基于位置信息的低轨卫星上行时钟同步方法

Uplink clock synchronization method for low earth orbit satellite based on location information

针对传统基于测距信息来设定上行同步方法中出现的频繁更新距离信息的问题,提出了基于位置信息的上行时钟同步方法。首先,通过测量伪距组成非线性方程组,采用基于最小二乘原理的解算方法定位出地面单元的位置信息;然后,由于卫星运动的位置信息已知,进一步可以得到星地间距离随时间的变化关系,距离换算成时延,即可得地面单元的上行信号发送时间提前量;最后,调整地面单元的发射机使上行信号以较高精度恰好在分配的时隙到达卫星,实现系统上行时钟同步的目的。仿真结果表明,所提方法能对全球范围内地面静止单元以较高精度实现卫星星座通信系统内上行时钟同步,避免频繁的测距更新,且精度更高。

In order to solve the problem of updating distance information frequently in the traditional method of setting uplink synchronization based on ranging information, a uplink clock synchronization method based on location information was proposed. Firstly, by measuring the pseudoranges to form a nonlinear system of equations, the location information of the terrestrial unit was located by using the solution method based on the principle of least squares. Then, due to the known location information of satellite movement, the change relationship of the distance between the satellite and the ground with time could be further obtained. The distance was converted into time delay to obtain the time advance of the uplink signal transmission of the terrestrial unit. Finally, the transmitter of the terrestrial unit was adjusted to make that the uplink signal could just arrive at the satellite in the assigned time slot with high accuracy, and the purpose of uplink clock synchronization was achieved. The simulation results show that, the proposed method can realize the synchronization of uplink clock in the satellite constellation communication system with high accuracy for the static units in the earth surface all over the world, and avoid the frequent ranging updates with high accuracy.