面向低轨卫星的星地信道模型综述

苏昭阳; 刘留; 艾渤; 周涛; 韩紫杰; 段相龙; 张嘉驰

doi:10.11999/JEIT230941

面向低轨卫星的星地信道模型综述

doi: 10.11999/JEIT230941

1.
北京交通大学电子信息工程学院北京 100044
2.
山东交通学院轨道交通学院济南 250357

基金项目: 国家自然科学基金(62341102)，中国国家铁路集团有限公司科技研究开发计划(N2023G060)

详细信息

作者简介:
苏昭阳：男，博士生，研究方向为无线信道测量与建模、卫星移动通信等

刘留：男，教授，博士生导师，研究方向为无线信道测量与建模、时变信道信号处理、5G关键技术、高铁宽带接入物理层关键技术等

艾渤：男，教授，博士生导师，研究方向为宽带移动通信系统与专用移动通信、通信工程、人工智能等

周涛：男，教授，博士生导师，研究方向为通信信号处理、无线信道测量与建模研究等

韩紫杰：女，硕士生，研究方向为卫星移动通信等

段相龙：男，硕士生，研究方向为卫星移动通信等

张嘉驰：男，博士，研究方向为宽带移动通信技术、卫星移动通信等

通讯作者:
刘留　liuliu@bjtu.edu.cn

中图分类号: TN927.2
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出版历程
- 收稿日期: 2023-08-30
- 修回日期: 2023-12-19
- 网络出版日期: 2023-12-25

Survey of Satellite-ground Channel Models for Low Earth Orbit Satellites

1.
School of Electronic and Information Engineering, Beijing Jiaotong University, Beijing 100044, China
2.
School of Rail Transportation, Shandong Jiaotong University, Jinan 250357, China

Funds: The National Natural Science Foundation of China (62341102), Technology Research and Development Program of China Railway (N2023G060)

摘要

摘要: 低轨卫星(LEO)具备通信时延低、部署成本低、覆盖范围广的特点，已经成为了建设未来空天地一体化网络的重要组成部分。然而卫星通信中端到端传播距离长、经历衰落复杂、终端移动速度快，其信道特性与地面蜂窝网络信道具有很大差异。基于此，为了对低轨卫星星地信道特性以及信道模型有较为全面的认识，该文总结了目前国际标准组织对星地信道的标准化进展，讨论了星地信道在不同传播位置处的衰落特性，根据建模方法对已有的重要信道模型进行了划分与阐述，最后对未来的工作提出了展望。
- 低轨卫星 /
- 无线信道 /
- 信道建模 /
- 信道测量
Abstract: Low Earth Orbit (LEO) satellite has the characteristics of low communication delay, low deployment cost and wide coverage, and has become an important part of the construction of the future space earth integrated network. However, satellite communication has large end-to-end propagation distance, complex fading and fast terminal movement speed, thus the channel characteristics are very different from the terrestrial cellular network. Based on this, in order to have a more comprehensive understanding of the characteristics and channel model of LEO satellite-ground channel, the current standardization progress of the satellite-ground channel by the international standards organization are summarized, the fading characteristics of the satellite ground channel at different propagation positions are discussed, the existing important channel models are classified and shown according to the modeling method, and finally the prospects for future work are proposed.
- Low Earth Orbit (LEO) satellite /
- Wireless channel /
- Channel modeling /
- Channel measurement

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图 1 全文主要章节架构

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图 2 卫星信号穿过大气层路径示意图

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图 3 空间段各大尺度损耗与频率的关系

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图 4 多普勒频偏随仰角和频率的变化关系

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图 5 6状态马尔可夫模型

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图 6 星地信道3D几何模型

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表 1 各标准特点与不足对比

标准组织	标准名称	标准特点	标准不足
ITU	ITU-R P.618	大气吸收衰减、降雨和云雾衰减、闪烁效应等	仅支持城区，只考虑了遮蔽概率
	ITU-R P.2108	地物损耗的计算	只支持城区和郊区，只考虑了地面段植被与建筑物的遮挡
	ITU-R P.681	适用于陆地移动卫星(Land Mobile Satellite, LMS)的宽带和窄带信道模型，以及卫星到室内的信道模型	只支持城区和郊区，只考虑了地面段植被与建筑物的遮挡
3GPP	3GPP TR 38.811	自由空间损耗、大气吸收损耗、降雨和云雾损耗、闪烁效应、多普勒频偏和变化率等，提出了TDL与CDL模型	基于5G蜂窝信道模型的改进，适用于低频段，没有考虑高移动性以及大气损耗
3GPP	3GPP TR 38.821	规定了星地链路仿真参数配置、新空口(New Radio, NR)为支持NTN需要做出的调整等	基于5G蜂窝信道模型的改进，适用于低频段，没有考虑高移动性以及大气损耗
ETSI	DVB-S2	卫星广播技术帧结构、调制和信道编码方案、物理层组帧、基带信号成形等	仅对AWGN信道进行了优化
ETSI	DVB-S2X	更完善的调制和信道编码方案、甚低信噪比通信方案等	仅对AWGN信道进行了优化

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表 2 3GPP TR 38.811标准中城区、郊区场景地物损耗参考值

仰角(º)	S频段		Ka频段
仰角(º)	城区	郊区	城区	郊区
10	34.3	19.52	44.3	29.5
20	30.9	18.17	39.9	24.6
30	29.0	18.42	37.5	21.9
40	27.7	18.28	35.8	20.0
50	26.8	18.63	34.6	18.7
60	26.2	17.68	33.8	17.8
70	25.8	16.50	33.3	17.2
80	25.5	16.30	33.0	16.9
90	25.5	16.30	32.9	16.8

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表 3 国内外各组织信道测量对比

测量组织	频段	场景	测量卫星
ESA	UHF/L/S/Ka	城区、郊区、乡村、移动列车等	MARECS、直升机模拟
NASA	UHF/L/S	公路、乡村、丘陵等	ATS6, MARECS、直升机模拟
日本通信研究实验室	L	城区、公路、郊区、乡村	ETS-V
澳大利亚电信研究所	L	郊区、乡村	ETS-V
CRC	UHF/L	郊区、乡村	MARECS、热气球、直升机模拟
中国科学院	UHF	密集城区、郊区、草坪湖泊等空旷地区	LEO模拟器模拟
加利福尼亚大学	L	城区	Orbcomm, ridium NEXT
德国联邦国防军慕尼黑大学	Ka	密集城区、乡村、山地	无人机模拟

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表 4 不同经验性模型的对比

文献	频段	场景	仰角	特点
[43]	L/S	高速、郊区、乡村	20°～60°	对ERS模型进行简化，搭建了信道仿真器
[44–48]	L	高速、郊区、乡村	20°～60°	建立了ERS模型，可预测由植被阴影所应当预留的衰落余量
[49]	L	高速、郊区、乡村	20°～80°	对ERS模型进行改进，扩大了可用仰角
[50]	L/S	郊区	60°～80°	对ERS模型进行改进，扩大了可用频率范围，但只适用于高仰角
[51]	L/S	郊区、乡村	20°～80°	结合了文献[49]和文献[50]的模型，在可用频段扩大的同时可用仰角范围也扩大
[52]	L/S/Ka	城区	0°～80°	基于无人机信道模型改进，通过调整模型参数可适用于不同城区

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表 5 不同统计性模型的对比

文献	频段	场景	状态数	模型构成	特点
[53,54]	L	乡村	单状态	Rice/Lognormal	受遮挡的直射分量与不受遮挡的多径分量的组合
[55]	L	城区/公路/郊区/乡村	单状态	Rice/Lognormal	直射分量与多径分量均受到同分布的阴影衰落
[56]	L	乡村	单状态	Rice/Lognormal	直射分量与多径分量均受到阴影衰落，允许两个阴影衰落独立
[57]	L	乡村	单状态	Rice/Nakagami	将阴影衰落改进为Nakagami分布
[58]	L	城区/公路/郊区/乡村	单状态	Beckmann/ Lognormal	将多径分量改进为Beckmann分布
[59]	L/S/Ka	城区/公路	单状态	Rice/Rayleigh/ Lognormal	可推导为其他经典模型
[60,61]	L	乡村	单状态	Squared Rice/Nakagami	考虑了分集接收
[62]	L	城区/公路	两状态	Rice/Rayleigh/ Lognormal	信道分为“好状态”、“坏状态”
[63]	L	城区/郊区/乡村	两状态	Rice/Rayleigh/ Lognormal	根据仰角判断信道状态
[64]	L/S/Ka	城区/公路/郊区/乡村	3状态	Loo/Loo/Loo	以植被引起的轻微阴影作为第2状态
[65]	L/S/Ka	城区/公路/郊区/乡村	3状态	Loo/R^M/Loo	采用R^M模型作为第2状态
[67]	L	城区/公路/郊区/乡村	4状态	Rice/Rice/Rayleigh/Lognormal	将4种不同场景视为4种状态
[68]	L	城区/公路/郊区/乡村	6状态	Rice/Rayleigh/ Lognormal	将“好状态”与“坏状态”细分为6个子状态
[69]	Ku	城区/公路	多状态	RJ-MCMC	无需认为假设状态数和每个状态的分布
[70]	L/S	城区/公路/郊区/乡村	多状态	Rice/Nakagami	将卫星轨道分为“好区域”与“坏区域”

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表 6 不同几何随机性模型的对比

文献	频段	场景	特点
[71]	UHF/L	郊区/农村	建立了基于单一散射点的几何模型
[72]	L	农村	利用多个单一散射体组成复杂散射体
[73]	Q	城区/郊区/乡村	建立了3D几何模型
[74]	-	郊区	利用UAV作为中转进行建模
[75]	K	-	根据卫星在空间中的分布建模

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表 7 不同基于机器学习的模型对比

文献	频段	采用的ML算法	特点
[79]	L	CNN	提取2D卫星图像信息估计路损指数与阴影衰落
[80]	Q	MLP/LSTM	使用MLP预测晴天损耗，使用LSTM预测雨天损耗
[81]	Q	LSTM	使用7种大气参数训练模型，但是无法用于Q频段以外的频段
[82]	S/Ku/Ka/Q/V	LSTM	建立了空间段与地面段的分段模型
[83]	Q/V	LSTM	将统计性建模与ML相结合
[84]	X	RNN	预测了闪烁效应

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表 8 频段与信道模型对应关系

频段	信道模型类型
频段	经验性模型	统计性模型	几何随机性模型	基于机器学习的模型
L	[43–52]	[53–65,67,68,70]	[71,72]	[79]
S	[43,50–52]	[59,64,65,70]	/	[82]
X	/	/	/	[84]
Ku	/	[69]		[82]
K	/	/	[75]	/
Ka	[52]	[59,64,65]	/	[82]
Q/V	/	/	[73]	[80,81,82,83]

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