卫星网络中基于网络编码的ARQ机制

Novel ARQ Mechanism Based on Network Coding in Satellite Networks

随着航空航天技术的发展,越来越多的应用任务需要利用卫星通信进行信息传输。在卫星网络中,已有的研究成果大都采用了ARQ机制来降低卫星信道的数据丢失率。然而由于卫星信道具有长时延的特点,因此ARQ所采用的反馈重传机制会大幅增加卫星信道的传输时延。因此,针对卫星网络,提出了一种基于网络编码的ARQ(SatNC-ARQ)机制来减少卫星信道的丢包数,并通过减少重传次数来降低卫星信道的传输时延。在Sat-NC-ARQ中,卫星终端除了发送几个真实业务终端的数据包外,还会创建一个虚拟业务终端发送网络编码数据包,从而在接收方,只要接收到足够多的数据包,就能对所有的数据包进行解码,于是可以大幅降低卫星信道的传输时延以及丢包数。还对Sat-NC-ARQ所具有的一些性质进行了理论分析。仿真结果显示,相对于选择性重传ARQ机制,Sat-NC-ARQ机制能够降低大约11%的传输时延和86%的丢包数。

With the development of aeronautics and astronautics technologies, more and more tasks need to use the satellite commu- nication technology to transmit information.In satellite networks, the existing research results mainly use ARQ mechanism to decrease the data loss probability of satellite channel. Since the satellite channel has the very long delay, the acknowledgment and retransmission mechanism of ARQ will highly increase the transmission delay of satellite channel.Therefore, this paper proposes a novel ARQ （ Sat-NC- ARQ ） mechanism based on network coding in satellite networks to decrease packet loss number, and Sat-NC-ARQ can also decrease the transmission delay of satellite channel by decreasing the number of retransmissions. In Sat-NC-ARQ, the source satellite terminal not only sends the packets of several actual service terminals,but also creates a virtual service terminal to send the network coding packet. Therefore, the destination satellite terminal can decode all the packets as long as receiving enough packets, and so can highly decrease the transmission delay and packet loss number of satellite channel.After that,the theory analysis of Sat-NC-ARQ has also been given. The simulation results show that the Sat-NC-ARQ mechanism can decrease the transmission delay by about 11% and the packet loss number by 86% according to Selective Repeat ARQ.