Terahertz(THz)wireless communication has been recognized as a powerful technology to meet the everincreasing demand of ultra-high rate services.In order to achieve efficient and reliable wireless communications over T...Terahertz(THz)wireless communication has been recognized as a powerful technology to meet the everincreasing demand of ultra-high rate services.In order to achieve efficient and reliable wireless communications over THz bands,it is extremely necessary to find an appropriate waveform for THz communications.In this paper,performance comparison of various single-carrier and multi-carrier waveforms over THz channels will be provided.Specifically,first,a system model for terahertz communication is briefly described,which includes amplifier nonlinearity,propagation characteristic,phase noise,etc.Then,the transceiver architectures related to both single-carrier and multi-carrier waveforms are presented,as well as their corresponding signal processing techniques.To evaluate the suitability of the waveforms,key performance metrics concerning power efficiency,transmission performance,and computational complexity are provided.Simulation results are provided to compare and validate the performance of different waveforms,which demonstrate the outstanding performance of Discrete-Fourier-Transform spread Orthogonal Frequency Division Multiplexing(DFT-s-OFDM)to THz communications when compared to Cyclic Prefix-OFDM(CP-OFDM)and other single-carrier waveforms.展开更多
Unlike the existing resonance region radar systems （RRRS ） that transmit the orthogonal frequency division multiplexing （OFDM）multi-carrier waveform,the dense multi-carrier （DMC）radar waveform which has a narrow...Unlike the existing resonance region radar systems （RRRS ） that transmit the orthogonal frequency division multiplexing （OFDM）multi-carrier waveform,the dense multi-carrier （DMC）radar waveform which has a narrower frequency interval than the traditional OFDM waveform is proposed.Therefore,in the same frequency bandwidth,the DMC waveform contains more sub-carriers and provides more frequency diversity.Additionally,to further improve detection performance,a novel optimal weight accumulation target detection （OWATD）method is proposed,where the echo electromagnetic waves at different frequencies are accumulated with the optimal weight coefficients.Then,with the signal-to-noise ratio （SNR）of echo waveform approaching infinity,the asymptotic detection performance is analyzed, and the condition that the OWATD method with the DMC outperforms the matched filter with the OFDM is presented.Simulation results show that the DMC outperforms the OFDM in the target detection performance,and the OWATD method can further improve the detection performance of the traditional methods with both the OFDM and DMC radar waveform.展开更多
For the carbon-neutral,a multi-carrier renewable energy system(MRES),driven by the wind,solar and geothermal,was considered as an effective solution to mitigate CO2emissions and reduce energy usage in the building sec...For the carbon-neutral,a multi-carrier renewable energy system(MRES),driven by the wind,solar and geothermal,was considered as an effective solution to mitigate CO2emissions and reduce energy usage in the building sector.A proper sizing method was essential for achieving the desired 100%renewable energy system of resources.This paper presented a bi-objective optimization formulation for sizing the MRES using a constrained genetic algorithm(GA)coupled with the loss of power supply probability(LPSP)method to achieve the minimal cost of the system and the reliability of the system to the load real time requirement.An optimization App has been developed in MATLAB environment to offer a user-friendly interface and output the optimized design parameters when given the load demand.A case study of a swimming pool building was used to demonstrate the process of the proposed design method.Compared to the conventional distributed energy system,the MRES is feasible with a lower annual total cost(ATC).Additionally,the ATC decreases as the power supply reliability of the renewable system decreases.There is a decrease of 24%of the annual total cost when the power supply probability is equal to 8%compared to the baseline case with 0%power supply probability.展开更多
A novel scheme of M-ary multi-carrier spread spectrum based on wavelet packet is proposed. Its performance is investigated for a multipath, slow Rayteigh fading channel. The performance advantages of the system over t...A novel scheme of M-ary multi-carrier spread spectrum based on wavelet packet is proposed. Its performance is investigated for a multipath, slow Rayteigh fading channel. The performance advantages of the system over that based on DFT are demonstrated by both analytical and simulation methods.展开更多
In multi-user wireless communication systems,adaptive modulation and scheduling are promising techniques for increasing system throughput.However,for multi-carrier systems,they will lead to overwhelming user feedback ...In multi-user wireless communication systems,adaptive modulation and scheduling are promising techniques for increasing system throughput.However,for multi-carrier systems,they will lead to overwhelming user feedback overhead for Channel Quality Indication(CQI) in every subcarrier.In our work,novel CQI feedback schemes are proposed based on the recently proposed theory of Compressive Sensing(CS).First,the standard CS method is introduced to reduce CQI feedback overhead for multi-carrier Multiple-Input Multiple-Output transmission.In addition,via further research on the design of measurement matrix with standard CS,a novel CQI feedback scheme based on subspace CS is proposed by exploiting the subspace information of the underlying signal and the feedback rate is greatly decreased.Simulation results show that,with the same feedback rate,the throughputs with subspace CS outperform the Discrete Cosine Transform(DCT)-based method which is usually employed,and the throughputs with standard CS outperform DCT when the feedback rate is larger than 0.13 bits/subcarrier.展开更多
To solve the inter carrier interference （ICI） elimination problem of an M-band wavelet multi-carrier modulation system, this paper analyzes the principle of the ICI caused by the Doppler frequency shift and its math...To solve the inter carrier interference （ICI） elimination problem of an M-band wavelet multi-carrier modulation system, this paper analyzes the principle of the ICI caused by the Doppler frequency shift and its mathematical expression based on the M-band wavelet multi-carrier modulation system model. Through the analysis of the mathematical expression and combining with the perfect reconstruction conditions of the filter banks, we propose the design conditions of an M-band filter to reduce and eliminate the ICI. The impulse response model of the filter design conditions and an iterative algorithm is also established. The simulation results show that the proposed ICI reduction and elimination methods can effectively improve the system performance.展开更多
Single-layered zirconium pentatelluride （ZrTes） has been predicted to be a large-gap two-dimensional （2D） topolog- ical insulator, which has attracted particular attention in topological phase transitions and pote...Single-layered zirconium pentatelluride （ZrTes） has been predicted to be a large-gap two-dimensional （2D） topolog- ical insulator, which has attracted particular attention in topological phase transitions and potential device applications. Herein, we investigated the transport properties in ZrTe5 films as a function of thickness, ranging from a few nm to several hundred nm. We determined that the temperature of the resistivity anomaly peak （Tp） tends to increase as the thickness decreases. Moreover, at a critical thickness of ~ 40 rim, the dominating carriers in the films change from n-type to p-type. A comprehensive investigation of Shubnikov-de Hass （SdH） oscillations and Hall resistance at variable temperatures revealed a multi-carrier transport tendency in the thin films. We determined the carrier densities and mobilities of two majority car- riers using the simplified two-carrier model. The electron carriers can be attributed to the Dirac band with a non-trivial Berry phase ~, while the hole carriers may originate from surface chemical reaction or unintentional doping during the microfabrication process. It is necessary to encapsulate the ZrTe5 film in an inert or vacuum environment to potentially achieve a substantial improvement in device quality.展开更多
In order to identify the multi-carrier orthogonal frequency division multiplexing(OFDM) and the single-carrier signal in the non-Gaussian noise environment, different features of the two signals are analyzed in terms ...In order to identify the multi-carrier orthogonal frequency division multiplexing(OFDM) and the single-carrier signal in the non-Gaussian noise environment, different features of the two signals are analyzed in terms of five parameters: generalized normalized fourth-order cumulant, the maximum value of the instantaneous amplitude power spectral density, absolute standard deviation of instantaneous phase on the section with weak signals, and position and numbers of the generalized cyclic spectrum's peak. The recognition method of the multi-carrier OFDM and single-carrier signal is proposed in the environment with alpha-stable distribution noise. Simulation results show that the recognition rate of the multi-carrier OFDM can reach 100% when the mixed signal to noise ratio(MSNR) is greater than-5 dB and the recognition rate can reach 90% for the single-carrier when the MSNR is greater than 2 dB.展开更多
The parallel interference c an cellation for multi-carrier DS-CDMA (which is termed FDC-PIC) is proposed by integrating frequency diversity combination. The simulations are made over FDC- PIC with respect to different...The parallel interference c an cellation for multi-carrier DS-CDMA (which is termed FDC-PIC) is proposed by integrating frequency diversity combination. The simulations are made over FDC- PIC with respect to different decision ways——hard, soft and linear decisions, respectively, and we conclude that FDC-PIC acquires superior performance improv ement over correlation reception of multi-carrier DS CDMA. With an increase in interference cancellation stages, the system performance is improved further. Th e initial 2 stages bring about the most dominant performance improvement, but up to the 3rd stage the system performance is improved little. It is also shown by the simulation results that FDC-PIC with soft decision would exhibit the best performance with a high implementation complexity, while FDC-PIC with linear de cision acquires performance comparable to that of FDC-PIC with soft decision wi th a reduced-complexity if the number of the interference cancellation stages i s the same, which indicates that FDC-PIC with linear decision has optimal perfo rmance/complexity tradeoff and therefore will be suitable for practical applica tion in future.展开更多
The dominate factors caused by reasons of losing the orthogonality in fading channel including FBC (fading branch correlation), CFO (carrier frequency offset), and even the CPN (carrier phase noise) are novel discussi...The dominate factors caused by reasons of losing the orthogonality in fading channel including FBC (fading branch correlation), CFO (carrier frequency offset), and even the CPN (carrier phase noise) are novel discussion in this letter. The first one factor causes the ISI (inter-symbol interference), and, however, the latter two will lead to the phenomenon of CPE (common phase error) and ICI (inter-carrier interference). On the other hand, they will lead to the loss of orthogonality for the radio system with multi-carrier modulating schemes, i.e., both them mainly deteriorate a wireless communication system. Eventually, in this letter not only the analytical expressions are derived, but a three dimension numerical results from the analysis involve the three parameters also illustrated is.展开更多
Denmark’ goal of being independent of fossil energy sources in 2050 puts forward great demands on all energy subsystems (electricity, heat, gas and transport, etc.) to be operated in a holistic manner. The Danish exp...Denmark’ goal of being independent of fossil energy sources in 2050 puts forward great demands on all energy subsystems (electricity, heat, gas and transport, etc.) to be operated in a holistic manner. The Danish experience and challenges of wind power integration and the development of district heating systems are summarized in this paper. How to optimally use the cross-sectoral flexibility by intelligent control (model predictive control-based) of the key coupling components in an integrated heat and power system including electrical heat pumps in the demand side, and thermal storage applications in buildings is investigated.展开更多
An interference suppression design scheme based on conjugate weighted butterfly interleaving mapping(CWBIM)is proposed for inter-carrier interference(ICI)and inter-subband interference(IBI)in the received signals of u...An interference suppression design scheme based on conjugate weighted butterfly interleaving mapping(CWBIM)is proposed for inter-carrier interference(ICI)and inter-subband interference(IBI)in the received signals of universal filtered multi-carrier(UFMC)systems.It applies an interleaving mapping operation to subtract the interference coefficients of adjacent terms in ICI and IBI twice,thereby achieving suppression effects similar to the self-cancellation(SC)algorithm while maintaining the original data transmission efficiency.Meanwhile,conjugate and complex weighting operations can effectively suppress the impact of phase rotation errors in high-speed mobile channel environments,thereby further improving the bit error rate(BFR)performance of the system,Moreover,butterfly operation can effectively control the computational complexity of the interleaving mapping process.Theoretical analysis and simulation results show that,compared with the PSC-UFMC algorithm,the CWBIM-UFMC scheme proposed in this paper can effectively suppress ICI and IBI in the received signal without compromising data transmission efficiency and reducing computational complexity,thereby achieving good BER performance of the system.展开更多
In response to the problem of inter-carrier interference(ICI)and inter-subband interference(IBI)in the received signals of universal filtered multi-carrier(UFMC)systems,a novel interfer-ence suppression design scheme ...In response to the problem of inter-carrier interference(ICI)and inter-subband interference(IBI)in the received signals of universal filtered multi-carrier(UFMC)systems,a novel interfer-ence suppression design scheme applying the method of complex weighted matrix inter-leaving map-ping(CWMIM)is proposed on the basis of the existing suppression scheme of conjugate weighted butterfly interleaving mapping(CWBIM).The proposed scheme performs matrix interleaving map-ping on the transmitted signal,which not only improves the carrier interference ratio(CIR)of the received signal by combining the original IBI and ICI terms,but also further inhibits the probability of burst error in the received signal.Meanwhile,the scheme can further decrease the impact of phase rotation errors in the received signal by increasing the number of rotation factors.Theoretical analysis and simulation results demonstrate that compared with CWBIM-UFMC,the proposed CWMIM-UFMC can obtain more effective ICI and IBI suppression and better system bit error rate(BER)performance with only a little bit increase in computational complexity.展开更多
The Space-Air-Ground-Sea Integrated Networks(SAGSIN)will place higher requirements on both spectral efficiency and security for future maritime communications.To simultaneously address these two challenges,in this pap...The Space-Air-Ground-Sea Integrated Networks(SAGSIN)will place higher requirements on both spectral efficiency and security for future maritime communications.To simultaneously address these two challenges,in this paper,a non-orthogonal modulation based multi-carrier differential chaos shift keying system(namely MCNO-DCSK)is proposed and demonstrated.The most remarkable feature of MCNO-DCSK is that the strict orthogonality between subcarriers is no longer required.In this way,frequency intervals between subcarriers can be much smaller than ever,which leads to a high spectral efficiency.Meanwhile,the frequency interval can be set more flexibly to make the symbol more difficult to be deciphered.Therefore,a high level of security can also be guaranteed.In this design,multiple modulated non-orthogonal subcarriers are sequentially delayed and directly superimposed in time domain to construct the MCNO-DCSK symbol.At the receiver,information bits are demodulated through solving a system of linear equations.The spectral efficiency,computational complexity,and security are analyzed,and the bit-error-rate expressions are derived.Moreover,as subcarriers are non-orthogonal and time delayed,the MCNO-DCSK will suffer severe interference over the multi-path channel.Therefore,the effect of the multi-path interference on the system performance is discussed,and a method to mitigate this interference is designed.Finally,simulation results are provided to verify the theoretical analysis and demonstrate the superiority of MCNO-DCSK.展开更多
On the basis of analyzing the principle of the space-time coding technique and the multi-carrier code division multiple access （MC-CDMA） technique, adopting the turbo codes as channel coding and the optimized comple...On the basis of analyzing the principle of the space-time coding technique and the multi-carrier code division multiple access （MC-CDMA） technique, adopting the turbo codes as channel coding and the optimized complex wavelet packet as multi-carrier modulation, a novel space-time block coded the MC-CDMA system based on complex wavelet packet and turbo coding is proposed, and the system bit error rate （BER） performance in the Rayleigh fading channel is investigated. The system can make full use of space-time block codes＇ transmit diversity and turbo codes＇ good ability against fading channel to improve the BER performance significantly, and it can also avoid the decrease of spectrum efficiency of conventional MC-CDMA due to inserting cyclic prefix （CP） by utilizing superior characteristics of the optimized complex wavelet packet. Simulation results show that the proposed space-time block coded MC-CDMA system based on the complex wavelet packet performs better than the conventional space-time block coded MC-CDMA （STBC-MC-CDMA） system, and slightly outperforms the STBC-MC-CDMA with CP. Moreover, the application of the space-time block coding technique concatenated with turbo codes strengthens the system ability to combat various interferences in fading channel further.展开更多
Recently a Hybrid Carrier （HC） scheme based on Weighted-type Fractional Fourier Transform （WFRFT） was proposed and developed, which contains Single Carrier （SC） and Multi-Carrier （MC） synergetie transmission. ...Recently a Hybrid Carrier （HC） scheme based on Weighted-type Fractional Fourier Transform （WFRFT） was proposed and developed, which contains Single Carrier （SC） and Multi-Carrier （MC） synergetie transmission. The wide interest is primarily due to its appealing characteristics, such as the robust performances in different types of selective fading channels and a great deal of potential for secure communications. According to the literatures, the HC signal and SC or MC signal probability distributions are different. In particular, some benefits of this HC scheme are brought by the quasi-Gaussian distribution of WFRFT signals. However, until now researchers have only presented statistic properties through computer simulations, and the accurate expressions of signals are not derived yet. In this paper, we derive the accu- rate and rigorously established closed-form expressions of Probability Density Function （PDF） of WFRFT signal real and imaginary parts with a large number of QPSK subcarriers, and this PDF can describe the behavior of data modulated by WFRFT, avoiding the complex computation for extensive computer simulations. Furthermore, the components of PDF expression are described and analyzed, and it is revealed that the tendency of signal quasi-Gaussian changes with the increasing of the parameter a （a in （0,1]）. To validate the analytical results, extensive simulations have been conducted, showing a very good match between the analytical results and the real situations. The contribution of this paper may be useful to deduce the closed form expressions of Bit Error Ratio （BER）, the Complementary Cumulative Distribution Function （CCDF） of Peak to Average Power Ratio （PAPR）, and other analytical studies which adopt the PDF.展开更多
Fifth Generation(5G)systems aim to improve flexibility,coexistence and diverse service in several aspects to achieve the emerging applications requirements.Windowing and filtering of the traditional multicarrier wavef...Fifth Generation(5G)systems aim to improve flexibility,coexistence and diverse service in several aspects to achieve the emerging applications requirements.Windowing and filtering of the traditional multicarrier waveforms are now considered common sense when designing more flexible waveforms.This paper proposed a Universal Windowing Multi-Carrier(UWMC)waveform design platform that is flexible,providing more easily coexists with different pulse shapes,and reduces the Out of Band Emissions(OOBE),which is generated by the traditional multicarrier methods that used in the previous generations of the mobile technology.The novel proposed approach is different from other approaches that have been proposed,and it is based on applying a novel modulation approach for the Quadrature-Amplitude Modulation(64-QAM)which is considered very popular in mobile technology.This new approach is done by employing flexible pulse shaping windowing,by assigning windows to various bands.This leads to decreased side-lobes,which are going to reduce OOBE and boost the spectral efficiency by assigning them to edge subscribers only.The new subband windowing(UWMC)will also maintain comprehensively the non-orthogonality by a variety of windowing and make sure to keep window time the same for all subbands.In addition,this paper shows that the new approach made the Bit Error Rate(BER)equal to the conventional Windowed-Orthogonal Frequency Division Multiplexing(W-OFDM).This platform achieved great improvement for some other Key Performance Indicators(KPI),such as the Peak to Average Power Ratio(PAPR)compared with the conventional(W-OFDM)and the conventional Universal Filtered Multicarrier(UFMC)approaches.In particular,the proposed windowing scheme outperforms previous designs in terms of the Power Spectral Density(PSD)by 58%and the(BER)by 1.5 dB and reduces the Complementary Cumulative Distribution Function Cubic Metric(CCDF-CM)by 24%.展开更多
Time-varying frequency selective attenuation and colored noises are unfavorable characteristics of power line communication(PLC) channels of the low voltage networks.To overcome these disadvantages,a novel real-time d...Time-varying frequency selective attenuation and colored noises are unfavorable characteristics of power line communication(PLC) channels of the low voltage networks.To overcome these disadvantages,a novel real-time dynamic spectrum management(DSM) algorithm in orthogonal frequency division multiplexing(OFDM)-based high-speed narrow-band power line communication(HNPLC) systems is proposed,and the corresponding FPGA circuit is designed and realized.Performance of the proposed DSM is validated with a large amount of network experiments under practical PLC circumstance.As the noise in each narrow subcarrier is approximately Gaussian,the proposed DSM adopts the BER/SER expression formulized via the AWGN channel to provide a handy and universal strategy for power allocation.The real-time requirement is guaranteed by choosing subcarriers in group and employing the same modulation scheme within each transmission.These measures are suitable for any modulation scheme no matter the system criterion is to maximize data rate or minimize power/BER.Algorithm design and hardware implementation of the proposed DSM are given with some flexible and efficient conversions.The DSM circuit is carried out with Xilinx KC705.Simulation and practical experiments validate that the proposed real-time DSM significantly improves system performance.展开更多
The use of different energy carriers together,known as an energy hub,has been a hot topic of research in recent years amongst scientists and researchers.The term energy hub refers to the simultaneous operation of vari...The use of different energy carriers together,known as an energy hub,has been a hot topic of research in recent years amongst scientists and researchers.The term energy hub refers to the simultaneous operation of various infrastructures for energy generation and transfer,which has gained momentum in the form of microgrids(MGs).This paper introduces a new strategy for the optimal performance of an MG consisting of different energy carriers for each day.In a smart distribution network(DN),MGs can reduce their own costs in the previous-day market by bidding on sales and purchases.The sales and purchases bidding problem is challenging due to different uncertainties,however.This paper proposes a two-stage strategy for making an optimal bid on electricity sales and purchases with electricity and gas price dependency in the previous-day and real-time markets for an energy hub.In this model,the MG behavior regarding the electricity and gas energy sales/purchase,the simultaneous effects of electricity and gas prices,as well as the energy carriers’dependence on one another are all examined.Due to the inherent uncertainty in the sources of clean energy production,the probabilistic model and the production and reduction scenario have been used in the paper to cover this issue.In the proposed grid,energy sales/purchases are presented in a multi-carrier MG in a two-stage model.This model is solved by using the harmony search algorithm in MATLAB.Numeric results demonstrate the benefits of this model in reducing energy hub costs of operation.展开更多
基金supported in part by the National Key R&D Program of China under Grant 2018YFB1801501in part by the National Natural Science Foundation of China under Grant 62101306supported by OPPO Research Fund。
文摘Terahertz(THz)wireless communication has been recognized as a powerful technology to meet the everincreasing demand of ultra-high rate services.In order to achieve efficient and reliable wireless communications over THz bands,it is extremely necessary to find an appropriate waveform for THz communications.In this paper,performance comparison of various single-carrier and multi-carrier waveforms over THz channels will be provided.Specifically,first,a system model for terahertz communication is briefly described,which includes amplifier nonlinearity,propagation characteristic,phase noise,etc.Then,the transceiver architectures related to both single-carrier and multi-carrier waveforms are presented,as well as their corresponding signal processing techniques.To evaluate the suitability of the waveforms,key performance metrics concerning power efficiency,transmission performance,and computational complexity are provided.Simulation results are provided to compare and validate the performance of different waveforms,which demonstrate the outstanding performance of Discrete-Fourier-Transform spread Orthogonal Frequency Division Multiplexing(DFT-s-OFDM)to THz communications when compared to Cyclic Prefix-OFDM(CP-OFDM)and other single-carrier waveforms.
基金The National Natural Science Foundation of China(No.61271204)the National Key Technology R&D Program during the 12th Five-Year Plan Period(No.2012BAH15B00)
文摘Unlike the existing resonance region radar systems （RRRS ） that transmit the orthogonal frequency division multiplexing （OFDM）multi-carrier waveform,the dense multi-carrier （DMC）radar waveform which has a narrower frequency interval than the traditional OFDM waveform is proposed.Therefore,in the same frequency bandwidth,the DMC waveform contains more sub-carriers and provides more frequency diversity.Additionally,to further improve detection performance,a novel optimal weight accumulation target detection （OWATD）method is proposed,where the echo electromagnetic waves at different frequencies are accumulated with the optimal weight coefficients.Then,with the signal-to-noise ratio （SNR）of echo waveform approaching infinity,the asymptotic detection performance is analyzed, and the condition that the OWATD method with the DMC outperforms the matched filter with the OFDM is presented.Simulation results show that the DMC outperforms the OFDM in the target detection performance,and the OWATD method can further improve the detection performance of the traditional methods with both the OFDM and DMC radar waveform.
基金Project(52108101)supported by the National Natural Science Foundation of ChinaProjects(2020GK4057,2021JJ40759)supported by the Hunan Provincial Science and Technology Department,China。
文摘For the carbon-neutral,a multi-carrier renewable energy system(MRES),driven by the wind,solar and geothermal,was considered as an effective solution to mitigate CO2emissions and reduce energy usage in the building sector.A proper sizing method was essential for achieving the desired 100%renewable energy system of resources.This paper presented a bi-objective optimization formulation for sizing the MRES using a constrained genetic algorithm(GA)coupled with the loss of power supply probability(LPSP)method to achieve the minimal cost of the system and the reliability of the system to the load real time requirement.An optimization App has been developed in MATLAB environment to offer a user-friendly interface and output the optimized design parameters when given the load demand.A case study of a swimming pool building was used to demonstrate the process of the proposed design method.Compared to the conventional distributed energy system,the MRES is feasible with a lower annual total cost(ATC).Additionally,the ATC decreases as the power supply reliability of the renewable system decreases.There is a decrease of 24%of the annual total cost when the power supply probability is equal to 8%compared to the baseline case with 0%power supply probability.
基金Supported by the National Natural Science Foundation of China(No.60172029)
文摘A novel scheme of M-ary multi-carrier spread spectrum based on wavelet packet is proposed. Its performance is investigated for a multipath, slow Rayteigh fading channel. The performance advantages of the system over that based on DFT are demonstrated by both analytical and simulation methods.
基金supported by National Natural Science Foundation of China under Grant No.60972041,60872104Open Research Foundation of National Mobile Communications Research Laboratory,Southeast University under Grant No.N200809+4 种基金Natural Science Fundamental Research Program of Jiangsu Universities under Grant No.08 KJD510001PH.D.Program Foundation of Ministry of Education under Grant No.200802930004National Special Project under Grant No.2009ZX03003-006National Basic Research Program of China under Grant No.2007CB310607Graduate Innovation Program under Grant No.CX10B-186Z
文摘In multi-user wireless communication systems,adaptive modulation and scheduling are promising techniques for increasing system throughput.However,for multi-carrier systems,they will lead to overwhelming user feedback overhead for Channel Quality Indication(CQI) in every subcarrier.In our work,novel CQI feedback schemes are proposed based on the recently proposed theory of Compressive Sensing(CS).First,the standard CS method is introduced to reduce CQI feedback overhead for multi-carrier Multiple-Input Multiple-Output transmission.In addition,via further research on the design of measurement matrix with standard CS,a novel CQI feedback scheme based on subspace CS is proposed by exploiting the subspace information of the underlying signal and the feedback rate is greatly decreased.Simulation results show that,with the same feedback rate,the throughputs with subspace CS outperform the Discrete Cosine Transform(DCT)-based method which is usually employed,and the throughputs with standard CS outperform DCT when the feedback rate is larger than 0.13 bits/subcarrier.
基金supported by the National Natural Science Foundation of China (Grant No.60872114)
文摘To solve the inter carrier interference （ICI） elimination problem of an M-band wavelet multi-carrier modulation system, this paper analyzes the principle of the ICI caused by the Doppler frequency shift and its mathematical expression based on the M-band wavelet multi-carrier modulation system model. Through the analysis of the mathematical expression and combining with the perfect reconstruction conditions of the filter banks, we propose the design conditions of an M-band filter to reduce and eliminate the ICI. The impulse response model of the filter design conditions and an iterative algorithm is also established. The simulation results show that the proposed ICI reduction and elimination methods can effectively improve the system performance.
基金Project supported by Guangdong Innovative and Entrepreneurial Research Team Program(Grant No.2016ZT06D348)Shenzhen Peacock Program(Grant No.KQTD2016022619565991)
文摘Single-layered zirconium pentatelluride （ZrTes） has been predicted to be a large-gap two-dimensional （2D） topolog- ical insulator, which has attracted particular attention in topological phase transitions and potential device applications. Herein, we investigated the transport properties in ZrTe5 films as a function of thickness, ranging from a few nm to several hundred nm. We determined that the temperature of the resistivity anomaly peak （Tp） tends to increase as the thickness decreases. Moreover, at a critical thickness of ~ 40 rim, the dominating carriers in the films change from n-type to p-type. A comprehensive investigation of Shubnikov-de Hass （SdH） oscillations and Hall resistance at variable temperatures revealed a multi-carrier transport tendency in the thin films. We determined the carrier densities and mobilities of two majority car- riers using the simplified two-carrier model. The electron carriers can be attributed to the Dirac band with a non-trivial Berry phase ~, while the hole carriers may originate from surface chemical reaction or unintentional doping during the microfabrication process. It is necessary to encapsulate the ZrTe5 film in an inert or vacuum environment to potentially achieve a substantial improvement in device quality.
基金Supported by the National Natural Science Foundation of China(No.61561031,61562058)the Natural Science Foundation of Gansu Province(No.1508RJZA054)
文摘In order to identify the multi-carrier orthogonal frequency division multiplexing(OFDM) and the single-carrier signal in the non-Gaussian noise environment, different features of the two signals are analyzed in terms of five parameters: generalized normalized fourth-order cumulant, the maximum value of the instantaneous amplitude power spectral density, absolute standard deviation of instantaneous phase on the section with weak signals, and position and numbers of the generalized cyclic spectrum's peak. The recognition method of the multi-carrier OFDM and single-carrier signal is proposed in the environment with alpha-stable distribution noise. Simulation results show that the recognition rate of the multi-carrier OFDM can reach 100% when the mixed signal to noise ratio(MSNR) is greater than-5 dB and the recognition rate can reach 90% for the single-carrier when the MSNR is greater than 2 dB.
基金National Natural Science Foundation of China (60372056)
文摘The parallel interference c an cellation for multi-carrier DS-CDMA (which is termed FDC-PIC) is proposed by integrating frequency diversity combination. The simulations are made over FDC- PIC with respect to different decision ways——hard, soft and linear decisions, respectively, and we conclude that FDC-PIC acquires superior performance improv ement over correlation reception of multi-carrier DS CDMA. With an increase in interference cancellation stages, the system performance is improved further. Th e initial 2 stages bring about the most dominant performance improvement, but up to the 3rd stage the system performance is improved little. It is also shown by the simulation results that FDC-PIC with soft decision would exhibit the best performance with a high implementation complexity, while FDC-PIC with linear de cision acquires performance comparable to that of FDC-PIC with soft decision wi th a reduced-complexity if the number of the interference cancellation stages i s the same, which indicates that FDC-PIC with linear decision has optimal perfo rmance/complexity tradeoff and therefore will be suitable for practical applica tion in future.
文摘The dominate factors caused by reasons of losing the orthogonality in fading channel including FBC (fading branch correlation), CFO (carrier frequency offset), and even the CPN (carrier phase noise) are novel discussion in this letter. The first one factor causes the ISI (inter-symbol interference), and, however, the latter two will lead to the phenomenon of CPE (common phase error) and ICI (inter-carrier interference). On the other hand, they will lead to the loss of orthogonality for the radio system with multi-carrier modulating schemes, i.e., both them mainly deteriorate a wireless communication system. Eventually, in this letter not only the analytical expressions are derived, but a three dimension numerical results from the analysis involve the three parameters also illustrated is.
基金Danish Agency for Science, Technology and Innovation (No. 6144-00037)Danish InnovationFunding (No. 5185-00005A)
文摘Denmark’ goal of being independent of fossil energy sources in 2050 puts forward great demands on all energy subsystems (electricity, heat, gas and transport, etc.) to be operated in a holistic manner. The Danish experience and challenges of wind power integration and the development of district heating systems are summarized in this paper. How to optimally use the cross-sectoral flexibility by intelligent control (model predictive control-based) of the key coupling components in an integrated heat and power system including electrical heat pumps in the demand side, and thermal storage applications in buildings is investigated.
基金Supported by the National Natural Science Foundation of China(No.61601296,61701295)the Science and Technology Innovation ActionPlan Project of Shanghai Science and Technology Commission(No.20511103500)the Talent Program of Shanghai University of Engineer-ing Science(No.2018RC43)。
文摘An interference suppression design scheme based on conjugate weighted butterfly interleaving mapping(CWBIM)is proposed for inter-carrier interference(ICI)and inter-subband interference(IBI)in the received signals of universal filtered multi-carrier(UFMC)systems.It applies an interleaving mapping operation to subtract the interference coefficients of adjacent terms in ICI and IBI twice,thereby achieving suppression effects similar to the self-cancellation(SC)algorithm while maintaining the original data transmission efficiency.Meanwhile,conjugate and complex weighting operations can effectively suppress the impact of phase rotation errors in high-speed mobile channel environments,thereby further improving the bit error rate(BFR)performance of the system,Moreover,butterfly operation can effectively control the computational complexity of the interleaving mapping process.Theoretical analysis and simulation results show that,compared with the PSC-UFMC algorithm,the CWBIM-UFMC scheme proposed in this paper can effectively suppress ICI and IBI in the received signal without compromising data transmission efficiency and reducing computational complexity,thereby achieving good BER performance of the system.
基金Supported by the National Natural Science Foundation of China(No.61601296,61201244)the Science and Technology Innovation Action Plan Project of Shanghai Science and Technology Commission(No.20511103500)the Talent Program of Shanghai University of Engineer-ing Science(No.2018RC43).
文摘In response to the problem of inter-carrier interference(ICI)and inter-subband interference(IBI)in the received signals of universal filtered multi-carrier(UFMC)systems,a novel interfer-ence suppression design scheme applying the method of complex weighted matrix inter-leaving map-ping(CWMIM)is proposed on the basis of the existing suppression scheme of conjugate weighted butterfly interleaving mapping(CWBIM).The proposed scheme performs matrix interleaving map-ping on the transmitted signal,which not only improves the carrier interference ratio(CIR)of the received signal by combining the original IBI and ICI terms,but also further inhibits the probability of burst error in the received signal.Meanwhile,the scheme can further decrease the impact of phase rotation errors in the received signal by increasing the number of rotation factors.Theoretical analysis and simulation results demonstrate that compared with CWBIM-UFMC,the proposed CWMIM-UFMC can obtain more effective ICI and IBI suppression and better system bit error rate(BER)performance with only a little bit increase in computational complexity.
基金supported by the National Key Research and Development Program of China(No.2019YFE0111600)the National Natural Science Foundation of China(Nos.62001077,61801074,61971083,and 51939001)+3 种基金the China Postdoctoral Science Foundation Funded Project(No.2019M661075)the Dalian High Level Talent Innovation Support Plan(No.2021RQ063)the Dalian Science and Technology Innovation Fund(No.2019J11CY015)the Liaoning Revitalization Talents Program(No.XLYC2002078).
文摘The Space-Air-Ground-Sea Integrated Networks(SAGSIN)will place higher requirements on both spectral efficiency and security for future maritime communications.To simultaneously address these two challenges,in this paper,a non-orthogonal modulation based multi-carrier differential chaos shift keying system(namely MCNO-DCSK)is proposed and demonstrated.The most remarkable feature of MCNO-DCSK is that the strict orthogonality between subcarriers is no longer required.In this way,frequency intervals between subcarriers can be much smaller than ever,which leads to a high spectral efficiency.Meanwhile,the frequency interval can be set more flexibly to make the symbol more difficult to be deciphered.Therefore,a high level of security can also be guaranteed.In this design,multiple modulated non-orthogonal subcarriers are sequentially delayed and directly superimposed in time domain to construct the MCNO-DCSK symbol.At the receiver,information bits are demodulated through solving a system of linear equations.The spectral efficiency,computational complexity,and security are analyzed,and the bit-error-rate expressions are derived.Moreover,as subcarriers are non-orthogonal and time delayed,the MCNO-DCSK will suffer severe interference over the multi-path channel.Therefore,the effect of the multi-path interference on the system performance is discussed,and a method to mitigate this interference is designed.Finally,simulation results are provided to verify the theoretical analysis and demonstrate the superiority of MCNO-DCSK.
文摘On the basis of analyzing the principle of the space-time coding technique and the multi-carrier code division multiple access （MC-CDMA） technique, adopting the turbo codes as channel coding and the optimized complex wavelet packet as multi-carrier modulation, a novel space-time block coded the MC-CDMA system based on complex wavelet packet and turbo coding is proposed, and the system bit error rate （BER） performance in the Rayleigh fading channel is investigated. The system can make full use of space-time block codes＇ transmit diversity and turbo codes＇ good ability against fading channel to improve the BER performance significantly, and it can also avoid the decrease of spectrum efficiency of conventional MC-CDMA due to inserting cyclic prefix （CP） by utilizing superior characteristics of the optimized complex wavelet packet. Simulation results show that the proposed space-time block coded MC-CDMA system based on the complex wavelet packet performs better than the conventional space-time block coded MC-CDMA （STBC-MC-CDMA） system, and slightly outperforms the STBC-MC-CDMA with CP. Moreover, the application of the space-time block coding technique concatenated with turbo codes strengthens the system ability to combat various interferences in fading channel further.
基金supported by the National Natural Science Foundation General Program of China(No.61201146)the National Basic Research Program of China(2013CB329003)the Fundamental Research Funds for the Central Universities(HIT.NSRIF.2015022)
文摘Recently a Hybrid Carrier （HC） scheme based on Weighted-type Fractional Fourier Transform （WFRFT） was proposed and developed, which contains Single Carrier （SC） and Multi-Carrier （MC） synergetie transmission. The wide interest is primarily due to its appealing characteristics, such as the robust performances in different types of selective fading channels and a great deal of potential for secure communications. According to the literatures, the HC signal and SC or MC signal probability distributions are different. In particular, some benefits of this HC scheme are brought by the quasi-Gaussian distribution of WFRFT signals. However, until now researchers have only presented statistic properties through computer simulations, and the accurate expressions of signals are not derived yet. In this paper, we derive the accu- rate and rigorously established closed-form expressions of Probability Density Function （PDF） of WFRFT signal real and imaginary parts with a large number of QPSK subcarriers, and this PDF can describe the behavior of data modulated by WFRFT, avoiding the complex computation for extensive computer simulations. Furthermore, the components of PDF expression are described and analyzed, and it is revealed that the tendency of signal quasi-Gaussian changes with the increasing of the parameter a （a in （0,1]）. To validate the analytical results, extensive simulations have been conducted, showing a very good match between the analytical results and the real situations. The contribution of this paper may be useful to deduce the closed form expressions of Bit Error Ratio （BER）, the Complementary Cumulative Distribution Function （CCDF） of Peak to Average Power Ratio （PAPR）, and other analytical studies which adopt the PDF.
基金supported in part by the Ministry of Higher Education Malaysia through the Fundamental Research Grant Scheme(FRGS/1/2019/TK04/UTHM/02/8)the University Tun Hussein Onn Malaysia.
文摘Fifth Generation(5G)systems aim to improve flexibility,coexistence and diverse service in several aspects to achieve the emerging applications requirements.Windowing and filtering of the traditional multicarrier waveforms are now considered common sense when designing more flexible waveforms.This paper proposed a Universal Windowing Multi-Carrier(UWMC)waveform design platform that is flexible,providing more easily coexists with different pulse shapes,and reduces the Out of Band Emissions(OOBE),which is generated by the traditional multicarrier methods that used in the previous generations of the mobile technology.The novel proposed approach is different from other approaches that have been proposed,and it is based on applying a novel modulation approach for the Quadrature-Amplitude Modulation(64-QAM)which is considered very popular in mobile technology.This new approach is done by employing flexible pulse shaping windowing,by assigning windows to various bands.This leads to decreased side-lobes,which are going to reduce OOBE and boost the spectral efficiency by assigning them to edge subscribers only.The new subband windowing(UWMC)will also maintain comprehensively the non-orthogonality by a variety of windowing and make sure to keep window time the same for all subbands.In addition,this paper shows that the new approach made the Bit Error Rate(BER)equal to the conventional Windowed-Orthogonal Frequency Division Multiplexing(W-OFDM).This platform achieved great improvement for some other Key Performance Indicators(KPI),such as the Peak to Average Power Ratio(PAPR)compared with the conventional(W-OFDM)and the conventional Universal Filtered Multicarrier(UFMC)approaches.In particular,the proposed windowing scheme outperforms previous designs in terms of the Power Spectral Density(PSD)by 58%and the(BER)by 1.5 dB and reduces the Complementary Cumulative Distribution Function Cubic Metric(CCDF-CM)by 24%.
基金Supported by the Tsinghua University International Science and Technology Cooperation Project(No.20133000197,20123000148)
文摘Time-varying frequency selective attenuation and colored noises are unfavorable characteristics of power line communication(PLC) channels of the low voltage networks.To overcome these disadvantages,a novel real-time dynamic spectrum management(DSM) algorithm in orthogonal frequency division multiplexing(OFDM)-based high-speed narrow-band power line communication(HNPLC) systems is proposed,and the corresponding FPGA circuit is designed and realized.Performance of the proposed DSM is validated with a large amount of network experiments under practical PLC circumstance.As the noise in each narrow subcarrier is approximately Gaussian,the proposed DSM adopts the BER/SER expression formulized via the AWGN channel to provide a handy and universal strategy for power allocation.The real-time requirement is guaranteed by choosing subcarriers in group and employing the same modulation scheme within each transmission.These measures are suitable for any modulation scheme no matter the system criterion is to maximize data rate or minimize power/BER.Algorithm design and hardware implementation of the proposed DSM are given with some flexible and efficient conversions.The DSM circuit is carried out with Xilinx KC705.Simulation and practical experiments validate that the proposed real-time DSM significantly improves system performance.
基金supported as a Major Project of the Beijing Social Science Foundation“Research on Financial Support System Adapting to the Coordinated Development of Strategic Emerging Industries in Beijing-Tianjin-Hebei”,No.20ZDA11.
文摘The use of different energy carriers together,known as an energy hub,has been a hot topic of research in recent years amongst scientists and researchers.The term energy hub refers to the simultaneous operation of various infrastructures for energy generation and transfer,which has gained momentum in the form of microgrids(MGs).This paper introduces a new strategy for the optimal performance of an MG consisting of different energy carriers for each day.In a smart distribution network(DN),MGs can reduce their own costs in the previous-day market by bidding on sales and purchases.The sales and purchases bidding problem is challenging due to different uncertainties,however.This paper proposes a two-stage strategy for making an optimal bid on electricity sales and purchases with electricity and gas price dependency in the previous-day and real-time markets for an energy hub.In this model,the MG behavior regarding the electricity and gas energy sales/purchase,the simultaneous effects of electricity and gas prices,as well as the energy carriers’dependence on one another are all examined.Due to the inherent uncertainty in the sources of clean energy production,the probabilistic model and the production and reduction scenario have been used in the paper to cover this issue.In the proposed grid,energy sales/purchases are presented in a multi-carrier MG in a two-stage model.This model is solved by using the harmony search algorithm in MATLAB.Numeric results demonstrate the benefits of this model in reducing energy hub costs of operation.
