Orthogonal frequency division multiple access communication apparatus and communication method

1. An integrated circuit to control a process of a communication apparatus that is a 20 MHz operating station, the integrated circuit comprising:

at least one input, which, in operation, receives an input; and

control circuitry coupled to the at least one input, which, in operation, controls the process comprising:

receiving a Trigger frame for allocating resource units (RU(s)) for random access and another frame including a Random Access parameter element that comprises a first field indicating an OFDMA contention window (OCW) minimum value (OCWmin), wherein the RU(s) include at least one RU that is restricted from being used for the 20 MHz operating station; and

controlling an Uplink OFDMA-based Random Access (UORA) procedure using the OCWmin, the UORA procedure including:

setting an OFDMA Back-Off (OBO) counter to zero in a case where when the OBO counter is not greater than a number of available RU(s) for random access in the Trigger frame, the available RU(s) being RU(s) unrestricted from being used for the 20 MHz operating station; and

decrementing the OBO counter by the number of the available RU(s) for random access in a case where the OBO counter is greater than the number of available RU(s) for random access.

2. The integrated circuit according to claim 1 , wherein the another frame is one of a Beacon frame and a Probe response frame.

3. The integrated circuit according to claim 1 , wherein the communication apparatus only operates with 20 MHz channel width.

4. The integrated circuit according to claim 1 , wherein the Random Access parameter element comprises a second field indicating an OCW maximum value (OCWmax), and the process includes:

setting an OCW value within a range of the OCWmin and the OCWmax; and

initializing the OBO counter to an integer value in a range of 0 and the OCW value.

5. The integrated circuit according to claim 1 , wherein

a recipient of the Trigger frame is a station apparatus operating on a primary 20 MHz channel bandwidth; and

the available RU(s) for random access are RU(s) unrestricted from being used for the station apparatus within the primary 20 MHz channel bandwidth.

6. The integrated circuit according to claim 1 , wherein

a recipient of the Trigger frame is a 20 MHz only non-Access Point station apparatus operating on a 20 MHz channel bandwidth.

7. The integrated circuit according to claim 1 , wherein

the Trigger frame comprises a common information field and a plurality of user information fields, each of the plurality of user information fields including an identifier subfield and an RU allocation subfield that indicates an RU used for uplink data transmission by a station apparatus identified by the identifier subfield.