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Long-duration quantum memories for photonic qubits are essential components for achieving long-distance quantum networks and repeaters. The mapping of optical states onto coherent spin-waves in rare earth ensembles is a particularly promising approach to quantum storage. However, it remains challenging to achieve long-duration storage at the quantum level due to read-out noise caused by the required spin-wave manipulation. In this work, we apply dynamical decoupling techniques and a small magnetic field to achieve the storage of six temporal modes for 20, 50, and 100 ms in a 151Eu3+:Y2SiO5 crystal, based on an atomic frequency comb memory, where each temporal mode contains around one photon on average. The quantum coherence of the memory is verified by storing two time-bin qubits for 20 ms, with an average memory output fidelity of F = (85 ± 2)% for an average number of photons per qubit of μin = 0.92 ± 0.04. The qubit analysis is done at the read-out of the memory, using a type of composite adiabatic read-out pulse we developed. [ABSTRACT FROM AUTHOR]

In all Hard IP (HIP) designs, there is a need for signals to travel from its source to destination module. To meet timing, they are flop repeated based on the floorplan of the design. Different signals have unique repetition requirements based on their functionality/timing criticality. Also signals may have single destination or multiple destinations. The flop repeater structure for each signal should be optimized so that it has minimum number of flops and timing is also met, to achieve desired targets for timing, area and power. This paper will show how we are creating optimized tree structure based on mathematical techniques and generating automated RTL for such repeater flop module. This submission presents a new tool ART (Auto Repeater Tool) that completely eliminates the manual effort/time required to generate functional, ready to plug-in RTL. [ABSTRACT FROM AUTHOR]

A novel and highly accurate finite-difference time-domain model is developed for bundled single-walled carbon nanotube (SWCNT) interconnects by considering a fixed configuration that consists of a CMOS driver, a bundled SWCNT interconnect system, and an optimal number of repeaters. Using superposition theorem, this iterative model is applied to the entire chain of repeaters to calculate the total closed-loop delay. An accurate transfer function is modeled for the chain of equi-spaced repeaters in the interconnect system. The transfer function is further used to develop an analytical model for closed-loop delay, considering the optimum number of repeaters as dependent parameter. Further, in order to determine the minimum delay, an analysis is performed to find out the optimum number of repeaters for a given interconnect length. In addition, a detailed study is carried out to observe the impact of interconnect length on time delay, the time delay reduction on increasing the number of repeaters and the effect of excitation magnitude on time delay with power delay product. It is observed that by using SWCNT interconnects, the total number of repeaters and the time delay are reduced by more than 40 and 50%, respectively, compared with the copper (Cu) interconnects. However, the proposed model achieves extreme accuracy, with 4% relative tolerance at maximum, in predicting interconnect performance based on comparison with the HSPICE simulations. [ABSTRACT FROM AUTHOR]

Industrial safety refers to the prevention of industrial accidents by limiting the factors that cause them. In other words, it encompasses all the activities required to safeguard and maintain industrial facilities and protect workers from all health issues caused by the disasters or accidents incurred by industrial activities. However, inadequate industrial safety education, a lack of preventative systems, and a lack of predictive facilities have led to frequent industrial accidents. These industrial accidents increase economic losses and lead to an increase also in the number of workers’ deaths and injuries. The objective of the study presented in this paper was therefore to develop a disaster prevention system to ensure the safety of workers in extreme industrial fields. In the system, peer-to-peer (P2P) sensor network technology is applied to allow the status of the worksite to be monitored in real time by the general management center, field manager, and workers in the industrial field. For the system, we developed a smartphone application that transmits the results of a harmful gas detection module and a workplace escape map, and designed a structure that connects the management center and field workers through a wireless communication repeater. In addition, we propose an integrated system that collects disaster information in real time through the P2P sensor network system. In the future, when disasters occur, the person in charge and the manager will be able to transmit information in real time, which will all owa rapid response to situations. [ABSTRACT FROM AUTHOR]

This paper presents an active cancellation method based on repeater jamming to weaken the incident wave rather than to weaken the scattered wave in conventional method. The method works well on chirp-subpulse stepped frequency (CSSF) signal. The incident plane wave is interfered by a spherical wave which is generated by a horizontal electric dipole. The analysis and simulation show that the plane wave can be reduced obviously via this method. By incorporating frequency and phase modulation, the backscattering of the target is reduced significantly. Numerical experiments also show that with greater wavelength, the cancellation performance gets better. [ABSTRACT FROM AUTHOR]

Closed-form expressions for the optimized number and size of repeaters in multi-walled carbon nanotube (MWCNT) interconnects are presented. The contact resistance and inductive effects are taken into account. It is found that the propagation delay of MWCNT interconnects can be reduced effectively by inserting repeaters. However, the contact resistance has a significant influence on the optimized number and size of repeaters. Moreover, it is found that both the optimal number of repeaters and the minimum propagation delay are kept almost unchanged with the variation of carbon nanotube (CNT) kinetic inductance. The optimal number of repeaters in the MWCNT interconnect is much smaller than that in its Cu counterpart, thus saving chip area and power consumption. [ABSTRACT FROM AUTHOR]

Dual-band coil modules facilitate efficient access to distinct-band, high-power, or rapid-charging wireless power transfer (WPT) systems. However, they do not function efficiently when the frequency ratio between two operating frequencies is large. To overcome this problem, we propose enhanced dual-band coil modules that adopt repeaters in the WPT system. We present a circuit-based analysis of repeaters in various dual-band coil modules compared with those in a single-band WPT system. The analytical results provide a design methodology applicable to diverse types of dual-band coil modules with a repeater in the WPT system. Our experimental results are consistent with the circuit-based analysis: coil power transfer efficiencies of 55% at 200 kHz and 74% at 6.78 MHz were obtained concurrently in the dual-band WPT system with a dual-band repeater. This paper reduced the application constraint of dual-band coil modules and facilitated the realization and application of multiband WPT systems. [ABSTRACT FROM PUBLISHER]

For frequency division duplex channels, a simple pilot loop-back procedure has been proposed that allows the estimation of the uplink (UL) and downlink (DL) channel subspaces between an antenna array and a fully analog repeater. For this scheme, we derive the maximum likelihood (ML) estimators for the UL and DL subspaces, formulate the corresponding Cramér–Rao bounds, and show the asymptotic efficiency of both (singular value decomposition (SVD) based) estimators by means of Monte Carlo simulations. In addition, we illustrate how to compute the underlying (rank-1) SVD with quadratic time complexity by employing the power iteration method. To enable power control for the data transmission, knowledge of the channel gains is needed. Assuming that the UL and DL channels have on average the same gain, we formulate the ML estimator for the uplink channel vector norm, and illustrate its robustness against strong noise perturbations by means of simulations. [ABSTRACT FROM PUBLISHER]

Interrupted-sampling repeater jamming (ISRJ) provides a novel coherent-jamming mode against wideband radar. ISRJ allows the single-antenna jammer to periodically sample and repeat a fraction of the intercepted signal, which reduces the sampling rate and achieves transmit-receive isolation. The coherent-jamming signal generated by ISRJ can form multiple verisimilar false targets when received and processed by the victim radar receiver. Moreover, some false targets can precede the real target. This paper surveys the use of ISRJ in linear frequency modulated (LFM) radar jamming. The theory and application of ISRJ has been researched for more than one decade, but what is missing is a completed summary for the framework of this technique. In this paper, mathematic principles of ISRJ against LFM radars, which utilize matched-filter processing, stretch processing, and range-Doppler processing, are developed. The unique jamming effects in radar systems are focused on when the interrupted sampling frequency of the jammer is smaller than the bandwidth of the radar signal. Specifically, the false-target characteristics, including amplitude, space distribution, and phase, are discussed, respectively. On this basis, the key jamming elements, which determine these false-target characteristics, are pointed out and analyzed in detail. At last, simulation and real data are used to verify the correctness of the analyses. Experimental results highlight the potential application of the proposed jamming mode. [ABSTRACT FROM PUBLISHER]

Wireless charging has provided a convenient alternative to renew nodes’ energy in wireless sensor networks. Due to physical limitations, previous works have only considered recharging a single node at a time, which has limited efficiency and scalability. Recent advances on multi-hop wireless charging is gaining momentum and provides fundamental support to address this problem. However, existing single-node charging designs do not consider and cannot take advantage of such opportunities. In this paper, we propose a new framework to enable multi-hop wireless charging using resonant repeaters. First, we present a realistic model that accounts for detailed physical factors to calculate charging efficiencies. Second, to achieve balance between energy efficiency and data latency, we propose a hybrid data gathering strategy that combines static and mobile data gathering to overcome their respective drawbacks and provide theoretical analysis. Then, we formulate multi-hop recharge schedule into a bi-objective NP-hard optimization problem. We propose a two-step approximation algorithm that first finds the minimum charging cost and then calculates the charging vehicles’ moving costs with bounded approximation ratios. Finally, upon discovering more room to reduce the total system cost, we develop a post-optimization algorithm that iteratively adds more stopping locations for charging vehicles to further improve the results while ensuring none of the nodes will deplete battery energy. Our extensive simulations show that the proposed algorithms can handle dynamic energy demands effectively, and can cover at least three times of nodes and reduce service interruption time by an order of magnitude compared to the single-node charging scheme. [ABSTRACT FROM AUTHOR]

Interrupted sampling repeater jamming (ISRJ) is an effective coherent jamming, which can induce false high-resolution range profile (HRRP) and image to greatly complicate the target detection and recognition of wideband radar. To counter ISRJ, an efficient filter is designed based on the time-frequency (TF) characteristic differences between target echo and ISRJ. Meanwhile, a feasible jamming suppression scheme is proposed, which not only could eliminate ISRJ but also could reserve the target echo. The main emphasis is that the received echo suppressed by our scheme is similar with the true target's HRRP on the basis of high correlation coefficient (CC) and large signal-jamming-to-noise ratio (SJNR) improvement factor. Simulation results are covered to illustrate the feasibility and validness of jamming suppression. [ABSTRACT FROM AUTHOR]

Since Feynman first proposed the idea of simulating a quantum system using another quantum system in 1981 [1], substantial progress has been made to control the individual quantum systems; now, many technology companies have become involved in quantum technology. SK Telecom has been developing various quantum technologies for the last five years, and an overview of the progress in the development of a quantum key distribution system, quantum random number generator chips, and a quantum repeater will be given in this article. [ABSTRACT FROM AUTHOR]

In the literature, surfing technique has been proposed for differential on-chip wave-pipelined serial interconnects with uniform repeaters (UR) and non-uniform repeaters to increase the data transfer rate for unidirectional schemes. In this paper, a novel bidirectional data transfer through the differential wave-pipelined serial interconnects with surfing for UR is proposed. A new circuit called 'Bidirectional surfing inverter pair' is proposed for differential wave-pipelined serial interconnects. The method of logical effort is used for the design of surfing circuits. To evaluate the efficiency of these techniques, 40 mm metal 4 interconnects using the proposed surfing techniques are implemented along with transmitter, receiver and delay locked loop in UMC 180 nm technology and their performances are studied through post layout simulations. The proposed bidirectional differential surfing scheme has a maximum data transfer rate of 2 Gb/s and has allowable jitter of 52 ps on both directions through the same interconnects. [ABSTRACT FROM AUTHOR]

A new closed-form expression of 50% propagation delay for distributed RLC interconnects is proposed using the multivariable curve fitting method, with a maximum error of 4% with respect to SPICE results. Then accurate closed-form solutions for the optimum repeater number and size to minimize the propagation delay are further derived. The performance of single-walled carbon nanotube (SWCNT) bundle interconnects is evaluated using the proposed models in the intermediate and global levels at the 22- and 32-nm technology nodes, and compared against traditional Cu interconnects. It is shown that the performance of SWCNT bundle interconnects in propagation delay can outperform Cu interconnects, and the improvement will be enhanced with technology scaling and wire length increasing. On the other hand, the propagation delay of SWCNT bundle interconnects is super-linearly dependent on the wire length similar to Cu interconnects, indicating that the method of repeater insertion to reduce the propagation delay can also apply to SWCNT bundle interconnects. The results shown that repeater insertion can really reduce the propagation delay of SWCNT bundle interconnects effectively, and the optimum repeater number is much smaller than that of Cu interconnects. [ABSTRACT FROM AUTHOR]

To realize efficient quantum communication based on quantum repeater, we propose a secure quantum network coding scheme for controlled repeater networks, which adds a controller as a trusted party and is able to control the process of EPR-pair distribution. As the key operations of quantum repeater, local operations and quantum communication are designed to adopt quantum one-time pad to enhance the function of identity authentication instead of local operations and classical communication. Scheme analysis shows that the proposed scheme can defend against active attacks for quantum communication and realize long-distance quantum communication with minimal resource consumption. [ABSTRACT FROM AUTHOR]

Due to the accelerated evolution of application services, optical network virtualization simplifies optical-layer resource management and provides flexibility in spectrum resource allocation. However, the energy consumption is one of the great challenges in the virtual optical networks (VONs). This paper focuses on the energy efficiency problem in survivable VONs with the sliceable multi-flow transponders and the elastic regenerators. For each VON, all virtual links provide the dedicated-path protection in the flexible bandwidth optical networks. An integer linear program (ILP) and a minimum unit-energy submatrix (MinEnSub) VON mapping approach are developed to improve the energy efficiency, minimize the power consumption, and reduce the spectrum usage under different line rates. For comparison, a baseline VON mapping approach is introduced. Simulation results show that the ILP model and the proposed MinEnSub VON mapping approach can save power consumption, improve the energy efficiency, and reduce the spectrum usage compared with the baseline VON mapping approach in a 6-node network. As expected, in a 14-node network, simulation results also validate that our proposed MinEnSub VON mapping approach can achieve better performance in terms of power consumption, energy efficiency, number of frequencies, and the number of regenerators. [ABSTRACT FROM AUTHOR]

ABSTRACT A dual-band on-body antenna for in-on-on wireless body area network repeater applications is proposed. This antenna consists of a dual-patch antenna and a zeroth-order resonance (ZOR) element. The two patch antenna elements form dual resonances that cover the 2.4 GHz ISM band. In addition, a triangle cut made at the lower edge of patch Element 1 improves the impedance matching in the 2.4 GHz ISM band. The ZOR element operates in the 403 MHz MICS band. The antenna has near surface radiation in the 2.4 GHz ISM band and nearly omnidirectional radiation in the 403 MHz MICS band. To evaluate the performance of the antenna on a human body, the proposed antenna is placed on a human equivalent flat phantom. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:436-441, 2016 [ABSTRACT FROM AUTHOR]

Currently, terrestrial digital multimedia broadcasting (T-DMB) systems offer an emergency alert service called automatic emergency alert service (AEAS) in emergency alert systems. The performance of T-DMB receiver for AEAS can be enhanced using cooperative communication techniques. This paper assumes the T-DMB receiver based on a cooperative communication model. Since synchronization is crucial in the performance of cooperative communications, a novel consumer synchronizer is proposed in this paper for the T-DMB receiver based on cooperative communications. The presented synchronizer includes the identification of the selected relays, which is especially required in the best-relay selection for cooperative communications. Furthermore, a channel estimation approach is suggested in the synchronizer, which is suitable for T-DMB receivers under high frequencyselectivity. The experimental results reveal that the proposed synchronizer further enhances the performance of T-DMB receiver based on cooperative communications in emergency alert systems. [ABSTRACT FROM AUTHOR]

In this paper, we have analyzed the performance of our optimized non-zero dispersion shifted fiber with three different test fibers, namely, single mode fiber, conventional non-zero dispersion shifted fiber and dispersion shifted fiber. While comparing the performances of those fibers, our optimized non-zero dispersion shifted fiber has yielded a better quality factor of 5.24 at 2.5 Gbit/s for long haul fiber length of 120 km in the absence of amplification and dispersion compensation. In order to measure the nonlinear impairments of wavelength division multiplexing channel, the quality factor values are measured at the sample channel 193.1 THz for 150 km lengthed fiber with peak input power of 6 dBm. Due to a very large effective area of optimized non-zero dispersion shifted fiber, it delivers a better quality factor of 6.12 compared to the other test fibers. We have also carried out the analysis for higher bitrates and different modulation formats at the transmission end. More phase encoded modulations of carrier-suppressed return-to-zero-differentiated phase shift keying and carrier-suppressed return-to-zero-differential quadrature phase shift keying offered optimum performances for a distance of 120 km at 10 Gbit/s bitrate. By including optical amplifiers, we could achieve a record fiber transmission length of 4000 km at the bitrate of 2.5 Gbit/s which can help the future wavelength division multiplexing optical networks to a great extent. [ABSTRACT FROM AUTHOR]

This paper proposes a quantum network coding scheme for general repeater networks so as to support long-distance quantum communication over quantum repeater networks with complex topology. The scheme includes three core parts: graph transformation, quantum channel generation, quantum information transmission. Concretely, the degree-3 $$({{D}_{3}})$$ graph transformation scheme is introduced, the quantum channel generation schemes for the cases of one-to-many, many-to-one, and many-to-many are given, and quantum information is transmitted by means of quantum teleportation. Without limitation of preparation, entangled states with arbitrary entanglement degree can be consumed as a resource of quantum communication. Scheme analysis shows that the proposed quantum network coding scheme can realize high-rate and long-distance transmission of quantum information in general networks. [ABSTRACT FROM AUTHOR]

In this study, we examine the performance of fixed gain amplify-and-forward repeaters for visible light communication (VLC) systems. We present the wireless optical channel model for VLC with the repeater and we evaluate the bit-error-rate (BER) performance for pulse-position modulation over the multipath channel with additive white Gaussian noise. The results reveal that when a repeater is placed, both the BER and the illuminance performance can be improved at any location in a typical office space. The benefit of VLC repeaters is also discussed when the channel from the source to the destination is shadowed. It is found that when the channel is shadowed, the impact of repeaters on the communication reliability is more distinct. [ABSTRACT FROM AUTHOR]

A compact 3-D dual-channel transceiver for passive wireless sensor node design is described herein. The transceiver contains two harmonic repeaters, one to be connected to a sensor and one to provide a reference signal for remote channel calibration and node identification (ID). Each repeater consists of a diode-based frequency doubler and conjugate-matched receive and transmit meandered monopole antennas. The sensing repeater operates by receiving a 2.4-GHz signal and reradiating a modulated 4.8-GHz return signal. The reference and sensing repeaters are optimized for RF input power level ranges from -\30 to -\20 dBm with zero dc power. The diagonal of the transceiver measures 0.25 \lambda at the fundamental frequency of 2.4 GHz and its measured conversion gain (CG) is -\ 12.4 dB with a 2% 3-dB CG bandwidth at -\20-dBm input power. With this performance, the communication range using an interrogator with a 2-W effective isotropic radiated power is > \40 m in a free-space environment. To the best of the authors' knowledge, the presented transceiver is the first completely passive design with built-in passive remote channel calibration and ID capability. The performance and size of the proposed design compare well with previously published passive single-channel harmonic repeaters. [ABSTRACT FROM PUBLISHER]

This paper resolves the performance issue encountered in very‐large‐scale integration interconnects due to downsizing of integrated circuits. Interconnects designed using carbon nanotubes (CNT) are compared with conventional copper interconnect. The propagation delay of very lengthy interconnect wires is ameliorated by interpolating smart buffers as repeaters within the wires. Existing buffer designs are contrived using both CNT and MOS technology for comparison using a different combination of MOS repeater‐Cu interconnect and CNT repeater‐CNT interconnect. Propound buffer uses power gating techniques and automated toggling approach to reduce delay besides mitigating average power consumption. Compared to conventional buffer, PropoundDesign3 brings about dynamic power saving of 99.94% and leakage power saving of 93%, but causes delay penalty. PropoundDesign2 saves dynamic power by 99.86% and leakage power by 88% and offers reduction in delay by 52%. Whereas PropoundDesign1 saves dynamic power by 98% and reduces propagation delay by 64% but on the cost of leakage power consumption. Simulation for 32 nm is done in HSPICE by considering a section of long interconnect line as driver interconnect load system using Stanford SPICE model for CNT and BSIM4 PTM for MOS. [ABSTRACT FROM AUTHOR]

A reconfigurable wearable repeater antenna (RWRA) for wireless body area network (WBAN) applications is proposed. The RWRA can work at triple‐mode by controlling the state of PIN diodes, which are repeater, on‐body and off‐body modes. The antenna is fed by a single port at side instead of bottom for the sake of reducing the profile and improving the coupling strength between the RWRA and an implantable antenna. The total size of the antenna is π × 282 × 4.8 mm3. To validate the performance, the RWRA is fabricated and measured on minced pork. Measured bandwidths at repeater and on‐/off‐body modes are 5.8, 84, and 54 MHz, respectively. Radiation patterns are omnidirectional with vertical polarization at on‐body mode and broadside at off‐body mode, which measured peak gains are 1.2 and 5.4 dBi, respectively. Specific absorption rate (SAR) values at all three modes are analyzed in this article as well. Coupling strength between the RWRA and an implantable antenna is also measured. Besides, the effect of distance and misalignment between them are analyzed. [ABSTRACT FROM AUTHOR]

In the quantum repeater networks of the quantum Internet, the varying stability of entangled quantum links makes dynamic topology adaption an emerging issue. Here we define an efficient topology adaption method for quantum repeater networks. The model assumes the random failures of entangled links and several parallel demands from legal users. The shortest path defines a set of entangled links for which the probability of stability is above a critical threshold. The scheme is utilized in a base-graph of the overlay quantum network to provide an efficient shortest path selection for the demands of all users of the network. We study the problem of entanglement assignment in a quantum repeater network, prove its computational complexity, and show an optimization procedure. The results are particularly convenient for future quantum networking, quantum Internet, and experimental long-distance quantum communications. [ABSTRACT FROM AUTHOR]

The radio frequency feedback (RFF) occurs when the insulation is insufficient between the antennas of an on-frequency repeater, increasing digital transmission errors. In addition, a strong RFF could compromise system stability of the on-frequency repeater because of the growing power in the closed-loop. Automatic gain control is widely used by the on-frequency repeater to regulate the power, this solution being generally used with echo cancellation processes. Most of echo cancellation techniques are based on digital processing such as adaptive filters whose the effectiveness and the algorithm speed are depending on the signal frequency, the bandwidth and the closed-loop parameters. This paper describes a solution of RFF estimation and detection regardless of the receiving signal modulation. By using the frequency scanning and the analysis of the power spectral density peaks in the system, this solution is reliable whatever are the values of the gain-margin and the loop-delay. Simulations and experimental implementation using field-programmable gate array validate the solution. In addition, an example of applications is given in the context of the interference cancellation. [ABSTRACT FROM AUTHOR]