Conventional OFDM transmission system uses a fixed-length Cyclic Prefix to counteract Inter-Symbol Inter- ferences (ISI) caused by channel delay spreading under wireless mobile environment. This may cause considerabl...Conventional OFDM transmission system uses a fixed-length Cyclic Prefix to counteract Inter-Symbol Inter- ferences (ISI) caused by channel delay spreading under wireless mobile environment. This may cause considerable per- formance deterioration when the CP length is less than the channel RMS delay spread, or may decrease the system power and spectrum efficiency when it is much larger. A novel Orthogonal Frequency Division Multiplexing (OFDM) transmission scheme is proposed in this paper to adapt the CP length to the variation of channel delay spread. AOFDM-VCPL utilizes the preamble or pilot sub-carriers of each OFDM packet to estimate the channel RMS delay spread; and then uses a criterion to calculate the CP length , which finally affects the OFDM transmitter. As illustrated in the simulation section, by deploying this scheme in a typical wireless environment, the system can transmit at data rate 11.5 Mb/s higher than conventional non-adaptive system while gaining a 0.65 dB power saving at the same BER performance.展开更多
In this paper,a massive multiple input multiple output(MIMO)channel measurement campaign with two setups is conducted in an indoor lobby environment.In the first setup,two types of 256-element virtual uniform rectangu...In this paper,a massive multiple input multiple output(MIMO)channel measurement campaign with two setups is conducted in an indoor lobby environment.In the first setup,two types of 256-element virtual uniform rectangular arrays(URAs),i.e.,the 4×64 virtual URA and the 64×4 virtual URA are used.The carrier frequency is 11 GHz;in the second setup,measurements are performed at 4,6,11,13,15,18 GHz at two different user locations.The channel characterization is presented by investigating the typical channel parameters,including average power delay profile(APDP),K factor,root mean square(RMS)delay spread,and coherence bandwidth.Moreover,the channel characteristics in angular domain are investigated by applying the space-alternating generalized expectation-maximization(SAGE)algorithm.The extracted multipath components(MPCs)are preliminarily clustered by visual inspection,and related to the interacting objects(IOs)in physical environment.Multipath structures at multiple frequency bands are examined.Direction spread of departure is estimated to evaluate the directional dispersion at the base station(BS)side.The results in this paper can help to reveal the propagation mechanisms in massive MIMO channels,and provide a foundation for the design and application of the practical massive MIMO system.展开更多
The several gigabit rate and license-free spectrum resources of 7 GHz bandwidth can be provided by the 60 GHz short-range communication technology, therefore it becomes one of the most promising alternative technologi...The several gigabit rate and license-free spectrum resources of 7 GHz bandwidth can be provided by the 60 GHz short-range communication technology, therefore it becomes one of the most promising alternative technologies in the wireless communication. In this paper, the millimeter wave propagation characteristics in the complex office environment are studied by the SBR/Image method. Firstly, under the complex office environment, the propagation characteristics including received power, the arrival angle and the probability distribution of the arrival angle are studied without regard roughness and oxygen absorption loss. Then, the RMS delay spreads in 60 GHz, 2.4 GHz and 5 GHz wireless LAN signals are simulated and compared.展开更多
为探索高频段室内离体信道的无线传播特性,对9.5~10.5 GHz频段多个典型室内场景进行离体信道测量。在大尺度衰落方面,通过研究路径损耗发现人体遮挡因子与旋转角度呈正弦函数关系,并与收发端距离呈现负指数关系,因此建立距离与角度联合...为探索高频段室内离体信道的无线传播特性,对9.5~10.5 GHz频段多个典型室内场景进行离体信道测量。在大尺度衰落方面,通过研究路径损耗发现人体遮挡因子与旋转角度呈正弦函数关系,并与收发端距离呈现负指数关系,因此建立距离与角度联合相关的新型路径损耗模型,并根据阴影衰落统计特性证明新模型的精确性与适用性。在小尺度衰落方面,通过分析路径损耗与均方根(RMS,root mean square)时延扩展的线性相关性,获得距离与角度相关的新型RMS时延扩展模型。证明了收发端距离与人体旋转产生的遮挡因子越大,路径损耗和多径衰落也越严重。新型离体信道模型可用于设计物联网环境体域网(BAN,body area network)的离体链路,为未来的室内无线通信系统提供理论与实践基础。展开更多
为了给下一代无线通信系统(B3G:Beyond 3G)参数设计提供参考以及为算法仿真提供信道建模,针对国内城市室外环境不同的传播场景,在5.8 GHz频段和20 MHz信道带宽的测量条件下,进行了室外信道测量和研究。根据测量数据统计分析,5.8 GHz频...为了给下一代无线通信系统(B3G:Beyond 3G)参数设计提供参考以及为算法仿真提供信道建模,针对国内城市室外环境不同的传播场景,在5.8 GHz频段和20 MHz信道带宽的测量条件下,进行了室外信道测量和研究。根据测量数据统计分析,5.8 GHz频段路径损耗指数在视距通信(LOS:Line of Sight)时为2.53,在非视距通信(NLOS:No Line of Sight)时为3.3～3.8;同时,对COST231-WI路径损耗模型进行了修正,考虑到阴影衰落的影响,修正后的模型能较准确地预测接收功率,为系统覆盖范围预测提供参考。均方根时延扩展(Root Mean Square Delay Spread)的累积概率为0.9时,在0.5～0.8μs之间变化。均方根角度扩展(RMS Azimuth Spread)主要由发射天线位置和传播环境决定。展开更多
电波传播特性预测是无线电系统设计的基础,其中路径损耗特性关系到系统覆盖范围,决定系统布局,时延特性决定数字通信系统的最大数据传输速率.提出一种预测矩形隧道中电波传播特性的方法,该方法可以通过几何光学原理精确地计算出由发射...电波传播特性预测是无线电系统设计的基础,其中路径损耗特性关系到系统覆盖范围,决定系统布局,时延特性决定数字通信系统的最大数据传输速率.提出一种预测矩形隧道中电波传播特性的方法,该方法可以通过几何光学原理精确地计算出由发射天线到达接收天线的电波主要路径,避免了复杂度很高的射线跟踪过程,使传统预测方法的计算复杂度大大降低.仿真结果表明:该模型对电波传播的路径损耗预测精度不低于传统的射线跟踪方法;隧道环境中收发天线相距越近,其接收的多径信号的平均时延扩散与均方根(root mean square,RMS)时延扩散越大;隧道截面积越大,其接收的多径信号的平均时延扩散与RMS时延扩散越大.展开更多
A propagation measurement campaign was performed at the 10 th floor corridor of Xingjian Building,Shanghai University,China.The channel was sounded by pseudo noise( PN) sequence at carrier frequencies of 400-and 2600-...A propagation measurement campaign was performed at the 10 th floor corridor of Xingjian Building,Shanghai University,China.The channel was sounded by pseudo noise( PN) sequence at carrier frequencies of 400-and 2600-MHz respectively.In order to obtain large scale and small scale propagation characteristics in the corridor,the receiver was moved along the corridor every 1.02 meter to record the impulse response.More than 280,000 impulse responses were recorded in the campaign.This work first describes the principle of the measurement,and then how the recorded raw data are processed.The results show that path loss exponent is related to frequency.The relationship between the root-mean squared( RMS) delay spread and the T-R separation distance is analyzed.The RMS delay spread and the mean excess delay spread against path loss are also given,which explain why the 2600 MHz RMS delay spread is larger than that of 400 MHz.展开更多
基金Project supported by the National Natural Science Foundation ofChina (No. 60002003) and the Hi-Tech Research and Develop-ment Program (863) of China (No. 2002AA123044)
文摘Conventional OFDM transmission system uses a fixed-length Cyclic Prefix to counteract Inter-Symbol Inter- ferences (ISI) caused by channel delay spreading under wireless mobile environment. This may cause considerable per- formance deterioration when the CP length is less than the channel RMS delay spread, or may decrease the system power and spectrum efficiency when it is much larger. A novel Orthogonal Frequency Division Multiplexing (OFDM) transmission scheme is proposed in this paper to adapt the CP length to the variation of channel delay spread. AOFDM-VCPL utilizes the preamble or pilot sub-carriers of each OFDM packet to estimate the channel RMS delay spread; and then uses a criterion to calculate the CP length , which finally affects the OFDM transmitter. As illustrated in the simulation section, by deploying this scheme in a typical wireless environment, the system can transmit at data rate 11.5 Mb/s higher than conventional non-adaptive system while gaining a 0.65 dB power saving at the same BER performance.
基金supported in part by the National Key Research and Development Program of China under Grant 2016YFE0200900 and 2018YFF0212103in part by NSFC under Grant 61725101, 61771037, 6181101396, and U1834210+4 种基金in part by the Beijing Natural Science Foundation under Grant 4182047 and L172020in part by the Fundamental research funds for the central universities under Grant 2017RC031 and Grant 2018JBM301in part by the Major projects of Beijing Municipal Science and Technology Commission under Grant Z181100003218010in part by the State Key Lab of Rail Traffic Control and Safety under Grant 2017JBM332, RCS2018ZZ007, and Grant RCS2018ZT014in part by the Teaching Reform Project under Grant 134496522
文摘In this paper,a massive multiple input multiple output(MIMO)channel measurement campaign with two setups is conducted in an indoor lobby environment.In the first setup,two types of 256-element virtual uniform rectangular arrays(URAs),i.e.,the 4×64 virtual URA and the 64×4 virtual URA are used.The carrier frequency is 11 GHz;in the second setup,measurements are performed at 4,6,11,13,15,18 GHz at two different user locations.The channel characterization is presented by investigating the typical channel parameters,including average power delay profile(APDP),K factor,root mean square(RMS)delay spread,and coherence bandwidth.Moreover,the channel characteristics in angular domain are investigated by applying the space-alternating generalized expectation-maximization(SAGE)algorithm.The extracted multipath components(MPCs)are preliminarily clustered by visual inspection,and related to the interacting objects(IOs)in physical environment.Multipath structures at multiple frequency bands are examined.Direction spread of departure is estimated to evaluate the directional dispersion at the base station(BS)side.The results in this paper can help to reveal the propagation mechanisms in massive MIMO channels,and provide a foundation for the design and application of the practical massive MIMO system.
文摘The several gigabit rate and license-free spectrum resources of 7 GHz bandwidth can be provided by the 60 GHz short-range communication technology, therefore it becomes one of the most promising alternative technologies in the wireless communication. In this paper, the millimeter wave propagation characteristics in the complex office environment are studied by the SBR/Image method. Firstly, under the complex office environment, the propagation characteristics including received power, the arrival angle and the probability distribution of the arrival angle are studied without regard roughness and oxygen absorption loss. Then, the RMS delay spreads in 60 GHz, 2.4 GHz and 5 GHz wireless LAN signals are simulated and compared.
文摘为探索高频段室内离体信道的无线传播特性,对9.5~10.5 GHz频段多个典型室内场景进行离体信道测量。在大尺度衰落方面,通过研究路径损耗发现人体遮挡因子与旋转角度呈正弦函数关系,并与收发端距离呈现负指数关系,因此建立距离与角度联合相关的新型路径损耗模型,并根据阴影衰落统计特性证明新模型的精确性与适用性。在小尺度衰落方面,通过分析路径损耗与均方根(RMS,root mean square)时延扩展的线性相关性,获得距离与角度相关的新型RMS时延扩展模型。证明了收发端距离与人体旋转产生的遮挡因子越大,路径损耗和多径衰落也越严重。新型离体信道模型可用于设计物联网环境体域网(BAN,body area network)的离体链路,为未来的室内无线通信系统提供理论与实践基础。
文摘为了给下一代无线通信系统(B3G:Beyond 3G)参数设计提供参考以及为算法仿真提供信道建模,针对国内城市室外环境不同的传播场景,在5.8 GHz频段和20 MHz信道带宽的测量条件下,进行了室外信道测量和研究。根据测量数据统计分析,5.8 GHz频段路径损耗指数在视距通信(LOS:Line of Sight)时为2.53,在非视距通信(NLOS:No Line of Sight)时为3.3～3.8;同时,对COST231-WI路径损耗模型进行了修正,考虑到阴影衰落的影响,修正后的模型能较准确地预测接收功率,为系统覆盖范围预测提供参考。均方根时延扩展(Root Mean Square Delay Spread)的累积概率为0.9时,在0.5～0.8μs之间变化。均方根角度扩展(RMS Azimuth Spread)主要由发射天线位置和传播环境决定。
文摘电波传播特性预测是无线电系统设计的基础,其中路径损耗特性关系到系统覆盖范围,决定系统布局,时延特性决定数字通信系统的最大数据传输速率.提出一种预测矩形隧道中电波传播特性的方法,该方法可以通过几何光学原理精确地计算出由发射天线到达接收天线的电波主要路径,避免了复杂度很高的射线跟踪过程,使传统预测方法的计算复杂度大大降低.仿真结果表明:该模型对电波传播的路径损耗预测精度不低于传统的射线跟踪方法;隧道环境中收发天线相距越近,其接收的多径信号的平均时延扩散与均方根(root mean square,RMS)时延扩散越大;隧道截面积越大,其接收的多径信号的平均时延扩散与RMS时延扩散越大.
基金Supported by the National Natural Science Foundation of China(No.61132003,61171086,61501186)Shanghai Natural Science Foundation under Grant(No.14ZR1415100)
文摘A propagation measurement campaign was performed at the 10 th floor corridor of Xingjian Building,Shanghai University,China.The channel was sounded by pseudo noise( PN) sequence at carrier frequencies of 400-and 2600-MHz respectively.In order to obtain large scale and small scale propagation characteristics in the corridor,the receiver was moved along the corridor every 1.02 meter to record the impulse response.More than 280,000 impulse responses were recorded in the campaign.This work first describes the principle of the measurement,and then how the recorded raw data are processed.The results show that path loss exponent is related to frequency.The relationship between the root-mean squared( RMS) delay spread and the T-R separation distance is analyzed.The RMS delay spread and the mean excess delay spread against path loss are also given,which explain why the 2600 MHz RMS delay spread is larger than that of 400 MHz.
