2. Robot Technology Used for Special Environment Key Laboratory of Sichuan Province, Southwest University of Science and Technology, Mianyang, Sichuan 621010, China;
3. 32 Shaanxi Tiansi Information Technology Co., Ltd, Xi'an, Shaanxi 710065, China
Overview: In the battlefield environment of complex terrain, the use of ultraviolet (UV) communication in armored formations overcomes the shortcomings of cable laying. And due to the strong absorption of atmosphere, UV communication have low identification rate performance, which has better covert transmission performance than other wireless communication modes such as infrared optical communication and radio frequency communication. Because of the serious attenuation of the UV atmospheric channel and high path loss, the end-to-end communication between the formations is easily interrupted, and the receiving end cannot receive the combat missions in time, which affects the combat capability of the formation. In order to improve the cooperative communications ability between the armored formations and the end-to-end communication quality of UV, how to select a reliable single relay node for the cooperative communications system of the UV NLOS (non-line-of-sight) multi-relay parallel link is studied.
The optimal relay selection algorithm for armored formations based on wireless UV covert communication is proposed on the premise of decode-and-forward protocol, combined with the threshold decision idea. The algorithm combines the advantages of UV NLOS communication. The optimal relay selection is made for the formations according to the signal to noise ratio (SNR) threshold and channel characteristics selection strategy, and the bit error rate (BER) performance is analyzed under Gaussian noise model. It can be seen from the simulation results that the BER performance of the UV cooperative communications system is affected by the threshold, the relay geometry and the relay position. Under the condition of higher signal to noise ratio and fewer candidate relay nodes, the cooperation threshold can be appropriately reduced to improve the system BER performance. Therefore, the algorithm can select appropriate coordination thresholds according to different SNR environments and the number of relay nodes, and select the best relay to establish a UV NLOS relay cooperative communications link. When the relay node selects a narrow transmitter and receiving apex angle as well as a wide receiving FOV, the relay closer to the source node becomes preferable. Therefore, when the cooperative communications link changes dynamically, the receiving and transmitting states of the relay node is adjusted according to the distance from the cooperative relay node to the source node. This enables the cooperative communications system to obtain the best BER performance, enhance the invulnerability of the cooperative communications links, and meet the communication needs of armored formations in complex battlefield environments.