Terahertz(THz)communication is considered to be a promising technology for future 6G network.To overcome the severe attenuation and relieve the high power consumption,massive multipleinput multiple-output(MIMO)with hy...Terahertz(THz)communication is considered to be a promising technology for future 6G network.To overcome the severe attenuation and relieve the high power consumption,massive multipleinput multiple-output(MIMO)with hybrid precoding has been widely considered for THz communication.However,accurate wideband channel estimation,which is essential for hybrid precoding,is challenging in THz massive MIMO systems.The existing wideband channel estimation schemes based on the ideal assumption of common sparse channel support will suffer from a severe performance loss due to the beam split effect.In this paper,we propose a beam split pattern detection based channel estimation scheme to realize reliable wideband channel estimation in THz massive MIMO systems.Specifically,a comprehensive analysis on the angle-domain sparse structure of the wideband channel is provided by considering the beam split effect.Based on the analysis,we define a series of index sets called as beam split patterns,which are proved to have a one-to-one match to different physical channel directions.Inspired by this one-to-one match,we propose to estimate the physical channel direction by exploiting beam split patterns at first.Then,the sparse channel supports at different subcarriers can be obtained by utilizing a support detection window.This support detection window is generated by expanding the beam split pattern which is determined by the obtained physical channel direction.The above estimation procedure will be repeated path by path until all path components are estimated.Finally,the wideband channel can be recovered by calculating the elements on the total sparse channel support at all subcarriers.The proposed scheme exploits the wideband channel property implied by the beam split effect,i.e.,beam split pattern,which can significantly improve the channel estimation accuracy.Simulation results show that the proposed scheme is able to achieve higher accuracy than existing schemes.展开更多
In this paper, we consider a novel two-dimensional(2D) geometry-based stochastic model(GBSM) for multiple-input multiple-output(MIMO) vehicle-to-vehicle(V2V) wideband fading channels. The proposed model employs the co...In this paper, we consider a novel two-dimensional(2D) geometry-based stochastic model(GBSM) for multiple-input multiple-output(MIMO) vehicle-to-vehicle(V2V) wideband fading channels. The proposed model employs the combination of a two-ring model and a multiple confocal ellipses model, where the signal is sum of the line-of-sight(Lo S) component, single-bounced(SB) rays, and double-bounced(DB) rays. Based on the reference model, we derive some expressions of channel statistical properties, including space-time correlation function(STCF), Doppler spectral power density(DPSD), envelope level crossing rate(LCR) and average fade duration(AFD). In addition, corresponding deterministic and stochastic simulation models are developed based on the reference model. Moreover, we compare the statistical properties of the reference model and the two simulation models in different scenarios and investigate the impact of different vehicular traffic densities(VTDs) on the channel statistical properties of the proposed model. Finally, the great agreement between simulation models and the reference model demonstrates not only the utility of simulation models, but also the correctness of theoretical derivations and simulations.展开更多
A geometry-based stochastic model(GBSM) for unmanned aerial vehicle to vehicle(UAV-V) multiple-input multiple-output(MIMO) wideband channel is proposed to investigate the characteristics of UAV-V channel. Based on the...A geometry-based stochastic model(GBSM) for unmanned aerial vehicle to vehicle(UAV-V) multiple-input multiple-output(MIMO) wideband channel is proposed to investigate the characteristics of UAV-V channel. Based on the proposed model, a three-dimensional(3D) wideband channel matrix regarding channel numbers, time and delay is constructed. And some important channel characteristics parameters, such as power delay profile(PDP), root mean square(RMS) delay spread, RMS Doppler spread, channel gain and Doppler power spectral density(PSD) are investigated with different vehicle velocities. It is much simpler and clearer compared with the complex analytical derivations. The results are compared with validated analysis to confirm the theoretical analysis.展开更多
A novel method,referred to as joint multiple subpulses processing,is developed to calibrate the nonideal transfer function of radio frequency front-end and I/Q imbalance in quadrature modulate/demodulate systems simul...A novel method,referred to as joint multiple subpulses processing,is developed to calibrate the nonideal transfer function of radio frequency front-end and I/Q imbalance in quadrature modulate/demodulate systems simultaneously,which frequently occur in wideband Synthetic Aperture Radar(SAR) systems.Based on the time-frequency relation of the chirp signal and the analyses of the channel errors in wideband SAR,joint multiple subpulses processing method is adopted to separate the image frequency component due to the I/Q channel error.Then,the complete description of the channel error is acquired for building the correction function,which is used to correct the radar raw echo in frequency domain.The validity and capability of this method are demonstrated by the experiments of the channel error correction on the high resolution SAR system with the effective bandwidth of 500 MHz.展开更多
In this paper, on-body radio channel performance of a compact ultra wideband (UWB) antenna is investigated for body-centric wireless communications. Measurement campaigns were first done in the chamber and then repeat...In this paper, on-body radio channel performance of a compact ultra wideband (UWB) antenna is investigated for body-centric wireless communications. Measurement campaigns were first done in the chamber and then repeated in an indoor environment for comparison. The path loss parameter for eight different on-body radio channels has been characterized and analyzed. In addition, the path loss was modeled as a function of distance for 34 different receiver locations for propagation along the front part of the body. Results and analysis show that, compared with anechoic chamber, a reduction of 16.34% path loss exponent is noticed in indoor environment. The antenna shows very good on-body radio channel performance and will be a suitable candidate for future efficient and reliable body-centric wireless communications.展开更多
Wideband multiple-input multiple-output (MIMO) channel measurements were performed at5.25GHz in the hotspot environment in Beijing.The propagation mechanism was line-of-sight and ob-structed-line-of-sight (LOS/OLOS) i...Wideband multiple-input multiple-output (MIMO) channel measurements were performed at5.25GHz in the hotspot environment in Beijing.The propagation mechanism was line-of-sight and ob-structed-line-of-sight (LOS/OLOS) in the outdoor scenario.Using a large amount of estimated angle ofdeparture (AoD) and angle of arrival (AoA) results,the cumulative distribution functions (CDFs) of di-rectional spread (DS) are extracted,which illustrate that the spatial dispersion is quite significant at bothends due to the low antenna height of base station and rich scatterers.The average power azimuth spec-trum (PAS) is found to be well fitted with a Laplacian function.In addition,the non-isotropic property ofspatial correlation is investigated,and the average envelop correlation over arbitrary antenna spacing pro-vides the correlation distance to facilitate the MIMO optimization and deployment in the outdoor hotspotenvironment.展开更多
In order to solve the cross-channel signal problem caused by the uniform channelized wideband digital receiver when processing wideband signal and the problem that the sensitivity of the system greatly decreases when ...In order to solve the cross-channel signal problem caused by the uniform channelized wideband digital receiver when processing wideband signal and the problem that the sensitivity of the system greatly decreases when the bandwidth of wideband digital receiver increases,which both decrease the wideband radar signal detection performance,a new wideband digital receiver based on the modulated wideband converter(MWC)discrete compressed sampling structure and an energy detection method based on the new receiver are proposed.Firstly,the proposed receiver utilizes periodic pseudo-random sequences to mix wideband signals with baseband and other sub-bands.Then the mixed signals are low-pass filtered and downsampled to obtain the baseband compressed sampling data,which can increase the sensitivity of the system.Meanwhile,the cross-channel signal will all appear in any subbands,so the cross-channel signal problem can be solved easily by processing the baseband compressed sampling data.Secondly,we establish the signal detection model and formulate the criterion of the energy detection method.And we directly utilize the baseband compressed sampling data to carry out signal detection without signal reconstruction,which decreases the complexity of the algorithm and reduces the computational burden.Finally,simulation experiments demonstrate the effectiveness of the proposed receiver and show that the proposed signal detection method is effective in low signal-to-noise ratio(SNR)compared with the conventional energy detection and the probability of detection increases significantly when SNR increases.展开更多
Due to the sparse nature of the impulse radio ultra-wideband(IR-UWB)communication channel in the time domain,compressive sensing(CS)theory is very suitable for the sparse channel estimation. Besides the sparse nature,...Due to the sparse nature of the impulse radio ultra-wideband(IR-UWB)communication channel in the time domain,compressive sensing(CS)theory is very suitable for the sparse channel estimation. Besides the sparse nature,the IR-UWB channel has shown more features which can be taken into account in the channel estimation process,such as the clustering structures. In this paper,by taking advantage of the clustering features of the channel,a novel IR-UWB channel estimation scheme based on the Bayesian compressive sensing(BCS)framework is proposed,in which the sparse degree of the channel impulse response is not required. Extensive simulation results show that the proposed channel estimation scheme has obvious advantages over the traditional scheme,and the final demodulation performance,in terms of Bit Error Rate(BER),is therefore greatly improved.展开更多
This work extends the use of wavelet-based denoising as an alternative processing scheme to improve measured mobile-radio channel power delay profiles. It has already been reported that, when applied on real domain da...This work extends the use of wavelet-based denoising as an alternative processing scheme to improve measured mobile-radio channel power delay profiles. It has already been reported that, when applied on real domain data (amplitude only), denoising provides mainly a qualitative improvement. Here, phase content was also considered, leading to significant qualitative and quantitative improvement of the processed profiles. Signal-to-noise ratios and dynamic ranges improvements as high as 50 dB have been observed.展开更多
Multipath arrivals in an Ultra-WideBand (UWB) channel have a long time intervals between clusters and rays where the signal takes on zero or negligible values. It is precisely the signal sparsity of the impulse respon...Multipath arrivals in an Ultra-WideBand (UWB) channel have a long time intervals between clusters and rays where the signal takes on zero or negligible values. It is precisely the signal sparsity of the impulse response of the UWB channel that is exploited in this work aiming at UWB channel estimation based on Compressed Sensing (CS). However, these multipath arrivals mainly depend on the channel environments that generate different sparse levels (low-sparse or high-sparse) of the UWB channels. According to this basis, we have analyzed the two most basic recovery algorithms, one based on linear programming Basis Pursuit (BP), another using greedy method Orthogonal Matching Pursuit (OMP), and chosen the best recovery algorithm which are suitable to the sparse level for each type of channel environment. Besides, the results of this work is an open topic for further research aimed at creating a optimal algorithm specially for application of CS based UWB systems.展开更多
Channel measurement and modeling is an important issue when designing ultra wideband (UWB) communication systems. A Precise model of the channel response is inevitable for designing an ultra wideband telecommunication...Channel measurement and modeling is an important issue when designing ultra wideband (UWB) communication systems. A Precise model of the channel response is inevitable for designing an ultra wideband telecommunication system. In this article signal propagation in indoor environment and LOS condition is evaluated and the appropriate model of this scenario is presented. Parameters such as the power delay profile, mean excess delay, delay spread, “NP10dB” are analyzed and simulated. Based on analysis results, the proposed model is presented. This model is based on Two-cluster approach but its average power delay profile is described with power function and cluster time of arrival is modeled by the modified exponential distribution. Finally UWB channel parameters of proposed model, Saleh and Valenzuela (S-V) and Two-cluster models are compared. Measurement and simulation results show that considerable improvement for mean excess delay, delay spread and “NP10dB” of proposed model comparing with S-V and Two-cluster model, this means the channel is better described, which mean the channel is described more precisely.展开更多
针对5G车对车(vehicle to vehicle,V2V)无线通信系统,基于几何随机建模方法,提出一种改进的三维宽带多输入多输出(multiple-input and multiple-outpit,MIMO)信道模型。引入多共焦半椭球体模型用于研究不同传播延迟下的V2V信道统计特性...针对5G车对车(vehicle to vehicle,V2V)无线通信系统,基于几何随机建模方法,提出一种改进的三维宽带多输入多输出(multiple-input and multiple-outpit,MIMO)信道模型。引入多共焦半椭球体模型用于研究不同传播延迟下的V2V信道统计特性,结合时变的路径长度、信号角度和莱斯因子表征V2V信道的非平稳特性。推导了空-时相关函数、多普勒功率谱密度等关键信道统计特性的数学表达式。分析了城市和高速场景下信道相关特性的差别,并研究了车流密度、运动方向、天线角度、传播延迟等因素对信道统计特性的影响。结果表明,城市场景下的时间相关性和空间相关性明显低于高速场景;不同传播延迟下的V2V信道统计特性有明显差异;信道相关性同天线阵列角度、收发车运动方向和时间变化密切相关。模型仿真结果为车载通信提供了一些有价值的结论,可以作为未来V2V通信系统设计、优化和评估的有效指导。仿真结果与实测数据较好地吻合,证明模型能正确表征V2V无线信道的相关特性。展开更多
基金supported in part by the National Key Research and Development Program of China(Grant No.2020YFB1805005)the National Natural Science Foundation of China(Grant No.62031019)the European Commission through the H2020-MSCA-ITN META WIRELESS Research Project under Grant 956256.
文摘Terahertz(THz)communication is considered to be a promising technology for future 6G network.To overcome the severe attenuation and relieve the high power consumption,massive multipleinput multiple-output(MIMO)with hybrid precoding has been widely considered for THz communication.However,accurate wideband channel estimation,which is essential for hybrid precoding,is challenging in THz massive MIMO systems.The existing wideband channel estimation schemes based on the ideal assumption of common sparse channel support will suffer from a severe performance loss due to the beam split effect.In this paper,we propose a beam split pattern detection based channel estimation scheme to realize reliable wideband channel estimation in THz massive MIMO systems.Specifically,a comprehensive analysis on the angle-domain sparse structure of the wideband channel is provided by considering the beam split effect.Based on the analysis,we define a series of index sets called as beam split patterns,which are proved to have a one-to-one match to different physical channel directions.Inspired by this one-to-one match,we propose to estimate the physical channel direction by exploiting beam split patterns at first.Then,the sparse channel supports at different subcarriers can be obtained by utilizing a support detection window.This support detection window is generated by expanding the beam split pattern which is determined by the obtained physical channel direction.The above estimation procedure will be repeated path by path until all path components are estimated.Finally,the wideband channel can be recovered by calculating the elements on the total sparse channel support at all subcarriers.The proposed scheme exploits the wideband channel property implied by the beam split effect,i.e.,beam split pattern,which can significantly improve the channel estimation accuracy.Simulation results show that the proposed scheme is able to achieve higher accuracy than existing schemes.
基金supported in part by the project from the ZTEthe National Natural Science Foundation of China under Grant 61622101 and Grant 61571020National Science and Technology Major Project under Grant 2018ZX03001031
文摘In this paper, we consider a novel two-dimensional(2D) geometry-based stochastic model(GBSM) for multiple-input multiple-output(MIMO) vehicle-to-vehicle(V2V) wideband fading channels. The proposed model employs the combination of a two-ring model and a multiple confocal ellipses model, where the signal is sum of the line-of-sight(Lo S) component, single-bounced(SB) rays, and double-bounced(DB) rays. Based on the reference model, we derive some expressions of channel statistical properties, including space-time correlation function(STCF), Doppler spectral power density(DPSD), envelope level crossing rate(LCR) and average fade duration(AFD). In addition, corresponding deterministic and stochastic simulation models are developed based on the reference model. Moreover, we compare the statistical properties of the reference model and the two simulation models in different scenarios and investigate the impact of different vehicular traffic densities(VTDs) on the channel statistical properties of the proposed model. Finally, the great agreement between simulation models and the reference model demonstrates not only the utility of simulation models, but also the correctness of theoretical derivations and simulations.
基金supported by the National Natural Science Foundation of China (62001166, 62172139)the Natural Science Foundation of Hebei Province of China(F2022201055)。
文摘A geometry-based stochastic model(GBSM) for unmanned aerial vehicle to vehicle(UAV-V) multiple-input multiple-output(MIMO) wideband channel is proposed to investigate the characteristics of UAV-V channel. Based on the proposed model, a three-dimensional(3D) wideband channel matrix regarding channel numbers, time and delay is constructed. And some important channel characteristics parameters, such as power delay profile(PDP), root mean square(RMS) delay spread, RMS Doppler spread, channel gain and Doppler power spectral density(PSD) are investigated with different vehicle velocities. It is much simpler and clearer compared with the complex analytical derivations. The results are compared with validated analysis to confirm the theoretical analysis.
基金Supported by the National High-Tech Research and Development Plan of China(No.2007AA120302)
文摘A novel method,referred to as joint multiple subpulses processing,is developed to calibrate the nonideal transfer function of radio frequency front-end and I/Q imbalance in quadrature modulate/demodulate systems simultaneously,which frequently occur in wideband Synthetic Aperture Radar(SAR) systems.Based on the time-frequency relation of the chirp signal and the analyses of the channel errors in wideband SAR,joint multiple subpulses processing method is adopted to separate the image frequency component due to the I/Q channel error.Then,the complete description of the channel error is acquired for building the correction function,which is used to correct the radar raw echo in frequency domain.The validity and capability of this method are demonstrated by the experiments of the channel error correction on the high resolution SAR system with the effective bandwidth of 500 MHz.
文摘In this paper, on-body radio channel performance of a compact ultra wideband (UWB) antenna is investigated for body-centric wireless communications. Measurement campaigns were first done in the chamber and then repeated in an indoor environment for comparison. The path loss parameter for eight different on-body radio channels has been characterized and analyzed. In addition, the path loss was modeled as a function of distance for 34 different receiver locations for propagation along the front part of the body. Results and analysis show that, compared with anechoic chamber, a reduction of 16.34% path loss exponent is noticed in indoor environment. The antenna shows very good on-body radio channel performance and will be a suitable candidate for future efficient and reliable body-centric wireless communications.
基金the National High Technology Research and Development Programme of China(No.2006AA01Z258)
文摘Wideband multiple-input multiple-output (MIMO) channel measurements were performed at5.25GHz in the hotspot environment in Beijing.The propagation mechanism was line-of-sight and ob-structed-line-of-sight (LOS/OLOS) in the outdoor scenario.Using a large amount of estimated angle ofdeparture (AoD) and angle of arrival (AoA) results,the cumulative distribution functions (CDFs) of di-rectional spread (DS) are extracted,which illustrate that the spatial dispersion is quite significant at bothends due to the low antenna height of base station and rich scatterers.The average power azimuth spec-trum (PAS) is found to be well fitted with a Laplacian function.In addition,the non-isotropic property ofspatial correlation is investigated,and the average envelop correlation over arbitrary antenna spacing pro-vides the correlation distance to facilitate the MIMO optimization and deployment in the outdoor hotspotenvironment.
基金supported by the National Natural Science Foundation of China(No.61571146)the Fundamental Research Funds for the Central Universities(HEUCF1608)
文摘In order to solve the cross-channel signal problem caused by the uniform channelized wideband digital receiver when processing wideband signal and the problem that the sensitivity of the system greatly decreases when the bandwidth of wideband digital receiver increases,which both decrease the wideband radar signal detection performance,a new wideband digital receiver based on the modulated wideband converter(MWC)discrete compressed sampling structure and an energy detection method based on the new receiver are proposed.Firstly,the proposed receiver utilizes periodic pseudo-random sequences to mix wideband signals with baseband and other sub-bands.Then the mixed signals are low-pass filtered and downsampled to obtain the baseband compressed sampling data,which can increase the sensitivity of the system.Meanwhile,the cross-channel signal will all appear in any subbands,so the cross-channel signal problem can be solved easily by processing the baseband compressed sampling data.Secondly,we establish the signal detection model and formulate the criterion of the energy detection method.And we directly utilize the baseband compressed sampling data to carry out signal detection without signal reconstruction,which decreases the complexity of the algorithm and reduces the computational burden.Finally,simulation experiments demonstrate the effectiveness of the proposed receiver and show that the proposed signal detection method is effective in low signal-to-noise ratio(SNR)compared with the conventional energy detection and the probability of detection increases significantly when SNR increases.
基金sponsored by the National Natural Science Foundation of China(Grant Nos.61001092,61371102)
文摘Due to the sparse nature of the impulse radio ultra-wideband(IR-UWB)communication channel in the time domain,compressive sensing(CS)theory is very suitable for the sparse channel estimation. Besides the sparse nature,the IR-UWB channel has shown more features which can be taken into account in the channel estimation process,such as the clustering structures. In this paper,by taking advantage of the clustering features of the channel,a novel IR-UWB channel estimation scheme based on the Bayesian compressive sensing(BCS)framework is proposed,in which the sparse degree of the channel impulse response is not required. Extensive simulation results show that the proposed channel estimation scheme has obvious advantages over the traditional scheme,and the final demodulation performance,in terms of Bit Error Rate(BER),is therefore greatly improved.
文摘This work extends the use of wavelet-based denoising as an alternative processing scheme to improve measured mobile-radio channel power delay profiles. It has already been reported that, when applied on real domain data (amplitude only), denoising provides mainly a qualitative improvement. Here, phase content was also considered, leading to significant qualitative and quantitative improvement of the processed profiles. Signal-to-noise ratios and dynamic ranges improvements as high as 50 dB have been observed.
文摘Multipath arrivals in an Ultra-WideBand (UWB) channel have a long time intervals between clusters and rays where the signal takes on zero or negligible values. It is precisely the signal sparsity of the impulse response of the UWB channel that is exploited in this work aiming at UWB channel estimation based on Compressed Sensing (CS). However, these multipath arrivals mainly depend on the channel environments that generate different sparse levels (low-sparse or high-sparse) of the UWB channels. According to this basis, we have analyzed the two most basic recovery algorithms, one based on linear programming Basis Pursuit (BP), another using greedy method Orthogonal Matching Pursuit (OMP), and chosen the best recovery algorithm which are suitable to the sparse level for each type of channel environment. Besides, the results of this work is an open topic for further research aimed at creating a optimal algorithm specially for application of CS based UWB systems.
文摘Channel measurement and modeling is an important issue when designing ultra wideband (UWB) communication systems. A Precise model of the channel response is inevitable for designing an ultra wideband telecommunication system. In this article signal propagation in indoor environment and LOS condition is evaluated and the appropriate model of this scenario is presented. Parameters such as the power delay profile, mean excess delay, delay spread, “NP10dB” are analyzed and simulated. Based on analysis results, the proposed model is presented. This model is based on Two-cluster approach but its average power delay profile is described with power function and cluster time of arrival is modeled by the modified exponential distribution. Finally UWB channel parameters of proposed model, Saleh and Valenzuela (S-V) and Two-cluster models are compared. Measurement and simulation results show that considerable improvement for mean excess delay, delay spread and “NP10dB” of proposed model comparing with S-V and Two-cluster model, this means the channel is better described, which mean the channel is described more precisely.
文摘针对5G车对车(vehicle to vehicle,V2V)无线通信系统,基于几何随机建模方法,提出一种改进的三维宽带多输入多输出(multiple-input and multiple-outpit,MIMO)信道模型。引入多共焦半椭球体模型用于研究不同传播延迟下的V2V信道统计特性,结合时变的路径长度、信号角度和莱斯因子表征V2V信道的非平稳特性。推导了空-时相关函数、多普勒功率谱密度等关键信道统计特性的数学表达式。分析了城市和高速场景下信道相关特性的差别,并研究了车流密度、运动方向、天线角度、传播延迟等因素对信道统计特性的影响。结果表明,城市场景下的时间相关性和空间相关性明显低于高速场景;不同传播延迟下的V2V信道统计特性有明显差异;信道相关性同天线阵列角度、收发车运动方向和时间变化密切相关。模型仿真结果为车载通信提供了一些有价值的结论,可以作为未来V2V通信系统设计、优化和评估的有效指导。仿真结果与实测数据较好地吻合,证明模型能正确表征V2V无线信道的相关特性。