Symbol Vector Research Articles

基于SVG的WebGIS点符号库的设计与实现

通过分析目前矢量符号库的优缺点，对SVG矢量点符号库的符号制作，上传与存储，检索、抽稀与显示到地图进行了详细讨论，并结合WebGIS平台软件ECNUGIS的制图应用，为Web端矢量符号库的设计与实现提供了新的思路和方法。 Through analyzing the advantages and disadvantages of the current vector symbol database, the symbol production, upload and storage, retrieval, extraction and display of SVG vector point symbol database are discussed in detail. The new idea and method are given in the design and imple-mentation of vector symbol database for Web, which has been used in mapping application of WebGIS platform—ECNUGIS with good practical effects.

Lossless chaos‐based crypto‐compression scheme for image protection

In this study, the authors proposed a new scheme which performs both lossless compression and encryption of images. Lossless compression is done by arithmetic coding (AC) while encryption is based on a chaos-based pseudorandom bit generator. Hence, they proposed to incorporate recent results of chaos theory into AC in order to shuffle the cumulative frequency vector of input symbols chaotically to make AC secure and the decoding process completely key-dependent. Many other techniques based on varying the statistical model used by AC have been proposed in literature, however, these techniques suffer from losses in compression efficiency that result from changes in entropy model statistics and are weak against known attacks. The proposed compression–encryption techniques were developed and discussed. The numerical simulation analysis indicates that the proposed scheme is highly satisfactory for image encryption without any AC compression efficiency loss. In addition, it can be incorporated into any image compression standard or algorithm employing AC as entropy coding stage, including static, adaptive and context-based adaptive models, and at any level, including bit, pixel and predictive error pixel levels.

Efficient list‐sphere detection scheme for joint iterative multiple‐input multiple‐output detection

List-sphere detection (LSD) is a sub-optimal multiple-input multiple-output (MIMO) detection scheme which searches candidate symbol vectors that lie within a sphere of a given radius. This study presents an efficient LSD based method for a joint iterative MIMO detection scheme. The proposed method utilises a channel condition in order to define the list size. During the search process, the radius is adaptively updated to reduce the computational complexity. Owing to the list size and corresponding radius are adaptively determined by the channel condition, the authors can operate the detector at the most appropriate complexity to produce the required performance. Simulation results show that the proposed methods provide substantial complexity reduction without bit error rate performance degradation.

Correction of Two (or Often More) Vector Symbol Errors With the Outer Structure of a Hamming Single Error Correcting Code

The case of a concatenated code is considered where the inner code decoder reports multi-bit symbol decisions and can save the soft information used for the decision. Normally, an outer decoder using a Hamming single error correcting code cannot correct more than one error. But by using what is called soft information single error correction (SISEC) where a hypothesis that a particular symbol in some outer check set is the only error in the set can be confirmed or denied by the inner coder, a Hamming single error correcting code of any order can very easily correct, with high confidence, any pattern of two errors. In many cases > 2 errors can be corrected, up to a good fraction of even n-k errors of a (n,k) Hamming single error correcting code.

Binary Symbol Recovery Via <formula formulatype="inline"> <tex Notation="TeX">$\ell_{\infty}$</tex></formula> Minimization in Faster-Than-Nyquist Signaling Systems

The issue of binary symbol detection in faster-than-Nyquist signaling systems (also known as overcomplete frame-modulated digital transmission systems) is addressed in this paper. Through convex relaxation, the original combinatorial optimization problem is transformed to an l∞ minimization problem. Following this idea, we further propose lp approximation algorithms to efficiently tackle such a convex optimization problem. For noiseless case, the recoverability of l∞ minimization is analyzed. It is shown that the binary symbol vector b can be completely recovered via l∞ minimization if and only if there is a vector in the row space of the transmission matrix located in the same quadrant as - b. Otherwise, complete reconstruction via l∞ minimization is hopeless. At the same time, we give an upper bound to the reconstruction probability. For noisy case, the reconstruction probability is analyzed via the probability distribution function of indefinite quadratic form in Gaussian vectors. Numerical results are provided to study the detection performance of l∞ minimization. It is shown that, compared with semidefinite programming algorithm and linear minimum mean-squared error (LMMSE) method, the proposed l∞ minimization detection achieves a better performance-complexity trade-off.

Combined calculi for photon orbital and spin angular momenta

Context. Wavelength, photon spin angular momentum (PSAM), and photon orbital angular momentum (POAM), completely describe the state of a photon or an electric field (an ensemble of photons). Wavelength relates directly to energy and linear momentum, the corresponding kinetic quantities. PSAMand POAM, themselves kinetic quantities, are colloquially known as polarization and optical vortices, respectively. Astrophysical sources emit photons that carry this information. Aims. PSAM characteristics of an electric field (intensity) are compactly described by the Jones (Stokes/Mueller) calculus. Similarly, I created calculi to represent POAM characteristics of electric fields and intensities in an astrophysical context. Adding wavelength dependence to all of these calculi is trivial. The next logical steps are to 1) form photon total angular momentum (PTAM = POAM + PSAM) calculi; 2) prove their validity using operators and expectation values; and 3) show that instrumental PSAM can affect measured POAM values for certain types electric fields. Methods. I derive the PTAM calculi of electric fields and intensities by combining the POAM and PSAM calculi. I show how these quantities propagate from celestial sphere to image plane. I also form the PTAMoperator (the sum of the POAMand PSAMoperators), with and without instrumental PSAM, and calculate the corresponding expectation values. Results. Apart from the vector, matrix, dot product, and direct product symbols, the PTAM and POAM calculi appear superficially identical. I provide tables with all possible forms of PTAM calculi. I prove that PTAM expectation values are correct for instruments with and without instrumental PSAM. I also show that POAM measurements of "unfactored" PTAM electric fields passing through non-zero instrumental circular PSAM can be biased. Conclusions. The combined PTAM calculi provide insight into how to mathematically model PTAM sources and calibrate POAMand PSAM- induced POAM measurement errors.

Performance Analysis of Layer Pruning on Sphere Decoding in MIMO Systems

Sphere decoding (SD) for multiple-input and multiple-output systems is a well-recognized approach for achieving near-maximum likelihood performance with reduced complexity. SD is a tree search process, whereby a large number of nodes can be searched in an effort to find an estimation of a transmitted symbol vector. In this paper, a simple and generalized approach called layer pruning is proposed to achieve complexity reduction in SD. Pruning a layer from a search process reduces the total number of nodes in a sphere search. The symbols corresponding to the pruned layer are obtained by adopting a QRM-MLD receiver. Simulation results show that the proposed method reduces the number of nodes to be searched for decoding the transmitted symbols by maintaining negligible performance loss. The proposed technique reduces the complexity by 35% to 42% in the low and medium signal-to-noise ratio regime. To demonstrate the potential of our method, we compare the results with another well-known method — namely, probabilistic tree pruning SD.

Analysis of MIMO Receiver Using Generalized Least Squares Method in Colored Environments

The classical detection techniques for multiple-input multiple-output (MIMO) systems are usually designed with the assumption that the additive complex Gaussian noise is uncorrelated. However, for closely spaced antennas, the additive noise is correlated due to the mutual antenna coupling. This letter analyzes an improved zero-forcing (ZF) technique for MIMO channels in colored environments. The additive noise is assumed to be correlated and the Rayleigh MIMO channel is considered doubly correlated. The improved ZF detector, based on the generalized least squares estimator (GLS), takes into account the noise covariance matrix and provides an unbiased estimator of the transmitted symbol vectors. We introduce some novel bounds on the achievable sum rate, on the normalized mean square error at the receiver output, and on the outage probability. The derived expressions are compared to Monte Carlo simulations.

On Bidirectional Transitions between Localist and Distributed Representations: The Case of Common Substrings Search Using Vector Symbolic Architecture

The contribution of this article is twofold. First, it presents an encoding approach for seamless bidirectional transitions between localist and distributed representation domains. Second, the approach is demonstrated on the example of using Vector Symbolic Architecture for solving a problem of finding common substrings. The proposed algorithm uses elementary operations on long binary vectors. For the case of two patterns with respective lengths L1 and L2 it requires Θ(L1 + L2 – 1) operations on binary vectors, which is equal to the suffix trees approach – the fastest algorithm for this problem. The simulation results show that in order to be robustly detected by the proposed approach the length of a common substring should be more than 4% of the longest pattern.

Landscape Preference and Map Readability in Design Evaluation of Topographic Maps with an Orthoimage Background

Orthoimagery and shaded relief are ways of introducing realism to maps, but each method presents design challenges in achieving consistently readable combinations with overlaid vector symbols and labels. Two studies were conducted to compare the readability of the current United States Geological Survey (USGS) ‘US Topo’ map series with two original designs incorporating orthoimagery and shaded relief. The studies examined reader design ratings after completing tasks that required analytical use of maps with varied map designs, using maps of diverse locations in the USA. The studies indicated that readability varied with map location to a greater degree than with map design, though design influence on ratings was detected in interaction with location. This variation with landscape is discussed from the perspective of recent theory in landscape aesthetics and preferences. Also, it was statistically demonstrated that either of the two new designs had improved readability over the existing US Topo. These studies reveal that user evaluations of maps are dependent on landscape preferences as well as on design, and demonstrate the importance of national topographic map design evaluation across a wide sample of national landscapes.

Compressed sensing techniques for receiver based post-compensation of transmitter's nonlinear distortions in OFDM systems

In this paper, compressed sensing techniques are proposed to linearize commercial power amplifiers driven by orthogonal frequency division multiplexing signals. The nonlinear distortion is considered as a sparse phenomenon in the time-domain, and three compressed sensing based algorithms are presented to estimate and compensate for these distortions at the receiver using a few and, at times, even no frequency-domain free carriers (i.e. pilot carriers). The first technique is a conventional compressed sensing approach, while the second incorporates a priori information about the distortions to enhance the estimation. Finally, the third technique involves an iterative data-aided algorithm that does not require any pilot carriers and hence allows the system to work at maximum bandwidth efficiency. The performances of all the proposed techniques are evaluated on a commercial power amplifier and compared. The error vector magnitude and symbol error rate results show the ability of compressed sensing to compensate for the amplifier's nonlinear distortions.

The Design of Activity Record in C Language Compile Process

Activity record is an important part of the compile process. C-based storage management strategy, the system uses the Eclipse integrated environment in Windows 7 system , using the Java language to implement process activity record analysis and processing of the C language. Program can handle variables stored procedure calls and nested execution jumps, and through vector symbol table to achieve compact build management. By applying stack storage management strategies,the storage activity can be clearly demonstrated.

Low-overhead Secure Network Coding based on Chaotic Sequence

A minimum overhead secure network coding based on chaotic sequence is presented in this paper. And only the source need to be modified, intermediate nodes implement a classical distributed ne twork code. So the proposed scheme is applied to all the linear network coding. Combine the chaotic sequence with original source information vector, because of the high randomness and the sensitivity to initial state of chaotic sequence, the presented network code is One-Time Pad (OTP). So the secure network coding achieves complete secrecy. This scheme requires only one noisy symbol to be embedded in the original information symbol vector to achieve complete secrecy. The theoretical analysis confirm that this sch eme can achieve the information-theoretic security condition and the signalling overhead to obtain complete security is minimized, while the atta cker has limited wiretapping ability.

Optimal Two-Dimensional Lattices for Precoding of Linear Channels

Consider the communication system model y = HFx + n, where H and F are the channel and precoder matrices, x is a vector of data symbols drawn from some lattice-type constellation, such as M-QAM, n is an additive white Gaussian noise vector and y is the received vector. It is assumed that both the transmitter and the receiver have perfect knowledge of the channel matrix H and that the transmitted signal Fx is subject to an average energy constraint. The columns of the matrix HF can be viewed as the basis vectors that span a lattice, and we are interested in the precoder F that maximizes the minimum distance of this lattice. This particular problem remains open within the theory of lattices and the communication theory. This paper provides the complete solution for any nonsingular M × 2 channel matrix H. For real-valued matrices and vectors, the solution is that HF spans the hexagonal lattice. For complex-valued matrices and vectors, the solution is that HF, when viewed in four-dimensional real-valued space, spans the Schlafli lattice D4.

A KML-BASED APPROACH FOR DISTRIBUTED COLLABORATIVE INTERPRETATION OF REMOTE SENSING IMAGES IN THE GEO-BROWSER

Abstract. Existing implementations of collaborative image interpretation have many limitations for very large satellite imageries, such as inefficient browsing, slow transmission, etc. This article presents a KML-based approach to support distributed, real-time, synchronous collaborative interpretation for remote sensing images in the geo-browser. As an OGC standard, KML (Keyhole Markup Language) has the advantage of organizing various types of geospatial data (including image, annotation, geometry, etc.) in the geo-browser. Existing KML elements can be used to describe simple interpretation results indicated by vector symbols. To enlarge its application, this article expands KML elements to describe some complex image processing operations, including band combination, grey transformation, geometric correction, etc. Improved KML is employed to describe and share interpretation operations and results among interpreters. Further, this article develops some collaboration related services that are collaboration launch service, perceiving service and communication service. The launch service creates a collaborative interpretation task and provides a unified interface for all participants. The perceiving service supports interpreters to share collaboration awareness. Communication service provides interpreters with written words communication. Finally, the GeoGlobe geo-browser (an extensible and flexible geospatial platform developed in LIESMARS) is selected to perform experiments of collaborative image interpretation. The geo-browser, which manage and visualize massive geospatial information, can provide distributed users with quick browsing and transmission. Meanwhile in the geo-browser, GIS data (for example DEM, DTM, thematic map and etc.) can be integrated to assist in improving accuracy of interpretation. Results show that the proposed method is available to support distributed collaborative interpretation of remote sensing image

An Improved Full Rate Full Diversity QOSTBC with Linear Decoding in MIMO Systems

In this letter, we propose an improved Quasi-orthogonal space-time block code (QOSTBC) with full rate, full diversity, linear decoding and better peak-to-average power ratio (PAPR). Constellation rotation is used to the input symbol vector to ensure full diversity, and then the information symbol vector is interleaved in coordinates and pre-grouped by using a Given rotation matrix. The performance is evaluated by numerical experiments. The PAPR of our proposed QOSTBC is lower than that of CI-QOSTBC in Khan and Rajan (IEEE Trans Inf Theory 52(5):2062---2091, 2006). Meanwhile, the Bit-error-rate versus Signal-to-noise-ratio of our proposed QOSTBC is better than those of OSTBC (Tarokh et al. in IEEE Trans Inf Theory 45(5):1456---1467, 1999) QOSTBC (Jafarkhani in IEEE Trans Wirel Commun 49(1):1---4, 2001), G-QOSTBC (Park et al. in IEEE Commun Lett 12(12):868---870, 2008), slightly better that of the CI-QOSTBC, and as same as that of the recently proposed Minimum Decoding Complexity QOSTBCs (MDC-QOSTBC) in Yuen et al.(IEEE Trans Wirel Commun 4(5):2089---2098, 2005), Wang and Xia (IEEE Trans Inf Theory 55(3):1104---1130, 2009). Compared with MDC-QOSTBC, the proposed QOSTBC has simpler code construct and lower decoding complexity.

Randomized Decode-and-Forward Strategies for Two-Way Relay Networks

Randomized space-time block coding (RSTBC) is a decentralized cooperative technique that ensures diversity gains through the recruitment of multiple uncoordinated relays, with virtually no signaling overhead. In this paper, RSTBC is applied to two-way relaying wireless networks which, when two terminals want to send a message to each other, can potentially improve the network throughput by allowing them to exchange data over two or three time slots via bidirectional relay communications. Specifically, two decode-and-forward relaying strategies are considered which take up only two time slots. In the first slot the two sources transmit simultaneously. In the former scheme which we refer to as decode and forward both (DFB) RSTBC, only relays which can reliably decode both source blocks via joint maximum likelihood decoding cooperate, and do so by modulating the bit-level XOR of the decoded data through a single RSTBC. In the latter scheme called decode and forward any (DFA) RSTBC, the relays cooperate in the second slot also when they can decode only one of the two source data. In this case each source data that is decoded is mapped into an independent RSTBC. If the relay decoded reliably both sources, after cancellation of the strong interference, then it sends the two RSTBCs encoding the symbol vectors from each of the sources. A randomized forwarding scheme is also proposed for three-time-slot relaying, which is also a DFA strategy, although without joint decoding or interference cancellation after the first slot. The diversity orders achievable through the three proposed schemes are calculated and the obtained theoretical results are validated by means of Monte Carlo numerical simulations.

2조 UTP를 이용한 500BASE-T의 구현

UBcN에서는 한 가입자가 UDTV나 3DTV와 같은 광대역 신호를 동시에 다수의 채널로 수신할 수 있게 하기 위하여 100 Mbps를 초과하는 전송률을 요구하고 있다. 최근에 FTTH를 위한 매체로서 댁내 일부에 광케이블을 사용하기 시작했지만, UTP는 여전히 가장 많이 사용되는 매체이고 UBcN 시대에도 널리 사용될 것이다. UBcN을 위해 광케이블이 포설되지 않은 곳에 UTP를 적용해야 한다면 현재로서는 1000BASE-T나 Vectorized VDSL2를 고려할 수 있다. 그러나 대부분의 가입자 댁내에는 2조 이하의 UTP가 포설되어 있으므로 4조의 UTP를 사용해야 하는 1000BASE-T나 3조의 UTP를 사용하는 Vectorized VDSL2를 적용하기 위해서는 추가적으로 UTP를 증설해야 한다. 이러한 문제를 해결하기 위하여 본 논문에서는 2조 UTP를 통하여 500 Mbps를 제공하는 500BASE-T 기술을 제안한다. 이 기술의 특징은 현존하는 1000BASE-T의 규격에서 PCS 상부에 속도 정합을 위한 부계층과 PCS 하부에 SERDES 부계층을 추가하여 구현된다. 속도 정합계층은 기존의 GMII와 호환이 되도록 하기 위한 것이다. 그리고 SERDES 부계층을 약간 수정하면 500 Mbps의 2조의 UTP를 250 Mbps의 1조 UTP로 용이하게 변경하여 사용할 수 있다. 이러한 기능들을 FPGA와 아날로그 보드를 이용하여 구현하였으며, 실험을 통하여 속도정합, 심벌벡터 동기, 전송률 등을 검증한다. 특히, 속도정함 부계층에서 enable 제어를 통하여 링크 효율을 증가함을 보여준다. More than 100 Mbps rate is needed in the UBcN for a subscriber to receive broadband traffics with multi-channel like UDTV or 3DTV. Although the optical fiber is recently deployed for the FTTH, the UTP is the most widely used medium and will be used in UBcN age. Network providers may consider the 1000BASE-T or the vectorized VDSL if they adopts the UTP in the place where does not have optical fibers. But UTP should be expanded because 1000BASE-T and vectorized UTP needs 4 and 3 pairs cable, respectively while residential region has not exceeding 2 pair UTP cable. To solve the problem, we propose a 500BASE-T technology using 2 pairs UTP in this paper. The technology introduces a rate adaptation sublayer and a SERDES sublayer above and under the PCS, respectively. The rate adaptation sublayer is compatible for the GMII. Also, if we modify the SERDES sublayer, the technology can easily obtain 250BASE-T with 2 pairs UTP. We implement such functions with FPGA and analog board and verify the function of rate adaptation and symbol vector synchronization, and effective transmission rate by experiments. In particular, we show that link efficiency is increased by enable control in the rate adaptation sublayer.

Joint detection and estimation for cooperative communications in cluster‐based networks

ABSTRACTA joint data detection and channel estimation scheme is proposed for cooperative communications in cluster‐based networks. In the proposed approach, each relay detects the source information using its joint detection and estimation rules and then compresses this information and forwards it to the destination node. The source information received from all the relays in the network is combined at the destination node in accordance with a fusion decision rule in order to determine the corresponding symbol vector. The joint detection and estimation rule at the relays and the fusion rule at the destination node are both processed using an expectation maximization algorithm. In order to reliably avoid poor local maxima, we utilized one pilot symbol per signal block to obtain a better initial starting point for the expectation maximization algorithm. The simulation results show that the feedback mechanism accelerates the convergence of the local channel estimates toward the Cramer–Rao lower bound. Copyright © 2011 John Wiley & Sons, Ltd.

An Efficient Soft-Output MIMO Detection Method Based on a Multiple-Channel-Ordering Technique

In this paper, we propose an efficient soft-output signal detection method for spatially multiplexed multiple-input multiple-output (MIMO) systems. The proposed method is based on the ordered successive interference cancellation (OSIC) algorithm, but it significantly improves the performance of the original OSIC algorithm by solving the error propagation problem. The proposed method combines this enhanced OSIC algorithm with a multiple-channel-ordering technique in a very efficient way. As a result, the log likelihood ratio values can be computed by using a very small set of candidate symbol vectors. The proposed method has been synthesized with a 0.13-μm CMOS technology for a 4×4 16-QAM MIMO system. The simulation and implementation results show that the proposed detector provides a very good solution in terms of performance and hardware complexity.