We implement and experimentally demonstrate a distributed, phase-coherent, mesh relay network that executes spatiotemporal beamforming on a communications signal. Each single-antenna node of this mesh network amplifie...
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We implement and experimentally demonstrate a distributed, phase-coherent, mesh relay network that executes spatiotemporal beamforming on a communications signal. Each single-antenna node of this mesh network amplifies, predistorts, and forwards its reception to a receiver. In this configuration, an incoherent network of N nodes enhances the received power of a signal of interest by a factor of N compared to a single-input single-output communications link. By synchronizing these distributed nodes and constructing a spatiotemporal beamformer, we increase this factor to a maximum of N-2 and enable significant interference rejection capabilities. To achieve phase-coherence across the network elements, we execute a distributed synchronization algorithm using training data from the source node. We construct spatiotemporal beamformers by solving an MMSE optimization, which we continually reoptimize using new observations of training sequences and updated channel estimates. We present results from two over-the-air experimental demonstrations, one without and one with an external interferer. In the former, we demonstrate a 17.4 dB signal-to-noise ratio (SNR) improvement compared to the 18.1 dB theoretical bound for an eight-element network. In the latter, we demonstrate an 11.3 dB SNR improvement and a 14.6 dB interference reduction.
In this paper, we present a novel application of distributed coherent communications labelled holographic beamforming, in which a distributed, cooperative relay implements a distributed transmit beamforming solution t...
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ISBN:
(纸本)9798350325744
In this paper, we present a novel application of distributed coherent communications labelled holographic beamforming, in which a distributed, cooperative relay implements a distributed transmit beamforming solution to improve the throughput and resilience of communications systems in a multi-user environment. We derive an MMSE beamforming solution to the posed problem. In a MATLAB simulation platform, we characterize the performance improvement of the proposed solution in terms of sum-rate, and compare this performance against a traditional frequency-division, multiple-access strategy leveraging single-user distributed coherent beamforming. With these results, we demonstrate a substantial throughput increase under certain configurations and discuss the limitations of the proposed approach in others.
A method of reducing parameters estimation error by multi-pulse accumulation is proposed to deal with the problem of large error and low coherence performance of distributed coherent aperture radar in low SNR(signal-t...
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ISBN:
(数字)9781728160672
ISBN:
(纸本)9781728160689
A method of reducing parameters estimation error by multi-pulse accumulation is proposed to deal with the problem of large error and low coherence performance of distributed coherent aperture radar in low SNR(signal-to-noise ratio) environment. This method uses different coherent accumulation methods for low-speed and high-speed moving targets respectively. For low-speed targets without range migration, discrete Fourier transform is used to achieve multi-pulse coherent accumulation. For high-speed targets, the keystone transform is used to correct the range migration firstly, and then the coherent accumulation is realized by discrete Fourier transform. Then, the peak picking method is used to estimate the coherence parameters. Finally, the coherence parameters estimation process in low SNR environment is given in combination with two cases. The simulation results show that, compared with the method of monopulse signal, this method can obtain higher estimation performance of coherence parameters in low SNR environment. And with the increase of accumulated pulses, the estimation performance of coherence parameters also improves.
Spectral congestion and modern consumer applications motivate radio technologies that efficiently cooperate with nearby users and provide several services simultaneously. We designed and implemented a joint positionin...
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Spectral congestion and modern consumer applications motivate radio technologies that efficiently cooperate with nearby users and provide several services simultaneously. We designed and implemented a joint positioning-communications system that simultaneously enables network communications, timing synchronization, and localization to a variety of airborne and ground-based platforms. This Communications and High-Precision Positioning (CHP2) system simultaneously performs communications and precise ranging (<10 cm) with a narrow band waveform (10 MHz) at a carrier frequency of 915 MHz (US ISM) or 783 MHz (EU Licensed). The ranging capability may be extended to estimate the relative position and orientation by leveraging the spatial diversity of the multiple-input, multiple-output (MIMO) platforms. CHP2 also digitally synchronizes distributed platforms with sub-nanosecond precision without support from external systems (GNSS, GPS, etc.). This performance is enabled by leveraging precise time-of-arrival (ToA) estimation techniques, a network synchronization algorithm, and the intrinsic cooperation in the joint processing chain that executes these tasks simultaneously. In this manuscript, we describe the CHP2 system architecture, hardware implementation, and in-lab and over-the-air experimental validation.
coherence is a basic feature of quantum systems and a common necessary condition for quantum correlations. It is also an important physical resource in quantum information processing. In this paper, using relative ent...
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coherence is a basic feature of quantum systems and a common necessary condition for quantum correlations. It is also an important physical resource in quantum information processing. In this paper, using relative entropy, we consider a more general definition of the cohering power of quantum operations. First, we calculate the cohering power of unitary quantum operations and show that the amount of distributed coherence caused by non-unitary quantum operations cannot exceed the quantum-incoherent relative entropy between system of interest and its environment. We then find that the difference between the distributed coherence and the cohering power is larger than the quantum-incoherent relative entropy. As an application, we consider the distributed coherence caused by purification.
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