Abstract: A data transmitter divides incoming data for transmission into data blocks and passes them in frame transmission order to a radio link stage via a serial frame buffer. The buffer holds the data frames until the radio link stage is able to transmit them. The incoming data has associated with it various parameters. The radio link stage has allocated to it radio link resources. The parameters and resources, which change independently of each other from time to time, are supplied to a controller which calculates high and low buffer levels therefrom. The controller controls the passing of the data frames through the frame buffer to maintain the number of frames in the buffer at any instant of time at a level between the calculated high and low levels.

Abstract: A data transmitter (10) divides incoming data for transmission into data blocks and passes them in frame transmission order to a radio link stage (16) via a serial frame buffer (14). The buffer (14) holds the data frames until the radio link stage (16) is able to transmit them. The incoming data has associated with it various parameters. The radio link stage (16) has allocated to it radio link resources. The parameters and resources, which change independently of each other from time to time, are supplied to a controller (18) which calculates high and low buffer levels therefrom. The controller (18) controls the passing of the data frames through the frame buffer (14) to maintain the number of frames in the buffer at any instant of time at a level between the calculated high and low levels.

Abstract: A data transfer procedure enables data of a data sequence to be transferred between a transmitting entity (13) and a receiving entity (19). The entities each comprise a higher data handling layer (11, 17) and a lower data handling layer (12, 18). The procedure comprises transferring down from the higher data handling layer (11) of the transmitting entity (13) to the lower data handling layer (12) of the transmitting entity a data unit of the data sequence, which data unit comprises one or more segments. The or each segment is transmitted from the lower data handling level (12) of the transmitting entity (13) to the lower data handling level (17) of the receiving entity (19) via a transmission link between the transmitting entity (13) and the receiving entity (19). An acknowledgement of receipt of the or each segment is sent from the lower data handling level (17) of the receiving entity to the lower data handling level (12) of the transmitting entity.