研究在目的节点进行协作干扰的全双工不可信中继传输系统中,在信道状态信息(channel state information,CSI)存在随机误差的情况下,以最大化系统可达保密速率为目标的功率分配问题。为了研究提高全双工不可信中继传输系统的保密性能的...研究在目的节点进行协作干扰的全双工不可信中继传输系统中,在信道状态信息(channel state information,CSI)存在随机误差的情况下,以最大化系统可达保密速率为目标的功率分配问题。为了研究提高全双工不可信中继传输系统的保密性能的功率分配方案,先推导系统可达保密速率的上界,针对随机信道状态信息的误差再求该保密速率上界的期望,即平均保密速率(average secrecy rate,ASR)。在此基础上,考虑源节点发送信息信号和目的节点发送人工噪声总功率的约束,以最大化ASR为优化目标,通过黄金分割法优化源节点和目的节点的功率分配。仿真结果表明,相比于固定功率分配因子和不考虑随机信道系数误差影响的功率分配方案,考虑信道的随机误差优化功率分配方案能有效提高系统的可达保密速率。展开更多
无线通信中,信道系数变化对均衡器的均衡具有较大的影响。在无噪和有噪环境中,分别采用直接求逆和广义求逆方法计算信道系数托普利兹矩阵的条件数,将条件数与均衡后得到的信号干扰噪声比(Signal to Interference plus Noise Ratio,SINR...无线通信中,信道系数变化对均衡器的均衡具有较大的影响。在无噪和有噪环境中,分别采用直接求逆和广义求逆方法计算信道系数托普利兹矩阵的条件数,将条件数与均衡后得到的信号干扰噪声比(Signal to Interference plus Noise Ratio,SINR)进行对比,探究因信道系数变化趋势带来的一系列影响,并通过不同的求逆方法来改善迫零均衡的均衡效果。仿真实验结果表明,广义求逆方法解决了因信道系数趋势先上升后下降引起的信道系数的托普利兹矩阵变为奇异矩阵的问题;可以根据信道系数的托普利兹矩阵的条件数,来判断信道系数使用哪种合适的求逆方法。展开更多
The scattering of plane surface waves by bottom undulations in channel flow consisting of two layers is investigated by assuming that the bed of the channel is composed of porous material. The upper surface of the flu...The scattering of plane surface waves by bottom undulations in channel flow consisting of two layers is investigated by assuming that the bed of the channel is composed of porous material. The upper surface of the fluid is bounded by a rigid lid and the channel is unbounded in the horizontal directions. There exists only one wave mode corresponding to an internal wave. For small undulations, a simplified perturbation analysis is used to obtain first order reflection and transmission coefficients in terms of integrals involving the shape function describing the bottom. For sinusoidal bottom undulations and exponentially decaying bottom topography, the first order coefficients are computed. In the case of sinusoidal bottom the first order transmission coefficient is found to vanish identically. The numerical results are depicted graphically in a number of figures.展开更多
This is the second of a three-part series of papers which presents the principle and architecture of the CRNM, a trajectory-oriented, carriageway-based road network data model. The first part of the series has introdu...This is the second of a three-part series of papers which presents the principle and architecture of the CRNM, a trajectory-oriented, carriageway-based road network data model. The first part of the series has introduced a general background of building trajectory-oriented road network data models, including motivation, related works, and basic concepts. Based on it, this paper describs the CRNM in detail. At first, the notion of basic roadway entity is proposed and discussed. Secondly, carriageway is selected as the basic roadway entity after compared with other kinds of roadway, and approaches to representing other roadways with carriageways are introduced. At last, an overall architecture of the CRNM is proposed.展开更多
This paper introduces a frequency-hopped (FH) communication system to anti-intersymbol interferences (ISI) caused by the multipath propagation in shallow-water acoustic channels, and uses high-speed digital signal pro...This paper introduces a frequency-hopped (FH) communication system to anti-intersymbol interferences (ISI) caused by the multipath propagation in shallow-water acoustic channels, and uses high-speed digital signal processor (DSP) and serial ADC (MAX121) chip to demodulate received signal efficiently based Fast Fourier Transform (FFT) algorithm. The field experimental results show: a data rate of 1Kbit/s with the bit error rates on the order of 10 -4 is demonstrated at 2000 m in the shallow-water acoustic channel of Xiamen harbor, and the key techniques of the system is analyzed in the paper.展开更多
A new channel estimation and data detection joint algorithm is proposed for multi-input multi-output （MIMO） - orthogonal frequency division multiplexing （OFDM） system using linear minimum mean square error （LMMSE...A new channel estimation and data detection joint algorithm is proposed for multi-input multi-output （MIMO） - orthogonal frequency division multiplexing （OFDM） system using linear minimum mean square error （LMMSE）- based space-alternating generalized expectation-maximization （SAGE） algorithm. In the proposed algorithm, every sub-frame of the MIMO-OFDM system is divided into some OFDM sub-blocks and the LMMSE-based SAGE algorithm in each sub-block is used. At the head of each sub-flame, we insert training symbols which are used in the initial estimation at the beginning. Channel estimation of the previous sub-block is applied to the initial estimation in the current sub-block by the maximum-likelihood （ML） detection to update channel estimatjon and data detection by iteration until converge. Then all the sub-blocks can be finished in turn. Simulation results show that the proposed algorithm can improve the bit error rate （BER） performance.展开更多
Based on the tortuous-expanding path/channel model,a micro-mechanism model for porous media is developed.The proposed model is expressed as a function of tortuosity,porosity,resistance coefficient,and fluid properties...Based on the tortuous-expanding path/channel model,a micro-mechanism model for porous media is developed.The proposed model is expressed as a function of tortuosity,porosity,resistance coefficient,and fluid properties.Every parameter in the proposed model has clear physical meaning.The results show that the model predictions are ingood agreement with those from the existing experimental data.展开更多
文摘研究在目的节点进行协作干扰的全双工不可信中继传输系统中,在信道状态信息(channel state information,CSI)存在随机误差的情况下,以最大化系统可达保密速率为目标的功率分配问题。为了研究提高全双工不可信中继传输系统的保密性能的功率分配方案,先推导系统可达保密速率的上界,针对随机信道状态信息的误差再求该保密速率上界的期望,即平均保密速率(average secrecy rate,ASR)。在此基础上,考虑源节点发送信息信号和目的节点发送人工噪声总功率的约束,以最大化ASR为优化目标,通过黄金分割法优化源节点和目的节点的功率分配。仿真结果表明,相比于固定功率分配因子和不考虑随机信道系数误差影响的功率分配方案,考虑信道的随机误差优化功率分配方案能有效提高系统的可达保密速率。
文摘无线通信中,信道系数变化对均衡器的均衡具有较大的影响。在无噪和有噪环境中,分别采用直接求逆和广义求逆方法计算信道系数托普利兹矩阵的条件数,将条件数与均衡后得到的信号干扰噪声比(Signal to Interference plus Noise Ratio,SINR)进行对比,探究因信道系数变化趋势带来的一系列影响,并通过不同的求逆方法来改善迫零均衡的均衡效果。仿真实验结果表明,广义求逆方法解决了因信道系数趋势先上升后下降引起的信道系数的托普利兹矩阵变为奇异矩阵的问题;可以根据信道系数的托普利兹矩阵的条件数,来判断信道系数使用哪种合适的求逆方法。
文摘The scattering of plane surface waves by bottom undulations in channel flow consisting of two layers is investigated by assuming that the bed of the channel is composed of porous material. The upper surface of the fluid is bounded by a rigid lid and the channel is unbounded in the horizontal directions. There exists only one wave mode corresponding to an internal wave. For small undulations, a simplified perturbation analysis is used to obtain first order reflection and transmission coefficients in terms of integrals involving the shape function describing the bottom. For sinusoidal bottom undulations and exponentially decaying bottom topography, the first order coefficients are computed. In the case of sinusoidal bottom the first order transmission coefficient is found to vanish identically. The numerical results are depicted graphically in a number of figures.
文摘This is the second of a three-part series of papers which presents the principle and architecture of the CRNM, a trajectory-oriented, carriageway-based road network data model. The first part of the series has introduced a general background of building trajectory-oriented road network data models, including motivation, related works, and basic concepts. Based on it, this paper describs the CRNM in detail. At first, the notion of basic roadway entity is proposed and discussed. Secondly, carriageway is selected as the basic roadway entity after compared with other kinds of roadway, and approaches to representing other roadways with carriageways are introduced. At last, an overall architecture of the CRNM is proposed.
文摘This paper introduces a frequency-hopped (FH) communication system to anti-intersymbol interferences (ISI) caused by the multipath propagation in shallow-water acoustic channels, and uses high-speed digital signal processor (DSP) and serial ADC (MAX121) chip to demodulate received signal efficiently based Fast Fourier Transform (FFT) algorithm. The field experimental results show: a data rate of 1Kbit/s with the bit error rates on the order of 10 -4 is demonstrated at 2000 m in the shallow-water acoustic channel of Xiamen harbor, and the key techniques of the system is analyzed in the paper.
基金Supported by the National Natural Science Foundation of China （No. 61001105）, the National Science and Technology Major Projects （No. 2011ZX03001- 007- 03） and Beijing Natural Science Foundation （No. 4102043）.
文摘A new channel estimation and data detection joint algorithm is proposed for multi-input multi-output （MIMO） - orthogonal frequency division multiplexing （OFDM） system using linear minimum mean square error （LMMSE）- based space-alternating generalized expectation-maximization （SAGE） algorithm. In the proposed algorithm, every sub-frame of the MIMO-OFDM system is divided into some OFDM sub-blocks and the LMMSE-based SAGE algorithm in each sub-block is used. At the head of each sub-flame, we insert training symbols which are used in the initial estimation at the beginning. Channel estimation of the previous sub-block is applied to the initial estimation in the current sub-block by the maximum-likelihood （ML） detection to update channel estimatjon and data detection by iteration until converge. Then all the sub-blocks can be finished in turn. Simulation results show that the proposed algorithm can improve the bit error rate （BER） performance.
基金Supported by National Nature Science Foundation of China under Grant Nos.40672156 and D0624005the National Basic Research Program (973 Program) under Grant No.2006CB202200
文摘Based on the tortuous-expanding path/channel model,a micro-mechanism model for porous media is developed.The proposed model is expressed as a function of tortuosity,porosity,resistance coefficient,and fluid properties.Every parameter in the proposed model has clear physical meaning.The results show that the model predictions are ingood agreement with those from the existing experimental data.
