患者女,51岁,因“近2个月出现体力下降,呼吸困难较前加重,夜间为著,伴双下肢、下腹部明显水肿”入院。自诉发作性胸闷、呼吸困难20余年,1年前无明显诱因出现双脚水肿,其后逐渐加重,双侧小腿、大腿出现水肿;否认家族遗传病史。入院体格检...患者女,51岁,因“近2个月出现体力下降,呼吸困难较前加重,夜间为著,伴双下肢、下腹部明显水肿”入院。自诉发作性胸闷、呼吸困难20余年,1年前无明显诱因出现双脚水肿,其后逐渐加重,双侧小腿、大腿出现水肿;否认家族遗传病史。入院体格检查:血压106/69 mm Hg(1 mm Hg=0.133 kPa),心率101次/min,律绝对不齐,第一心音强弱不等。双下肢及下腹部指凹性水肿。心电图示:心房颤动,前间壁T波改变。展开更多
A modified time domain interpolation method is proposed for orthogonal frequency division multiplexing(OFDM)systems to address the problem that time domain interpolation in the least square(LS)channel estimation metho...A modified time domain interpolation method is proposed for orthogonal frequency division multiplexing(OFDM)systems to address the problem that time domain interpolation in the least square(LS)channel estimation method based on comb-type pilots cannot choose the pilot spacing flexibly.Firstly,the estimated channel frequency response(CFR)at pilot positions in the frequency domain is obtained by LS channel estimation based on comb-type pilots,and the estimated channel impulse response(CIR)in the time domain is obtained by linear interpolation and inverse fast Fourier transform(IFFT).Secondly,the error of the estimated CIR obtained by linear interpolation is analyzed by theoretical deduction,and a method for correcting it is proposed.Finally,an estimated CFR at all subcarrier positions in the frequency domain is obtained by performing zero padding in the time domain and fast Fourier transform(FFT)on the modified CIR.The simulation results suggest that the proposed method gives similar performance to time domain interpolation,yet it does not need to meet the condition of time domain interpolation that the number of subcarriers must be an integral multiple of pilot spacing to use it.The proposed method allows for flexible pilot spacing,reducing the number of pilots and the consumption of subcarriers used for channel estimation.展开更多
文摘患者女,51岁,因“近2个月出现体力下降,呼吸困难较前加重,夜间为著,伴双下肢、下腹部明显水肿”入院。自诉发作性胸闷、呼吸困难20余年,1年前无明显诱因出现双脚水肿,其后逐渐加重,双侧小腿、大腿出现水肿;否认家族遗传病史。入院体格检查:血压106/69 mm Hg(1 mm Hg=0.133 kPa),心率101次/min,律绝对不齐,第一心音强弱不等。双下肢及下腹部指凹性水肿。心电图示:心房颤动,前间壁T波改变。
基金The National Natural Science Foundation of China(No.51975117)。
文摘A modified time domain interpolation method is proposed for orthogonal frequency division multiplexing(OFDM)systems to address the problem that time domain interpolation in the least square(LS)channel estimation method based on comb-type pilots cannot choose the pilot spacing flexibly.Firstly,the estimated channel frequency response(CFR)at pilot positions in the frequency domain is obtained by LS channel estimation based on comb-type pilots,and the estimated channel impulse response(CIR)in the time domain is obtained by linear interpolation and inverse fast Fourier transform(IFFT).Secondly,the error of the estimated CIR obtained by linear interpolation is analyzed by theoretical deduction,and a method for correcting it is proposed.Finally,an estimated CFR at all subcarrier positions in the frequency domain is obtained by performing zero padding in the time domain and fast Fourier transform(FFT)on the modified CIR.The simulation results suggest that the proposed method gives similar performance to time domain interpolation,yet it does not need to meet the condition of time domain interpolation that the number of subcarriers must be an integral multiple of pilot spacing to use it.The proposed method allows for flexible pilot spacing,reducing the number of pilots and the consumption of subcarriers used for channel estimation.
