A classification network coding retransmission approach based on the minimal set coverage is proposed to improve the single relay cooperative transmission efficiency. In this scheme

to make full use of the advantage of relay-assisted transmission

the lost packets of receivers are classified into two categories according to the packet reception status of relay node after the initial transmission

and then the packets are encoded for retransmission according to the category sequentially. For each classification

according to the corresponding status feed matrix to search for encoding opportunities and generate encoding packets

the encoded packets selecting procedure is abstracted as the set coverage problem

and the number of retransmissions is approached the minimum value by solving the minimal set coverage problem. In addition

to reduce the number of retransmission packets and improve retransmission efficiency

encoding opportunities between the two types of lost packet are further used to generate new encoding packets on the premise of not increasing the current number of encoding packets. The analysis and simulation results show the effectiveness of the scheme proposed.