period following after the first frame period, the third wireless communication apparatus transmits the second data, and the third wireless communication apparatus does not transmit the second data in the first frame period.