Showing papers on "Bandwidth (signal processing) published in 2017"
TL;DR: This survey provides the reader with comprehensive details on the use of space-based optical backhaul links in order to provide high capacity and low cost backhaul solutions.
Abstract: In recent years, free space optical (FSO) communication has gained significant importance owing to its unique features: large bandwidth, license free spectrum, high data rate, easy and quick deployability, less power, and low mass requirements. FSO communication uses optical carrier in the near infrared band to establish either terrestrial links within the Earth’s atmosphere or inter-satellite/deep space links or ground-to-satellite/satellite-to-ground links. It also finds its applications in remote sensing, radio astronomy, military, disaster recovery, last mile access, backhaul for wireless cellular networks, and many more. However, despite of great potential of FSO communication, its performance is limited by the adverse effects (viz., absorption, scattering, and turbulence) of the atmospheric channel. Out of these three effects, the atmospheric turbulence is a major challenge that may lead to serious degradation in the bit error rate performance of the system and make the communication link infeasible. This paper presents a comprehensive survey on various challenges faced by FSO communication system for ground-to-satellite/satellite-to-ground and inter-satellite links. It also provides details of various performance mitigation techniques in order to have high link availability and reliability. The first part of this paper will focus on various types of impairments that pose a serious challenge to the performance of optical communication system for ground-to-satellite/satellite-to-ground and inter-satellite links. The latter part of this paper will provide the reader with an exhaustive review of various techniques both at physical layer as well as at the other layers (link, network, or transport layer) to combat the adverse effects of the atmosphere. It also uniquely presents a recently developed technique using orbital angular momentum for utilizing the high capacity advantage of optical carrier in case of space-based and near-Earth optical communication links. This survey provides the reader with comprehensive details on the use of space-based optical backhaul links in order to provide high capacity and low cost backhaul solutions.
1,592 citations
TL;DR: Techniques for photonics-based broadband and high-speed microwave measurement are discussed with an emphasis on the system architectures for microwave signal parameter measurement and object property identification.
Abstract: Microwave measurement refers to the acquisition of parameters of a microwave signal or the identification of properties of an object via microwave-based approaches. Thanks to the broad bandwidth and high speed provided by modern photonics, microwave measurement in the optical domain can provide better performance in terms of bandwidth and speed which may not be achievable using traditional, even state-of-the-art electronics. In this tutorial, techniques for photonics-based broadband and high-speed microwave measurement are discussed with an emphasis on the system architectures for microwave signal parameter measurement and object property identification. Emerging technologies in this area and possible future research directions are also discussed.
296 citations
TL;DR: In this paper, closed-form expressions relating the channel coherence time and beamwidth are derived and the pointing error due to the receiver motion is incorporated to show that there exists a nonzero optimal beamwidth that maximizes the coherenceTime.
Abstract: Millimeter wave (mmWave) has great potential in realizing high data rates, thanks to the large spectral channels. It is considered as a key technology for fifth-generation (5G) wireless networks and is already used in wireless LAN (e.g., IEEE 802.11ad). Using mmWave for vehicular communications, however, is often viewed with some skepticism due to a misconception that the Doppler spread would become too large at these high frequencies. This is not necessarily true when directional beams are employed. In this paper, closed-form expressions relating the channel coherence time and beamwidth are derived. Unlike prior work that assumed perfect beam pointing, the pointing error due to the receiver motion is incorporated to show that there exists a nonzero optimal beamwidth that maximizes the coherence time. We define a novel concept of beam coherence time, which is an effective measure of beam alignment frequency. Using the derived correlation function, the channel coherence time, and the beam coherence time, an overall performance metric considering both the channel time variation and the beam alignment overhead is derived. Using this metric, it is shown that beam realignment in every beam coherence time performs better than beam realignment in every channel coherence time.
295 citations
TL;DR: The design of multi-resolution beamforming sequences to enable the system to quickly search out the dominant channel direction for single-path channels are considered, which generates a multilevel beamforming sequence that strikes a balance between minimizing the training overhead and maximizing beamforming gain.
Abstract: Millimeter wave (mm-wave) communication is expected to be widely deployed in fifth generation (5G) wireless networks due to the substantial bandwidth available for licensed and unlicensed use at mm-wave frequencies. To overcome the higher path loss observed at mm-wave bands, most prior work focused on the design of directional beamforming using analog and/or hybrid beamforming techniques in large-scale multiple-input multiple-output systems. Obtaining potential gains from highly directional beamforming in practical systems hinges on sufficient levels of channel estimation accuracy, where the problem of channel estimation becomes more challenging due to the substantial training overhead needed to sound all directions using a high-resolution narrow beam. In this paper, we consider the design of multi-resolution beamforming sequences to enable the system to quickly search out the dominant channel direction for single-path channels. The resulting design generates a multilevel beamforming sequence that strikes a balance between minimizing the training overhead and maximizing beamforming gain, where a subset of multilevel beamforming vectors is chosen adaptively to maximize the average data rate within a constrained time. We propose an efficient method to design a hierarchical multi-resolution codebook utilizing a Butler matrix, i.e., a generalized discrete Fourier transform matrix. Numerical results show the effectiveness of the proposed algorithm.
288 citations
TL;DR: A high-throughput communication approach using the orbital angular momentum (OAM) of acoustic vortex beams with one order enhancement of the data transmission rate at a single frequency is demonstrated.
Abstract: Long-range acoustic communication is crucial to underwater applications such as collection of scientific data from benthic stations, ocean geology, and remote control of off-shore industrial activities. However, the transmission rate of acoustic communication is always limited by the narrow-frequency bandwidth of the acoustic waves because of the large attenuation for high-frequency sound in water. Here, we demonstrate a high-throughput communication approach using the orbital angular momentum (OAM) of acoustic vortex beams with one order enhancement of the data transmission rate at a single frequency. The topological charges of OAM provide intrinsically orthogonal channels, offering a unique ability to multiplex data transmission within a single acoustic beam generated by a transducer array, drastically increasing the information channels and capacity of acoustic communication. A high spectral efficiency of 8.0 ± 0.4 (bit/s)/Hz in acoustic communication has been achieved using topological charges between -4 and +4 without applying other communication modulation techniques. Such OAM is a completely independent degree of freedom which can be readily integrated with other state-of-the-art communication modulation techniques like quadrature amplitude modulation (QAM) and phase-shift keying (PSK). Information multiplexing through OAM opens a dimension for acoustic communication, providing a data transmission rate that is critical for underwater applications.
287 citations
TL;DR: The proposed photonics-based radar is an effective solution to overcome the limitations on operation bandwidth and processing speed of current radar imaging technologies, which may enable applications where high-resolution and real-time radar imaging is required.
Abstract: A photonics-based radar with generation and de-chirp processing of broadband linear frequency modulated continuous-wave (LFMCW) signal in optical domain is proposed for high-resolution and real-time inverse synthetic aperture radar (ISAR) imaging. In the proposed system, a broadband LFMCW signal is generated by a photonic frequency quadrupler based on a single integrated electro-optical modulator, and the echoes reflected from the targets are de-chirped to a low frequency signal by a microwave photonic frequency mixer. The proposed radar can operate at a high frequency with a large bandwidth, and thus achieve an ultra-high range resolution for ISAR imaging. Thanks to the wideband photonic de-chirp technique, the radar receiver could apply low-speed analog-to-digital conversion and mature digital signal processing, which makes real-time ISAR imaging possible. A K-band photonics-based radar with an instantaneous bandwidth of 8 GHz (18-26 GHz) is established and its performance for ISAR imaging is experimentally investigated. Results show that a recorded two-dimensional imaging resolution of ~2 cm × ~2 cm is achieved with a sampling rate of 100 MSa/s in the receiver. Besides, fast ISAR imaging with 100 frames per second is verified. The proposed radar is an effective solution to overcome the limitations on operation bandwidth and processing speed of current radar imaging technologies, which may enable applications where high-resolution and real-time radar imaging is required.
265 citations
TL;DR: The local cut-off frequency is adaptively designed by fully facilitating the instantaneous amplitude and frequency information and is able to improve the frequency separation performance, as well as the stability under low sampling rates.
257 citations
4 Oct 2017
TL;DR: This paper presents RFind, a new technology that brings the benefits of ultra-wideband localization to the billions of RFIDs in today's world and can emulate over 220MHz of bandwidth on tags designed with a communication bandwidth of only tens to hundreds of kHz, while remaining compliant with FCC regulations.
Abstract: State-of-the-art RFID localization systems fall under two categories. The first category operates with off-the-shelf narrowband RFID tags but makes restrictive assumptions on the environment or the tag's movement patterns. The second category does not make such restrictive assumptions; however, it requires designing new ultra-wideband hardware for RFIDs and uses the large bandwidth to directly compute a tag's 3D location. Hence, while the first category is restrictive, the second one requires replacing the billions of RFIDs already produced and deployed annually. This paper presents RFind, a new technology that brings the benefits of ultra-wideband localization to the billions of RFIDs in today's world. RFind does not require changing today's passive narrowband RFID tags. Instead, it leverages their underlying physical properties to emulate a very large bandwidth and uses it for localization. Our empirical results demonstrate that RFind can emulate over 220MHz of bandwidth on tags designed with a communication bandwidth of only tens to hundreds of kHz, while remaining compliant with FCC regulations. This, combined with a new super-resolution algorithm over this bandwidth, enables RFind to perform 3D localization with sub-centimeter accuracy in each of the x/y/z dimensions, without making any restrictive assumptions on the tag's motion or the environment.
250 citations
TL;DR: Results show that the proposed method outperforms EMD-AMma, ensemble empirical mode decomposition-AMMA, and generalized empirical mode decompposition-empirical envelope demodulation in detecting early inner race fault.
Abstract: This paper presents a novel signal processing scheme, bandwidth empirical mode decomposition, and adaptive multiscale morphological analysis (BEMD-AMMA) for early fault diagnosis of rolling bearings. In this scheme, we propose a bandwidth based method to select the best envelope interpolation method. First, multiple envelope algorithms are defined and separately subtracted from the original data to obtain the preintrinsic mode functions (PIMFs). Second, an IMF with the smallest frequency bandwidth is selected to be the optimal IMF (OIMF). Third, this OIMF is subtracted from the original signal, and then repeat the sifting process until the residual is a constant or monotonic. Since the OIMF has the smallest frequency bandwidth, the mode mixing phenomenon can be significantly weakened. After that the OIMFs with clear fault information are used to construct the main component of the original signal. Then, the AMMA is introduced to demodulate the constructed main component. Simulation and experimental vibration signals are employed to evaluate the effectiveness of the proposed method. Results show that the proposed method outperforms EMD-AMMA, ensemble empirical mode decomposition-AMMA, and generalized empirical mode decomposition-empirical envelope demodulation in detecting early inner race fault.
235 citations
TL;DR: The mmWave channel sounder described here may be used for accurate spatial and temporal ray-tracing calibration, to identify individual multipath components, to measure antenna patterns, for constructing spatial profiles of mmWave channels, and for developing statistical channel impulse response models in time and space.
Abstract: This paper presents a novel ultrawideband wireless spread spectrum millimeter-wave (mmWave) channel sounder that supports both a wideband sliding correlator mode and a realtime spread spectrum mode, also known as wideband correlation or direct correlation. Both channel sounder modes are capable of absolute propagation delay (time of flight) measurements with up to 1 GHz of radio frequency null-to-null bandwidth, and can measure multipath with a 2-ns time resolution. The sliding correlator configuration facilitates long-distance measurements with angular spread and delay spread for up to 185 dB of maximum measurable path loss. The real-time spread spectrum mode is shown to support short-range, small-scale temporal, and Doppler measurements (minimum snapshot sampling interval of 32.753 μs) with a substantial dynamic fading range of 40 dB for human blockage and dynamic urban scenarios. The channel sounder uses field programmable gate arrays, analog-to-digital converters, digital-to-analog converters, and low-phase-noise rubidium standard references for frequency/time synchronization and absolute time delay measurements. Using propagation theory, several methods are presented here to calibrate and verify the accuracy of the channel sounder, and an improved diffraction model for human blockage, based on the METIS model but now including directional antenna gains, is developed from measurements using the channel sounder. The mmWave channel sounder described here may be used for accurate spatial and temporal raytracing calibration, to identify individual multipath components, to measure antenna patterns, for constructing spatial profiles of mmWave channels, and for developing statistical channel impulse response models in time and space.
209 citations
TL;DR: This review paper highlights recent advances in the use of OAM multiplexing for high-capacity free-space optical and millimetre-wave communications and discusses different technical challenges as well as potential techniques to mitigate such degrading effects.
Abstract: There is a continuing growth in the demand for data bandwidth, and the multiplexing of multiple independent data streams has the potential to provide the needed data capacity. One technique uses the spatial domain of an electromagnetic (EM) wave, and space division multiplexing (SDM) has become increasingly important for increased transmission capacity and spectral efficiency of a communication system. A subset of SDM is mode division multiplexing (MDM), in which multiple orthogonal beams each on a different mode can be multiplexed. A potential modal basis set to achieve MDM is to use orbital angular momentum (OAM) of EM waves. In such a system, multiple OAM beams each carrying an independent data stream are multiplexed at the transmitter, propagate through a common medium and are demultiplexed at the receiver. As a result, the total capacity and spectral efficiency of the communication system can be multiplied by a factor equal to the number of transmitted OAM modes. Over the past few years, progress has been made in understanding the advantages and limitations of using multiplexed OAM beams for communication systems. In this review paper, we highlight recent advances in the use of OAM multiplexing for high-capacity free-space optical and millimetre-wave communications. We discuss different technical challenges (e.g. atmospheric turbulence and crosstalk) as well as potential techniques to mitigate such degrading effects.This article is part of the themed issue 'Optical orbital angular momentum'.
TL;DR: A field trial in time division duplex downlink conducted on a configurable test bed in a real-world environment for the performance evaluations of orthogonal frequency-division multiplexing (OFDM)-based 5G waveform candidates suggests that f-OFDM outperforms CP- OFDM and W-OF DM in terms of both the spectrum efficiency and robustness in a high SNR regime.
Abstract: Service diversity is expected in the upcoming fifth-generation (5G) cellular networks, which poses great challenges to the underlying waveforms to accommodate heterogeneous service requirements in a flexible way. By dividing the bandwidth into several subbands, each having a different numerology, this paper reports a field trial in time division duplex downlink conducted on a configurable test bed in a real-world environment for the performance evaluations of orthogonal frequency-division multiplexing (OFDM)-based 5G waveform candidates, i.e., cyclically prefixed OFDM (CP-OFDM), windowing OFDM (W-OFDM), and filtered OFDM (f-OFDM), in the presence of mixed numerologies. Field trial results confirm the feasibility of mixed numerologies and reveal the impact of several important system parameters, e.g., guard bandwidth, data bandwidth, signal-to-noise ratio (SNR), and transmit power. The results also suggest that f-OFDM outperforms CP-OFDM and W-OFDM in terms of both the spectrum efficiency and robustness in a high SNR regime, and the gain increases with a higher inter-numerology out-of-band interference. In some specific scenarios, ideal spectrum utilization can be realized by f-OFDM which completely removes the guard band.
TL;DR: It is demonstrated by means of realistic ray-tracing and map based evaluations that positioning accuracies below one meter can be achieved by properly fusing direction and delay related measurements on the network side, even when tracking moving devices.
Abstract: In this article, the prospects and enabling technologies for high-efficiency device positioning and location-aware communications in emerging 5G networks are reviewed. We will first describe some key technical enablers and demonstrate by means of realistic ray-tracing and map based evaluations that positioning accuracies below one meter can be achieved by properly fusing direction and delay related measurements on the network side, even when tracking moving devices. We will then discuss the possibilities and opportunities that such high-efficiency positioning capabilities can offer, not only for location-based services in general, but also for the radio access network itself. In particular, we will demonstrate that geometric location-based beamforming schemes become technically feasible, which can offer substantially reduced reference symbol overhead compared to classic full channel state information (CSI)-based beamforming. At the same time, substantial power savings can be realized in future wideband 5G networks where acquiring full CSI calls for wideband reference signals while location estimation and tracking can, in turn, be accomplished with narrowband pilots.
TL;DR: Simulation results show that the proposed multi-resolution time-delay codebooks could provide sufficient beam gains and are robust over large bandwidth, and the effectiveness of the hierarchical beamforming training is verified.
Abstract: Millimeter-wave (mmWave) and sub-Terahertz (THz) communications are compelling as an enabler for next-generation wireless networks. In this paper, we study mmWave and sub-THz systems with array-of-subarray architecture. To accommodate the ultrabroad bandwidth in the mmWave and sub-THz bands, time-delay phase shifters are introduced in system design. Our goal is to investigate beamforming training with hybrid processing to extract the dominant channel information, which would fully exploit channel characteristics while respecting the nature of circuit hardware. In particular, codebooks based on time-delay phase shifters are defined and structured. Then, two multi-resolution time-delay codebooks are designed through subarray coordination. One is built on adaptation of physical beam directions, and the other relies on dynamic approximation of beam patterns. Also, a low-complexity system implementation with modifications on the time-delay codebooks is studied. Furthermore, based on the proposed codebooks, a hierarchical beamforming training strategy with reduced overhead is developed to enable simultaneous training for multiple users. Simulation results show that the proposed multi-resolution time-delay codebooks could provide sufficient beam gains and are robust over large bandwidth. Also, the effectiveness of the hierarchical beamforming training is verified.
TL;DR: The proposed radar architecture is a reliable solution to overcome the limitations of current radar on operation bandwidth and processing speed, and it is hopefully to be used in future radars for real-time and high-resolution target detection and imaging.
Abstract: Real-time and high-resolution target detection is highly desirable in modern radar applications. Electronic techniques have encountered grave difficulties in the development of such radars, which strictly rely on a large instantaneous bandwidth. In this article, a photonics-based real-time high-range-resolution radar is proposed with optical generation and processing of broadband linear frequency modulation (LFM) signals. A broadband LFM signal is generated in the transmitter by photonic frequency quadrupling, and the received echo is de-chirped to a low frequency signal by photonic frequency mixing. The system can operate at a high frequency and a large bandwidth while enabling real-time processing by low-speed analog-to-digital conversion and digital signal processing. A conceptual radar is established. Real-time processing of an 8-GHz LFM signal is achieved with a sampling rate of 500 MSa/s. Accurate distance measurement is implemented with a maximum error of 4 mm within a range of ~3.5 meters. Detection of two targets is demonstrated with a range-resolution as high as 1.875 cm. We believe the proposed radar architecture is a reliable solution to overcome the limitations of current radar on operation bandwidth and processing speed, and it is hopefully to be used in future radars for real-time and high-resolution target detection and imaging.
TL;DR: In this paper, a comprehensive review concerning the geometry, the manufacturing technologies, the materials, and the numerical techniques, adopted for the analysis and design of wideband and ultrawideband (UWB) antennas for wireless applications, is presented.
Abstract: A comprehensive review concerning the geometry, the manufacturing technologies, the materials, and the numerical techniques, adopted for the analysis and design of wideband and ultrawideband (UWB) antennas for wireless applications, is presented. Planar, printed, dielectric, and wearable antennas, achievable on laminate (rigid and flexible), and textile dielectric substrates are taken into account. The performances of small, low-profile, and dielectric resonator antennas are illustrated paying particular attention to the application areas concerning portable devices (mobile phones, tablets, glasses, laptops, wearable computers, etc.) and radio base stations. This information provides a guidance to the selection of the different antenna geometries in terms of bandwidth, gain, field polarization, time-domain response, dimensions, and materials useful for their realization and integration in modern communication systems.
TL;DR: In this paper, the effect of the design parameters of the harvester on the dynamic response and the effective bandwidth of such devices remains uninvestigated, and an analytical approach to characterize the effective frequency bandwidth of harvesters that possess a hexic potential energy function is established.
TL;DR: This paper proposes a novel decentralized baseband processing architecture that alleviates bottlenecks by partitioning the BS antenna array into clusters, each associated with independent radio-frequency chains, analog and digital modulation circuitry, and computing hardware.
Abstract: Achieving high spectral efficiency in realistic massive multi-user (MU) multiple-input multiple-output (MIMO) wireless systems requires computationally complex algorithms for data detection in the uplink (users transmit to base-station) and beamforming in the downlink (base-station transmits to user). Most existing algorithms are designed to be executed on centralized computing hardware at the base-station (BS), which results in prohibitive complexity for systems with hundreds or thousands of antennas and generates raw baseband data rates that exceed the limits of current interconnect technology and chip I/O interfaces. This paper proposes a novel decentralized baseband processing architecture that alleviates these bottlenecks by partitioning the BS antenna array into clusters, each associated with independent radio-frequency chains, analog and digital modulation circuitry, and computing hardware. For this architecture, we develop novel decentralized data detection and beamforming algorithms that only access local channel-state information and require low communication bandwidth among the clusters. We study the associated tradeoffs between error-rate performance, computational complexity, and interconnect bandwidth, and we demonstrate the scalability of our solutions for massive MU-MIMO systems with thousands of BS antennas using reference implementations on a graphics processing unit (GPU) cluster.
TL;DR: The proposed TRXs are equipped with binary phase shift keying modulators as well as an I/Q receiver and can be utilized to build a flexible software-defined radar platform for range and distant-selective vibration sensors utilizing frequency-modulated continuous wave as wellAs pseudo-random noise radar techniques.
Abstract: This paper describes a multi-purpose radar system suitable for applications with different requirements on dynamic range, resolution, and miniaturization degree. It utilizes a scalable sensor platform that includes a wideband 30.5-GHz voltage-controlled oscillator (VCO) as well as 61- and 122-GHz transceivers (TRXs) in a silicon-germanium BiCMOS technology. The proposed architecture enables the cascading of multiple TRXs and allows the implementation of MIMO radar systems in two different frequency bands by using a single VCO. The higher transmit output power of 11.5 dBm as well as receive gain of 24 dB make the 61-GHz TRX suitable for applications requiring a high dynamic range. The lower wavelength allows the integration of on-chip antennas in the 122-GHz TRX and enables, thus, a high miniaturization degree. The higher LO scaling factor makes the 122-GHz TRX also more attractive for high-resolution applications. A sweep bandwidth of 2.5 GHz generated by the VCO is scaled up to 10 GHz and results in a range resolution of 3 cm. The proposed TRXs are equipped with binary phase shift keying modulators as well as an I/Q receiver and can be utilized to build a flexible software-defined radar platform for range and distant-selective vibration sensors utilizing frequency-modulated continuous wave as well as pseudo-random noise radar techniques.
TL;DR: The developed channel model allows system design engineers to generate realizations of propagation channel efficiently for designing Kiosk-fashion close-proximity communication systems in the THz band.
Abstract: Terahertz (THz) Kiosk application offers ultrahigh downloads of digital information to users’ handheld devices. System configuration and multiple paths between the transmitter and receiver have important impact on the achievable data rates. In this paper, the propagation channel of THz Kiosk downloading application is investigated and a stochastic channel model is proposed. Based on channel measurements using a vector network analyzer, a 3-D ray-tracing simulator is calibrated to conduct simulations for an in-depth analysis of the different channel characteristics. Successively, the observed propagation paths are classified and the key channel parameters in time, frequency, and spatial domains are modeled for each type of ray. The resulting stochastic model is evaluated in terms of Rician K-factor and root mean square delay spread. Compared to the reference data, the mean absolute errors of these two metrics of the three investigated scenarios are less than 1.48 dB and 0.07 ns, respectively. The results show that the target 100 gigabits per second data rate is achievable at tens of gigahertz system bandwidth at proper communication distance and higher order modulation schemes. The developed channel model allows system design engineers to generate realizations of propagation channel efficiently for designing Kiosk-fashion close-proximity communication systems in the THz band.
TL;DR: In this paper, a novel circularly polarized (CP) antenna element based on spiral antenna is proposed, which can achieve 23.0% impedance bandwidth and 21.9% 3-dB axial ratio (AR) bandwidth with a maximum gain of 7.9 dB.
Abstract: A novel circularly polarized (CP) antenna element based on spiral antenna is proposed in this paper. It is differentially fed with an aperture through two vias locating at opposite sides of the aperture. This element can be easily integrated with the low loss substrate integrated waveguide and fabricated with the low cost printed circuit board technology. It can achieve 23.0% impedance bandwidth and 21.9% 3-dB axial ratio (AR) bandwidth with a maximum gain of 7.9 dBic. In order to broaden the AR bandwidth and lower the AR values of the antenna array, sequential rotation is applied to make a 2 × 2 subarray. The subarray covers an impedance bandwidth of 21.3%, with AR values lower than 1.1 dB across the whole impedance matching band. Thereafter, by employing the designed subarray, a 4 × 8 antenna array is composed and fabricated. The measured impedance bandwidth covers 14.1%, from 56.55 to 65.13 GHz, and the measured 3-dB AR bandwidth covers 21.1%, from 55 to 68 GHz. The maximum measured gain is 19.5 dBic. It also demonstrates that the proposed antenna element is a promising candidate to design high gain CP antenna arrays in millimeter-wave band.
TL;DR: With a genetic algorithm, an on-chip TEo- TMo polarization rotator with a footprint of 0.96 μm × 4.2 μm is designed and experimentally demonstrated its conversion loss and extinction ratio in the wavelength range of 1440–1580nm.
Abstract: Polarization control of light waves is an important technique in optical communication and signal processing. On-chip polarization rotation from the fundamental transverse-electric (TE00) mode to the fundamental transverse-magnetic (TM00) mode is usually difficult because of their large effective refractive index difference. Here, we demonstrate an on-chip wideband polarization rotator designed with a genetic algorithm to convert the TE00 mode into the TM00 mode within a footprint of 0.96 μm ×4.2 μm. In simulation, the optimized structure achieves polarization rotation with a minimum conversion loss of 0.7 dB and the 1-dB bandwidth of 157 nm. Experimentally, our fabricated devices have demonstrated the expected polarization rotation with a conversion loss of ∼2.5 dB in the measured wavelength range of 1440–1580 nm, where the smallest value reaches ∼2 dB. The devices can serve as a generic approach and standard module for controlling light polarization in integrated photonic circuitry.
TL;DR: In this paper, the potential benefits of digital nonlinearity compensation (NLC) techniques in fully loaded coherent wavelength-division multiplexed (WDM) transmission systems were explored. And the authors showed that while the BP gain is similar to single-carrier systems, PPRN removal can have a much stronger effect, particularly for higher order QAM systems, implying that SCM can be advantageous not only for constant modulus formats such as QPSK, but also for high spectral efficiency systems.
Abstract: We explore the potential benefits of digital nonlinearity compensation (NLC) techniques in fully loaded coherent wavelength-division multiplexed (WDM) transmission systems. After providing an overview of the various classes of nonlinear interference noise (NLIN) and digital signal processing approaches for their mitigation, we consider the two practically most relevant digital NLC methods known today: back-propagation (BP) and equalization of nonlinear phase and polarization rotation noise (PPRN). We consider a wide range of system configurations including a variety of modulation formats from quadrature phase-shift keying (QPSK) to 256-ary quadrature amplitude modulation (QAM), single-carrier and digital subcarrier multiplexed (SCM) optical superchannels, as well as both point-to-point line systems and optically routed networks (ORNs). Using theoretical predictions from the time-domain model for NLIN, we show that the gain in peak signal-to-noise ratio in fully loaded WDM systems using single-channel and three-channel joint BP is typically limited to 0.5 and 1 dB. The additional gain provided by increasing the number of jointly back-propagated channels beyond three is limited to 0.1 dB per additional back-propagated channel. The remarkably slow growth of the BP gain with the bandwidth of the back-propagated signal is shown to apply also for systems in which the receiver employs PPRN removal. We additionally explore the potential benefits of SCM across a wide range of system configurations, including the impact of BP and PPRN removal on SCM systems. We show that while the BP gain is similar to single-carrier systems, PPRN removal can have a much stronger effect, particularly for higher order QAM systems, implying that SCM can be advantageous not only for constant modulus formats such as QPSK, but also for high spectral efficiency systems. In the context of ORNs, we find that SCM not only improves system tolerance to nonlinearities, but also induces significantly smaller performance variations in various ORN scenarios.
TL;DR: In this paper, the authors presented a compact piezoelectric vibration energy harvester (VEH) using multiple nonlinear techniques to tune the resonant frequency and broadening the bandwidth.
TL;DR: In this article, an effectively single mode tubular antiresonant hollow core fiber with minimum loss of ∼25 dB/km at ∼1200 nm, and an extremely wide low-loss transmission window (lower than 30dB/km loss from 1000 to 1400 nm and 6 dB bandwidth exceeding 1000 nm) was reported.
Abstract: We report an effectively single mode tubular antiresonant hollow core fiber with minimum loss of ∼25 dB/km at ∼1200 nm, and an extremely wide low-loss transmission window (lower than 30 dB/km loss from 1000 to 1400 nm and 6 dB bandwidth exceeding 1000 nm). Despite the relatively large mode field diameter of 32 µm, the fiber can be interfaced to SMF28 to produce fully connectorized samples. Exploiting an excellent modal purity arising from large modal differential loss and low intermodal coupling, we demonstrate penalty-free 10G on–off keying data transmission through 100 m of fiber, at wavelengths of 1065, 1565, and 1963 nm.
TL;DR: Undersampling method is introduced to reduce the sampling rate of the analog-to-digital converter and the data size, which can reduce the cost of the system and facilitate real-time data processing.
Abstract: This paper proposes a novel distributed fiber-optic acoustic sensor, which can solve both the tradeoff between the maximum measurable distance and the spatial resolution, and that between the measurement distance and the vibration response bandwidth. The system is based on frequency-division-multiplexing time-gated digital optical frequency domain reflectometry, which consecutively injects linear-frequency-modulated probe pulses with different frequency ranges. Undersampling method is introduced to reduce the sampling rate of the analog-to-digital converter and the data size, which can reduce the cost of the system and facilitate real-time data processing. In experiments, two simultaneous vibrations with frequency up to 9 kHz are detected over the 24.7-km-long fiber, with a sign-to-noise ratio of 30 dB and spatial resolution of 10 m.
TL;DR: Numerical analysis shows that the analytical results match the simulation results, and the proposed ISBI cancelation and equalization algorithms can significantly improve the system performance in comparison with the existing algorithms.
Abstract: Flexibly supporting multiple services, each with different communication requirements and frame structure, has been identified as one of the most significant and promising characteristics of next generation and beyond wireless communication systems. However, integrating multiple frame structures with different subcarrier spacing in one radio carrier may result in significant inter-service-band-interference (ISBI). In this paper, a framework for multi-service (MS) systems is established based on a subband filtered multi-carrier system. The subband filtering implementations and both asynchronous and generalized synchronous (GS) MS subband filtered multi-carrier (SFMC) systems have been proposed. Based on the GS-MS-SFMC system, the system model with ISBI is derived and a number of properties on ISBI are given. In addition, low-complexity ISBI cancelation algorithms are proposed by precoding the information symbols at the transmitter. For asynchronous MS-SFMC system in the presence of transceiver imperfections, including carrier frequency offset, timing offset, and phase noise, a complete analytical system model is established in terms of desired signal, inter-symbol-interference, inter-carrier-interference, ISBI, and noise. Thereafter, new channel equalization algorithms are proposed by considering the errors and imperfections. Numerical analysis shows that the analytical results match the simulation results, and the proposed ISBI cancelation and equalization algorithms can significantly improve the system performance in comparison with the existing algorithms.
TL;DR: 3-D MIMO channel which fully utilizes the elevation domain does improve capacity and also enhance the contributing eigenvalue number, and in reality, O2I is the most beneficial scenario, then followed by UMi and UMa scenarios.
Abstract: By taking advantage of the elevation domain, three-dimensional (3-D) multiple input and multiple output (MIMO) with massive antenna elements is considered as a promising and practical technique for the fifth Generation mobile communication system. So far, 3-D MIMO is mostly studied by simulation and a few field trials have been launched recently. It still remains unknown how much does the 3-D MIMO meet our expectations in versatile scenarios. In this paper, we answer this based on measurements with $56\times 32$ antenna elements at 3.5 GHz with 100-MHz bandwidth in three typical deployment scenarios, including outdoor to indoor (O2I), urban microcell (UMi), and urban macrocell (UMa). Each scenario contains two different site locations and 2–5 test routes under the same configuration. Based on the measured data, both elevation and azimuth angles are extracted and their stochastic behaviors are investigated. Then, we reconstruct two-dimensional and 3-D MIMO channels based on the measured data, and compare the capacity and eigenvalues distribution. It is observed that 3-D MIMO channel which fully utilizes the elevation domain does improve capacity and also enhance the contributing eigenvalue number. However, this gain varies from scenario to scenario in reality, O2I is the most beneficial scenario, then followed by UMi and UMa scenarios. More results of multiuser capacity varying with the scenario, antenna number and user number can provide the experimental insights for the efficient utilization of 3-D MIMO in future.
TL;DR: In this article, the authors proposed a dual-polarized antenna subarray with filtering responses, which is a multilayered 3D geometry, including a dualpath $1 \times 4$ feeding network and four cavity-backed slot antennas.
Abstract: A $2 \times 2$ dual-polarized antenna subarray with filtering responses is proposed in this paper. This antenna subarray is a multilayered 3-D geometry, including a dual-path $1 \times 4$ feeding network and four cavity-backed slot antennas. The isolation performance between two input ports is greatly improved by a novel method, which only needs to modify several vias in a square resonator. Cavities in the feeding network are properly arranged and coupled using different coupling structures, so that the operation modes in each cavity for different paths can always remain orthogonal, which enables the subarray to exhibit not only filtering functions (in both reflection coefficients and gain responses), but also a low cross-polarization level. A prototype is fabricated with a center frequency of 37 GHz and a bandwidth of 600 MHz for demonstration. Good agreement is achieved between simulation and measurement, for both $S$ -parameter and far-field results. The proposed filtering dual-polarized antenna array is very suitable to be employed as the subarray in millimeter-wave 5G base stations to reduce the complexity and integration loss of such beamforming systems.
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TL;DR: In this paper, a novel distributed dynamic spectrum access algorithm based on deep multi-user reinforcement leaning is proposed to solve the problem of spectrum access for network utility maximization in multichannel wireless networks.
Abstract: We consider the problem of dynamic spectrum access for network utility maximization in multichannel wireless networks. The shared bandwidth is divided into K orthogonal channels. In the beginning of each time slot, each user selects a channel and transmits a packet with a certain transmission probability. After each time slot, each user that has transmitted a packet receives a local observation indicating whether its packet was successfully delivered or not (i.e., ACK signal). The objective is a multi-user strategy for accessing the spectrum that maximizes a certain network utility in a distributed manner without online coordination or message exchanges between users. Obtaining an optimal solution for the spectrum access problem is computationally expensive in general due to the large state space and partial observability of the states. To tackle this problem, we develop a novel distributed dynamic spectrum access algorithm based on deep multi-user reinforcement leaning. Specifically, at each time slot, each user maps its current state to spectrum access actions based on a trained deep-Q network used to maximize the objective function. Game theoretic analysis of the system dynamics is developed for establishing design principles for the implementation of the algorithm. Experimental results demonstrate strong performance of the algorithm.