基于RA-IDNC的D2D辅助F-RANs协作重传方案
D2D-assisted F-RANs Cooperative Retransmission Scheme Based on RA-IDNC
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摘要: 针对D2D辅助F-RANs场景中网络资源利用不充分、重传平均完成时延较高的问题,提出了一种基于速率感知IDNC(Rate perception IDNC, RA-IDNC)的D2D辅助F-RANs重传策略,通过利用不同频段的蜂窝链路和带外D2D链路进行网络编码传输。在重传阶段,首先推导了D2D辅助F-RANs中使用网络编码重传的最小完成时间公式;然后利用图论的方法构造终端和增强远程无线电头(enhanced Remote Radio Head, eRRH)联合的RA-IDNC图,将最小化重传完成时间问题转换为联合图的最大权重独立集搜索问题,并综合考虑链路丢包率、终端丢失数据包个数、设备接口传输速率、接收终端个数等因素设计权重,为了降低运算复杂度,采用贪婪算法对联合RA-IDNC图进行搜索选取最优的编码传输策略;最后,利用接口传输速率不一致造成的发送持续时间不同,搜索满足再次发送条件的设备,并构建空闲时间下设备的联合RA-IDNC图,从提前处于空闲状态的终端和eRRH中搜索可行的编码传输方案,在不增加传输时间的基础上尽可能多的恢复单次重传过程中终端丢失数据包的个数。仿真结果表明,与现有的RA-IDNC编码方案相比,本文所提方案能够有效提高F-RANs中的重传效率,降低重传平均完成时间。Abstract: 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.