对于采用大规模MIMO技术的时分双工系统,基站天线的互易误差会破坏上下行基带信道互易特性,大幅降低系统下行传输性能。考虑到大规模MIMO技术所带来的基站天线间的耦合效应,该文设计了基于总体最小二乘估计的基站天线互易校准算法,以实...对于采用大规模MIMO技术的时分双工系统,基站天线的互易误差会破坏上下行基带信道互易特性,大幅降低系统下行传输性能。考虑到大规模MIMO技术所带来的基站天线间的耦合效应,该文设计了基于总体最小二乘估计的基站天线互易校准算法,以实现对基站的天线互易误差的补偿。该算法以增加计算复杂度为代价,以及通过增加信道测量样本,克服了上下行信道估计误差对现有天线互易误差校准算法的影响。同时,该文通过瑞利商迭代求解降低了该算法的复杂度。若忽略用户天线互易误差,计算机仿真结果表明,该算法相对于现有的基站天线互易误差校正算法,具有1.8 d B左右的性能增益。若考虑用户天线互易误差,该算法相对于已有的算法,具有随信道估计误差方差减小而增大的增益。展开更多
Traditional antenna calibration methods for time division duplex （TDD） systems asSume that the flee-space channel remains the same during calibration, which is unreasonable under the high-speed rail and other time-v...Traditional antenna calibration methods for time division duplex （TDD） systems asSume that the flee-space channel remains the same during calibration, which is unreasonable under the high-speed rail and other time-varying channel scenarios, and will cause calibration error due to time variability. This paper proposes an antenna calibration method for time-varying channels. In the proposed method, the transceiver first sequentially sends a pilot signal to ob- tain equivalent do^vnlink and uplink channel responses. Then, by predicting the downlink （uplink） channel response fed back from the receiver using the channel prediction algorithm, the transmitter obtains the channel response correspond- ing to the channel response on uplink （downlink）. Finally, the transmitter calculates the transmission calibration factor through the prediction value. Compared with the traditional antenna calibration method, this method can improve the accuracy of the calibration factor. Simulation results show that the performance degradation of antenna calibration can be caused by time-varying channels and the proposed method can well compensate for the performance loss and sig- nificantly improve the antenna calibration performance for time-varying channels.展开更多
A moment actuator with direct detection of forces is described.Moment frequency re- sponse and moment excitation purity asperformance criteria are proposed. Methods for the perfor- mancecalibration of the actuator are...A moment actuator with direct detection of forces is described.Moment frequency re- sponse and moment excitation purity asperformance criteria are proposed. Methods for the perfor- mancecalibration of the actuator are presented. Assessment is carried outby means of the reciprocity principle.展开更多
Thanks to channel reciprocity,the time-division duplexing operation is typically used for distributed large-scale multiple-input multiple-output systems.With the knowledge of uplink channel state,APs(Access Points)per...Thanks to channel reciprocity,the time-division duplexing operation is typically used for distributed large-scale multiple-input multiple-output systems.With the knowledge of uplink channel state,APs(Access Points)perform the downlink precoding to cooperatively communicate with multiple UEs(User Equipments).Unfortunately,the channel reciprocity is often jeopardized by the non-symmetric transceiver RF(Radio Frequency)circuits at both sides of the link.By excluding UEs from the calibration procedure,the TLS(Total Least Squares)method is extended to the case of partial calibration,where only the APs are involved to exchange calibration signals to compensate for RF mismatches.Nevertheless,channel fluctuations between APs significantly degrade system performance.Therefore,we propose a scheme to obtain the diversity gain,by performing a calibration with the combination of the calibration signals of different channel coherent times.Simulation results confirm the effective performance and robustness of our scheme.展开更多
文摘对于采用大规模MIMO技术的时分双工系统,基站天线的互易误差会破坏上下行基带信道互易特性,大幅降低系统下行传输性能。考虑到大规模MIMO技术所带来的基站天线间的耦合效应,该文设计了基于总体最小二乘估计的基站天线互易校准算法,以实现对基站的天线互易误差的补偿。该算法以增加计算复杂度为代价,以及通过增加信道测量样本,克服了上下行信道估计误差对现有天线互易误差校准算法的影响。同时,该文通过瑞利商迭代求解降低了该算法的复杂度。若忽略用户天线互易误差,计算机仿真结果表明,该算法相对于现有的基站天线互易误差校正算法,具有1.8 d B左右的性能增益。若考虑用户天线互易误差,该算法相对于已有的算法,具有随信道估计误差方差减小而增大的增益。
基金supported by the National Natural Science Foundation of China(Nos.61032002,61101090 and 60902026)Chinese Important National Science & Technology Specific Projects(No.2011ZX03001-007-01)
文摘Traditional antenna calibration methods for time division duplex （TDD） systems asSume that the flee-space channel remains the same during calibration, which is unreasonable under the high-speed rail and other time-varying channel scenarios, and will cause calibration error due to time variability. This paper proposes an antenna calibration method for time-varying channels. In the proposed method, the transceiver first sequentially sends a pilot signal to ob- tain equivalent do^vnlink and uplink channel responses. Then, by predicting the downlink （uplink） channel response fed back from the receiver using the channel prediction algorithm, the transmitter obtains the channel response correspond- ing to the channel response on uplink （downlink）. Finally, the transmitter calculates the transmission calibration factor through the prediction value. Compared with the traditional antenna calibration method, this method can improve the accuracy of the calibration factor. Simulation results show that the performance degradation of antenna calibration can be caused by time-varying channels and the proposed method can well compensate for the performance loss and sig- nificantly improve the antenna calibration performance for time-varying channels.
基金the Natural Science Foundation of Guangdong Pronvince of China under Grant 960736
文摘A moment actuator with direct detection of forces is described.Moment frequency re- sponse and moment excitation purity asperformance criteria are proposed. Methods for the perfor- mancecalibration of the actuator are presented. Assessment is carried outby means of the reciprocity principle.
基金supported in part by the National Basic Research Program of China("973"Program)(No.2013CB336600)the Natural Science Foundation of China(NSFC)(Nos.61271205,61501113,61521061,61372100)+3 种基金National High Technol-ogy Research and Development Program of China("863"Program)(No.2014AA01A704)the Natural Science Foundation of Jiangsu Province(No.BK20150630)the Hong Kong,Macao and Taiwan Science&Technology Cooperation Program of China(No.2014DFT10290)and the Fundamental Research Funds for the Central Universities and Colleges and Universities in Jiangsu Province Plans to Graduate Research and Innovation(No.KYLX150075).
文摘Thanks to channel reciprocity,the time-division duplexing operation is typically used for distributed large-scale multiple-input multiple-output systems.With the knowledge of uplink channel state,APs(Access Points)perform the downlink precoding to cooperatively communicate with multiple UEs(User Equipments).Unfortunately,the channel reciprocity is often jeopardized by the non-symmetric transceiver RF(Radio Frequency)circuits at both sides of the link.By excluding UEs from the calibration procedure,the TLS(Total Least Squares)method is extended to the case of partial calibration,where only the APs are involved to exchange calibration signals to compensate for RF mismatches.Nevertheless,channel fluctuations between APs significantly degrade system performance.Therefore,we propose a scheme to obtain the diversity gain,by performing a calibration with the combination of the calibration signals of different channel coherent times.Simulation results confirm the effective performance and robustness of our scheme.
