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
A novel behavioral model using three-layer time-delay feed-forward neural networks （TDFFNN）is adopted to model radio frequency （RF）power amplifiers exhibiting memory nonlinearities. In order to extract the paramet...A novel behavioral model using three-layer time-delay feed-forward neural networks （TDFFNN）is adopted to model radio frequency （RF）power amplifiers exhibiting memory nonlinearities. In order to extract the parameters, the back- propagation algorithm is applied to train the proposed neural networks. The proposed model is verified by the typical odd- order-only memory polynomial model in simulation, and the performance is compared with different numbers of taped delay lines（TDLs） and perceptrons of the hidden layer. For validating the TDFFNN model by experiments, a digital test bench is set up to collect input and output data of power amplifiers at a 60 × 10^6 sample/s sampling rate. The 3.75 MHz 16-QAM signal generated in the vector signal generator（VSG） is chosen as the input signal, when measuring the dynamic AM/AM and AM/PM characteristics of power amplifiers. By comparisons and analyses, the presented model provides a good performance in convergence, accuracy and efficiency, which is approved by simulation results and experimental results in the time domain and frequency domain.展开更多
In this paper,potential use of perfect but delayed channel estimates for variable-power discrete-rate adaptive modulation is explored.Research is concentrated on block by block adaptation.At first,a new quantity-TAUD(...In this paper,potential use of perfect but delayed channel estimates for variable-power discrete-rate adaptive modulation is explored.Research is concentrated on block by block adaptation.At first,a new quantity-TAUD(Tolerable Average Use Delay)is defined,it quantifies the performance of an adaptation scheme in tolerating the delay of channel estimates.Then,the research on TAUD shows that the delay tolerating performance declines with the increase in average power,the scheme working with more modulation modes can tolerate a longer delay,and such improvement will be more significant with the increase of average power.Finally,it shows that,as the delay tolerating performance determines the maximum block length,it has a great effect on the maximum spectral efficiency.The criterion for determining the block length appropriate for the target BER is described and a simple method of calculating the maximum block length is presented.展开更多
Environmentally clean photovoltaic(PV)generation has found wider application,but the power f luctuation generated from PV can negatively impact the operation of power system.A properly designed energy storage system(E...Environmentally clean photovoltaic(PV)generation has found wider application,but the power f luctuation generated from PV can negatively impact the operation of power system.A properly designed energy storage system(ESS)can stabilize power system by absorbing and injecting instantaneous power.Suitable control strategy of ESS is studied in order to accommodate the power f luctuation.It adopts negative feedback which considers the relationship between real power and voltage in the distribution network because resistor is comparable to reactance of the lines in the distribution network.A universal model of ESS is established,the characteristic parameters such as time-delay of system response,limitation of charging and discharging and restraint of energy storage capacity are taken into account.The validity of the proposed model is verif ied by user-def ined modules in power system analysis software package(PSASP).The operation of PV generation at Wuhan Railway Station in both grid-connected mode and island mode at Wuhan Railway Station is analyzed in detail.The performances of the local distribution network with PV under different weather conditions are summarized,and the key parameter of ESS suitable for PV generation at Wuhan Railway Station is also recommended.展开更多
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The National Natural Science Foundation of China(No.60621002)the National High Technology Research and Development Pro-gram of China(863 Program)(No.2007AA01Z2B4).
文摘A novel behavioral model using three-layer time-delay feed-forward neural networks （TDFFNN）is adopted to model radio frequency （RF）power amplifiers exhibiting memory nonlinearities. In order to extract the parameters, the back- propagation algorithm is applied to train the proposed neural networks. The proposed model is verified by the typical odd- order-only memory polynomial model in simulation, and the performance is compared with different numbers of taped delay lines（TDLs） and perceptrons of the hidden layer. For validating the TDFFNN model by experiments, a digital test bench is set up to collect input and output data of power amplifiers at a 60 × 10^6 sample/s sampling rate. The 3.75 MHz 16-QAM signal generated in the vector signal generator（VSG） is chosen as the input signal, when measuring the dynamic AM/AM and AM/PM characteristics of power amplifiers. By comparisons and analyses, the presented model provides a good performance in convergence, accuracy and efficiency, which is approved by simulation results and experimental results in the time domain and frequency domain.
基金supported by National Natural Science Foundation of China(No.61071087)Chun Lei 2009BWZ037 from SDUST,China
文摘In this paper,potential use of perfect but delayed channel estimates for variable-power discrete-rate adaptive modulation is explored.Research is concentrated on block by block adaptation.At first,a new quantity-TAUD(Tolerable Average Use Delay)is defined,it quantifies the performance of an adaptation scheme in tolerating the delay of channel estimates.Then,the research on TAUD shows that the delay tolerating performance declines with the increase in average power,the scheme working with more modulation modes can tolerate a longer delay,and such improvement will be more significant with the increase of average power.Finally,it shows that,as the delay tolerating performance determines the maximum block length,it has a great effect on the maximum spectral efficiency.The criterion for determining the block length appropriate for the target BER is described and a simple method of calculating the maximum block length is presented.
基金Key Project of National Natural Science Foundation China(50837003)The National Basic Research Program(973 Program)(2009CB219702)
文摘Environmentally clean photovoltaic(PV)generation has found wider application,but the power f luctuation generated from PV can negatively impact the operation of power system.A properly designed energy storage system(ESS)can stabilize power system by absorbing and injecting instantaneous power.Suitable control strategy of ESS is studied in order to accommodate the power f luctuation.It adopts negative feedback which considers the relationship between real power and voltage in the distribution network because resistor is comparable to reactance of the lines in the distribution network.A universal model of ESS is established,the characteristic parameters such as time-delay of system response,limitation of charging and discharging and restraint of energy storage capacity are taken into account.The validity of the proposed model is verif ied by user-def ined modules in power system analysis software package(PSASP).The operation of PV generation at Wuhan Railway Station in both grid-connected mode and island mode at Wuhan Railway Station is analyzed in detail.The performances of the local distribution network with PV under different weather conditions are summarized,and the key parameter of ESS suitable for PV generation at Wuhan Railway Station is also recommended.
