低轨卫星通信系统中的一种波束小区切换算法

A Spot Beam Cell Handover Algorithm in LEO Satellite Communication System

针对低轨卫星移动通信系统中终端切换频繁,以及因邻区列表动态变化特性使得邻区测量存在较大不确定性的问题,提出了一种基于波束可视时间与接收信号强度的波束小区切换准则。推导了定向天线信号场值广播至地面的时变表达式,基于此预测切换触发时间,并进一步计算终端的邻区列表。根据波束可视时间与接收信号强度计算邻区的切换权重并进一步选择目标波束,针对重复切换的情形设置同一波束切换次数上限。仿真结果表明,该算法可以有效降低终端切换的频次并避免"乒乓切换"的发生,且终端纬度越高,算法效果越明显。

For the problem of frequent handover and the uncertainty of neighboring cell measurement resulting from the dynamic characteristics of neighboring cell list,a cell handover criterion based on beam-visibility time and receiving signal strength is proposed. The time-variant formulation of the signal strength transmitted by directional antenna on the ground is derived. Based on this,the handover triggered time is predicted and the neighboring cell list is speculated then. The handover weight of a neighboring cell is computed by its beam-visibility time and receiving signal strength. The decision which takes the same beam as target over the predefined threshold times is rejected. Simulation results show that the algorithm can reduce the frequency of cell handover and avoid ping-pong handover effectively. The higher the latitude of the terminal is,the better this algorithm takes effect.