低轨卫星通信凭借低传输时延和组网灵活等优势,正成为新一代卫星通信的关键技术。广义频分复用(Generalized Frequency Division Multiplexing,GFDM)作为候选波形,能够满足低轨卫星通信各种应用场景需求。在基于GFDM的低轨卫星通信系统...低轨卫星通信凭借低传输时延和组网灵活等优势,正成为新一代卫星通信的关键技术。广义频分复用(Generalized Frequency Division Multiplexing,GFDM)作为候选波形,能够满足低轨卫星通信各种应用场景需求。在基于GFDM的低轨卫星通信系统中,由于GFDM子载波间非正交特性以及低轨卫星信道存在时间-频率双选择性,导致数据符号受到严重的子载波间干扰和子符号间干扰,传统信道估计算法难以实现可靠的数据传输。现有的基于离散导频的迭代信道估计和信号检测算法(Iterative Channel Estimation and Signal Detection Algorithm Based on Discrete Pilots,ICESD-DP)虽然提高了在双选信道下信道估计的准确性,但需要付出高昂的计算成本。为解决上述问题,提出了一种基于判决重构符号的迭代信道估计和干扰消除算法(Iterative Channel Estimation and Interference Cancellation Algorithm Based on Judgment Reconstructed Symbols,ICEIC-JRS),使用经过干扰预处理的导频进行初始信道估计和均衡,在每次迭代中利用Turbo译码器生成的判决重构符号估计数据符号的有效增益和干扰增益,继而对接收符号进行干扰消除,以提高信道估计与符号检测的精度。仿真结果表明,与ICESD-DP相比,ICEIC-JRS在较多迭代次数下表现出更优异的误码率(Bit Error Rate,BER)和均方误差(Mean Square Error,MSE)性能,且ICEIC-JRS的单次迭代复杂度下降了一个数量级,更适用于对运算复杂度有较高要求的低轨卫星通信系统。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
文摘低轨卫星通信凭借低传输时延和组网灵活等优势,正成为新一代卫星通信的关键技术。广义频分复用(Generalized Frequency Division Multiplexing,GFDM)作为候选波形,能够满足低轨卫星通信各种应用场景需求。在基于GFDM的低轨卫星通信系统中,由于GFDM子载波间非正交特性以及低轨卫星信道存在时间-频率双选择性,导致数据符号受到严重的子载波间干扰和子符号间干扰,传统信道估计算法难以实现可靠的数据传输。现有的基于离散导频的迭代信道估计和信号检测算法(Iterative Channel Estimation and Signal Detection Algorithm Based on Discrete Pilots,ICESD-DP)虽然提高了在双选信道下信道估计的准确性,但需要付出高昂的计算成本。为解决上述问题,提出了一种基于判决重构符号的迭代信道估计和干扰消除算法(Iterative Channel Estimation and Interference Cancellation Algorithm Based on Judgment Reconstructed Symbols,ICEIC-JRS),使用经过干扰预处理的导频进行初始信道估计和均衡,在每次迭代中利用Turbo译码器生成的判决重构符号估计数据符号的有效增益和干扰增益,继而对接收符号进行干扰消除,以提高信道估计与符号检测的精度。仿真结果表明,与ICESD-DP相比,ICEIC-JRS在较多迭代次数下表现出更优异的误码率(Bit Error Rate,BER)和均方误差(Mean Square Error,MSE)性能,且ICEIC-JRS的单次迭代复杂度下降了一个数量级,更适用于对运算复杂度有较高要求的低轨卫星通信系统。
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.
