A wireless transmitter transmits a plurality of data blocks defined in a transmission window for receipt by a receiver. The transmitter transmits a status request to the receiver for positive acknowledgement of successful receipt of the status request, the status request identifying a data block. The transmitter updates the transmission window upon receipt of a positive acknowledgement of receipt of a data block or upon receipt of a positive acknowledgement of receipt of a status request relating to a data block. The updating removes the record of the data block from the transmission window and adds a record of at least one different data block to the transmission window.