Performance analysis of DFT spread generalized multi-carrier systems

Discrete Fourier transform-spread generalized multi-carrier （DFT-S-GMC） based single carrier-frequency division multiple access （SC-FDMA） scheme is a promising solution for uplink transmission of broadband wireless communication. In this paper, the impact of non-perfect orthogonal prototype filter to the performance of the DFT-S-GMC system is discussed. Single sub-band frequency-domain equalization （FDE） method is presented and the performance loss caused by FDE-tone discarding is analyzed. Moreover, the post-processing signal to interference plus noise ratio （SINR） of DFT-S-GMC receiver over multi-path channel is addressed. The theoretical analysis illustrates that the non-perfect orthogonal prototype filter results in inter-symbol interference （ISI） and inter-sub-band interference （IBI）, and the variance of the ISI is still less than le-4 and much larger than that of IBI. By designing proper system parameters, the reconstruction error due to FDE-tones discarding can be controlled under -40 dB; the post-processing SINR of the DFT-S-GMC receiver with minimum mean square error （MMSE） equalization is higher than that with zero forcing （ZF） equalization. The theoretical performances are verified by extensive simulation results.

Recognition of multi-carrier OFDM and single-carrier with alpha-stable distribution noise

In order to identify the multi-carrier orthogonal frequency division multiplexing(OFDM) and the single-carrier signal in the non-Gaussian noise environment, different features of the two signals are analyzed in terms of five parameters: generalized normalized fourth-order cumulant, the maximum value of the instantaneous amplitude power spectral density, absolute standard deviation of instantaneous phase on the section with weak signals, and position and numbers of the generalized cyclic spectrum's peak. The recognition method of the multi-carrier OFDM and single-carrier signal is proposed in the environment with alpha-stable distribution noise. Simulation results show that the recognition rate of the multi-carrier OFDM can reach 100% when the mixed signal to noise ratio(MSNR) is greater than-5 dB and the recognition rate can reach 90% for the single-carrier when the MSNR is greater than 2 dB.

ICI elimination of M-band wavelet multi-carrier modulation system

To solve the inter carrier interference （ICI） elimination problem of an M-band wavelet multi-carrier modulation system, this paper analyzes the principle of the ICI caused by the Doppler frequency shift and its mathematical expression based on the M-band wavelet multi-carrier modulation system model. Through the analysis of the mathematical expression and combining with the perfect reconstruction conditions of the filter banks, we propose the design conditions of an M-band filter to reduce and eliminate the ICI. The impulse response model of the filter design conditions and an iterative algorithm is also established. The simulation results show that the proposed ICI reduction and elimination methods can effectively improve the system performance.

Multi-carrier transport in ZrTe_5 film

Single-layered zirconium pentatelluride （ZrTes） has been predicted to be a large-gap two-dimensional （2D） topolog- ical insulator, which has attracted particular attention in topological phase transitions and potential device applications. Herein, we investigated the transport properties in ZrTe5 films as a function of thickness, ranging from a few nm to several hundred nm. We determined that the temperature of the resistivity anomaly peak （Tp） tends to increase as the thickness decreases. Moreover, at a critical thickness of ~ 40 rim, the dominating carriers in the films change from n-type to p-type. A comprehensive investigation of Shubnikov-de Hass （SdH） oscillations and Hall resistance at variable temperatures revealed a multi-carrier transport tendency in the thin films. We determined the carrier densities and mobilities of two majority car- riers using the simplified two-carrier model. The electron carriers can be attributed to the Dirac band with a non-trivial Berry phase ~, while the hole carriers may originate from surface chemical reaction or unintentional doping during the microfabrication process. It is necessary to encapsulate the ZrTe5 film in an inert or vacuum environment to potentially achieve a substantial improvement in device quality.

On the Characteristic of Orthogonality for Multi-Carrier-Based Systems

The dominate factors caused by reasons of losing the orthogonality in fading channel including FBC (fading branch correlation), CFO (carrier frequency offset), and even the CPN (carrier phase noise) are novel discussion in this letter. The first one factor causes the ISI (inter-symbol interference), and, however, the latter two will lead to the phenomenon of CPE (common phase error) and ICI (inter-carrier interference). On the other hand, they will lead to the loss of orthogonality for the radio system with multi-carrier modulating schemes, i.e., both them mainly deteriorate a wireless communication system. Eventually, in this letter not only the analytical expressions are derived, but a three dimension numerical results from the analysis involve the three parameters also illustrated is.

Enhancing Wind Power Integration through Optimal Use of Flexibility in Multi-Carrier Energy Systems from the Danish Perspective

Denmark’ goal of being independent of fossil energy sources in 2050 puts forward great demands on all energy subsystems (electricity, heat, gas and transport, etc.) to be operated in a holistic manner. The Danish experience and challenges of wind power integration and the development of district heating systems are summarized in this paper. How to optimally use the cross-sectoral flexibility by intelligent control (model predictive control-based) of the key coupling components in an integrated heat and power system including electrical heat pumps in the demand side, and thermal storage applications in buildings is investigated.

基于CP重构的高时间传输效率CP-UFMC接收方法

针对循环前缀(cyclic prefix,CP)不足的情况对循环前缀通用滤波多载波(cyclic prefix-universal filtered multi-carrier,CP-UFMC)系统的影响进行了数学推导,提出了一种基于CP重构的高时间传输效率CP-UFMC接收方法来改善系统性能,并进一步研究了选择性重构方法的性能。之后仿真研究了不同CP长度,不同载波频率偏移和不同正交振幅调制阶数时的系统误符号率(symbol error rate,SER)表现。仿真结果表明,基于CP重构的CP-UFMC接收方法可以改善CP不足导致的系统SER恶化问题,使其接近CP充足时的SER,并优于对比的其他通用滤波多载波系统接收方法。

A design scheme for interference suppression based on CWBIM

An interference suppression design scheme based on conjugate weighted butterfly interleaving mapping(CWBIM)is proposed for inter-carrier interference(ICI)and inter-subband interference(IBI)in the received signals of universal filtered multi-carrier(UFMC)systems.It applies an interleaving mapping operation to subtract the interference coefficients of adjacent terms in ICI and IBI twice,thereby achieving suppression effects similar to the self-cancellation(SC)algorithm while maintaining the original data transmission efficiency.Meanwhile,conjugate and complex weighting operations can effectively suppress the impact of phase rotation errors in high-speed mobile channel environments,thereby further improving the bit error rate(BFR)performance of the system,Moreover,butterfly operation can effectively control the computational complexity of the interleaving mapping process.Theoretical analysis and simulation results show that,compared with the PSC-UFMC algorithm,the CWBIM-UFMC scheme proposed in this paper can effectively suppress ICI and IBI in the received signal without compromising data transmission efficiency and reducing computational complexity,thereby achieving good BER performance of the system.

多能源互补分布式能源系统集成研究综述及展望

分布式能源系统是能源革命发展的重要载体和推进手段,将在未来能源体系中占据重要地位;同时多能源互补是其发展的主要方向和关键特征,开展多能源互补分布式能源系统相关研究对我国的能源转型具有重要的意义。该文从资源量化表征与需求预测、多能流建模、系统集成与规划、运行优化与主动能量调控、以及能源系统综合评价等5个方面对多能源互补分布式能源系统集成的发展现状进行分析,探讨未来可能的发展趋势和面临的挑战,为多能互补分布式能源系统未来基础及应用研究和行业发展提供一定的参考和建议。

双功能雷达通信系统的多用户功率分配算法

为解决传统多用户双功能雷达通信系统因载波分配导致通信性能较差的问题,提高双功能雷达通信系统的资源利用率,提出了一种通信用户载波共享模型下的多用户功率分配方案,并通过构造合理的资源分配问题使得系统具有更优的通信性能。首先,建立双功能雷达通信系统的通信用户载波共享信号模型。其次,为保证双功能雷达通信系统性能,构造了以系统通信和速率最大并满足雷达信噪比下界、总功率和用户功率约束的优化问题,通过理论分析严格证明了优化问题的可行性。最后,为求解凸优化问题,提出一种多用户功率分配算法,通过引入辅助变量对目标函数进行二次转换,将其分解为两个优化子问题,继而通过交替迭代的方式进行求解。研究结果表明,相较于传统通信用户载波分配模型,优化后的通信用户载波共享模型通信和速率提高了约40%,从而验证了所提方案具有更优的通信性能,有效提高了系统资源利用率。本研究成果为提高多用户双功能雷达通信系统的通信性能提供了一种新思路和手段。

基于神经网络的编码压扩联合峰均比降低技术

多载波调制技术是当下宽带通信系统中常用的一种先进的调制方式,然而,多载波信号在时域上会产生非常大的峰均功率比(PAPR),这将导致信号非线性损伤,严重影响信号传输性能与通信质量。文章提出了基于神经网络的频域编码和时域压扩联合PAPR降低方案,频域编码采用一层全连接层来实现,极大降低了复杂度和网络训练难度,同时引入小比例的扩频用以提供编码增益,时域压扩网络采用了非线性的卷积神经网络来降低PAPR。通过在各种参数条件下的仿真展示了该方案的效果,并与多种方案对比。仿真结果表明,该方案在引入极小失真下,PAPR可降低5 dB。最后,对该方案进行了实验验证,结果表明,在降低PAPR 5 dB情况下,该方案的误码率(BER)性能相比剪切方案降低了75%,验证了方案的可行性。

Selective Harmonics Elimination Technique for Artificial Bee Colony Implementation

In this research,an Artificial Bee Colony(ABC)algorithm based Selective Harmonics Elimination(SHE)technique is used as a pulse generator in a reduced switch fifteen level inverter that receives input from a PV system.Pulse width modulation based on Selective Harmonics Elimination is mostly used to suppress lower-order harmonics.A high gain DC-DC-SEPIC converter keeps the photovoltaic(PV)panel’s output voltage constant.The Grey Wolf Optimization(GWO)filter removes far more Photovoltaic panel energy from the sunlight frame.To eliminate voltage harmonics,this unique inverter architecture employs a multi-carrier duty cycle,a high-frequency modulation approach.The proposed ABC harmonics elimination approach is compared to SHE strategies based on Particle Swarm Optimization(PSO)and Flower Pollination Algorithm(FPA).The suggested system’s performance is simulated and measured using the MATLAB simulation tool.The proposed ABC approach has a THD level of 4.86%,which is better than the PSO and FPA methods.

抑制癌症治疗多药耐药性的纳米药物递送体系

多药耐药(MDR)是指肿瘤细胞对传统和新型化疗药物产生耐药性的现象,成为治疗恶性肿瘤的重要障碍。近年来,已发现纳米药物递送体系(NDDS)在抑制肿瘤MDR方面表现出独特优势,可增加药物的溶解度和稳定性,避开药物外排泵、以更低的剂量和更少的副作用实现目标部位更高的药物浓度。因此,NDDS成为克服癌症MDR的有效策略。介绍了肿瘤MDR机制;从多肽类配体、叶酸靶向配体、转铁蛋白靶向配体、透明质酸配体、双配体及其他配体5个方面总结了辅助纳米粒子克服MDR的研究进展;综述了内源性及外源性刺激响应型纳米药物的设计、结构以及克服MDR的效果;提出了抑制癌症治疗多药耐药性的NDDS存在的问题及未来发展方向。

新型电力系统环境下FBMC系统信道估计

移动无线通信在新型电力系统的发电、输电、配电、变电、用电等环节中都有着广泛的应用场景,滤波器组多载波(Filter Bank Multi-carrier,FBMC)技术作为一种新型无线通信方式,相比4G应用的正交频分复用(Orthogonal Frequency Division Multiplexing,OFDM)技术有着频带利用率高、带外功率泄漏低、无须循环前缀等优点,但也存在计算复杂度高、虚部干扰难以消除等缺点,对信道估计环节接收信号的恢复造成影响。为高效解决FBMC系统信道估计问题,结合压缩感知思想,利用稀疏度自适应匹配追踪(Sparse Adaptive Match Pursuit,SAMP)算法与离散傅里叶变换(Discrete Fourier Transform,DFT)算法,设计并完成信号恢复实验以及FBMC系统信道估计仿真实验,随机信号恢复实验验证了SAMP算法的重构性能,在FBMC系统信道估计仿真实验中,将提出的算法与SAMP、子空间追踪(Subspace Pursuit,SP)、正交匹配追踪(Orthogonal Matching Pursuit,OMP)等常见压缩感知算法充分比较,结果证明该算法相比其他传统算法有更低的误码率和更低的均方误差。

数字信道化多载波卫星通信系统的优化设计

针对多载波星载通信系统,文章建立了一种基于数字信道化的多载波星载通信系统的链路支撑优化模型。通过对此模型的求解,可以获得每个子信道的最优增益以及每个子链路的最优传输功率。然后,研究一种链路支持模式下的卫星接收系统,以减小各载波间的功率差别,实现系统工作点向饱和点移动。由此,提高了接收机的能量利用效率,从而促进我国通信事业的发展。

基于协同平衡的可靠性冗余设计优化算法

可靠性冗余设计优化是航天装备研发工作的重点之一。在系统可靠性平衡优化的基础上提出了协同平衡的新概念,即利用单元协同变化实现复杂系统可靠性冗余设计的进一步优化。所提算法充分考虑冗余单元变化对复杂系统可靠度、费用、体积、质量和功耗等性能参数的影响,可以解决各类可靠性冗余设计优化问题。计算结果表明基于单元协同平衡的可靠性冗余设计优化算法可以有效实现可靠性冗余设计的优化目标,同时具有计算成本低、效率高等优点。

一种改进的多载波并行组合扩频通信系统

本文结合正交频分复用技术和并行组合扩频技术,在原有的并行组合扩频技术上加以改进,提出一种新的多载波并行组合扩频通信方式,与原有的PCSS-OFDM通信技术相比,在带宽相同的情况下,提高了频带利用率和数据传输速率。并使用MATLAB对该系统在AWGN信道、多径信道、非线性放大和多音干扰的情况下进行仿真验证。结果表明与单载波并行组合扩频技术和未改进的多载波并行组合扩频技术相比,改进的多载波并行组合扩频技术误码率更低,更适用于复杂信道以及其他恶劣的通信环境。

基于多变量约束的GNSS瞬时姿态确定方法

传统的直接定姿法或最小二乘法依赖于整周模糊度的成功固定。当卫星数目较少或存在干扰的情形下,模糊度固定成功率会大大降低,进而导致定姿结果不准确。因此,提出基于多变量约束的姿态确定方法,所提方法将整周模糊度和姿态确定视作联合问题进行解算且对基线长度没有限制。利用天线的几何信息和姿态矩阵的正交特性对观测模型进行多变量约束,能够有效提升模糊度固定成功率并实现瞬时定姿。仿真结果表明:即使在信号观测精度非常低的场景下,所提方法也能达到75.7%的模糊度固定成功率;即使只有4颗卫星,所提方法也能达到90%以上的成功率。且在使用超短基线的前提下,所提方法能够达到0.93°的定姿精度。

LTE-A载波聚合下的载波切换分析

多载波聚合技术是LTE-A(LTE-advanced)系统的一个关键技术,它能解决LTE-A系统对带宽资源的需求。由于不同频带的信号传输功率、覆盖范围不尽相同,使得终端在小区间的切换成为难点。本文在LTE切换流程的基础上分析了LTE-A载波聚合环境下的载波切换场景、小区内及小区间的载波切换流程,为了减少多载波切换的失败率,提出了同时向多个符合条件的相邻小区发出切换请求并选择其中最佳小区进行切换的改进思路,同时针对多目标eNB切换方式设计了两种多载波切换方法。

CDMA系统中的空时发射分集方案及其在MIMO MC-CDMA中应用的研究

本文结合了空时发射分集技术能够有效地对抗信道衰落、提高系统容量和多载波码分多址(MC CD-MA)具有高效频谱利用率、对频率选择性信道鲁棒性的优点,提出了CDMA系统中两种新的空时发射分集方法,研究了这两种空时发射分集方法在MIMO MC-CDMA系统中的应用,并与基于空时分组编码的发射分集方法分别在MIMOCDMA和MIMO MC-CDMA两种系统下进行了仿真比较.