A method performed by a first communications device for transmitting data to a second communications device on a sub-channel of a total system bandwidth of a communications network, wherein the total system bandwidth comprises two or more sub-channels, and wherein the method comprises: - performing carrier sensing on a first sub-channel assigned an unknown occupancy state, to determine whether the first sub-channel is vacant or occupied; - when the first sub-channel is determined as being vacant, - transmitting, to the second communications device, the data on the first sub-channel; the method further comprising: - when the first sub-channel is determined as being occupied, - assigning the first sub-channel an occupied state; - starting a first time period associated with the first sub-channel, during which first time period the first sub-channel is considered as being occupied; - performing carrier sensing on a second sub-channel assigned the unknown occupancy state, to determine whether the second sub-channel is vacant or occupied, and when the second sub-channel is determined as being vacant, transmitting, to the second communications device, the data on the second sub-channel; and - in the absence of the second sub-channel assigned the unknown occupancy state, entering an inactive mode until the first time period has expired. - performing carrier sensing on a first sub-channel assigned an unknown occupancy state, to determine whether the first sub-channel is vacant or occupied; - when the first sub-channel is determined as being vacant, - transmitting, to the second communications device, the data on the first sub-channel; the method further comprising: - when the first sub-channel is determined as being occupied, - assigning the first sub-channel an occupied state; - starting a first time period associated with the first sub-channel, during which first time period the first sub-channel is considered as being occupied; - performing carrier sensing on a second sub-channel assigned the unknown occupancy state, to determine whether the second sub-channel is vacant or occupied, and when the second sub-channel is determined as being vacant, transmitting, to the second communications device, the data on the second sub-channel; and - in the absence of the second sub-channel assigned the unknown occupancy state, entering an inactive mode until the first time period has expired. - transmitting, to the second communications device, the data on the first sub-channel; the method further comprising: - when the first sub-channel is determined as being occupied, - assigning the first sub-channel an occupied state; - starting a first time period associated with the first sub-channel, during which first time period the first sub-channel is considered as being occupied; - performing carrier sensing on a second sub-channel assigned the unknown occupancy state, to determine whether the second sub-channel is vacant or occupied, and when the second sub-channel is determined as being vacant, transmitting, to the second communications device, the data on the second sub-channel; and - in the absence of the second sub-channel assigned the unknown occupancy state, entering an inactive mode until the first time period has expired. - when the first sub-channel is determined as being occupied, - assigning the first sub-channel an occupied state; - starting a first time period associated with the first sub-channel, during which first time period the first sub-channel is considered as being occupied; - performing carrier sensing on a second sub-channel assigned the unknown occupancy state, to determine whether the second sub-channel is vacant or occupied, and when the second sub-channel is determined as being vacant, transmitting, to the second communications device, the data on the second sub-channel; and - in the absence of the second sub-channel assigned the unknown occupancy state, entering an inactive mode until the first time period has expired. - assigning the first sub-channel an occupied state; - starting a first time period associated with the first sub-channel, during which first time period the first sub-channel is considered as being occupied; - performing carrier sensing on a second sub-channel assigned the unknown occupancy state, to determine whether the second sub-channel is vacant or occupied, and when the second sub-channel is determined as being vacant, transmitting, to the second communications device, the data on the second sub-channel; and - in the absence of the second sub-channel assigned the unknown occupancy state, entering an inactive mode until the first time period has expired.