QoS Control Using Adaptive Layered Data Transmission

To improve the QoS of best-effort based networks and accommodate heterogeneous receivers different solutions based on applying hierarchical transmission of data streams have been introduced. These solutions are based on multicasting a base layer which is received by all interested end systems. In addition, enhancement layers are transmitted that improve the quality of the base layer. Each receiver can determine the number of enhancement layers to join and thereby the QoS he would like to receive based on its own capabilities and view of the network congestion state. With this approach, however, the quality of a received data stream is improved or reduced with the granularity of one layer. Depending on the encoding and transmission method used, the additional bandwidth required by each layer can vary greatly. To fine tune the QoS changes, we propose in this paper to enhance the hierarchical transmission schemes through sender adaptation using a scheme called adaptive layered transmission (ALT). With the ALT approach, the sender dynamically redistributes a data stream on the different layers based on the feedback of the receivers. In addition, ALT allows for dynamic discovery of the appropriate transmission rate for each layer. First results obtained through simulations suggest an overall improvement of the QoS perceived by heterogeneous receivers.