为提高现有直接信息均匀压缩采样(Analog to information conversion,AIC)的观测效率和性能,在能量准则下,提出非均匀信息采集(Non-uniform information acquisition,NUIA),充分利用信息的重要性先验,即对信号随机调制后,依据能量进行...为提高现有直接信息均匀压缩采样(Analog to information conversion,AIC)的观测效率和性能,在能量准则下,提出非均匀信息采集(Non-uniform information acquisition,NUIA),充分利用信息的重要性先验,即对信号随机调制后,依据能量进行变速率的采集,能量越大的信号段采样速率越高,反之亦然。结合支撑域扩充、剪枝的思路提出变速匹配追踪(Variable rate matching pursuit,VRMP)算法,通过引入非均匀观测的先验支撑集,并在追踪过程中将其与迭代估计出的支撑集相并,提高了重构精度。理论分析和实验结果表明了NUIA-VRMP的有效性。特别地,相比于常规AIC的子空间追踪重构,NUIA-VRMP的组合能在低采样速率条件(如20%的Nyquist速率)下获得50dB的重构增益。展开更多
It has been shown that analog-to-information conversion(AIC) is an efficient scheme to perform sub-Nyquist sampling of pulsed radar echoes. However, it is often impractical, if not infeasible, to reconstruct full-rang...It has been shown that analog-to-information conversion(AIC) is an efficient scheme to perform sub-Nyquist sampling of pulsed radar echoes. However, it is often impractical, if not infeasible, to reconstruct full-range Nyquist samples because of huge storage and computational load requirements. Based on the analyses of AIC measurement system, this paper develops a novel segment-sliding reconstruction(Seg SR) scheme to effectively reconstruct the Nyquist samples. The Seg SR performs segment-by-segment reconstruction in a sliding mode and can be implemented in real time. An important characteristic that distinguishes the proposed Seg SR from existing methods is that the measurement matrix in each segment satisfies the restricted isometry property(RIP) condition. Partial support in the previous segment can be incorporated into the estimation of the Nyquist samples in the current segment. The effect of interference introduced from adjacent segments is theoretically analyzed, and it is revealed that the interference consists of two interference levels with different impacts to the signal reconstruction performance. With these observations, a two-step orthogonal matching pursuit(OMP)procedure is proposed for segment reconstruction, which takes into account different interference levels and partially known support of the previous segment. The proposed Seg SR scheme achieves near-optimal reconstruction performance with a significant reduction of computational loads and storage requirements. Theoretical analyses and simulations verify its effectiveness.展开更多
The design and realization of a videoconference system based on international recommendation are introduced in this paper, and the hardware implementation of video codec based on ITU-T H. 261 is briefly discussed. Fur...The design and realization of a videoconference system based on international recommendation are introduced in this paper, and the hardware implementation of video codec based on ITU-T H. 261 is briefly discussed. Furthermore, the buffer control method and the adaptive control strategy for quantization are proposed, which are adaptive and robust. This system can be operated under the transmission rate ranging from 128kb/s to 2Mb/s. With these strategies for the videoconference system, the high quality image is obtained. The time delay of the system is about half a second.展开更多
文摘为提高现有直接信息均匀压缩采样(Analog to information conversion,AIC)的观测效率和性能,在能量准则下,提出非均匀信息采集(Non-uniform information acquisition,NUIA),充分利用信息的重要性先验,即对信号随机调制后,依据能量进行变速率的采集,能量越大的信号段采样速率越高,反之亦然。结合支撑域扩充、剪枝的思路提出变速匹配追踪(Variable rate matching pursuit,VRMP)算法,通过引入非均匀观测的先验支撑集,并在追踪过程中将其与迭代估计出的支撑集相并,提高了重构精度。理论分析和实验结果表明了NUIA-VRMP的有效性。特别地,相比于常规AIC的子空间追踪重构,NUIA-VRMP的组合能在低采样速率条件(如20%的Nyquist速率)下获得50dB的重构增益。
基金supported by National Natural Science Foundation of China (Grant Nos. 61171166, 61401210, 61571228)China Postdoctoral Science Foundation (Grant No. 2014M551597)
文摘It has been shown that analog-to-information conversion(AIC) is an efficient scheme to perform sub-Nyquist sampling of pulsed radar echoes. However, it is often impractical, if not infeasible, to reconstruct full-range Nyquist samples because of huge storage and computational load requirements. Based on the analyses of AIC measurement system, this paper develops a novel segment-sliding reconstruction(Seg SR) scheme to effectively reconstruct the Nyquist samples. The Seg SR performs segment-by-segment reconstruction in a sliding mode and can be implemented in real time. An important characteristic that distinguishes the proposed Seg SR from existing methods is that the measurement matrix in each segment satisfies the restricted isometry property(RIP) condition. Partial support in the previous segment can be incorporated into the estimation of the Nyquist samples in the current segment. The effect of interference introduced from adjacent segments is theoretically analyzed, and it is revealed that the interference consists of two interference levels with different impacts to the signal reconstruction performance. With these observations, a two-step orthogonal matching pursuit(OMP)procedure is proposed for segment reconstruction, which takes into account different interference levels and partially known support of the previous segment. The proposed Seg SR scheme achieves near-optimal reconstruction performance with a significant reduction of computational loads and storage requirements. Theoretical analyses and simulations verify its effectiveness.
基金the High Technology Research and Development Programme of China
文摘The design and realization of a videoconference system based on international recommendation are introduced in this paper, and the hardware implementation of video codec based on ITU-T H. 261 is briefly discussed. Furthermore, the buffer control method and the adaptive control strategy for quantization are proposed, which are adaptive and robust. This system can be operated under the transmission rate ranging from 128kb/s to 2Mb/s. With these strategies for the videoconference system, the high quality image is obtained. The time delay of the system is about half a second.
