AIS基站短消息特性

Short message characteristics of AIS base stations

研究了在内河与港口应用环境下,由船载自动识别系统(AIS)基站发送到船舶的短消息特征,分析了AIS报文在场强下降后的波形失真与误包原理。在半实物仿真平台下,分析了消息长度与误包率的关系,并给出相应的误包率预测模型。结合Hata-Okumura模型,提出了拥挤航道下AIS基站向船舶发送短消息的极限容量。最后以黄浦江上海航道为例,运用极限计算模型对其极限容量进行了预测,并与实测结果进行了对比。对比结果表明:短消息可靠性随长度增加与场强降低而逐步下降,基站能同时进行短消息管理的AIS船舶数量有限,对于本文设定的黄浦江上海航道,当AIS目标船舶数量达到625艘时,AIS基站能同时进行短消息通讯的AIS船舶容量的计算结果为26艘,实测为24艘,计算结果与实测结果基本一致。

The characteristics of short messages from automatic identification system（AIS） base stations to ships in the inland river and port were studied. The principles of waveform distortion and package error were analyzed when AIS field strength was declined. In the hardware in-the- loop simulation platform, the relationship between message length and package error rate was analyzed, and the prediction model of package error rate was proposed. Combined with Hata- Okumura model, the maximum capacity for short messages sent from AIS base stations to ships was proposed in crowded channel. At last, taking the Shanghai Channel of Huangpu River as an example, using the proposed model, the maximum capacity was calculated and compared with the measured result. Comparison result indicates that the reliability of short message decreases with the increase of short message length and the decrease of fixed field strength. The number of AIS target ships communicating with AIS base stations meanwhile is limited. For the Shanghai Channel of Huangpu River, the calculated number of AIS target ship communicating with an AIS base station is 26 when the total AIS target ships is 625, and the measured value is 24, so the calculated value basically matches with the reality value. 2 tabs, 6 figs, 15 refs.