Performance evaluation of high rate space?time trellis-coded modulation using Gauss?Chebyshev quadrature technique

The performance analysis of high rate space-time trellis-coded modulation (HR-STTCM) using the Gauss-Chebyshev quadrature technique is presented. HR-STTCM is an example of space-time codes that combine the idea used in trellis coded modulation (TCM) design that is signal set expansion and set partitioning into its construction. HR-STTCM construction is based on the concatenation of an outer TCM encoder and inner space-time block code. This paper evaluates the exact pairwise error probability of HR- STTCM based on the Gauss-Chebyshev quadrature formula. Comparison of numerical and simulation results shows that the proposed method is accurate. The method used is shown to be computationally simpler than those in the literature.     

码率嵌入式高码率差分空时编码

为了提高传输码率,将具有高码率的全分集全码率(FDFR)空时码嵌入到低码率的传统差分空时编码中,提出了一种码率嵌入式的差分空时编码方法,该编码方案具有编码增益高,误码性能好等优点.仿真结果表明,与传统的差分空时编码方案(酉差分空时编码和差分空时分组编码)相比,新编码方法具有很好的误码性能,特别是在高传输码率和接收天线较多情况下,其误码性能优势越明显.     

On the capacity of orthogonalised correlated MIMO channels under different adaptive transmission techniques

Orthogonal space-time block codes (STBCs) are known to orthogonalise the multiple-input multiple-output (MIMO) wireless channel, thus reducing the space-time vector detection to a simpler scalar detection problem. The capacity of STBCs over correlated Rayleigh and Ricean flat-fading MIMO channels under different adaptive transmitting techniques is studied. Three adaptive schemes known as optimal power and rate allocation, total channel inversion with fixed rate policy and its truncated variant are studied. Taking into account the effect of channel correlation, closed-form expressions are obtained for the capacity of orthogonalised Rayleigh and Ricean MIMO channels under these adaptive transmission techniques in order to avoid Monte-Carlo simulations     

General differential modulation scheme for quasi-orthogonal space?time block codes with partial or full transmit diversity

A general and simple differential modulation scheme that can be applied to both partial-diversity quasi-orthogonal space-time block codes and full-diversity quasi-orthogonal space-time block codes is reported. A new class of quasi-orthogonal coding structures is presented for various number of transmit antennas. Differential encoding and decoding can be simplified to differential Alamouti codes by grouping the signals in the transmitted matrix and decoupling the detection of data symbols, respectively. For the codes with partial transmit diversity, the new scheme can achieve constant amplitude of transmitted signals, and avoid signal constellation expansion; in addition, it has a linear signal detector with very low complexity. Simulation results show that these partial-diversity codes can provide very useful results at low signal-to-nose ratio for current communication systems. For codes with full transmit diversity achieved by constellation rotation, the proposed scheme has performance equal to the best full-rate quasi-orthogonal schemes previously described in the literature with the benefit of a simpler detector. Moreover, a simple linear detector is also presented for the case when two orthogonal ASK constellations are used. Extension to more than four transmit antennas is also considered.     

Closed-form expressions for symbol error probability of orthogonal space?time block codes over Rician?Nakagami channels

The performances of orthogonal space-time block codes (OSTBCs) over Rician- Nakagami channels are investigated. In particular, we derive closed-form symbol error probability (SEP) expressions for OSTBC systems in which M-ary phase-shift-keying modulation and M-ary quadrature-amplitude modulation are used. These SEP results are expressed in terms of Lauricella's multivariate hypergeometric functions, which can be easily evaluated numerically. When the Rician-Nakagami channel degenerates to the Rician-Rayleigh channel, or equivalently the Rayleigh fading channel, the closed-form SEP expressions are rewritten in terms of higher transcendental functions, that is, Gauss hypergeometric function and Appell hypergeometric function.     

MIMO水声通信中的空时分组扩展编码方案探讨

采用多输入多输出（MIMO）结构和空时编码可以使水声通信系统获得分集增益,改善系统性能。针对水声信道中的频率选择性衰落,研究了一种用于MIMO水声通信系统的空时分组扩展编码方案（STBSC）,利用正交扩频编码克服了水声信道中多径干扰对空时分组编码（STBC）信号正交性的破坏。给出了方案的系统模型和实现框图,采用MIMO水声模型对方案的性能进行了仿真。仿真结果表明,STBSC方案在多径水声信道中可以得到完全发射分集。最后介绍了方案的水库试验,试验结果表明了方案的有效性。     

Space-time compressive imaging

Compressive imaging systems typically exploit the spatial correlation of the scene to facilitate a lower dimensional measurement relative to a conventional imaging system. In natural time-varying scenes there is a high degree of temporal correlation that may also be exploited to further reduce the number of measurements. In this work we analyze space-time compressive imaging using Karhunen-Loève (KL) projections for the read-noise-limited measurement case. Based on a comprehensive simulation study, we show that a KL-based space-time compressive imager offers higher compression relative to space-only compressive imaging. For a relative noise strength of 10% and reconstruction error of 10%, we find that space-time compressive imaging with 8×8×16 spatiotemporal blocks yields about 292× compression compared to a conventional imager, while space-only compressive imaging provides only 32× compression. Additionally, under high read-noise conditions, a space-time compressive imaging system yields lower reconstruction error than a conventional imaging system due to the multiplexing advantage. We also discuss three electro-optic space-time compressive imaging architecture classes, including charge-domain processing by a smart focal plane array (FPA). Space-time compressive imaging using a smart FPA provides an alternative method to capture the nonredundant portions of time-varying scenes.     

Cascaded generalised-K fading channel

A versatile fading distribution that generalises many commonly used models for multi-path and shadow fading is the so-called generalised-K (KG) distribution. By considering the product of N independent but not necessarily identically distributed (n.i.d.) squared KG random variables (RVs), we derive exact closed-form expressions for the moment generating function, probability density function, cumulative distribution function and the moments of the cascaded KG fading channel. Expressions for the ergodic capacity and the error performance of different digital modulation schemes are also obtained. Based on the above mentioned formulas, we analyse the performance of orthogonal space-time block codes over multiple-input multipleoutput keyhole KG fading channels. Various performance evaluation results demonstrate the proposed mathematical analysis.     

相关MIMO信道下一种特征波束成型方案的性能研究

提出了相关多输入多输出信道下的一种空时分组码、空分复用与波束成型相结合的新方案．该方案利用了发射分集和空分复用所带来的分集和复用增益，并基于接收机反馈的信道相关矩阵设计了一种波束成型器．仿真结果表明，这种方案的性能较传统的方案在高信噪比时能获得较大的改善．     

基于DSTBC-DF的无线传感网能量有效性研究

提出了一种基于分布式空时分组编码的译码转发(DSTBC-DF)的新的协同分集方案,设计了适合协同分簇多跳无线传感网的网络协议,并讨论了协同同步情况,分析了协同分集方案的性能和协同分簇无线传感网的能量效率.理论分析与Mento Catlo仿真的结果验证了这一新方案的有效性:相比传统的方案,不但实现简单,而且通过合理的协议设计有效地解决了协同同步问题,实现了完全的分集增益,有更高的能量效率,网络系统能耗明显降低.     

Upper bounds on the error probability of coded space?time block coded systems with diversity reception

New union bounds are derived for space-time block coded systems over Rayleigh fading channels. Both maximal ratio combining and generalised selection combining are considered as combining schemes at the receiver. The union bounds are easy to be evaluated using the transfer function of the code. Furthermore, the bounds are general to any coding scheme with a known weight distribution. Results show that the proposed union bounds are tight to simulation results for wide ranges of diversity orders and signal-to-noise ratio values.     

Numeric modeling of the process of press fitting dies into ring blocks with allowance for plastic deformation and frictional forces

Dies of high-pressure vessels (HPV) for the synthesis of superhard materials (SHM) are press-fitted into ring blocks with considerable interference to improve their stability. The mathematical statement of the problem of determining the stress-strain state (SSS) of the die and ring block during press fitting, which includes a computational scheme, and a system of equations for solving elastoplastic contact problems for large deformations, is presented. The SSS of the die and ring block is investigated on the basis of an FEM-based numeric method developed with allowance for the history of the press fit in accordance with existing and proposed procedures. Implementation of the new press-fitting technology has made it possible to improve the stability of dies and ring blocks by 30–44%.Translated from Problemy Prochnosti, No. 11, pp. 94–99, November, 1990.     

Magnetic Plasmon Networks Programmed by Molecular Self‐Assembly

Nanoscale manipulation of magnetic fields has been a long‐term pursuit in plasmonics and metamaterials, as it can enable a range of appealing optical properties, such as high‐sensitivity circular dichroism, directional scattering, and low‐refractive‐index materials. Inspired by the natural magnetism of aromatic molecules, the cyclic ring cluster of plasmonic nanoparticles (NPs) has been suggested as a promising architecture with induced unnatural magnetism, especially at visible frequencies. However, it remains challenging to assemble plasmonic NPs into complex networks exhibiting strong visible magnetism. Here, a DNA‐origami‐based strategy is introduced to realize molecular self‐assembly of NPs forming complex magnetic architectures, exhibiting emergent properties including anti‐ferromagnetism, purely magnetic‐based Fano resonances, and magnetic surface plasmon polaritons. The basic building block, a gold NP (AuNP) ring consisting of six AuNP seeds, is arranged on a DNA origami frame with nanometer precision. The subsequent hierarchical assembly of the AuNP rings leads to the formation of higher‐order networks of clusters and polymeric chains. Strong emergent plasmonic properties are induced by in situ growth of silver upon the AuNP seeds. This work may facilitate the development of a tunable and scalable DNA‐based strategy for the assembly of optical magnetic circuitry, as well as plasmonic metamaterials with high fidelity.     

Assembly of sub-10-nm block copolymer patterns with mixed morphology and period using electron irradiation and solvent annealing

Block copolymer self-assembly generates patterns with periodicity in the ～10-100 nm range and is increasingly recognized as a route to lithographic patterning beyond the resolution of photolithography. Block copolymers naturally produce periodic patterns with a morphology and length-scale determined by the molecular architecture, and considerable research has been carried out to extend the range of patterns that can be produced from a given block copolymer, but the ability to control the period of the pattern over a wide range and to achieve complex structures with mixed morphologies from a given block copolymer is limited. Here we show how patterns consisting of coexisting sub-10-nm spheres and cylinders and sphere patterns with a range of periods can be created using a combination of serial solvent anneal processes and electron-beam irradiation of selected areas of a film of poly(styrene-block-dimethylsiloxane). These techniques extend the capabilities of block copolymer lithography, enabling complex aperiodic nanoscale patterns to be formed from a single block copolymer thin film.     

Optimising quasi-orthogonal STBC through group-constrained linear transformation

The generic algebraic structure of a quasi-orthogonal space-time block code (QO-STBC) has been derived, and group-constrained linear transformation (GCLT) as a mean to optimise the diversity and coding gains of a QO-STBC with square or rectangular QAM constellations has been proposed. Compared with QO-STBC with constellation rotation (CR), QO-STBC with GCLT requires only half the number of symbols for joint detection, hence lower maximum-likelihood decoding complexity. The optimum GCLT parameters for QO-STBC with square QAM constellation have been derived analytically. The optimised QO-STBCs with GCLT are able to achieve full-transmit diversity and have negligible performance loss compared with QO-STBCs with CR at the same code rate     

Calculations of neutron and photon source terms and attenuation profiles for the generic design of the SPEAR3 storage ring shield

The FLUKA Monte Carlo particle generation and transport code was used to calculate shielding requirements for the 3 GeV, 500 mA SPEAR3 storage ring at the Stanford Synchrotron Radiation Laboratory. The photon and neutron dose equivalent source term data were simulated for a 3 GeV electron beam interacting with two typical target/shielding geometries in the ring. The targets simulated are a rectangular block of 0.7 cm thick copper and a 5 cm thick iron block, both tilted at 1 degree relative to the beam direction. Attenuation profiles for neutrons and photons in concrete and lead as a function of angle at different shield thicknesses were calculated. The first, second and equilibrium attenuation lengths of photons and neutrons in the shield materials are derived from the attenuation profiles. The source term data and the attenuation lengths were then used to evaluate the shielding requirements for the ratchet walls of all front-ends of the SPEAR3 storage ring.     

Diagnostics of Flows of Pulsed Plasma by Probe, Microwave, and Photometric Methods

The methodology is suggested of complex diagnostics of pulsed plasma flows, which is based on a synchronous application of the probe, microwave, and photometric methods. The space-time distribution of the basic kinetic parameters are given under conditions of expansion of plasma clusters in vacuum and their interaction with an obstacle.     

单片机和CPLD在火箭橇全程时空位置测试中的控制方法研究

本文围绕火箭橇试验全程时空位置测试问题,研究单片机和CPLD在时序发生、时序控制、数据锁存、数据采集、数据存储等方面的联合应用,是解决火箭橇试验全程时空位置测试问题的一种方法的探索,提出了基于单片机和CPLD控制的火箭橇全程时空位置测试的设计方案,包括硬件和软件设计、时序仿真、系统精度检测等.     

Space-Time Adaptive Fup Multi-Resolution Approach for Boundary-Initial Value Problems

The space-time Adaptive Fup Collocation Method (AFCM) for solving boundary-initial value problems is presented. To solve the one-dimensional initial boundary value problem, we convert the problem into a two-dimensional boundary value problem. This quasi-boundary value problem is then solved simultaneously in the space-time domain with a collocation technique and by using atomic Fup basis functions. The proposed method is a generally meshless methodology because it requires only the addition of collocation points and basis functions over the domain, instead of the classical domain discretization and numerical integration. The grid is adapted progressively by setting the threshold as a direct measure of the solution accuracy at a given resolution level. At higher resolution levels, collocation points are only added in the space-time sub-domains where the solution correction is greater than the prescribed threshold. In contrast to the classical time-stepping schemes, in which globally accumulated errors can arise and which are not easily adapted to multiple time steps, the space-time AFCM covers all space and time multiple scales, while global error is strictly controlled in time by an a priori threshold.     

利用机体表面振动信号诊断活塞环失效的研究

建立了活塞环失效时活塞－缸套撞击的力学模型，通过理论计算证明活塞环失效后活塞组的撞击参数将会改变。分析了活塞环振动和悬浮的条件。给出了活塞环径向振动固有频率范围的计算式。通过两种机型对活塞环失效故障诊断进行了模拟试验。得到了利用机体表面振动信号诊断活塞环失效的方法；当从机身外表面监测到的振动参数在低频段出现了与单环径向振动固有频率相近的特征频率，该特征频率处谱值显著增大，含该特征频率的窄带内功率也显著增大，可认为有活塞环（通常是第一道环）失效了。