Channel training in reconfigurable intelligent surface(RIS)-assisted communications is usually conducted in an on-off manner,resulting in unaffordable training time overhead when the number of RIS elements is large.In...Channel training in reconfigurable intelligent surface(RIS)-assisted communications is usually conducted in an on-off manner,resulting in unaffordable training time overhead when the number of RIS elements is large.In this paper,for correlated Rayleigh channels,we compare three typical training overhead reduction schemes,namely RIS element selection(Scheme 1),element grouping(Scheme 2),and statistical CSI-based phase shifts design(Scheme3).For Scheme 1 and Scheme 2,we propose two algorithms to select RIS elements(or form element groups) and determine the optimal number of activated elements(or formed groups),based on the channel correlation information only;for Scheme 3,we consider a semi-definite programming-based approach in the literature,and propose an alternative dominant eigenvector-based method for determining the RIS phase shifts vector.Via extensive simulations,we compare the achievable ergodic rates of these schemes versus the signal-to-noise ratio,the channel correlation level,and the element number-to-coherent time ratio,respectively,and discuss possible switching of the three schemes over these system parameters.At last,operation regions of the considered training overhead reduction schemes are shown in the plane characterized by the system parameters,which provides useful guidelines for practical scheme determination.展开更多
Sensing coverage is a fundamental design issue in wireless sensor networks(WSNs),while sensor scheduling ensures coverage degree to the monitored event and extends the network lifetime.In this paper,we address k-cover...Sensing coverage is a fundamental design issue in wireless sensor networks(WSNs),while sensor scheduling ensures coverage degree to the monitored event and extends the network lifetime.In this paper,we address k-coverage scheduling problem in dense WSNs,we maintain a connected k-coverage energy efficiently through a novel Hard-Core based Coordinated Scheduling(HCCS),in which hardcore is a thinning process in stochastic geometry that inhibits more than one active sensor covering any area redundantly in a minimum distance. As compared with existing coordinated scheduling,HCCS allows coordination between sensors with little communication overhead.Moreover,due to the traditional sensing models in k-coverage analysis is unsuitable to describe the characteristic of transmit channel in dense WSNs,we propose a novel sensing model integrating Rayleigh Fading and Distribution of Active sensors(RFDA),and derive the coverage measure and k-coverage probability for the monitored event under RFDA. In addition,we analyze the influence factors,i.e. the transmit condition and monitoring degree to the k-coverage probability. Finally,through Monte Carlo simulations,it is shown that the k-coverage probability of HCCS outperforms that of its random scheduling counterpart.展开更多
在n-Rayleigh信道下,研究了MRC(Maximal Ratio Combining)合并接收系统的平均码字错误率(ASEP)性能。基于矩生成函数(MGF)的方法,推导了MRC接收系统在n-Rayleigh衰落信道上采用M进制相移键控(MPSK),M进制正交幅度调制(MQAM)和M进制脉冲...在n-Rayleigh信道下,研究了MRC(Maximal Ratio Combining)合并接收系统的平均码字错误率(ASEP)性能。基于矩生成函数(MGF)的方法,推导了MRC接收系统在n-Rayleigh衰落信道上采用M进制相移键控(MPSK),M进制正交幅度调制(MQAM)和M进制脉冲幅度调制(MPAM)等几种M进制数字调制方式的ASEP的计算式。然后在不同条件下,仿真了系统的ASEP性能,仿真值与理论值相一致,理论分析的正确性得到了证明。分析结果表明:分集支路数和衰弱因子对系统的ASEP性能有重要影响。展开更多
A novel kind of multidimension symbol/sequence trellis coded modulation (TCM) based on TCM of lower coding rate has been constructed. The redundancy of this new kind of TCM is provided not only by the modulated symbo...A novel kind of multidimension symbol/sequence trellis coded modulation (TCM) based on TCM of lower coding rate has been constructed. The redundancy of this new kind of TCM is provided not only by the modulated symbol sequence but also by the PN sequences for spreading spectrum as well. The performance of direct sequence spread spectrum multiple access (DS/SSMA) system with this symbol/sequence TCM over flat Rayleigh fading channel has been investigated by theoretical analysis and numerical simulation. The results obtained in this research demonstrate the performance improvements of this system in comparison with that of the DS/SSMA system with conventional TCM under the same conditions.展开更多
基金the National Natural Science Foundation of China under Grants 62171240,61771264,62001254,61971467,the Key Research and Development Program of Jiangsu Province of China under Grant BE2021013-1the Science and Technology Program of Nantong under Grants JC2021121,JC2021017.
文摘Channel training in reconfigurable intelligent surface(RIS)-assisted communications is usually conducted in an on-off manner,resulting in unaffordable training time overhead when the number of RIS elements is large.In this paper,for correlated Rayleigh channels,we compare three typical training overhead reduction schemes,namely RIS element selection(Scheme 1),element grouping(Scheme 2),and statistical CSI-based phase shifts design(Scheme3).For Scheme 1 and Scheme 2,we propose two algorithms to select RIS elements(or form element groups) and determine the optimal number of activated elements(or formed groups),based on the channel correlation information only;for Scheme 3,we consider a semi-definite programming-based approach in the literature,and propose an alternative dominant eigenvector-based method for determining the RIS phase shifts vector.Via extensive simulations,we compare the achievable ergodic rates of these schemes versus the signal-to-noise ratio,the channel correlation level,and the element number-to-coherent time ratio,respectively,and discuss possible switching of the three schemes over these system parameters.At last,operation regions of the considered training overhead reduction schemes are shown in the plane characterized by the system parameters,which provides useful guidelines for practical scheme determination.
基金supported by the National Science Foundation of China under Grant 61271186
文摘Sensing coverage is a fundamental design issue in wireless sensor networks(WSNs),while sensor scheduling ensures coverage degree to the monitored event and extends the network lifetime.In this paper,we address k-coverage scheduling problem in dense WSNs,we maintain a connected k-coverage energy efficiently through a novel Hard-Core based Coordinated Scheduling(HCCS),in which hardcore is a thinning process in stochastic geometry that inhibits more than one active sensor covering any area redundantly in a minimum distance. As compared with existing coordinated scheduling,HCCS allows coordination between sensors with little communication overhead.Moreover,due to the traditional sensing models in k-coverage analysis is unsuitable to describe the characteristic of transmit channel in dense WSNs,we propose a novel sensing model integrating Rayleigh Fading and Distribution of Active sensors(RFDA),and derive the coverage measure and k-coverage probability for the monitored event under RFDA. In addition,we analyze the influence factors,i.e. the transmit condition and monitoring degree to the k-coverage probability. Finally,through Monte Carlo simulations,it is shown that the k-coverage probability of HCCS outperforms that of its random scheduling counterpart.
文摘在n-Rayleigh信道下,研究了MRC(Maximal Ratio Combining)合并接收系统的平均码字错误率(ASEP)性能。基于矩生成函数(MGF)的方法,推导了MRC接收系统在n-Rayleigh衰落信道上采用M进制相移键控(MPSK),M进制正交幅度调制(MQAM)和M进制脉冲幅度调制(MPAM)等几种M进制数字调制方式的ASEP的计算式。然后在不同条件下,仿真了系统的ASEP性能,仿真值与理论值相一致,理论分析的正确性得到了证明。分析结果表明:分集支路数和衰弱因子对系统的ASEP性能有重要影响。
文摘A novel kind of multidimension symbol/sequence trellis coded modulation (TCM) based on TCM of lower coding rate has been constructed. The redundancy of this new kind of TCM is provided not only by the modulated symbol sequence but also by the PN sequences for spreading spectrum as well. The performance of direct sequence spread spectrum multiple access (DS/SSMA) system with this symbol/sequence TCM over flat Rayleigh fading channel has been investigated by theoretical analysis and numerical simulation. The results obtained in this research demonstrate the performance improvements of this system in comparison with that of the DS/SSMA system with conventional TCM under the same conditions.
