Outage probability of multiple-IRS-assisted SISO wireless communications over Rician fading

Outage probability (OP) performance of multiple-intelligent reflecting surface (IRS)-assisted is presented for a practically important single-input-single-output (SISO) wireless communication system over Rician fading channels where the IRS panel selection is considered. We investigate the SISO wireless communication scenario in which a single antenna transmitting node is sending its message to the receiving node with the aid of the best IRS panel selection. This wireless communication scenario model is a typical application of the uplink scenarios for future cellular wireless systems. We derive approximate OP expressions in the closed form using both the central limit theorem and the Laguerre series expansion. Further, we also derive a simple asymptotic OP to get diversity order and coding gain. The influence of each system parameter on OP performance is thoroughly investigated. In addition, the analytical OP results are corroborated with simulated OP results to confirm the accuracy of our presented analytical results.     

Lower bound on the capacity of distributed MIMO systems with spatially correlated Rician/Lognormal fading

This paper presents an analytic lower bound of ergodic capacity for distributed MIMO (D-MIMO) systems that experience not only Rician fading but also shadowing effects of Lognormal distributed. In particularly, we consider that the Rician fading channel is spatially correlated at both transmitter and receiver. In the communication environment corresponding to this setting, the angle spread at the transmitter and the angle spread at the receiver are both insufficient, and the non-fading components co-exists with the fading components. Such communication environment is very common. In the process of deriving the analytic lower bound, in order to avoid Hayakawa polynomials that cannot be analytically expressed, non-central quadratic forms are transformed to non-central Wishart matrices by use of inequality. The validity of the presented lower bound is verified by computer simulations. The simulation results show the influence of the number of radio ports at the transmitter, the number of antennas at the transmitter or receiver, correlation level (angle spreads) and Rician K-factor on the capacity of systems. In all cases, the presented bound remains tight across the entire signal-to-noise ratio (SNR) regime.     

Moment-based modulation classification for Rician time-varying aeronautical channels

Modulation classification is a classical topic in the field of signal classification, and is of great significance in various applications including aeronautical communications. However, changes in the features of the signals transmitted through the Rician time-varying channels deteriorate the performance of modulation classification. In this study, a robust moment-based algorithm is proposed to counter the influence of the channels. The statistical correlation of the received samples are utilized for the estimation on the Rician factor. According to the derivation of the relationship between the moments of the transmitted samples and the received samples, the features utilized for classification are compensated mathematically. Finally, decision tree and random forest classifier are presented for classification. The estimation and classification performance of the proposed algorithm are analyzed for aeronautical en-route (EN) and arrival/takeoff (AT) channels through simulations. Meanwhile, real world signals of L-band digital aeronautical communication system (L-DACS1) are utilized for verification. The results show that our algorithm has high classification accuracy and low computational complexity.     

On signal space diversity: An adaptive interleaver for enhancing physical layer security in frequency selective fading channels

Signal space diversity is a powerful technique that increases reliability of detection over fading channels. In this paper, we explore the ability of this technique to provide secure communication. We enhance the security of OFDM systems in frequency selective fading channels by providing more diversity gain to the legitimate user compared to an eavesdropper. This is done by adapting the interleaving pattern to the channel of the legitimate user in rich multipath environments, where spatially separated channels are typically independent to each other. This ensures secrecy in a time division duplex system, where the eavesdropper has no information regarding the channel of the legitimate user. The scheme can also be used in the conventional frequency division duplex system, which is more challenging in terms of security aspects because of the channel state information leakage. A theoretical analysis is presented on the bit-error probability in Rayleigh fading environment. The numerical results support the conclusion that adapting the interleaving pattern to the CSI of the legitimate user provides a gain in the bit-error rate performance over the eavesdropper.     

Modeling the lossy transmission of correlated sources in multiple access fading channels

In this paper, we develop accurate distortion models for the lossy transmission of two correlated sources in a multiple access Rayleigh fading channel. We focus on a class of real-life communication systems, where the source and channel coders have already been designed separately and can only be configured during the system operation. We investigate three different source coding schemes: distributed source coding (DSC), layered source coding, and independent compression through quantization. With the later scheme the sources are jointly decoded with minimum mean square error (MMSE) estimation at the receiver. We also consider two different transmission schemes: Orthogonal transmissions and interfering transmissions decoded with a successive interference cancellation (SIC) decoder. Our final closed-form analytical models are used to determine the optimal combination of source coding and transmission schemes, as well as their optimal configuration. Hence, we exercise joint source and channel coding (JSCC) by optimizing the system configuration. Through simulations, we first validate the analytical model and illustrate the performance of different schemes. Finally, we demonstrate the JSCC gains achieved by our system.     

一种新的快速衰落信道相干时间估计方法

快速衰落信道(FFD)是浅海中常见的畸变信道模型之一,通常用信道相干时间来描述其多普勒扩展程度。分段副本相关器(SRC)是FFD信道的最佳似然比检测器,但当信道相干时间未知时,其性能因失配受到较大影响。针对此种情况,提出了多重假设SRC,该方法能简单有效地估计FFD信道相干时间并解决SRC的失配问题。     

A new layered space--time detection algorithm for frequency selective fading multiple-input multiple-output channels based on particle filter

In this paper, a new observation equation of non-Gaussian frequency selective fading Bell Labs layered space time (BLAST) architecture system is proposed, which is used for frequency selective fading channels and non-Gaussian noise in an application environment of BLAST system. With othogonal matrix triangularization (QR decomposition) of the channel matrix, the static observation equation of frequency selective fading BLAST system is transformed into a dynamic state space model, and then the particle filter is used for space--time layered detection. Making the full use of the finite alphabet of the digital modulation communication signal, the optimal proposal distribution can be chosen to produce particle and update the weight. Incorporated with current method of reducing error propagation, a new space--time layered detection algorithm is proposed. Simulation result shows the validity of the proposed algorithm.     

Upper bounds on the private capacity for bosonic Gaussian channels

Recently, there have been considerable progresses on the bounds of various quantum channel capacities for bosonic Gaussian channels. Especially, several upper bounds for the classical capacity and the quantum capacity on the bosonic Gaussian channels, via a technique known as quantum entropy power inequality, have been shed light on understanding the mysterious quantum-channel-capacity problems. However, upper bounds for the private capacity on quantum channels are still missing for the study on certain universal upper bounds. Here, we derive upper bounds on the private capacity for bosonic Gaussian channels involving a general Gaussian-noise case through the conditional quantum entropy power inequality.     

The volume measure for flat connections as limit of the Yang–Mills measure

We prove that integration over the moduli space of flat connections can be obtained as a limit of integration with respect to the Yang–Mills measure defined in terms of the heat-kernel for the gauge group. In doing this we also give a rigorous proof of Witten’s formula for the symplectic volume of the moduli space of flat connections. Our proof uses an elementary identity connecting determinants of matrices along with a careful accounting of certain dense subsets of full measure in the moduli space.     

Effect of multivalent cation substitution on the capacity fading of lithium manganese spinel cathodes

The introduction of Co, Al, and Ti into LiMn₂O₄ cathode powders has been studied in this work. The substitution of 25% Mn with either of these metals is expected to improve the cycle ability of the cathode, while the Jahn–Teller effect is suppressed. The solid-state reaction method is used in order to produce the cathode materials, which are prepared at 750 or 800 °C. The materials are characterized by X-ray data and, electrochemically, by galvanostatic cycling at the 4-V range. Their capacity fading behavior is evaluated, and a further investigation into cycling at a higher voltage range is also presented.     

Simple, accurate formula for the average bit error probability of multiple-input multiple-output free-space optical links over negative exponential turbulence channels

In this Letter we investigate the error performance of multiple-input multiple-output free-space optical communication systems employing intensity modulation/direct detection and operating over strong atmospheric turbulence channels. Atmospheric-induced strong turbulence fading is modeled using the negative exponential distribution. For the considered system, an approximate yet accurate analytical expression for the average bit error probability is derived and an efficient method for its numerical evaluation is proposed. Numerically evaluated and computer simulation results are further provided to demonstrate the validity of the proposed mathematical analysis.     

Modeling of the EHD effects on hydrodynamics and heat transfer within a flat miniature heat pipe including axial capillary grooves

A numerical model for an electrohydrodynamic (EHD) grooved Flat Miniature Heat Pipe (FMHP) is developed. Two microchannel shapes are considered as axial capillary structures: square and triangle grooves. For both groove shapes, the electric field affects the liquid-vapor radius of curvature which decreases in the condenser and increases in the evaporator under the action of the electric field. The liquid and vapor velocities are also affected by the EHD effects. The electric field effects on the velocities depend on the FMHP zone. It is also demonstrated that the electric field increases the vapor pressure drop; however, it decreases the liquid pressure drop. The liquid-wall and vapor-wall viscous forces as well as the shear liquid-vapor forces are affected by the electric field. The analysis of the electric forces shows that the dielectrophoretic forces which act on the liquid-vapor interface are predominant and their order of magnitude is much higher than the Coulomb forces. Finally, it is also demonstrated that the capillary limit increases with the electric field for both groove shapes.     

An error detection and recovery algorithm for the transmission of digital holography over noisy channels

Digitalization enables and expertise storage and transmission of holographic data. However, the reconstructed object image is vulnerable to transmission errors over the noisy channel. We present a novel algorithm of what we believe is the first approach to reduction of noise effects on digital holograms corrupted by transmission errors. To accomplish this work, we exploit new interdependencies on the interference holograms and develop a detection-based algorithm to detect error points and to identify the corresponding interference holograms with the largest errors. In the reconstruction process, the conventional four-step algorithm is used for the recovery of error-free points. In contrast, a three-step algorithm is employed to reconstruct error points by removing the largest error holograms. With accurate detection, the proposed algorithm is capable of recovering the object image from digital holograms with severe transmission errors. It is shown that the proposed algorithm provides much better reconstruction performances than the conventional four-step reconstruction algorithm in an error-prone environment.     

电动汽车空调热泵微通道换热器扁管布置方式对制热性能的影响

本文针对电动汽车空调热泵系统的室内微通道换热器制热性能进行了研究.首先对换热器的流程排布进行了优化分析,得到四流程12-13-13-12模型性能最优.在优化分析的基础上,实验研究了室内换热器扁管横竖布置方式对单体及系统制热性能的影响.结果发现在单体实验中,扁管竖置布置时的内部制冷剂分布均匀度远好于扁管横置布置,其换热量与出风温度比扁管横置布置分别提高了11.2%~16.5%与6.3%~8.4%.系统制热实验结果表明,扁管横置布置的制冷剂分布均匀度仍小于扁管竖置布置,且其受压缩机转速影响较大.而当扁管竖置布置时,制冷剂分布均匀度随着压缩机转速增大而减小.而随着室外环境温度的降低,扁管竖置布置的优势减弱。     

A method for the construction of hierarchical generalized space shift keying (GSSK) modulation for unequal error protection

In this paper, we propose a systematic method to achieve two-level unequal error protection (UEP) with generalized space shift keying (GSSK) modulation for multiple-input multiple-output (MIMO) systems. GSSK is a modulation scheme that encodes the source information in the antenna indices. To enable the nonuniform arrangement of the spatial constellation of GSSK modulation, new techniques are needed as new features of GSSK modulation are observed. The proposed method is based on first partitioning the GSSK constellation into subsets and then choosing constellation points inside a subset. The high-priority (HP) bits select the subset and the low-priority (LP) bits select constellation points inside a subset. The proposed subset partitioning procedure developed based on a theoretical study on set partitioning in the multidimensional space guarantees optimal or near-optimal HP protection, enables simple and systematic designs for LP protection, and increases the LP capacity. The proposed systematic design approach applies to systems with any numbers of transmit antennas and can create various hierarchical GSSK schemes with different HP/LP protection capabilities.     

纳米分辨率外差干涉信号处理电路相位畸变的实验研究

外差干涉是实现纳米精度长度测量的重要手段。采用电子倍频、混频、高频计数的方法可处理外差信号实现亚纳米分辨率,具有电路简单、能计大数的优点,但会引入电子信号的相位畸变,引入测量的动态误差。本文通过理论和实验分析了这一误差,表明在电子倍频中锁相环引起的相位畸变仅在亚纳米量级,但在混频环节中带通滤波器引入的相位畸变则可达几纳米,引入较严重的误差。本文通过采用低频差横向塞曼激光器产生３２０ｋＨｚ的外差信号,并采用ＦＰＧＡ技术实现倍频后的高频率信号直接计数,省略混频环节,从而实现了高测量分辨率并避免了这一误差。     

混沌系统模型误差平均绝对误差增长过程研究

混沌系统的平均绝对误差增长最初是用来刻画初始值误差增长的,本文依照平均绝对误差增长的定义来研究模型误差的增长过程,获得了一些很有意义的结论．研究发现,在初期模型误差的平均绝对误差增长呈指数级增长,增长指数同模型的扰动相关,与真实系统最大Lyapunov指数没有直接关系．其后模型误差进入非线性增长过程,误差增长放缓,最终达到饱和．误差饱和值恒定,当真实系统和模型系统吸引子差别较小时,模型误差饱和值基本上同真实系统的初始值误差饱和值相等．利用上述研究结论可以求出模型的可预报期限,这在数值天气预报中具有重要的意义．进而利用模型的可预报期限可以对同一真实系统的不同模型进行评价,相对真实系统越精确的模型拥有更高的可预报期限．这对新模型的开发具有很强的指导作用．     

Method for estimating the influence of an external electric field on the probability of photochemical transformations

We propose an approach to estimating the influence of a strong external electric field on the probability of photochemical transformations. The approach is based on an analysis of the appearance or disappearance of the resonance levels of interacting subsystems that are necessary for the chemical transformation and the change of overlap integral of the corresponding wave functions. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 4, pp. 543–545, July–August, 2007.