Time-varying frequency selective attenuation and colored noises are unfavorable characteristics of power line communication(PLC) channels of the low voltage networks.To overcome these disadvantages,a novel real-time d...Time-varying frequency selective attenuation and colored noises are unfavorable characteristics of power line communication(PLC) channels of the low voltage networks.To overcome these disadvantages,a novel real-time dynamic spectrum management(DSM) algorithm in orthogonal frequency division multiplexing(OFDM)-based high-speed narrow-band power line communication(HNPLC) systems is proposed,and the corresponding FPGA circuit is designed and realized.Performance of the proposed DSM is validated with a large amount of network experiments under practical PLC circumstance.As the noise in each narrow subcarrier is approximately Gaussian,the proposed DSM adopts the BER/SER expression formulized via the AWGN channel to provide a handy and universal strategy for power allocation.The real-time requirement is guaranteed by choosing subcarriers in group and employing the same modulation scheme within each transmission.These measures are suitable for any modulation scheme no matter the system criterion is to maximize data rate or minimize power/BER.Algorithm design and hardware implementation of the proposed DSM are given with some flexible and efficient conversions.The DSM circuit is carried out with Xilinx KC705.Simulation and practical experiments validate that the proposed real-time DSM significantly improves system performance.展开更多
为研究多中继协作正交频分复用(orthogonal frequency division multiplexing,OFDM)系统子载波分配,提出了萤火虫算法与混合蛙跳算法相结合的联合优化算法(GSO-SFLA)来搜索最优子载波对。在总功率约束条件下,以最大化信息传输速率为优...为研究多中继协作正交频分复用(orthogonal frequency division multiplexing,OFDM)系统子载波分配,提出了萤火虫算法与混合蛙跳算法相结合的联合优化算法(GSO-SFLA)来搜索最优子载波对。在总功率约束条件下,以最大化信息传输速率为优化目标,提出了子载波分配模型,给出了基于GSO-SFLA算法的子载波分配步骤,并仿真验证了所提出的子载波分配方案。仿真结果表明,与固定子载波算法和传统的萤火虫算法相比,所提出的基于GSO-SFLA子载波分配方案能获得较大的信息传输速率。展开更多
Efficient and reliable subcarrier power joint allocation is served as a promising problem in cognitive OFDM-based Cognitive Radio Networks (CRN). This paper focuses on optimal subcarrier allocation for OFDM-based CRN....Efficient and reliable subcarrier power joint allocation is served as a promising problem in cognitive OFDM-based Cognitive Radio Networks (CRN). This paper focuses on optimal subcarrier allocation for OFDM-based CRN. We mainly propose subcarrier allocation scheme denoted as Worst Subcarrier Avoiding Water-filling (WSAW), which is based on Rate Adaptive (RA) criterion and three constraints are considered in CRN. The algorithm divides the assignment procedure into two phases. The first phase is an initial subcarrier allocation based on the idea of avoiding selecting the worst subcarrier in order to maximize the transmission rate; while the second phase is an iterative adjustment process which is realized by swapping pairs of subcarriers between arbitrary users. The proposed scheme could assign subcarriers in accordance with channel coherence time. Hence, real time subcarrier allocation could be implemented. Simulation results show that, comparing with the similar existing algorithms, the proposed scheme could achieve larger capacity and a near-optimal BER performance.展开更多
基于相干检测的正交频分复用技术是未来高速光通信技术的重要解决方案之一,由于相干光检测系统结构复杂不易实现,因此采用副载波外差检测技术检测副载波正交频分复用光信号。建立了大气湍流信道系统传输模型,推导了子载波平均载噪比(CNR...基于相干检测的正交频分复用技术是未来高速光通信技术的重要解决方案之一,由于相干光检测系统结构复杂不易实现,因此采用副载波外差检测技术检测副载波正交频分复用光信号。建立了大气湍流信道系统传输模型,推导了子载波平均载噪比(CNR)和平均误比特率(BER)的闭合表达式,数值分析了本振光功率和调制系数对系统平均误比特率的影响,并通过仿真实验进行验证。实验结果表明,与直接检测相比,副载波外差可以进一步提高平均载噪比,提升系统误码性能。当接收光功率为微瓦量级时,本振光功率约为-11 d Bm,此时可获得最佳平均载噪比,当本振光功率大于-11 d Bm时,随本振光功率增加平均载噪比逐渐降低,平均误比特率升高。弱湍流条件下,当接收光功率大于-17 d Bm时,平均误比特率为10-5以上,此时可以保证无线光通信系统的可靠性。展开更多
An expendable conductivity-temperature-depth profiler(XCTD)is one of the most important instruments used to obtain hydrological data,such as temperature and conductivity,and detect ocean depth in a large area.However,...An expendable conductivity-temperature-depth profiler(XCTD)is one of the most important instruments used to obtain hydrological data,such as temperature and conductivity,and detect ocean depth in a large area.However,the XCTD channel provides poor time-varying performance,narrowband,and low signal-to-noise ratio(SNR),which severely restricts the data transmission rate.In contrast to conventional single-carrier modulation techniques,such as amplitude-shift keying and differential phase-shift keying,this article provides a new method,based on orthogonal frequency division multiplexing(OFDM)to enhance the data transmission rate of deep-sea abandoned profilers.We apply the OFDM to enhance the SNR of the XCTD,which is achieved by reducing the data transmission rate of each sub-channel.Moreover,the bandwidth utilization may be improved by increasing the number of subcarriers in a given bandwidth,which enhances the data transmission rate.Based on analysis of the XCTD channel model,OFDM with different parameters such as constellation mapping,number of subcarriers,subcarrier spacing,signal period and cyclic prefix are achieved.To verify the effectiveness of the OFDM,this study investigates the influence of different parameters on the data transmission rate at different noise levels,i.e.,-20 dB and-40 d B.展开更多
基金Supported by the Tsinghua University International Science and Technology Cooperation Project(No.20133000197,20123000148)
文摘Time-varying frequency selective attenuation and colored noises are unfavorable characteristics of power line communication(PLC) channels of the low voltage networks.To overcome these disadvantages,a novel real-time dynamic spectrum management(DSM) algorithm in orthogonal frequency division multiplexing(OFDM)-based high-speed narrow-band power line communication(HNPLC) systems is proposed,and the corresponding FPGA circuit is designed and realized.Performance of the proposed DSM is validated with a large amount of network experiments under practical PLC circumstance.As the noise in each narrow subcarrier is approximately Gaussian,the proposed DSM adopts the BER/SER expression formulized via the AWGN channel to provide a handy and universal strategy for power allocation.The real-time requirement is guaranteed by choosing subcarriers in group and employing the same modulation scheme within each transmission.These measures are suitable for any modulation scheme no matter the system criterion is to maximize data rate or minimize power/BER.Algorithm design and hardware implementation of the proposed DSM are given with some flexible and efficient conversions.The DSM circuit is carried out with Xilinx KC705.Simulation and practical experiments validate that the proposed real-time DSM significantly improves system performance.
文摘为研究多中继协作正交频分复用(orthogonal frequency division multiplexing,OFDM)系统子载波分配,提出了萤火虫算法与混合蛙跳算法相结合的联合优化算法(GSO-SFLA)来搜索最优子载波对。在总功率约束条件下,以最大化信息传输速率为优化目标,提出了子载波分配模型,给出了基于GSO-SFLA算法的子载波分配步骤,并仿真验证了所提出的子载波分配方案。仿真结果表明,与固定子载波算法和传统的萤火虫算法相比,所提出的基于GSO-SFLA子载波分配方案能获得较大的信息传输速率。
基金Supported by the National Natural Science Foundation of China (NSFC) (No. 61102066)the China Postdoctoral Science Foundation (Grant No. 2012M511365)the Scientific Research Project of Zhejiang Provincial Education Department (No. Y201119890)
文摘Efficient and reliable subcarrier power joint allocation is served as a promising problem in cognitive OFDM-based Cognitive Radio Networks (CRN). This paper focuses on optimal subcarrier allocation for OFDM-based CRN. We mainly propose subcarrier allocation scheme denoted as Worst Subcarrier Avoiding Water-filling (WSAW), which is based on Rate Adaptive (RA) criterion and three constraints are considered in CRN. The algorithm divides the assignment procedure into two phases. The first phase is an initial subcarrier allocation based on the idea of avoiding selecting the worst subcarrier in order to maximize the transmission rate; while the second phase is an iterative adjustment process which is realized by swapping pairs of subcarriers between arbitrary users. The proposed scheme could assign subcarriers in accordance with channel coherence time. Hence, real time subcarrier allocation could be implemented. Simulation results show that, comparing with the similar existing algorithms, the proposed scheme could achieve larger capacity and a near-optimal BER performance.
文摘基于相干检测的正交频分复用技术是未来高速光通信技术的重要解决方案之一,由于相干光检测系统结构复杂不易实现,因此采用副载波外差检测技术检测副载波正交频分复用光信号。建立了大气湍流信道系统传输模型,推导了子载波平均载噪比(CNR)和平均误比特率(BER)的闭合表达式,数值分析了本振光功率和调制系数对系统平均误比特率的影响,并通过仿真实验进行验证。实验结果表明,与直接检测相比,副载波外差可以进一步提高平均载噪比,提升系统误码性能。当接收光功率为微瓦量级时,本振光功率约为-11 d Bm,此时可获得最佳平均载噪比,当本振光功率大于-11 d Bm时,随本振光功率增加平均载噪比逐渐降低,平均误比特率升高。弱湍流条件下,当接收光功率大于-17 d Bm时,平均误比特率为10-5以上,此时可以保证无线光通信系统的可靠性。
基金supported by the National Key Research and Development Program of China (No. 2016 YFC1400400)the Marine Economic Innovation and Development Demonstration Project in Binhai New Area (No. 1723434C4114194)
文摘An expendable conductivity-temperature-depth profiler(XCTD)is one of the most important instruments used to obtain hydrological data,such as temperature and conductivity,and detect ocean depth in a large area.However,the XCTD channel provides poor time-varying performance,narrowband,and low signal-to-noise ratio(SNR),which severely restricts the data transmission rate.In contrast to conventional single-carrier modulation techniques,such as amplitude-shift keying and differential phase-shift keying,this article provides a new method,based on orthogonal frequency division multiplexing(OFDM)to enhance the data transmission rate of deep-sea abandoned profilers.We apply the OFDM to enhance the SNR of the XCTD,which is achieved by reducing the data transmission rate of each sub-channel.Moreover,the bandwidth utilization may be improved by increasing the number of subcarriers in a given bandwidth,which enhances the data transmission rate.Based on analysis of the XCTD channel model,OFDM with different parameters such as constellation mapping,number of subcarriers,subcarrier spacing,signal period and cyclic prefix are achieved.To verify the effectiveness of the OFDM,this study investigates the influence of different parameters on the data transmission rate at different noise levels,i.e.,-20 dB and-40 d B.
