Research Of Link Packet Error Rate Based Automatic Retransmission Technology For Space Networks

With the development of electronics and wireless communications and technology, network has influenced all aspects of human life. The network technology has changed from fixed wired transmission to wireless transmission, from flat grid structure to three-dimensional space structure, from static node to high-speed dynamic node. The concern and development of space resource and rapid development of aerospace technology, have given material and technical support to the foundation and development of space network system. The space network system will become the important component of future network world. Unfortunately, the space network is faced with the challenge of high topological variation rate, high node speed, long link propagation delay, strong space interference, high bit error rate and limited space resources, which have influence the reliability of space network data transmission, and have become a important technological barrier to the development and application of space network.Our article has reviewed the development of spatial information network, and briefly introduced the characteristics, R & D process and challenges of space DNT network, and studied the features of associated transfer protocol. According to the data transmission reliability of space DNT network, we put forward a space network automatic re-transmission mechanism which is based on the link error rate with the abbreviation of BEAR-TP protocol. In the process of space link data transmission, in the condition of unstable link propagation delay raised from node movement, this protocol could adopt different transport mechanisms to ensure the reliability of data transmission and the validity of the link utilization.BEAR-TP protocol is concerned about the space network data transmission and re-transmission tactics with the target of efficient and reliable inter-node communication. BEAR-TP protocol is founded on the base of Saratoga protocol. It is put forward to resolve the problem that the file transfer performance of Saratoga protocol will decrease in condition of long link delay and high error rate. BEAR-TP protocol could adapt data transmission in different link environment. BEAR-TP protocol proposed the envisage that the re-tranmission tactics should change according to the error rate variation. LEARQ mechanism should be adopted in condition of long link delay and low error rate. While HEARQ mechanism should be adopted in the opposite condition. According to changes of link environment, we adjust the transmission strategy flexibly, so that the protocol can adapt to more harsh and instable environment of the space network, however, the use of HEARQ mechanisms is BEAR-TP and Saratoga, DTTP agreement where the difference between. Therefore, HEARQ mechanism is the main content of our simulation tests. On ONE simulation platform, according to the characteristics of the space DTN network, we established a network model, used MapRouteMovement module to set the node's trajectories, and established the connection between nodes. In the simulator, we set up some parameters, such as, transmission rate, transmission distance, file size, packet size, packet error rate, retransmission rate, etc, and run a simplified HEARQ and Saratoga agreement, compared with and analyzed the performance difference between the two protocols, verified the transmission performance of HEARQ mechanism in case of high error rate and long delay. The results show that HEARQ mechanism of transmission is better than Saratoga agreement, particularly in the delay or link error rate is rising, the gain is even more evident, the transferation is used in less time, and the reliability of data transmission is higher.