低复杂度的时域同步OFDM信号检测算法

构造一种在所有正交频分复用(OFDM)符号中使用同一PN序列作为保护间隔的时域同步OFDM信号格式,提出一种基于快速傅里叶变换的PN码干扰消除和信号检测算法,该算法不使用FIR均衡技术,复杂度低,仅与常规CP-OFDM信号检测算法的复杂度相当,但由于引入了部分保护间隔内的噪声,因此BER性能不如CP-OFDM系统。仿真结果表明,在典型的双径短波信道中,两者的BER性能差距小于0.1 dB,在信道时域扩展较大的四径短波信道中,两者的BER性能差距小于1 dB。     

扫频干扰的自适应时变抑制研究

在DSSS系统中,提出一种基于修正离散Chirp-Fourier变换(MDCFT)的扫频干扰自适应时变抑制算法。该算法采用MDCFT估计扫频干扰的参数,构造了实时性强的自适应时变干扰剔除器,推导了MDCFT检测扫频干扰的输出信噪比的闭合表达式。与Wigner-Hough变换(WHT)估计扫频干扰时的非线性损失相比,输出信噪比提高了3 dB,并给出了误码率的闭合表达式。数值仿真表明了理论分析的正确性和该方法的有效性。     

基于CME算法的数字窄带干扰抑制及改进

用连续均值剔除干扰(Consecutive mean excision,CME)算法可以抑制直扩系统中的数字窄带干扰,通过迭代更新门限值,可抑制50%带宽的数字窄带干扰.针对CME算法计算量大的缺点,利用FFT幅度谱的中心对称特性,提出了一种改进的更易于工程实现的CME算法.与常规的CME算法相比,改进的CME算法仅对部分幅度谱进行迭代更新,在减少运算量和节省存储空间的同时,能够保持良好的抑制性能.理论分析和数字仿真表明,改进算法可有效地抑制直扩通信系统中的数字窄带干扰,且实现简单.     

New Technique for Estimating and Suppressing Narrowband Interference in DSSS Systems

A generalized approach for narrowband interference （NBI） suppression in direct sequence spread spectrum （DSSS） communication systems using adaptive infinite impulse response （IIR） filter is presented. The excision filter coefficients depend on both the jammer power and its instantaneous frequency. The dependency of the filter construction on the jammer power is significant as it allows optimal tradeoff between interference removal and signal distortion by maximizing the receiver signal to noise ratio improvement（SNRI）. Instead of traditional adaptive line enhancer （ALE） estimator, a preferable NBI estimator-Fourier interpolation estimator （FIE） is proposed. Closed-form expressions of the SNR improvement and theoretical bit error rate （BER） based on the assumption that the output of the correlator is Gaussian distributed are both derived. Performance results obtained by numerical simulation are also presented and compared with theoretical results.     

Improved Interference Suppression Algorithm Against Broadband BPSK Interference

An improved polar exciser(IMPE)interference suppression method against broadband constant envelope binary phase shift keying(BPSK)interference is proposed.The disadvantage of traditional polar exciser(PE)is the performance degradation when the power of interference is low,i.e.,the threshold effect.The proposed improved PE(IMPE)algorithm can overcome the threshold effect of PE by introducing compression gain(CG)metric,which forces PE suppressor active only at larger jammer-to-signal ratio(JSR)and switch to matched filter(MF)at lower JSR.Theoretical analysis and numerical simulations show the exactness of CG as a switching metric and the validity of the IMPE algorithm.