基于北斗卫星预警信息发布的通信参数设计

基于北斗卫星的预警信息发布是利用北斗卫星导航系统的短报文功能进行预警信息的发布，可有效提高预警信息发布的覆盖范围和时效性。该文提出了这种发布方式下一种新的通信参数设计方法，预警信息的传输次数和指挥机的通播ID数是基于北斗卫星的预警信息发布方式中需要确定的两个重要通信参数。定量分析表明:随着传输成功率阈值或预警信息分包数减小，预警信息的最优传输次数呈阶梯状减少；随着发布时效增加，指挥机的最优通播ID数近似线性减少；随着传输成功率阈值或预警信息分包数减小，指挥机的最优通播ID数呈阶梯状减少。该文提出的通信参数设计方法可在相关基于北斗卫星的预警信息发布系统设计时作为指标推算的参考依据。

Design of Communication Parameters for Beidou Satellite-based Early Warning Information Distribution Method

Beidou satellite-based early warning information distribution (BD-EWID) uses short message service of Beidou Navigation Satellite System to distribute early warning information. BD-EWID effectively improves coverage and timeliness of early warning information distribution in China, especially in marine and distant land areas. However, packet length and service frequency of short message are restricted in Beidou Navigation Satellite System. The data amount of a piece of early warning information often exceeds the transmission capacity of one short message. Therefore, long early warning information must be segmented into multiple smaller packets and sent multiple times. However, the more the packets are, the lower the transmission success rate is, and the longer the whole transmission time is. The existing literature has proposed methods of parallel transmission of uplink terminal and unified message compensation to solve these problems in BD-EWID.Transmission times of early warning information and the number of broadcast ID are two important communication parameters in the method of parallel transmission of uplink terminal and the unified message compensation. The transmission times are closely related to the number of packets and transmission success rate of packets, affect the occupancy rate of channel resource in Beidou Navigation Satellite System. The number of broadcast ID is closely related to transmission timeliness, and affects the scale of the whole system. In order to satisfy demands of transmission success rate of the entire early warning information and transmission timeliness, and to save resource, a new design method of those two communication parameters in BD-EWID is proposed.The design method of two communication parameters is described in detail. The relationship of transmissiontimes, the number of packets and transmission success rate are analyzed. An explicit calculation formula of times of transmission is proposed to obtain the optimal value. The larger the number of packets is, or the higher the transmission success rate is, the more the optimal times of transmission are. Also, the relationship of broadcast ID number, transmission timeliness and transmissiontimes are analyzed. An explicit calculation formula of the number of broadcast ID is proposed to obtain the optimal values. The larger the transmission timeliness is, the smaller the number of broadcast ID is. Finally, optimal results are calculated with the transmission success rate and transceiver delay which are obtained from the experiments. With the increase of the number of packets and transmission success rate, optimal times of transmission increases stepwise. With the increase of transmission timeliness, the optimal number of broadcast ID approximately linearly decreases.The proposed design method of communication parameters can be used as a reference of index calculation in the BD-EWID system design phase.