This paper develops a Cyclic Prefix(CP)based joint Maximum-Likelihood(ML)estima-tion algorithm of Carrier Frequency Offset(CFO)and Power Delay Profile(PDP)for Multi-InputMulti-Output Orthogonal Frequency Division Mult...This paper develops a Cyclic Prefix(CP)based joint Maximum-Likelihood(ML)estima-tion algorithm of Carrier Frequency Offset(CFO)and Power Delay Profile(PDP)for Multi-InputMulti-Output Orthogonal Frequency Division Multiplexing(MIMO-OFDM)systems.However,theexact solution of the joint ML estimation is very complex since it needs a search over amulti-dimensional domain.Thus a simplified method is proposed to estimate the CFO and the PDPiteratively via the alternating-projection method which could induce the multidimensional searchproblem to a sequence of simple one-dimensional searches.Simulations show that the proposed algo-rithm is more accurate and robust than the existing algorithms.展开更多
为节省系统带宽,提出了宽带M IMO-OFDM(Mu ltip le-InputMu ltip le-Output and O rthogonal Frequency D i-vision Mu ltip lexing)系统中的一种信道估计方法。该方法只需对重要抽头进行估计,且两步算法在导频数小于信道响应时间和未...为节省系统带宽,提出了宽带M IMO-OFDM(Mu ltip le-InputMu ltip le-Output and O rthogonal Frequency D i-vision Mu ltip lexing)系统中的一种信道估计方法。该方法只需对重要抽头进行估计,且两步算法在导频数小于信道响应时间和未知功率延迟分布的情况下,可获得与经典的LMMSE(L inearM in imum M ean Square Error)算法相近的性能,计算机仿真结果证实了其有效性。展开更多
Output-pulse shaping capability of a linear transformer driver （LTD） module under different conditions is studied, by conducting the whole circuit model simulation by using the PSPICE code. Results indicate that a h...Output-pulse shaping capability of a linear transformer driver （LTD） module under different conditions is studied, by conducting the whole circuit model simulation by using the PSPICE code. Results indicate that a higher impedance profile of the internal transmission line would lead to a wider adjustment range for the output current rise time and a narrower adjustment range for the current peak. The number of cavities in series has a positive effect on the output- pulse shaping capability of LTD. Such an improvement in the output-pulse shaping capability can primarily be ascribed to the increment in the axial electric length of LTD. For a triggering time interval longer than the time taken by a pulse to propagate through the length of one cavity, the output parameters of LTD could be improved significantly. The present insulating capability of gas switches and other elements in the LTD cavities may only tolerate a slightly longer deviation in the triggering time interval. It is feasible for the LTD module to reduce the output current rise time, though it is not useful to improve the peak power effectively.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
This paper studies a new positioning beacon for railway transport using Ultra Wideband (UWB) radio and Time Reversal (TR) techniques. UWB radio has the potential to offer a good level of performance in terms of locali...This paper studies a new positioning beacon for railway transport using Ultra Wideband (UWB) radio and Time Reversal (TR) techniques. UWB radio has the potential to offer a good level of performance in terms of localization accuracy. Time Reversal channel pre-filtering facilitates signal detection and also helps increasing the received energy in the targeted area. In this paper, we evaluate the characteristics of TR technique in terms of temporal focusing. The theoretical and simulation results for Power Delay Profile, equivalent channel model and focusing gain of TR-UWB are given. We analyze the contribution of Time Reversal associated with UWB technology to enhance the localization resolution. The IEEE 802.15.3achannel models are used to evaluate the performance of this system. In terms of localization error, the theoretical and simulation results show that TR-UWB technique delivers improved performance over the UWB localization approach.展开更多
With the increased demand for unmanned driving technology and big-data transmission between vehicles,millimeter-wave(mmWave)technology,due to its characteristics of large bandwidth and low latency,is considered to be ...With the increased demand for unmanned driving technology and big-data transmission between vehicles,millimeter-wave(mmWave)technology,due to its characteristics of large bandwidth and low latency,is considered to be the key technology in future vehicular communication systems.Different from traditional cellular communication,the vehicular communication environment has the characteristics of long distance and high moving speed.However,the existing communication channel tests mostly select low-speed and small-range communication scenarios for testing.The test results are insufficient to provide good data support for the existing vehicular communication research;therefore,in this paper,we carry out a large number of channel measurements in mmWave vehicle-toinfrastructure(V2I)long-distance communication scenarios in the 41 GHz band.We study the received signal strength(RSS)in detail and find that the vibration features of RSS can be best modeled by the modified two-path model considering road roughness.Based on the obtained RSS,a novel close-in(CI)model considering the effect of the transmitter(TX)and receiver(RX)antenna heights(CI-TRH model)is developed.As for the channel characteristics,the distribution of the root-mean-square(RMS)delay spread is analyzed.We also extend the twosection exponential power delay profile(PDP)model to a more general form so that the distance-dependent features of the mmWave channel can be better modeled.Furthermore,the variation in both RMS delay spread and PDP shape parameters with TX-RX distance is analyzed.Analysis results show that TX and RX antenna heights have an effect on large-scale fading.Our modified two-path model,CI-TRH model,and two-section exponential PDP model are proved to be effective.展开更多
A more accurate correlated multiple input and multiple output （MIMO） channel model for IEEE 802.16n is presented. On one hand, this MIMO channel model can obtain more precise antenna correlation, which is a key char...A more accurate correlated multiple input and multiple output （MIMO） channel model for IEEE 802.16n is presented. On one hand, this MIMO channel model can obtain more precise antenna correlation, which is a key character for MIMO channel and important for the research of IEEE 802.16n and MIMO technologies. On the other hand, it maintains a low complexity of simulation.展开更多
基金the National Natural Science Foundation of China(No.60496311).
文摘This paper develops a Cyclic Prefix(CP)based joint Maximum-Likelihood(ML)estima-tion algorithm of Carrier Frequency Offset(CFO)and Power Delay Profile(PDP)for Multi-InputMulti-Output Orthogonal Frequency Division Multiplexing(MIMO-OFDM)systems.However,theexact solution of the joint ML estimation is very complex since it needs a search over amulti-dimensional domain.Thus a simplified method is proposed to estimate the CFO and the PDPiteratively via the alternating-projection method which could induce the multidimensional searchproblem to a sequence of simple one-dimensional searches.Simulations show that the proposed algo-rithm is more accurate and robust than the existing algorithms.
文摘为节省系统带宽,提出了宽带M IMO-OFDM(Mu ltip le-InputMu ltip le-Output and O rthogonal Frequency D i-vision Mu ltip lexing)系统中的一种信道估计方法。该方法只需对重要抽头进行估计,且两步算法在导频数小于信道响应时间和未知功率延迟分布的情况下,可获得与经典的LMMSE(L inearM in imum M ean Square Error)算法相近的性能,计算机仿真结果证实了其有效性。
基金supported by National Natural Science Foundation of China (Nos. 50637010, 51077111)the State Key Laboratory of Electrical Insulation and Power Equipment of Xi'an Jiaotong University of China (EIPE 09207)
文摘Output-pulse shaping capability of a linear transformer driver （LTD） module under different conditions is studied, by conducting the whole circuit model simulation by using the PSPICE code. Results indicate that a higher impedance profile of the internal transmission line would lead to a wider adjustment range for the output current rise time and a narrower adjustment range for the current peak. The number of cavities in series has a positive effect on the output- pulse shaping capability of LTD. Such an improvement in the output-pulse shaping capability can primarily be ascribed to the increment in the axial electric length of LTD. For a triggering time interval longer than the time taken by a pulse to propagate through the length of one cavity, the output parameters of LTD could be improved significantly. The present insulating capability of gas switches and other elements in the LTD cavities may only tolerate a slightly longer deviation in the triggering time interval. It is feasible for the LTD module to reduce the output current rise time, though it is not useful to improve the peak power effectively.
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This paper studies a new positioning beacon for railway transport using Ultra Wideband (UWB) radio and Time Reversal (TR) techniques. UWB radio has the potential to offer a good level of performance in terms of localization accuracy. Time Reversal channel pre-filtering facilitates signal detection and also helps increasing the received energy in the targeted area. In this paper, we evaluate the characteristics of TR technique in terms of temporal focusing. The theoretical and simulation results for Power Delay Profile, equivalent channel model and focusing gain of TR-UWB are given. We analyze the contribution of Time Reversal associated with UWB technology to enhance the localization resolution. The IEEE 802.15.3achannel models are used to evaluate the performance of this system. In terms of localization error, the theoretical and simulation results show that TR-UWB technique delivers improved performance over the UWB localization approach.
基金Project supported by the National Key Research and Development Program of China(No.2020YFB1805001)the National Natural Science Foundation of China(Nos.91938202 and 61801102)+1 种基金the Defense Industrial Technology Development Program,China(No.JCKY2016204A603)the 5G Millimeter Wave High-Speed Channel Simulator,China(No.2021YFG0342)。
文摘With the increased demand for unmanned driving technology and big-data transmission between vehicles,millimeter-wave(mmWave)technology,due to its characteristics of large bandwidth and low latency,is considered to be the key technology in future vehicular communication systems.Different from traditional cellular communication,the vehicular communication environment has the characteristics of long distance and high moving speed.However,the existing communication channel tests mostly select low-speed and small-range communication scenarios for testing.The test results are insufficient to provide good data support for the existing vehicular communication research;therefore,in this paper,we carry out a large number of channel measurements in mmWave vehicle-toinfrastructure(V2I)long-distance communication scenarios in the 41 GHz band.We study the received signal strength(RSS)in detail and find that the vibration features of RSS can be best modeled by the modified two-path model considering road roughness.Based on the obtained RSS,a novel close-in(CI)model considering the effect of the transmitter(TX)and receiver(RX)antenna heights(CI-TRH model)is developed.As for the channel characteristics,the distribution of the root-mean-square(RMS)delay spread is analyzed.We also extend the twosection exponential power delay profile(PDP)model to a more general form so that the distance-dependent features of the mmWave channel can be better modeled.Furthermore,the variation in both RMS delay spread and PDP shape parameters with TX-RX distance is analyzed.Analysis results show that TX and RX antenna heights have an effect on large-scale fading.Our modified two-path model,CI-TRH model,and two-section exponential PDP model are proved to be effective.
文摘A more accurate correlated multiple input and multiple output （MIMO） channel model for IEEE 802.16n is presented. On one hand, this MIMO channel model can obtain more precise antenna correlation, which is a key character for MIMO channel and important for the research of IEEE 802.16n and MIMO technologies. On the other hand, it maintains a low complexity of simulation.
