Mobile Crowd Sensing(MCS)is an emerging paradigm that leverages sensor-equipped smart devices to collect data.The introduction of MCS also poses some challenges such as providing highquality data for upper layer MCS a...Mobile Crowd Sensing(MCS)is an emerging paradigm that leverages sensor-equipped smart devices to collect data.The introduction of MCS also poses some challenges such as providing highquality data for upper layer MCS applications,which requires adequate participants.However,recruiting enough participants to provide the sensing data for free is hard for the MCS platform under a limited budget,which may lead to a low coverage ratio of sensing area.This paper proposes a novel method to choose participants uniformly distributed in a specific sensing area based on the mobility patterns of mobile users.The method consists of two steps:(1)A second-order Markov chain is used to predict the next positions of users,and select users whose next places are in the target sensing area to form a candidate pool.(2)The Average Entropy(DAE)is proposed to measure the distribution of participants.The participant maximizing the DAE value of a specific sensing area with different granular sub-areas is chosen to maximize the coverage ratio of the sensing area.Experimental results show that the proposed method can maximize the coverage ratio of a sensing area under different partition granularities.展开更多
An improved low distortion sigma-delta ADC（analog-to-digital converter） for wireless local area network standards is presented.A feed-forward MASH 2-2 multi-bit cascaded sigma-delta ADC is adopted; however,this work...An improved low distortion sigma-delta ADC（analog-to-digital converter） for wireless local area network standards is presented.A feed-forward MASH 2-2 multi-bit cascaded sigma-delta ADC is adopted; however,this work shows a much better performance than the ADCs which have been presented to date by adding a feedback factor in the second stage to improve the performance of the in-band SNDR（signal to noise and distortion ratio）,using 4-bit ADCs in both stages to minimize the quantization noise.Data weighted averaging technology is therefore used to decrease the mismatch noise induced by the 4-bit DACs,which improves the SFDR（spurious free dynamic range） of the ADC. The modulator has been implemented by a 0.18μm CMOS process and operates at a single 1.8 V supply voltage. Experimental results show that for a 1.25 MHz @-6 dBFS input signal at 160 MHz sampling frequency,the improved ADC with all non-idealities considered achieves a peak SNDR of 80.9 dB and an SFDR of 87 dB,and the effective number of bits is 13.15 bits.展开更多
基金supported by the Open Foundation of State key Laboratory of Networking and Switching Technology(Beijing University of Posts and Telecommunications)(SKLNST-2021-1-18)the General Program of Natural Science Foundation of Chongqing(cstc2020jcyj-msxmX1021)+1 种基金the Science and Technology Research Program of Chongqing Municipal Education Commission(KJZD-K202000602)Chongqing graduate research and innovation project(CYS22478).
文摘Mobile Crowd Sensing(MCS)is an emerging paradigm that leverages sensor-equipped smart devices to collect data.The introduction of MCS also poses some challenges such as providing highquality data for upper layer MCS applications,which requires adequate participants.However,recruiting enough participants to provide the sensing data for free is hard for the MCS platform under a limited budget,which may lead to a low coverage ratio of sensing area.This paper proposes a novel method to choose participants uniformly distributed in a specific sensing area based on the mobility patterns of mobile users.The method consists of two steps:(1)A second-order Markov chain is used to predict the next positions of users,and select users whose next places are in the target sensing area to form a candidate pool.(2)The Average Entropy(DAE)is proposed to measure the distribution of participants.The participant maximizing the DAE value of a specific sensing area with different granular sub-areas is chosen to maximize the coverage ratio of the sensing area.Experimental results show that the proposed method can maximize the coverage ratio of a sensing area under different partition granularities.
基金supported by National Natural Science Foundation of the China(Nos.60725415,60971066 )the National High-Tech Programs of China(Nos.2009AA01Z258,2009AA01Z260)
文摘An improved low distortion sigma-delta ADC（analog-to-digital converter） for wireless local area network standards is presented.A feed-forward MASH 2-2 multi-bit cascaded sigma-delta ADC is adopted; however,this work shows a much better performance than the ADCs which have been presented to date by adding a feedback factor in the second stage to improve the performance of the in-band SNDR（signal to noise and distortion ratio）,using 4-bit ADCs in both stages to minimize the quantization noise.Data weighted averaging technology is therefore used to decrease the mismatch noise induced by the 4-bit DACs,which improves the SFDR（spurious free dynamic range） of the ADC. The modulator has been implemented by a 0.18μm CMOS process and operates at a single 1.8 V supply voltage. Experimental results show that for a 1.25 MHz @-6 dBFS input signal at 160 MHz sampling frequency,the improved ADC with all non-idealities considered achieves a peak SNDR of 80.9 dB and an SFDR of 87 dB,and the effective number of bits is 13.15 bits.
