A novel multi-layer planar antenna array to achieve multi-polarized radiation is developed. U-shaped coupling slots are embedded in the ground plane to extend the bandwidth. The phase relation between adjacent element...A novel multi-layer planar antenna array to achieve multi-polarized radiation is developed. U-shaped coupling slots are embedded in the ground plane to extend the bandwidth. The phase relation between adjacent elements in the radiation field is analyzed when adjacent elements are fed in opposite phase. Return loss and radiation pattern are measured for a 16-element antenna array at 12.5 GHz. The radiation pattern shows a good agreement with the calculated one in the shape of the main beam. The return-loss of the proposed antenna array is less than -20 dB in the 12.5 GHz frequency band （12.25-12.75 GHz）. Because of two feed ports the antenna can transmit arbitrary elliptic polarized waves if the two feed ports have different amplitude and phase. The main factors such as element spacing, substrate medium and manufacturing imperfection are analyzed and the corresponding conclusions are presented.展开更多
Conventional slot microstrip antenna is analyzed,an h-shaped multi-frequency and miniaturization slot microstrip antenna is proposed.Numerical simulation is performed for the characteristics of the antenna with the so...Conventional slot microstrip antenna is analyzed,an h-shaped multi-frequency and miniaturization slot microstrip antenna is proposed.Numerical simulation is performed for the characteristics of the antenna with the software HFSS11.0,which is a kind of simulation software based on Finite Element Method,the simulation results shown that the antenna operated at 2.26~2.42GHz,2.67~2.82GHz,4.28~4.39GHz and 5.76~5.89GHz when the return loss S11<-10dB,the size reduced compare to general microstrip antenna,demonstrated the effectiveness of the design scheme.The antenna structure is simple and easily to be implemented,met the wireless LAN 802.11a/b/g/n mobile terminal antenna miniaturization and multi-band requirements.展开更多
针对现有的双局域网(LAN)太赫兹无线局域网(Dual-LAN THz WLAN)相关介质访问控制(MAC)协议中存在的某些节点会在多个超帧内重复发送相同的信道时隙请求帧以申请时隙资源以及网络运行的一些时段存在空闲时隙等问题,提出一种基于自发数据...针对现有的双局域网(LAN)太赫兹无线局域网(Dual-LAN THz WLAN)相关介质访问控制(MAC)协议中存在的某些节点会在多个超帧内重复发送相同的信道时隙请求帧以申请时隙资源以及网络运行的一些时段存在空闲时隙等问题,提出一种基于自发数据传输的高效MAC协议——SDTE-MAC(high-Efficiency MAC protocol based on Spontaneous Data Transmission)。SDTE-MAC通过让各节点都维护一张或多张时间单元链表,使各节点与其余节点在网络运行时间上达到同步,从而获悉各节点应该在信道空闲时隙的什么位置开始发送数据帧,优化了传统的信道时隙分配和信道剩余时隙再分配的流程,提高了网络吞吐量和信道时隙利用率,降低了数据时延,能够进一步提升双LAN太赫兹无线局域网的性能。仿真结果表明,网络饱和时,相较于AHT-MAC(Adaptive High Throughout multi-pan MAC protocol)中的N-CTAP(Normal Channel Time Allocation Period)时段时隙资源分配新机制以及自适应缩短超帧时段机制,SDTE-MAC的MAC层吞吐量提升了9.2%,信道时隙利用率提升了10.9%,数据时延降低了22.2%。展开更多
随着预训练语言模型在自然语言处理(NLP)任务上的应用,意图检测(ID)和槽位填充(SF)联合建模提高了口语理解的性能。现有方法大多关注意图和槽位的相互作用,忽略了差异文本序列建模对口语理解(SLU)任务的影响。因此,提出一种基于多任务...随着预训练语言模型在自然语言处理(NLP)任务上的应用,意图检测(ID)和槽位填充(SF)联合建模提高了口语理解的性能。现有方法大多关注意图和槽位的相互作用,忽略了差异文本序列建模对口语理解(SLU)任务的影响。因此,提出一种基于多任务学习的意图检测和槽位填充联合方法(IDSFML)。首先,使用随机掩盖mask策略构造差异文本,设计结合自编码器和注意力机制的神经网络(AEA)结构,为口语理解任务融入差异文本序列的特征;其次,设计相似性分布任务,使差异文本和原始文本的表征相似;最后,联合训练ID、SF和差异文本序列相似性分布三个任务。在航班旅行信息系统(ATIS)和SNIPS数据集上的实验结果表明,IDSFML与表现次优的基线方法SASGBC(Self-Attention and Slot-Gated on top of BERT with CRF)相比,槽位填充F1值分别提升了1.9和1.6个百分点,意图检测准确率分别提升了0.2和0.4个百分点,提高了口语理解任务的准确率。展开更多
In Ambient Assistant Living(AAL) systems, it is a fundamental problem to ensure prompt delivery of detected events, such as irregular heart rate or fall of elderly, to a central processing device(e.g. gateway node). M...In Ambient Assistant Living(AAL) systems, it is a fundamental problem to ensure prompt delivery of detected events, such as irregular heart rate or fall of elderly, to a central processing device(e.g. gateway node). Most of recently proposed MAC protocols for low-power embedded sensing systems(e.g. wireless sensor networks) are designed with energy efficiency as the first goal, so they are not suitable for AAL systems. Although some multi-channel MAC protocols have been proposed to address the problem, most of those protocols ignore the cost of channel switching, which can have reverse effect on network performance, especially latency of data delivery. In this paper, we propose a Delay-Sensitive Multi-channel MAC protocol(DS-MMAC) for AAL systems, which can provide high packet delivery ratio and bound low latency for data delivered to the gateway node. The novelty of the protocol is that an efficient distributed time slot scheduling and channel assignment algorithm is combined with the process of route establishment, which takes the channel switching cost into account and reduces endto-end delay to meet the required delay bound of each data flow. The performance of the proposed protocol is evaluated through extensive simulations. Results show that DS-MMAC can bound low latency for delivering detected events in AAL system to the gateway, while providing high delivery reliability and low energy consumption.展开更多
Fractal antennas are characterized by space filling and self-similarity properties which results in considerable size reduction and multiband operation as compared to conventional microstrip antenna. This paper outlin...Fractal antennas are characterized by space filling and self-similarity properties which results in considerable size reduction and multiband operation as compared to conventional microstrip antenna. This paper outlines a multiband antenna design based on fractal concepts. Fractal antennas show multiband behavior due to self-similarity in their structure. The plus shaped fractal antenna has been designed on a substrate of dielectric constant €r = 4.4 and thickness 1.6mm. The proposed antenna is characterized by a compact size and it is microstrip feed fractal patch of order 1/3. It is observed that the antenna is radiating at multiple resonant frequencies. The resonant frequency is reduced from 2.2 GHz to 900 MHz after I & II iterations respectively. Thus considerable size reduction of 81.77% & overall bandwidth of 12.92% are achieved. The proposed antenna is simulated using the method of moment based commercial software (IE3D) and it is found that simulated results are in good agreement with the experimental results.展开更多
文摘A novel multi-layer planar antenna array to achieve multi-polarized radiation is developed. U-shaped coupling slots are embedded in the ground plane to extend the bandwidth. The phase relation between adjacent elements in the radiation field is analyzed when adjacent elements are fed in opposite phase. Return loss and radiation pattern are measured for a 16-element antenna array at 12.5 GHz. The radiation pattern shows a good agreement with the calculated one in the shape of the main beam. The return-loss of the proposed antenna array is less than -20 dB in the 12.5 GHz frequency band （12.25-12.75 GHz）. Because of two feed ports the antenna can transmit arbitrary elliptic polarized waves if the two feed ports have different amplitude and phase. The main factors such as element spacing, substrate medium and manufacturing imperfection are analyzed and the corresponding conclusions are presented.
基金supported by the Science Technology of The Chongqing Education Commission(KJ100512)the Natural Science Foundation of Chongqing province of China(CSTC 2010BB2412)
文摘Conventional slot microstrip antenna is analyzed,an h-shaped multi-frequency and miniaturization slot microstrip antenna is proposed.Numerical simulation is performed for the characteristics of the antenna with the software HFSS11.0,which is a kind of simulation software based on Finite Element Method,the simulation results shown that the antenna operated at 2.26~2.42GHz,2.67~2.82GHz,4.28~4.39GHz and 5.76~5.89GHz when the return loss S11<-10dB,the size reduced compare to general microstrip antenna,demonstrated the effectiveness of the design scheme.The antenna structure is simple and easily to be implemented,met the wireless LAN 802.11a/b/g/n mobile terminal antenna miniaturization and multi-band requirements.
文摘针对现有的双局域网(LAN)太赫兹无线局域网(Dual-LAN THz WLAN)相关介质访问控制(MAC)协议中存在的某些节点会在多个超帧内重复发送相同的信道时隙请求帧以申请时隙资源以及网络运行的一些时段存在空闲时隙等问题,提出一种基于自发数据传输的高效MAC协议——SDTE-MAC(high-Efficiency MAC protocol based on Spontaneous Data Transmission)。SDTE-MAC通过让各节点都维护一张或多张时间单元链表,使各节点与其余节点在网络运行时间上达到同步,从而获悉各节点应该在信道空闲时隙的什么位置开始发送数据帧,优化了传统的信道时隙分配和信道剩余时隙再分配的流程,提高了网络吞吐量和信道时隙利用率,降低了数据时延,能够进一步提升双LAN太赫兹无线局域网的性能。仿真结果表明,网络饱和时,相较于AHT-MAC(Adaptive High Throughout multi-pan MAC protocol)中的N-CTAP(Normal Channel Time Allocation Period)时段时隙资源分配新机制以及自适应缩短超帧时段机制,SDTE-MAC的MAC层吞吐量提升了9.2%,信道时隙利用率提升了10.9%,数据时延降低了22.2%。
文摘随着预训练语言模型在自然语言处理(NLP)任务上的应用,意图检测(ID)和槽位填充(SF)联合建模提高了口语理解的性能。现有方法大多关注意图和槽位的相互作用,忽略了差异文本序列建模对口语理解(SLU)任务的影响。因此,提出一种基于多任务学习的意图检测和槽位填充联合方法(IDSFML)。首先,使用随机掩盖mask策略构造差异文本,设计结合自编码器和注意力机制的神经网络(AEA)结构,为口语理解任务融入差异文本序列的特征;其次,设计相似性分布任务,使差异文本和原始文本的表征相似;最后,联合训练ID、SF和差异文本序列相似性分布三个任务。在航班旅行信息系统(ATIS)和SNIPS数据集上的实验结果表明,IDSFML与表现次优的基线方法SASGBC(Self-Attention and Slot-Gated on top of BERT with CRF)相比,槽位填充F1值分别提升了1.9和1.6个百分点,意图检测准确率分别提升了0.2和0.4个百分点,提高了口语理解任务的准确率。
基金supported by the International S&T Cooperation Program of China (ISTCP) under Grant No. 2013DFA10690the National Science Foundation of China (NSFC) under Grant No. 61100180
文摘In Ambient Assistant Living(AAL) systems, it is a fundamental problem to ensure prompt delivery of detected events, such as irregular heart rate or fall of elderly, to a central processing device(e.g. gateway node). Most of recently proposed MAC protocols for low-power embedded sensing systems(e.g. wireless sensor networks) are designed with energy efficiency as the first goal, so they are not suitable for AAL systems. Although some multi-channel MAC protocols have been proposed to address the problem, most of those protocols ignore the cost of channel switching, which can have reverse effect on network performance, especially latency of data delivery. In this paper, we propose a Delay-Sensitive Multi-channel MAC protocol(DS-MMAC) for AAL systems, which can provide high packet delivery ratio and bound low latency for data delivered to the gateway node. The novelty of the protocol is that an efficient distributed time slot scheduling and channel assignment algorithm is combined with the process of route establishment, which takes the channel switching cost into account and reduces endto-end delay to meet the required delay bound of each data flow. The performance of the proposed protocol is evaluated through extensive simulations. Results show that DS-MMAC can bound low latency for delivering detected events in AAL system to the gateway, while providing high delivery reliability and low energy consumption.
文摘Fractal antennas are characterized by space filling and self-similarity properties which results in considerable size reduction and multiband operation as compared to conventional microstrip antenna. This paper outlines a multiband antenna design based on fractal concepts. Fractal antennas show multiband behavior due to self-similarity in their structure. The plus shaped fractal antenna has been designed on a substrate of dielectric constant €r = 4.4 and thickness 1.6mm. The proposed antenna is characterized by a compact size and it is microstrip feed fractal patch of order 1/3. It is observed that the antenna is radiating at multiple resonant frequencies. The resonant frequency is reduced from 2.2 GHz to 900 MHz after I & II iterations respectively. Thus considerable size reduction of 81.77% & overall bandwidth of 12.92% are achieved. The proposed antenna is simulated using the method of moment based commercial software (IE3D) and it is found that simulated results are in good agreement with the experimental results.
