An apparatus (104, 106, 108, 110, 112) of transmitting node, the apparatus (104, 106, 108, 110, 112) comprising: one or more antenna (305a, 305b, 305n) configured to communicate data; and processing circuitry (315, 320) configured to: establish a negotiated data transmission bandwidth using at least one of one or more free channels determined within a data transmission bandwidth comprising multiple aggregated channels; transmit, to a receiving node, a request to send, RTS, message comprising a first bitmap configured to indicate that a portion of the data transmission bandwidth comprising the multiple aggregated channels is available to be used for transmission, wherein the portion comprises at least one channel of the multiple aggregated channels and/or at least one channel segment included in the multiple aggregated channels; and receive, from the receiving node, a clear to send, CTS, message comprising a second bitmap configured to indicate that a subset of the portion of the data transmission bandwidth indicated by the RTS message is available to be used for the transmission, wherein the subset comprises at least one channel included in the portion and/or at least one channel segment included in the portion, wherein a number of bits for the first bitmap is determined based on the data transmission bandwidth comprising the multiple aggregated channels, and wherein a number of bits for the second bitmap is determined based on the portion of the data transmission bandwidth indicated by the RTS message. one or more antenna (305a, 305b, 305n) configured to communicate data; and processing circuitry (315, 320) configured to: establish a negotiated data transmission bandwidth using at least one of one or more free channels determined within a data transmission bandwidth comprising multiple aggregated channels; transmit, to a receiving node, a request to send, RTS, message comprising a first bitmap configured to indicate that a portion of the data transmission bandwidth comprising the multiple aggregated channels is available to be used for transmission, wherein the portion comprises at least one channel of the multiple aggregated channels and/or at least one channel segment included in the multiple aggregated channels; and receive, from the receiving node, a clear to send, CTS, message comprising a second bitmap configured to indicate that a subset of the portion of the data transmission bandwidth indicated by the RTS message is available to be used for the transmission, wherein the subset comprises at least one channel included in the portion and/or at least one channel segment included in the portion, establish a negotiated data transmission bandwidth using at least one of one or more free channels determined within a data transmission bandwidth comprising multiple aggregated channels; transmit, to a receiving node, a request to send, RTS, message comprising a first bitmap configured to indicate that a portion of the data transmission bandwidth comprising the multiple aggregated channels is available to be used for transmission, wherein the portion comprises at least one channel of the multiple aggregated channels and/or at least one channel segment included in the multiple aggregated channels; and receive, from the receiving node, a clear to send, CTS, message comprising a second bitmap configured to indicate that a subset of the portion of the data transmission bandwidth indicated by the RTS message is available to be used for the transmission, wherein the subset comprises at least one channel included in the portion and/or at least one channel segment included in the portion, wherein a number of bits for the first bitmap is determined based on the data transmission bandwidth comprising the multiple aggregated channels, and wherein a number of bits for the second bitmap is determined based on the portion of the data transmission bandwidth indicated by the RTS message.