Playtime-Oriented Retransmission Control Method for Multimedea Streaming

In this paper, we propose playtime-oriented retransmission control method for multimedia streaming. In multimedia streaming, playtime of each packet is decided when a client starts playing contents. If a packet does not arrive at a client until its playtime, the packet is discarded by the client application. In our method, a client sends a server NACK packet when it detects packet losses. NACK packet includes not only identifiers of lost packets but also playtime of a top packet of client buffer to a server. The server subtracts playtime of the top packet of client buffer from that of lost packet, and compares result of the calculation to RTT between the server and the client. If former is larger, the server retransmits the lost packets to the client. If not, the server retransmits no packets. Therefore, the number of unnecessary retransmission of packets is decreased. Moreover, we estimate our method and compare it to the simple retransmission method using NACK packets. From the results, we show that Our method hardly decreases the number of retransmitted packets which achieve a client until their playtime while our method drastically decreases the number of retransmitted packets.