A first device for wireless communication, the first device comprising: a transceiver (21_4); and processing circuitry (21_1) configured to: negotiate (S71a, S71b, S91a, S91b) a buffer size with a second device via the transceiver (21_4), wherein a predetermined maximum block acknowledgement bitmap subfield length is associated corresponding to the range of the negotiated buffer size; determine (S72a, S72b, S92a, S92b) an upper bound of the length of the block acknowledgement bitmap subfield based on a size of data to be transmitted, wherein the upper bound is equal to or less than the maximum block acknowledgement bitmap subfield length; set (S73a, S73b, S93a, S93b) a duration field based on the determined upper bound, or a subfield defining the upper bound thereby explicitly limiting the block acknowledgement bitmap subfield length; transmit (S74a, S74b, S94a, S94b) the data and including in the data at least one of the duration field (31_1) or the subfield to the second device via the transceiver (21_4); and receive (S76a, S76b, S97a, S97b) a first block acknowledgement from the second device via the transceiver (21_4), the first block acknowledgement comprising a first block acknowledgement bitmap. a transceiver (21_4); and processing circuitry (21_1) configured to: negotiate (S71a, S71b, S91a, S91b) a buffer size with a second device via the transceiver (21_4), wherein a predetermined maximum block acknowledgement bitmap subfield length is associated corresponding to the range of the negotiated buffer size; determine (S72a, S72b, S92a, S92b) an upper bound of the length of the block acknowledgement bitmap subfield based on a size of data to be transmitted, wherein the upper bound is equal to or less than the maximum block acknowledgement bitmap subfield length; set (S73a, S73b, S93a, S93b) a duration field based on the determined upper bound, or a subfield defining the upper bound thereby explicitly limiting the block acknowledgement bitmap subfield length; transmit (S74a, S74b, S94a, S94b) the data and including in the data at least one of the duration field (31_1) or the subfield to the second device via the transceiver (21_4); and receive (S76a, S76b, S97a, S97b) a first block acknowledgement from the second device via the transceiver (21_4), the first block acknowledgement comprising a first block acknowledgement bitmap. negotiate (S71a, S71b, S91a, S91b) a buffer size with a second device via the transceiver (21_4), wherein a predetermined maximum block acknowledgement bitmap subfield length is associated corresponding to the range of the negotiated buffer size; determine (S72a, S72b, S92a, S92b) an upper bound of the length of the block acknowledgement bitmap subfield based on a size of data to be transmitted, wherein the upper bound is equal to or less than the maximum block acknowledgement bitmap subfield length; set (S73a, S73b, S93a, S93b) a duration field based on the determined upper bound, or a subfield defining the upper bound thereby explicitly limiting the block acknowledgement bitmap subfield length; transmit (S74a, S74b, S94a, S94b) the data and including in the data at least one of the duration field (31_1) or the subfield to the second device via the transceiver (21_4); and receive (S76a, S76b, S97a, S97b) a first block acknowledgement from the second device via the transceiver (21_4), the first block acknowledgement comprising a first block acknowledgement bitmap. <EOS>