Receive antenna selection for MIMO-SM systems with linear MMSE receivers in the presence of unknown interference

In this paper, a novel receive antenna subset selection technique is proposed for multiple input multiple output spatial multiplexing (MIMO-SM) systems with linear minimum mean square error (MMSE) receivers in the presence of unknown co-channel interference. This antenna selection technique is directly implemented based on training sample sequence by utilizing backward greedy algorithm (BGA) under the least squares (LS) criterion. In the case of practical implementation. Diagonal loading (DL) technique is incorporated into the selection process to insure robustness of antenna selection given limited training sample support. Simulation results show that the proposed antenna selection technique is able to retain the diversity order of a full complexity system in the presence of unknown multiple access interference (MAI)     

Adaptive narrowband interference rejection in DS-CDMA systems: ascheme of parallel interference cancellers

In the presence of narrowband interference (NBI), the performance of the direct-sequence code-division multiple access communication system can be improved by using various interference cancellation schemes. In this paper, a scheme of parallel interference cancellers (PICs), which includes a set of NBI cancellation filters and a set of multiple access interference (MAI) cancellation filters, is developed to improve the signal-to-interference ratio (SIR) and handle the MAI effect. In order to avoid performance deterioration due to unreliable initial detection, a robust coefficient γ is introduced in our proposed design criterion. A recursive least-square algorithm is employed to update the tap coefficients of the PICs. In other words, no training or retraining period is needed in our proposed PICs. Finally, the SIR performance of the proposed detector is analyzed and compared to that of the conventional linear detector     

Least squares-based receive antenna selection for MIMO spatial multiplexing systems with linear receivers

In this letter, a novel receive antenna selection technique is proposed for multiple input multiple output (MIMO) spatial multiplexing systems with linear receivers in the presence of unknown interference. This antenna selection technique is directly implemented based on training sample sequence under the least squares (LS) criterion. It avoids the channel estimation and retain the diversity benefit by antenna selection in the presence of unknown multiple access interference (MAI). In addition, practical implementation with manageable complexity is made possible by extending the fast backward greedy algorithm (BGA) into the proposed antenna selection algorithm.     

Methods of Forming Classified Training Sample for Adaptation of Weight Coefficient of Automatic Interference Compensator

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.     

Multi‐group linear turbo equalization with intercell interference cancellation for MC‐CDMA cellular systems

In this paper, we investigate multi‐group linear turbo equalization using single antenna interference cancellation (SAIC) techniques to mitigate the intercell interference for multi‐carrier code division multiple access (MC‐CDMA) cellular systems. It is important for the mobile station to mitigate the intercell interference as the performance of the users close to cell edge is mainly degraded by the intercell interference. The complexity of the proposed iterative detector and receiver is low as the one‐tap minimum mean square error (MMSE) equalizer is employed for mitigating the intracell interference, while a simple group interference canceller is used for suppressing the intercell interference. Simulation results show that the proposed iterative detector and receiver can mitigate the intercell interference effectively through iterations for both uncoded and coded signals. Copyright © 2009 John Wiley & Sons, Ltd.     

Application of matrix pencil method for estimating natural resonances of scatterers

The matrix pencil (MP) method has been utilised for estimating the poles from the IFFT of calculated frequency responses. The novelty is that the optimal choice of pencil parameters in MP is given, and a scheme for adaptive selection of frequency sampling interval is proposed. Lastly, poles of a complex target are calculated by the proposed method and compared with other available data     

CFE下FRESH滤波器性能分析及CFE校正

频移(FRESH)滤波器的研究通常都基于接收机准确知道信号或干扰循环频率(CF)的假设,但在FRESH滤波器的实际应用环境中,循环频率误差(CFE)往往不可避免地存在。该文基于FRESH滤波器抑制DSSS/BPSK系统窄带干扰的模型,分析了CFE对FRESH滤波器抽头系数、估计误差和系统误码性能的影响,提出了一种改进的CFE校正算法。理论分析与数值仿真的结果表明,FRESH滤波器的性能对CFE十分敏感,该文提出的算法能有效地校正CFE,使FRESH滤波器在CFE下仍能保持稳健而优良的性能。     

Coherent orthogonal filter using pilot symbol-assisted channelestimation for DS-CDMA

A coherent orthogonal filter (COF) using pilot symbol-assisted channel estimation is proposed for DS-CDMA cellular mobile radio. In the proposed scheme, a complex fading envelope in the multi-path environment is estimated using pilot symbols, and tap coefficients of orthogonal filter are controlled for maximising the signal to interference ratio (SIR) of a RAKE combined signal. Computer simulation results show that the required E_b/N₀ of the proposed COF is reduced by ~10.0 dB compared to conventional matched filter receiver at an average BER of 3×10² when there are 10 users and processing gain is 31     

Tapping signal power on 12 μm-thick SOI optical waveguide for performance monitoring

The multimode interference S-bend tap based on the mode-shifting and self-imaging property is proposed to obtain a 5.5% coupling ratio and 20.6 dB polarisation-dependent loss on 12 μm-thick silicon-oninsulator optical waveguides for performance monitoring.     

自适应核协同表示在SAR目标识别中的应用

针对合成孔径雷达(Synthetic Aperture Radar,SAR)目标识别中方位角差距大的训练样本之间存在干扰的问题,对传统协同表示字典进行了改进,得到更适应于当前测试样本且能够降低弱相关原子对系统影响的自适应字典,基于此提出了一种自适应原子选择的核函数变换协同表示算法,并在美国DARPA中的运动和静止目标获取与识别计划公开发布的SAR图像数据库上进行了验证实验.实验结果表明,相较于基于全部训练样本字典的核协同表示模型,基于自适应原子选择的核协同表示方法降低了干扰原子的不良影响,提高了对SAR目标识别的可靠性和鲁棒性.     

Performance evaluation of spatially multiplexed MIMO systems with subset antenna transmission in interference limited environments

Transmit antenna selection in spatially multiplexed multiple-input multiple-output (MIMO) systems is a low complexity low-rate feedback technique, which involves transmission of a reduced number of streams from the maximum possible to improve the error rate performance of linear receivers. It has been shown to be effective in enhancing the performance of single-user interference-free point-to-point MIMO systems. However, performance of transmit antenna selection techniques in interference-limited environments and over frequency selective channels is less well understood. In this paper, we investigate the performance of transmit antenna selection in spatially multiplexed MIMO systems in the presence of co-channel interference. We propose a transmission technique for the downlink of a cellular MIMO system that employs transmit antenna selection to minimize the effect of co-channel interference from surrounding cells. Several transmit antenna selection algorithms are proposed and their performance is evaluated in both frequency flat and frequency selective channels. Various antenna selection algorithms proposed in the literature for single user MIMO links are extended to a cellular scenario, where each user experiences co-channel interference from the other cells (intercell interference) in the system. For frequency selective channels, we consider orthogonal frequency division multiplexing (OFDM) with MIMO. We propose a selection algorithm that maximizes the average output SINR over all subcarriers. A method to quantify selection gain in frequency selective channel is discussed. The effect of delay spread on the selection gain is studied by simulating practical fading environments with different delay spreads. The effect of the variable signal constellation sizes and the number of transmitted streams on the bit error rate (BER) performance of the proposed system is also investigated in conjunction with the transmit antenna selection. Simulation results show that for low to moderate interference power, significant improvement in the system performance is achievable with the use of transmit antenna selection algorithms. Even though the gain due to selection in frequency selective channels is reduced compared to that in flat fading channels due to the inherent frequency diversity, the performance improvement is significant when the system is interference limited. The performance improvement due to reduced number of transmit streams at larger signal constellation sizes is found to be more significant in spatially correlated scenarios, and the gain due to selection is found to be reduced with the increased delay spread. It is found that employing transmit antenna selection algorithms in conjunction with adaptation of the number of transmitted streams and the signal constellation sizes can significantly improve the performance of MIMO systems with co-channel interference.     

Design of Automatic Equalizer Including a Decoder of Error-Correcting Code

A new proposed automatic equalizer including a decoder of error-correcting code (AEDEC) is obtained by the joint adaptive operation of an automatic equalizer and a decoder. This AEDEC can reduce misadjustment of tap values and error propagation owing to decision errors, and stabilize convergence even without a known training signal in noisy channels.     

Effects of CIR selection diversity with two correlated branches in the m-fading channel

A number of methods for the measurement of channel impulse response (CIR) (desired signal carrier power to interference ratio) have been proposed in cellular mobile radio systems. The paper estimates the probability of cochannel interference for CIR selection diversity having two correlated branches in the m-fading channel. The advantage of CIR selection diversity over selection diversity based on the desired signal power algorithm is confirmed.     

一种移动P2P网络环境下的动态安全信任模型

信任是移动对等(MP2P)网络安全中首要解决的关键技术问题.由于MP2P网络环境与P2P网络环境有本质的区别,因此现有P2P网络信任模型并不适用于MP2P网络环境.本文提出一种适合MP2P网络环境的动态安全信任模型DSTM_MP2P.DSTM_MP2P包括两种方案,一种是针对节点的信任信息已知或部分已知的情况,提出基于节点行为的节点类型识别机制;另一种是针对节点的信任信息未知的情况,提出基于贝叶斯博弈的节点概率选择策略.通过理论分析和实验证明,无论MP2P网络环境如何,DSTM_MP2P模型使得请求节点总是优先连接安全可靠的节点,从而极大地提高了下载成功率.     

扩频通信中干扰抑制的自适应非线性滤波技术

本文研究了自适应非线性滤波在直扩通信中抑制窄带干扰的应用，修正了Ｖｉｊａｙａｎ和Ｐｏｏｒ所采用的抽头更新算法，使非线性滤波的性能明显改善，同时把自适应非线性横向滤波结构，推广到Ｌａｔｔｉｃｅ结构，提高了收敛速度。     

Adaptive equalization and interference cancellation for wirelesscommunication systems

An adaptive equalization and interference cancellation method is proposed. The proposed scheme can cancel both intersymbol interference and cochannel interference, and is blind in the sense that no knowledge of the training sequences of the interfering users is required. In particular, it is a maximum likelihood sequence estimation (MLSE) equalizer that is implemented by the generalized Viterbi algorithm (GVA) with an RLS-based channel estimator. To demonstrate the potential of the proposed method, various simulation results over a frequency selective Rayleigh fading environment in the presence of cochannel interference are presented. In addition, a sequential algorithm is introduced to reduce the computational complexity of GVA     

Neural-network-based maximum-power-point tracking of coupled-inductor interleaved-boost-converter-supplied PV system using fuzzy controller

The photovoltaic (PV) generator exhibits a nonlinear V-I characteristic and its maximum power (MP) point varies with solar insolation. In this paper, a feedforward MP-point tracking scheme is developed for the coupled-inductor interleaved-boost-converter-fed PV system using a fuzzy controller. The proposed converter has lower switch current stress and improved efficiency over the noncoupled converter system. For a given solar insolation, the tracking algorithm changes the duty ratio of the converter such that the solar cell array voltage equals the voltage corresponding to the MP point. This is done by the feedforward loop, which generates an error signal by comparing the instantaneous array voltage and reference voltage corresponding to the MP point. Depending on the error and change of error signals, the fuzzy controller generates a control signal for the pulsewidth-modulation generator which in turn adjusts the duty ratio of the converter. The reference voltage corresponding to the MP point for the feedforward loop is obtained by an offline trained neural network. Experimental data are used for offline training of the neural network, which employs a backpropagation algorithm. The proposed peak power tracking effectiveness is demonstrated through simulation and experimental results. Tracking performance of the proposed controller is also compared with the conventional proportional-plus-integral-controller-based system. These studies reveal that the fuzzy controller results in better tracking performance.     

一种抗飞行器衰落的定时恢复技术研究

对流层散射通信信道是时变多径信道,当飞行器经过散射公共体时会导致飞行器衰落。为了对抗飞行器衰落,在研究自适应均衡算法的基础上,提出在定时恢复环路中采用抽头跟踪定时误差检测算法。通过自适应均衡算法消除码间干扰、跟踪信道变化,定时误差检测算法跟踪均衡器抽头的变化情况进行定时恢复,从而使采样时刻位于最佳位置。仿真结果表明,该方法能够对抗飞行器衰落,实现定时恢复。     

Channel‐power profile estimation for orthogonal frequency‐division multiplexing systems

In this work, a channel‐power profile estimation for orthogonal frequency‐division multiplexing systems, based on the cyclic prefix (CP), is introduced. By knowing the delay of each path, the time‐dispersion information can be derived. The proposed method, considering long intersymbol interference (ISI) fading channels, requires only the coarse symbol timing information. More specifically, quasi‐stationary fading channels are considered. The basic contribution is to obtain the maximum‐likelihood estimation of the correlation coefficient based on the CP. Subsequently, the relationship between the correlation coefficient and the channel‐tap powers is explored. With the estimate of correlation coefficient, the least‐square solution of the channel‐tap powers can be determined. The proposed method is suitable for both short and long ISI channels. Furthermore, the Cramér–Rao lower bound of the channel‐power profile estimation is analyzed, and simulations confirm the advantages of the proposed estimator. Copyright © 2011 John Wiley & Sons, Ltd.     

5G下行CoMP技术研究及测试验证

对于同频干扰严重的重叠覆盖场景,CoMP可提高边缘用户SINR,降低小区间干扰,提高边缘用户的吞吐率.对下行CoMP技术进行介绍,并重点介绍了5G下行CoMP与技术与LTE下行CoMP的主要差异,5G下行CoMP JT的基本原理以及具体的实现流程.针对2种场景,对5G下行CoMP JT技术进行了性能验证及分析.测试结果...