索引调制OFDM(OFDM with index modulation,OFDM-IM)的接收端常采用基于子载波激活状态的对数似然比(log likelihood ratio,LLR)检测算法。然而,LLR检测算法会出现子载波激活模式(subcarrier activation pattern,SAP)判决错误或判决出...索引调制OFDM(OFDM with index modulation,OFDM-IM)的接收端常采用基于子载波激活状态的对数似然比(log likelihood ratio,LLR)检测算法。然而,LLR检测算法会出现子载波激活模式(subcarrier activation pattern,SAP)判决错误或判决出非法的SAP,不仅引起对索引信息的估计错误,还严重影响符号解调的正确率,导致整体的误码率增大。针对上述问题,提出了一种基于低密度奇偶校验(low density parity check,LDPC)编码辅助的子载波索引保护方案,通过对索引信息比特编码降低子载波激活模式的判决错误率。在接收端设计了LDPC编码辅助(LDPC coding aided,LA)检测算法,并详细推导了索引信息比特LLR的闭合表达式。利用MATLAB软件在多径衰落信道下进行蒙特卡洛仿真,结果表明在频谱效率不低于传统OFDM-IM方案的条件下,所提方案在误码率为10-4时可取得约5~9 dB的增益,能够有效提高OFDM-IM传输方案的误码率性能。展开更多
研究了Underlay频谱共享方式下两跳认知缓存辅助中继(Buffer-aided Cognitive Relay)索引调制正交频分复用技术(Orthogonal Frequency Division Multiplexing with Index Modulation,OFDM-IM)的中断性能。提出了一种受过时信道状态信息(...研究了Underlay频谱共享方式下两跳认知缓存辅助中继(Buffer-aided Cognitive Relay)索引调制正交频分复用技术(Orthogonal Frequency Division Multiplexing with Index Modulation,OFDM-IM)的中断性能。提出了一种受过时信道状态信息(Channel State Information,CSI)影响的“最大可用缓存中继/最大接收信噪比之和子载波组(Max Available Buffer Relay/Max Sum of Received Signal-to-Noise Ratio Subcarriers,MABR/MSRS)”的联合选择方案。采用译码转发(Decode and Forward,DF)中继协议,基于马尔科夫链(Markov Chain,MC)理论对中继缓存状态变化情况进行建模,推导了MABR/MSRS方案可达中断概率的闭式解,理论分析与蒙特卡罗仿真数值吻合良好。仿真结果表明,相同条件下MABR/MSRS方案获得了比无缓存的Bulk中继选择方案更好的系统中断性能;过时CSI会恶化系统传输性能;当主用户干扰门限值一定时,随着SNR的增加,系统中断概率会收敛至一个固定的值。展开更多
基于带指数调制的OFDM系统(Orthogonal Frequency Division Multiplexing with Index Modulation,OFDM-IM)以其潜在的分集增益而被人们所熟知。随后,一种基于遗传算法的全索引调制的OFDM(GA-OFDM-AIM)方案被提出,与传统的OFDM-IM相比,...基于带指数调制的OFDM系统(Orthogonal Frequency Division Multiplexing with Index Modulation,OFDM-IM)以其潜在的分集增益而被人们所熟知。随后,一种基于遗传算法的全索引调制的OFDM(GA-OFDM-AIM)方案被提出,与传统的OFDM-IM相比,其采用遗传算法辅助子块设计,通过交叉、变异和选择过程,得到了低误码率的子块实现,但由于窃听者可以通过搜索算法或检测信道中的子块,传输安全无法得到保证,为此提出了基于遗传算法的全索引调制的物理层加密算法。利用无线信道特点,采用密钥生成技术提取初始密钥并且作为混沌发生器的初始值产生混沌序列,再利用该混沌序列对GA-OFDM-AIM中的子块进行星座点映射和星座旋转,打乱了星座阶数和调制类型的特征,使得窃听者难以破解系统的参数。为验证该算法的有效性和安全性,分析了不同的攻击模型,并比较了加密前后星座的误码性能。安全分析和仿真结果表明,该方案能有效地提高系统的安全性和传输性能。展开更多
recently the indexed modulation(IM) technique in conjunction with the multi-carrier modulation gains an increasing attention. It conveys additional information on the subcarrier indices by activating specific subcarri...recently the indexed modulation(IM) technique in conjunction with the multi-carrier modulation gains an increasing attention. It conveys additional information on the subcarrier indices by activating specific subcarriers in the frequency domain besides the conventional amplitude-phase modulation of the activated subcarriers. Orthogonal frequency division multiplexing(OFDM) with IM(OFDM-IM) is deeply compared with the classical OFDM. It leads to an attractive trade-off between the spectral efficiency(SE) and the energy efficiency(EE). In this paper, the concept of the combinatorial modulation is introduced from a new point of view. The sparsity mapping is suggested intentionally to enable the compressive sensing(CS) concept in the data recovery process to provide further performance and EE enhancement without SE loss. Generating artificial data sparsity in the frequency domain along with naturally embedded channel sparsity in the time domain allows joint data recovery and channel estimation in a double sparsity framework. Based on simulation results, the performance of the proposed approach agrees with the predicted CS superiority even under low signal-to-noise ratio without channel coding. Moreover, the proposed sparsely indexed modulation system outperforms the conventional OFDM system and the OFDM-IM system in terms of error performance, peak-to-average power ratio(PAPR) and energy efficiency under the same spectral efficiency.展开更多
研究了两跳缓存辅助(Buffer-aided)多中继索引调制OFDM(Orthogonal Frequency Division Multiplexing with Index Modulation,OFDM-IM)的中断性能,并提出了一种名为“最大可用缓存/最大接收信噪比之和(Max Available Buffer/Max Sum of ...研究了两跳缓存辅助(Buffer-aided)多中继索引调制OFDM(Orthogonal Frequency Division Multiplexing with Index Modulation,OFDM-IM)的中断性能,并提出了一种名为“最大可用缓存/最大接收信噪比之和(Max Available Buffer/Max Sum of Received Signal-to-Noise Ratio,MAB/MSR)”的中继/子载波组联合选择方案。采用译码转发(Decode and Forward,DF)中继协议,运用马尔科夫链(Markov Chain,MC)理论分析了中继的缓存空间状态变化情况,推导了MAB/MSR方案可达中断概率的闭式解,理论分析与蒙特卡罗仿真数值吻合良好。结果表明,MAB/MSR方案获得了比缓存辅助最大链路选择(Max Link Selection,MLS)、最大权重中继选择(Max Weight Relay Selection,MWRS)方案更好的系统中断性能。展开更多
Modulation techniques for light fidelity （Li-Fi） are reviewed in this paper. Li-Fi is the fully networked solution for nmltiple users that combines communication and illumination simultaneously. Light emitting diod...Modulation techniques for light fidelity （Li-Fi） are reviewed in this paper. Li-Fi is the fully networked solution for nmltiple users that combines communication and illumination simultaneously. Light emitting diodes （LEDs） are used in Li-Fi as visible light transmitters, therefore, only intensity modulated direct detected modulation techniques can be achieved. Single carrier modulation techniques are straightforward to be used in Li-Fi, however, computationally complex equalization processes are required in fre- quency selective Li-Fi channels. On the other hand, multiearrier modulation techniques offer a viable solution for Li-Fi in terms of power, spectral and computational efficiency. In particular, orthogonal frequency division multiplexing （OFDM） based modulation techniques offer a practical solution for Li-Fi, especially when direct current （DC） wander, and adaptive bit and power loading techniques are considered. Li-Fi modulation techniques need to also satisfy illumination requirements. Flickering avoidance and dimming control are considered in the variant modulation techniques presented. This paper surveys the suitable modulation techniques for Li-Fi including those which explore time, frequency and colour domains.展开更多
空间调制(Spatial Modulation, SM)技术和OFDM多模子载波索引调制(OFDMMulti-Mode Index Modulation, MM-OFDM-IM)技术分别在能量效率(Energy Efficiency,EE)和频谱效率(Spectral Efficiency,SE)上有着很大的优势。多维度索引调制技术...空间调制(Spatial Modulation, SM)技术和OFDM多模子载波索引调制(OFDMMulti-Mode Index Modulation, MM-OFDM-IM)技术分别在能量效率(Energy Efficiency,EE)和频谱效率(Spectral Efficiency,SE)上有着很大的优势。多维度索引调制技术相结合能够应用多种物理资源,应对无线通信系统对数据传输和系统容量的高需求,由此将SM与MMOFDM-IM系统灵活结合,构建基于空频结合的多模复合索引调制(OFDM-Multiple-Mode Space Frequency Composite Index Modulation,MM-OFDM-SFCIM)系统,保留传统子载波索引调制技术中的静默子载波,拓展新的复合系数维度,提高系统的SE和EE。针对系统的复杂特性,提出了基于符号能量及对数似然的联合检测算法(REML based on symbolic Energy and LLR,EL-REML)。仿真结果表明,MM-OFDM-SFCIM系统比传统的空频结合系统在SE上提高了约30%,并且MM-DFDM-SPCIM系统中提出的EL-REML算法比LLR算法在误码率上提高了3~4 dB,相比传统的ML算法,其计算复杂度更低。展开更多
多输入多输出(Multiple-input multiple-output,MIMO)技术可以有效提高水禽监控网络节点间的数据传输速率和误比特性能.载波序号调制技术(Orthogonal frequency division multiplexing with index modulation,OFDM-IM)是一种可以有效对...多输入多输出(Multiple-input multiple-output,MIMO)技术可以有效提高水禽监控网络节点间的数据传输速率和误比特性能.载波序号调制技术(Orthogonal frequency division multiplexing with index modulation,OFDM-IM)是一种可以有效对抗由多径传输引起的频率选择性衰落并获得更优的频谱效率和误比特性能多载波传输新技术.通过将MIMO和载波序号调制技术相结合可以提高水禽监控网络节点间的数据传输速率和可靠性,提出一种基于树形搜索的序贯蒙特卡罗(Sequential Monte Carlo,SMC)低复杂度接收机,通过对每个子载波抽取采样点,可以大幅降低接收机的计算法复杂度.仿真结果表明提出的SMC接收机可以在线性计算复杂度下获得接近最优的最大似然(Maximum Likelihood,ML)概率的接收机的误比特性能.展开更多
文摘索引调制OFDM(OFDM with index modulation,OFDM-IM)的接收端常采用基于子载波激活状态的对数似然比(log likelihood ratio,LLR)检测算法。然而,LLR检测算法会出现子载波激活模式(subcarrier activation pattern,SAP)判决错误或判决出非法的SAP,不仅引起对索引信息的估计错误,还严重影响符号解调的正确率,导致整体的误码率增大。针对上述问题,提出了一种基于低密度奇偶校验(low density parity check,LDPC)编码辅助的子载波索引保护方案,通过对索引信息比特编码降低子载波激活模式的判决错误率。在接收端设计了LDPC编码辅助(LDPC coding aided,LA)检测算法,并详细推导了索引信息比特LLR的闭合表达式。利用MATLAB软件在多径衰落信道下进行蒙特卡洛仿真,结果表明在频谱效率不低于传统OFDM-IM方案的条件下,所提方案在误码率为10-4时可取得约5~9 dB的增益,能够有效提高OFDM-IM传输方案的误码率性能。
文摘研究了Underlay频谱共享方式下两跳认知缓存辅助中继(Buffer-aided Cognitive Relay)索引调制正交频分复用技术(Orthogonal Frequency Division Multiplexing with Index Modulation,OFDM-IM)的中断性能。提出了一种受过时信道状态信息(Channel State Information,CSI)影响的“最大可用缓存中继/最大接收信噪比之和子载波组(Max Available Buffer Relay/Max Sum of Received Signal-to-Noise Ratio Subcarriers,MABR/MSRS)”的联合选择方案。采用译码转发(Decode and Forward,DF)中继协议,基于马尔科夫链(Markov Chain,MC)理论对中继缓存状态变化情况进行建模,推导了MABR/MSRS方案可达中断概率的闭式解,理论分析与蒙特卡罗仿真数值吻合良好。仿真结果表明,相同条件下MABR/MSRS方案获得了比无缓存的Bulk中继选择方案更好的系统中断性能;过时CSI会恶化系统传输性能;当主用户干扰门限值一定时,随着SNR的增加,系统中断概率会收敛至一个固定的值。
文摘基于带指数调制的OFDM系统(Orthogonal Frequency Division Multiplexing with Index Modulation,OFDM-IM)以其潜在的分集增益而被人们所熟知。随后,一种基于遗传算法的全索引调制的OFDM(GA-OFDM-AIM)方案被提出,与传统的OFDM-IM相比,其采用遗传算法辅助子块设计,通过交叉、变异和选择过程,得到了低误码率的子块实现,但由于窃听者可以通过搜索算法或检测信道中的子块,传输安全无法得到保证,为此提出了基于遗传算法的全索引调制的物理层加密算法。利用无线信道特点,采用密钥生成技术提取初始密钥并且作为混沌发生器的初始值产生混沌序列,再利用该混沌序列对GA-OFDM-AIM中的子块进行星座点映射和星座旋转,打乱了星座阶数和调制类型的特征,使得窃听者难以破解系统的参数。为验证该算法的有效性和安全性,分析了不同的攻击模型,并比较了加密前后星座的误码性能。安全分析和仿真结果表明,该方案能有效地提高系统的安全性和传输性能。
文摘recently the indexed modulation(IM) technique in conjunction with the multi-carrier modulation gains an increasing attention. It conveys additional information on the subcarrier indices by activating specific subcarriers in the frequency domain besides the conventional amplitude-phase modulation of the activated subcarriers. Orthogonal frequency division multiplexing(OFDM) with IM(OFDM-IM) is deeply compared with the classical OFDM. It leads to an attractive trade-off between the spectral efficiency(SE) and the energy efficiency(EE). In this paper, the concept of the combinatorial modulation is introduced from a new point of view. The sparsity mapping is suggested intentionally to enable the compressive sensing(CS) concept in the data recovery process to provide further performance and EE enhancement without SE loss. Generating artificial data sparsity in the frequency domain along with naturally embedded channel sparsity in the time domain allows joint data recovery and channel estimation in a double sparsity framework. Based on simulation results, the performance of the proposed approach agrees with the predicted CS superiority even under low signal-to-noise ratio without channel coding. Moreover, the proposed sparsely indexed modulation system outperforms the conventional OFDM system and the OFDM-IM system in terms of error performance, peak-to-average power ratio(PAPR) and energy efficiency under the same spectral efficiency.
文摘研究了两跳缓存辅助(Buffer-aided)多中继索引调制OFDM(Orthogonal Frequency Division Multiplexing with Index Modulation,OFDM-IM)的中断性能,并提出了一种名为“最大可用缓存/最大接收信噪比之和(Max Available Buffer/Max Sum of Received Signal-to-Noise Ratio,MAB/MSR)”的中继/子载波组联合选择方案。采用译码转发(Decode and Forward,DF)中继协议,运用马尔科夫链(Markov Chain,MC)理论分析了中继的缓存空间状态变化情况,推导了MAB/MSR方案可达中断概率的闭式解,理论分析与蒙特卡罗仿真数值吻合良好。结果表明,MAB/MSR方案获得了比缓存辅助最大链路选择(Max Link Selection,MLS)、最大权重中继选择(Max Weight Relay Selection,MWRS)方案更好的系统中断性能。
基金support by the UK Engineering and Physical Sciences Research Council(EPSRC)under Grants EP/K008757/1 and EP/M506515/1
文摘Modulation techniques for light fidelity （Li-Fi） are reviewed in this paper. Li-Fi is the fully networked solution for nmltiple users that combines communication and illumination simultaneously. Light emitting diodes （LEDs） are used in Li-Fi as visible light transmitters, therefore, only intensity modulated direct detected modulation techniques can be achieved. Single carrier modulation techniques are straightforward to be used in Li-Fi, however, computationally complex equalization processes are required in fre- quency selective Li-Fi channels. On the other hand, multiearrier modulation techniques offer a viable solution for Li-Fi in terms of power, spectral and computational efficiency. In particular, orthogonal frequency division multiplexing （OFDM） based modulation techniques offer a practical solution for Li-Fi, especially when direct current （DC） wander, and adaptive bit and power loading techniques are considered. Li-Fi modulation techniques need to also satisfy illumination requirements. Flickering avoidance and dimming control are considered in the variant modulation techniques presented. This paper surveys the suitable modulation techniques for Li-Fi including those which explore time, frequency and colour domains.
文摘空间调制(Spatial Modulation, SM)技术和OFDM多模子载波索引调制(OFDMMulti-Mode Index Modulation, MM-OFDM-IM)技术分别在能量效率(Energy Efficiency,EE)和频谱效率(Spectral Efficiency,SE)上有着很大的优势。多维度索引调制技术相结合能够应用多种物理资源,应对无线通信系统对数据传输和系统容量的高需求,由此将SM与MMOFDM-IM系统灵活结合,构建基于空频结合的多模复合索引调制(OFDM-Multiple-Mode Space Frequency Composite Index Modulation,MM-OFDM-SFCIM)系统,保留传统子载波索引调制技术中的静默子载波,拓展新的复合系数维度,提高系统的SE和EE。针对系统的复杂特性,提出了基于符号能量及对数似然的联合检测算法(REML based on symbolic Energy and LLR,EL-REML)。仿真结果表明,MM-OFDM-SFCIM系统比传统的空频结合系统在SE上提高了约30%,并且MM-DFDM-SPCIM系统中提出的EL-REML算法比LLR算法在误码率上提高了3~4 dB,相比传统的ML算法,其计算复杂度更低。
文摘多输入多输出(Multiple-input multiple-output,MIMO)技术可以有效提高水禽监控网络节点间的数据传输速率和误比特性能.载波序号调制技术(Orthogonal frequency division multiplexing with index modulation,OFDM-IM)是一种可以有效对抗由多径传输引起的频率选择性衰落并获得更优的频谱效率和误比特性能多载波传输新技术.通过将MIMO和载波序号调制技术相结合可以提高水禽监控网络节点间的数据传输速率和可靠性,提出一种基于树形搜索的序贯蒙特卡罗(Sequential Monte Carlo,SMC)低复杂度接收机,通过对每个子载波抽取采样点,可以大幅降低接收机的计算法复杂度.仿真结果表明提出的SMC接收机可以在线性计算复杂度下获得接近最优的最大似然(Maximum Likelihood,ML)概率的接收机的误比特性能.
