A Novel High Spectral Efficiency Waveform Coding-OVFDM

Based on the Overlapped Multiplexing Principle[12],a frequency domain OVFDM(Overlapped Frequency Domain Multiplexing) Coding is proposed.By the data weighted shift overlapped version of any band-limited Multiplexing Transfer Function H(f) the coding gain and spectral efficiency are both achieved.The heavier the overlap of the data weighted Multiplexing Transfer Function H(f),the higher the coding gain and spectral efficiency as well as the closer the output to the optimum complex Gaussian distribution.The bit error probability performance is estimated.The time domain OVTDM(Overlapped Time Domain Multiplexing) Coding,the dual of OVFDM in time domain is incidentally proposed as well.Both theoretical analysis and testified simulations show that OVFDM(OVTDM) is suitable for high spectral efficiency application and its spectral efficiency is only roughly linear to SNR rather than the well-known logarithm to SNR.

ANALYSIS OF SPECTRAL PHASE ENCODING OCDMA SYSTEM WITH PSEUDORANDOM CODING

Multiple access interference (MAI) is the most serious interference in spectral phase encoding optical code division multiple access (SPE OCDMA) systems. This paper focuses on the behavior of MAI in SPE OCDMA systems with pseudorandom coding. The statistical expectation of multi access interference (MAI) is derived and plotted. The results confirm that MAI can be suppressed effectively by pseudorandom coding with m sequences.

Piecewise spectrally band-pass for compressive coded aperture spectral imaging

Coded aperture snapshot spectral imaging(CASSI) has been discussed in recent years. It has the remarkable advantages of high optical throughput, snapshot imaging, etc. The entire spatial-spectral data-cube can be reconstructed with just a single two-dimensional(2D) compressive sensing measurement. On the other hand, for less spectrally sparse scenes,the insufficiency of sparse sampling and aliasing in spatial-spectral images reduce the accuracy of reconstructed threedimensional(3D) spectral cube. To solve this problem, this paper extends the improved CASSI. A band-pass filter array is mounted on the coded mask, and then the first image plane is divided into some continuous spectral sub-band areas. The entire 3D spectral cube could be captured by the relative movement between the object and the instrument. The principle analysis and imaging simulation are presented. Compared with peak signal-to-noise ratio(PSNR) and the information entropy of the reconstructed images at different numbers of spectral sub-band areas, the reconstructed 3D spectral cube reveals an observable improvement in the reconstruction fidelity, with an increase in the number of the sub-bands and a simultaneous decrease in the number of spectral channels of each sub-band.

Degradation of effective carrier-power-to-noise densityratio based on code trackingspectral sensitivitycoefficient for GNSS radio frequencycompatibilityin C band

The frequency band between 5 010 MHz and 5 030 MHz allocated as C band has been used as a candidate in the global navigation satellite systems （GNSS） along with more and more naviga- tion services in L band. The potential benefits and technical requirements of C band for satellite navi- gation have been analyzed before. However the degradation of effective carrier-power-to-noise densi- ty ratio（ A （C/No ）eu） based on code tracking spectral sensitivity coefficient（ CT_SSC ） as a compati- bility assessment methodology for potential GNSS radio frequency compatibility in C-Band has not been discussed clearly. So the compatibility of the signals in the C band between BeiDou （BD） B1 C and GPS L1C, L1C/A, Galileo E1Os as the interoperability or classical signals in L band is analyzed. Simulation results reveal the interference degree between BD III B1C and GPS L1C/A, L1C, Galileo E1OS. The results can also reveal that the multiplexed binary offset carrier （MBOC） and binary phase shift keying （BPSK） modulation is not appropriate for C band.

编码孔径快照光谱成像重构算法综述

光谱图像含有丰富的空间和光谱信息,能够反映目标的组成、结构和材料特性,在航天遥感、医疗诊断和机器视觉等领域具有重要的应用价值.近年来,光谱成像技术作为热点研究领域受到广泛关注.传统光谱成像技术采用沿空间维度或光谱维度扫描的方式,依次获取待测物体表面的光谱信息.由于曝光时间较长,传统光谱成像技术不适用于拍摄动态场景.编码孔径快照光谱成像(Coded Aperture Snapshot Spectral Imaging,CASSI)是光谱成像的前沿技术方案,能够从单次曝光中快速获取动态场景的光谱图像,其包括两个阶段:对高维光谱图像的“编码降维采集”和对低维观测图像的“解码升维重构”.CASSI的早期研究聚焦于“编码降维采集”,通过物理系统设计提升图像编码的有效性,包括编码模板设计和双相机系统设计.目前,CASSI的“编码降维采集”物理系统趋于稳定,其“解码升维重构”决定了光谱成像的质量和效率.本文综述CASSI的重构算法.首先介绍CASSI的物理系统和前向模型,详细描述物理系统的组成元件和硬件参数,推导CASSI前向模型的数学表达;其次梳理CASSI重构的特点和挑战,其挑战主要存在于系统前向模型、先验表示模型、算法灵活性、算法复杂度、实物数据集等方面;之后重点归纳重构算法的研究现状,包括基于优化模型的重构算法和基于深度学习的重构算法.基于优化模型的重构算法利用凸优化模型求解线性逆问题,结合平滑、稀疏、低秩等手工设计的先验表示模型降低逆问题的欠定性;基于深度学习的重构算法利用数据驱动的方式建立先验表示模型,结合端到端全网络、深度展开、即插即用等框架求解重构图像.接着比较主流算法的重构质量和计算效率,以峰值信噪比、结构相似度、光谱角制图为重构质量的评价指标,以模型参数量、浮点计算量为计算效率的评价指标.最后讨论现有工作的不足和未来研究趋势,指出当前仍未解决的领域痛点,展望进一步的研究方向,为本领域开拓创新提供参考.

基于合并码本的码字位置序号调制SCMA方案

为满足后5G及未来6G时代对通信系统可靠性及频谱效率(spectral efficiency,SE)的严苛要求,针对上行稀疏码多址接入(sparse code multiple access,SCMA)系统,提出了一种基于合并码本的码字位置序号调制SCMA方案。该方案在时域拓展码字位置,使得码字位置全填充且由其序号携带额外信息比特,并能通过改变码字位置数和序号调制阶数灵活调整系统的谱效。此外,设计了基于消息传递算法(message passing algorithm,MPA)的联合检测算法,并给出了合并码本设计准则。系统分析及仿真结果表明,相较于其他序号调制方案,所提方案更好地兼顾了可靠性与SE,在误比特率(bit error rate,BER)性能与鲁棒性方面都有优势。

一种基于张量字典学习的光谱图像稀疏编码方法

光谱图像与传统RGB图像不同,光谱图像包含有连续的光谱曲线,这些信息对目标识别,目标分类等领域有着很高的应用价值。但是当光谱分辨率较高时,光谱图像数据量剧增,将占用更多的存储空间,为光谱图像的储存和传输带来了难度。因此,本文提出了一种基于张量字典学习的光谱图像稀疏编码方法,主要通过将光谱图像以张量的形式进行表示,增强数据之间的空间相关性;在保证图像不失真的前提下使用先验的光谱字典对光谱图像进行稀疏编码,通过储存该稀疏编码代替原始数据,从而减低降低光谱图像储存量。

Robust key point descriptor for multi-spectral image matching

Histogram of collinear gradient-enhanced coding （HCGEC）, a robust key point descriptor for multi-spectral image matching, is proposed. The HCGEC mainly encodes rough structures within an image and suppresses detailed textural information, which is desirable in multi-spectral image matching. Experiments on two multi-spectral data sets demonstrate that the proposed descriptor can yield significantly better results than some state-of- the-art descriptors.

Pragmatic Approach to Adaptive Turbo Coded Modulation

This paper presents a pragmatic adaptive scheme for TuCM over slowly fading channels. The adaptive scheme employs a single turbo coded modulator composed of a variable-rate turbo encoder and a variable-rate variable-power MQAM for all fading regions, so it has an acceptable complexity to implement. The optimal adaptive TuCM scheme is determined subject to various system constraints. Simulations have been performed to measure the performance of the scheme for different parameters. It is shown that adopting both the turbo coded modulator and the transmit power achieves a performance within 2.5 dB of the fading channel capacity.

Performance of Cross-Layer Design with Power Allocation in Space-Time Coded MIMO Systems

A cross-layer design(CLD)scheme with combination of power allocation,adaptive modulation(AM)and automatic repeat request(ARQ)is presented for space-time coded MIMO system under imperfect feedback,and the corresponding system performance is investigated in a Rayleigh fading channel.Based on imperfect feedback information,a suboptimal power allocation(PA)scheme is derived to maximize the average spectral efficiency(SE)of the system.The scheme is based on a so-called compressed SNR criterion,and has a closed-form expression for positive power allocation,thus being computationally efficient.Moreover,it can improve SE of the presented CLD.Besides,due to better approximation,it obtains the performance close to the existing optimal approach which requires numerical search.Simulation results show that the proposed CLD with PA can achieve higher SE than the conventional CLD with equal power allocation scheme,and has almost the same performance as CLD with optimal PA.However,it has lower calculation complexity.

PERFORMANCES OF ADAPTIVE MODULATION AND CODING IN SATELLITE MOBILE CHANNEL

Given that satellite mobile channel is a time-varying channel,Adaptive Modulation and Coding(AMC) was proposed to provide robust and spectrally efficient transmission over satellite mobile channel.Three different kinds of channel environment were considered in this paper:the urban area,the rural area,and the open space.Four combinations of modulation and coding were designed to meet reliable communication on time-varying channel,and spectral efficiency and system throughput of these three kinds of channel environment were simulated.Based on the simulation results,this paper analysed the results and compared the performances of AMC with non-AMC system in these three kinds of channel environment.At last,we come to the conclusions:a system with AMC can achieve higher spectral efficiency and better system throughput;and the spectral efficiency and system throughput of AMC system will be higher on better satellite mobile channel.

Efficiency Improvement of Space Time Block Codes

Unlike most of the existing methods in Space Time coding (STC) system which focus on design of STC gaining full rate and/or maximum diversity, we propose an approach to improve spectral efficiency of the code. The proposed scheme carries more information symbols in each transmission block as compare to its counterpart code, and yet retains the property of simple decoding. Simulation results show that transmit diversity is retained with improvement of code efficiency. We mainly focus on Four transmit antenna scheme but it can be generalized for any number of transmit antennas.

Dual Adaptive Turbo Coded Modulation for Integrated Multimedia Service Transmission

This paper proposes a cross-layer dual adaptive coded modulation architecture using turbo codes for mobile multimedia communication, which adapts to both the varying channel characteristics and the QoS of various multimedia services simultancously to increase the average system throughput substantially. A pragmatic channeladaptive turbo coded modulation schcme, which comes within 2.5 dB of the Shannon limit, is optimally designed, and then a QoS-adaptive scheme is superimposed to build the dual adaptive architecture. Simulation results show that the novel dual adaption reduces the gap from the fading channel capacity to 2 dB when assuming different services occur in equal probability and the service duration follows exponential distribution.

A channel- and QoS-adaptive turbo coded modulation architecture for mobile multimedia communication

This paper proposed a cross-layer dual adaptive coded modulation architecture using turbo codes for mobile muhimedia communication, which simultaneously adapted to both the varying channel characteristics and the quality of service （QoS） of various mobile multimedia services to increase the average system throughput substantially. A pragmatic channel-adaptive turbo coded modulation scheme, which comes within 2.5dB of the Shannon limit, was optimally designed, and then a QoS-adaptive scheme was superimposed to build the dual adaptive architecture. Simulation results show that the novel dual adaption reduces the difference with the fading channel capacity to 2dB when assuming different services occur in equal probability and the service duration follows the exponential distribution.

Spectral Properties of Yellow Fluorescent Powder for White LEDs

Much attention has been paid to white LEDs because of their potential applications in the illumination.The doping of rare earth ions plays an important role in the optical properties of yellow fluorescent powder.And mainly aiming to raise the intensity and the luminous rate of the white LEDs and by photoluminescence and electroluminescence,the luminescence spectrum of yellow fluorescent powder bought from different places is measured.Furthermore, the luminous intensity in the normal direction and the angle distribution of half maximum power for the white LEDs packed with cylindrical Φ 5 epoxy on the same blue GaN chips are also measured under the same manufacture conditions. The results show that the yellow fluorescent powder bought from China mainland has higher optical output rate than that bought from China Taiwan and hence is more suitable to fabricate the white LEDs for practical use.

Modulation for Digital Radio Broadcasting Using Amplitude Autocorrelation of Pseudo Random Noise Codes to Carry Information

The frequency bands used in mobile communications are allocated according to the type of application. With the need for more channels, the frequency spectrum has become a scarce natural resource. This study shows the results of a proposed modulation using a variation of the autocorrelation of pseudo-random codes to carry information. The work also presents the generation of multiple orthogonal axes to increase the bit rate thus improving the channel efficiency.

直接序列扩频非正交分组码索引调制技术研究

为了进一步提高传统码索引调制(Code Index Modulation, CIM)的误码率性能和降低伪随机(Pseudo Noise, PN)码索引资源的耗费量,提出非正交分组-码索引调制(Nonorthogonal Grouping-Code Index Modulation, NG-CIM)方案。NG-CIM在发送端将每一个传输时隙并行分为调制块和映射块,调制块通过比特分组后映射成为多组调制符号,映射块为各组调制符号的正交分量和同相分量索引相同的PN码进行直接序列扩频传输。仿真结果表明,在加性高斯白噪声信道中,随着频谱效率的提升,NG-CIM的误码率性能较CIM有着约2~4dB的改善,同时PN码资源的耗费量也大大减少。

编码孔径中红外光谱成像系统的光谱重构算法

针对一款基于双DMD的光谱维编码中波红外光谱成像系统的应用需求,在经典的Hadamard变换完备编码理论基础上,提出了一种具有最大信噪比增益的编码矩阵。结合基于双DMD的光谱维编码中波红外光谱成像系统的光路结构和工作原理,探讨了光谱维DMD所加载的编码模板的设计方法。建立了区块化光谱重构算法的数学模型,并进行了实验验证。实验结果表明,原理样机在具有良好的光谱成像能力的基础上,能够实现较高实时性的凝视成像,其在低光谱分辨率模式下光谱数据立方体帧频能够达到22.35帧/s,验证了区块化光谱重构算法的有效性。

数字微镜器件光谱成像技术进展

数字微镜器件(DMD)作为一种灵活、可编程、可独立寻址的空间光调制器件,广泛地应用于无掩膜光刻、光束整形、全息成像、共焦测量等领域。在光谱成像领域,DMD能够对成像视场进行精细可控的调制,从而代替传统的机械掩膜版和机械扫描结构。综述了近年来DMD在光谱成像领域的研究进展和应用情况,详细论述了基于DMD的编码孔径和推扫式光谱成像系统的光学系统基本结构及工作原理;梳理了基于DMD的光谱成像系统从哈达玛变换光谱成像到推扫式光谱成像的发展脉络;详细介绍了研究人员为克服DMD微镜的衍射以及像面倾斜等像差所做的相关研究工作。最后,总结了基于DMD的光谱成像技术的独特优势,讨论了基于DMD的光谱成像技术未来的发展方向与应用前景。