In this paper, we utilize a space-time coding (STC) scheme to synthesize the multiple-input multiple-output (MIMO) radar transmit beampattern and meanwhile consider the matched filtering loss (MFL) of equivalent signa...
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In this paper, we utilize a space-time coding (STC) scheme to synthesize the multiple-input multiple-output (MIMO) radar transmit beampattern and meanwhile consider the matched filtering loss (MFL) of equivalent signal in waveform design. To solve the MFL optimization problem, we propose a simulated annealing based (SA-based) algorithm to effectively find the optimal solution of STC waveform matrix. Our STC method for waveform design has suppressed the fluctuation of equivalent signal so that has the advantage of achieving the minimum MFL nearly, compared to the conventional methods for constant-envelope constraint waveform design (e.g. cyclic algorithm (CA) method). Simulation results demonstrate the effectiveness of the proposed algorithm. (C) 2019 Elsevier Inc. All rights reserved.
Aeronautical telemetry systems that transmit the same signal through multiple antennas from the flight vehicle suffer from severe link dropouts when the signals destructively interfere one with another at receiver. Th...
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Aeronautical telemetry systems that transmit the same signal through multiple antennas from the flight vehicle suffer from severe link dropouts when the signals destructively interfere one with another at receiver. The underlying issue is a transmit array with element spacing far greater than the wavelength producing a transmit antenna pattern with significant and deep nulls. Recently, space-time coding techniques have been proven to resolve the issue for systems using linear modulations and shaped-offset quadrature shift keying (SOQPSK) modulation, a non-linear continuous phase modulation (CPM). This thesis examines application of space-time coding techniques to resolve the self-interference issue for another CPM modulation, the advanced range telemetry (ARTM) CPM. It is shown in this thesis among the two branches of space-time coding, space-time block coding (STBC) and space-time trellis coding (STTC), only the latter offers a solution for a full rate, low complexity, no hardware modification implementation. Various candidate STTCs are identified via simulation using the pair-wise error probability as a performance metric. One STTC is identified with trivial implementation costs and an error performance that is a function of code length.
Metasurfaces are artificially designed ultra-thin structures that can be regarded as two-dimensional forms of metamaterials. space-time-coding metasurface has been developed. This concept has aroused the research inte...
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Digital metasurfaces based on space-time coding have established themselves as a powerful and versatile platform for joint spatial/spectral control of electromagnetic waves. However, their advanced design remains a la...
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Digital metasurfaces based on space-time coding have established themselves as a powerful and versatile platform for joint spatial/spectral control of electromagnetic waves. However, their advanced design remains a largely open problem with significant computational challenges. This study introduces a novel approach, based on deep neural networks, to address this challenge. The proposed technique enables the simultaneous and independent multi-frequency synthesis of scattering patterns, allowing precise tailoring of the harmonic equivalent currents (both in magnitude and phase), and enhancing spectral efficiency. These results, experimentally validated at X-band microwave frequencies, substantially broaden the capabilities of space-time coding digital metasurfaces, paving the way for advanced applications in wireless communications, sensing, and imaging. This study addresses the multi-frequency synthesis of space-time-coding digital metasurfaces via a machine-learning-based method that offers improved control over harmonic beam shaping/steering and increased spectral efficiency. Synthesized examples include Dolph-Chebyshev, Fourier-based, diffuse-scattering, and orbital-angular-momentum patterns. These outcomes, experimentally verified at X-band microwave frequencies, hold promise for applications to wireless communications, sensing, and imaging scenarios. image
Orbital angular momentum (OAM) multiplexing has recently received considerable interest in free space optical (FSO) communications. Propagating OAM modes through free space may be subject to atmospheric turbulence (AT...
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Orbital angular momentum (OAM) multiplexing has recently received considerable interest in free space optical (FSO) communications. Propagating OAM modes through free space may be subject to atmospheric turbulence (AT) distortions that cause intermodal crosstalk and power disparities between OAM modes. In this paper, we are interested in multiple-input-multiple-output (MIMO) coherent FSO communication systems using the OAM. We propose a selection criterion for the OAM modes to minimize the impact of the AT. To further improve the obtained performance, we propose a space-time (ST) coding scheme at the transmitter. Through numerical simulations of the error probability, we show that the penalty from AT is completely absorbed for the weak AT regime, and considerable coding gains are obtained in the strong AT regime.
Algebraic space-time codinga powerful technique developed in the context of multiple-input multiple-output (MIMO) wireless communicationshas profited tremendously from tools from Class Field Theory and, more concretel...
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Algebraic space-time codinga powerful technique developed in the context of multiple-input multiple-output (MIMO) wireless communicationshas profited tremendously from tools from Class Field Theory and, more concretely, the theory of central simple algebras and their orders. During the last decade, the study of space-time codes for practical applications, and more recently for future generation (5G+) wireless systems, has provided a practical motivation for the consideration of many interesting mathematical problems. One such problem is the explicit computation of orders of central simple algebras with small discriminants. In this article, we consider the most interesting asymmetric MIMO channel setups and, for each treated case, we provide explicit pairs of fields and a corresponding non-norm element giving rise to a cyclic division algebra whose natural order has the minimum possible discriminant.
Nonorthogonal multiple access (NOMA) can improve the spectrum efficiency through reusing the power-level space by different users. Although NOMA in single-input single-output channels has been thoroughly explored, it ...
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Nonorthogonal multiple access (NOMA) can improve the spectrum efficiency through reusing the power-level space by different users. Although NOMA in single-input single-output channels has been thoroughly explored, it is still underexploited in multiple-input multiple-output (MIMO) channels. Precoding design in multiuser MIMO channels with nonorthogonal transmission is a multidimensional nesting problem, it is hard to compare two matrix channels if only their power levels are considered. In this paper, we first propose a method to compare the covariance matrices of two channel matrices, and then derive a channel condition under which the linear precoding scheme can achieve the sum capacity. Considering arbitrary realizations of multiuser channels, we provide a nested precoding algorithm that can work well in highly correlated multiuser channels. Based on this idea, a specialized superposition transmission scheme between signaling and data information is proposed, where plenty of resources beneath the signaling signal are utilized to transmit data information for dedicated users, and a large amount of extra rates are achieved. In addition, space-time coding is used for signaling information and spatial-division multiplexing is used for multiuser data information. Under the constraint that signaling information should be correctly decoded at any position in the cell, we seek to maximize the sum rate of the underneath multiuser data streams. To this end, the optimal and a low-complexity simplified precoding algorithms are developed. Finally, simulation results verify the throughput improvement and the correct decoding probability of the signaling information.
We propose a novel space-time waveform coding (STWC) scheme for joint radar and wireless communications (RadCom). In particular, we consider a frequencymodulated continuous-wave (FMCW) multiple-input multipleoutput (M...
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ISBN:
(纸本)9781728131061
We propose a novel space-time waveform coding (STWC) scheme for joint radar and wireless communications (RadCom). In particular, we consider a frequencymodulated continuous-wave (FMCW) multiple-input multipleoutput (MIMO) radar for near-range to medium-range radar applications. In order to establish the required orthogonal transmit signals, up- and down-chirp FMCW waveforms are combined with Alamouti space-time coding across two transmit antennas. We demonstrate that, from a radar perspective, the cross-ambiguity function is improved significantly by the orthogonal Alamouti code, while the FMCW waveforms ensure robustness in the presence of Doppler shifts. Regarding the communications part, the generic orthogonality of the Alamouti code allows us to embed random information symbols within the radar signal, enabling wireless communications in the 100 kb/s regime. To this end, we propose a suitable communications receiver algorithm for multiple antennas with corresponding maximum-ratio combining, which is able to extract the embedded information symbols while acquiring spatial diversity gains.
Background: Referring to space-time coding (STC) in wireless MIMO communication and Gram-Schmidt procedure, we introduce a new procedure in the symbol combiner of the receiver that detects the transmitted symbols stra...
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Background: Referring to space-time coding (STC) in wireless MIMO communication and Gram-Schmidt procedure, we introduce a new procedure in the symbol combiner of the receiver that detects the transmitted symbols straightforwardly and more easily than the heuristic procedure presented by Alamouti. Methods: To find this combiner, we firstly project the vector of symbols in a two-dimensional orthonormal basis, Cartesian coordinate system, and make the computation in this coordinates. Conclusion: Using the presented procedure, we obtain new capabilities to realize both the new combiner and a reasonable BER in the receiver.
The principle of space-time block coding is considered. The main problems of building MIMO radar systems are described. Encoding methods for antennas with a variety of active elements are proposed. An assessment of th...
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ISBN:
(纸本)9781728103396
The principle of space-time block coding is considered. The main problems of building MIMO radar systems are described. Encoding methods for antennas with a variety of active elements are proposed. An assessment of the advantages and disadvantages of the methods described is given.
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