基于最大似然法的GPS弱信号载噪比估计算法
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摘要
为了在弱信号环境下准确估计卫星信号载噪比,提出一种可自适应调整估计时间,基于最大似然准则的载噪比估计算法。在分析GPS信号相关器模型输出的基础上,对该算法的原理和性能进行了理论分析,研究了相干累加次数对该算法的影响,并在仿真平台上进行验证。仿真结果与理论推导吻合,在信号很弱时可通过提高累加次数对载噪比进行准确估计。相对传统载噪比估计算法,该算法估计时间较短,估值准确。根据理论推导求出满足精度要求的最小累加次数,用于自适应调整估计更新时间,可提高算法的灵活性。
In order to estimate the carrier to noise ratio under the weak signal environment,an algorithm based on the maximum likelihood criterion has been proposed which can change the update time adaptively.On the basis of GPS correlator output model,the algorithm performance is analyzed theoretically,the coherent accumulation times impact on the accuracy of the estimation.The simulation results agree with the theoretical derivation,which verify that the accuracy can be assured by increasing accumulation times under the noise environment.Compared with the traditional carrier to noise ratio estimation algorithm,the method consumes shorter time with good accuracy.Also the minimum cumulative number to meet accuracy requirements can increase the flexibility of the algorithm by adjusting estimation update time adaptively.
In order to estimate the carrier to noise ratio under the weak signal environment,an algorithm based on the maximum likelihood criterion has been proposed which can change the update time adaptively.On the basis of GPS correlator output model,the algorithm performance is analyzed theoretically,the coherent accumulation times impact on the accuracy of the estimation.The simulation results agree with the theoretical derivation,which verify that the accuracy can be assured by increasing accumulation times under the noise environment.Compared with the traditional carrier to noise ratio estimation algorithm,the method consumes shorter time with good accuracy.Also the minimum cumulative number to meet accuracy requirements can increase the flexibility of the algorithm by adjusting estimation update time adaptively.
引文
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[2]陈杰,巴晓辉,刘海洋,等.一种有效的GNSS接收机载噪比估计方法[J].武汉大学学报:信息科学版,2011(4):457-460.
[3]叶甜春,何文涛,徐建华.GPS弱信号的自适应载噪比估计算法[J].电子技术应用,2010(6):111-114.
[4]Pauluzzi D R,Beaulieu N C.A comparison of SNR estimation techniques for the AWGN channel[J].IEEE Transactions on Communications,2000,48(10):1681-1691.
[5]Satyanarayana S,Borio D Lachapelle G.C/N0 estimation:design criteria and reliability analysis under global navigation satellite system(GNSS)weak signal scenarios[J].IET Radar,Sonar and Navigation,2012,6(2):81-89.
[6]Muthuraman K,Borio D.C/N0estimation for modernized GNSS signals:theoretical bounds and a novel iterative estimator[J].Navigation,2010,57(4):309-323.
[7]Groves P D.GPS signal to noise measurement in weak signal and high interference environments[J].Measurement,2005,12(13):14.
[8]Sharawi M S,Akos D M,Aloi D N.GPS C/N0estimation in the presence of interference and limited quantization levels[J].IEEE Transactions on Aerospace and Electronic Systems,2007,43(1):227-238.
[9]Cioni S,Corazza G E,Bousquet M.An analytical characterization of maximum likelihood signal-to-noise ratio estimation[C]//2nd International Symposium on IEEE Wireless Communication Systems,2005:827-830.
[10]郑霖.自适应降低复杂度的预均衡最大似然序列检测[J].桂林电子科技大学学报,2011,31(4):266-269.
[11]张松林,张昆.连续随机变量非线性函数的期望和方差的近似求法[J].大地测量与地球动力学,2008 28(4):107-110.