A method, along with corresponding devices (11 12) and a system (11 12), by which in-sequence delivery of data blocks, sent wirelessly by a sending terminal (11), is provided to a radio link control layer (12a) of a receiving terminal (12) by a media access control layer service (12b) of the receiving terminal (12), where the data blocks are communicated according to a protocol, such as WCDMA, in which a media access control layer (11b) of the sending terminal (11) includes as a service the transmission of the data blocks and possible retransmission of the same data blocks in response to ACK/NAK signaling by a corresponding service included in a media access control layer of the receiving terminal. No data block sequence number is used in the ACK/NAK signaling.