The invention relates to wireless network comprising an access point and non-AP stations. The station has traffic queues and associated a backoff counters which are decremented over time upon continuously sensing the medium as free during more than respective AIFS durations. To compensate additional opportunities provided by OFDMA RUs, a queue switches to an MU mode upon transmitting its data in an RU provided by the AP. To restore dynamicity of the backoff counters, frozen in the MU mode in the known techniques, embodiments provide the following at each expiry of one of the queue backoff counters: the current mode of the expiring traffic queue is determined; in case of legacy mode, the station accesses the channel to transmit data from the queue; whereas in case of MU mode, a new backoff value is drawn to reset the expiring backoff counter, without having data from the queue being transmitted.