Space-time Architecture Research Articles

The space-time architecture variation of the shallow magmatic plumbing systems feeding the Campi Flegrei and Ischia volcanoes (Southern Italy) from halogen constraints

The space-time architecture variation of the shallow magmatic plumbing systems feeding the Campi Flegrei and Ischia volcanoes (Southern Italy) from halogen constraints

Relics of the quantum spacetime: from Synge’s world function as the fundamental probe of spacetime architecture to the emergent description of gravity

All our observations that characterise space and time are expressed in terms of non-local, bi-tensorial objects such as geodesic intervals between events and two-point (Green) functions. In this contribution, I highlight the importance of characterising spacetime geome-try in terms of such non-local objects, focusing particularly on two important bi-tensors that play a particular fundamental role – Synge’s World function and the van Vleck determinant. I will first discuss how these bi-tensors help capture information about spacetime geometry, and then describe their role in characterising quantum spacetime endowed with a lower bound, say ℓ 0, on spacetime intervals. Incorporating such a length scale in a Lorentz covariant manner necessitates a description of spacetime geometry in terms of above bi-tensors, and naturally replaces the conventional description based on the metric tensor gab (x) with a description in terms of a non-local bi-tensor qab (x, y). The non-analytic structure of qab (x, y) which renders a perturbative expansion in ℓ 0 meaningless, also generically leaves a non-trivial “relic” in the limit ℓ 0 → 0. I present some results where such a relic term is manifest; specifically, I will discuss how this: (i) suggests a description of gravitational dynamics different from the one based on Einstein-Hilbert lagrangian, (ii) implies dimensional reduction to 2 at small scales, (iii) connects with the notion of cosmological constant itself being a non-local vestige of the small scale structure of spacetime, (iv) helps address the issues of spacetime singularities. I will conclude by discussing the ramifications of these ideas for quantum gravity.

EL CRONOTOPO HISTÓRICO. LA FORMA COMO HUELLA EN EL PARQUE-CEMENTERIO DE IGUALADA

Frente a la interpretación moderna de la arquitectura como una disciplina espacial, en las últimas décadas han emergido nuevas aproximaciones que suponen su entendimiento como una práctica conjunta del espacio y el tiempo. En este contexto, el concepto de cronotopo ha sido aplicado al análisis de la arquitectura como vinculación entre el espacio y el tiempo en el lugar. El concepto de cronotopo histórico arquitectónico, derivado del anterior, no ha sido aún desarrollado en profundidad.Entre las aproximaciones a la condición espaciotemporal de la arquitectura, la obra de Enric Miralles supone una arquitectura en la que espacio y tiempo adquieren una importancia equivalente, permitiendo una conciencia de este último a través de la experiencia del espacio. Entre sus obras, el parque-cementerio de Igualada, proyectado con Carme Pinós, configura un lugar donde el espacio y el tiempo se vinculan de manera indisoluble a través de la forma, construyendo un cronotopo.Este artículo contribuye al debate contemporáneo acerca de la arquitectura como disciplina espacio­temporal desde el concepto de cronotopo histórico, tomando como caso de estudio el parque-cementerio de Igualada. Desde la interpretación de la forma como huella, se argumenta su condición como cronotopo histórico capaz de vincular el tiempo crónico del mundo y el tiempo biológico del hombre mediante la condición calendaria y funeraria del lugar. A través del análisis del discurso de las palabras de Miralles, se muestra su voluntad de configurar el lugar como un cronotopo histórico. A partir de la interpretación reflexiva de la condición de la forma como huella histórica, se enuncian rasgos característicos del concepto de cronotopo histórico.

MIMO channels: optimizing throughput and reducing outage by increasing multiplexing gain

The two main aims of deploying multiple input multiple out (MIMO) are to achieve spatial diversity (improves channel reliability) and spatial multiplexing (increase data throughput). Achieving both in a given system is impossible for now, and a trade-off has to be reached as they may be conflicting objectives. The basic concept of multiplexing: divide (multiplex) transmit a data stream several branches and transmit via several (independent) channels. In this paper, we focused mainly on achieving spatial multiplexing by modeling the channel using the diagonal Bell Labs space time scheme (D-BLAST) and the vertical Bell Labs space time architecture (V-BLAST) Matlab simulations results were a lso given to further compare the advantages of spatial multiplexing.

Receivers for VBLAST FBMC-OQAM Systems

We consider vertical Bell laboratories layered space-time architecture for offset quadrature amplitude modulation based filter bank multicarrier (FBMC) systems, and propose two different receivers. We first investigate a low-complexity QR decomposition (QRD) based conventional minimum mean square error (MMSE) successive interference cancellation (C-MMSE-SIC) receiver. The intrinsic interference in FBMC systems severely degrades the symbol error rate (SER) of the C-MMSE-SIC receiver. By exploiting the overlapping nature of neighboring symbols in an FBMC system, and the fact that the desired symbol in an FBMC system interferes with the symbols in a small neighborhood, we propose novel low-complexity intrinsic interference estimation (IIE) based sequential MMSE-SIC (IIE-SMMSE-SIC) receivers with QRD and its sorted version. We show that the IIE-SMMSE-SIC receivers, with similar complexity order as that of the C-MMSE-SIC, have lower SER.

BER Performance of Spatial Modulation Systems Under a Non-Stationary Massive MIMO Channel Model

In this paper, the bit error rate (BER) performance of spatial modulation (SM) systems is investigated both theoretically and by simulation in a non-stationary Kronecker-based massive multiple-input-multiple-output (MIMO) channel model in multi-user (MU) scenarios. Massive MIMO SM systems are considered in this paper using both a time-division multiple access (TDMA) scheme and a block diagonalization (BD) based precoding scheme, for different system settings. Their performance is compared with a vertical Bell labs layered space-time (V-BLAST) architecture based system and a conventional channel inversion system. It is observed that a higher cluster evolution factor can result in better BER performance of SM systems due to the low correlation among sub-channels. Compared with the BD-SM system, the SM system using the TDMA scheme obtains a better BER performance but with a much lower total system data rate. The BD-MU-SM system achieves the best trade-off between the data rate and the BER performance among all of the systems considered. When compared with the V-BLAST system and the channel inversion system, SM approaches offer advantages in performance for MU massive MIMO systems.

Improving Performance of Bell Labs Layered Space-Time Systems by Multiframe Space-Time Interleavers

Turbo-BLAST (T-BLAST) is a multiple-input multiple-output (MIMO) wireless communication system. It is based on three main concepts: Bell laboratories layered space-time (BLAST) architecture, random space-time interleaving, and the turbo principle. T-BLAST system has many advantages including high data rate, excellent performance, and low complexity. These advantages make T-BLAST one the most important choices for future wireless communication systems. In this article, the authors study the effect of the space-time interleaver on the performance of T-BLAST system. This interleaver is split into two separated stages, time interleaving followed by space interleaving. They show that, in a quasi-static channel, the enhancement in performance provided by the time interleavers is very small compared to the gain provided by space interleavers. They also propose a new technique to improve the system performance, called multiframe space-time interleaving (MUSTI). Simulation results show an improvement in performance up to 6 dB at BER=10-4 for a (2,2) configuration.

Computation of System Performance of MIMO Technique in Communication Channel using V-BLAST Method.

In order to improvement both system performances and data rate Multiple Input Multiple Output techniques play an important role in transmission system. A number of techniques are used to do the needful work for performance improvement in MIMO systems belongs to different block codes, apart from that BLAST architecture are used Such as Diagonal Bell laboratories layered space-time (D-BLAST), Vertical Bell Labs Space-Time Architecture (V-BLAST) method. This work defines the performance improvement using V-BLAST technique in Multiple Input Multiple Output detector. Here we discuss the concept of Multiple Input Multiple Output with BLAST architecture. Depends upon the Bit Error Rate and Frame Error Rate, the comparison is made with the existing methods.

Unified Physics and the Entanglement Nexus of Awareness

An analysis is made of the correlation between internal processes of the neurobiological system, which ostensibly generate the subjective qualia of experiential awareness, and the external environment which is comprised of objective phenomena. We describe a mechanism of vacuum-state correlation of quanta in the neurobiological system with spatially and/or temporally separated systems, resulting in a co-dependency of states. This is evaluated in the context of how strong correlation of the dipole moments (of charge and spin) of residues in biological polymers, such as deoxyribonucleic acid and microtubulin, are involved in the information processing of awareness, particularly memory, and are entangled across spatial and temporal domains (spacetime). Coherent electromagnetic emissions from both water nanostructures and associated biomolecules may modulate the electronic properties and thus behaviors of supramolecular systems, representing a significant signaling and regulatory mechanism functioning in tandem to the strong correlation of the spin and electromagnetic dipoles of polarizable structures in biological macromolecules. Strong coherence across macromolecular structures of the biological system and extension through spacetime via entanglement resolves the “binding problem” associated with the generation of conscious awareness by the brain, as it is not only the result of supposed computational activity of neuronal networks, but the integration of information from multiple reference frames across the entanglement network of spacetime. The entanglement nexus of spacetime, herein referred to as the unified spacememory network, emerges as a component of some of the recent elaborations of quantum spacetime architecture in the holographic mass solution to quantum gravity and unification. This is taken in consideration with the Susskind-Maldacena conformal field theory holographic equivalence conjecture that demonstrates the correspondence of micro-wormholes of Planck-scale dimension with quantum entanglement, resolving the information loss paradox and providing a physical and ontological explanation for nonlocality observed in quantum behavior. Together, these concepts describe an architecture of spacetime that is built from information and quantum entanglement through a micro-wormhole network. It is shown how the unified spacememory network is pivotal to engendering fundamental characteristics of awareness that are actively utilized in the macromolecular information systems of the biological organism.

Differential Space-Time Coding Dispensing With Channel Estimation Approaches the Performance of Its Coherent Counterpart in the Open-Loop Massive MIMO-OFDM Downlink

In this paper, we propose a simple yet powerful mapping scheme that converts any conventional square-matrix-based differential space-time coding (DSTC) into a nonsquare-matrix-based DSTC. This allows DSTC schemes to be used practically in open-loop large-scale multiple-input multiple-output scenarios. Our proposed scheme may be viewed as the differential counterpart of coherent spatial modulation (SM), of the generalized SM, of Bell Laboratories layered space-time architecture, and of subcarrier-index modulation. The fundamental impediment of the existing DSTC schemes is the excessive complexity imposed by the unitary constraint. Specifically, the transmission rate of conventional DSTC schemes decays as the number of transmit antennas increases. Our proposed scheme eliminates this impediment and thus achieves a significantly higher transmission rate. We introduce four novel construction methods for the nonsquare codewords, some of which include an arbitrary number of nonzero elements in each codeword column. Our analysis shows that the proposed encoding technique reduces the complexity of both the inverse Fourier transform and the detection processes. Our proposed scheme is shown to approach the performance of its coherent counterpart for low-mobility scenarios, where the number of transmit antennas is increased up to 256.

Deep video portraits

We present a novel approach that enables photo-realistic re-animation of portrait videos using only an input video. In contrast to existing approaches that are restricted to manipulations of facial expressions only, we are the first to transfer the full 3D head position, head rotation, face expression, eye gaze, and eye blinking from a source actor to a portrait video of a target actor. The core of our approach is a generative neural network with a novel space-time architecture. The network takes as input synthetic renderings of a parametric face model, based on which it predicts photo-realistic video frames for a given target actor. The realism in this rendering-to-video transfer is achieved by careful adversarial training, and as a result, we can create modified target videos that mimic the behavior of the synthetically-created input. In order to enable source-to-target video re-animation, we render a synthetic target video with the reconstructed head animation parameters from a source video, and feed it into the trained network - thus taking full control of the target. With the ability to freely recombine source and target parameters, we are able to demonstrate a large variety of video rewrite applications without explicitly modeling hair, body or background. For instance, we can reenact the full head using interactive user-controlled editing, and realize high-fidelity visual dubbing. To demonstrate the high quality of our output, we conduct an extensive series of experiments and evaluations, where for instance a user study shows that our video edits are hard to detect.

Power Loading in Peak Limited Intensity Modulation Direct Detection Mode Group Division Multiplexing

The exponential growth of network traffic within data centers and high-performance computing generates a growing volume of fiber cabling. This raises the need for spectrally efficient communication scheme, which allows easy integration of optics and electronics. In this paper, we suggest a mode group division multiplexing scheme based upon intensity-modulated silicon photonics (SiP) Mach-Zehnder modulators (MZMs) coupled to standard graded-index multi-mode fiber directly detected using multi-segment concentric photo-detector. In addition, we have theoretically derived the bit and power loading of such a system in a closed-loop multiple-input multiple-output (MIMO) formation using convex optimization with two possible types of architectures: the vertical Bell Labs layered space-time architecture (V-BLAST) with minimum mean square error and successive interference cancellation (MMSE-SIC); and singular value decomposition (SVD). Our optimization problem maximizes the system's capacity under peak amplitude, power consumption, and BER constraints. Simulation results have shown the superiority of a V-BLAST MMSE-SIC over the SVD architecture in terms of total spectral efficiency for a 4 × 4 MIMO short reach low driving voltage conventional SiP-based MZM system.

Performance Analysis of a Multi-layered SVD Based STBC System

Multiple-Input Multiple-Output transmission systems using orthogonal frequency-division multiplexing is a key solution in wireless communications. The performance of MIMO-OFDM systems can be improved using coding schemes such as Space–Time Block Coding (STBC), Singular Value Decomposition (SVD) and Vertical Bell Labs Layered Space–Time Architecture (VBLAST). In this paper we present a (4 × 4) cascaded STBC–SVD multi-layered encoder structured in a VBLAST architecture. The STBC output streams are SVD encoded to improve symbol error rate (SER) performance. The introduced system achieves both spatial multiplexing and diversity gains simultaneously and maintains reliable SER performance. We study the effect of ordering the output streams of the STBC before applying the SVD encoding. We show that there is an optimum ordering that guarantees a minimum overall SER. MATLAB® simulations show that the proposed system performs better over other conventional VBLAST systems. Moreover, we show that better performance is not associated with an increase in the computational complexity.

Slicer Architectures for Analog-to-Information Conversion in Channel Equalizers

The scaling of analog-to-digital converter (ADC) power consumption with communication bandwidth imposes severe limits on its precision, which significantly impacts receiver performance. In this paper, we consider a “space-time” generalization of the flash architecture by allowing a fixed number of slicers to be dispersed in time (i.e., sampling offset) as well as space (i.e., amplitude), with the goal of investigating its capabilities for analog-to-information conversion (i.e., enabling reliable recovery of digital information, rather than faithful reproduction of the input signal) in the context of channel equalization for binary signaling over a dispersive channel. We first study standard symbol-spaced ADC with severe quantization constraints, estimating the minimum number of slicers needed to avoid error floors. We observe that the performance is sensitive to channel realization and sampling phase, which motivates a more flexible space-time architecture. Using ideas similar to those underlying compressive sensing, we prove that such architectures have no fundamental limitations in theory: randomly dispersing enough one-bit slicers over space and time does provide information sufficient for reliable equalization. We then focus on practical designs for symbol-spaced and fractionally-spaced sampling subject to a constraint on the number of slicers, and propose an algorithm for optimizing slicer thresholds, which significantly improves performance over a standard design.

Scalable Source Transmission with Unequal Frequency Reuses in MIMO Cellular Networks

This paper studies the optimal frequency reuse for the transmission of multimedia scalable sources, such as embedded images or scalable video, which need unequal error protection or unequal transmission rates in the bitstream. First, we analyze the crossover of the outage probabilities for full and partial frequency reuse cases in terms of the data rate. We prove that we can find a crossover of the outage probability curves for a data rate lower than a given threshold, which is a function of the parameters such as the partial frequency reuse factor and the user location in the cell. Moreover, the crossover point in the signal-to-noise ratio (SNR) is a strictly increasing function of the data rate. On the other hand, for a data rate higher than or equal to the threshold, there is no crossover; for all SNRs, the outage probability of full-frequency reuse is lower than that of partial-frequency reuse. The results are proven for the arbitrary location of a user in a cell, and for an arbitrary partial frequency reuse factor. Furthermore, the results hold, regardless of the numbers of transmit and receive antennas in the multiple-input multiple-output systems of orthogonal space-time block codes, and of the vertical Bell Labs space-time architecture with a zero-forcing linear receiver. Based on the analysis, we propose unequal-frequency reuse for the optimal transmission of scalable sources. The numerical results show that the peak-SNR performance improves when a sequence of scalable packets is transmitted at the subbands governed by unequal-frequency reuse in cellular networks.

Multiple-input multiple-output underwater acoustic communications by using a quasi-orthogonal group space-time architecture

A Quasi-orthogonal Group Space-Time (QoGST) architecture is presented in this paper for better diversity and multiplexing tradeoff gains in Multiple-Input Multiple-Output (MIMO) underwater acoustic (UWA) communications. Both QoGST and Group Layered Space-Time (GLST) are the combination of space-time block coding (STBC) and layered space-time coding. For GLST, the STBC is taken just in each group. For QoGST, however, all groups are encoded together via inter-group STBC, which can effectively suppress the interference between groups with the orthogonal STBC. At the receivers, the STBC decoding is performed and thus we have the higher diversity gains for the group detection. A statistical model of UWA channel which is presented by Milica Stojanovic and contains variations caused by small- and large-scale effects is considered. Simulation results show that the frame error rate (FER) of QoGST is much lower than that of GLST, which means the QoGST has the higher diversity gains. Furthermore, the lower bound diversity and multiplexing tradeoff of QoGST is coincides with that of GLST and the upper bound diversity and multiplexing tradeoff of QoGST is closer to the optimal values.

Optimization of Multimedia Progressive Transmission Over MIMO Channels

This paper studies the optimal transmission of multimedia progressive sources, which require unequal target error rates in their bitstream, over multiple-input–multiple-output (MIMO) channels. First, we derive the information outage probability expression of a space–time code for an arbitrarily given piecewise-linear diversity–multiplexing tradeoff (DMT) function and the conditions for the existence of a crossover point of the information outage probability curves of the space–time codes. We prove that as long as the crossover point of the outage probabilities exists, as spectral efficiency increases, the crossover point in the signal-to-noise ratio (SNR) monotonically increases, whereas that of the outage probability monotonically decreases. This analysis can be applied to any space–time code, receiver, and propagation channel with a given DMT function. As a specific example, we analyze the two-layer diagonal Bell Labs space–time architecture (D-BLAST) with a group zero-forcing receiver, the vertical BLAST (V-BLAST) with a minimum mean-square error receiver, and orthogonal space–time block codes (OSTBCs), and prove the monotonic behavior of the crossover point for those codes. Based on that, with respect to D-BLAST, V-BLAST, and OSTBC, we derive a method for the optimal space–time coding of a sequence that contains numerous progressive packets. We show that by employing the optimization method rather than exhaustive search, the computational complexity involved with optimal space–time coding can be exponentially reduced without losing any peak SNR performance.

Combined Data Detection Scheme for Zero-Padded OFDM Signals in MMF Links

In this letter, we propose a receiver scheme for zero-padded orthogonal frequency division multiplexing (OFDM) that combines low complexity from overlap-and-add equalizer and low error rate provided by successive interference cancellation data detection from optimal ordering vertical Bell Laboratories layered space-time (V-BLAST) architecture. Results of numerical simulations on multimode optical fiber links show that the proposed scheme improves the error rate performance of zero forcing (ZF) equalization receiver, reaching results similar to V-BLAST. For example, the proposed scheme can reach 33.9 Gb/s in a 600-m link, whereas the ZF receiver would reach 29.06 Gb/s and cyclic prefix OFDM only 19.37 Gb/s. These results are obtained with a reduction in computational complexity (measured in number of real products) of 86% in detection and 66% in preprocessing with respect to the ZF receiver, and 75% and 97% with respect to the V-BLAST receiver.

Opportunistic round robin scheduling for V-BLAST systems over multiuser MIMO channels

In this paper, we study opportunistic round robin (ORR) uplink scheduling for vertical Bell Labs layered space-time architecture (V-BLAST) systems over multiuser multiple-input multiple-output (MIMO) channels. The proposed ORR scheduling method is compared to greedy scheduling. In greedy scheduling, the base station selects the best user based on a certain criterion without any consideration for fairness. On the other hand, ORR scheduling guarantees full fairness and each user will be served by excluding the previous selected users from the competition in the next round. The selected user spatially multiplexes his data over the transmit antennas. This spatial multiplexing (SM) scheme provides high data rates, while multiuser diversity obtained from scheduling improves the performance of the uplink system. The results show the performance and capacity gains obtained by scheduling. The greedy scheduler captures full multiuser diversity. In contrast, the ORR scheduler provides substantial signal-to-noise ratio (SNR) gains compared to round robin while guaranteeing full fairness to all users.

User Selection Criteria for Uplink Spatial Multiplexing MIMO Systems

We study in this paper multiuser uplink scheduling algorithms for Multiple-Input Multiple-Output (MIMO) systems, where the multiusers compete for the MIMO Channel and the scheduler selects one user at a time based on a certain criterion. Then the selected user spatially multiplexes his data over the transmit antennas. This spatial multiplexing (SM) scheme provides high data rates while the multiuser diversity obtained from scheduling improves the performance of the uplink system. At the receiver, the Vertical-Bell-Labs LAyered Space Time architecture (V-BLAST) is used to detect the information layers. The main contribution of this paper is proposing and comparing the performance of several scheduling criteria for MIMO uplink scheduling. In addition, novel V-BLAST capacity bounds based on random matrix theory is presented. Furthermore, we investigate suboptimal schedulers and compare their performance. The main results of this study show that the scheduler that maximizes the optimal MIMO capacity doesn't work well for a V-BLAST system. Instead, the optimal scheduler that maximizes the V-BLAST capacity is derived and analyzed. In addition, we look into scheduling for SM with sphere decoding and we find that in this case, using MIMO capacity as the scheduling criterion performs the best.