D2D-assisted F-RANs Cooperative Retransmission Scheme Based on RA-IDNC

‍ ‍Aiming at the problems of insufficient utilization of network resources and high average completion delay of retransmission in D2D assisted F-RANs scenarios， a D2D assisted F-RANs retransmission strategy based on Rate perception IDNC （RA-IDNC） was proposed. Network coding transmission is carried out by using cellular links in different frequency bands and out-of-band D2D links. In the retransmission stage， the minimum completion time formula of retransmission using network coding in D2D assisted F-RANs is derived. Then， the RA-IDNC graph combined with the terminal and the enhanced Remote Radio Head （eRRH） is constructed using the graph theory method， and the problem of minimizing the completion time of retransmission is transformed into the maximum weight independent set search problem of the union graph. The weight is designed by considering factors such as link packet loss rate， number of terminal lost packets， transmission rate of device interface and number of receiving terminals. In order to reduce the computational complexity， greedy algorithm is used to search the joint RA-IDNC graph and select the optimal encoding transmission strategy. Finally， based on the different transmission duration caused by inconsistent interface transmission rates， the device that meets the retransmission condition is searched， and the joint RA-IDNC diagram of the device under idle time is constructed， and the feasible encoding transmission scheme is searched from the terminal that is idle in advance and eRRH. The number of packets lost by the terminal in a single retransmission process can be recovered as much as possible without increasing the transmission time. Compared with the existing RA-IDNC encoding scheme， simulation results show that the scheme mentioned in this article is able to efficaciously increase retransmission efficiency in F-RANs and decrease the average length of time of retransmission.