A two-stage automatic key frame selection method is proposed to enhance stitching speed and quality for UAV aerial videos. In the first stage, to reduce redundancy, the overlapping rate of the UAV aerial video sequenc...A two-stage automatic key frame selection method is proposed to enhance stitching speed and quality for UAV aerial videos. In the first stage, to reduce redundancy, the overlapping rate of the UAV aerial video sequence within the sampling period is calculated. Lagrange interpolation is used to fit the overlapping rate curve of the sequence. An empirical threshold for the overlapping rate is then applied to filter candidate key frames from the sequence. In the second stage, the principle of minimizing remapping spots is used to dynamically adjust and determine the final key frame close to the candidate key frames. Comparative experiments show that the proposed method significantly improves stitching speed and accuracy by more than 40%.展开更多
Efficient anti-jamming rateless coding based on cognitive Orthogonal Frequency Division Multiplexing (OFDM) modulation in Cognitive Radio Network (CRN) is mainly discussed. Rateless coding with small redundancy and lo...Efficient anti-jamming rateless coding based on cognitive Orthogonal Frequency Division Multiplexing (OFDM) modulation in Cognitive Radio Network (CRN) is mainly discussed. Rateless coding with small redundancy and low complexity is presented, and the optimal design methods of building rateless codes are also proposed. In CRN, anti-jamming rateless coding could recover the lost packets in parallel channels of cognitive OFDM, thus it protects Secondary Users (SUs) from the in-terference by Primary Users (PUs) efficiently. Frame Error Rate (FER) and throughput performance of SU employing anti-jamming rateless coding are analyzed in detail. Performance comparison between rateless coding and piecewise coding are also presented. It is shown that, anti-jamming rateless coding provides low FER and Word Error Rate (WER) performance with uniform sub-channel selection. Meanwhile, it is also verified that, in higher jamming rate and longer code redundancy scenario, rateless coding method could achieve better FER and throughput performance than another anti-jamming coding schemes.展开更多
The pilotless frame synchronization approach and implementations of LDPC code are the crucial issue of LDPC decoder. The Maximum-A-Posteriori probability( MAP) decoder has a perfect frame synchronization error rate( F...The pilotless frame synchronization approach and implementations of LDPC code are the crucial issue of LDPC decoder. The Maximum-A-Posteriori probability( MAP) decoder has a perfect frame synchronization error rate( FSER) performance. In this paper,a theoretical derivation of the FSER performance of pilotless frame synchronization for LDPC code is presented. The FSER performance by theoretical analysis coincides well with that by simulation in additive white Gaussian channel and Rician fading channel. So it is estimated the FSER performance of an LDPC code by theoretical analysis can be used instead of the simulations which are much more time-consuming.展开更多
基于通信的列车控制(Communication-Based Train Control,CBTC)系统是一种采用先进的通信、计算机技术,连续控制、监测列车运行的列车控制系统.为了提高CBTC系统的传输效率,将正交频分复用技术(Orthogonal Frequency Division Multiplex...基于通信的列车控制(Communication-Based Train Control,CBTC)系统是一种采用先进的通信、计算机技术,连续控制、监测列车运行的列车控制系统.为了提高CBTC系统的传输效率,将正交频分复用技术(Orthogonal Frequency Division Multiplexing,OFDM)运用于CBTC系统,从OFDM系统的工作原理出发,研究了列车速度对于OFDM系统子载波非正交性的影响,并以无线局域网(Wireless Local Area Networks,WLAN)技术中的OFDM参数为例,对列车速度引起的信道相干时间变化进行了深入分析与计算.理论计算与仿真结果表明:列车速度对子载波间正交性的影响可以忽略不计;在同样报文长度、不同列车速度下,最低的传输速率并不一定能得到最低的误帧率(Frame Error Rate,FER);通信系统应该根据信道时变情况以及报文长度分别选择不同的传输速率以得到最低的FER.展开更多
针对中国毫米波频段(45GHz),制定下一代IEEE 802.11aj无线局域网(Wireless Local Area Network,WLAN)协议标准通信系统的物理层结构及发射机发送方式,研究了一种新的适用于该标准的循环移位分集(Cyclic Shift Diversity,CSD)方案,该方...针对中国毫米波频段(45GHz),制定下一代IEEE 802.11aj无线局域网(Wireless Local Area Network,WLAN)协议标准通信系统的物理层结构及发射机发送方式,研究了一种新的适用于该标准的循环移位分集(Cyclic Shift Diversity,CSD)方案,该方案在不增加接收机额外复杂度的前提下能够获得较好的性能。同时,本文对通信系统在各种调制和编码方式(Modulation and Coding Scheme,MCS)下的性能进行了仿真和评估。结果表明,在将系统发射功率控制在20d B时,采用码率为1/2的16-QAM调制方式可以在保证误帧率性能的同时获得较高的吞吐率。展开更多
文摘A two-stage automatic key frame selection method is proposed to enhance stitching speed and quality for UAV aerial videos. In the first stage, to reduce redundancy, the overlapping rate of the UAV aerial video sequence within the sampling period is calculated. Lagrange interpolation is used to fit the overlapping rate curve of the sequence. An empirical threshold for the overlapping rate is then applied to filter candidate key frames from the sequence. In the second stage, the principle of minimizing remapping spots is used to dynamically adjust and determine the final key frame close to the candidate key frames. Comparative experiments show that the proposed method significantly improves stitching speed and accuracy by more than 40%.
基金Supported by the National Natural Science Foundation of China (No. 60972039)the Scientific Planning Project of Zhejiang Province entitled "Research and Development of Smart Antenna for the Next Generation Mobile Com-munications Based on TDD"the Young Staff Startup Research Foundation of Hangzhou Dianzi University entitled "Research on Key Technologies of Resource Allocation in Cognitive Radio Networks Based on Multicarrier Modulation"
文摘Efficient anti-jamming rateless coding based on cognitive Orthogonal Frequency Division Multiplexing (OFDM) modulation in Cognitive Radio Network (CRN) is mainly discussed. Rateless coding with small redundancy and low complexity is presented, and the optimal design methods of building rateless codes are also proposed. In CRN, anti-jamming rateless coding could recover the lost packets in parallel channels of cognitive OFDM, thus it protects Secondary Users (SUs) from the in-terference by Primary Users (PUs) efficiently. Frame Error Rate (FER) and throughput performance of SU employing anti-jamming rateless coding are analyzed in detail. Performance comparison between rateless coding and piecewise coding are also presented. It is shown that, anti-jamming rateless coding provides low FER and Word Error Rate (WER) performance with uniform sub-channel selection. Meanwhile, it is also verified that, in higher jamming rate and longer code redundancy scenario, rateless coding method could achieve better FER and throughput performance than another anti-jamming coding schemes.
基金Supported by the National Natural Science Foundation of China(No.61271230,61472190)the Open Research Fund of National Mobile Communications Research Laboratory,Southeast University(No.2013D02)the Open Research Fund of National Key Laboratory of Electromagnetic Environment,China Research Institute of Radiowave Propagation(No.201500013)
文摘The pilotless frame synchronization approach and implementations of LDPC code are the crucial issue of LDPC decoder. The Maximum-A-Posteriori probability( MAP) decoder has a perfect frame synchronization error rate( FSER) performance. In this paper,a theoretical derivation of the FSER performance of pilotless frame synchronization for LDPC code is presented. The FSER performance by theoretical analysis coincides well with that by simulation in additive white Gaussian channel and Rician fading channel. So it is estimated the FSER performance of an LDPC code by theoretical analysis can be used instead of the simulations which are much more time-consuming.
文摘基于通信的列车控制(Communication-Based Train Control,CBTC)系统是一种采用先进的通信、计算机技术,连续控制、监测列车运行的列车控制系统.为了提高CBTC系统的传输效率,将正交频分复用技术(Orthogonal Frequency Division Multiplexing,OFDM)运用于CBTC系统,从OFDM系统的工作原理出发,研究了列车速度对于OFDM系统子载波非正交性的影响,并以无线局域网(Wireless Local Area Networks,WLAN)技术中的OFDM参数为例,对列车速度引起的信道相干时间变化进行了深入分析与计算.理论计算与仿真结果表明:列车速度对子载波间正交性的影响可以忽略不计;在同样报文长度、不同列车速度下,最低的传输速率并不一定能得到最低的误帧率(Frame Error Rate,FER);通信系统应该根据信道时变情况以及报文长度分别选择不同的传输速率以得到最低的FER.
文摘针对中国毫米波频段(45GHz),制定下一代IEEE 802.11aj无线局域网(Wireless Local Area Network,WLAN)协议标准通信系统的物理层结构及发射机发送方式,研究了一种新的适用于该标准的循环移位分集(Cyclic Shift Diversity,CSD)方案,该方案在不增加接收机额外复杂度的前提下能够获得较好的性能。同时,本文对通信系统在各种调制和编码方式(Modulation and Coding Scheme,MCS)下的性能进行了仿真和评估。结果表明,在将系统发射功率控制在20d B时,采用码率为1/2的16-QAM调制方式可以在保证误帧率性能的同时获得较高的吞吐率。
