AI 中文总结
本文针对LEO星座通信与PNT服务的波束调度问题，提出两种策略并对比，在通信优先级下评估其PNT可用性，为融合PNT服务提供方案。
AI 中文摘要
未来低轨（LEO）星座预计将把定位、导航与授时（PNT）作为原生服务，与宽带服务一同提供，以此消除5G非地面网络继承的全球导航卫星系统（GNSS）依赖，这在文献中被称为融合PNT。本文研究在通信保持完全优先级的场景下，低轨星座中的多波束卫星应如何在通信服务（COM）与PNT之间分配波束和功率。卫星上的每个波束可提供通信服务、PNT服务或两者（存在一定限制）。在每颗卫星的最大可用功率固定的情况下，PNT服务的评估指标为达到95%时间可用性的区域占比。本文将该PNT可用性问题建模为波束-功率预算问题，由于接收机的处理增益，PNT波束无需以与通信波束相同的功率发射。本文对比了两种卫星波束调度策略：第一种策略中，小区内为通信需求服务的波束专用于通信，因此该小区的PNT服务由视距内的其他卫星提供，无需信号修改，在均匀/人口加权流量分布下可达到70.5%/88.2%的可用性；第二种策略中，通信波束也可提供PNT信号，该波束内测距将测距信号嵌入通信波形中，达到可用性上限，但需以波形重新设计为代价。两种策略的可用性差距集中在赤道带的薄重叠区域。
英文摘要
Future low Earth orbit (LEO) constellations are expected to provide positioning, navigation, and timing (PNT) as a native service alongside broadband, removing the GNSS dependency inherited by 5G non-terrestrial networks. This is known in the literature as fused PNT. This paper asks how a multibeam satellites in a LEO constellation should share their beams and power between a communication service (COM) and PNT in the scenario when communications keep full priority. Each beam on a satellite can provide a communication service, a PNT service or both (this under certain limitations). Then, the PNT service is evaluated by the share of area the reach $95\%$-of-time availability for a fixed maximum power available on each satellite. This paper present this PNT availability question as a beam-power budget, as the PNT beams do not need to transmit at the same power as the communication beams thanks to the processing gain on the receiver. Two satellite beam scheduler policies are compared: one where on a cell the beam serving COM demand is exclusive for COM, therefore the PNT service in this cell is provided by the other satellites in line of sight, it requires no signal modification and attains $70.5\%$ / $88.2\%$ availability under homogeneous/population-weighted traffic profiles; and a second policy, the COM beam can provide also PNT signals, this in-beam ranging embeds the ranging signal in the COM waveform, reaching the ceiling at the cost of waveform redesign. The availability gap between the two policies is concentrated on the thin-overlap equatorial belt.
