针对现存陆地移动卫星(land mobile satellite,LMS)信道模型使用场景有限及状态持续时间概率密度函数(state duration probability density function,SDPDF)不精确问题,提出能准确有效地描述更多操作场景的窄带LMS信道模型.利用对数正...针对现存陆地移动卫星(land mobile satellite,LMS)信道模型使用场景有限及状态持续时间概率密度函数(state duration probability density function,SDPDF)不精确问题,提出能准确有效地描述更多操作场景的窄带LMS信道模型.利用对数正态分布近似SDPDF的Semi-Markov链实现状态序列.在每一状态内结合传播参数生成服从Loo分布的载噪比时间序列.通过在慢衰落成分中引入多普勒频移以增加参数数据库及扩展适用场景.研究不同场景下状态概率、载噪比时间序列的一阶统计特性和90%信号有效性所需的余量,并与实测值比较.研究结果表明:该模型能在多场景下有效地代表阴影条件,且在不同信道环境中的各仰角和方位角下具有较好适用性,可用于系统性能分析.展开更多
Since the lower power requirement of code division multiple access(CDMA) than that of other multiple access, the CDMA technology is suitable to be used in low earth orbit(LEO) satellite communication system whose spac...Since the lower power requirement of code division multiple access(CDMA) than that of other multiple access, the CDMA technology is suitable to be used in low earth orbit(LEO) satellite communication system whose space power is limited due to the small size of satellite. The pilot channel of CDMA technology is very important for earth mobile station(EMS) in LEO system to recover carrier and code, but the power requirement of pilot channel is very higher than that of other channels. In this paper, a power reduction method for pilot channel is proposed. By the new method, the power of pilot channel transmitted from LEO satellite is reduced to a lower level. For improving the signal to noise ratio(SNR) of pilot channel with lower power, coherent integration is employed in EMS at the pre-processing stage. Considering the high dynamic situation of LEO satellite, the long period of time for integration will deteriorate the receiving performance of EMS, therefore, a dynamic compensation module is added to carrier tracking loop against the high dynamic. Meanwhile, the transfer function of the new tracking loop and the condition for steadystate zero error are deduced. Numerical examples are provided to demonstrate effectiveness of the proposed approach.展开更多
文摘针对现存陆地移动卫星(land mobile satellite,LMS)信道模型使用场景有限及状态持续时间概率密度函数(state duration probability density function,SDPDF)不精确问题,提出能准确有效地描述更多操作场景的窄带LMS信道模型.利用对数正态分布近似SDPDF的Semi-Markov链实现状态序列.在每一状态内结合传播参数生成服从Loo分布的载噪比时间序列.通过在慢衰落成分中引入多普勒频移以增加参数数据库及扩展适用场景.研究不同场景下状态概率、载噪比时间序列的一阶统计特性和90%信号有效性所需的余量,并与实测值比较.研究结果表明:该模型能在多场景下有效地代表阴影条件,且在不同信道环境中的各仰角和方位角下具有较好适用性,可用于系统性能分析.
基金supported by the National High Technology Research and Development Program of China (863 Program) (No.2012AA01A502)the National Natural Science Foundation of China (No.61179006)the Science and Technology Support Program of Sichuan Province (No.2014GZX0004)
文摘Since the lower power requirement of code division multiple access(CDMA) than that of other multiple access, the CDMA technology is suitable to be used in low earth orbit(LEO) satellite communication system whose space power is limited due to the small size of satellite. The pilot channel of CDMA technology is very important for earth mobile station(EMS) in LEO system to recover carrier and code, but the power requirement of pilot channel is very higher than that of other channels. In this paper, a power reduction method for pilot channel is proposed. By the new method, the power of pilot channel transmitted from LEO satellite is reduced to a lower level. For improving the signal to noise ratio(SNR) of pilot channel with lower power, coherent integration is employed in EMS at the pre-processing stage. Considering the high dynamic situation of LEO satellite, the long period of time for integration will deteriorate the receiving performance of EMS, therefore, a dynamic compensation module is added to carrier tracking loop against the high dynamic. Meanwhile, the transfer function of the new tracking loop and the condition for steadystate zero error are deduced. Numerical examples are provided to demonstrate effectiveness of the proposed approach.
