MIMO‐UWB smart antenna communication characteristics for different antenna arrays of transmitters

The channel capacity of indoor multiple‐input multiple‐output ultra‐wide band (MIMO‐UWB) transmission for smart antenna is presented. The genetic algorithm (GA) is used to synthesize the radiation pattern of the directional antenna array to maximize the capacity performance in indoor MIMO‐UWB communication system. Three types of antenna arrays such as circular shape, L shape and Y shape arrays are used in the transmitter and their corresponding capacity on several paths in the indoor environment are calculated. The UWB impulse responses of the indoor channel for any transmitter‐receiver location are computed by applying shooting and bouncing ray/image (SBR/image) techniques, inverse fast Fourier transform and Hermitian processing. By using the calculated frequency response, the capacity performance of the synthesized antenna pattern on MIMO‐UWB system can be computed. Based on the topography of the antenna array and the capacity formula, the array pattern synthesis problem can be reformulated into an optimization problem and solved by the GA algorithm. The GA algorithm optimization is applied to a high order nonlinear optimization problem. The novelties of our approach is not only choosing capacity as the cost function instead of sidelobe level of the antenna pattern, but also considering the antenna feed length effect of each array element. The cost function for the problem is nonsmooth and discontinuous with respect to the antenna pattern. It is difficult to solve by gradient methods, since the derivative is hard to derive. The GA algorithm is employed to optimize the excitation voltages and feed lengths for these antenna arrays to increase the capacity. The strong point of the GA is that it can find out the solution even if the performance index cannot be formulated by simple equations. Numerical results show that the synthesized antenna array pattern is effective to focus maximum gain to the LOS path for these antenna arrays. In other words, the receiver can increase the received signal energy to noise ratio. The synthesized array pattern also can mitigate severe multipath fading in complex propagation environment. As a result, the capacity can be increased substantially in indoor MIMO‐UWB communication system. The investigated results can help communication engineers improve their planning and design of indoor wireless communication. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2013.     

基于Chirp-BOK-DQPSK调制的超宽带无线通信系统*

针对普通的Chirp-BOK调制效率不高的问题,设计了基于Chirp-BOK-DQPSK调制的超宽带(UWB)无线通信系统,推导与验证了该系统在AWGN信道下的误比特率,分析了该系统在多径环境下存在较大码间干扰的原因。最后通过仿真分析比较了该系统和Chirp-BOK-UWB系统、Chirp-BOK-DBPSK-UWB系统在IEEE 802.15 SG4a给出的CM1和CM7信道下的性能。仿真结果表明,该系统在牺牲一定误码率性能的情况下,能有效提高传输速率。     

基于多带正交频分复用的超宽带信号压缩传感

针对超宽带(UWB)信号在采样率过高时难以采样的问题,提出了改进的并行分段式压缩传感（MPSCS）方法,并且在多带正交频分复用超宽带通信系统中,利用MPSCS中基于正交匹配追踪（OMP）的重构算法进行了压缩采样与信号重构。在CM1信道下,通过仿真分析比较了MPSCS方法和并行分段式压缩传感（PSCS）方法、奈奎斯特方法的误码率、采样率性能。仿真结果显示,MPSCS在误码率、采样率方面有很大优势,而且在采样率仅为奈奎斯特速率6.06%的情况下,MPSCS能精确重构超宽带信号。     

一种基于卡尔曼滤波的超宽带室内定位算法

为了减小室内环境中障碍物对超宽带(UWB)传感器测距结果的影响,提出了一种基于卡尔曼滤波(KF)的超宽带室内定位算法.利用超宽带接收信号的信噪比区分视距和非视距环境,给出了超宽带传感器测距性能最小二乘标定模型,减小测距系统误差;判断相邻测距差分是否在阈值范围内,否则用卡尔曼滤波先验估计替代后验估计处理测距结果,由此减弱多径效应和非视距误差对测距的影响;用扩展卡尔曼滤波器(EKF)实现室内定位.实验结果表明:算法在复杂室内环境中可达到亚米级的动态实时定位精度.     

一种新型3G系统超宽带室内双向天线研究

设计了一种用于第三代移动通信系统的新型室内双向天线。通过采用渐变球激励的形式,解决了环形天线平衡馈电和阻抗匹配的问题,在节省复杂匹配网络的同时得到了很宽的工作带宽,不需附加额外的匹配网络,天线电压驻波比小于1.5时,阻抗带宽达到100%。天线工作在800 MHz~2 500 MHz,低频段增益可达5 dBi,高频段增益可达8 dBi,满足2G和3G移动室内通信在商务写字楼和宾馆酒店走廊两侧覆盖要求,与现有采用全向天线覆盖的方法相比可有效降低室内移动通信网络的建设成本,提高整个通信网络的容量和质量。     

基于脉冲调制的并行组合扩频通信系统性能研究*

为满足现代通信系统对通信的高效性和安全性的要求,本文提出一种基于脉冲调制的并行组合扩频通信系统,结合超宽带通信脉冲调制和并行组合扩频通信各自在保密性能和高效通信能力方面的优点,使新的系统可以同时具有高效的通信能力和良好的安全保密性能。设计、建立系统模型,并利用仿真软件对系统性能进行仿真和分析。仿真结果表明,基于脉冲调制的并行组合扩频通信系统在误码性能方面优于常规超宽带脉冲调制通信系统和常规正弦载波调制的并行组合扩频通信系统,并且可以通过并行组合扩频部分参数的设置提高系统的信息传输速率,验证了脉冲调制并行组合扩频通信系统良好的误码性能、信息传输能力和系统可行性。     

超宽带系统中一种新型的MMSE-SRAKE接收机

根据超宽带室内信道多径的特点,阐述了一种新型的MMSE-SRAKE接收机,采用基于遗传(GA)算法的路径选择方法。仿真结果表明,通过合理次数的迭代,该接收机性能达到近似最优,优于传统的MMSE-SRAKE接收机。     

Human respiration rate estimation using ultra-wideband distributed cognitive radar system

It has been shown that remote monitoring of pulmonary activity can be achieved using ultra-wideband (UWB) systems,which shows promise in home healthcare, rescue, and security applications. In this paper, we first present a multi-ray propagation model for UWB signal, which is traveling through the human thorax and is reflected on the air/dry-skin/fat/muscle interfaces. A geometry-based statistical channel model is then developed for simulating the reception of UWB signals in the indoor propagation environment. This model enables replication of time-varying multipath profiles due to the displacement of a human chest. Subsequently,a UWB distributed cognitive radar system (UWB-DCRS) is developed for the robust detection of chest cavity motion and the accurate estimation of respiration rate. The analytical framework can serve as a basis in the planning and evaluation of future measurement programs. We also provide a case study on how the antenna beamwidth affects the estimation of respiration rate based on the proposed propagation models and system architecture.     

Optimization of circular antenna arrays using the cuckoo search algorithm

This article presents a study of circular antenna array design and optimization using the cuckoo search (CS) algorithm. The goal of optimization is to minimize the maximum sidelobe level with and without null steering. The CS algorithm is used to determine the parameters of the array elements that produce the desired radiation pattern. We illustrated the effectiveness of the CS in the design and optimization of circular antenna arrays by means of extensive numerical simulations. We compared our results with other methods from the literature whenever possible. We presented numerous examples that show the excellent performance and robustness of the CS algorithm and the results reveal that the design of circular antenna arrays using the CS algorithm provides acceptable enhancement compared with the uniform array or the design obtained using other optimization methods.     

UWB 技术在消防员位置定位系统研究与应用

设计一种基于无载波通信超宽带技术(UWB),对消防员的位置定位进行设计的系统,克服了传统位置定位系统缺点,并一步提高对消防员的位置定位的精确度,而且能够在室内发挥良好作用。超宽带定位技术具有功耗低、高速、抗多径效果好、安全性高,特别是能够在定位方面能够提供非常高的精度等优点,在无线电技术定位方面具有很大发展潜力。     

超宽带Rake接收机结构的研究

超宽带信号在室内密集多径环境下会产生严重的时间弥散,信号的传输性能将会下降,Rake 接收是提高超宽带接收机性能的重要手段。然而如何确定接收机的叉指数目成为接收机设计过程中的关键问题。基于 IEEE802.15.3a 室内超宽带多径信道模型,采用二进制相移键控(BPSK)调制方式时,选用最大比合并(MRC)方式对 Rake 接收机的超宽带通信系统的性能进行了仿真。仿真得出了最佳的合并叉指数目,结果表明在最佳的合并叉指数目情况下的系统性能较其他叉指数目情况下的系统性能更为优越,验讧了选取此叉指数目的有效性。此方法大大有利于 Rake 接收机的设计。     

Joint estimation of time delays and directions of arrival using proper set of antenna elements of a high-order antenna array

In this work, we investigate the accuracy and complexity deviation between using all or selected antenna elements of a massive MIMO array for source localization. In addition, we address the problem of highly resolving the propagation time delay, and the angles of arrival (azimuth and elevation) associated with signals in multipath communication channels for many location-based services and three-dimensional (3D) beamforming. The 3D unitary matrix pencil (3D UMP) algorithm is enhanced and applied in a new way to evaluate these parameters simultaneously from the estimated space channel frequency response (S-CFR) using wideband orthogonal multicarrier signals and uniform rectangular array (URA). Furthermore, the 2D UMP is enhanced to estimate the unknown parameters of wideband signals impinging on 8 different array configurations that are structured as combinations of uniform linear arrays (ULAs). It is not necessary to use all antenna elements of a high-order antenna array for source localization. Due to the dependency on mobile unit location, the phase uncertainties and the deviation of received signal strength between array elements, using the proper set of antenna elements can provide a comparable accuracy and a considerable reduction in the computational complexity of the localization algorithm. The computational complexity is further reduced by exploiting real computation and similar eigen-structure property, and using a priori information of wireless positioning. The IEEE 802.11ac system parameters are used in our experiments.     

一种基于可见光信标的室内定位系统及实现

设计了一种基于LED可见光信标的室内定位系统,具有成本低、功耗低、调制解调算法简单等优点,实验数据表明,使用光学天线可以明显减小误码率并增大可见光通信的传输距离,该室内系统定位最小所需时间为76 ms,当LED信标高度为1 m时,定位精度约为20 cm。     

Reconfigurable method of smart antenna beam shaping in indoor fading environment using adaptive algorithms: An exhaustive experimental study

Adaptive algorithms for beam shaping of a phased array antenna and multiple‐input multiple‐output (MIMO) system gaining importance in today's advanced wireless networks to mitigate interference effects and distortion in the receiving signal due to multipath, small scale, and large scale fading effects. This article deals with the development of reconfigurable field programmable gate array (FPGA)‐based hardware for smart antenna system to explore parameter dependencies, drawbacks, and relative performance comparison of popular adaptive beamforming and interference suppression algorithms. These are least mean square, recursive least squares (RLS), and sample matrix inversion (SMI) used in real‐time under laboratory environment where the existing wireless channel between transmitters and receivers is linear time‐varying in nature due to presence of secondary sources giving rise to small‐scale fading. For this at first, we propose a novel received signal strength indicator‐based procedure to measure the radiation pattern of the antenna under an echoic indoor environment on a reconfigurable and portable FPGA system named wireless open‐access research platform (WARP), controllable by generic programming codes over a user‐friendly MATLAB interface. For better performance, the SMI algorithm was modified to increase block size rather than block shifting in general SMI. Later a comparative study was performed under varying conditions to observe the best utilization of three adaptive algorithms in beam shaping. In all cases, SMI performs the best with less beam shaping error and faster convergence, validating its use in a real‐time fading environment.     

Beamforming of UWB pulse array and its implementation

This paper firstly introduces a realistic ultra-wideband (UWB) pulse model and discusses the principle of sensor array beamforming for UWB pulse signals. Then the differences between a UWB pulse array and narrowband sinusoidal array are studied. Based on it, the problem of realizing a digital and applicable variable delay circuit (VDC) to compensate the channel propagation delay accurately for UWB pulse array beamforming is addressed. In our work, fractional sample delay compensation filters (FDCF) are combined with delay lines to build up accurate VDCs. As a result, the Lagrange interpolation method based on maximally flat criterion is found to be most suitable for the fixed beam steering; and Farrow structure is recommended to satisfy the need of rapid beam adjustment. In the simulation experiments, two kinds of directivity pattern for an UWB pulse array are studied and compared with that of sinusoidal array. The effectiveness of the presented scheme is verified by the simulation results, which show that the VDC implementation by digital lines and FDCF can remarkably improve the performance of the directivity patterns of UWB pulse array especially for the system with low sampling rate.     

Pattern synthesis of the multimode orbital angular momentum beams based on the fruit fly optimization algorithm

The multimode orbital angular momentum (OAM) radio waves can be used to multiplex multiple transmission channels to increase the capacity of communication system without adding additional bandwidth. However, the divergence of the OAM beams and beam inconsistency escalate by increasing OAM mode number. Moreover, the worse sidelobe level (SLL) always appears along with a better convergent beam. In this article, the fruit fly optimization algorithm (FOA) is proposed to suppress the SLL in multimode OAM scenario. Based on the concentric circular array antenna (CCAA), the feeding amplitudes and the radii of the array are synthesized simultaneously to realize less than ?30 dB SLL of the multimode OAM patterns. When the main lobes with different OAM modes steered to a uniform azimuth of θ = 0° , the SLLs of these OAM modes are also suppressed to less than ?21 dB. The advantages of FOA used in the OAM pattern synthesis are verified by comparing it with the genetic algorithm (GA). The FOA‐based synthesis has a simpler implementation flow diagram which reduces the time of synthesis to 39.5% of GA.     

Towards robust and efficient device-free localization using UWB sensor network

Device-free localization (DFL) is the method of using distributed wireless sensors to localize the target without carrying any devices. Existing DFL methods leverage the variation of narrowband received signal strength (NRSS) which is vulnerable to multipath fading, and thus results in considerable performance degradation in indoor environments. Moreover, the inefficient sensor deployment of traditional DFL involves huge human efforts, which is not suitable for emergency scenarios. In this paper, we utilize sensors transmitting ultra-wideband (UWB) signals to solve both problems. We proposed two RSS variation estimation methods based on the channel impulse response (CIR) measurements provided by UWB sensors, which turn out to be more robust to multipath than NRSS due to the fine multipath resolution of UWB signals. We also employ a higher operating frequency to enhance the shadowing loss for mitigating the multipath effect. Additionally, satisfactory sensor self-localization is achieved under the cooperative localization framework owing to the accurate ranging capability of UWB sensors. We conducted experiments in three different environments to explore the feasibility of our method. The results show that the proposed method gains much better localization performance and requires less human efforts than narrowband DFL.     

100Mbps UWB通信系统基带单元的设计与实现

超宽带通信技术与其它通信技术有很大不同,它具有信号功率谱密度低、保密性强、穿透能力强、抗多径干扰等优点,尤其适合于室内等密集多径场所的高速无线接入和军事通信。本文介绍了一种基于TH-PPM的100Mbps超宽带试验通信系统的实现方案,对系统基带信号处理的同步捕获、卷积、交织模块进行了详细的介绍,并在搭建的室内UWB实验平台台上得到了验证。     

融合UWB与INS的消防员室内定位与NLOS检测算法

融合超宽带（UWB）和惯性导航系统（INS）能够实现消防员室内精确定位。为实现UWB的非视距（NLOS）误差检测,设计一种双级EKF框架。该框架以松耦合形式实现UWB/INS的数据融合,通过INS获取的初始位置估计坐标以检测UWB测量值的NLOS误差,根据检测结果计算残差矩阵来动态调整融合滤波器的测量噪声矩阵,以达到缓解NLOS误差的目的。实验结果表明,与三角不等式原理检测算法和无NLOS检测的UWB/INS简单融合算法相比,所提NLOS检测算法具备良好的检测能力、较强的稳定性及较高的定位精度。     

基于遗传算法的多板天线时延相位补偿技术

关于动中通系统中普遍采用抛物面天线,可使得系统小型化难度增加,为优化最佳天线方案,采用平板天线取代抛物面天线可以部分改善.为促进动中通技术在车载平台中的应用,提出了超低轮廓相控阵天线方案,使得平板相控阵天线的高度进一步降低.针对孔径效应和孔径渡越时间限制问题,给出了时延相位两级补偿的方法,有效扩展了天线系统的工作带宽;同时采用遗传算法调整天线阵因子相位,对多板相控阵天线方向图的副瓣高度实现了优化.仿真结果表明,多板天线方案可以实现性能对平板天线的逼近,并很好的适应了车载平台对天线高度的严格要求,有较高的工程实用价值.