Data transmission method, data transmission apparatus, data receiving apparatus, and packet data structure

A data transmission method for performing continuous data transmission from a transmitting end to a receiving end in units of packets, each packet having additional information relating to its sequence number, priority, and data reproduction time at the receiving end, while performing retransmission of the packets in response to a retransmission request from the receiving end, said method comprising:

• at the transmitting end,
• giving priority information to each packet to be transmitted;
• and
• storing, as retransmission data, only data of packets the priorities of which are equal to or higher than a predetermined value, in a retransmission buffer;
• at the receiving end,
• when a transmission error is detected, outputting a retransmission request for an error packet to the transmitting end by indicating the sequence number of the error packet;
• and at the transmitting end,
• only when the data of the packet having the sequence number which is indicated by the retransmission request from the receiving end is stored in the retransmission buffer, retransmitting the data of the packet having the sequence number which is indicated by the retransmission request to the receiving end.

A data transmission apparatus for relaying data transmitted from a transmitting end in units of packets, each packet having additional information relating to its sequence number, priority, and data reproduction time at a receiving end, said data transmission apparatus comprising:

• a receiving unit operable to receive packets transmitted from the transmitting end,
• a priority decision unit operable to decide the priorities of the received packets,
• a retransmission packet storing unit operable to store, as retransmission packets, only packets the priorities of which are equal to or higher than a predetermined value, based on the priority of each packet decided by the priority decision unit,
• a retransmission instruction receiving unit operable to receive a retransmission instruction from the receiving end,
• a retransmission decision unit operable to decide whether retransmission of a packet for which the retransmission instruction has been made is performed or not, based on the retransmission instruction and a storage condition of the retransmission packets in the retransmission packet storing unit,
• a transmission queue management unit operable to set the transmission order of the received packets and the packets being decided to be retransmitted in accordance with the additional information, and
• a transmission unit operable to transmit data of the packets in the transmission order set by the transmission queue management unit.

A data receiving apparatus for receiving data transmitted from a transmitting end in units of packets, each packet having additional information relating to its sequence number, priority, and data reproduction time at a receiving end, said data receiving apparatus comprising:

• a receiving unit operable to receive packets transmitted from the transmitting end,
• an error packet detection unit operable to detect error packets in which errors have occurred during transmission and output normal packets which have been normally transmitted,
• a packet priority decision unit operable to receive the result of the detection in the error packet detection unit and decide an error packet the priority of which is equal to or higher than a predetermined value, and
• a retransmission instruction output unit operable to output a request for retransmitting the error packets toward the transmitting end by indicating the sequence number of the error packet, the error packets being decided to be packets the priorities of which are equal to or higher than the predetermined value in the packet priority decision unit.