Initially the message frame comprising a header with length information, a data portion and a check sequence is expanded with gaps inserted to the data portion and the frame check sequence and the frame length information is updated, the frame is then scrambled and forward error correction data is generated and written into the gaps. An outer check sequence is generated and appended as part of the frame, after which the entire frame is transmitted. Error control decoding of the transmitted frame is achieved between reception and descrambling at a receiving device. The outer check sequence is optionally checked and removed, an error correction algorithm is applied to the frame in response to errors, after which the frame is descrambled, the forward error correction data and the inserted gaps are removed and the frame is restored to its original state and the length information is updated to its original value.