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
Non Orthogonal Frequency Division Multiplexing (NOFDM) systems make use of a transmission signal set which is not restricted to orthonormal bases unlike previous OFDM systems. The usage of non-orthogonal bases general...Non Orthogonal Frequency Division Multiplexing (NOFDM) systems make use of a transmission signal set which is not restricted to orthonormal bases unlike previous OFDM systems. The usage of non-orthogonal bases generally results in a trade-off between Bit Error Rate (BER) and receiver complexity. This paper studies the use of Gabor based on designing a Spectrally Efficient Multi-Carrier Modulation Scheme. Using Gabor Transform with a specific Gaussian envelope;we derive the expected BER-SNR performance. The spectral usage of such a NOFDM system when affected by a channel that imparts Additive White Gaussian Noise (AWGN) is estimated. We compare the obtained results with an OFDM system and observe that with comparable BER performance, this system gives a better spectral usage. The effect of window length on spectral usage is also analyzed.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
The penetration of multi-carrier energy systems in distribution system gains more and more concerns.In this paper,a bi-level transactive energy trading framework is proposed to improve the energy scheduling and operat...The penetration of multi-carrier energy systems in distribution system gains more and more concerns.In this paper,a bi-level transactive energy trading framework is proposed to improve the energy scheduling and operation efficiency for multi-carrier energy systems which are modeled as energy hubs(EHs).In the upper level,each EH in the distribution system not only makes energy scheduling decisions considering supplies and demands of local energy,but also trades energy with each other to further maximize their social welfare.The associated trading payment among EHs is made in a fair manner by applying Nash bargaining theory.We solve the bargaining problem by decomposing it into two subproblems:operation cost minimization problem and payment bargaining problem.Then,based on the trading decision,the nodal equivalent loads of EHs are sent to the distribution system operator(DSO)without publishing trading details.By applying the second-order cone programming(SOCP),DSO reconfigures the network to reduce the transmission loss of the system in the lower level.The network reconfiguration and the trading behavior of EHs interact and iterate until the convergence.Numerical studies on modified IEEE 33-bus distribution system demonstrate the effectiveness of the proposed framework.展开更多
Discrete Fourier transform-spread generalized multi-carrier （DFT-S-GMC） based single carrier-frequency division multiple access （SC-FDMA） scheme is a promising solution for uplink transmission of broadband wireles...Discrete Fourier transform-spread generalized multi-carrier （DFT-S-GMC） based single carrier-frequency division multiple access （SC-FDMA） scheme is a promising solution for uplink transmission of broadband wireless communication. In this paper, the impact of non-perfect orthogonal prototype filter to the performance of the DFT-S-GMC system is discussed. Single sub-band frequency-domain equalization （FDE） method is presented and the performance loss caused by FDE-tone discarding is analyzed. Moreover, the post-processing signal to interference plus noise ratio （SINR） of DFT-S-GMC receiver over multi-path channel is addressed. The theoretical analysis illustrates that the non-perfect orthogonal prototype filter results in inter-symbol interference （ISI） and inter-sub-band interference （IBI）, and the variance of the ISI is still less than le-4 and much larger than that of IBI. By designing proper system parameters, the reconstruction error due to FDE-tones discarding can be controlled under -40 dB; the post-processing SINR of the DFT-S-GMC receiver with minimum mean square error （MMSE） equalization is higher than that with zero forcing （ZF） equalization. The theoretical performances are verified by extensive simulation results.展开更多
The output of each individual channel in multi-carrier system can be processed to detect moving targets by the approach used in tradition narrowband pulse Doppler（PD） radar and then using non-coherent integration to...The output of each individual channel in multi-carrier system can be processed to detect moving targets by the approach used in tradition narrowband pulse Doppler（PD） radar and then using non-coherent integration to promote signal noise ratio（SNR）. However, due to the difference of Doppler on sub-carriers, there occurs Doppler dispersion during non-coherent integration, which causes attenuation and extension on target＇s amplitude. Especially, it can deteriorate performance of target detection under wideband multicarrier system or fast-moving target scene. In this paper, a modified Fourier transform kernel is proposed to solve Doppler dispersion for multi-carrier chirp signal. It can achieve accumulation at the same frequency point for the target＇s Doppler of each subcarrier. The simulation results indicate that this method can effectively eliminate the integral loss caused by Doppler dispersion.展开更多
A time domain designing method is proposed for discrete Fourier transform （DFT） modulated filter banks （DFT-FBs） for application in multi-carrier transceiver systems. Instead of using the time-reversed pair limita...A time domain designing method is proposed for discrete Fourier transform （DFT） modulated filter banks （DFT-FBs） for application in multi-carrier transceiver systems. Instead of using the time-reversed pair limitation between the transmitting /receiving filter pair, the receiving filters in the proposed filter banks are derived from transmitting filters in accordance with the Moore-Penrose generalized inverse matrix. It can be freely obtained to design the transmitting prototype filter, which mainly affects the level of spectral containment. Furthermore, the symbol error rate （SER） performance of the proposed filter bank based trans-multiplexer with one tap equalizer is investigated in ideal channel and multi-path channel environments respectively. Simulation shows that the proposed approach can achieve significant SER reductions when square root raised cosine （RRC） prototype filter is used for comparing with the orthogonal frequency division multiplexing （OFDM） and the general DFT-FBs based applications.展开更多
Energy storage systems(ESSs)have an assistive role in the operation of multi-carrier energy systems.This paper presents a type of natural gas(NG)ESS called NG tank and studies the operation and flexibility contributio...Energy storage systems(ESSs)have an assistive role in the operation of multi-carrier energy systems.This paper presents a type of natural gas(NG)ESS called NG tank and studies the operation and flexibility contributions of this ESS in the system.NG tank modeling and formulation are unified the same as the electrical ESS.The NG tank and the electrical ESS models are implemented on a large-scale multi-carrier energy network and the impressive effects of utilizing these units are investigated in the operational planning of the energy systems.The optimal operational problem is solved utilizing the teaching learning based optimization(TLBO)algorithm to minimize the operational cost of the system.展开更多
Fluctuating polarization state-of-light in the optical loop is an important factor that seriously influences the output performance of a multi-carrier source based on re-circulating frequency shifter （RFS）. The reas...Fluctuating polarization state-of-light in the optical loop is an important factor that seriously influences the output performance of a multi-carrier source based on re-circulating frequency shifter （RFS）. The reason for output spectrum instability when no polarization controller （PC） is present in the loop is analyzed theoretically. Numerical simulations for the output spectra of the multi-carrier source with and without PC are conducted, and the trajectories of the several frequency components polarization states on the Poincare sphere with and without PC are compared. The results show that the performance of multi-carrier source based on a RFS can be improved effectively by adjusting the PC in the configuration properly.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.
文摘Non Orthogonal Frequency Division Multiplexing (NOFDM) systems make use of a transmission signal set which is not restricted to orthonormal bases unlike previous OFDM systems. The usage of non-orthogonal bases generally results in a trade-off between Bit Error Rate (BER) and receiver complexity. This paper studies the use of Gabor based on designing a Spectrally Efficient Multi-Carrier Modulation Scheme. Using Gabor Transform with a specific Gaussian envelope;we derive the expected BER-SNR performance. The spectral usage of such a NOFDM system when affected by a channel that imparts Additive White Gaussian Noise (AWGN) is estimated. We compare the obtained results with an OFDM system and observe that with comparable BER performance, this system gives a better spectral usage. The effect of window length on spectral usage is also analyzed.
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The penetration of multi-carrier energy systems in distribution system gains more and more concerns.In this paper,a bi-level transactive energy trading framework is proposed to improve the energy scheduling and operation efficiency for multi-carrier energy systems which are modeled as energy hubs(EHs).In the upper level,each EH in the distribution system not only makes energy scheduling decisions considering supplies and demands of local energy,but also trades energy with each other to further maximize their social welfare.The associated trading payment among EHs is made in a fair manner by applying Nash bargaining theory.We solve the bargaining problem by decomposing it into two subproblems:operation cost minimization problem and payment bargaining problem.Then,based on the trading decision,the nodal equivalent loads of EHs are sent to the distribution system operator(DSO)without publishing trading details.By applying the second-order cone programming(SOCP),DSO reconfigures the network to reduce the transmission loss of the system in the lower level.The network reconfiguration and the trading behavior of EHs interact and iterate until the convergence.Numerical studies on modified IEEE 33-bus distribution system demonstrate the effectiveness of the proposed framework.
基金Supported by the National High-Tech Research & Development Program of China (Grant No. 2006AA01Z280)the National Key Project of China during the 11th Five-Year Plan Period (Grant No. 2009ZX03003-006-03)
文摘Discrete Fourier transform-spread generalized multi-carrier （DFT-S-GMC） based single carrier-frequency division multiple access （SC-FDMA） scheme is a promising solution for uplink transmission of broadband wireless communication. In this paper, the impact of non-perfect orthogonal prototype filter to the performance of the DFT-S-GMC system is discussed. Single sub-band frequency-domain equalization （FDE） method is presented and the performance loss caused by FDE-tone discarding is analyzed. Moreover, the post-processing signal to interference plus noise ratio （SINR） of DFT-S-GMC receiver over multi-path channel is addressed. The theoretical analysis illustrates that the non-perfect orthogonal prototype filter results in inter-symbol interference （ISI） and inter-sub-band interference （IBI）, and the variance of the ISI is still less than le-4 and much larger than that of IBI. By designing proper system parameters, the reconstruction error due to FDE-tones discarding can be controlled under -40 dB; the post-processing SINR of the DFT-S-GMC receiver with minimum mean square error （MMSE） equalization is higher than that with zero forcing （ZF） equalization. The theoretical performances are verified by extensive simulation results.
基金supported by the National Natural Science Foundation of China (61371107, 61362006)the Foundation of Key Lab. of Guangxi Broadband Wireless Communication & Signal Processing (GXKL061501)+1 种基金the Guangxi Natural Science Foundation (2014GXNSFBA118288)the Science and Technology on Information Transmission and Dissemination in Communication Networks Lab
文摘The output of each individual channel in multi-carrier system can be processed to detect moving targets by the approach used in tradition narrowband pulse Doppler（PD） radar and then using non-coherent integration to promote signal noise ratio（SNR）. However, due to the difference of Doppler on sub-carriers, there occurs Doppler dispersion during non-coherent integration, which causes attenuation and extension on target＇s amplitude. Especially, it can deteriorate performance of target detection under wideband multicarrier system or fast-moving target scene. In this paper, a modified Fourier transform kernel is proposed to solve Doppler dispersion for multi-carrier chirp signal. It can achieve accumulation at the same frequency point for the target＇s Doppler of each subcarrier. The simulation results indicate that this method can effectively eliminate the integral loss caused by Doppler dispersion.
基金supported by Young Scientists Fund of Chongqing University of Posts and Telecommunications(A2013-32)
文摘A time domain designing method is proposed for discrete Fourier transform （DFT） modulated filter banks （DFT-FBs） for application in multi-carrier transceiver systems. Instead of using the time-reversed pair limitation between the transmitting /receiving filter pair, the receiving filters in the proposed filter banks are derived from transmitting filters in accordance with the Moore-Penrose generalized inverse matrix. It can be freely obtained to design the transmitting prototype filter, which mainly affects the level of spectral containment. Furthermore, the symbol error rate （SER） performance of the proposed filter bank based trans-multiplexer with one tap equalizer is investigated in ideal channel and multi-path channel environments respectively. Simulation shows that the proposed approach can achieve significant SER reductions when square root raised cosine （RRC） prototype filter is used for comparing with the orthogonal frequency division multiplexing （OFDM） and the general DFT-FBs based applications.
文摘Energy storage systems(ESSs)have an assistive role in the operation of multi-carrier energy systems.This paper presents a type of natural gas(NG)ESS called NG tank and studies the operation and flexibility contributions of this ESS in the system.NG tank modeling and formulation are unified the same as the electrical ESS.The NG tank and the electrical ESS models are implemented on a large-scale multi-carrier energy network and the impressive effects of utilizing these units are investigated in the operational planning of the energy systems.The optimal operational problem is solved utilizing the teaching learning based optimization(TLBO)algorithm to minimize the operational cost of the system.
基金supported by the Chinese Universities Scientific Fund (No. BUPT 2011RC009)the BUPT Excellent Ph.D. Students Foundation (No. CX201121)the Research Fund for the Doctoral Program of Higher Education (No. 20110005110014)
文摘Fluctuating polarization state-of-light in the optical loop is an important factor that seriously influences the output performance of a multi-carrier source based on re-circulating frequency shifter （RFS）. The reason for output spectrum instability when no polarization controller （PC） is present in the loop is analyzed theoretically. Numerical simulations for the output spectra of the multi-carrier source with and without PC are conducted, and the trajectories of the several frequency components polarization states on the Poincare sphere with and without PC are compared. The results show that the performance of multi-carrier source based on a RFS can be improved effectively by adjusting the PC in the configuration properly.
