Tracking via Square Grid of RFID Reader Positioning and Diffusion Algorithm

The study and analysis of RFID (radio frequency identification) reader positioning is important for RFID large-scale deployment. Therefore, the purpose of this research is to investigate the art of RFID reader positioning in order to develop a highly accurate positioning and tracking system for usage inside a building and also to optimize the tracking performance that can be applied to different active and passive RFID standards. This study involves design of square grid RFID reader network and position calculation using diffusion algorithm. Square grid network presents the solution of placement pattern of RFID readers, hence optimal number of required readers and guaranteed coverage can be achieved. The proposed diffusion algorithm makes use of distance information between the reader and the tag to estimate the RFID tag position. This study has also introduced a probabilistic mathematical model to maintain coverage of the unit square region and to ensure connectivity of the proposed square grid network. The effectiveness of the diffusion algorithm is evaluated in this study and the obtained results show satisfactory performance. The obtained results show that the proposed positioning system can achieve average positioning error below 1 m with different RFID reading ranges and in some cases accuracy improvement of about 65% can be reached than the results obtained by known positioning system. It is also found that the proposed diffusion algorithm together with square grid can bring approximately 50–85% improvement on raw accuracy provided by only square grid method.     

Performance analysis of cross-layer design with average PER constraint over MIMO fading channels

In this article, a cross-layer design (CLD) scheme for multiple-input and multiple-output system with the dual constraints of imperfect feedback and average packet error rate (PER) is presented, which is based on the combination of the adaptive modulation and the automatic repeat request protocols. The design performance is also evaluated over wireless Rayleigh fading channel. With the constraint of target PER and average PER, the optimum switching thresholds (STs) for attaining maximum spectral efficiency (SE) are developed. An effective iterative algorithm for finding the optimal STs is proposed via Lagrange multiplier optimisation. With different thresholds available, the analytical expressions of the average SE and PER are provided for the performance evaluation. To avoid the performance loss caused by the conventional single estimate, multiple outdated estimates (MOE) method, which utilises multiple previous channel estimation information, is presented for CLD to improve the system performance. It is shown that numerical simulations for average PER and SE are in consistent with the theoretical analysis and that the developed CLD with average PER constraint can meet the target PER requirement and show better performance in comparison with the conventional CLD with instantaneous PER constraint. Especially, the CLD based on the MOE method can obviously increase the system SE and reduce the impact of feedback delay greatly.     

Interference Mitigation in Asynchronous Slow Frequency Hopping Bluetooth Networks

In asynchronous slow frequency hopping Bluetooth networks, packet collisions diminish the total link throughput. However, interference mitigation capability can reduce packet losses due to collisions. In this paper, an interference cancelling dual decision feedback (IC-DDF) Bluetooth receiver is proposed and its performance is evaluated for slow fading indoor channels. In addition to the bit error rate (BER) performance, the system level performance is evaluated by using the packet error rate (PER). To integrate the BER performance into the PER performance, a new geometric interpretation of packet error rate is introduced that uses an ensemble average of the received carrier to interference ratio (CIR). Also, a generalized packet collision probability is derived to analyze total link throughput.     

基于间隔估计法的RFID防碰撞算法

多个应答器的碰撞问题是影响超高频射频识别(RFID)系统读取效率的一个关键问题。从EPC Class1 Generation2(C1G2)RFID系统帧长受约束特点出发,分析了帧时隙ALOHA防碰撞机制及其经典应答器估计方法的特点。提出了应答器间隔估计方法(IEM)以及基于该方法的EPC C1G2 RFID防碰撞算法,并给出了仿真结果。与现有基于经典应答器估计方法的射频识别系统防碰撞算法相比较,提出的防碰撞算法减少了识别时间,提高了系统的识别效率。     

Performance of heterogeneous multiuser MIMO system with cross-layer design and multiple outdated estimations in Rayleigh fading channel

By combining adaptive modulation and automatic repeat request protocol as well as user scheduling, a cross-layer design (CLD) scheme for multiuser MIMO system with the normalized signal-to-noise ratio (SNR)-based scheduling under heterogeneous case is developed, where perfect and imperfect channel state information (CSI) are both considered. Based on this, by exploiting previous channel estimation information, the multiple outdated estimates method is presented to improve the system performance under imperfect CSI. According to the performance analysis and the normalized-SNR based scheduling scheme, the average spectral efficiency (SE) and packet error rate (PER) of the system are derived, respectively. As a result, closed-form SE and PER expressions are attained. These expressions include the ones with conventional single outdated estimate as special cases, and can provide good performance evaluation for the multiuser CLD system under heterogeneous case. Simulation results show that the derived theoretical SE and PER are in consistent with the corresponding simulations. Moreover, the presented CLD scheme with multiple estimates can provide higher SE and lower PER than that with conventional single estimate in the presence of imperfect CSI. Besides, multiuser MIMO-CLD has superior performance over the conventional single user counterpart due to the multiuser diversity.     

基于多天线到达相位差的室内定位算法

针对测距式射频识别(RFID)室内定位算法的精确度会受到测距误差严重影响的问题,提出一种基于多天线到达相位差(M-PDOA)的室内定位算法。通过M-PDOA测距方法进行测距,采用三边测量算法对目标标签进行定位。仿真结果显示,本算法的测距平均误差为0.102 7 m,性能提升65.76%;定位平均误差为0.180 7 m,性能提升56.67%,说明本文算法能够有效减少测距误差,并且定位精确度较高。     

基于历史信息的软卡尔曼滤波迭代时变信道估计方法

针对高速移动MIMO-OFDM系统,提出了一种基于历史信息的软卡尔曼滤波迭代时变信道估计方法。考虑高速铁路环境中不同列车在相同位置处的信道具有很强的相关性,首先利用历史列车的信道信息获取最优基函数,基于该基函数对信道建模,将对信道的估计转换成基系数的估计,降低了计算复杂度和提高了信道估计精度。其次,在每次迭代中采用了软卡尔曼滤波和数据检测联合的方法估计基系数;为了更好地减少数据检测误差传播的影响,采用软数据检测方法,并且在每次迭代中将软数据检测误差作为噪声进行处理。另外,采用的软卡尔曼滤波器不涉及 AR 模型跟踪因子,避免了估计跟踪因子引入的计算复杂度。仿真结果表明,所提方法具有更好的估计性能,且更适用于实际的高速移动场景的时变信道获取。     

基于信道转换的蓝牙微微网之间同频干扰抑制方法

多个蓝牙微微网之间的同频干扰十分严重,该文针对此问题提出一种基于信道转换的同频干扰抑制方法。该方法在蓝牙微微网重传时进行信道转换,以同频不一定会产生干扰为前提,综合考虑了返回分组、跳频保护间隔、3种时隙分组共存等多种情况,使分析更加接近真实情况。对网络性能指标进行大量仿真,由仿真分析可见,该方法有效地降低了蓝牙微微网的分组错误率,提高了微微网的吞吐量,尤其当网络数量在14~57范围内时,微微网吞吐量最大可增加260 kbps。     

Parameter estimator based on a minimum discrepancy criterion: aBayesian approach

A new estimation criterion based on the discrepancy between the estimator's error covariance and its information lower bound is proposed. This discrepancy measure criterion tries to take the information content of the observed data into account. A minimum discrepancy estimator (MDE) is then obtained under a linearity assumption. This estimator is shown to be equivalent to the maximum likelihood estimator (MLE), if one assumes that a linear efficient estimator exists and the prior distribution of parameters is uniform. Moreover, it is equivalent to the minimum variance unbiased estimator (MVUE) if the MDE is required to be unbiased. Illustrative examples of MDE and its comparisons with other estimators are given     

一种基于单次散射体定位的TOA/AOA混合定位算法

为了降低非视距(Non-Line-of-Sight,NLOS)误差对定位精度的不利影响,提出了一种基于散射体定位的到达时间(Time of Arrival,TOA)/到达角(Angle of Arrival,AOA)混合定位算法.假设各基站(Base Station,BS)接收的多径信号都经历了散射体单次散射,首先利用...     

New Adaptive All-pass Based Notch Filter for Narrowband/FM Anti-jamming GPS Receivers

The global positioning system (GPS), which provides accurate positioning and timing information, has become a commonly used navigation instrument for many applications. The application of a new adaptive all-pass based notch filter (ANFA) for narrowband/FM interference suppression and frequency estimation in GPS receivers is proposed. An ANFA structure that achieves better unbiased characteristics with its coefficients is employed to accurately estimate the narrowband interfering signals in online fashion. A variable convergence factor that optimizes the maximal mean square error (MSE) reduction in each iteration is applied in a modified adaptive Gaussian–Newton (MAGN) algorithm. The proposed MAGN algorithm can lead to both faster convergence speed and higher estimation accuracy. Simulation results show that the ANFA offers a better performance than conventional linear predictors in terms of the SNR improvement and the mean output power (MOP) under the interference environments of interest.     

On Loss Differentiation for CSMA-Based Dense Wireless Network

In this paper, we propose a novel method to differentiate packet loss based on interference energy and timing relative to desired signal in CSMA-based dense wireless networks. All measurements are conducted locally at transmitters without any additional over-the-air overhead. Our method can estimate PER (packet error rate) due to interference prior to or after the beginning of the desired signal separately, allowing for more efficient MAC(media access control) adaptation design.     

基于软判决的MMSE-OSIC接收机

串行干扰相消接收机是广泛应用于多输入多输出系统中的一种接收端信号处理与检测技术。在串行干扰相消接收机中,先检测的层的判决准确性会对后续层的检测产生影响。检测过程中产生的判决误差,将对后续层的检测引入残留干扰,进而影响后续层检测的正确性,造成差错传播。本文提出一种基于软判决的最小均方误差检测带排序串行干扰相消接收机,可以有效减轻基于硬判决方法的带排序串行干扰相消接收机的差错传播问题。在重构干扰信号时,该接收机使用根据软判决信息得到的符号期望,替代硬判决方法,能够有效降低干扰相消时各层之间由判决误差引起的残留干扰;该接收机还可以精确估计残留干扰的功率以及各层数据流的后处理信干噪比,改善了基于硬判决方法的串行干扰相消接收机存在的各层后处理信干噪比估计值偏大的问题。可靠性更高的软判决结果有效降低了残留干扰,更精确的各层后处理信干噪比抑制了残留干扰对后续数据流检测的影响,提高了判决结果和排序过程的准确性。仿真结果证明,基于软判决的最小均方误差检测带排序串行干扰相消接收机可以有效避免差错传播的产生,因而获得较大的性能提升。      

Objects tracking in a dense reader environment utilising grids of RFID antenna positioning

One of the fundamental constraints in radio frequency identification (RFID) large scale deployment, such as in warehouse RFID deployment, is the positioning of RFID reader antennas to efficiently locate all the tagged objects distributed in a dense RFID reader environment. For tracking the tagged objects in a dense RFID deployment, the required number of reader antennas must be optimised in order to reduce the overall cost. This study proposes highly accurate square and hexagonal grid-based positioning and tracking techniques mainly for use indoors and includes performance comparison of both of these grids. The study involves the design of the square and hexagonal grid reader antenna networks and position calculation using a diffusion algorithm. Both of these grids of RFID antenna positioning present a solution for the problem of the placement pattern of RFID reader antennas in a dense reader environment, hence an optimal number of required reader antennas and guaranteed coverage can be achieved. This study also presents a path loss model that can be applied to predict the radio signal strength information at a certain distance. The proposed diffusion algorithm estimates RFID tag position by using distance information between the reader and the tag. The obtained results show that a square grid can yield higher positioning accuracy compared to the hexagonal grid. The obtained results further show that the proposed tracking techniques can achieve an average positioning error below 1 m, which is 85% better in some cases than the results obtained by other known methods.     

基于FM0记忆辅助特性的RFID标签碰撞检测

为实现两个射频识别(RFID)碰撞标签信息的检测和分离，提出一种利用Gen2标准中FM0标签编码固有记忆特性的检测方法。通过对FM0比特编码特点和碰撞标签信息的无记忆检测分析，得到基于单个比特持续时间的无记忆检测方法的条件错误概率和单个标签信息检测的误码率；然后利用单个FM0比特编码需要前一比特的“记忆”特性，得到对应于前一比特的一对测量值和对应于下一比特的一对测量值，进而得到碰撞标签信息的1比特记忆辅助检测时的条件错误概率和误码率性能；并对在帧Aloha媒质接入方案中采用提出的检测方法时的N个标签群的总延迟减少性能进行了分析。仿真实验结果表明，提出的1比特记忆辅助检测方法，相比于无记忆检测具有更好的误码率性能，且能减少标签群接入时的总延迟。     

Combined MMSE interference suppression and turbo coding for acoherent DS-CDMA system

The performance of a turbo-coded code division multiaccess system with a minimum mean-square error (MMSE) receiver for interference suppression is analyzed on a Rayleigh fading channel. In order to accurately estimate the performance of the turbo coding, two improvements are proposed on the conventional union bounds: the information of the minimum distance of a particular turbo interleaver is used to modify the average weight spectra, and the tangential bound is extended to the Rayleigh fading channel. Theoretical results are derived based on the optimum tap weights of the MMSE receiver and maximum-likelihood decoding. Simulation results incorporating iterative decoding, RLS adaptation, and the effects of finite interleaving are also presented. The results show that in the majority of the scenarios that we are concerned with, the MMSE receiver with a rate-1/2 turbo code will outperform a rate-1/4 turbo code. They also show that, for a bit error rate lower than 10^-3, the capacity of the system is increased by using turbo codes over convolutional codes, even with small block sizes     

一种稳健的盲稀疏度压缩感知雷达目标参数估计方法

针对压缩感知雷达(Compressive Sensing Radar, CSR)在感知矩阵和目标信息矢量失配时距离-多普勒参数估计性能下降的问题,该文提出一种稳健的盲稀疏度CSR目标参数估计方法。首先建立了CSR系统模型失配时的距离-多普勒2维参数稀疏感知模型,推导了以最小化感知矩阵相干系数(Coherence of Sensing Matrix, CSM)为准则的波形优化目标函数。其次提出了一种新的盲稀疏度CSR目标参数估计方法,通过发射波形,系统模型失配误差和目标信息矢量的相互迭代,逐步校正系统感知矩阵,最终以较高精度估计目标距离-多普勒参数。与传统CSR目标参数估计方法相比,该方法显著降低了CSR系统距离-多普勒参数的估计误差,改善了CSR目标参数估计的准确性和鲁棒性。计算机仿真验证了该方法的有效性。     

一种基于RSSI指纹和DOA信息的单基站定位方法

无人集群系统技术是未来无人机技术的发展趋势。在复杂未知的背景环境中，由于电磁、物理屏障等不可控干扰因素，导航系统易出现因卫星信号拒止而无法准确提供导航信息的情况。本文利用无人集群系统多机编队的特点，提出一种基于目标间信号到达方位(DOA)和接收信号强度(RSSI)指纹信息(Fingerprints)的协作定位方法，仅利用单个基站即可实现对移动目标节点的位置定位。实验结果表明，对突然丧失定位能力的节点，本文方法能够实现盲节点的再定位功能，在约 80m×80m 的运动区域内达到约 1.5m 的定位精度。该方法定位误差不随时间积累，具有良好的定位性能。     

一种融合时差频差和测向的运动目标跟踪方法

传统的星载无源定位系统对空中辐射源定位求解通常采用假设高程的方法,高程假设误差将对定位跟踪精度造成较大影响。为实现未知高程运动辐射源的高精度定位跟踪,针对异轨三星构型的无源定位系统,提出了一种基于时差、频差和二维测向融合的迭代扩展卡尔曼滤波(Iterative Extended Kalman Filter, IEKF)跟踪方法。在WGS-84坐标系下建立了状态方程和观测方程,并采用IEKF方法对目标状态进行估计。仿真结果表明,该方法可对未知高程的运动目标进行高精度状态估计,典型仿真场景下的目标高程估计精度达到百米量级,相对于已有方法收敛时间更短,并且在卫星覆盖范围内具有更大的高精度定位跟踪区域。     

融合梯度和色度信息的分块均值漂移目标跟踪

针对在相似颜色干扰场景下传统均值漂移目标跟踪鲁棒性差的缺陷,提出Prewitt梯度和色度信息融合的分块均值漂移跟踪算法。首先,对跟踪框进行分块,并提取当前帧各子块特征;其次,利用Bhattacharyya距离计算参考目标区域与候选区域间各子块对应的相似程度,根据其相似程度分配各子块的权值,并通过融合规则对各子块相应特征进行融合构成新子块特征,在此基础上,将子块特征选择串接方式作为最终目标特征;最后,采用均值偏移原理迭代估计最终目标位置信息。实验结果表明,当场景中存在相似颜色干扰的情况下,相对于经典均值漂移算法,其准确度提高了84%左右。