Performance of the Zero Forcing precoding MIMO broadcast systems with channel estimation errors

In this paper, the effect of channel estimation errors upon the Zero Forcing (ZF) precoding Multiple Input Multiple Output Broadcast (MIMO BC) systems was studied. Based on the two kinds of Gaussian estimation error models, the performance analysis is conducted under different power allocation strategies. Analysis and simulation show that if the covariance of channel estimation errors is independent of the received Signal to Noise Ratio (SNR), imperfect channel knowledge deteriorates the sum capacity and the Bit Error Rate (BER) performance severely. However, under the situation of orthogonal training and the Minimum Mean Square Error (MMSE) channel estimation, the sum ca- pacity and BER performance are consistent with those of the perfect Channel State Information (CSI) with only a performance degradation.     

一种新的鲁棒自适应控制器

本文通过引入估计误差符号信息的反馈来建立一种新的鲁棒自适应控制器，能确保存在有界外部干扰时Ｌｙａｐｕｎｏｖ函数对时间的导数的半负定性，从而确保了系统的稳定性，使系统具有较强的鲁棒性，理论分析与仿真结果表明，该鲁棒自适应控制器对有界外部干扰有较强的抑制能力，并且可以加快自适应初始阶段的收敛速度。     

基于瞬时频率的双曲调频信号距离估计误差分析

双曲调频信号的多普勒不变性可使运动目标匹配滤波输出的能量损失达到最小,从而可对运动目标有很高的检测能力,在运动目标检测与参数估计中具有独特优势,但同时也给目标距离的估计带来一定误差。在双曲调频信号模糊函数、多普勒不变性和匹配滤波特性的基础上,对距离分辨力和测距误差进行了分析,提出了基于瞬时频率的距离误差计算公式,可直接应用于目标距离的补偿以及目标跟踪中量测方程的校正,提高声呐的工作性能。     

非理想CSI下MIMO MRC系统多用户分集性能分析*

针对在无线多输入—多输出（MIMO）通信系统的发射端采用波束成形、接收端采用最大比合并的MIMO MRC系统,考虑收发端仅能获得存在信道估计误差的非理想信道信息（CSI）且系统受到共信道干扰这一条件,分析系统的多用户分集性能。导出封闭形式的信号干扰噪声比的概率分布函数表达式和以平均容量的形式给出的系统多用户分集性能表达式。数值仿真证实了理论分析的结果。研究表明,信道估计误差和共信道干扰均会降低系统的多用户分集性能,而信道估计的精度是影响系统多用户分集性能的关键因素。     

水下晃动平台姿态估计精度仿真

根据水下平台晃动的规律建立了晃动模型,对水下晃动平台姿态估计的精度分析展开研究.仿真验证了平台以匀速运动、匀加速运动两种情况下的卡尔曼滤波算法和简化的自适应卡尔曼滤波算法的姿态估计精度.仿真结果表明:匀速运动模式两种算法的估计误差在同一范围内;匀加速运动模式,卡尔曼算法具有更快的收敛速度,而自适应卡尔曼算法的估计方差约为卡尔曼算法的50%以下.     

连续切换非方广义线性系统的观测器设计

针对一类连续切换非方广义线性系统,设计了广义状态观测器,并分析了状态估计误差的稳定性。首先通过矩阵的初等变换将连续切换非方广义线性系统的观测器设计问题转换为连续切换广义线性系统的观测器设计问题,之后设计第i个子系统的子观测器,可根据第i个子观测器构造这个广义切换系统的观测器。当观测器是全维观测器,且每个子系统都可检测时,状态估计误差甚至可以在任意切换下指数收敛到零。最后,通过数值实例和Matlab仿真分析说明了观测器设计方法简单可行,观测误差较其他方法的收敛速度快,证实了该方法的有效性和正确性。     

Optimal pilots design for frequency offsets and channel estimation in OFDM modulated single frequency networks

Optimal pilot design and placement for both the frequency offsets and channel estimation in Orthogonal Frequency-Division Multiplexing modulated Single Frequency Network are treated.Unlike the conventional frequency-domain filter-based algorithms,the proposed pilot of each transmitter can always be demodulated at the receiver even if the received pilots of multiple transmitters are totally overlapped.Although the channel state information is needed in designing the proposed pilot for carrier frequency offset(CFO)estimation,the performance of the proposed CFO estimation is robust to the channel estimation error.The optimal pilot as well as the Least-Squares(LS)channel estimator is also proposed,and the pilot for channel estimation is always a constant-modulus.A joint frequency offset and channel estimation scheme is also proposed,and the transmitters can adaptively optimize their pilots in the successive transmissions using the estimation results feedback in the former transmission.Simulation results demonstrate the performance of the proposed algorithm in terms of frequency offset and channel estimation accuracies.Since multiple copies of the same information can be received at each receiver,some combining technologies such as equal gain combining(EGC)or maximal ratio combining(MRC)can be applied at the receiver to improve the receiving diversity gain.Numerical results show that in a scenario of two transmitters with a Signal-to-Noise Ratio of 20 dB,the Bit Error Rate(BER)of1.5×10-4(or 1×10-4)can be obtained at the receiver using EGC(or MRC),and this BER performance can be improved to be 4×10-6for EGC(or 2×10-6for MRC)by considering three co-receiver transmitters.     

Approximating probability distribution of circuit performance function for parametric yield estimation using transferable belief model

This paper applies the transferable belief model （TBM） interpretation of the Dempster-Shafer theory of evidence to approximate distribution of circuit performance function for parametric yield estimation. Treating input parameters of performance function as credal variables defined on a continuous frame of real numbers, the suggested approach constructs a random set-type evidence for these parameters. The corresponding random set of the function output is obtained by extension principle of random set. Within the TBM framework, the random set of the function output in the credal state can be transformed to a pignistic state where it is represented by the pignistic cumulative distribution. As an approximation to the actual cumulative distribution, it can be used to estimate yield according to circuit response specifications. The advantage of the proposed method over Monte Carlo （MC） methods lies in its ability to implement just once simulation process to obtain an available approximate value of yield which has a deterministic estimation error. Given the same error, the new method needs less number of calculations than MC methods. A track circuit of high-speed railway and a numerical eight-dimensional quadratic function examples are included to demonstrate the efficiency of this technique.     

基于估计误差逆序的VBLAST检测算法研究

为了取得VBLAST系统复杂度与性能的折中,在串行干扰消除检测算法的基础上提出一种按估计误差从大到小排序并与最大似然检测算法相结合的检测算法.该算法的排序方式能够保证后面检测层的可靠度逐渐增加,对首层进行最大似然检测能提高首层的性能从而遏制误码传播问题;或者对首层进行假设,检测出所有信号后择优选取作为最后的检测输出来提高系统整体性能.仿真结果表明,不管是快衰落瑞利信道还是空间相关信道,新算法复杂度与传统排序串行干扰消除算法复杂度相当或略有增加,而误码率更低,性能明显改善,更适合于VBLAST系统的信号检测.     

永磁同步电机无位置估计误差的滑模观测器无速度传感器控制方法

传统滑模观测器(SMO)无速度传感器控制方法在电机的运行速度出现较大变化时,对位置的估计会出现稳态误差。为了消除位置的估计误差,提出了一种带有反动电势修正的SMO无速度传感器控制方法。反电动势的修正律基于永磁同步电机(PMSM)的d-q轴电流模型。即使电机运行在速度大幅波动的情况下,也能保持位置估计误差为零,且该方法计算增量较小,易于实现。将所提出的方法在1台1.5 kW的PMSM上进行了仿真和试验,结果验证了位置估计误差能有效地收敛至零。