In a complex world, where networking expands very rapidly, the network stability of flow of bandwidth played a vital role in transmitting packets. Hence, it was imperative to find solution to the ...problem of congestion especially in the follow of bandwidth stability. Congestion in computer networking is caused by so many factors. Some of the signs are packet loss, queuing delay resulting from overloading the buffer, faulty hardware devices, intermixing of old and new technologies and unstable flow of bandwidth resulting from positive feedback A negative feedback mechanism was added to the network. Feedback was developed using both control and queuing theory. The congested signalling was tested for stability using control theory. Kendall notation was used to determine both arrival and service rates with all the queue disciplines. Matlab was used to simulate the model. Bode plots and impulse responses were used to analyse the performance of the improved model. The results showed that flow of bandwidth was stable with increase in service rate of packets and decrease in the probability of routers not accepting packets. This shows that adopting dynamic explicit feedback model reduced congestion by minimal packet drops, balanced flow of bandwidth, converges to fairness and minimized amplitude of oscillation.
We propose deep learning based communication methods for adaptive-bandwidth transmission of images over wireless channels. We consider the scenario in which images are transmitted progressively in ...layers over time or frequency, and such layers can be aggregated by receivers in order to increase the quality of their reconstructions. We investigate two scenarios, one in which the layers are sent sequentially, and incrementally contribute to the refinement of a reconstruction, and another in which the layers are independent and can be retrieved in any order. Those scenarios correspond to the well known problems of successive refinement and multiple descriptions , respectively, in the context of joint source-channel coding (JSCC). We propose DeepJSCC-<inline-formula> <tex-math notation="LaTeX">l </tex-math></inline-formula>, an innovative solution that uses convolutional autoencoders, and present three architectures with different complexity trade-offs. To the best of our knowledge, this is the first practical multiple-description JSCC scheme developed and tested for practical information sources and channels. Numerical results show that DeepJSCC-<inline-formula> <tex-math notation="LaTeX">l </tex-math></inline-formula> can learn to transmit the source progressively with negligible losses in the end-to-end performance compared with a single transmission. Moreover, DeepJSCC-<inline-formula> <tex-math notation="LaTeX">l </tex-math></inline-formula> has comparable performance with state of the art digital progressive transmission schemes in the challenging low signal-to-noise ratio (SNR) and small bandwidth regimes, with the additional advantage of graceful degradation with channel SNR.
•The real working mode of dual-mass gyroscope sense coupling mode is analyzed.•A high effective test method is proposed based on the sense mode feedback combs.•The restrict element of mechanical ...structure bandwidth is calculated and tested.•The proportional integral phase lead controller for sense close loop is proposed.•The bandwidth under wide-temperature are tested, the results verify the theory analysis.
This paper presents the bandwidth expanding method with wide-temperature range for sense mode coupling dual-mass MEMS gyro. The real sensing mode of the gyroscope is analyzed to be the superposition of in-phase and anti-phase sensing modes. The mechanical sensitivity and bandwidth of the gyroscope structure are conflicted with each other and both governed by the frequency difference between sensing and drive modes (min {Δω1, Δω2}). The sensing mode force rebalancing combs stimulation method (FRCSM) is presented to simulate the Coriolis force, and based on this method, the gyro’s dynamic characteristics are tested. The sensing closed- loop controller is achieved by operational amplifier based on phase lead method, which enable the magnitude margin and phase margin of the system to reach 7.21dB and 34.6° respectively, and the closed-loop system also expands gyro bandwidth from 13Hz (sensing open-loop) to 102Hz (sensing closed-loop). What’s more, the turntable test results show that the sensing closed-loop works stably in wide-temperature range (from −40°C to 60°C) and the bandwidth values are 107Hz @−40°C and 97Hz @60°C. The results indicate that the higher temperature causes lower bandwidth, and verify the simulation results are 103Hz @−40°C and 98.2Hz @60°C. The new bottleneck of the closed loop bandwidth is the valley generated by conjugate zeros, which is formed by superposition of sensing modes.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
A low-profile aperture-coupled microstrip patch antenna (MPA) using the TM10 and TM30 resonant modes to enhance the impedance bandwidth is proposed in this paper. Based on the cavity model for a ...square MPA, the TM10 and TM30 modes as well as both higher odd-order and even-order modes between them can be characterized. In order to combine the dual radiative resonant modes for a wide impedance bandwidth, a rectangular radiating patch with an aperture-coupled feeder is employed and theoretically investigated at first, aiming to demonstrate that all of the undesired modes between them can be removed effectively. After that, by loading the shorting pins properly underneath the patch, the resonant frequency of TM10 mode is shown to progressively turn up with slight effect on that of TM30 mode. As a result, these two radiative modes can be allocated in proximity to each other, resulting in a wide impedance bandwidth with a stable radiation pattern and the same far-field polarization. Moreover, the principal parameters of the MPA have been extensively studied in order to investigate the sensitivity in input impedance of the aperture-fed patch antenna. Finally, the proposed antenna is fabricated and measured. Simulated and measured results are found in good agreement with each other and illustrate that the antenna achieves a wide impedance bandwidth of about 15.2% in fraction or 2.32-2.70 GHz under |S 11 | <; -10 dB, while keeping a low profile property with the height of 0.032 free-space wavelength. Besides, a stable gain varied from 3 to 6.8 dBi within the whole operating band is also obtained.
A new class of compact, high-<inline-formula> <tex-math notation="LaTeX">Q </tex-math></inline-formula>, tunable coaxial filter is presented in this article based on a novel inset resonator concept. ...The tuning concept is based on the displacement of movable resonators inside a properly modified metallic housing which features wide tuning capabilities and stable high <inline-formula> <tex-math notation="LaTeX">Q </tex-math></inline-formula>-factor performance with minimum variation throughout the tuning window. Various prototypes are designed and implemented to demonstrate and validate the proposed concept. A single tunable inset resonator is first designed and measured showing distinctive results of a 43% tuning range, stable high-<inline-formula> <tex-math notation="LaTeX">Q </tex-math></inline-formula> of 4100% ± 4%, spurious-free band up to <inline-formula> <tex-math notation="LaTeX">3.8\times f_{0} </tex-math></inline-formula>, and volume-saving up to 50% when compared with the conventional combline and half-wavelength structures. The design procedure for constant absolute bandwidth (CABW) tunable filters is then presented, and two different tunable inset filters are designed and implemented. First, a manually tunable four-pole filter is demonstrated with the merits of a wide 39.3% tuning range, while maintaining a constant bandwidth of 116 MHz ± 6% and a stable high-<inline-formula> <tex-math notation="LaTeX">Q </tex-math></inline-formula> of 1820% ± 6%. Next, an automatically tunable third-order inset filter is designed and measured using high-accuracy piezomotors. Similarly, the measured results exhibit a wide 1.3-GHz tuning range from 2.65 to 3.95 GHz with a stable insertion loss that is less than 0.35 dB, a return loss that is better than 15 dB, and a good spurious performance up to <inline-formula> <tex-math notation="LaTeX">2.8\times f_{0} </tex-math></inline-formula>. To our own knowledge, the proposed tuning technique and tunable components represent state-of-the-art tuning range and stable high-<inline-formula> <tex-math notation="LaTeX">Q </tex-math></inline-formula> with minimal variation when compared with similar loaded-waveguide designs.
In a cloud computing environment, it is necessary to simultaneously allocate both processing ability and network bandwidth needed to access it. The authors proposed the joint multiple resource ...allocation method in a cloud computing environment that consists of multiple data centers with different Quality of Service (QoS). This article proposes to enhance the existing joint multiple resource allocation method, so that it can handle multiple heterogeneous resource-attributes. Resource-attributes of bandwidth, for example, are network delay time, packet loss probability, etc. The basic idea is to identify the key resource-attribute first which has the most impact on resource allocation, and to select the resources which provide the lowest QoS for the key resource-attribute as it satisfies required QoS. It is demonstrated by simulation evaluations that the enhanced method Method A can reduce the total amount of resources up to 30%, compared with the existing method. It is also highly likely that each data center provides the different network delay to users at multiple locations.
The TCP congestion control mechanism in standard implementations presents several problems, for example, large queue lengths in network routers and packet losses, a misleading reduce of the ...transmission rate when there are link failures, among others. This article proposes a schema to congestion control in TCP protocols, called NGWA, which is based on the network bandwidth. The NGWA provides information considering the available bandwidth of the network infrastructure to the endpoints of the TCP connection. Hence, it helps in choosing a better transmission rate for TCP improving its performance. Simulation results show superior performance of the proposed scheme when compared to those obtained by TCP New Reno and standard TCP. A physical implementation in the Linux kernel was performed to prove the correct operation of the proposal.
A century-old tenet in physics and engineering asserts that any type of system, having bandwidth Δω, can interact with a wave over only a constrained time period Δt inversely proportional to the ...bandwidth (Δt·Δω ~ 2π). This law severely limits the generic capabilities of all types of resonant and wave-guiding systems in photonics, cavity quantum electrodynamics and optomechanics, acoustics, continuum mechanics, and atomic and optical physics but is thought to be completely fundamental, arising from basic Fourier reciprocity. We propose that this “fundamental” limit can be overcome in systems where Lorentz reciprocity is broken. As a system becomes more asymmetric in its transport properties, the degree to which the limit can be surpassed becomes greater. By way of example, we theoretically demonstrate how, in an astutely designed magnetized semiconductor heterostructure, the above limit can be exceeded by orders of magnitude by using realistic material parameters. Our findings revise prevailing paradigms for linear, time-invariant resonant systems, challenging the doctrine that high-quality resonances must invariably be narrowband and providing the possibility of developing devices with unprecedentedly high time-bandwidth performance.
Full text
Available for:
BFBNIB, NMLJ, NUK, ODKLJ, PNG, SAZU, UL, UM, UPUK
Fiber-optic multi-band transmission (MBT) aims at exploiting the low-loss spectral windows of single-mode fibers (SMFs) for data transport, expanding by <inline-formula><tex-math ...notation="LaTeX">\sim\!11\times</tex-math></inline-formula> the available bandwidth of C-band line systems and by <inline-formula><tex-math notation="LaTeX">\sim\!5\times</tex-math></inline-formula> C+L-band line systems'. MBT offers a high potential for cost-efficient throughput upgrades of optical networks, even in absence of available dark-fibers, as it utilizes more efficiently the existing infrastructures. This represents the main advantage compared to approaches such as multi-mode/-core fibers or spatial division multiplexing. Furthermore, the industrial trend is clear: the first commercial C<inline-formula><tex-math notation="LaTeX">+</tex-math></inline-formula>L-band systems are entering the market and research has moved toward the neighboring S-band. This article discusses the potential and challenges of MBT covering the ITU-T optical bands O <inline-formula><tex-math notation="LaTeX">\rightarrow</tex-math></inline-formula> L. MBT performance is assessed by addressing the generalized SNR (GSNR) including both the linear and non-linear fiber propagation effects. Non-linear fiber propagation is taken into account by computing the generated non-linear interference by using the generalized Gaussian-noise (GGN) model, which takes into account the interaction of non-linear fiber propagation with stimulated Raman scattering (SRS), and in general considers wavelength-dependent fiber parameters. For linear effects, we hypothesize typical components' figures and discussion on components' limitations, such as transceivers,' amplifiers' and filters' are not part of this work. We focus on assessing the transmission throughput that is realistic to achieve by using feasible multi-band components without specific optimizations and implementation discussion. So, results are meant to address the potential throughput scaling by turning-on excess fiber transmission bands. As transmission fiber, we focus exclusively on the ITU-T G.652.D, since it is the most widely deployed fiber type worldwide and the mostly suitable to multi-band transmission, thanks to its ultra-wide low-loss single-mode high-dispersion spectral region. Similar analyses could be carried out for other single-mode fiber types. We estimate a total single-fiber throughput of 450 Tb/s over a distance of 50 km and 220 Tb/s over regional distances of 600 km: <inline-formula><tex-math notation="LaTeX">\sim\!10\times</tex-math></inline-formula> and 8× more than C-band transmission respectively and <inline-formula><tex-math notation="LaTeX">\sim\!2.5\times</tex-math></inline-formula> more than full C+L.
We propose a new sampling theorem, the complete reconstruction of a function from its samples, for the space of variable bandwidth constructed using Wilson expansions. The theorem is based on the ...maximal gap between consecutive points and it relates the lower sampling rate to the bandwidths that have an influence on the reconstruction on each particular interval of the signal.
PDF
