In a wireless communications network, access points and connected mobile devices transmit data via a radio frequency spectrum channel. When a device has packets for transmission it must check the channel is available before it can transmit the data. Furthermore there is a Transmission Opportunity (TXOP) parameter which limits the maximum amount of time that a device can transmit packets before it must relinquish the channel so that other devices are not locked out. Each device in the network is capable of updating its own TXOP parameters in order to respond to changes in the level of interference and contention in the surrounding area. In this way devices can transmit for longer periods of time when contention is low, while responding to increased network contention by shortening the TXOP to ensure fair access for all other devices in the network.