A Reduced Complexity Time-Delay Tracking and Channel Estimation for OFDM Systems

Introduction OFDM[1]is a special case of multicarrier trans-mission, where a single datastream is transmittedover a number of orthogonal subcarriers. Becausethe symbol duration increases for the lower rateparallel subcarriers, the relative amount of disper-sion in time caused by multipath delay spread is de-creased. Intersymbol interference is eliminated al-most completely by introducing a guard time in ev-ery OFDM symbol. Due to these advantages,OFDM is widely exploited for the communica…     

Fast affine projection algorithm for adaptive noise canceling and its application on the fetal electrocardiogram extraction

Aimed at the problem of adaptive noise canceling (ANC), three implementary algorithms, which are least mean square (LMS) algorithm, recursive least square (RLS) algorithm and fast affine projection (FAP) algorithm, have been researched. The simulations were made for the performance of these algorithms. The extraction of fetal electrocardiogram (FECG) is applied to compare the application effect of the above algorithms. The proposed FAP algorithm has obvious advantages in computational complexity, convergence speed and steadystate error.     

Lattice-basis reduction precoding based on successive interference cancellation design for multiuser MIMO downlink system

Two kinds of lattice-basis reduction precoding schemes based on successive interference cancellation are proposed. The successive interference cancellation (SIC) structure can be obtained by either orthogonal and a right triangular matrix (QR) decomposition, or the Vertical Bell Labs Layered Space Time (VBLAST) algorithm which provides optimal user ordering. Moreover, the extended channel approach is applied to the proposed SICbased schemes. Simulation results show that the proposed schemes can achieve comparable BER performance to vector precoding (VP).     

Pragmatic physical layer abstraction method based on bit-LLR-wise exponential effective SNR mapping for bit interleaved coded orthogonal frequency division multiplexing system

In this paper, we analyze the physical layer abstraction for bit interleaved coded orthogonal frequency division multiplexing （BIC-OFDM） system from a parallel bit channel perspective. By combining the exponential effective SNR （signal-to-noise ratio） mapping （EESM） with the maximum a posteriori （MAP） algorithm, a bit LLR （log-likelihood ratio） wise EESM （BL-EESM） method is proposed. This method can abstract the link performance with high accuracy, especially for the case when channel estimation is imperfect. Afterward, the BL-EESM method is simplified by utilizing the non-linear quantization idea, which can reduce the times of exponential operation by two orders of magnitude at wide system bandwidth, yet shows little loss in accuracy. Our proposal can be applied to both system level simulations to save the time consumption and to practical terminals to facilitate the adaptive modulation and coding （AMC） procedure, bringing about throughput improvement at low hardware cost.     

Micro-electro-mechanical-sensor inertial navigation system-assisted global navigation satellite system receiver acquisition scheme and performance evaluation

When an aircraft moves under a low carrier-to-noise ratio (CNR) or at a high speed, increasing the sensitivity of global navigation satellite system (GNSS) receiver is a goal quite hard to achieve. A novel acquisition scheme assisted with micro-electro-mechanical-sensor (MEMS) inertial navigation system (INS) is presented to estimate the Doppler caused by user dynamics relative to each satellite ahead of time. Based on tightly coupled GNSS/INS estimation algorithm, MEMS INS Doppler error that can be achieved is first described. Then, by analyzing the mean acquisition time and signal detection probability, the MEMS INS-assisted acquisition capabilities in cold, warm and hot starts are quantitatively determined and compared with the standard GNSS acquisition capability. The simulations and comparisons have shown that: the acquisition time in cold start can be shortened by at least 23 s, the time in warm start can be shortened to 1 s and the acquisition capability is improved 95%, and the reacquisition time in hot start can be shortened by around 0.090 s and the capability can be enhanced 40%. The results demonstrate the validity of the novel method.     

Robust ergodic rate transmission for time division duplex beamforming systems

In time division duplex(TDD)beamforming systems,the base station estimates the channel state information(CSI)at transmitter based on uplink pilots and then uses it to generate the beamforming vector in the downlink transmission.Because of the constraints of the TDD frame structure and the uplink pilot overhead,there inevitably exists CSI delay and channel estimation error between CSI estimation and downlink transmission channel,which would degrade system ergodic rate.In this paper,we propose a robust ergodic rate transmission scheme,in which the uplink pilot time interval(UPTI)of an active user is adaptively adjusted according to the changing channel conditions such as Doppler frequency shift,uplink pilot signal to noise ratio(SNR),to minimize the impact of CSI delay and channel estimation error on the ergodic rate of TDD beamforming systems.In order to get the optimal UPTI,we first derive the average post-processing SNR for TDD beamforming systems with channel estimation error and CSI delay.We then obtain the optimal UPTI,which maximizes the average post-processing SNR,given the normalized pilot overhead(the number of pilot symbols per data symbol).The numerical simulation results validate that the the proposed robust ergodic rate transmission scheme not only maximizes the average post-processing SNR but also maximizes the system ergodic rate.Moreover,the scheme can adapt well to the changing channel environments compared with the current fixed UPTI scheme.Especially our research is valuable for the uplink sounding reference signal design in long term evolution advanced(LTEAdvanced)system.     

MVB-Ethernet网关设计与时延分析

分析了一种多功能车辆总线和工业以太网协议转换网关,软硬件设计方案及其实现原理,该设备具有以太网和MVB跨总线通信能力,通过网络配置灵活的支持MVB过程数据,消息数据和以太网通信.分析了影响网关实时性的关鍵因子TCP时延,为了控制网络时延,分析和对比了3种不同的改进方案的实时性能,并对最优方案进行了时延计算和实验验证,实验结果满足列车网络通信实时性要求.     

Joint user and antenna selection for multiuser MIMO downlink with block diagonalization

User selection is necessary for multiuser multiple-input multiple-output (MIMO) downlink systems with block diagonalization (BD) due to the limited free spatial transmit dimensions. The pure user selection algorithms can be improved by performing receive antenna selection (RAS) to increase sum rate. In this paper, a joint user and antenna selection algorithm, which performs user selection for sum rate maximization in the first stage and then performs antenna selection in the second stage, is proposed. The antenna selection process alternately drops one antenna with the poorest channel quality based on maximum determinant ranking (MDR) from the users selected during the first stage and activates one antenna with the maximum norm of projected channel from the remaining users. Simulation results show that the proposed algorithm significantly outperforms the algorithm only performing user selection as well as the algorithm combining user selection with MDR receive antenna selection in terms of sum rate.     

电磁干扰对电力线网络的传输质量与频谱的影响

电力线通信（Power-Line Communication,PLC）系统是利用信号耦合的方式,将载波耦合到AC电力线的弦波信号上,经由电力线来传输网络数据.本文主要探讨常见的家电用品对PLC系统的影响.量测工具使用LabVIEW软件来撷取数据,针对距离、电器设备差异计算信噪比（SNR）、信道频率响应（CFR）以及上传/下载速度对通信质量影响.由量测的结果得知,目前PLC系统所遇到的衰减问题大多与外界的噪声大小或与AC传输线的距离有关,经由量测的资料结果可以当作改善PLC系统效能的依据.     

一种在CDMA辅助下实现WLAN无缝切换的机制

随着无线局域网（WLAN）技术的发展,越来越多的用户可以在移动过程中通过WLAN获得网络接入服务,这就需要对WLAN切换的支持,而单纯基于接收信号强度（RSS）的切换机制难以克服乒乓效应及其他一些服务质量下降问题.本文提出一种CDMA辅助下的WLAN无缝切换（即低延时、低丢包率）机制（CAHO）,该机制在用户发生相邻WLAN之间的切换过程中使用CD-MA连接来避免性能下降问题.为了评价该机制,我们建立一个实验床,并与传统的WLAN切换机制及Multiscan切换机制进行了比较.实验结果表明,CAHO机制能够有效地解决丢包、服务中断及乒乓切换等问题.     

Robust optimization for the correlated MIMO downlink with imperfect channel state information

To reduce the performance deterioration induced by imperfect channel state information (CSI) in cor-related multiple input multiple output(MIMO) downlink, the linear transmit/receive filters should be optimized to be robust to imperfect CSI. A sub-optimization algorithm based on minimizing sum MSE conditional on available imperfect CSI estimates subject to a per-user power constraint is proposed. The algorithm adapts the existing MMSE algorithm from uncorrelated single-user MIMO system with perfect CSI to correlated MIMO downlink with imperfect CSI. Simulation shows that the suboptimal algorithm can effectively mitigate the performance loss induced by imperfect CSI and has a good convergence performance. In addition, the effect of spatial correlation on the performance of the proposed algorithm is also simulated.     

基于车路信息交互的车辆卫星定位协同定权方法

为确保基于卫星导航系统的车辆定位性能满足特定交通应用需求，本文针对导航卫星观 测量权重分配对复杂动态运行环境的跟踪适配问题，建立基于车路信息交互的车辆卫星定位协 同定位增强总体框架；基于加权最小二乘定位解算模式，设计基于轻量级梯度提升机建模与多车 信息综合决策的协同定权方法，提出面向学习建模通道的导航卫星伪距残差轻量级梯度提升机 建模方案，面向定权计算通道设计了基于多车信息综合决策的导航卫星观测量权重决策策略。 实验结果表明：运用轻量级梯度提升机构建伪距残差模型，相较于支持向量机、随机森林以及仅 基于基础卫星观测特征的轻量级梯度提升机，均方根误差分别降低了62.1%，29.9%，60.4%；运用所建立的预测模型协同定权所得水平误差标准差，相对于等权和卫星仰角/信噪比组合定权策略分别降低了48.5%和47.6%。研究结果对于充分发挥车路协同系统模式下，信息交互机制的核心优势和优化车辆卫星定位性能具有重要意义。     

An range-free localization scheme for large scale underwater wireless sensor networks

In this paper, we study an area localization problem in large scale underwater wireless sensor networks (UWSNs). The limited bandwidth, the severely impaired channel and the cost of underwater equipment all make the underwater localization problem very challenging. Exact localization is very difficult for UWSNs in deep underwater environment. We propose a range free method based on mobile detachable elevator transceiver (DET) and 3D multi-power area localization scheme (3D-MALS) to address the challenging problem. In the proposed scheme, the ideas of 2D multi-power area localization scheme (2D-ALS) and utilizing DET are used to achieve the simplicity, location accuracy, scalability and low cost performances. The DET can rise and get down to broadcast its position. And it is assumed that all the underwater nodes underwater have pressure sensors and know their z coordinates. We evaluate the performances of 2D-ALS and our proposed 3D-MALS schemes under both ideal and non-ideal channel propagation conditions, in terms of localization error and localization ratio. The simulation results show that our proposed scheme is much more efficient than the 2D-ALS.     

具有自适应温度补偿的自动变速器起步控制

根据电控机械式自动变速器起步性能指标及起步过程离合器转矩传递特性，提出了确定离合器目标接合速度的加权方法．该方法兼顾了驾驶员起步意图及自动变速器起步性能要求．模仿人工控制的-特点，同时考虑液压油温度变化的影响，提出了基于误差峰值采样的自适应温度补偿的起步过程离合器接合速控制算法．实验表明，该算法既满足了3种典型起步工况(爬行起步、正常起步和急起步)的性能要求，又提高了系统对温度变化的适应能力．     

基于OFDM的DF中继网络能效最优路径选择策略

针对三节点解码转发(DF)中继OFDM (orthogonal frequency division multiplexing)网络,提出一种能效最优路径选择策略.通过将中继链路衰落值和直传链路衰落值转化为等效路径损耗值,给出了一种基于等效路径损耗指数的能效最优路径选择准则,并分析了电路功率消耗、带宽、速率需求以及信道条件等因素在路径选择时对系统能效的影响.仿真结果表明,能效最优路径与链路速率需求、传输带宽以及信道条件有关,并满足能效最优路径判决准则,当基站(BS)和用户(MS)间距离为610 m,速率等于5和6 Mbit/s时,本文方案的能效比最大调和信道增益路径选择方案分别提高11.8%和40.5%.      

基于交通流时间序列相似性的NCut城市路网分区算法

针对大规模城市道路交通路网分区的实际需求,基于可反映时间序列变化趋势的皮尔逊相关系数和度量空间关系的欧式距离,构建了一种衡量交通流时间序列相似性的综合指标; 结合交通流时间序列的时空相似性特点,引入子区内的空间连通约束,利用归一化割(NCut)算法设计了一种改进的路网静态分区算法; 为体现交通路网分区的时变特征,选取了合适的评价指标来确定每一时间段内合理的分区数量,提出了一种基于时间序列的NCut路网动态分区算法; 利用北京市东北二环区域内采集的路段交通流速度数据,应用所设计的算法对7.23 km2的路网进行分区,对比了晚高峰时期的分区效果。研究结果表明:所提出的分区算法能实现对路网内不同区域交通状况的有效识别,以30 min为间隔的动态分区算法能划分出数量和范围随时间变化的多个可变子区域; 与子区数固定为2、3、4、5的静态分区算法相比,动态分区算法的评价指标分别提升了63.77%、50.06%、6.43%和7.13%,提高了路网分区效果。可见,本文提出的动态分区算法在保证子区内部连通性的基础上可将异质路网划分成多个内部同质子区域,并充分体现交通流动态演化的时空特性,有利于制定动态的多区域边界控制方案。      

Human-imitation recognition algorithm based on multi-character

A multi-character recognition method based on hidden Markov model (HMM) was presented. The method can reduce the calculation load of correlation and improve recognition accuracy compared with single-character recognition in video. The characteristics used for recognizing include the shape character, the color character, the texture character and so on. Even our human being generally uses these characteristics to recognize objects in practice. A recognition experiment of 17 fishes was carried out in the paper. The experimental results demonstrate the high veracity of the multi-character recognition algorithm. Together with the tracking process, it can handle dynamic objects, so the multi-character recognition is more like the human recognition, and has great application value.     

神经Chebyshev正交多项式均衡器及自适应算法

提出一种全新结构的非线性均衡器———神经Chebyshev正交多项式自适应均衡器.该均衡器由1个非线性神经自适应滤波器和1个Chebyshev正交多项式滤波器级联而成.基于最陡下降方法,推导出了相应的自适应算法.仿真结果表明,在线性信道中,该均衡器的均方误差(MSE)比神经自适应均衡器和二阶Volterra均衡器小;在非线性信道中,以更为简单的结构达到了和BP算法训练的三层神经网络相似的性能.     

用于阵列波导光栅设计的傅里叶光学修正算法

以傅里叶光学为基础,应用菲涅耳-惠更斯原理推导出了用于设计阵列波导光栅解复用器的数学模型;分析了菲涅耳近似条件对光场在自由传输区进行高斯远场衍射的影响;提出了一种基于四阶量化误差的修正算法,并和传统的傅里叶光学法及StigmaticPoints法进行了比较分析;设计了一个具有0.4nm通道间隔的1×256信道阵列波导光栅解复用器,结果表明,得到的器件参数与实际设计值相吻合.     

Latent Supportive Utility of Irrelevant Attributes in Feature Selection

This paper proposed a novel feature selection method LUIFS (latent utility of irrelevant feature selection) that not only selects the relevant features, but also targets at discovering the latent useful irrelevant attributes by measuring their supportive importance to other attributes. The method minimizes the information lost and simultaneously maximizes the final classification accuracy. The classification error rates of the LUIFS method on 16 real-life datasets from UCI machine learning repository were evaluated using the ID3, Nave-Bayes, and IB (instance-based classifier) learning algorithms, respectively; and compared with those of the same algorithms with no feature selection (NoFS), feature subset selection (FSS), and correlation-based feature selection (CFS). The empirical results demonstrate that the LUIFS can improve the performance of learning algorithms by taking the latent relevance for irrelevant attributes into consideration, and hence including those potentially important attributes into the optimal feature subset for classification.