Real-Time segmented pulse compression-detection is one of the key technologies of space-borne tracking receiver.Its implementation requires an optimized and dedicated hardware.The real-time processing places several c...Real-Time segmented pulse compression-detection is one of the key technologies of space-borne tracking receiver.Its implementation requires an optimized and dedicated hardware.The real-time processing places several constraints such as area occupied,power comumption,and speed.A number of segmented compression techniques have been proposed to overcome these limitations and decrease the processing latency.However,relatively high power loss in the partial field could limit their implementation in many current real-time systems.A good theoretical model was designed with intersection signal accumulation to enhance signal-noise-ratio(SNR)gain of detecting signal in the paper.From the experimental results it is known that this approach works well for pulse compression-detection,which is better suited for implementation in the high performance of current field programmable gate array(FPGA)with dedicated hardware multipliers.展开更多
Industry leaders are currently setting out standards for 5G networks projected for 2020 or even sooner. Future generation networks will be heterogeneous in nature as no single network type will be capable of optimally...Industry leaders are currently setting out standards for 5G networks projected for 2020 or even sooner. Future generation networks will be heterogeneous in nature as no single network type will be capable of optimally meeting all the rapid changes in customer demands. With the advent of multi-homed devices and heterogeneous network (HetNet) solution, great concerns arise in the processes involved for successful handover. Active calls that get dropped or cases of poor quality of service experienced by mobile users can be attributed to the phenomenon of delayed handover (HO) or an outright case of an unsuccessful handover procedure. This work compares multiple criteria handover basis to its traditional single relative signal strength (RSS) base counterpart. It analyses the performance of a fuzzy-based VHO algorithm scheme in a Wi-Fi, WiMAX, UMTS and LTE integrated network using OMNeT++ event simulator. The loose coupling network architecture is adopted and simulation results analysed for the two major categories of handover;the multiple and single criteria. Results obtained show a better overall throughput, better call dropped rate and shorter handover time for the multiple criteria based decision method as compared to the single criteria based technique. This work also highlights current research trends, challenges of seamless handover and initiatives for Next Generation HetNet.展开更多
This paper studies wireless vehicular communication(VehCom)in intelligent transportation systems using an orthogonal frequency division multiplexing with index modulation(OFDM-IM).In the concept of IM,data is transmit...This paper studies wireless vehicular communication(VehCom)in intelligent transportation systems using an orthogonal frequency division multiplexing with index modulation(OFDM-IM).In the concept of IM,data is transmitted not only through the modulated symbols but also via the indices of the active subcarriers.In contrast to the original OFDM,OFDM-IM activates only non-zero subcarriers,increasing energy efficiency.However,the pilotassisted channel estimation(CE)method is a significant challenge in OFDM-IM,where the desired pilot subcarrier interval is related to the OFDM-IM subblock length.This paper proposes a walsh-scattered pilot-assisted CE for OFDM-IM VehCom.The optimum walsh-scattered pilot assignment is proposed to improve the transmission efficiency.Furthermore,a space-time block code with a high transmit diversity gain is employed for OFDM-IM VehCom to enhance VehCom's signal quality.The results show that the proposed method performs higher CE accuracy and better bit-error rate with significant spectral and energy efficiencies than conventional methods.展开更多
In ultra-dense networks(UDNs), large-scale deployment of femto base stations is an important technique for improving the network throughput and quality of service(QoS). In this paper, a multidimensional resource alloc...In ultra-dense networks(UDNs), large-scale deployment of femto base stations is an important technique for improving the network throughput and quality of service(QoS). In this paper, a multidimensional resource allocation algorithm based on noncooperation game theory is proposed to manage the resource allocation in UDNs, including transmission point association, user channels, and power. The algorithm derives a multidimensional resource optimization model and converts into a noncooperation game model according to the analysis of transmission point association user channel and power allocation. The algorithm includes two phases: transmission point association, and channel and power allocation. Then, feasible domain and discrete variables relaxation approaches are introduced to derive an approximate optimal multidimensional resource allocation solution with low complexity. Simulation results show that this method has some advantages in suppressing interference and improves the overall system throughput, while ensuring the QoS of femtocell users.展开更多
In this paper,the design of a resonator rectenna,based on metamaterials and capable of harvesting radio-frequency energy at 2.45 GHz to power any low-power devices,is presented.The proposed design uses a simple and in...In this paper,the design of a resonator rectenna,based on metamaterials and capable of harvesting radio-frequency energy at 2.45 GHz to power any low-power devices,is presented.The proposed design uses a simple and inexpensive circuit consisting of a microstrip patch antenna with a mushroom-like electromagnetic band gap(EBG),partially reflective surface(PRS)structure,rectifier circuit,voltage multiplier circuit,and 2.45 GHzWi-Fi module.The mushroom-like EBG sheet was fabricated on an FR4 substrate surrounding the conventional patch antenna to suppress surface waves so as to enhance the antenna performance.Furthermore,the antenna performance was improved more by utilizing the slotted I-shaped structure as a superstrate called a PRS surface.The enhancement occurred via the reflection of the transmitted power.The proposed rectenna achieved a maximum directive gain of 11.62 dBi covering the industrial,scientific,and medical radio band of 2.40–2.48 GHz.A Wi-Fi 4231 access point transmitted signals in the 2.45 GHz band.The rectenna,located 45◦anticlockwise relative to the access point,could achieve a maximum power of 0.53μW.In this study,the rectenna was fully characterized and charged to low-power devices.展开更多
In this paper, we exploit clustered interference alignment(IA) for efficient subchannel allocation in ultra-dense orthogonal frequency division multiplexing access(OFDMA) based femtocell networks, which notably improv...In this paper, we exploit clustered interference alignment(IA) for efficient subchannel allocation in ultra-dense orthogonal frequency division multiplexing access(OFDMA) based femtocell networks, which notably improves the spectral efficiency as well as addresses the feasibility issue of IA. Our problem is formulated as a combinatorial optimization problem which is NP-hard. To avoid obtaining its optimal solution by exhaustive search, we propose a two-phases efficient solution with low-complexity. The first phase groups all the femtocell user equipments(FUEs) into disjoint clusters, and the second phase allocates subchannels to the formed clusters where IA is performed. By doing this, the intra-cluster and inter-cluster interferences are mitigated by clustered IA and subchannel allocation in ultra-dense femtocell networks, respectively.Also, low-complexity algorithm is proposed to solve the corresponding sub-problem in each phase. Simulation results demonstrate that the proposed scheme not only outperforms other related schemes, but also provides a close performance to the optimal solution.展开更多
The predominant use of today＇s networks is content access and distribution. Network Coding （NC） is an innovative technique that has potential to improve the efficiency of multicast content distribution over multiho...The predominant use of today＇s networks is content access and distribution. Network Coding （NC） is an innovative technique that has potential to improve the efficiency of multicast content distribution over multihop Wireless Mesh Networks （WMNs） by allowing intermediate Forwarding Nodes （FNs） to encode and then forward data packets. Practical protocols are needed to realize the benefits of the NC technique. However, the existing NC-based multicast protocols cannot accurately determine the minimum number of coded packets that a FN should send in order to ensure successful data delivery to the destinations, so that many redundant packets are injected into the network, leading to performance degradation. In this paper, we propose HopCaster, a novel reliable multicast protocol that incorporates network coding with hop-by-hop transport. HopCaster completely eliminates the need for estimating the number of coded packets to be transmitted by a FN, and avoids redundant packet transmissions. It also effectively addresses the challenges of heterogeneous mulficast receivers. Moreover, a cross-layer multicast rate adaptation mechanism is proposed, which enables HopCaster to optimize multicast throughput by dynamically adjusting wireless transmission rate based on the changes in the receiver population and channel conditions during the course of mulficasting a coded data chunk. Our evaluations show that HopCaster significantly outperforms the existing NC-based multicast protocols.展开更多
Recently,the Muscle-Computer Interface(MCI)has been extensively popular for employing Electromyography(EMG)signals to help the development of various assistive devices.However,few studies have focused on ankle foot mo...Recently,the Muscle-Computer Interface(MCI)has been extensively popular for employing Electromyography(EMG)signals to help the development of various assistive devices.However,few studies have focused on ankle foot movement classification considering EMG signals at limb position.This work proposes a new framework considering two EMG signals at a lower-limb position to classify the ankle movement characteristics based on normal walking cycles.For this purpose,we introduce a human anklefoot movement classification method using a two-dimensional-convolutional neural network(2D-CNN)with low-cost EMG sensors based on lowerlimb motion.The time-domain signals of EMG obtained from two sensors belonging to Dorsiflexion,Neutral-position,and Plantarflexion are firstly converted into time-frequency spectrograms by short-time Fourier transform.Afterward,the spectrograms of the three ankle-foot movement types are used as input to the 2D-CNN such that the EMG foot movement types are finally classified.For the evaluation phase,the proposed method is investigated using the healthy volunteer for 5-fold cross-validation,and the accuracy is used as a standard evaluation.The results demonstrate that our approach provides an average accuracy of 99.34%.This exhibits the usefulness of 2D-CNN with low-cost EMG sensors in terms of ankle-foot movement classification at limb position,which offers feasibility for walking.However,the obtained EMG signal is not directly considered at the ankle position.展开更多
This research investigates a monopole patch antenna for Wi-Fi applications at 2.45 and 5.2 GHz,and WiMax at 3.5 GHz.A low-cost and flexible graphite sheet with good conductivity,base on graphite conductive powder and ...This research investigates a monopole patch antenna for Wi-Fi applications at 2.45 and 5.2 GHz,and WiMax at 3.5 GHz.A low-cost and flexible graphite sheet with good conductivity,base on graphite conductive powder and glue is used to create a radiator patch and ground plane.Instead of commercially available conductive inks or graphite sheets,we use our selfproduced graphite liquid to create the graphite sheet because it is easy to produce and inexpensive.The antenna structure is formed using a low-cost and easy hand-screen printing approach that involved placing graphite liquid on a bendable polyester substrate.This research focuses on designing and developing a low-cost,thin,light,and flexible patch antenna for wireless communication and smart glass applications.The proposed antenna utilizes CST microwave software for simulations to improve the parameters before fabrication and measurement.The simulation and measurement results for the reflection coefficients at 2.45 GHz,3.5 GHz,and 5.20 GHz are reliable and cover the required resonance frequencies,antennas gain are 1.91,1.98,and 1.87 dB,respectively.Additionally,the radiation patterns of both results are omnidirectional.In the experiments,bending the proposed patch antenna along with the cylinder with the radii of 60,40,and 25 mm yielded the same measurement results as the unbent patch antenna.展开更多
We address the problem of encoding entanglement-assisted （EA） quantum error-correcting codes （QECCs） and of the corresponding complexity. We present an iterative algorithm from which a quantum circuit composed of ...We address the problem of encoding entanglement-assisted （EA） quantum error-correcting codes （QECCs） and of the corresponding complexity. We present an iterative algorithm from which a quantum circuit composed of CNOT, H, and S gates can be derived directly with complexity O（n2） to encode the qubits being sent. Moreover, we derive the number of each gate consumed in our algorithm according to which we can design EA QECCs with low encoding complexity. Another advantage brought by our algorithm is the easiness and efficiency of programming on classical computers.展开更多
The RFID is a rapidly developing technology. It’s used in many applications such as logistics, ticketing, security, employee attendance record and others. Also, fractal technology is used in many areas, and recently ...The RFID is a rapidly developing technology. It’s used in many applications such as logistics, ticketing, security, employee attendance record and others. Also, fractal technology is used in many areas, and recently in antenna design because it allows making multi-band and wide-band antennas. In this paper, two tri-band fractal antennas are studied for the Radio Frequency Identification (RFID) applications using the Method of Moment (MoM). The first one is designed for the RFID readers and it operates at 3.85 GHZ, 5.80 GHZ and 8.12 GHZ. The second one is designed for the RFID Tags and it operates at 3.94 GHZ, 5.65 GHZ and 8.20 GHZ.展开更多
This paper presents a hypothesis regarding the existence of time fused in spacetime, assuming that time possesses the properties of both a particle and a field. This duality is referred to as the field-particle of tim...This paper presents a hypothesis regarding the existence of time fused in spacetime, assuming that time possesses the properties of both a particle and a field. This duality is referred to as the field-particle of time (FPT). The analysis shows that when the FPT moves through matter, it causes time dilation. The FPT is also a significant element that appears in relativistic kinetic energy (KE = (γ - 1) · mc<sup>2</sup>). Accelerating matter to near the speed of light requires relativistic energy approaching infinity, which corresponds to the relativistic kinetic energy. Meanwhile, the potential energy (PE = mc<sup>2</sup>) from the rest mass remains constant. Then, the mass-energy equation can be rearranged in terms of PE and KE, as shown in E = (1 + (γ - 1)) · mc<sup>2</sup>. The relativistic energy of the FPT also directly affects the gravitational attraction of matter. It transfers energy to each other through spacetime. The analysis demonstrates that the gravitational force is inversely proportional to the distance squared, following Newton’s law of gravity, and it varies with the relative velocity of matter. The relationship equation between relative time and the gravitational constant indicates that a higher intensity of the gravitational field leads to a slower reference time for matter, in accordance with the general theory of relativity. A thought experiment presents a comparison of two atomic clocks placed in different locations. The first one is placed in a room temperature, around 25°C, on the surface of the Earth, and the second one is placed in high-density areas. The analysis, considering the presence of the FPT, shows that the reference time slows down in high-density areas. Therefore, the second clock must be noticeably slower than the first one, indicating the existence of the FPT passing through both atomic clocks at different speeds.展开更多
While Global Navigation Satellite Systems(GNSS)have been the primary Positioning,Navigation,and Timing(PNT)solution since their advent,new technologies are being sought to address the limitations of GNSS.For the past ...While Global Navigation Satellite Systems(GNSS)have been the primary Positioning,Navigation,and Timing(PNT)solution since their advent,new technologies are being sought to address the limitations of GNSS.For the past few years,the strongest contender to ofer global PNT solutions has been the use of Low Earth Orbit(LEO)satellites,not only to overcome the GNSS limitations but also to improve the positioning accuracy and coverage given the pro-liferation of new,more-demanding applications.The present work aims at shedding light on the LEO theoreti-cally achievable positioning accuracy and interference robustness with respect to GNSS,depending on the choice of the carrier frequency,constellation design,hybridization with GNSS,and available satellite transmission power.The analysis uses a semi-analytical approach with 192,000 Monte Carlo runs,employing an in-house satellite constellation simulator to model 400 users across Europe operating in fve representative outdoor scenarios,and for 480 diferent instances of satellite positions in time.This semi-analytical study provides the necessary insights to derive clear design takeaways depending on the choice of the aforementioned parameters.A moderate Efective Isotropic Radiated Power(EIRP)of 50 dBm is shown to be sufcient for achieving high accuracy outdoors,operating at the C-band in the urban scenarios where GNSS typically struggles.The most cost-efective hybrid LEO plus GNSS solutions come from the combination of 1)‘CentiSpace-like’plus BeiDou,and 2)‘Çelikbilek 1’plus GPS and Galileo,where LEO satellites drive performance in difcult environments while GNSS provides stability in nominal conditions.The fndings suggest using the‘Çelikbilek 1’constellation with a 50 dBm EIRP at a 5 GHz carrier frequency or higher as the most efective system design.展开更多
I. INTRODUCTION MacWilliams and Sloane listed as an open problem the classification of all Bent functions of a given order. So far, there is not any satisfied method to construct all Bent sequences. Adams and Tavares ...I. INTRODUCTION MacWilliams and Sloane listed as an open problem the classification of all Bent functions of a given order. So far, there is not any satisfied method to construct all Bent sequences. Adams and Tavares had done some useful research to generate and count binary Bent sequences. In this note, we present a method of constructing a new class of binary Bent se-展开更多
The pseudorandom sequences used widely in spread spectrum communications and cryptography are required to have not only large linear complexity, but also good auto(cross-)correlation properties. Now it is known that t...The pseudorandom sequences used widely in spread spectrum communications and cryptography are required to have not only large linear complexity, but also good auto(cross-)correlation properties. Now it is known that there are four kinds of sequences having the ideal two-valued autocorrelation function, they are m-sequences, L-sequences, Hall sequences and GMWsequences, but the number of these sequences is all small. We have constructed a new kind of sequences with two-valued autocorrelation展开更多
Orthogonal Frequency Division Multiplexing （ OFDM） system is sensitive to Carrier Frequency Offset （ CFO ）. In this paper, traditional Maximum Likelihood Estimators （MLE） for CFO of OFDM are introduced first. Th...Orthogonal Frequency Division Multiplexing （ OFDM） system is sensitive to Carrier Frequency Offset （ CFO ）. In this paper, traditional Maximum Likelihood Estimators （MLE） for CFO of OFDM are introduced first. Then, averaging method and a-filter are introduced as Low Pass Filter （LPF） to improve the performance of cyclic prefix estimator. The bandwith of LPF is determined by the coherence time of radio channel. Estimation performance in multipath channel is analyzed. Outlier picking-out scheme is proposed to improve performance further. Performance of close-loop structure is presented briefly, which is worse than that of open-loop structure. Finally, a parallel switch structure of frequency synchronizer is proposed for mobile OFDM systems. The scheme ezcploits training sequence and cyclic prefix. The proposed synchronizer has a wide acquisition range. It is accurate and robust in both AWGN channel and multipath channels. The complexity is low due to functionality of a-filter. A better performance of frequevlcy synchronization is obtained comparing to that of existing Maximum Likelihood Estimator（ MLEs）. We achieve these advantages without loss of bandwidth efficiency.展开更多
A novel Call Admission Control(CAC)scheme is proposed for multimedia CDMA systems.The effectivebandwidth of real time calls is reserved in the CAC with the consideration of active factors.The admission of non-real tim...A novel Call Admission Control(CAC)scheme is proposed for multimedia CDMA systems.The effectivebandwidth of real time calls is reserved in the CAC with the consideration of active factors.The admission of non-real timecalls is controlled by the system according to the residual effective bandwidth left from real time calls.Simulation resultshave shown that the novel CAC has greatly enlarged the admission region for real time calls and make the transmission de-lay of non-real time calls under an acceptable level.展开更多
基金Correspondence should be addressed to:YANG Jian-xi,E-mail:navicom@foxmail.com
文摘Real-Time segmented pulse compression-detection is one of the key technologies of space-borne tracking receiver.Its implementation requires an optimized and dedicated hardware.The real-time processing places several constraints such as area occupied,power comumption,and speed.A number of segmented compression techniques have been proposed to overcome these limitations and decrease the processing latency.However,relatively high power loss in the partial field could limit their implementation in many current real-time systems.A good theoretical model was designed with intersection signal accumulation to enhance signal-noise-ratio(SNR)gain of detecting signal in the paper.From the experimental results it is known that this approach works well for pulse compression-detection,which is better suited for implementation in the high performance of current field programmable gate array(FPGA)with dedicated hardware multipliers.
文摘Industry leaders are currently setting out standards for 5G networks projected for 2020 or even sooner. Future generation networks will be heterogeneous in nature as no single network type will be capable of optimally meeting all the rapid changes in customer demands. With the advent of multi-homed devices and heterogeneous network (HetNet) solution, great concerns arise in the processes involved for successful handover. Active calls that get dropped or cases of poor quality of service experienced by mobile users can be attributed to the phenomenon of delayed handover (HO) or an outright case of an unsuccessful handover procedure. This work compares multiple criteria handover basis to its traditional single relative signal strength (RSS) base counterpart. It analyses the performance of a fuzzy-based VHO algorithm scheme in a Wi-Fi, WiMAX, UMTS and LTE integrated network using OMNeT++ event simulator. The loose coupling network architecture is adopted and simulation results analysed for the two major categories of handover;the multiple and single criteria. Results obtained show a better overall throughput, better call dropped rate and shorter handover time for the multiple criteria based decision method as compared to the single criteria based technique. This work also highlights current research trends, challenges of seamless handover and initiatives for Next Generation HetNet.
文摘This paper studies wireless vehicular communication(VehCom)in intelligent transportation systems using an orthogonal frequency division multiplexing with index modulation(OFDM-IM).In the concept of IM,data is transmitted not only through the modulated symbols but also via the indices of the active subcarriers.In contrast to the original OFDM,OFDM-IM activates only non-zero subcarriers,increasing energy efficiency.However,the pilotassisted channel estimation(CE)method is a significant challenge in OFDM-IM,where the desired pilot subcarrier interval is related to the OFDM-IM subblock length.This paper proposes a walsh-scattered pilot-assisted CE for OFDM-IM VehCom.The optimum walsh-scattered pilot assignment is proposed to improve the transmission efficiency.Furthermore,a space-time block code with a high transmit diversity gain is employed for OFDM-IM VehCom to enhance VehCom's signal quality.The results show that the proposed method performs higher CE accuracy and better bit-error rate with significant spectral and energy efficiencies than conventional methods.
基金supported by Natural Science Foundation of China (61372125)973 project (2013CB329104)+1 种基金Natural Science Foundation of the Higher Education Institutions of Jiangsu Province (16KJA510005)the open research fund of National Mobile Communications Research Laboratory, Southeast University (2013D01, 2015D10)
文摘In ultra-dense networks(UDNs), large-scale deployment of femto base stations is an important technique for improving the network throughput and quality of service(QoS). In this paper, a multidimensional resource allocation algorithm based on noncooperation game theory is proposed to manage the resource allocation in UDNs, including transmission point association, user channels, and power. The algorithm derives a multidimensional resource optimization model and converts into a noncooperation game model according to the analysis of transmission point association user channel and power allocation. The algorithm includes two phases: transmission point association, and channel and power allocation. Then, feasible domain and discrete variables relaxation approaches are introduced to derive an approximate optimal multidimensional resource allocation solution with low complexity. Simulation results show that this method has some advantages in suppressing interference and improves the overall system throughput, while ensuring the QoS of femtocell users.
基金supported by the Rajamangala University of Technology Thanyaburi research and development fund.
文摘In this paper,the design of a resonator rectenna,based on metamaterials and capable of harvesting radio-frequency energy at 2.45 GHz to power any low-power devices,is presented.The proposed design uses a simple and inexpensive circuit consisting of a microstrip patch antenna with a mushroom-like electromagnetic band gap(EBG),partially reflective surface(PRS)structure,rectifier circuit,voltage multiplier circuit,and 2.45 GHzWi-Fi module.The mushroom-like EBG sheet was fabricated on an FR4 substrate surrounding the conventional patch antenna to suppress surface waves so as to enhance the antenna performance.Furthermore,the antenna performance was improved more by utilizing the slotted I-shaped structure as a superstrate called a PRS surface.The enhancement occurred via the reflection of the transmitted power.The proposed rectenna achieved a maximum directive gain of 11.62 dBi covering the industrial,scientific,and medical radio band of 2.40–2.48 GHz.A Wi-Fi 4231 access point transmitted signals in the 2.45 GHz band.The rectenna,located 45◦anticlockwise relative to the access point,could achieve a maximum power of 0.53μW.In this study,the rectenna was fully characterized and charged to low-power devices.
基金supported by China Scholarship Council (201406960042)the National Science Foundation (91338115,61231008)+2 种基金National S&T Major Project (2015ZX03002006)Program for Changjiang Scholars and Innovative Research Team in University (IRT0852)the 111 Project (B08038)
文摘In this paper, we exploit clustered interference alignment(IA) for efficient subchannel allocation in ultra-dense orthogonal frequency division multiplexing access(OFDMA) based femtocell networks, which notably improves the spectral efficiency as well as addresses the feasibility issue of IA. Our problem is formulated as a combinatorial optimization problem which is NP-hard. To avoid obtaining its optimal solution by exhaustive search, we propose a two-phases efficient solution with low-complexity. The first phase groups all the femtocell user equipments(FUEs) into disjoint clusters, and the second phase allocates subchannels to the formed clusters where IA is performed. By doing this, the intra-cluster and inter-cluster interferences are mitigated by clustered IA and subchannel allocation in ultra-dense femtocell networks, respectively.Also, low-complexity algorithm is proposed to solve the corresponding sub-problem in each phase. Simulation results demonstrate that the proposed scheme not only outperforms other related schemes, but also provides a close performance to the optimal solution.
文摘The predominant use of today＇s networks is content access and distribution. Network Coding （NC） is an innovative technique that has potential to improve the efficiency of multicast content distribution over multihop Wireless Mesh Networks （WMNs） by allowing intermediate Forwarding Nodes （FNs） to encode and then forward data packets. Practical protocols are needed to realize the benefits of the NC technique. However, the existing NC-based multicast protocols cannot accurately determine the minimum number of coded packets that a FN should send in order to ensure successful data delivery to the destinations, so that many redundant packets are injected into the network, leading to performance degradation. In this paper, we propose HopCaster, a novel reliable multicast protocol that incorporates network coding with hop-by-hop transport. HopCaster completely eliminates the need for estimating the number of coded packets to be transmitted by a FN, and avoids redundant packet transmissions. It also effectively addresses the challenges of heterogeneous mulficast receivers. Moreover, a cross-layer multicast rate adaptation mechanism is proposed, which enables HopCaster to optimize multicast throughput by dynamically adjusting wireless transmission rate based on the changes in the receiver population and channel conditions during the course of mulficasting a coded data chunk. Our evaluations show that HopCaster significantly outperforms the existing NC-based multicast protocols.
基金This work was supported by Suranaree University of Technology(SUT),Thailand Science Research and Innovation(TSRI),and National Science Research and Innovation Fund(NSRF)(NRIIS no.42852).
文摘Recently,the Muscle-Computer Interface(MCI)has been extensively popular for employing Electromyography(EMG)signals to help the development of various assistive devices.However,few studies have focused on ankle foot movement classification considering EMG signals at limb position.This work proposes a new framework considering two EMG signals at a lower-limb position to classify the ankle movement characteristics based on normal walking cycles.For this purpose,we introduce a human anklefoot movement classification method using a two-dimensional-convolutional neural network(2D-CNN)with low-cost EMG sensors based on lowerlimb motion.The time-domain signals of EMG obtained from two sensors belonging to Dorsiflexion,Neutral-position,and Plantarflexion are firstly converted into time-frequency spectrograms by short-time Fourier transform.Afterward,the spectrograms of the three ankle-foot movement types are used as input to the 2D-CNN such that the EMG foot movement types are finally classified.For the evaluation phase,the proposed method is investigated using the healthy volunteer for 5-fold cross-validation,and the accuracy is used as a standard evaluation.The results demonstrate that our approach provides an average accuracy of 99.34%.This exhibits the usefulness of 2D-CNN with low-cost EMG sensors in terms of ankle-foot movement classification at limb position,which offers feasibility for walking.However,the obtained EMG signal is not directly considered at the ankle position.
基金This work was supported by the RMUTT research and development fund。
文摘This research investigates a monopole patch antenna for Wi-Fi applications at 2.45 and 5.2 GHz,and WiMax at 3.5 GHz.A low-cost and flexible graphite sheet with good conductivity,base on graphite conductive powder and glue is used to create a radiator patch and ground plane.Instead of commercially available conductive inks or graphite sheets,we use our selfproduced graphite liquid to create the graphite sheet because it is easy to produce and inexpensive.The antenna structure is formed using a low-cost and easy hand-screen printing approach that involved placing graphite liquid on a bendable polyester substrate.This research focuses on designing and developing a low-cost,thin,light,and flexible patch antenna for wireless communication and smart glass applications.The proposed antenna utilizes CST microwave software for simulations to improve the parameters before fabrication and measurement.The simulation and measurement results for the reflection coefficients at 2.45 GHz,3.5 GHz,and 5.20 GHz are reliable and cover the required resonance frequencies,antennas gain are 1.91,1.98,and 1.87 dB,respectively.Additionally,the radiation patterns of both results are omnidirectional.In the experiments,bending the proposed patch antenna along with the cylinder with the radii of 60,40,and 25 mm yielded the same measurement results as the unbent patch antenna.
基金supported by the National Basic Research Program of China (Grant No.2010CB328300)the National Natural Science Foundation of China (Grant Nos.60972046 and 60902030)+4 种基金the Program for Changjiang Scholars and Innovative Research Team in University (Grant No.IRT0852)the Natural Science Foundation of Shaanxi Province (Grant No.2010JQ8025)the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No.20100203120004)the 111 Program (Grant No.B08038)the China Scholarship Council (Grant No.[2008]3019)
文摘We address the problem of encoding entanglement-assisted （EA） quantum error-correcting codes （QECCs） and of the corresponding complexity. We present an iterative algorithm from which a quantum circuit composed of CNOT, H, and S gates can be derived directly with complexity O（n2） to encode the qubits being sent. Moreover, we derive the number of each gate consumed in our algorithm according to which we can design EA QECCs with low encoding complexity. Another advantage brought by our algorithm is the easiness and efficiency of programming on classical computers.
文摘The RFID is a rapidly developing technology. It’s used in many applications such as logistics, ticketing, security, employee attendance record and others. Also, fractal technology is used in many areas, and recently in antenna design because it allows making multi-band and wide-band antennas. In this paper, two tri-band fractal antennas are studied for the Radio Frequency Identification (RFID) applications using the Method of Moment (MoM). The first one is designed for the RFID readers and it operates at 3.85 GHZ, 5.80 GHZ and 8.12 GHZ. The second one is designed for the RFID Tags and it operates at 3.94 GHZ, 5.65 GHZ and 8.20 GHZ.
文摘This paper presents a hypothesis regarding the existence of time fused in spacetime, assuming that time possesses the properties of both a particle and a field. This duality is referred to as the field-particle of time (FPT). The analysis shows that when the FPT moves through matter, it causes time dilation. The FPT is also a significant element that appears in relativistic kinetic energy (KE = (γ - 1) · mc<sup>2</sup>). Accelerating matter to near the speed of light requires relativistic energy approaching infinity, which corresponds to the relativistic kinetic energy. Meanwhile, the potential energy (PE = mc<sup>2</sup>) from the rest mass remains constant. Then, the mass-energy equation can be rearranged in terms of PE and KE, as shown in E = (1 + (γ - 1)) · mc<sup>2</sup>. The relativistic energy of the FPT also directly affects the gravitational attraction of matter. It transfers energy to each other through spacetime. The analysis demonstrates that the gravitational force is inversely proportional to the distance squared, following Newton’s law of gravity, and it varies with the relative velocity of matter. The relationship equation between relative time and the gravitational constant indicates that a higher intensity of the gravitational field leads to a slower reference time for matter, in accordance with the general theory of relativity. A thought experiment presents a comparison of two atomic clocks placed in different locations. The first one is placed in a room temperature, around 25°C, on the surface of the Earth, and the second one is placed in high-density areas. The analysis, considering the presence of the FPT, shows that the reference time slows down in high-density areas. Therefore, the second clock must be noticeably slower than the first one, indicating the existence of the FPT passing through both atomic clocks at different speeds.
基金supported by Tampere University’s Dean’s PhD grant.This work has also been partially supported by the LEDSOL project funded within the LEAP-RE programme by the European Union’s Horizon 2020 Research and Innovation Program under Grant Agreement 963530the Research Council of Finland grant 352364+2 种基金the Spanish Agency of Research(AEI)under grant PID2023-152820OB-I00 funded by MICIU/AEI/10.13039/501100011033ERDF/EU,and grant PDC2023-145858-I00 funded by MICIU/AEI/10.13039/501100011033the European Union NextGenerationEU/PRTR.
文摘While Global Navigation Satellite Systems(GNSS)have been the primary Positioning,Navigation,and Timing(PNT)solution since their advent,new technologies are being sought to address the limitations of GNSS.For the past few years,the strongest contender to ofer global PNT solutions has been the use of Low Earth Orbit(LEO)satellites,not only to overcome the GNSS limitations but also to improve the positioning accuracy and coverage given the pro-liferation of new,more-demanding applications.The present work aims at shedding light on the LEO theoreti-cally achievable positioning accuracy and interference robustness with respect to GNSS,depending on the choice of the carrier frequency,constellation design,hybridization with GNSS,and available satellite transmission power.The analysis uses a semi-analytical approach with 192,000 Monte Carlo runs,employing an in-house satellite constellation simulator to model 400 users across Europe operating in fve representative outdoor scenarios,and for 480 diferent instances of satellite positions in time.This semi-analytical study provides the necessary insights to derive clear design takeaways depending on the choice of the aforementioned parameters.A moderate Efective Isotropic Radiated Power(EIRP)of 50 dBm is shown to be sufcient for achieving high accuracy outdoors,operating at the C-band in the urban scenarios where GNSS typically struggles.The most cost-efective hybrid LEO plus GNSS solutions come from the combination of 1)‘CentiSpace-like’plus BeiDou,and 2)‘Çelikbilek 1’plus GPS and Galileo,where LEO satellites drive performance in difcult environments while GNSS provides stability in nominal conditions.The fndings suggest using the‘Çelikbilek 1’constellation with a 50 dBm EIRP at a 5 GHz carrier frequency or higher as the most efective system design.
基金Project supported by the University Science and Technology Foundation of National Education Commission of China
文摘I. INTRODUCTION MacWilliams and Sloane listed as an open problem the classification of all Bent functions of a given order. So far, there is not any satisfied method to construct all Bent sequences. Adams and Tavares had done some useful research to generate and count binary Bent sequences. In this note, we present a method of constructing a new class of binary Bent se-
基金'Project supported by the University SC & Tech. Foundation of China.
文摘The pseudorandom sequences used widely in spread spectrum communications and cryptography are required to have not only large linear complexity, but also good auto(cross-)correlation properties. Now it is known that there are four kinds of sequences having the ideal two-valued autocorrelation function, they are m-sequences, L-sequences, Hall sequences and GMWsequences, but the number of these sequences is all small. We have constructed a new kind of sequences with two-valued autocorrelation
文摘Orthogonal Frequency Division Multiplexing （ OFDM） system is sensitive to Carrier Frequency Offset （ CFO ）. In this paper, traditional Maximum Likelihood Estimators （MLE） for CFO of OFDM are introduced first. Then, averaging method and a-filter are introduced as Low Pass Filter （LPF） to improve the performance of cyclic prefix estimator. The bandwith of LPF is determined by the coherence time of radio channel. Estimation performance in multipath channel is analyzed. Outlier picking-out scheme is proposed to improve performance further. Performance of close-loop structure is presented briefly, which is worse than that of open-loop structure. Finally, a parallel switch structure of frequency synchronizer is proposed for mobile OFDM systems. The scheme ezcploits training sequence and cyclic prefix. The proposed synchronizer has a wide acquisition range. It is accurate and robust in both AWGN channel and multipath channels. The complexity is low due to functionality of a-filter. A better performance of frequevlcy synchronization is obtained comparing to that of existing Maximum Likelihood Estimator（ MLEs）. We achieve these advantages without loss of bandwidth efficiency.
文摘A novel Call Admission Control(CAC)scheme is proposed for multimedia CDMA systems.The effectivebandwidth of real time calls is reserved in the CAC with the consideration of active factors.The admission of non-real timecalls is controlled by the system according to the residual effective bandwidth left from real time calls.Simulation resultshave shown that the novel CAC has greatly enlarged the admission region for real time calls and make the transmission de-lay of non-real time calls under an acceptable level.
