The theoretical lower bounds on mean squared channel estimation errors for typical fading channels are presented by the infinite-length and non-causal Wiener filter and the exact closed-form expressions of the lower b...The theoretical lower bounds on mean squared channel estimation errors for typical fading channels are presented by the infinite-length and non-causal Wiener filter and the exact closed-form expressions of the lower bounds for different channel Doppler spectra are derived. Based on the obtained lower bounds on mean squared channel estimation errors, the limits on bit error rate （BER） for maximal ratio combining （MRC） with Gaussian distributed weighting errors on independent and identically distributed （i. i. d） fading channels are presented. Numerical results show that the BER performances of ideal MRC are the lower bounds on the BER performances of non-ideal MRC and deteriorate as the maximum Doppler frequency increases or the SNR of channel estimate decreases.展开更多
本文设计了一个多输入单输出(Multiple-Input Single-Output,MISO)的三维室内可见光定位通信一体化(Visible Light Position and Communication,VLPC)系统,该系统在接收端基于接收信号强度(Received Signal Strength,RSS)的三维可见光定...本文设计了一个多输入单输出(Multiple-Input Single-Output,MISO)的三维室内可见光定位通信一体化(Visible Light Position and Communication,VLPC)系统,该系统在接收端基于接收信号强度(Received Signal Strength,RSS)的三维可见光定位(Visible Light Position,VLP)算法获得定位数据,同时估计信道状态信息(Channel State Information,CSI)并上传给发射端进行定向通信.该系统的发射端基于空移键控(Space Shift Keying,SSK)的室内可见光通信(Visible Light Communication,VLC)技术实现系统的通信功能.另外,本方案可以完全避免通信与定位子系统之间的干扰.同时,通过推导定位误差的克拉美罗下界(Cramér-Rao Lower Bound,CRLB)和SSK-VLC的通信可达速率来评估本文提出的VLPC系统的性能.仿真结果验证了本文所提方案的有效性.展开更多
This paper deals with the blow-up rate of positive solution for a semilinearparabolic system coupled in the equations and boundary condition. The upper and lower bounds ofblow-up rates are obtained.
This paper deals with the blow-up rate estimates of positive solutions for systems of heat equationswith nonlinear boundary conditions. The upper and lower bounds of blow-up rate are obtained.
The covID-19 outbreak has brought unprecedented social attention to economic uncertainty and negative interest rate policy(NIRP).How does uncertainty affect economic activity,and how effective is a NIRP based on centr...The covID-19 outbreak has brought unprecedented social attention to economic uncertainty and negative interest rate policy(NIRP).How does uncertainty affect economic activity,and how effective is a NIRP based on central bank digital currency(CBDC)?To answer the two questions,we constructed a dynamic stochastic general equilibrium(DSGE)model that accommodates sticky prices and wages.The results indicated:(i)Economic uncertainty has substantially reduced investment,output,wage,and loans,which increases unemployment risk.In the short term,it has triggered impulsive consumption by households,while consumption has fallen into a slump in the long run.(ii)After suffering an uncertainty shock,the economy entered short-term stagflation and long-term deflation.The short-term stagflation was mainly caused by resident wage adjustment,and the long-term deflation was due to the decline in effective demand caused by unemployment risk.(ii)CBDC could eliminate the zero lower bound(ZLB)constraint,thereby improving the effectiveness of NIRP.Compared with traditional currency,CBDCbased NIRP could more effectively smooth macroeconomic fluctuations and alleviate the negative impact of an uncertainty shock,which is more conducive to restoring market confidence and promoting economic recovery.展开更多
As an important parameter in the single airborne passive locating system, the rate of phase difference change contains range information of the radio emitter. Taking single carrier sine pulse signals as an example, th...As an important parameter in the single airborne passive locating system, the rate of phase difference change contains range information of the radio emitter. Taking single carrier sine pulse signals as an example, this article illustrates the principle of passive location through measurement of rates of phase difference change and analyzes the structure of measurement errors. On the basis of the Cramér-Rao lower bound (CRLB), an algorithm associated with time-chips is proposed to determine the rates of pha...展开更多
在新发展格局下,金融市场的高质量发展不能忽视外部因素的影响。美联储的货币政策调整会对中国金融市场产生怎样的影响,现有文献的研究还不够充分全面,尤其缺乏对于零利率下限时期与常态化时期的比较分析。本文认为,美联储实施紧缩性货...在新发展格局下,金融市场的高质量发展不能忽视外部因素的影响。美联储的货币政策调整会对中国金融市场产生怎样的影响,现有文献的研究还不够充分全面,尤其缺乏对于零利率下限时期与常态化时期的比较分析。本文认为,美联储实施紧缩性货币政策将缩小中美两国利差,促使中国的资本外流加剧,并导致实际利率水平和企业融资成本增加,进而带来资产价格下跌,对中国金融市场产生负面影响。2008年全球金融危机以及2020年新冠疫情之后,美联储不断下调联邦基金利率,使其面临零利率下限约束,此时实施紧缩性货币政策对中国金融市场的影响可能会与常态化时期有所区别。基于2002年1月至2021年7月中国宏观经济和金融98个变量的月度数据,采用Wu-Xia联邦基金影子利率(Wu-Xia Shadow Federal Funds Rate)来度量零利率下限时期的美联储货币政策立场,运用因子扩张型向量自回归模型(FAVAR)从资产价格角度分析美联储紧缩性货币政策冲击对中国金融市场的影响,结果显示:总体上看,美联储紧缩性货币政策冲击会通过利率渠道对中国资产价格产生负面影响,且该负面影响具有时滞性;人民币汇率调整具有补偿效应,即可以通过人民币贬值减轻资本外流的压力,进而削弱美联储紧缩性货币政策冲击对中国资产价格的负面影响;在零利率下限时期,美联储紧缩性货币政策冲击对中国资产价格的负面影响比常态化时期更为显著。相比现有文献,本文主要进行了如下改进和拓展:一是采用Wu-Xia联邦基金影子利率度量零利率下限时期美联储的货币政策立场,避免因采用联邦基金利率而低估其负面影响;二是运用FAVAR模型缓解VAR模型及TVP-VAR模型的遗漏变量偏误问题,并为识别结构冲击提供足够丰富的信息;三是对零利率下限时期与常态化时期进行比较分析,有利于更好地把握美联储货币政策冲击对中国金融市场的时变影响。为更好地应对美联储紧缩性货币政策冲击对中国金融市场和宏观经济造成的负面影响,需要深入分析和把握美联储货币政策动向发生改变的原因和本质,在坚持货币政策“以我为主”的同时,密切关注和警惕美联储紧缩性货币政策冲击可能产生的负面影响,并不断深化人民币汇率改革,保证人民币汇率弹性适度和调整空间充足。展开更多
文摘The theoretical lower bounds on mean squared channel estimation errors for typical fading channels are presented by the infinite-length and non-causal Wiener filter and the exact closed-form expressions of the lower bounds for different channel Doppler spectra are derived. Based on the obtained lower bounds on mean squared channel estimation errors, the limits on bit error rate （BER） for maximal ratio combining （MRC） with Gaussian distributed weighting errors on independent and identically distributed （i. i. d） fading channels are presented. Numerical results show that the BER performances of ideal MRC are the lower bounds on the BER performances of non-ideal MRC and deteriorate as the maximum Doppler frequency increases or the SNR of channel estimate decreases.
文摘本文设计了一个多输入单输出(Multiple-Input Single-Output,MISO)的三维室内可见光定位通信一体化(Visible Light Position and Communication,VLPC)系统,该系统在接收端基于接收信号强度(Received Signal Strength,RSS)的三维可见光定位(Visible Light Position,VLP)算法获得定位数据,同时估计信道状态信息(Channel State Information,CSI)并上传给发射端进行定向通信.该系统的发射端基于空移键控(Space Shift Keying,SSK)的室内可见光通信(Visible Light Communication,VLC)技术实现系统的通信功能.另外,本方案可以完全避免通信与定位子系统之间的干扰.同时,通过推导定位误差的克拉美罗下界(Cramér-Rao Lower Bound,CRLB)和SSK-VLC的通信可达速率来评估本文提出的VLPC系统的性能.仿真结果验证了本文所提方案的有效性.
文摘This paper deals with the blow-up rate of positive solution for a semilinearparabolic system coupled in the equations and boundary condition. The upper and lower bounds ofblow-up rates are obtained.
基金This work was supported by the National Natural Science Foundation of China (Grant No. 19831060) and "333" Project of Jiangsu Province.
文摘This paper deals with the blow-up rate estimates of positive solutions for systems of heat equationswith nonlinear boundary conditions. The upper and lower bounds of blow-up rate are obtained.
基金the National Planning Office of Philosophy and Social Science of China(Grant No.21BJY206)。
文摘The covID-19 outbreak has brought unprecedented social attention to economic uncertainty and negative interest rate policy(NIRP).How does uncertainty affect economic activity,and how effective is a NIRP based on central bank digital currency(CBDC)?To answer the two questions,we constructed a dynamic stochastic general equilibrium(DSGE)model that accommodates sticky prices and wages.The results indicated:(i)Economic uncertainty has substantially reduced investment,output,wage,and loans,which increases unemployment risk.In the short term,it has triggered impulsive consumption by households,while consumption has fallen into a slump in the long run.(ii)After suffering an uncertainty shock,the economy entered short-term stagflation and long-term deflation.The short-term stagflation was mainly caused by resident wage adjustment,and the long-term deflation was due to the decline in effective demand caused by unemployment risk.(ii)CBDC could eliminate the zero lower bound(ZLB)constraint,thereby improving the effectiveness of NIRP.Compared with traditional currency,CBDCbased NIRP could more effectively smooth macroeconomic fluctuations and alleviate the negative impact of an uncertainty shock,which is more conducive to restoring market confidence and promoting economic recovery.
基金Aeronautical Science Foundation of China (2007ZC53030)
文摘As an important parameter in the single airborne passive locating system, the rate of phase difference change contains range information of the radio emitter. Taking single carrier sine pulse signals as an example, this article illustrates the principle of passive location through measurement of rates of phase difference change and analyzes the structure of measurement errors. On the basis of the Cramér-Rao lower bound (CRLB), an algorithm associated with time-chips is proposed to determine the rates of pha...
文摘在新发展格局下,金融市场的高质量发展不能忽视外部因素的影响。美联储的货币政策调整会对中国金融市场产生怎样的影响,现有文献的研究还不够充分全面,尤其缺乏对于零利率下限时期与常态化时期的比较分析。本文认为,美联储实施紧缩性货币政策将缩小中美两国利差,促使中国的资本外流加剧,并导致实际利率水平和企业融资成本增加,进而带来资产价格下跌,对中国金融市场产生负面影响。2008年全球金融危机以及2020年新冠疫情之后,美联储不断下调联邦基金利率,使其面临零利率下限约束,此时实施紧缩性货币政策对中国金融市场的影响可能会与常态化时期有所区别。基于2002年1月至2021年7月中国宏观经济和金融98个变量的月度数据,采用Wu-Xia联邦基金影子利率(Wu-Xia Shadow Federal Funds Rate)来度量零利率下限时期的美联储货币政策立场,运用因子扩张型向量自回归模型(FAVAR)从资产价格角度分析美联储紧缩性货币政策冲击对中国金融市场的影响,结果显示:总体上看,美联储紧缩性货币政策冲击会通过利率渠道对中国资产价格产生负面影响,且该负面影响具有时滞性;人民币汇率调整具有补偿效应,即可以通过人民币贬值减轻资本外流的压力,进而削弱美联储紧缩性货币政策冲击对中国资产价格的负面影响;在零利率下限时期,美联储紧缩性货币政策冲击对中国资产价格的负面影响比常态化时期更为显著。相比现有文献,本文主要进行了如下改进和拓展:一是采用Wu-Xia联邦基金影子利率度量零利率下限时期美联储的货币政策立场,避免因采用联邦基金利率而低估其负面影响;二是运用FAVAR模型缓解VAR模型及TVP-VAR模型的遗漏变量偏误问题,并为识别结构冲击提供足够丰富的信息;三是对零利率下限时期与常态化时期进行比较分析,有利于更好地把握美联储货币政策冲击对中国金融市场的时变影响。为更好地应对美联储紧缩性货币政策冲击对中国金融市场和宏观经济造成的负面影响,需要深入分析和把握美联储货币政策动向发生改变的原因和本质,在坚持货币政策“以我为主”的同时,密切关注和警惕美联储紧缩性货币政策冲击可能产生的负面影响,并不断深化人民币汇率改革,保证人民币汇率弹性适度和调整空间充足。
