Electrochemical CO_(2)reduction to C_(2)H_(4)can provide a sustainable route to reduce globally accelerating CO_(2)emissions and produce energy-rich chemical feedstocks.However,the poor selectivity in C_(2)H_(4)electr...Electrochemical CO_(2)reduction to C_(2)H_(4)can provide a sustainable route to reduce globally accelerating CO_(2)emissions and produce energy-rich chemical feedstocks.However,the poor selectivity in C_(2)H_(4)electrosynthesis limits its implementation in industrially interesting processes.Herein,we report a composite structured catalyst composed of Ag and Cu_(2)O with different crystal faces to achieve highly efficient reduction of CO_(2)to C_(2)H_(4).The catalyst composed of Ag and octahedral Cu_(2)O enclosed with(111)facet exhibits the best CO_(2)electroreduction performance,with the Faradaic efficiency(FE)and partial current density reaching 66.8%and 17.8 mA cm2 for C_(2)H_(4)product at-1.2 VRHE in 0.5 M KHCO_(3),respectively.Physical characterization and electrochemical test analysis indicate that the high selectivity for C_(2)H_(4)product stems from the synergistic effect of crystal faces control engineering and tandem catalysis.Specifically,Ag can provide optimal availability of CO intermediate by suppressing hydrogen evolution;subsequently,C-C coupling is promoted on the intimate surface of Cu_(2)O with facetdependent selectivity.The insights gained from this work may be beneficial for designing efficient multicomponent catalysts for improving the selectivity of electrochemical CO_(2)reduction reaction to generate C2þproducts.展开更多
In this study,we used a simple impregnation method to prepare Fe-Ce-O_x catalysts and tested them regarding their low-temperature(200-300 ℃) selective catalytic reduction(SCR) of NO using NH_3.We investigated the eff...In this study,we used a simple impregnation method to prepare Fe-Ce-O_x catalysts and tested them regarding their low-temperature(200-300 ℃) selective catalytic reduction(SCR) of NO using NH_3.We investigated the effects of Fe/Ce molar ratio,the gas hourly space velocity(GHSV),the stability and SO_2/H_2O resistance of the catalysts.The results showed that the FeCe(1:6)O_x(Ce/Fe molar ratio is 1:6) catalyst,which has some ordered parallel channels,exhibited good SCR performance.The FeCe(1:6)O_x catalyst had the highest NO conversion with an activity of 94-99%at temperatures between 200 and300 ℃ at a space velocity of 28,800 h^(-1).The NO conversion for the FeCe(1:6)O_x catalyst also reached 80-98%between 200 and 300 ℃ at a space velocity of204,000h^(-1).In addition,the FeCe(1:6)O_x catalyst demonstrated good stability in a 10-h SCR reaction at200-300 ℃.Even in the presence of SO_2 and H_2O,the FeCe(1:6)O_x catalyst exhibited good SCR performance.展开更多
Monolithic catalysts of Pt/La-Al2O3 and Pt/Ce0.67Zr0.3302 were prepared to investigate methane selective catalytic reduction (SCR) of NO. The results indicate that Pt/Ce0.67Zr0.33O2 shows high activity and both NO a...Monolithic catalysts of Pt/La-Al2O3 and Pt/Ce0.67Zr0.3302 were prepared to investigate methane selective catalytic reduction (SCR) of NO. The results indicate that Pt/Ce0.67Zr0.33O2 shows high activity and both NO and CH4 can be converted completely at 450℃. Meanwhile, NO and CH4 can be converted completely when there exists excess oxygen. The Pt/Ce0.67Zr0.33O2 catalyst were further investigated by using methane as reducing agent to SCR NO in a novel equipment which combined the CH4 selective catalytic reduction of NO with methane combustion. The result shows that the catalyst is high active and the novel equipment is very effective. The conversion of NO is above 92% under the conditions used in this work. The prepared burner and catalysts have great potential for application.展开更多
DBUH-Br_3 catalyzed selective conversion of sulfides to sulfoxides in the presence of H_2O_2 as oxidizing agent is described.The reaction was performed selectively at room temperature and relatively short reaction times.
Selective laser sintering (SLS) is a new process to prepare the polystyrene (PS)/Al2O3 nanocomposites. In this paper, with different laser power and other processing parameters unchanged, the morphology, density a...Selective laser sintering (SLS) is a new process to prepare the polystyrene (PS)/Al2O3 nanocomposites. In this paper, with different laser power and other processing parameters unchanged, the morphology, density and mechanical properties of the sintered specimens were investigated. It was found that nano-sized inorganic particles are uniformly located in the PS matrix and the maximum density of the sintered specimens with pure PS powder reaches 1.07 g/cm^3, higher than 1.04 g/cm^3 that of the sintered specimens with mixture powder. Due to strengthening and toughness of the nano-sized Al2O3 inorganic particles, the maximum notched impact strength and tensile strength of the sintered part mixed with nano-sized inorganic particles are improved greatly from 7.5 to 12.1 kJ/m^2 and from 6.5 to 31.2 MPa, respectively, under the same sintering condition.展开更多
The selective catalytic oxidation of toluene with hydrogen peroxide over V-Mo-based catalysts under mild conditions was studied.The promotion effect of Mo on the catalysts was studied with V/Al2O3 and Mo/Al2O3 as refe...The selective catalytic oxidation of toluene with hydrogen peroxide over V-Mo-based catalysts under mild conditions was studied.The promotion effect of Mo on the catalysts was studied with V/Al2O3 and Mo/Al2O3 as reference samples.The catalysts were characterized by XRD,TPR,and XPS techniques.The results show that the addition of Mo to V/Al2O3 may change the distribution of V species on Al2O3 surface.Over V-Mo/Al2O3 catalyst,highly dispersed amorphous V species facilitates benzaldehyde formation,and crystalline V2O5 species increases the conversion of toluene but decreases the selectivity to benzaldehyde,while AlVMoO7 species favors both the conversion of toluene and the formation of cresols.The yield of benzaldehyde depends remarkably on the surface O/Al and Mo/V atomic ratios,and gets to a maximum value of 13.2% with a selectivity of 79.5% at an O/Al atomic ratio of 3.0 and Mo/V atomic ratio of 0.7.展开更多
To improve the denitrification performance of carbon-based materials for sintering flue gas,we prepared a composite catalyst comprising coconut shell activated carbon(AC)modified by thermal oxidation air.The microstru...To improve the denitrification performance of carbon-based materials for sintering flue gas,we prepared a composite catalyst comprising coconut shell activated carbon(AC)modified by thermal oxidation air.The microstructure,the specific surface area,the pore volume,the crystal structure,and functional groups presented in the prepared Cu2O/AC catalysts were thoroughly characterized.By using scanning electron microscopy(SEM),nitrogen adsorption/desorption isotherms,Fourier-transform infrared(FTIR)spectroscopy and X-ray diffractometry(XRD),the effects of Cu2O loading and calcination temperature on Cu2O/AC catalysts were investigated at low temperature(150℃).The research shows that Cu on the Cu2O/AC catalyst is in the form of Cu2O with good crystalline performance and is spherical and uniformly dispersed on the AC surface.The loading of Cu2O increases the active sites and the specific surface area of the reaction gas contact,which is conducive to the rapid progress of the carbon monoxide selective catalytic reduction(CO-SCR)reaction.When the loading of Cu2O was 8%and the calcination temperature was 500℃,the removal rate of NOx facilitated by the Cu2O/AC catalyst reached 97.9%.These findings provide a theoretical basis for understanding the denitrification of sintering flue gas.展开更多
This work studied CuO/CeO2-Co3O4 with wt% Ce:Co ratio 95:5 for selective CO oxidation with effect of? wt% Cu loading. The catalysts were prepared by co-precipitation. Characterizations of catalysts were carried out by...This work studied CuO/CeO2-Co3O4 with wt% Ce:Co ratio 95:5 for selective CO oxidation with effect of? wt% Cu loading. The catalysts were prepared by co-precipitation. Characterizations of catalysts were carried out by XRD and BET techniques. The results showed a good dispersion of CuO for 5 wt% Cu loading catalysts and showed high specific surface area of catalyst. For selective CO oxidation, both 5CuO and 30CuO catalysts could remove completely CO in the presence of excess hydrogen at 423 K and 20CuO could eliminate CO completely at 443 K. Moreover, considering the selectivity to CO oxidation, the 5CuO catalyst has shown the highest selectivity of 85% while the 30CuO catalyst obtains the selectivity of 65% at the reaction temperature of 423 K.展开更多
The Cu-Zr-Ce-O catalysts prepared using the coprecipitation method exhibited better catalytic performance for CO selective oxidation. The Cu-Zr-Ce-O catalysts pretreated with different methods were studied by CO-TPR a...The Cu-Zr-Ce-O catalysts prepared using the coprecipitation method exhibited better catalytic performance for CO selective oxidation. The Cu-Zr-Ce-O catalysts pretreated with different methods were studied by CO-TPR and XPS techniques. The results showed that the Cu-Zr-Ce-O catalyst pretreated with oxygen exhibited the best catalytic performance and had the widest operating temperature window, with CO conversion above 99% from 160 to 200 ℃. The O2 pretreatment caused an enrichment of the oxygen storaged on the Cu active species and promoted the conversion of adsorbed oxygen into surface lattice oxygen. It also improved the amount of Cu+/Cu^2+ ionic pair, and then facilitated the formation of CuO active species on the catalyst for selective CO oxidation.展开更多
In this paper,using cyclostationarity-based sensing method to detect the presence of Orthogonal Frequency Division Multiplexing(OFDM) signal over doubly-selective fading channels is studied.By approximating the channe...In this paper,using cyclostationarity-based sensing method to detect the presence of Orthogonal Frequency Division Multiplexing(OFDM) signal over doubly-selective fading channels is studied.By approximating the channel with Basis Expansion Model(BEM),we derive the second-order cyclostationary statistics of the received OFDM signal over doubly-selective fading channels.Theoretical analysis indicates that new cyclostationary signatures produced by Doppler spread and multipath delay can be further exploited in the detecting process.Simulation examples demonstrate that the sensing methods using channel-induced cyclostationary features provide substantial improvements on detection performance.展开更多
Comparatively high CH3OH selectivity (60.0%) and yield (6.7%) were obtained on MoOx/(LaCoO3+Co3O4) catalysts in selective oxidation of methane to methanol using molecular oxygen as oxidant. The interaction between MoO...Comparatively high CH3OH selectivity (60.0%) and yield (6.7%) were obtained on MoOx/(LaCoO3+Co3O4) catalysts in selective oxidation of methane to methanol using molecular oxygen as oxidant. The interaction between MoOx and La-Co-oxide modified the molecular structure of molybdenum oxide and the ratio of O7O ' on the catalyst surface, which controlled the catalytic performance of MoOx/(LaCoO3+Co3O4) catalysts.展开更多
In order to reduce the cost of Radio Frequency (RF) chains in the spatial multiplexing systems with Vertical-Bell Labs Layered Space-Time (V-BLAST) nonlinear receiver, a novel transmit antenna selection cri-terion is ...In order to reduce the cost of Radio Frequency (RF) chains in the spatial multiplexing systems with Vertical-Bell Labs Layered Space-Time (V-BLAST) nonlinear receiver, a novel transmit antenna selection cri-terion is proposed with the motivation of minimizing the Vector Symbol Error Rate (VSER). In the proposed scheme, both the number of substreams and the mapping of substreams to antennas are dynamically adjusted based on the knowledge of channel. Simulation results illustrate that the proposed two-step selection criterion outperforms the existing eigenmode based selection criterion by 0.3dB at a VSER of 10?3.展开更多
In doubly-selective fading wireless channel,the conventional orthogonal frequency division multi-plexing(OFDM)receivers for inter-carrier interference(ICI)compensation require extensive computa-tions.To obtain an effe...In doubly-selective fading wireless channel,the conventional orthogonal frequency division multi-plexing(OFDM)receivers for inter-carrier interference(ICI)compensation require extensive computa-tions.To obtain an effective balance between performance and complexity,the whole channel responsematrix was decomposed into a sequence of submatrix,and then a novel equalizer based on minimum meansquare error(MMSE)criterion was presented to combat the ICI.Furthermore,a simple ordering-baseddecision-feedback equalizer(DFE)was derived to exploit the temperal diversity gain offered by mobilechannels.Numerical studies illustrate that although the MMSE equalizer still suffers from error floor,whereas the DFE equalizer exhibits significant performance improvement.The advantage of the proposedscheme indicates its potential applications in the future broadband wireless systems.展开更多
Orthogonal frequency division multiplexing-interleave division multiple access (OFDM-IDMA) systems may suffer from serious inter-carrier interference (ICI) in time-and frequency-selective (doubly selective) channels. ...Orthogonal frequency division multiplexing-interleave division multiple access (OFDM-IDMA) systems may suffer from serious inter-carrier interference (ICI) in time-and frequency-selective (doubly selective) channels. In such case, the conventional OFDM-IDMA detection algorithm for quasi-static channels will result in significantly performance degradation. In this paper, signal detection is investigated for OFDM-IDMA uplink over doubly selective channels. Firstly, the impact of time-varying channels for OFDM-IDMA uplink is analyzed, which leads to the failure of the conventional algorithm. Secondly, a novel iterative detection algorithm is developed based on an integrated interference canceller, which can iteratively estimate and mitigate the ICI as well as multiple access interference (MAI) simultaneously. In addition, an improved detection algorithm is derived for reducing the complexity using an approximation to the mean and variance of the interference. Simulation results indicate that the proposed algorithm can significantly enhance the system performance to the conventional case, and the improved algorithm can strike a balance between performance and complexity.展开更多
近年来,高速移动通信受到业界的广泛关注,其中接收机侧的信道估计直接决定了系统的通信质量。正交频分复用(orthogonal frequency division multiplexing,OFDM)以其高带宽效率和抗多径衰落的特性,在目前的无线通信中被广泛采用。综述了...近年来,高速移动通信受到业界的广泛关注,其中接收机侧的信道估计直接决定了系统的通信质量。正交频分复用(orthogonal frequency division multiplexing,OFDM)以其高带宽效率和抗多径衰落的特性,在目前的无线通信中被广泛采用。综述了高速移动场景下OFDM系统信道估计方法;描述了OFDM的系统模型;分析了高速移动场景下信道的时间/频率选择性衰落特性(双选特性)和稀疏特性。基于深度学习和压缩感知的信道估计方法,其高精度和低复杂度被用于高速移动场景,该文分别对基于深度学习和压缩感知的信道估计算法进行了归纳、对比、分析,探讨了高速移动场景下信道估计的发展趋势。展开更多
基金This work was supported by the University of Science and Technology Beijing.DG acknowledges the financial support from 111 Project(no.B170003)Foshan Science and Technology Innovation Project(no.2018IT100363).
文摘Electrochemical CO_(2)reduction to C_(2)H_(4)can provide a sustainable route to reduce globally accelerating CO_(2)emissions and produce energy-rich chemical feedstocks.However,the poor selectivity in C_(2)H_(4)electrosynthesis limits its implementation in industrially interesting processes.Herein,we report a composite structured catalyst composed of Ag and Cu_(2)O with different crystal faces to achieve highly efficient reduction of CO_(2)to C_(2)H_(4).The catalyst composed of Ag and octahedral Cu_(2)O enclosed with(111)facet exhibits the best CO_(2)electroreduction performance,with the Faradaic efficiency(FE)and partial current density reaching 66.8%and 17.8 mA cm2 for C_(2)H_(4)product at-1.2 VRHE in 0.5 M KHCO_(3),respectively.Physical characterization and electrochemical test analysis indicate that the high selectivity for C_(2)H_(4)product stems from the synergistic effect of crystal faces control engineering and tandem catalysis.Specifically,Ag can provide optimal availability of CO intermediate by suppressing hydrogen evolution;subsequently,C-C coupling is promoted on the intimate surface of Cu_(2)O with facetdependent selectivity.The insights gained from this work may be beneficial for designing efficient multicomponent catalysts for improving the selectivity of electrochemical CO_(2)reduction reaction to generate C2þproducts.
基金supported by the National Natural Science Foundation of China (No.21206108)Tianjin Municipal Science and Technology Commission (No.14JCYBJC21200)
文摘In this study,we used a simple impregnation method to prepare Fe-Ce-O_x catalysts and tested them regarding their low-temperature(200-300 ℃) selective catalytic reduction(SCR) of NO using NH_3.We investigated the effects of Fe/Ce molar ratio,the gas hourly space velocity(GHSV),the stability and SO_2/H_2O resistance of the catalysts.The results showed that the FeCe(1:6)O_x(Ce/Fe molar ratio is 1:6) catalyst,which has some ordered parallel channels,exhibited good SCR performance.The FeCe(1:6)O_x catalyst had the highest NO conversion with an activity of 94-99%at temperatures between 200 and300 ℃ at a space velocity of 28,800 h^(-1).The NO conversion for the FeCe(1:6)O_x catalyst also reached 80-98%between 200 and 300 ℃ at a space velocity of204,000h^(-1).In addition,the FeCe(1:6)O_x catalyst demonstrated good stability in a 10-h SCR reaction at200-300 ℃.Even in the presence of SO_2 and H_2O,the FeCe(1:6)O_x catalyst exhibited good SCR performance.
基金Supported by the National High Technology Research and Development Program of China (863 Program, 2006AA06Z347)the NationalNatural Science Foundation of China (20773090).
文摘Monolithic catalysts of Pt/La-Al2O3 and Pt/Ce0.67Zr0.3302 were prepared to investigate methane selective catalytic reduction (SCR) of NO. The results indicate that Pt/Ce0.67Zr0.33O2 shows high activity and both NO and CH4 can be converted completely at 450℃. Meanwhile, NO and CH4 can be converted completely when there exists excess oxygen. The Pt/Ce0.67Zr0.33O2 catalyst were further investigated by using methane as reducing agent to SCR NO in a novel equipment which combined the CH4 selective catalytic reduction of NO with methane combustion. The result shows that the catalyst is high active and the novel equipment is very effective. The conversion of NO is above 92% under the conditions used in this work. The prepared burner and catalysts have great potential for application.
文摘DBUH-Br_3 catalyzed selective conversion of sulfides to sulfoxides in the presence of H_2O_2 as oxidizing agent is described.The reaction was performed selectively at room temperature and relatively short reaction times.
文摘Selective laser sintering (SLS) is a new process to prepare the polystyrene (PS)/Al2O3 nanocomposites. In this paper, with different laser power and other processing parameters unchanged, the morphology, density and mechanical properties of the sintered specimens were investigated. It was found that nano-sized inorganic particles are uniformly located in the PS matrix and the maximum density of the sintered specimens with pure PS powder reaches 1.07 g/cm^3, higher than 1.04 g/cm^3 that of the sintered specimens with mixture powder. Due to strengthening and toughness of the nano-sized Al2O3 inorganic particles, the maximum notched impact strength and tensile strength of the sintered part mixed with nano-sized inorganic particles are improved greatly from 7.5 to 12.1 kJ/m^2 and from 6.5 to 31.2 MPa, respectively, under the same sintering condition.
基金Supported by the National Natural Science Foundation of China(Nos.20502017and20072024)the Teaching and ResearchAward Program for Outstanding Young Teachers in Higher Education Institutions of Ministry of Education,Chinathe ScienceFoundation for Young Teachers of Sichuan University.
文摘The selective catalytic oxidation of toluene with hydrogen peroxide over V-Mo-based catalysts under mild conditions was studied.The promotion effect of Mo on the catalysts was studied with V/Al2O3 and Mo/Al2O3 as reference samples.The catalysts were characterized by XRD,TPR,and XPS techniques.The results show that the addition of Mo to V/Al2O3 may change the distribution of V species on Al2O3 surface.Over V-Mo/Al2O3 catalyst,highly dispersed amorphous V species facilitates benzaldehyde formation,and crystalline V2O5 species increases the conversion of toluene but decreases the selectivity to benzaldehyde,while AlVMoO7 species favors both the conversion of toluene and the formation of cresols.The yield of benzaldehyde depends remarkably on the surface O/Al and Mo/V atomic ratios,and gets to a maximum value of 13.2% with a selectivity of 79.5% at an O/Al atomic ratio of 3.0 and Mo/V atomic ratio of 0.7.
基金Open Fund of Key Laboratory of Ministry of Education for Metallurgical Emission Reduction and Comprehensive Utilization of Resources,China(No.JKF19-08)General Project of Science and Technology Plan of Yunnan Science and Technology Department,China(No.2019FB077)+1 种基金Industrialization Cultivation Project of Scientific Research Fund of Yunnan Provincial Department of Education,China(No.2016CYH07)Top Young Talents of Yunnan Ten Thousand Talents Plan,China(No.YNWR-QNBJ-2019-263)。
文摘To improve the denitrification performance of carbon-based materials for sintering flue gas,we prepared a composite catalyst comprising coconut shell activated carbon(AC)modified by thermal oxidation air.The microstructure,the specific surface area,the pore volume,the crystal structure,and functional groups presented in the prepared Cu2O/AC catalysts were thoroughly characterized.By using scanning electron microscopy(SEM),nitrogen adsorption/desorption isotherms,Fourier-transform infrared(FTIR)spectroscopy and X-ray diffractometry(XRD),the effects of Cu2O loading and calcination temperature on Cu2O/AC catalysts were investigated at low temperature(150℃).The research shows that Cu on the Cu2O/AC catalyst is in the form of Cu2O with good crystalline performance and is spherical and uniformly dispersed on the AC surface.The loading of Cu2O increases the active sites and the specific surface area of the reaction gas contact,which is conducive to the rapid progress of the carbon monoxide selective catalytic reduction(CO-SCR)reaction.When the loading of Cu2O was 8%and the calcination temperature was 500℃,the removal rate of NOx facilitated by the Cu2O/AC catalyst reached 97.9%.These findings provide a theoretical basis for understanding the denitrification of sintering flue gas.
文摘This work studied CuO/CeO2-Co3O4 with wt% Ce:Co ratio 95:5 for selective CO oxidation with effect of? wt% Cu loading. The catalysts were prepared by co-precipitation. Characterizations of catalysts were carried out by XRD and BET techniques. The results showed a good dispersion of CuO for 5 wt% Cu loading catalysts and showed high specific surface area of catalyst. For selective CO oxidation, both 5CuO and 30CuO catalysts could remove completely CO in the presence of excess hydrogen at 423 K and 20CuO could eliminate CO completely at 443 K. Moreover, considering the selectivity to CO oxidation, the 5CuO catalyst has shown the highest selectivity of 85% while the 30CuO catalyst obtains the selectivity of 65% at the reaction temperature of 423 K.
基金supported by the National Nature Science Foundation of China (Project No.20576023)the Natural Science Foundation of Guangdong Province (Project No.06025660).
文摘The Cu-Zr-Ce-O catalysts prepared using the coprecipitation method exhibited better catalytic performance for CO selective oxidation. The Cu-Zr-Ce-O catalysts pretreated with different methods were studied by CO-TPR and XPS techniques. The results showed that the Cu-Zr-Ce-O catalyst pretreated with oxygen exhibited the best catalytic performance and had the widest operating temperature window, with CO conversion above 99% from 160 to 200 ℃. The O2 pretreatment caused an enrichment of the oxygen storaged on the Cu active species and promoted the conversion of adsorbed oxygen into surface lattice oxygen. It also improved the amount of Cu+/Cu^2+ ionic pair, and then facilitated the formation of CuO active species on the catalyst for selective CO oxidation.
基金Supported by the National Natural Science Foundation of China(No.61002017 and No.61072076)the STCSM and Shanghai Rising-Star Program(10JC1414400)
文摘In this paper,using cyclostationarity-based sensing method to detect the presence of Orthogonal Frequency Division Multiplexing(OFDM) signal over doubly-selective fading channels is studied.By approximating the channel with Basis Expansion Model(BEM),we derive the second-order cyclostationary statistics of the received OFDM signal over doubly-selective fading channels.Theoretical analysis indicates that new cyclostationary signatures produced by Doppler spread and multipath delay can be further exploited in the detecting process.Simulation examples demonstrate that the sensing methods using channel-induced cyclostationary features provide substantial improvements on detection performance.
基金supported by the State Key Fundamental Research Development Project(G1999022404)
文摘Comparatively high CH3OH selectivity (60.0%) and yield (6.7%) were obtained on MoOx/(LaCoO3+Co3O4) catalysts in selective oxidation of methane to methanol using molecular oxygen as oxidant. The interaction between MoOx and La-Co-oxide modified the molecular structure of molybdenum oxide and the ratio of O7O ' on the catalyst surface, which controlled the catalytic performance of MoOx/(LaCoO3+Co3O4) catalysts.
基金Supported by the National Natural Science Foundation of China (No.60372055) and the National High Tech-nology Research and Development (863) Project of China (No.2003AA123320).
文摘In order to reduce the cost of Radio Frequency (RF) chains in the spatial multiplexing systems with Vertical-Bell Labs Layered Space-Time (V-BLAST) nonlinear receiver, a novel transmit antenna selection cri-terion is proposed with the motivation of minimizing the Vector Symbol Error Rate (VSER). In the proposed scheme, both the number of substreams and the mapping of substreams to antennas are dynamically adjusted based on the knowledge of channel. Simulation results illustrate that the proposed two-step selection criterion outperforms the existing eigenmode based selection criterion by 0.3dB at a VSER of 10?3.
基金Supported by the National Natural Science Foundation of China (No. 60573112)
文摘In doubly-selective fading wireless channel,the conventional orthogonal frequency division multi-plexing(OFDM)receivers for inter-carrier interference(ICI)compensation require extensive computa-tions.To obtain an effective balance between performance and complexity,the whole channel responsematrix was decomposed into a sequence of submatrix,and then a novel equalizer based on minimum meansquare error(MMSE)criterion was presented to combat the ICI.Furthermore,a simple ordering-baseddecision-feedback equalizer(DFE)was derived to exploit the temperal diversity gain offered by mobilechannels.Numerical studies illustrate that although the MMSE equalizer still suffers from error floor,whereas the DFE equalizer exhibits significant performance improvement.The advantage of the proposedscheme indicates its potential applications in the future broadband wireless systems.
文摘Orthogonal frequency division multiplexing-interleave division multiple access (OFDM-IDMA) systems may suffer from serious inter-carrier interference (ICI) in time-and frequency-selective (doubly selective) channels. In such case, the conventional OFDM-IDMA detection algorithm for quasi-static channels will result in significantly performance degradation. In this paper, signal detection is investigated for OFDM-IDMA uplink over doubly selective channels. Firstly, the impact of time-varying channels for OFDM-IDMA uplink is analyzed, which leads to the failure of the conventional algorithm. Secondly, a novel iterative detection algorithm is developed based on an integrated interference canceller, which can iteratively estimate and mitigate the ICI as well as multiple access interference (MAI) simultaneously. In addition, an improved detection algorithm is derived for reducing the complexity using an approximation to the mean and variance of the interference. Simulation results indicate that the proposed algorithm can significantly enhance the system performance to the conventional case, and the improved algorithm can strike a balance between performance and complexity.
文摘近年来,高速移动通信受到业界的广泛关注,其中接收机侧的信道估计直接决定了系统的通信质量。正交频分复用(orthogonal frequency division multiplexing,OFDM)以其高带宽效率和抗多径衰落的特性,在目前的无线通信中被广泛采用。综述了高速移动场景下OFDM系统信道估计方法;描述了OFDM的系统模型;分析了高速移动场景下信道的时间/频率选择性衰落特性(双选特性)和稀疏特性。基于深度学习和压缩感知的信道估计方法,其高精度和低复杂度被用于高速移动场景,该文分别对基于深度学习和压缩感知的信道估计算法进行了归纳、对比、分析,探讨了高速移动场景下信道估计的发展趋势。