共查询到20条相似文献,搜索用时 31 毫秒
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The requirement to suppress narrowband interferences in CDMA communications stems from the overlay concept, i.e., coexistence of different types of signals in the same frequency band. The conventional approach to rejecting the narrowband interferences has been to whiten the received signal containing the interference, prior to spread spectrum demodulation. In this paper, it is proposed to achieve the interference rejection through spatial processing. The main benefit of this approach is its robustness with respect to the interference bandwidth. Stepping up from single domain spatial processing to space-time processing provides degrees of freedom for both overlay interference cancellation and diversity combining. Two space-time architectures, cascade and joint-domain, are studied and compared to a Rake receiver preceded by a whitening filter. Main contributions of the paper are the development of analytical expressions of (1) the efficiency of each method, (2) the p.d.f.'s of the output SNR in a Rayleigh fading environment, and (3) the error probability associated with each method. The analysis therein demonstrates that the joint-domain architecture outperforms the cascade configuration, which in turn is superior to the whitening filter-Rake combination. 相似文献
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The problem of analyzing various methods for the formation of the classified training sample that ensure the effective operation of the automatic compensator for active interferences with simultaneous presence of passive interference is solved in this paper. For the first time an adaptive method for the formation of the classified training sample based on the use of threshold estimation of the interchannel correlation coefficient of the combined interference is proposed. An adaptive method for the formation of the classified training sample based on the current interval estimation of the distribution of the passive component of the combined interference in range (time) is also proposed. The method provides an estimation of the coefficient of interchannel correlation with the selection of the maximum value and its utilization for the formation of weight coefficients in the following probing period. Experiment in the testing ground is conducted with a quantitative estimation of the cancellation ratio of active interference for the formation of the classification sample using spectral differences in the structure of active and passive interferences. 相似文献
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Jing-Ran Lin Qi-Cong Peng Huai-Zong Shao Tai-Liang Ju 《中国电子科技》2007,5(2):175-179
A novel approach of unitarily interpolated array MVDR (UIA-MVDR) is proposed, aiming at avoiding the signal cancellation caused by broadband signal-correlated interferences. UIA-MVDR belongs to the classic approaches of spectral averaging. However, it is distinguished from the conventional interpolated array MVDR (IA-MVDR) by two points: 1) It imposes a unitary constraint on the transform matrices. 2) It only optimizes the worst-case performance of array manifold approximation. As a result, the restriction on the order of Bessel function expansion is released, so that very accurate approximation can be achieved even in the case of small or middle arrays. Compared with many related approaches, UIA-MVDR destroys the correlation more completely and then achieves better performance. Its excellent performance in both correlated and uncorrelated broadband interferences suppression is confirmed via a n umber of numerical examples. 相似文献
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Xin Guo Hongbo Sun Tat Soon Yeo 《Geoscience and Remote Sensing, IEEE Transactions on》2008,46(7):1879-1891
The performance of high-frequency surface wave radar (HFSWR) is known to suffer from external environmental interference and noise, such as cochannel radio-frequency interference from other radiating source, ionospheric clutter, lightning impulsive noise, etc. This paper experimentally evaluates the interference cancellation performance of various adaptive beamforming schemes with respect to the aforementioned three types of interferences in an attempt to find the most promising adaptive cancellation scheme in practical HFSWR environment. 相似文献
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The performance of a successive concatenated cancellation scheme for code-division multiple-access (CDMA) uplink transmission in cellular mobile radio is presented. Both serial and parallel cancellation stages are employed. The serial cancellation stage is first used to obtain initial data estimates followed by the parallel cancellation stages to enhance the accuracy of the estimates. The performance of this scheme is evaluated via analysis and simulation. In our analysis, we develop a model to consider the impact of wrongly estimating the phase and amplitude of the channel impulse response on the successive concatenated cancellation scheme. Analysis and simulation results in flat Rayleigh fading asynchronous channels with both perfect and nonperfect channel estimation and with perfect ranking confirms the accuracy of our analytical model as well as the significant improvement in performance compared to the conventional single-user matched filter (MF) detection and the stand-alone parallel cancellation schemes. Analytical results also show that the concatenated scheme has the potential to reach the single-user performance bound for a wide range of user base size, up to K=120 users, with a processing gain of 127 using one serial and three parallel cancellation stages. Finally, we propose a method whereby the receiver adapts with the number of users in order to retain the bit error ratio (BER) performance while decreasing the processing delay 相似文献
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为了破解雷达主瓣干扰尤其是多个主副瓣干扰同时抑制的难题,该文利用目标极化散射特性在不同入射角存在差异而干扰近似相同的特点,将极化信息应用到机载双基地雷达,通过构建机载双基地极化敏感阵列来实现主副瓣干扰抑制。该方法主要通过双基地-极化分级抑制来实现。首先重构协方差矩阵遮蔽主瓣干扰来分别抑制双基地主辅雷达副瓣干扰,然后将辅雷达接收数据时域对齐后送主雷达,最后修正主辅雷达主瓣干扰导向矢量,并利用极化对消实现主瓣干扰抑制。仿真结果表明:利用双基地-极化分级抑制方法可实现多个主副瓣干扰同时抑制,大幅提升雷达系统抗干扰能力。 相似文献
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The requirement to suppress narrowband interferences in CDMA communication stems from the overlay concept, i.e., coexistence of different types of signals in the same frequency band. This paper describes the performance analysis of a direct-sequence (DS) CDMA personal communication system sharing a common spectrum with narrowband microwave radio links in the 1.85 to 1.99 GHz band. The coexistence of these two systems within the same frequency band will improve the overall spectrum efficiency, but will also cause interference to both systems. In this paper it is shown that joint spatial and temporal optimum combining provides an efficient means of improving the performance of the DS-CDMA system through cancellation of the narrowband signal and the co-channel interferences. The proposed space-time architecture provides degrees of freedom for both diversity and interference cancellation. It is shown that the joint space-time receiver is robust with respect to the narrowband interference signal bandwidth and its carrier frequency offset from the DS-CDMA carrier frequency. 相似文献
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信号间的互相关干扰导致对期待信号的部分抵消.针对这种情况,提出了内插酉阵列最小均方无畸变响应(UIA-MVDR)宽带自适应波束形成技术以抑制这种干扰从而获取所需信号.UIA-MVDR不受贝塞尔函数展开阶数的限制,使得即使在中小规模阵列情形下,也能获得很精确的阵列流型逼近.相对于传统方法而言,UIA-MVDR能更好地消除互相关干扰.仿真实验表明它具有更佳的性能. 相似文献
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针对多径干扰对频率选择性信道下伪码捕获性能的影响,提出了一种基于自动删除算法的PN码捕获方法。该串行相关捕获系统通过一个基于排序数据方差的自动删除单元平均恒虚警检测器来删除参考滑窗中的干扰样本,并且不需要多径干扰数目的先验信息。对系统的平均捕获时间及检测性能进行了计算与仿真,与传统的自适应捕获方法相比,改进后捕获算法的性能得到较大的改善。 相似文献
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提出一种基于总体最小二乘(TLS)的外辐射源雷达直达波相消算法,该算法首先利用TLS获取直达波的数目和时延,再基于既得的直达波信息构建直达波子空间,最后将回波向该空间投影实现直达波相消。与传统扩展相消算法相比,该算法所构建的直达波子空间阶数低,精确度高,在相关处理时间较短或直达波幅度时变的情况下,仍具有良好的直达波抑制性能。仿真结果证实了算法的有效性。 相似文献
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Kyungjung Kim Sarkar T.K. Hong Wang Salazar-Palma M. 《Antennas and Propagation, IEEE Transactions on》2004,52(2):533-541
The purpose of this paper is to estimate the direction of arrival (DOA) of the signal of interest (SOI) in the presence of both coherent and noncoherent interferences and multipath components utilizing a combined temporal and spatial processing technique based on a direct data domain approach. The concept of cyclostationarity, which deals with the temporal information of the SOI, is used to extract signals having the same cycle frequency and out the co-channel interferences and additive noise. Hence, the signal detection capability can be significantly increased over conventional filtering when the length of the data record is limited. The main contribution of the paper is that by combining temporal and spatial processing based on a direct data domain approach one can handle number of signals along with their various coherent and noncoherent multipaths and interferences which can exceed the number of antenna elements. Hence, this methodology may be advantageous over conventional spatial processing when the number of degrees of freedom can never exceed the number of antenna elements in the array. However, the number of multipaths and interferers at the same cycle frequency has to be less than approximately 66 % of the antenna elements. Since we do not form a covariance matrix of the data, this method is quite suitable for short data lengths or when the environment is quite dynamic. Hence, in the proposed algorithm, while the estimation of the cyclic array covariance matrix is avoided, we develop a new matrix form using extremely short data samples. As a result, the computational load in the proposed approach is relatively reduced and the robustness of the estimation of SOI is significantly improved when the number of available snapshots is extremely limited. Numerical results are presented to illustrate the efficiency and accuracy of this method. 相似文献
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Space-time multiuser detection in multipath CDMA channels 总被引:3,自引:0,他引:3
The problem of multiuser detection in multipath CDMA channels with receiver antenna array is considered. The optimal space-time multiuser receiver structure is first derived, followed by linear space-time multiuser detection methods based on iterative interference cancellation. Blind adaptive space-time multiuser detection techniques are then proposed, which require prior knowledge of only the spreading waveform and the timing of the desired user's signal. Single-user-based space-time processing methods are also considered and are compared with the multiuser approach. It is seen that the proposed multiuser space-time processing techniques offer substantial performance gains over the single-user-based methods, especially in a near-far situation 相似文献
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Improved parallel interference cancellation for CDMA 总被引:2,自引:0,他引:2
This paper introduces an improved nonlinear parallel interference cancellation scheme for code-division multiple access (CDMA) that significantly reduces the degrading effect on the desired user of interference from the other users that share the channel. The implementation complexity of the scheme is linear in the number of users and operates on the fact that parallel processing simultaneously removes from each user a part of the interference produced by the remaining users accessing the channel the amount being proportional to their reliability. The parallel processing can be done in multiple stages. The proposed scheme uses tentative decision devices at the multiple stages to produce the most reliably estimated received data for generation and cancellation of user interference. Simulation results are given for a multitude of different situations, in particular, those cases for which the analysis is too complex 相似文献
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Maximum number of users in a Code Division Multiple Access (CDMA) system, disregarding the type of used signature sequences, is equal to the processing gain; but in overloaded CDMA systems, it is tried to use some special methods of applying signature sequences so that the number of users exceeds the processing gain of the system. This growth in capacity is gain at the cost of decrease in performance of the conventional systems; and usually it is tried to use channel coding methods or multi-user detectors to compensate this decrease. Because of advantages of using coding methods joined with multiuser detectors in achieving better performance and also because of some benefits of using (Low Density Parity Check) LDPC method in comparison with similar capacity achieving coding methods, in this article, an iterative multi-user detector for an overloaded LDPC Coded CDMA system is proposed. This receiver consists of a combination of matched filters in the first stage and a linear (Minimum Mean Square Error) MMSE detector and an Interference Cancellation (IC) scheme in the successive stages. In the suggested method, a bank of LDPC decoders gives the soft information to the IC blocks, which help for the better interference cancellation. Comparing the performance of the proposed system with that of Turbo coded system shows that the proposed system, in addition to advantages of using LDPC codes instead of Turbo codes, has better bit error rate performance. 相似文献