Method and apparatus for transmitting data, and communication system

A communication system, comprising:

• a sending end device, configured to monitor a delay of data during transmission;
• if the delay is greater than a first delay threshold value, send blocking information used to block low priority data sent by an upper layer;
• receive high priority data sent by the upper layer;
• encapsulate the high priority data into a data unit;
• mark the data unit with a flag indicating that a retransmission is not needed;
• and send the data unit to a receiving end device;
• and the receiving end device, configured to receive the data unit sent by the sending end device;
• when it is determined that the data unit comprises the flag indicating that the retransmission is not needed, save the data unit in a retransmission buffer of the receiving end;
• when it is determined that the data unit does not comprise the flag indicating that the retransmission is not needed, judge whether the data unit is a new data unit;
• if the data unit is the new data unit, save the data unit in the retransmission buffer of the receiving end;
• if the data unit is not the new data unit, judge whether the data unit is incorrect;
• if the data unit is incorrect, discard the data unit;
• if the data unit is not incorrect, further judge whether the data unit times out;
• if the data unit times out, discard the data unit;
• if the data unit does not time out, save the data unit in the retransmission buffer of the receiving end;
• mark the data unit in the retransmission buffer of the receiving end with an additional flag through monitoring a delay status, wherein the additional flag indicates a processing manner after the upper layer receives the data unit;
• and submit the data unit to the upper layer, so that the upper layer processes the data unit according to the additional flag.

A receiving end device, comprising:

• a receiving unit, configured to receive a data unit sent by a sending end;
• a flag identification unit, configured to determine whether the data unit received by the receiving unit comprises a flag indicating that a retransmission is not needed;
• a newness and oldness judgment unit, configured to judge whether the data unit is a new data unit when the flag identification unit determines that the data unit does not comprise the flag indicating that the retransmission is not needed;
• a storage unit, configured to save the data unit in a retransmission buffer of the receiving end when the flag identification unit determines that the data unit comprises the flag indicating that the retransmission is not needed, or when the newness and oldness judgment unit judges that the data unit is a new data unit;
• a correctness judgment unit, configured to judge whether the data unit is incorrect when the newness and oldness judgment unit judges that the data unit is not a new data unit;
• a time-out judgment unit, configured to judge whether the data unit times out when the correctness judgment unit judges that the data unit is not incorrect;
• and a discarding unit, configured to discard the data unit when the correctness judgment unit judges that the data unit is incorrect;
• or discard the data unit when the time-out judgment unit judges that the data unit times out;
• an additional flag unit, configured to mark the data unit in the retransmission buffer of the receiving end with an additional flag through monitoring a delay status, wherein the additional flag indicates a processing manner after an upper layer receives the data unit;
• and a submission unit, configured to submit the data unit marked by the additional flag unit to the upper layer, so that the upper layer processes the data unit according to the additional flag.