Capacity of MI MO LAS-CDMA System Under Correlating Multi-Path Fading Channels

Capacity of MIMO LAS-CDMA systems under multi-path fading channels with two different correlating models were studied in the paper. Influences of the two models parameters on capacity were analyzed. The numerical results present that ： according to the Various Scattering Environments correlating model, when the inner-elements distance of antennas array is large than 0. 5λ, correlation almost does not take from the system capacity ; for the Salz-Winter correlating model, the spread angle at receiver is the other key factor, it also influence the system capacity greatly.

A Deep Learning Based Broadcast Approach for Image Semantic Communication over Fading Channels

We consider an image semantic communication system in a time-varying fading Gaussian MIMO channel,with a finite number of channel states.A deep learning-aided broadcast approach scheme is proposed to benefit the adaptive semantic transmission in terms of different channel states.We combine the classic broadcast approach with the image transformer to implement this adaptive joint source and channel coding(JSCC)scheme.Specifically,we utilize the neural network(NN)to jointly optimize the hierarchical image compression and superposition code mapping within this scheme.The learned transformers and codebooks allow recovering of the image with an adaptive quality and low error rate at the receiver side,in each channel state.The simulation results exhibit our proposed scheme can dynamically adapt the coding to the current channel state and outperform some existing intelligent schemes with the fixed coding block.

Effective Capacity of URLLC over Parallel Fading Channels with Imperfect Channel State Information

This paper investigates the effective capacity of a point-to-point ultra-reliable low latency communication(URLLC)transmission over multiple parallel sub-channels at finite blocklength(FBL)with imperfect channel state information(CSI).Based on reasonable assumptions and approximations,we derive the effective capacity as a function of the pilot length,decoding error probability,transmit power and the sub-channel number.Then we reveal significant impact of the above parameters on the effective capacity.A closed-form lower bound of the effective capacity is derived and an alternating optimization based algorithm is proposed to find the optimal pilot length and decoding error probability.Simulation results validate our theoretical analysis and show that the closedform lower bound is very tight.In addition,through the simulations of the optimized effective capacity,insights for pilot length and decoding error probability optimization are provided to evaluate the optimal parameters in realistic systems.

Energy efficiency aware dynamic rate and power adaptation in carrier sensing based WLANs under Rayleigh fading and shadowing

We consider the problem of energy efficiency aware dynamic adaptation of data transmission rate and transmission power of the users in carrier sensing based Wireless Local Area Networks(WLANs)in the presence of path loss,Rayleigh fading and log-normal shadowing.For a data packet transmission,we formulate an optimization problem,solve the problem,and propose a rate and transmission power adaptation scheme with a restriction methodology of data packet transmission for achieving the optimal energy efficiency.In the restriction methodology of data packet transmission,a user does not transmit a data packet if the instantaneous channel gain of the user is lower than a threshold.To evaluate the performance of the proposed scheme,we develop analytical models for computing the throughput and energy efficiency of WLANs under the proposed scheme considering a saturation traffic condition.We then validate the analytical models via simulation.We find that the proposed scheme provides better throughput and energy efficiency with acceptable throughput fairness if the restriction methodology of data packet transmission is included.By means of the analytical models and simulations,we demonstrate that the proposed scheme provides significantly higher throughput,energy efficiency and fairness index than a traditional non-adaptive scheme and an existing most relevant adaptive scheme.Throughput and energy efficiency gains obtained by the proposed scheme with respect to the existing adapting scheme are about 75%and 103%,respectively,for a fairness index of 0.8.We also study the effect of various system parameters on throughput and energy efficiency and provide various engineering insights.

The Generalized-Fisher composite fading model for the next generation of mobile communication systems

The new generation of communication systems is moving towards using a millimeter-wave spectrum.Since the shadowing effects are undeniable in this type of propagation,the proposed Generalized Fisher(GF)distribution can be useful in modeling shadowed fading channels,considering the non-linearity and the multi-cluster nature of the diffusion medium.After introducing the model,its main statistics,including Probability Density Function(PDF),Cumulative Distribution Function(CDF),Moment Generating Function(MGF),and the distribution of the sum of an arbitrary number of independent and non-identically distributed(i.n.i.d.)random variables with GF distribution are calculated.Subsequently,some wireless communication application criteria such as ergodic and outage capacities,are computed.Finally,considering the classic Wyner's wiretap model and passive eavesdropping scenario,specific security criteria,such as the probability of non-zero secrecy capacity and secrecy outage probability,are also determined.These expressions are measured in terms of either univariate or multivariate Fox's H-function.

Analysis of GPS ionospheric scintillation signal amplitude fading characteristics at low latitude

The received satellite signal amplitude is attenuated greatly due to the strong ionospheric scintillation for lowlatitude regions, which causes the GPS tracking loop＇s loss of lock, the positioning errors to increase, and navigation to be interrupted. To solve the above problems, a novel signal processing algorithm is proposed based on the GPS L1 software receiver during strong ionospheric scintillation using the multi-channel intermediate frequency（IF） data sampling system. Tens of thousands of fading events are obtained based on the signal intensity measurement. The amplitude fading characteristics in the lowlatitude region are analyzed,including fading duration, time separation between fades and the numbers of signal intensity fading events. The fading thresholds are set to be 15 and 10 dB, respectively. The main fading time is very short in- 15 dB fading threshold, which generally is less than 20 ms. The main time separation between fades is less than 2 s in a single one-hour period from the time 23： 00 to 24： 00. Therefore, it has the characteristic of a short reacquisition time for the receiver designed to reduce the probability of simultaneous loss of lock for some satellites.Subsequently, the acquisition, tracking and PVT（position,velocity and time） calculations are completed by the customdesigned software receiver. The results show that the impact analysis of ionospheric scintillation on GPS amplitude attenuation in the lowlatitude region is helpful for designing the advanced tracking algorithm and to improve the robustness and accuracy of the GPS receiver.

Closed BER expression of multi-user DS UWB systemsin indoor fading channel

The bit error rate （BER） performance of multi-user direct spreading bi-phase shift keying （DSBPSK） direct impulse ultra wideband （UWB） systems is analyzed and simulated based on a statistical indoor multi-path fading channel model. The BER of the system is theoretically derived and given in closed form, which is expressed in terms of channel parameters and system parameters such as pulse width parameter, pulse repeat period, user number and pulse waveform. With this BER expression, the effect of these parameters on the system performance can be evaluated in a uniform way. Simulation results well match the theory numerical results, and prove that the multi-access interference （MAI） of DS-BPSK UWB is a normal distribution.

电子音乐中Fade In及Fade Out效果应用

在电子音乐处理手法多如牛毛的今天,人们对电子音乐审美正随着电子音乐地发展而提高。但劣质CD音乐同时抑制着电子音乐的整体发展,影响人们的音乐审美。因此,本文通过对音乐Fade-In及Fade-Out音频前期制作中的情绪辅助表达、录音过程中的音频剪辑、CD成品刻录中的防止爆破三种作用的研究,力图在尽量保持电子音乐高品质的同时,不断的尝试新的操作构思,为电子音乐地发展创新锦上添花。

Multi-access performance of DS UWB systemunder indoor dense multi-path channel

The performance of multi-user code to direct spreading bi-phase shift keying （DS-BPSK） direct impulse ultra wideband （UWB） systems under indoor multi-user and multi-path environment is analyzed and simulated. The system output signals with Rake receiver are derived, then a simple and practical code selection scheme is given; i. e., with a large occupation to empty ratio of the repeating pulses, directly choosing those random or pseudo-random user codes with enough length and good co-relative orthogonal features will make the performance of DS-BPSK approximate the optimum and, so there is no need to carefully design the code or its type. The system multi-access performances are simulated using Gold sequence and PN codes as multi-user codes under CMI-CM4 multi-path channels. Simulation results prove that the proposed scheme is feasible.

Electrochemical behavior and cyclic fading mechanism of LiNi_(0.5) Mn_(0.5) O_2 electrode in LiNO_3 electrolyte

Electrochemical behavior of layered LiNi0.5Mn0.5O2 in LiNO3 aqueous solution and its cyclic fading mechanism in electrolytes with different pH values were investigated. CV results show that LiNi0.5Mn0.5O2 has good electrochemical reversible behaviors in 5 mol/L LiNO3 solution. Meanwhile, the electrode in 5 mol/L LiNO3 with pH value of 12 demonstrates the best electrochemical stability. Based on the electrochemical impedance spectroscopy （EIS）, X-ray diffraction （XRD） and scanning electron microscopy （SEM） results, it is proposed that suppressed charge-transfer resistance is the major reason, which is probably ascribed to the more stable electrode surface and less structure change.

无编程和填表制导开发环境FADE

本文介绍无编程软件应用系统开发环境FADE的设计思想,论述无编程开发工具的类型和特点,填表式制导开发方式的应用系统的生成过程,并给出了表格数据库的文法和语义描述。

复杂环境下无人机组合导航自适应滤波算法

在复杂环境中,无人机(UAW)组合导航系统可能会因量测噪声过大导致定位精度下降。为解决这一问题,提出了一种改进的Sage-Husa自适应滤波算法。首先,采用一种含权重因子的滑动窗口残差卡方检验方法识别故障信号,将系统区分为有/无故障两种状态;然后,在检测出系统故障时,引入可动态调节的遗忘因子估计量测噪声,提高系统的自适应能力;最后,在系统无故障时,引入多重渐消因子修正预测均方误差矩阵,减小陈旧信息对当前滤波的影响。仿真结果表明:改进后的滤波算法可以有效提高故障信号识别准确性以及定位精度。相较于传统Sage-Husa自适应滤波,改进后的算法在东、北、天向定位精度分别提高了46.54%、18.59%及46.24%。

Concatenated Trellis Coding and CPM for DS/SSMA Communications in Rayleigh Fading Channel

In this paper, direct sequence spread spectrum multiple access (DS/SSMA) communication system employing serially concatenated trellis coded modulation (TCM) and continuous phase modulation (CPM) over flat Rayleigh fading channel are presented. The performance of this concatenated TCM/CPM DS/SSMA system is exploited by the theoretical analysis and numerical simulations. The results demonstrate that significant improvements in error probability of this DS/SSMA system over the system with single TCM or CPM of different modulation indices can be achieved under the same conditions.

基于逐尺度卷积的OFDM信道估计算法

针对快衰落信道环境下的无线通信正交频分复用系统中信道估计算法估计难度大、复杂度高等问题,提出一种轻量级的逐尺度卷积信道估计网络(scale-wise convolution channel estimation network,SCCENet)。对输入的信道状态信息矩阵下采样,构建多尺度特征金字塔,通过构建的逐尺度卷积部分以网络权重共享的方式对信道状态信息矩阵构成的多尺度特征金字塔进行不同尺度的特征融合,在不增加网络参数情况下增大感受野。仿真结果表明,该算法估计性能优于最小二乘算法,能以较低的估计复杂度取得相较于其它深度学习信道估计算法更低的估计误差。

应用FADE品质改善模式改善新入院病人护理细节质量

目的应用FADE[focus(确认问题);analyze(问题分析,指出需要了解的事项,并收集资料以决定影响因素);develop(建立计划以解决问题);execute(执行改善计划并追综检讨,FADE]品质改善模式,持续改进新入院病人护理细节质量,确保病人安全。方法 2014年11月—2015年6月应用FADE品质改善模式,确认改进问题为"新入院病人护理细节质量",找出影响新入院病人护理细节质量的主要问题,并针对问题进行根因分析找出影响因素,制定新入院病人护理细节质量标准、改进目标及改进策略,执行计划并追踪检讨持续改进,运用数据评价改进效果。结果实施改进前2014年11月新入院病人护理细节质量合格率为77.9%,实施改进后,2015年1—6月共检查6次,新入院病人护理细节质量平均合格率为92.2%,实施前后合格率比较,差异有统计学意义(P<0.01),有效改进了新入院病人护理工作中存在的问题。结论应用FADE品质改善模式,有效改进了新入院病人护理中存在的问题,提高了新入院病人护理细节质量,确保了病人安全。

Performance and capacity fading reason of LiMn_2O_4/graphite batteries after storing at high temperature

Spinel LiMn204 was synthesized by a solid-state method. A 204468-size battery was fabricated and stored at 55℃. The structure and morphology of the LiMn204 cathode were analyzed by X-ray diffraction （XRD） and scanning electron microscopy （SEM） technique. Energy dispersive spectroscopy （EDS） was used to analyze the surface component of the carbon anode. The discharge capacities of LiMn204 stored for 0, 24, 48, and 96 h are 106, 98, 96, and 92 mAh·g^-1, respectively. The cyclic performance is improved after storage. The capacity retentions of LiMn204 stored for 0, 24, 48, and 96 h are 83.8%, 85.8%, 86.9%, and 88.6% after 180 cycles. The intensity of all the LiMn204 diffraction peaks is weakened. Mn is detected from the carbon electrode when the battery is stored for 96 h. Cyclic voltammograms and electrochemical impedance spectroscopy （EIS） were used to examine the surface state of the electrode after storage. The results show that the resistance and polarization of LiMn2O4/electrolyte is increased after storage, which is responsible for the fading of capacity.

Mechanism of Capacity Fading Caused by Mn(Ⅱ)Deposition on Anodes for Spinel Lithium Manganese Oxide Cell

The capacity fade of spinel lithium manganese oxide in lithium-ion batteries is a bottleneck challenge for the large-scale application.The traditional opinion is that Mn（Ⅱ） ions in the anode are reduced to the metallic manganese that helps for catalyzing electrolyte decomposition.This could poison and damage the solid electrolyte interface（SEI） film,leading to the the capacity fade in Li-ion batteries.We propose a new mechanism that Mn（Ⅱ） deposites at the anode hinders and/or blocks the intercalation/de-intercalation of lithium ions,which leads to the capacity fade in Li-ion batteries.Based on the new mechanism assumption,a kind of new structure with core-shell characteristic is designed to inhabit manganese ion dissolution,thus improving electrochemical cycle performance of the cell.By the way,this mechanism hypothesis is also supported by the results of these experiments.The LiMn2-xTixO4 shell layer enhances cathode resistance to corrosion attack and effectively suppresses dissolution of Mn,then improves battery cycle performance with LiMn_2O_4 cathode,even at high rate and elevated temperature.

Comparison of Two Fading Filters anc Adaptively Robust Filter

Two kinds of fading filters and their principles are introduced. An adaptive robust filter is given with corresponding principle. The basic abilities of the fading filters and adaptively robust filter in controlling the influences of the kinematic model errors are analyzed. A practical example is given. The results of the fading filter and adaptively robust filter are compared and analyzed.

A k-Coverage Scheduling Scheme in Wireless Sensor Network Based on Hard-Core Process in Rayleigh Fading Channel

Sensing coverage is a fundamental design issue in wireless sensor networks(WSNs),while sensor scheduling ensures coverage degree to the monitored event and extends the network lifetime.In this paper,we address k-coverage scheduling problem in dense WSNs,we maintain a connected k-coverage energy efficiently through a novel Hard-Core based Coordinated Scheduling(HCCS),in which hardcore is a thinning process in stochastic geometry that inhibits more than one active sensor covering any area redundantly in a minimum distance. As compared with existing coordinated scheduling,HCCS allows coordination between sensors with little communication overhead.Moreover,due to the traditional sensing models in k-coverage analysis is unsuitable to describe the characteristic of transmit channel in dense WSNs,we propose a novel sensing model integrating Rayleigh Fading and Distribution of Active sensors(RFDA),and derive the coverage measure and k-coverage probability for the monitored event under RFDA. In addition,we analyze the influence factors,i.e. the transmit condition and monitoring degree to the k-coverage probability. Finally,through Monte Carlo simulations,it is shown that the k-coverage probability of HCCS outperforms that of its random scheduling counterpart.