Aiming at solving the blind estimation problem of dispreading spectrum sequence under low SNR, a spread-spectrum estimation algorithm based subspace tracking is studied in this paper. This method avoids the direct eig...Aiming at solving the blind estimation problem of dispreading spectrum sequence under low SNR, a spread-spectrum estimation algorithm based subspace tracking is studied in this paper. This method avoids the direct eigen decomposition, using the sliding window technique to obtain the code synchronization, then use segmentation subspace tracking method estimate spreading sequence and splice in a certain order to achieve pseudo-code blind estimation. The results show that the algorithm can complete the accurate estimation of PN code sequence in low SNR conditions, reduce the amount of data storage and be easy hardware implementation展开更多
This paper analyzed the security of constant dimensional subspace code against wiretap attacks. The security was measured in the probability with which an eavesdropper guessed the source message successfully. With the...This paper analyzed the security of constant dimensional subspace code against wiretap attacks. The security was measured in the probability with which an eavesdropper guessed the source message successfully. With the methods of linear algebra and combinatorics, an analytic solution of the probability was obtained. Performance of subspace code was compared to several secure network coding schemes from the perspective of security, flexibility, complexity, and independence, etc. The comparison showed subspace code did not have perfect security, but it achieved probabilistic security with low complexity. As a result, subspace code was suitable to the applications with limited computation and moderate security requirement.展开更多
As the Projection Approximation Subspace Tracking with deflation(PASTd) algorithm is sensitive to impulsive noise, an improved subspace tracking algorithm is proposed and applied to blind adaptive multi-user detection...As the Projection Approximation Subspace Tracking with deflation(PASTd) algorithm is sensitive to impulsive noise, an improved subspace tracking algorithm is proposed and applied to blind adaptive multi-user detection. Simulation results show that the improved PASTd algorithm not only remains the properties of the conventional PASTdalgorithm, but also has good Bit Error Rate(BER) performance in impulsive noise environment, thus it can effectively improve the system performance.展开更多
Vertical layered space-time codes have demonstrated the enormous potential to accommodate rapid flow data. Thus far, vertical layered space-time codes assumed that perfect estimates of current channel fading condition...Vertical layered space-time codes have demonstrated the enormous potential to accommodate rapid flow data. Thus far, vertical layered space-time codes assumed that perfect estimates of current channel fading conditions are available at the receiver. However, increasing the number of transmit antennas increases the required training interval and reduces the available time in which data may be transmitted before the fading coefficients change. In this paper, a vertical layered space-time code is proposed. By applying the subspace method to the layered space-time code, the symbols can be detected without training symbols and channel estimates at the transmitter or the receiver. Monte Carlo simulations show that performance can approach that of the detection method with the knowledge of the channel.展开更多
针对长短码直接扩频序列(long and short code direct sequence spread spectrum, LSC-DSSS)信号序列估计难题,在已知LSC-DSSS信号参数的条件下,提出一种基于新信息准则(novel information criterion, NIC)神经网络联合梅西算法的长短...针对长短码直接扩频序列(long and short code direct sequence spread spectrum, LSC-DSSS)信号序列估计难题,在已知LSC-DSSS信号参数的条件下,提出一种基于新信息准则(novel information criterion, NIC)神经网络联合梅西算法的长短码信号序列估计方法。将LSC-DSSS信号输入NIC神经网络以估计随机采样起点,再通过不断输入数据训练NIC神经网络权值向量。当网络收敛时,权值向量的符号值即为LSC-DSSS信号的复合码序列片段。使用延迟相乘,消除幅度模糊与短扩频码序列的影响,再利用梅西算法获得扰码序列的生成多项式。仿真实验结果表明,NIC神经网络较特征值分解法的抗噪声性能提高6 dB,同时较Hebbian准则神经网络所需学习组数减少50%。展开更多
In this paper,we firstly construct several new kinds of Sidon spaces and Sidon sets by investigating some known results.Secondly,using these Sidon spaces,we will present a construction of cyclic subspace codes with ca...In this paper,we firstly construct several new kinds of Sidon spaces and Sidon sets by investigating some known results.Secondly,using these Sidon spaces,we will present a construction of cyclic subspace codes with cardinality τ,q^(n)-1/q-1 and minimum distance 2k-2,whereτis a positive integer.We further-more give some cyclic subspace codes with size 2τ·q^(n)-1/q-1 and without changing the minimum distance 2k-2.展开更多
文摘Aiming at solving the blind estimation problem of dispreading spectrum sequence under low SNR, a spread-spectrum estimation algorithm based subspace tracking is studied in this paper. This method avoids the direct eigen decomposition, using the sliding window technique to obtain the code synchronization, then use segmentation subspace tracking method estimate spreading sequence and splice in a certain order to achieve pseudo-code blind estimation. The results show that the algorithm can complete the accurate estimation of PN code sequence in low SNR conditions, reduce the amount of data storage and be easy hardware implementation
文摘This paper analyzed the security of constant dimensional subspace code against wiretap attacks. The security was measured in the probability with which an eavesdropper guessed the source message successfully. With the methods of linear algebra and combinatorics, an analytic solution of the probability was obtained. Performance of subspace code was compared to several secure network coding schemes from the perspective of security, flexibility, complexity, and independence, etc. The comparison showed subspace code did not have perfect security, but it achieved probabilistic security with low complexity. As a result, subspace code was suitable to the applications with limited computation and moderate security requirement.
文摘As the Projection Approximation Subspace Tracking with deflation(PASTd) algorithm is sensitive to impulsive noise, an improved subspace tracking algorithm is proposed and applied to blind adaptive multi-user detection. Simulation results show that the improved PASTd algorithm not only remains the properties of the conventional PASTdalgorithm, but also has good Bit Error Rate(BER) performance in impulsive noise environment, thus it can effectively improve the system performance.
基金Partially supported by the National Natural Sciences Foundation (No.69872029) and the Research Fund for Doctoral Program of Higher Education (No.1999069808) of China
文摘Vertical layered space-time codes have demonstrated the enormous potential to accommodate rapid flow data. Thus far, vertical layered space-time codes assumed that perfect estimates of current channel fading conditions are available at the receiver. However, increasing the number of transmit antennas increases the required training interval and reduces the available time in which data may be transmitted before the fading coefficients change. In this paper, a vertical layered space-time code is proposed. By applying the subspace method to the layered space-time code, the symbols can be detected without training symbols and channel estimates at the transmitter or the receiver. Monte Carlo simulations show that performance can approach that of the detection method with the knowledge of the channel.
文摘针对长短码直接扩频序列(long and short code direct sequence spread spectrum, LSC-DSSS)信号序列估计难题,在已知LSC-DSSS信号参数的条件下,提出一种基于新信息准则(novel information criterion, NIC)神经网络联合梅西算法的长短码信号序列估计方法。将LSC-DSSS信号输入NIC神经网络以估计随机采样起点,再通过不断输入数据训练NIC神经网络权值向量。当网络收敛时,权值向量的符号值即为LSC-DSSS信号的复合码序列片段。使用延迟相乘,消除幅度模糊与短扩频码序列的影响,再利用梅西算法获得扰码序列的生成多项式。仿真实验结果表明,NIC神经网络较特征值分解法的抗噪声性能提高6 dB,同时较Hebbian准则神经网络所需学习组数减少50%。
基金supported by the National Natural Science Foundation of China(Grant Nos.11771007,12171241).
文摘In this paper,we firstly construct several new kinds of Sidon spaces and Sidon sets by investigating some known results.Secondly,using these Sidon spaces,we will present a construction of cyclic subspace codes with cardinality τ,q^(n)-1/q-1 and minimum distance 2k-2,whereτis a positive integer.We further-more give some cyclic subspace codes with size 2τ·q^(n)-1/q-1 and without changing the minimum distance 2k-2.
