This article introduces Nvidia's high-performance Pascal GPU. GP100 features in-package high-bandwidth memory, support for efficient FP16 operations, unified memory, and instruction preemption, and ...incorporates Nvidia's NVLink I/O for high-bandwidth connections between GPUs and between GPUs and CPUs.
The problem of joint downlink cell association (CA) and wireless backhaul bandwidth allocation (WBBA) in two-tier cellular heterogeneous networks (HetNets) is investigated. Large-scale antenna array ...is implemented at the macro base station (BS), while the small cells within the macro cell range are single-antenna BSs and they rely on over-the-air links to the macro BS for backhauling. A sum logarithmic user rate maximization problem is studied under the wireless backhaul constraints. Duplex and spectrum sharing with co-channel reverse time-division duplex (TDD) and dynamic soft frequency reuse is considered for interference management in the two-tier HetNet employing large-scale antenna arrays at the macro BS and wireless backhauling for small cells. Two in-band WBBA scenarios, namely, unified bandwidth allocation and per-small-cell bandwidth allocation, are investigated for joint CA-WBBA in the HetNet. A two-level hierarchical decomposition method for relaxed optimization is employed to solve the mixed-integer nonlinear program (MINLP). Solutions based on the General Algorithm Modeling System (GAMS) optimization solver and fast heuristics are also proposed for cell association in the per-small-cell WBBA scenario. It is shown that when all small cells have to use in-band wireless backhaul, the system load has more impact on both the sum logarithmic rate and per-user rate performance than the number of small cells deployed within the macro cell range. The proposed joint CA-WBBA algorithms have an optimal load approximately equal to the size of the large-scale antenna array at the macro BS. The cell range expansion (CRE) strategy, which is an efficient cell association scheme for HetNets with ideal backhauling, is shown to be inefficient when in-band wireless backhauling for small cells comes into play.
This paper expands our previous work on planar tunable capacitive coupling structures in substrate-integrated cavities using lumped components. We demonstrate both frequency and bandwidth tunable ...filters with adjustable transmission zeros (TZs). By the appropriate choice of the absolute and relative strength of magnetic and electric coupling coefficients, we demonstrate: 1) tunable bandwidth and the ability to maintain either a constant absolute bandwidth or a constant fractional bandwidth; 2) adjustable TZ location at a prescribed bandwidth; and 3) the ability to switch OFF the filter with high isolation. Filter design methodologies based on a dispersive coupling structure are presented using lumped circuit models, coupling matrix, and full-wave simulations. With this planar capacitive coupling, it is also convenient to realize cross-coupling in higher order filters to produce additional TZs for rejecting spurious resonances or interferes. Fabricated two-pole filters with one or two TZs and four-pole filters with three or four TZs validate the filter design. A two-pole filter with tunable center frequency and tunable bandwidth along with a four-pole filter with tunable center frequency and tunable TZs are also demonstrated.
This paper presents the analysis and design of a novel broadband low-noise amplifier (LNA) with larger than seven-octave bandwidth. To achieve good impedance matching, flat gain, and low noise over ...larger than seven-octave bandwidth, the combination technique of shunt-resistive feedback, dual inductive-peaking techniques as well as a compact improved active load supporting broadband RF biasing from dc to 20 GHz, is proposed for LNA design. The gain and noise improvement principles of the proposed technique are also analyzed theoretically. Based on the theoretical study, a three-stage LNA with larger than seven-octave bandwidth, i.e. 0.1 to 20 GHz, is designed and verified using a 0.15-<inline-formula> <tex-math notation="LaTeX">\mu \text{m} </tex-math></inline-formula> GaAs pHEMT technology. The LNA experimental results show a high gain of 28.6 dB, good noise figure of 3.1 to 5.8 dB, and output <inline-formula> <tex-math notation="LaTeX">P_{\mathrm {-1\,\,dB}} </tex-math></inline-formula> of 7.8 to 12.7 dBm over the broad frequency range of 0.1 to 20 GHz. The proposed LNA has a compact chip size of only 1.53 mm 2 including testing input/output pads.
A hybrid metasurface (HMS) is proposed to form a low-profile wideband antenna array. The antenna element is an array of 4 × 4 square metal patches and fed by a 50 Ω microstrip line through an ...H-shaped coupling slot on the ground plane. Only are the edge patches of HMS antenna element grounded by shorting pins for the suppression of surface waves and crosspolarization levels as well as the enhancement of the gain. With the HMS antenna element, a compact 2 χ 2 array with an overall size of 1.58λ 0 × 1.58λ 0 ×0.068λ 0 (λ4 is the free-space wavelength at 5.0 GHz) is designed, where the adjacent elements share the edge patches of the elements. The measurement shows the impedance bandwidth of 28% (4.41-5.85 GHz) for |S 11 | ≤ -10 dB is obtained, and the boresight gain is greater than 8.4 dBi across the operating band, covering both fifth-generation (5G) sub 6 GHz and WiFi bands.
We study federated machine learning at the wireless network edge, where limited power wireless devices, each with its own dataset, build a joint model with the help of a remote parameter server (PS). ...We consider a bandwidth-limited fading multiple access channel (MAC) from the wireless devices to the PS, and propose various techniques to implement distributed stochastic gradient descent (DSGD) over this shared noisy wireless channel. We first propose a digital DSGD (D-DSGD) scheme, in which one device is selected opportunistically for transmission at each iteration based on the channel conditions; the scheduled device quantizes its gradient estimate to a finite number of bits imposed by the channel condition, and transmits these bits to the PS in a reliable manner. Next, motivated by the additive nature of the wireless MAC, we propose a novel analog communication scheme, referred to as the compressed analog DSGD (CA-DSGD), where the devices first sparsify their gradient estimates while accumulating error from previous iterations, and project the resultant sparse vector into a low-dimensional vector for bandwidth reduction. We also design a power allocation scheme to align the received gradient vectors at the PS in an efficient manner. Numerical results show that D-DSGD outperforms other digital approaches in the literature; however, in general the proposed CA-DSGD algorithm converges faster than the D-DSGD scheme, and reaches a higher level of accuracy. We have observed that the gap between the analog and digital schemes increases when the datasets of devices are not independent and identically distributed (i.i.d.). Furthermore, the performance of the CA-DSGD scheme is shown to be robust against imperfect channel state information (CSI) at the devices. Overall these results show clear advantages for the proposed analog over-the-air DSGD scheme, which suggests that learning and communication algorithms should be designed jointly to achieve the best end-to-end performance in machine learning applications at the wireless edge.
This paper presents a bandwidth expansion method for dual-mass microelectromechanical system (MEMS) gyroscopes based on the pole-zero temperature compensation method. When the sense loop operates ...under open conditions, the mechanical sensitivity of the gyroscope structure conflicts with the bandwidth and is governed by the frequency difference between the drive and the sense modes (min {Δ ω 1 , Δ ω 2 }), which is proven to change with temperature during the experiment. The pole-zero temperature compensation proportional controller (PZTCPC) is proposed to expand the bandwidth under different temperatures based on the pole-zero compensation method. The force rebalancing combs stimulation method (FRCSM) is used to achieve accurate gyroscope bandwidth characteristics. The mechanical bandwidth of the gyroscope is proven to be approximately 13 Hz when the sense-mode loop is open, and the simulation results show that the PZTCPC method expands the bandwidth to greater than 91.7 Hz after the sense-mode loop is closed. The FRCSM experiments indicate that gyroscope bandwidth is expanded to 95 Hz at -40 °C, 94 Hz at 20 °C and 92 Hz at 60 °C, while the bandwidths at -40, 20, and 60 °C are all 93 Hz with the turntable method. The experimental curves match the simulation curves well and verify the simulation results. The new limiting condition of the closed-loop bandwidth is the trough generated by conjugate zeros, formed by superposition of in-phase and anti-phase sense modes.
We study federated machine learning (ML) at the wireless edge, where power- and bandwidth-limited wireless devices with local datasets carry out distributed stochastic gradient descent (DSGD) with ...the help of a parameter server (PS). Standard approaches assume separate computation and communication, where local gradient estimates are compressed and transmitted to the PS over orthogonal links. Following this digital approach, we introduce D-DSGD, in which the wireless devices employ gradient quantization and error accumulation, and transmit their gradient estimates to the PS over a multiple access channel (MAC). We then introduce a novel analog scheme, called A-DSGD, which exploits the additive nature of the wireless MAC for over-the-air gradient computation, and provide convergence analysis for this approach. In A-DSGD, the devices first sparsify their gradient estimates, and then project them to a lower dimensional space imposed by the available channel bandwidth. These projections are sent directly over the MAC without employing any digital code. Numerical results show that A-DSGD converges faster than D-DSGD thanks to its more efficient use of the limited bandwidth and the natural alignment of the gradient estimates over the channel. The improvement is particularly compelling at low power and low bandwidth regimes. We also illustrate for a classification problem that, A-DSGD is more robust to bias in data distribution across devices, while D-DSGD significantly outperforms other digital schemes in the literature. We also observe that both D-DSGD and A-DSGD perform better with the number of devices, showing their ability in harnessing the computation power of edge devices.
Faster-Than-Nyquist Signaling Anderson, John B.; Rusek, Fredrik; Owall, Viktor
Proceedings of the IEEE,
08/2013, Volume:
101, Issue:
8
Journal Article
Peer reviewed
In this paper, we survey faster-than-Nyquist (FTN) signaling, an extension of ordinary linear modulation in which the usual data bearing pulses are simply sent faster, and consequently are no longer ...orthogonal. Far from a disadvantage, this innovation can transmit up to twice the bits as ordinary modulation at the same bit energy, spectrum, and error rate. The method is directly applicable to orthogonal frequency division multiplex (OFDM) and quadrature amplitude modulation (QAM) signaling. Performance results for a number of practical systems are presented. FTN signaling raises a number of basic issues in communication theory and practice. The Shannon capacity of the signals is considerably higher.
Generalization of the Concept of Bandwidth Mojahed, Alireza; Bergman, Lawrence A.; Vakakis, Alexander F.
Journal of sound and vibration,
09/2022, Volume:
533
Journal Article
Peer reviewed
Open access
•A new bandwidth concept for a broad class of dynamical systems is proposed.•Bandwidth relates to the energy decay rate by the Fourier uncertainty principle.•The new concept enables quantification of ...nonlinear inter-harmonic energy flow.•Applications are presented for hardening/softening and bi-stable nonlinear systems.
In the sciences and engineering, there is no generally accepted definition of bandwidth beyond those used to characterize low-loss linear time-invariant systems of low order operating at steady-state. In fact, the concept of bandwidth is often subject to interpretation depending upon context and the requirements of a specific community. The focus of this work is to formulate this concept for a general class of passive oscillatory dynamical systems, including but not limited to mechanical, structural, acoustic, electrical, and optical. Typically, the (linearized) bandwidth of these systems is determined by the half-power (-3 dB) method, and the result is often referred to as “half-power bandwidth.” The fundamental assumption underlying this definition is that the system performance degrades once its power decreases by 50%; moreover, there are restrictive conditions, rarely met, that render a system amenable to the use of this approach, such as linearity, low-dimensionality, low-loss, and stationary output. Here the concept of root mean square (RMS) bandwidth is considered, justified by the Fourier uncertainty principle, to generalize the definition of bandwidth to encompass linear/nonlinear, single/multi-mode, low/high loss and time-varying/invariant oscillating systems. By tying the bandwidth of an oscillatory dynamical system directly to its dissipative capacity, one can formulate a definition based solely on its transient energy evolution, effectively circumventing the previous restrictions. Further, applications are given that highlight the limitations of the traditional half-power bandwidth; these include a Duffing oscillator with hardening nonlinearity, and a bi-stable, geometrically nonlinear oscillator with tunable hardening or softening nonlinearity. The resulting energy-dependent bandwidth computations are compatible with the nonlinear dynamics of these systems, since at low energies they recover the (linearized) half-power bandwidth, whereas at high energies they accurately capture the nonlinear physics. Moreover, the bandwidth computation is directly tied to nonlinear harmonic generation in the transient dynamics, so that the contributions to the bandwidth of the individual harmonics and of inter-harmonic targeted energy transfers can be directly quantified and studied. The new bandwidth definition proposed in this work has broad applicability and can be regarded as a generalization of the traditional linear half-power bandwidth which is used widely in the sciences and engineering.
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