Complex Symbols Research Articles

Learning Aided Behavioral Modeling and Adaptive Digital Predistortion Design for Nonlinear Power Amplifier

A new learning-based structure is defined for the identification of nonlinear attributes of a baseband power amplifier (PA) and design of an adaptive digital pre-distorter for application in wireless channels. Analytically and experimentally, generalized memory polynomial (GMP) model is derived from the transmit–receive conditions and the learning network structure. The test data are a sequences of 16-quadrature amplitude modulation (QAM) and 64-QAM complex symbols. In simulation, unknown GMP models of different order are used as a baseband PA model for identification. Minicircuits ZHL-4240 radio frequency PA modules along with NI USRP 2920 units are employed for experimental verification of the concept. The learning aspect is governed by a specially designed artificial neural network structure called real valued focused time delay neural network. Simulation and empirical results agree with analytical derivation.

An Energy Efficient QAM Modulation with Multidimensional Signal Constellation

Abstract Packing constellations points in higher dimensions, the concept of multidimensional modulation exploits the idea drawn from geometry for searching dense sphere packings in a given dimension, utilising it to minimise the average energy of the underlying constellations. The following work analyses the impact of spherical shaping of the constellations bound instead of the traditional, hyper-cubical bound. Balanced constellation schemes are obtained with the N-dimensional simplex merging algorithm. The performance of constellations of dimensions 2, 4 and 6 is compared to the performance of QAM modulations of equivalent throughputs in the sense of bits transmitted per complex (two-dimensional) symbols. The considered constellations give an approximately 0:7 dB to 1 dB gain in terms of BER over a standard QAM modulation.

Involuntary symbol manipulation (Pig Latin) from external control: Implications for thought suppression

In ironic processing, one is more likely to think about something (e.g., white bears) when instructed to not think about that thing. Entry into consciousness of such content may be automatic, reflecting the ‘encapsulated’ nature of the generation of conscious contents. Based on this research, the Reflexive Imagery Task (RIT) reveals that, following the activation of action sets, conscious contents can arise involuntarily and systematically in response to external stimuli. In the most basic version of this paradigm, participants are presented with visual objects and instructed to not think of the names of the objects, which is challenging. Here, we addressed one criticism of the RIT—that the effect arises only for automatic processes (e.g., forms of cued-memory retrieval) and not for more complex processes (e.g., symbol manipulation). Participants were first trained to perform a word-manipulation task similar to the game of Pig Latin (e.g., “CAR” becomes “AR-CAY”). Such a task involves complex symbol manipulations that are associated with processes in frontal cortex. After training, participants were instructed to not transform stimulus words in this way. The RIT effect still arose under these conditions. This striking finding is relevant to theories of cognitive control, psychopathology, and conscious/unconscious processing.

Performance comparison of linearly-decodable RAR-QOSTBC & conventional QO-STBC for M-PSK modulation

Quasi-Orthogonal Space time block codes (QOSTBC) containing complex symbol terms in their code structure are widely famous for achieving full rate but they are having the disadvantages of less diversity gain and more decoding complexity. In conventional QOSTBC, decoding occurs with pairs of symbols instead of individual symbol. Due to the presence of interference from the neighboring symbols decoding complexity increases. In mathematical terms, the reason for more decoding complexity is because of the presence of non-diagonal terms in the detection matrix. In this work, a new method is proposed to create a non-diagonal detection matrix and further orthogonal channel matrix & Quasi-orthogonal symbol transmission matrix are generated. Proposed scheme have been designed to overcome the disadvantages of conventional QOSTBC and that can achieve improved diversity gain and less computational load while decoding. Evaluation has been done for different orders of PSK scheme over different channels. Experimental results show that the proposed scheme is responsible for an improvement in the performance of the system in terms of BER.

Electromechanical resonance vibration generators: Operation process analysis

We consider the electromechanical resonance vibration generators (ERVG) used to implement wave technologies. These generators are the vibration systems with elastic and electromagnetic couplings with a high degree of interference in the electromagnetic and the mechanical processes. To develop engineering methods of calculation and analysis of the steady ERVG vibration regimes in the linear approximation, with account for their specific peculiarities, we propose the widely applied complex (symbol) method and superposed vector diagrams. Experimental oscillograms illustrate the results obtained.

A high throughput architecture for a low complexity soft-output demapping algorithm

Abstract. Iterative channel decoders such as Turbo-Code and LDPC decoders show exceptional performance and therefore they are a part of many wireless communication receivers nowadays. These decoders require a soft input, i.e., the logarithmic likelihood ratio (LLR) of the received bits with a typical quantization of 4 to 6 bits. For computing the LLR values from a received complex symbol, a soft demapper is employed in the receiver. The implementation cost of traditional soft-output demapping methods is relatively large in high order modulation systems, and therefore low complexity demapping algorithms are indispensable in low power receivers. In the presence of multiple wireless communication standards where each standard defines multiple modulation schemes, there is a need to have an efficient demapper architecture covering all the flexibility requirements of these standards. Another challenge associated with hardware implementation of the demapper is to achieve a very high throughput in double iterative systems, for instance, MIMO and Code-Aided Synchronization. In this paper, we present a comprehensive communication and hardware performance evaluation of low complexity soft-output demapping algorithms to select the best algorithm for implementation. The main goal of this work is to design a high throughput, flexible, and area efficient architecture. We describe architectures to execute the investigated algorithms. We implement these architectures on a FPGA device to evaluate their hardware performance. The work has resulted in a hardware architecture based on the figured out best low complexity algorithm delivering a high throughput of 166 Msymbols/second for Gray mapped 16-QAM modulation on Virtex-5. This efficient architecture occupies only 127 slice registers, 248 slice LUTs and 2 DSP48Es.

Accommodation response to Chinese and Latin characters in Chinese‐illiterate young adults

BackgroundDifferences in accommodation when reading Chinese, as compared to Latin, characters have been suggested to have a role in the higher prevalence of myopia in some Asian countries. Yeo and colleagues (Optom Vis Sci 2013; 90: 156‐163) found that, in Chinese‐literate children, accommodation was marginally more accurate (by less than 0.05 D), when reading Chinese text. This was attributed to the additional cognitive demand associated with interpreting the more complex Chinese symbols. The present study compared responses to single Chinese and Latin characters, while controlling for cognitive demand.MethodsThe monocular accommodative response was measured in Chinese‐illiterate adults (10 emmetropes, mean spherical equivalent: ‐0.07 ± 0.42 D, age: 29.9 ± 4.2 years; 11 myopes, mean spherical equivalent: ‐4.28 ± 2.84 D, age: 31.7 ± 4.6 years) with an open‐field autorefractor. Four Chinese and three Latin characters (approximately 1.15 degrees subtense) were individually presented on a display screen one metre away from the subject, while their vergence was varied over the range zero to 5.00 D using spectacle trial lenses. The slope and the accommodative error index (AEI) were calculated from the accommodative stimulus/response curves (ASRC).ResultsNo statistically significant differences were found between refractive groups or among characters within the same refractive group in ARSC slopes (Latin: 0.87 ± 0.14 for myopes versus 0.81 ± 0.12 for emmetropes; Chinese: 0.84 ± 0.12 for myopes versus 0.85 ± 0.12 for emmetropes). No significant differences were found between characters in accommodative error index either (Latin, 0.78 ± 0.42 D for myopes versus 1.15 ± 0.72 D for emmetropes; Chinese, 0.74 ± 0.37 D for myopes versus 1.17 ± 0.83 D for emmetropes). However, accommodative error indices and accommodative errors were significantly higher for emmetropes.ConclusionUnder controlled cognitive demand, Chinese and Latin characters elicited similar responses in both individual refractive groups. This study fails to support the hypothesis that development of myopia in some Asian populations is associated with larger lags of accommodation when reading or viewing Chinese characters.

Avatar in the Amazon - Narratives of Cultural Conversion and Environmental Salvation between Cultural Theory and Popular Culture

In 2010 the New York Times reported that ‘[t]ribes of Amazon Find an Ally Out of “Avatar”’, James Cameron. The alliance was against the building of Belo Monte, a hydroelectricdam in the Xingu River in Brazil. Cameron made a documentary about Belo Monte, A Message from Pandora. Here he states that Avatar becomes real in the struggle against the dam. This appears to confirm U. K. Heise’s observation that the ‘Amazon rainforest has long functioned as a complex symbol of exotic natural abundance, global ecological connectedness, and environmental crisis’. This construal, however, downplays the ‘symbols’ cultural components. In this article I show that the image of an ecological ‘rainforest Indian’ and a particular kind of culture constitutes a crucial part of the Amazon as ‘a complex’ cross-disciplinary ‘symbol’. Firstly, I examine how an Amazonian topology (closeness to nature, natural cultures) is both a product of an interdisciplinary history, and a place to speak from for ethno-political activist. Next I analyze how Amazonian cultures have been turned into ‘ethnological isolates’ representing a set of grand theoretical problems in anthropology, not least concerning the nature/culture-distinction, and how environmentalism has deployed the same topology. Finally I examine how Avatar and one of its cinematic intertexts, John Boorman’s The Emerald Forest, is used as a model to understand the struggle over the Belo Monte. In a paradoxical way the symbolic power of indigenous people in ecological matters here appears to be dependent upon a non-relation, and a reestablishment of clear cut cultural boundaries, where ‘the tribal’ is also associated with the human past. Disturbingly such symbolic exportation of solutions is consonant with current exportations of the solution of ecological problems to ‘other places’.

A function-based linear map symbol building and rendering method using shader language

Maps are widely used to visualize geo-information so that map users can develop related understandings about the real world. Such a process for communicating information is largely dependent on the rendering of map elements using different symbols (points and linear and area symbols). To meet the demand of more dynamic and comprehensive visualization in map rendering, it is essential to improve the rendering efficiency. This paper focuses on these research topics, especially the difficulty in constructing and drawing linear map symbols. By employing shader language, a function-based linear symbol building and rendering method is presented in this paper. The basic idea of this function-based method is to build a map-rendering solution that employs graphic processing unit (GPU) acceleration technology to improve the rendering efficiency. A ‘function’ is used to represent the algorithm that draws certain simple or complex linear map symbols. This function reflects the structure of a linear map symbol (describing the symbol construction information) and also the rendering process of the symbolized linear map elements (handled on a per-pixel basis by the shader program). Based on the Open Geospatial Consortium (OGC), Styled Layer Descriptor (SLD) specifications, four basic line types (i.e., solid lines, dashed lines, gradient color lines, and transition lines) are implemented in the proposed method, and the implementation of line markers, line joins and line caps is also discussed. Three experiments are conducted to demonstrate improvements in map rendering. The results show that a variety of linear map symbols can be constructed in a uniform way, which suggests that the proposed method addresses the difficulty in drawing linear map symbols. With this method, the efficiency of rendering linear map elements is substantially improved compared to using the graphics device interface plus (GDI+) and anti-grain geometry (AGG) methods; it also provides an applicable approach for developing map rendering systems. Using this function-based concept, the complexity of building linear map symbols and drawing linear map elements can be decreased.

Images as representations: visual sources on education and childhood in the past

The challenge of using images for the history of education and childhood will be addressed in this article by looking at them as representations. Central is the relationship between representations and reality. The focus is on the power of paintings as representations of aspects of realities. First the meaning of representation for images as sources for the history of education and childhood – mirrors of realities, complex symbol systems or representations – is explained. A distinction is made between images of real people and images of patterns of human behaviour and the value of the phenomenon of historical sensation as a methodological instrument for insight in that relationship is dealt with. Second, a specific genre of paintings from the seventeenth century, namely portraits of dead children, will be described and analysed to make clear that their value for the history of education and childhood can be studied adequately only by using those images as representations and by interpreting them within the cultural rules and regulations of time and place. This analysis results in the conclusion that images should be considered in their function as representations of aspects of educational and childhood reality.

Шаманские атрибуты народов Сибири: истоки семантического единства и полифункциональности

The article presents a comprehensive semantic and functional analysis of central shamanic attributes — tambourine, stick, bow with arrows, and swagger stick — drawing on a wide body of ethnographic materials on the Turko-Mongol, Samoyed, and Manchu-Tungusic peoples of Siberia as well as on the Ob Ugric people and the Kets. It argues that the shamanic attributes considered in a semiotic way constitute complex symbols that organize communication between the human and the spirit worlds. The analysis allows us to track the formation of two types of sound — a percussive (two sticks hit against one another, with one of them carrying ringing or clattering objects) and a string one (the sound is produced by a bowstring) — which act as different ways and types of communication. The research reveals semantic and, possibly, genetic consistency between various ritual objects, which indicates that many elements of the tambourine’s design, its symbolism and functional characteristics genetically go back to simpler and, apparently, universal ritual tools based on sound.DOI 10.14258/izvasu(2015)3.2-25

Polar-Based OFDM and SC-FDE Links Toward Energy-Efficient Gbps Transmission Under IM-DD Optical System Constraints [Invited

Recent studies have investigated the use of orthogonal frequency division multiplexing (OFDM) and single carrier frequency-domain equalization (SC-FDE) for gigabyte per second (Gpbs) short-range optical wired and wireless access networks based on direct intensitymodulation with direct detection (IM-DD). OFDM systems have an inherent high peak-to-average power ratio (PAPR). SC-FDE systems have lower PAPR and thus outperform comparable OFDM systems in terms of bit-error performance under various practical considerations, mainly the limited dynamic range of operation at the transmitter. In RF-based OFDM and SC-FDE systems, the output signal is bipolar, complex, and cannot be transmitted in IM-DD systems. Therefore, several power efficient schemes, however spectrally inefficient, have been proposed to make positive OFDM and SC-FDE signals, e.g., asymmetrically clipped optical OFDM (ACO-OFDM) and repetition and clipping optical SCFDE (RCO-SCFDE). To increase the data rate, novel OFDM and SC-FDE signal formats, called polar OFDM (P-OFDM) and polar SC-FDE (P-SC-FDE), based on a polar representation of complex symbols, are proposed. The proposed format offers twice as much spectral efficiency as state-of-the art unipolar OFDM and SC-FDE formats. Moreover, using a power allocation approach on the time-domain positive samples, the PAPR is further reduced, and the numerical evaluation of the bit-error performance under optical source power and dynamic range constraints demonstrates superior results toward Gpbs transmission.

A method based on graphic entity for visualizing complex map symbols on the web

A method based on graphic entity for map symbol visualization in vector-based web mapping is proposed. The method is especially effective for complex geological symbols. It has three parts: graphic entity library, symbol synthesizer, and synthesis specifications. The design process is described as the application of the method to symbols representing point, line, and polygon features in web mapping. The method works with Flash, SVG, or other mapping technologies. We chose Flash to visualize geological disaster information for the Guangdong province in China. The case study demonstrates that this graphic entity-based method can meet the demands for interactive symbolization and complex symbol visualization in Internet web mapping. It produces good results, is fast, and is easy to operate. This makes it especially suitable for web-mapping applications, especially vector-based and hybrid WebGIS applications which display complex symbols.

Alphabetism and the science of reading: from the perspective of the akshara languages.

Alphabetism and the science of reading: from the perspective of the akshara languages.

On Precoding for Constant <inline-formula> <tex-math notation="TeX">$K$</tex-math></inline-formula>-User MIMO Gaussian Interference Channel With Finite Constellation Inputs

This paper considers linear precoding for the constant channel-coefficient K-user MIMO Gaussian interference channel (MIMO GIC) where each transmitter-i (Tx-i) requires the sending of d <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</sub> independent complex symbols per channel use that take values from fixed finite constellations with uniform distribution to receiver-i (Rx-i) for i=1,2,..., K. We define the maximum rate achieved by Tx-i using any linear precoder as the signal-to-noise ratio (SNR) tends to infinity when the interference channel coefficients are zero to be the constellation constrained saturation capacity (CCSC) for Tx-i. We derive a high-SNR approximation for the rate achieved by Tx-i when interference is treated as noise and this rate is given by the mutual information between Tx-i and Rx-i, denoted as I[X <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</sub> ;Y <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</sub> ]. A set of necessary and sufficient conditions on the precoders under which [IX <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</sub> ; Y <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</sub> ] tends to CCSC for Tx-i is derived. Interestingly, the precoders designed for interference alignment (IA) satisfy these necessary and sufficient conditions. Furthermore, we propose gradient-ascent-based algorithms to optimize the sum rate achieved by precoding with finite constellation inputs and treating interference as noise. A simulation study using the proposed algorithms for a three-user MIMO GIC with two antennas at each node with d <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</sub> =1 for all i and with BPSK and QPSK inputs shows more than 0.1-b/s/Hz gain in the ergodic sum rate over that yielded by precoders obtained from some known IA algorithms at moderate SNRs.

Vacillating images of Shin Saimdang: the invention of a historical heroine in colonial Korea

Shin Saimdang (1504–1551) is a nationally renowned historical figure who is generally considered an iconic traditional Korean woman; that is, “a wise mother and good wife” (hyeonmoyangcheo). Yet simultaneously, she is the most controversial woman in Korean history. In 2009, she became the first female figure to appear on a Korean banknote. Shin Saimdang is a truly complex symbol that has been (re)constructed as both a “tradition” and a figure in “the realm of memory” throughout the twentieth century in Korea. This paper examines the early phase of the discovery and interpretation of Shin Saimdang in the modern scene that began in the Enlightenment period and ended in the Japanese colonial period. In particular, the author highlights how frameworks and strategies to interpret Shin Saimdang vacillated according to nationalistic and colonial strategies. The author also explains how the concept of “good wife and wise mother” (ryousaikenbo in Japanese), which was imported from Japan, was hybridized and transformed into a complex ideal for Korean women that emphasized the “wise mother” over the “good wife.”

Fast-Decodable MIDO Codes With Large Coding Gain

In this paper, a new method is proposed to obtain full-diversity, rate-2 (rate of two complex symbols per channel use) space-time block codes (STBCs) that are full-rate for multiple input double output (MIDO) systems. Using this method, rate-2 STBCs for 4 × 2, 6 × 2, 8 × 2, and 12 × 2 systems are constructed and these STBCs are fast ML-decodable, have large coding gains, and STBC-schemes consisting of these STBCs have a non-vanishing determinant (NVD) so that they are DMT-optimal for their respective MIDO systems. It is also shown that the Srinath-Rajan code for the 4 × 2 system, which has the lowest ML-decoding complexity among known rate-2 STBCs for the 4 × 2 MIDO system with a large coding gain for 4-/16-QAM, has the same algebraic structure as the STBC constructed in this paper for the 4 × 2 system. This also settles in positive a previous conjecture that the STBC-scheme that is based on the Srinath-Rajan code has the NVD property and hence is DMT-optimal for the 4 × 2 system.

Improved Perfect Space-Time Block Codes

Perfect space-time block codes (STBCs) are based on four design criteria-full-rateness, nonvanishing determinant, cubic shaping, and uniform average transmitted energy per antenna per time slot. Cubic shaping and transmission at uniform average energy per antenna per time slot are important from the perspective of energy efficiency of STBCs. The shaping criterion demands that the generator matrix of the lattice from which each layer of the perfect STBC is carved be unitary. In this paper, it is shown that unitariness is not a necessary requirement for energy efficiency in the context of space-time coding with finite input constellations, and an alternative criterion is provided that enables one to obtain full-rate (rate of nt complex symbols per channel use for an nt transmit antenna system) STBCs with larger normalized minimum determinants than the perfect STBCs. Further, two such STBCs, one each for 4 and 6 transmit antennas, are presented and they are shown to have larger normalized minimum determinants than the comparable perfect STBCs which hitherto had the best-known normalized minimum determinants.

Subspace-Based Blind Channel Estimation by Separating Real and Imaginary Symbols for Cyclic-Prefixed Single-Carrier Systems

Blind channel estimation based on a subspace-based algorithm for single-input single-output cyclic-prefixed single-carrier systems is proposed in this brief. The proposed method is different from conventional subspace-based approaches, which exploit the original complex structure of the received data symbols. In contrast, we separate the real part and the imaginary part of the received complex symbols and then exploit these two kinds of symbols to construct the signal model. The noise subspace can then be established to estimate the channel impulse response (CIR) using a subspace algorithm when real symbols, such as binary phase shift keying or pulse amplitude modulation symbols, are applied. The real part and the imaginary part of the CIR can be estimated individually and simultaneously with only a sign ambiguity. With the aid of repetition index, the proposed method is workable even if few data blocks are available. Simulation results demonstrate that the proposed approach outperforms conventional methods in normalized mean-squared error under static channel environments.

A new geometric descriptor for symbols with affine deformations

Great attention has been devoted to the development of shape descriptors that is the key to object recognition. Previous works have great success on either relatively simple symbols or limited transformations, e.g., translation, rotation and scaling. We propose a new affine invariant, named characteristic ratio (CHAR) that includes more points for complex symbols with rich inner structures. Moreover, we build a novel shape descriptor with CHAR values calculated on collinear points that cover the convex hull of a shape. Dynamic Time Warping algorithm is employed to compare the similarity of spectrum. The performance of the proposed descriptor is validated by the experiments compared with the classical SIFT descriptor, Shape Context (SC), recently developed Cross Ratio Spectrum (CRS) and Circular Blurred Shape Model (CBSM) on three kinds of symbols, i.e., alphanumeric characters, television networks logos and traffic signs with a wide range of transformations (2016 images in total). The results indicate a high recognition rate to severe affine deformations, and a good discriminating ability to similar symbols. We also perform the experiments on the GREC database corrupted by noise with different degrees, showing the robustness of our descriptor to noise.