Although the 5G wireless network has made significant advances,it is not enough to accommodate the rapidly rising requirement for broader bandwidth in post-5G and 6G eras.As a result,emerging technologies in higher fr...Although the 5G wireless network has made significant advances,it is not enough to accommodate the rapidly rising requirement for broader bandwidth in post-5G and 6G eras.As a result,emerging technologies in higher frequencies including visible light communication(VLC),are becoming a hot topic.In particular,LED-based VLC is foreseen as a key enabler for achieving data rates at the Tb/s level in indoor scenarios using multi-color LED arrays with wavelength division multiplexing(WDM)technology.This paper proposes an optimized multi-color LED array chip for high-speed VLC systems.Its long-wavelength GaN-based LED units are remarkably enhanced by V-pit structure in their efficiency,especially in the“yellow gap”region,and it achieves significant improvement in data rate compared with earlier research.This work investigates the V-pit structure and tries to provide insight by introducing a new equivalent circuit model,which provides an explanation of the simulation and experiment results.In the final test using a laboratory communication system,the data rates of eight channels from short to long wavelength are 3.91 Gb/s,3.77 Gb/s,3.67 Gb/s,4.40 Gb/s,3.78 Gb/s,3.18 Gb/s,4.31 Gb/s,and 4.35 Gb/s(31.38 Gb/s in total),with advanced digital signal processing(DSP)techniques including digital equalization technique and bit-power loading discrete multitone(DMT)modulation format.展开更多
This paper presents a wide-bandwidth back-illuminated modified uni-traveling-carrier photodiode(MUTC-PD)packaged with standard WR-5 rectangular waveguide for high-speed wireless communications.With optimized epitaxy s...This paper presents a wide-bandwidth back-illuminated modified uni-traveling-carrier photodiode(MUTC-PD)packaged with standard WR-5 rectangular waveguide for high-speed wireless communications.With optimized epitaxy structure and coplanar waveguide electrodes,the fabricated 4-μm-diameter PD exhibits ultra-flat frequency response and high saturation power.Integrated passive circuits including low-loss bias-tee and E-plane probe are designed to package the PD into a compact module with waveguide output.The packaged PD module has demonstrated a flat frequency response with fluctuations within±2.75 d B over a broadband of 140–220 GHz and a high saturated output power of-7.8 d Bm(166μW)at 140 GHz.For wireless communication applications,the packaged PD is used to implement 1-m free space transmission at carrier frequencies of 150.5 and 210.5 GHz,with transmission rates of 75 and 90 Gbps,respectively.展开更多
This paper proposes a wildfire monitoring and detection system based on wireless sensor network. This system detects fire by monitoring surrounding temperature, humidity and smoke. Once fire is detected, a warning mes...This paper proposes a wildfire monitoring and detection system based on wireless sensor network. This system detects fire by monitoring surrounding temperature, humidity and smoke. Once fire is detected, a warning message containing probable location of that fire is immediately sent to the responsible authority over cellular network. In order for the system to be more effective, communities living near forests or national parks can send warning messages through the same system to the responsible authority using their mobile handsets once they witness wildfire or illegal activities. For the system to be fully functional, the only requirement is the availability of cellular network coverage in forests or national parks to enable short message services to take place. The system prototype is developed using Arduino microcontroller, several sensors to detect temperature, relative humidity and smoke as well as wireless network connection modules. At the control center Telerivet messaging platform is used to design the messaging service. The experimental results justify the capability of the proposed system in detecting wildfire in real time.展开更多
Reducing maternal and infant deaths’ rates in the developing countries, particularly in sub-Sahara Africa, remain a big challenge. Despite efforts by governments, the reductions have been unsatisfactory. To accelerat...Reducing maternal and infant deaths’ rates in the developing countries, particularly in sub-Sahara Africa, remain a big challenge. Despite efforts by governments, the reductions have been unsatisfactory. To accelerate the reduction in maternal and infant deaths, m-health has been proposed as a viable, economical and effective intervention, able to reach the low income and disadvantaged groups. Mobile phone-based applications are among the m-health interventions that have been found to have positive outcomes for different healthcare challenges, such as improving clinical attendance and skilled delivery, and reducing perinatal mortality. However, the adoption of smartphone-based applications for health in Tanzania has been slow. Some of the likely contributing factors might be low technology exposure by the majority of the population and English language skills’ limitations. In this work, we developed a mobile application for providing interactive support to users, thus complementing other solutions available such as SMS and other smartphone apps. The main advantage of this app is the presence of interactive features that enable patient-provider communication. We adopted the Rapid application development (RAD) model for developing the application. We used UML modeling language tools for designing the application. The mobile application’s technical architecture uses various technologies and system development tools such as PHP programming language for the web application, MySQL database management system and Android Studio mobile application development platform.展开更多
We proposed a method to evaluate the material dispersion of the dielectric film in dielectriccoated silver hollow fiber.By taking into consideration the derived material dispersion,the wavelengths of the loss peaks an...We proposed a method to evaluate the material dispersion of the dielectric film in dielectriccoated silver hollow fiber.By taking into consideration the derived material dispersion,the wavelengths of the loss peaks and valleys in the loss spectra of the hollow fiber can be predicted more accurately.Then,we fabricated the dielectric-coated silver hollow fiber according to the parameters obtained by using the improved design method.The measured data showed good agreement with the calculated results.The loss for medical laser of Er:YAG and CO_(2)was less than 0.3 dB/m.The loss for green or red pilot beams was around 5 dB/m,which is sufficiently low for the purpose of pilot beam transmission.The derived material dispersion plays an important role in the design and fabrication of the hollow fiber for multiwavelength delivery.展开更多
Optical monitoring of object position and alignment with nanoscale precision is critical for ultra-precision measurement applications,such as micro/nano-fabrication,weak force sensing,and micro-scopic imaging.Traditio...Optical monitoring of object position and alignment with nanoscale precision is critical for ultra-precision measurement applications,such as micro/nano-fabrication,weak force sensing,and micro-scopic imaging.Traditional optical nanometry methods often rely on precision nanostructure fabrication,multi-beam interferometry,or complex post-processing algorithms,which can limit their practical use.In this study,we introduced a simplified and robust quantum measurement technique with an achievable resolution of 2.2 pm and an experimental demonstration of 1 nm resolution,distinguishing it from conventional interferometry,which depended on multiple reference beams.We designed a metasurface substrate with a mode-conversion function,in which an incident Gaussian beam is converted into higher-order transverse electromagnetic mode(TEM)modes.A theoretical analysis,including calculations of the Fisher information,demonstrated that the accuracy was maintained for nanoscale displacements.In conclusion,the study findings provide a new approach for precise alignment and metrology of nanofabrication and other advanced applications.展开更多
In this paper, we propose and experimentally demonstrate a bi-directional indoor communication system based on visible light RGB-LED. Spectrally efficient modulation formats （QAM-OFDM）, advanced digital signal proce...In this paper, we propose and experimentally demonstrate a bi-directional indoor communication system based on visible light RGB-LED. Spectrally efficient modulation formats （QAM-OFDM）, advanced digital signal processing, pre- and post- equalization are adopted to compensate the severe frequency response of indoor channel. In this system, we utilize red-green-blue Light emitting diodes （LEDs）, of which each color can be used to carry different signals. For downlink, the low frequencies of each color are used while for uplink, the high frequencies are used. The overall data rate of downlink and uplink are 1.15-Gb/s and 300-Mb/s. The bit error ratios （BERs） for all channels after 0.7 m indoor delivery are below pre-forward- error-correction （pre-FEC） threshold of 3.8×10-3. To the best of our knowledge, this is the highest data rate in bi-directional visible light communication system.展开更多
Hybrid beamforming(HBF)has become an attractive and important technology in massive multiple-input multiple-output(MIMO)millimeter-wave(mmWave)systems.There are different hybrid architectures in HBF depending on diffe...Hybrid beamforming(HBF)has become an attractive and important technology in massive multiple-input multiple-output(MIMO)millimeter-wave(mmWave)systems.There are different hybrid architectures in HBF depending on different connection strategies of the phase shifter network between antennas and radio frequency chains.This paper investigates HBF optimization with different hybrid architectures in broadband point-to-point mmWave MIMO systems.The joint hybrid architecture and beamforming optimization problem is divided into two sub-problems.First,we transform the spectral efficiency maximization problem into an equivalent weighted mean squared error minimization problem,and propose an algorithm based on the manifold optimization method for the hybrid beamformer with a fixed hybrid architecture.The overlapped subarray architecture which balances well between hardware costs and system performance is investigated.We further propose an algorithm to dynamically partition antenna subarrays and combine it with the HBF optimization algorithm.Simulation results are presented to demonstrate the performance improvement of our proposed algorithms.展开更多
High maternal and child deaths in developing countries are frequently linked to poor health services provided to pregnant women and children. To improve the quality of maternal, neonatal and child health (MNCH) servic...High maternal and child deaths in developing countries are frequently linked to poor health services provided to pregnant women and children. To improve the quality of maternal, neonatal and child health (MNCH) services, the government and other stakeholders in MNCH emphasize the importance of quality assessment. However, effective quality assessment approaches are mostly lacking in most developing countries, particularly in Tanzania. This study, therefore, aimed at developing a quality assessment approach that can effectively assess and report on the quality of MNCH services. Due to the need for a good quality assessment approach that suits a resource-constrained environment, machine learning-based approach was proposed and developed. K-means algorithm was used to develop a clustering model that groups MNCH data and performs cluster summarization to discover the knowledge portrayed in each group on the quality of MNCH services. Results confirmed the clustering model’s ability to assign the data points into appropriate clusters;cluster analysis with the collaboration of MNCH experts successfully discovered insights on the quality of services portrayed by each group.展开更多
This paper reports the developed mobile application through the use of advanced technologies such as mobile computing, cloud computing and Global Positioning System (GPS) in order to solve the challenges. The purpose ...This paper reports the developed mobile application through the use of advanced technologies such as mobile computing, cloud computing and Global Positioning System (GPS) in order to solve the challenges. The purpose of this study is to find out how the recent advances and mass adoption of ICT by the public can best be leveraged to enhance the performance of Civil Society Organizations (CSOs) in East Africa. The data collection techniques used are through questionnaires, observations and conducting interviews with different stakeholders in the civil society arena i.e., the donors, the CSOs and the people in society that are given a voice by civil societies. In the system development phase, agile development methodology was used. Analysis of the data collected showed that there is a gap in the availability of a single or a centralized platform which can be easily accessed, user-friendly and reliable where different actors can readily get reliable and up-to-date information about the available CSOs they are interested in. To address this problem, an interactive online directory of CSOs has been developed. The platform is mobile based and enables CSOs to register and fill up their current details, thus ensuring that there is always correct and updated information. The platform is equipped with, among other features, a geo-mapping facility which enables users of the system to correctly geo-locate their civil societies of interest on a map view. The results of system evaluation showed that 88.125% of users were satisfied with the system basing on the evaluation criteria.展开更多
Single-pixel imaging(SPI)is a prominent scattering media imaging technique that allows image transmission via one-dimensional detection under structured illumination,with applications spanning from long-range imaging ...Single-pixel imaging(SPI)is a prominent scattering media imaging technique that allows image transmission via one-dimensional detection under structured illumination,with applications spanning from long-range imaging to microscopy.Recent advancements leveraging deep learning(DL)have significantly improved SPI performance,especially at low compression ratios.However,most DL-based SPI methods proposed so far rely heavily on extensive labeled datasets for supervised training,which are often impractical in real-world scenarios.Here,we propose an unsupervised learningenabled label-free SPI method for resilient information transmission through unknown dynamic scattering media.Additionally,we introduce a physics-informed autoencoder framework to optimize encoding schemes,further enhancing image quality at low compression ratios.Simulation and experimental results demonstrate that high-efficiency data transmission with structural similarity exceeding 0.9 is achieved through challenging turbulent channels.Moreover,experiments demonstrate that in a 5 m underwater dynamic turbulent channel,USAF target imaging quality surpasses traditional methods by over 13 dB.The compressive encoded transmission of 720×720 resolution video exceeding 30 seconds with great fidelity is also successfully demonstrated.These preliminary results suggest that our proposed method opens up a new paradigm for resilient information transmission through unknown dynamic scattering media and holds potential for broader applications within many other scattering media imaging technologies.展开更多
We demonstrated a fiber-terahertz(THz)-fiber communication system at the D-band based on full photonic conversions,exploiting a modified unitraveling-carrier photodiode(MUTC-PD)module to achieve optical-to-THz convers...We demonstrated a fiber-terahertz(THz)-fiber communication system at the D-band based on full photonic conversions,exploiting a modified unitraveling-carrier photodiode(MUTC-PD)module to achieve optical-to-THz conversion at the transmitter end and an ultrabroadband packaged thin-film lithium niobate Mach-Zehnder modulator(MZM)to convert the THz signal to the optical signal at the receiver end.This system successfully realized the transmission of 33-Gbaud 16-quadrature amplitude modulation(QAM)and 31-Gbaud probabilistic shaping-64-QAM signals through 10-km standard singlemode fiber(SSMF),0.6-m wireless distance,and the subsequent 5-km SSMF,achieving net data rates of 116.03 and123.72 Gbps,respectively.展开更多
With the rapid development of the light-emitting diode （LED） industry, interest in visible light communication （VLC） is growing. The limited bandwidth of commercial LEDs is one of the main challenges to achieve hi...With the rapid development of the light-emitting diode （LED） industry, interest in visible light communication （VLC） is growing. The limited bandwidth of commercial LEDs is one of the main challenges to achieve high- speed VLC. In this Letter, a kind of bandwidth-efficient VLC system based on carrierless amplitude and phase （CAP） modulation is proposed, where a simple differential faster-than-Nyquist （FTN） pre-coding scheme is em- ployed to compress the spectrum and further improve the overall system baud rate. The system is experimentally demonstrated with a data rate of 1.47-Cb/s over 1.5 m free space transmission. The results indicate that an improvement of 80 Mbaud is achieved by FTN-CAP4 at 20% subband overlap and 40 Mbaud rate improvement by FTN-CAP16 at 7.5% subband overlap. Compared with traditional CAP, the FTN pre-coded CAP shows a better performance in spectral efficiency （SE） and intercarrier interference resistance. To the best of our knowl- edge, it is the first time to employ FTN pre-coded CAP in indoor high-data-rate VLC systems.展开更多
Light-emitting diode(LED)-based visible light communication(VLC) has become a potential candidate for nextgeneration ultra-high-speed indoor wireless communication. In this paper, four special-shaped 8-quadrature ampl...Light-emitting diode(LED)-based visible light communication(VLC) has become a potential candidate for nextgeneration ultra-high-speed indoor wireless communication. In this paper, four special-shaped 8-quadrature amplitude modulation(QAM) constellations are investigated in a single-carrier VLC system. It is numerically verified and experimentally demonstrated that circular(7,1) shows obvious superiority in the performance of the dynamic range of signal voltage peak-to-peak(vpp) value and bit error rate(BER). Next best is rectangular, followed by triangular; circular(4,4) has the worst performance. A data rate of 1.515 Gbit/s is successfully achieved by circular(7,1) employing a red chip LED over 0.5 m indoor free space transmission below a BER threshold of3.8 × 10^(-3). Compared with circular(4,4), the traditional 8-QAM constellation, circular(7,1) provides a wider dynamic range of signal vpp, a higher data rate, and a longer transmission distance. To the best of our knowledge,this is the first investigation into the performance differences of special-shaped 8-QAM constellations in a highspeed, single-carrier VLC system, and the results comprehensively demonstrate that circular(7,1) is the optimal option.展开更多
A novel scheme to generate, transmit, and receive an optical orthogonal frequency division multiplexing （OFDM） continuous phase modulation （CPM） signal, which is combining minimum shift keying （MSK） coding with ...A novel scheme to generate, transmit, and receive an optical orthogonal frequency division multiplexing （OFDM） continuous phase modulation （CPM） signal, which is combining minimum shift keying （MSK） coding with OFDM optical modulation, for downlink application in a 4×2.5-Gb/s wavelength division multiplexing （WDM） passive optical access network, is proposed and experimentally validated. We also realize wavelength remodulation for carrying upstream on-off keying （OOK） data to reduce the cost budget at the optical network unit. The experimental results show that the power penalties for the downlink and the uplink data after transmission over 25-km SMF-28 fiber are 0.1 dB and smaller than 0.4 dB, respectively.展开更多
In this Letter, we propose a novel constellation-shaping carrier-less amplitude and phase （CAP） modulation scheme to alleviate the systematic nonlinearity in visible light communication （VLC） systems. A simple geo...In this Letter, we propose a novel constellation-shaping carrier-less amplitude and phase （CAP） modulation scheme to alleviate the systematic nonlinearity in visible light communication （VLC） systems. A simple geo- metric transformation shaping method is employed to convert the normal square lattice constellation into multi- ple circular constellations. The feasibility and performance are investigated and experimentally demonstrated by a 1.25 Gb/s CAP-modulated VLC system. The results indicate that the circular constellation has better resis- tance to systematic nonlinearity compared with a rectangular constellation. The dynamic range of input signal peak-to-peak values promotes 20% at a low bias voltage nonlinear area and 50% at a high bias voltage nonlinear area. To the best of our knowledge, this is the first time constellation-shaping CAP has ever been reported in indoor high data rate VLC systems.展开更多
Asymmetrically clipped optical orthogonal frequency division multiplexing(ACO-OFDM)has been a promising candidate in visible light communications(VLC)due to its improvement in power efficiency and reduction of nonline...Asymmetrically clipped optical orthogonal frequency division multiplexing(ACO-OFDM)has been a promising candidate in visible light communications(VLC)due to its improvement in power efficiency and reduction of nonlinearity based on previous simulation analysis.In this paper,for the first time as far as we know,we experimentally verify that ACO-OFDM would be an efficient scheme to improve the performance of a gigabit wavelength division multiplexing VLC system.Our theoretical investigations reveal that the advantages of ACO-OFDM can be attributed to the reduction of inter-carrier interference caused by signal–signal beating noise.An aggregate data rate of 1.05 Gb∕s is successfully achieved over 30 cm transmission below the 7%forwarderror-correction threshold of 3.8×10−3.The experimental results show that ACO-OFDM can outperform DC-biased optical OFDM by BER performance of 1.5 dB at the same data rate and 4 dB at the same bandwidth,which clearly demonstrates the benefit and feasibility of ACO-OFDM.展开更多
The generation of coherent optical subcarriers based on a concatenated dual-drive Mach-Zehnder intensity modulator （IM） and two phase modulators （PMs） is proposed and experimentally demonstrated. The modulation in...The generation of coherent optical subcarriers based on a concatenated dual-drive Mach-Zehnder intensity modulator （IM） and two phase modulators （PMs） is proposed and experimentally demonstrated. The modulation index and DC bias of PM＋IM modulation are theoretically investigated. Theoretical analysis and numerical study are also carried out to examine the proposed scheme. We use 25-GHz RF synchronous sinusoidal signals to drive cascaded two-stage PMs and IM, through which we generate 28 subcaxriers with peak power fluctuations less than 4 dB. The measured tone-to-noise ratio of the subcarrier is higher than 40 dB. The experimental results show that for 100-Gb/s polarization multiplexing QPSK signal, the receiver sensitivity of the back-to-back signal is -28.6 dBm, and the power penalty is lower than 1 dB after 100-km transmission at the BER of 1 × 10-9.展开更多
Novel optical offset quadrature phase shift keying （OQPSK） and improved minimum-shift keying （MSK） modulation schemes to smooth optical phase hopping for high speed fiber optics transmission are proposed. Simulati...Novel optical offset quadrature phase shift keying （OQPSK） and improved minimum-shift keying （MSK） modulation schemes to smooth optical phase hopping for high speed fiber optics transmission are proposed. Simulations have been done among the MSK, OQPSK, quadrature phase shift keying （QPSK）, and binary phase-shift keying （BPSK） modulation formats at 40 Gb/s over 100-km transmission link using coherent detection. Simulation results present good performances to elevate chromatic dispersion tolerance and reduce the influence of nonlinear effects by adopting the smooth phase modulation formats. Inter-symbol interference decreases for the fast side-lobe property and tight spectrum as a result of avoding the π phase shift and reducing envelop fluctuation.展开更多
We propose an encryption technique for underwater visible light communication[UVLC]based on chaotic phase scrambling[PS]and conjugate frequency hopping[CFH].The technique is experimentally tested using an 8-level puls...We propose an encryption technique for underwater visible light communication[UVLC]based on chaotic phase scrambling[PS]and conjugate frequency hopping[CFH].The technique is experimentally tested using an 8-level pulse amplitude modulation[PAM-8]and a 1.2 m underwater link.The security key of the phase scrambling code is generated according to a logistic map,and the frequency hopping is achieved by adding the same zero frequency points to the signal spectrum.The maximum transmission rate of 2.1 Gbit/s is measured with bit-error-rate[BER]below 7%the hard-decision forward error correction[HD-FEC]threshold of 3.8×10^(-3).展开更多
基金This research was funded by the National Key Research and Development Program of China(2022YFB2802803)the Natural Science Foundation of China Project(No.61925104,No.62031011,No.62201157,No.62074072).
文摘Although the 5G wireless network has made significant advances,it is not enough to accommodate the rapidly rising requirement for broader bandwidth in post-5G and 6G eras.As a result,emerging technologies in higher frequencies including visible light communication(VLC),are becoming a hot topic.In particular,LED-based VLC is foreseen as a key enabler for achieving data rates at the Tb/s level in indoor scenarios using multi-color LED arrays with wavelength division multiplexing(WDM)technology.This paper proposes an optimized multi-color LED array chip for high-speed VLC systems.Its long-wavelength GaN-based LED units are remarkably enhanced by V-pit structure in their efficiency,especially in the“yellow gap”region,and it achieves significant improvement in data rate compared with earlier research.This work investigates the V-pit structure and tries to provide insight by introducing a new equivalent circuit model,which provides an explanation of the simulation and experiment results.In the final test using a laboratory communication system,the data rates of eight channels from short to long wavelength are 3.91 Gb/s,3.77 Gb/s,3.67 Gb/s,4.40 Gb/s,3.78 Gb/s,3.18 Gb/s,4.31 Gb/s,and 4.35 Gb/s(31.38 Gb/s in total),with advanced digital signal processing(DSP)techniques including digital equalization technique and bit-power loading discrete multitone(DMT)modulation format.
基金supported in part by National Key Research and Development Program of China(No.2022YFB2803002)National Natural Science Foundation of China(Nos.62235005,62127814,62225405,61975093,61927811,61991443,61925104 and 61974080)Collaborative Innovation Centre of Solid-State Lighting and Energy-Saving Electronics.
文摘This paper presents a wide-bandwidth back-illuminated modified uni-traveling-carrier photodiode(MUTC-PD)packaged with standard WR-5 rectangular waveguide for high-speed wireless communications.With optimized epitaxy structure and coplanar waveguide electrodes,the fabricated 4-μm-diameter PD exhibits ultra-flat frequency response and high saturation power.Integrated passive circuits including low-loss bias-tee and E-plane probe are designed to package the PD into a compact module with waveguide output.The packaged PD module has demonstrated a flat frequency response with fluctuations within±2.75 d B over a broadband of 140–220 GHz and a high saturated output power of-7.8 d Bm(166μW)at 140 GHz.For wireless communication applications,the packaged PD is used to implement 1-m free space transmission at carrier frequencies of 150.5 and 210.5 GHz,with transmission rates of 75 and 90 Gbps,respectively.
文摘This paper proposes a wildfire monitoring and detection system based on wireless sensor network. This system detects fire by monitoring surrounding temperature, humidity and smoke. Once fire is detected, a warning message containing probable location of that fire is immediately sent to the responsible authority over cellular network. In order for the system to be more effective, communities living near forests or national parks can send warning messages through the same system to the responsible authority using their mobile handsets once they witness wildfire or illegal activities. For the system to be fully functional, the only requirement is the availability of cellular network coverage in forests or national parks to enable short message services to take place. The system prototype is developed using Arduino microcontroller, several sensors to detect temperature, relative humidity and smoke as well as wireless network connection modules. At the control center Telerivet messaging platform is used to design the messaging service. The experimental results justify the capability of the proposed system in detecting wildfire in real time.
文摘Reducing maternal and infant deaths’ rates in the developing countries, particularly in sub-Sahara Africa, remain a big challenge. Despite efforts by governments, the reductions have been unsatisfactory. To accelerate the reduction in maternal and infant deaths, m-health has been proposed as a viable, economical and effective intervention, able to reach the low income and disadvantaged groups. Mobile phone-based applications are among the m-health interventions that have been found to have positive outcomes for different healthcare challenges, such as improving clinical attendance and skilled delivery, and reducing perinatal mortality. However, the adoption of smartphone-based applications for health in Tanzania has been slow. Some of the likely contributing factors might be low technology exposure by the majority of the population and English language skills’ limitations. In this work, we developed a mobile application for providing interactive support to users, thus complementing other solutions available such as SMS and other smartphone apps. The main advantage of this app is the presence of interactive features that enable patient-provider communication. We adopted the Rapid application development (RAD) model for developing the application. We used UML modeling language tools for designing the application. The mobile application’s technical architecture uses various technologies and system development tools such as PHP programming language for the web application, MySQL database management system and Android Studio mobile application development platform.
基金supported by the Shanghai Pujiang Program(7pj14012)the National Nature Science Foundation of China(60608013).
文摘We proposed a method to evaluate the material dispersion of the dielectric film in dielectriccoated silver hollow fiber.By taking into consideration the derived material dispersion,the wavelengths of the loss peaks and valleys in the loss spectra of the hollow fiber can be predicted more accurately.Then,we fabricated the dielectric-coated silver hollow fiber according to the parameters obtained by using the improved design method.The measured data showed good agreement with the calculated results.The loss for medical laser of Er:YAG and CO_(2)was less than 0.3 dB/m.The loss for green or red pilot beams was around 5 dB/m,which is sufficiently low for the purpose of pilot beam transmission.The derived material dispersion plays an important role in the design and fabrication of the hollow fiber for multiwavelength delivery.
基金supported by the West Light Project,CAS(xbzg-zdsys-202206)the National Key Research and Development Program of China(2021YFA1401003)+1 种基金the National Natural Science Foundation of China(NSFC)(62222513,U24A6010,and U24A20317)the Sichuan Engineering Research Center of Digital Materials.
文摘Optical monitoring of object position and alignment with nanoscale precision is critical for ultra-precision measurement applications,such as micro/nano-fabrication,weak force sensing,and micro-scopic imaging.Traditional optical nanometry methods often rely on precision nanostructure fabrication,multi-beam interferometry,or complex post-processing algorithms,which can limit their practical use.In this study,we introduced a simplified and robust quantum measurement technique with an achievable resolution of 2.2 pm and an experimental demonstration of 1 nm resolution,distinguishing it from conventional interferometry,which depended on multiple reference beams.We designed a metasurface substrate with a mode-conversion function,in which an incident Gaussian beam is converted into higher-order transverse electromagnetic mode(TEM)modes.A theoretical analysis,including calculations of the Fisher information,demonstrated that the accuracy was maintained for nanoscale displacements.In conclusion,the study findings provide a new approach for precise alignment and metrology of nanofabrication and other advanced applications.
基金supported by the NNSF of China(No.61177071, No.61250018)the Key Program of Shanghai Science and Technology Association (12dz1143000)
文摘In this paper, we propose and experimentally demonstrate a bi-directional indoor communication system based on visible light RGB-LED. Spectrally efficient modulation formats （QAM-OFDM）, advanced digital signal processing, pre- and post- equalization are adopted to compensate the severe frequency response of indoor channel. In this system, we utilize red-green-blue Light emitting diodes （LEDs）, of which each color can be used to carry different signals. For downlink, the low frequencies of each color are used while for uplink, the high frequencies are used. The overall data rate of downlink and uplink are 1.15-Gb/s and 300-Mb/s. The bit error ratios （BERs） for all channels after 0.7 m indoor delivery are below pre-forward- error-correction （pre-FEC） threshold of 3.8×10-3. To the best of our knowledge, this is the highest data rate in bi-directional visible light communication system.
基金supported by ZTE Industry-University-Institute Cooperation Funds,the Natural Science Foundation of Shanghai under Grant No.23ZR1407300the National Natural Science Foundation of China un⁃der Grant No.61771147.
文摘Hybrid beamforming(HBF)has become an attractive and important technology in massive multiple-input multiple-output(MIMO)millimeter-wave(mmWave)systems.There are different hybrid architectures in HBF depending on different connection strategies of the phase shifter network between antennas and radio frequency chains.This paper investigates HBF optimization with different hybrid architectures in broadband point-to-point mmWave MIMO systems.The joint hybrid architecture and beamforming optimization problem is divided into two sub-problems.First,we transform the spectral efficiency maximization problem into an equivalent weighted mean squared error minimization problem,and propose an algorithm based on the manifold optimization method for the hybrid beamformer with a fixed hybrid architecture.The overlapped subarray architecture which balances well between hardware costs and system performance is investigated.We further propose an algorithm to dynamically partition antenna subarrays and combine it with the HBF optimization algorithm.Simulation results are presented to demonstrate the performance improvement of our proposed algorithms.
文摘High maternal and child deaths in developing countries are frequently linked to poor health services provided to pregnant women and children. To improve the quality of maternal, neonatal and child health (MNCH) services, the government and other stakeholders in MNCH emphasize the importance of quality assessment. However, effective quality assessment approaches are mostly lacking in most developing countries, particularly in Tanzania. This study, therefore, aimed at developing a quality assessment approach that can effectively assess and report on the quality of MNCH services. Due to the need for a good quality assessment approach that suits a resource-constrained environment, machine learning-based approach was proposed and developed. K-means algorithm was used to develop a clustering model that groups MNCH data and performs cluster summarization to discover the knowledge portrayed in each group on the quality of MNCH services. Results confirmed the clustering model’s ability to assign the data points into appropriate clusters;cluster analysis with the collaboration of MNCH experts successfully discovered insights on the quality of services portrayed by each group.
文摘This paper reports the developed mobile application through the use of advanced technologies such as mobile computing, cloud computing and Global Positioning System (GPS) in order to solve the challenges. The purpose of this study is to find out how the recent advances and mass adoption of ICT by the public can best be leveraged to enhance the performance of Civil Society Organizations (CSOs) in East Africa. The data collection techniques used are through questionnaires, observations and conducting interviews with different stakeholders in the civil society arena i.e., the donors, the CSOs and the people in society that are given a voice by civil societies. In the system development phase, agile development methodology was used. Analysis of the data collected showed that there is a gap in the availability of a single or a centralized platform which can be easily accessed, user-friendly and reliable where different actors can readily get reliable and up-to-date information about the available CSOs they are interested in. To address this problem, an interactive online directory of CSOs has been developed. The platform is mobile based and enables CSOs to register and fill up their current details, thus ensuring that there is always correct and updated information. The platform is equipped with, among other features, a geo-mapping facility which enables users of the system to correctly geo-locate their civil societies of interest on a map view. The results of system evaluation showed that 88.125% of users were satisfied with the system basing on the evaluation criteria.
基金supported by the Natural Science Foundation of China Project(No.62525102).
文摘Single-pixel imaging(SPI)is a prominent scattering media imaging technique that allows image transmission via one-dimensional detection under structured illumination,with applications spanning from long-range imaging to microscopy.Recent advancements leveraging deep learning(DL)have significantly improved SPI performance,especially at low compression ratios.However,most DL-based SPI methods proposed so far rely heavily on extensive labeled datasets for supervised training,which are often impractical in real-world scenarios.Here,we propose an unsupervised learningenabled label-free SPI method for resilient information transmission through unknown dynamic scattering media.Additionally,we introduce a physics-informed autoencoder framework to optimize encoding schemes,further enhancing image quality at low compression ratios.Simulation and experimental results demonstrate that high-efficiency data transmission with structural similarity exceeding 0.9 is achieved through challenging turbulent channels.Moreover,experiments demonstrate that in a 5 m underwater dynamic turbulent channel,USAF target imaging quality surpasses traditional methods by over 13 dB.The compressive encoded transmission of 720×720 resolution video exceeding 30 seconds with great fidelity is also successfully demonstrated.These preliminary results suggest that our proposed method opens up a new paradigm for resilient information transmission through unknown dynamic scattering media and holds potential for broader applications within many other scattering media imaging technologies.
基金supported by the National Key Research and Development Program of China(No.2022YFB2903600)the National Natural Science Foundation of China(Nos.62235005,62171137,and 61925104)。
文摘We demonstrated a fiber-terahertz(THz)-fiber communication system at the D-band based on full photonic conversions,exploiting a modified unitraveling-carrier photodiode(MUTC-PD)module to achieve optical-to-THz conversion at the transmitter end and an ultrabroadband packaged thin-film lithium niobate Mach-Zehnder modulator(MZM)to convert the THz signal to the optical signal at the receiver end.This system successfully realized the transmission of 33-Gbaud 16-quadrature amplitude modulation(QAM)and 31-Gbaud probabilistic shaping-64-QAM signals through 10-km standard singlemode fiber(SSMF),0.6-m wireless distance,and the subsequent 5-km SSMF,achieving net data rates of 116.03 and123.72 Gbps,respectively.
基金supported by the National Science Foundation of China(No.61571133)Key Project of Guangdong Province of China(No.2015B010113001)
文摘With the rapid development of the light-emitting diode （LED） industry, interest in visible light communication （VLC） is growing. The limited bandwidth of commercial LEDs is one of the main challenges to achieve high- speed VLC. In this Letter, a kind of bandwidth-efficient VLC system based on carrierless amplitude and phase （CAP） modulation is proposed, where a simple differential faster-than-Nyquist （FTN） pre-coding scheme is em- ployed to compress the spectrum and further improve the overall system baud rate. The system is experimentally demonstrated with a data rate of 1.47-Cb/s over 1.5 m free space transmission. The results indicate that an improvement of 80 Mbaud is achieved by FTN-CAP4 at 20% subband overlap and 40 Mbaud rate improvement by FTN-CAP16 at 7.5% subband overlap. Compared with traditional CAP, the FTN pre-coded CAP shows a better performance in spectral efficiency （SE） and intercarrier interference resistance. To the best of our knowl- edge, it is the first time to employ FTN pre-coded CAP in indoor high-data-rate VLC systems.
基金National Natural Science Foundation of China(NSFC)(61571133)National"863"Program of China(2015AA016904)
文摘Light-emitting diode(LED)-based visible light communication(VLC) has become a potential candidate for nextgeneration ultra-high-speed indoor wireless communication. In this paper, four special-shaped 8-quadrature amplitude modulation(QAM) constellations are investigated in a single-carrier VLC system. It is numerically verified and experimentally demonstrated that circular(7,1) shows obvious superiority in the performance of the dynamic range of signal voltage peak-to-peak(vpp) value and bit error rate(BER). Next best is rectangular, followed by triangular; circular(4,4) has the worst performance. A data rate of 1.515 Gbit/s is successfully achieved by circular(7,1) employing a red chip LED over 0.5 m indoor free space transmission below a BER threshold of3.8 × 10^(-3). Compared with circular(4,4), the traditional 8-QAM constellation, circular(7,1) provides a wider dynamic range of signal vpp, a higher data rate, and a longer transmission distance. To the best of our knowledge,this is the first investigation into the performance differences of special-shaped 8-QAM constellations in a highspeed, single-carrier VLC system, and the results comprehensively demonstrate that circular(7,1) is the optimal option.
基金supported by the National"973" Program of China (No. 2010CB328300)the National Natural Science Foundation of China (Nos.600837004 and 60777010)+3 种基金the National "863" Program of China (Nos. 2009AA01Z253 and 2009AA01A347)the Chinese Postdoctoral Science Foundation (No.20090460593)the Shanghai Postdoctoral Science Foundation (No. 10R21411600)the Open Fund of Beijing University of Posts and Telecommunications, and the Shuguang Fund
文摘A novel scheme to generate, transmit, and receive an optical orthogonal frequency division multiplexing （OFDM） continuous phase modulation （CPM） signal, which is combining minimum shift keying （MSK） coding with OFDM optical modulation, for downlink application in a 4×2.5-Gb/s wavelength division multiplexing （WDM） passive optical access network, is proposed and experimentally validated. We also realize wavelength remodulation for carrying upstream on-off keying （OOK） data to reduce the cost budget at the optical network unit. The experimental results show that the power penalties for the downlink and the uplink data after transmission over 25-km SMF-28 fiber are 0.1 dB and smaller than 0.4 dB, respectively.
文摘In this Letter, we propose a novel constellation-shaping carrier-less amplitude and phase （CAP） modulation scheme to alleviate the systematic nonlinearity in visible light communication （VLC） systems. A simple geo- metric transformation shaping method is employed to convert the normal square lattice constellation into multi- ple circular constellations. The feasibility and performance are investigated and experimentally demonstrated by a 1.25 Gb/s CAP-modulated VLC system. The results indicate that the circular constellation has better resis- tance to systematic nonlinearity compared with a rectangular constellation. The dynamic range of input signal peak-to-peak values promotes 20% at a low bias voltage nonlinear area and 50% at a high bias voltage nonlinear area. To the best of our knowledge, this is the first time constellation-shaping CAP has ever been reported in indoor high data rate VLC systems.
基金the NNSF of China(No.61177071)the Key Program of Shanghai Science and Technology Association(12dz1143000)the NHTRDP(863 Program)of China(2013AA013603).
文摘Asymmetrically clipped optical orthogonal frequency division multiplexing(ACO-OFDM)has been a promising candidate in visible light communications(VLC)due to its improvement in power efficiency and reduction of nonlinearity based on previous simulation analysis.In this paper,for the first time as far as we know,we experimentally verify that ACO-OFDM would be an efficient scheme to improve the performance of a gigabit wavelength division multiplexing VLC system.Our theoretical investigations reveal that the advantages of ACO-OFDM can be attributed to the reduction of inter-carrier interference caused by signal–signal beating noise.An aggregate data rate of 1.05 Gb∕s is successfully achieved over 30 cm transmission below the 7%forwarderror-correction threshold of 3.8×10−3.The experimental results show that ACO-OFDM can outperform DC-biased optical OFDM by BER performance of 1.5 dB at the same data rate and 4 dB at the same bandwidth,which clearly demonstrates the benefit and feasibility of ACO-OFDM.
基金supported by the National "973" Program of China(No.2010CB328300)the National Natural Science Foundation of China(Nos. 61107064,61177071,and 600837004)+3 种基金the Doctoral Fund of Ministry of Educationthe Open Fund of the State Key Lab of ASIC & System(No.11MS009)the Pujiang Fundthe Shuguang Fund
文摘The generation of coherent optical subcarriers based on a concatenated dual-drive Mach-Zehnder intensity modulator （IM） and two phase modulators （PMs） is proposed and experimentally demonstrated. The modulation index and DC bias of PM＋IM modulation are theoretically investigated. Theoretical analysis and numerical study are also carried out to examine the proposed scheme. We use 25-GHz RF synchronous sinusoidal signals to drive cascaded two-stage PMs and IM, through which we generate 28 subcaxriers with peak power fluctuations less than 4 dB. The measured tone-to-noise ratio of the subcarrier is higher than 40 dB. The experimental results show that for 100-Gb/s polarization multiplexing QPSK signal, the receiver sensitivity of the back-to-back signal is -28.6 dBm, and the power penalty is lower than 1 dB after 100-km transmission at the BER of 1 × 10-9.
基金supported by the National"973" Project of China (No. 2010CB328300)the National "863" Project of China (Nos. 2009AA01Z253 and 2009AA01A347)the National Natural Science Foundation of China (Nos. 600837004 and 60777010), and the Shuguang Fund
文摘Novel optical offset quadrature phase shift keying （OQPSK） and improved minimum-shift keying （MSK） modulation schemes to smooth optical phase hopping for high speed fiber optics transmission are proposed. Simulations have been done among the MSK, OQPSK, quadrature phase shift keying （QPSK）, and binary phase-shift keying （BPSK） modulation formats at 40 Gb/s over 100-km transmission link using coherent detection. Simulation results present good performances to elevate chromatic dispersion tolerance and reduce the influence of nonlinear effects by adopting the smooth phase modulation formats. Inter-symbol interference decreases for the fast side-lobe property and tight spectrum as a result of avoding the π phase shift and reducing envelop fluctuation.
基金supported by the National Key Research and Development Program of China(No.2022YFB2802803)the National Natural Science Foundation of China(Nos.61925104,62031011,and 62201157)the Major Key Project of PCL。
文摘We propose an encryption technique for underwater visible light communication[UVLC]based on chaotic phase scrambling[PS]and conjugate frequency hopping[CFH].The technique is experimentally tested using an 8-level pulse amplitude modulation[PAM-8]and a 1.2 m underwater link.The security key of the phase scrambling code is generated according to a logistic map,and the frequency hopping is achieved by adding the same zero frequency points to the signal spectrum.The maximum transmission rate of 2.1 Gbit/s is measured with bit-error-rate[BER]below 7%the hard-decision forward error correction[HD-FEC]threshold of 3.8×10^(-3).
