Since wireless links in Ad hoc networks are more fragile than those in traditional wireless networks due to route flapping,multi-node cooperation plays an important role in ensuring the quality of service( QoS). Based...Since wireless links in Ad hoc networks are more fragile than those in traditional wireless networks due to route flapping,multi-node cooperation plays an important role in ensuring the quality of service( QoS). Based on the authors' previous work,this paper proposes a receiver-controlled multi-node cooperation routing protocol,known as AODV-RCC. In this protocol,nodes form a cooperation group based on signal power. In a cooperation group,signal power between a partner and a transmitter,as well as signal power between the partner and the receiver,must be larger than the signal power between the transmitter and the receiver. Otherwise,the transmission will not benefit from cooperation. To avoid collision or congestion,each cooperation group only contains one partner. This partner offers both data and ACK cooperative retransmission. Its retransmission time should be shorter than the internal retry time of the transmitter's MAC layer,because it is better for the partner to retransmit firstly,as it offers a more reliable cooperative link. In AODV-RCC,it is the receiver that chooses the partner,because the link between the partner and the receiver is the most important. According to our simulation results,AODV-RCC shortens the end-to-end delay and increases the packet delivery ratio.展开更多
Closed form expressions for the PDF and MGF of the harmonic mean of two independent exponential variates are cited and derived, and then applied to study the performance of cellular multi-node and dual-hop cooperative...Closed form expressions for the PDF and MGF of the harmonic mean of two independent exponential variates are cited and derived, and then applied to study the performance of cellular multi-node and dual-hop cooperative communication systems with non-regenerative relays over flat Rayleigh fading channels. We derive the probability density function (PDF) and asymptotic symbol error rate (SER) expression with MRC scheme. Then we use Matlab to simulate the performance.展开更多
In recent years the variety and complexity of Wireless Sensor Network (WSN) applications, the nodes and the functions they are expected to perform have increased immensely. This poses the question of reducing the ti...In recent years the variety and complexity of Wireless Sensor Network (WSN) applications, the nodes and the functions they are expected to perform have increased immensely. This poses the question of reducing the time from initial design of WSN applications to their implementation as a major research topic. RF communication programs for WSN nodes are generally written on microcontroller units (MCUs) for universal asynchronous receiverransmitter (UART) data communication, however nowadays radio frequency (RF) designs based on field-programmable gate array (FPGA) have emerged as a very powerful alternative, due to their parallel data processing ability and software reconfigurability. In this paper, the authors present a prototype of a flexible multi-node transceiver and monitoring system. The prototype is designed for time-critical applications and can be also reconfigured for other applications like event tracking. The processing power of FPGA is combined with a simple communication protocol. The system consists of three major parts: wireless nodes, the FPGA and display used for visualization of data processing. The transmission protocol is based on preamble and synchronous data transmission, where the receiver adjusts the receiving baud rate in the range from min. 300 to max. 2400 bps. The most important contribution of this work is using the virtual PicoBlaze Soft-Core Processor for controlling the data transmission through the RF modules. The proposed system has been evaluated based on logic utilization, in terms of the number of slice flip flops, the number of 4 input LUTs (Look-Up Tables) and the number of bonded lOBs (Input Output Blocks). The results for capacity usage are very promising as compared to other similar research.展开更多
Traditional landers typically encounter difficulties achieving stable landings because of the weak gravity and complex terrain of small celestial bodies.A multi-node lander with flexible connections can improve the st...Traditional landers typically encounter difficulties achieving stable landings because of the weak gravity and complex terrain of small celestial bodies.A multi-node lander with flexible connections can improve the stability of a small celestial body landing.However,this also poses new challenges,particularly for landing guidance in hazardous terrain.To address this problem,an equivalent simplified dynamic model of a multi-node flexible lander is first constructed,and its flat output is determined.Subsequently,a trajectoryplanning method combining the flow and vector fields is designed to avoid collision,and the parameters of the vector field are optimized online according to the dynamic and obstacle constraints during the descent process to obtain a more suitable trajectory.Finally,the effectiveness of the proposed trajectory-planning method is verified through comparative simulations of landing and obstacle avoidance from the hover point to the landing area.This study offers new prospects for upcoming small celestial body landing missions in complex terrains.展开更多
In view of the obvious changes in color between the upper and lower leaf scar in sugarcane nodes,a method of simultaneous multi-nodes identification on a single sugarcane stem was proposed based on the analysis of gra...In view of the obvious changes in color between the upper and lower leaf scar in sugarcane nodes,a method of simultaneous multi-nodes identification on a single sugarcane stem was proposed based on the analysis of gradient characteristics of sugarcane images.In combination with image processing and machine vision recognition technology,two cameras were used to acquire different parts of sugarcane images,and the two images were integrated into a complete image of sugarcane by image mosaicking.The Sobel operator is used to calculate the gradient of the sugarcane image in a horizontal direction,and the gradient image is obtained.The sugarcane gradient image was scanned by a rectangular template with a width of 14 pixels and a step length of 12 pixels.The features of average gradient and variance gradient were used to identify sugarcane nodes for the first time.The experimental results showed that the recognition accuracy was 96.8952%,and there were fewer false detected sugarcane segments.The detection efficiency could be improved by detecting multi-nodes on a single sugarcane stem at the same time.展开更多
为提升极端灾害情景下城市基础设施网络的安全韧性,针对现有关键节点识别方法存在的异质性刻画不足、识别精度有限等问题,提出1种融合改进中心性与级联影响(fusion of improved centrality and cascading impact,FICCI)的关键节点识别...为提升极端灾害情景下城市基础设施网络的安全韧性,针对现有关键节点识别方法存在的异质性刻画不足、识别精度有限等问题,提出1种融合改进中心性与级联影响(fusion of improved centrality and cascading impact,FICCI)的关键节点识别方法。以深圳市某区交通-电力-通信基础设施为研究对象,构建跨层依赖网络模型,通过改进中心性度量刻画结构异质性与功能耦合度,并引入度量分配法则将中心性度量与负载-容量级联影响值加权融合,获得关键节点排序结果;进一步在多层基础设施网络和3种公共网络上进行验证。结果表明,与传统方法相比,FICCI在级联失效规模、未供电服务损失指数和应急疏散延迟指数等5项指标上整体表现更优;当节点移除百分比达到6%,12%后,在功能退化与结构鲁棒性评估中的优势更为明显;该方法能够支撑基础设施系统脆弱性评估与设防策略优化等实际应用。研究结果可为助力韧性安全城市建设提供参考。展开更多
基金Sponsored by the Natural Scientific Research Innovation Foundation in Harbin Institute of Technology(Grant No.HIT.NSRIF.2013029)the National Science and Technology Major Project(Grant No.2012ZX03004003)+1 种基金the National Basic Research Development Program of China(973 Program)(Grant No.2013CB329003)the National Natural Science Foundation of China(Grant No.61201148 and No.61101123)
摘要Since wireless links in Ad hoc networks are more fragile than those in traditional wireless networks due to route flapping,multi-node cooperation plays an important role in ensuring the quality of service( QoS). Based on the authors' previous work,this paper proposes a receiver-controlled multi-node cooperation routing protocol,known as AODV-RCC. In this protocol,nodes form a cooperation group based on signal power. In a cooperation group,signal power between a partner and a transmitter,as well as signal power between the partner and the receiver,must be larger than the signal power between the transmitter and the receiver. Otherwise,the transmission will not benefit from cooperation. To avoid collision or congestion,each cooperation group only contains one partner. This partner offers both data and ACK cooperative retransmission. Its retransmission time should be shorter than the internal retry time of the transmitter's MAC layer,because it is better for the partner to retransmit firstly,as it offers a more reliable cooperative link. In AODV-RCC,it is the receiver that chooses the partner,because the link between the partner and the receiver is the most important. According to our simulation results,AODV-RCC shortens the end-to-end delay and increases the packet delivery ratio.
摘要Closed form expressions for the PDF and MGF of the harmonic mean of two independent exponential variates are cited and derived, and then applied to study the performance of cellular multi-node and dual-hop cooperative communication systems with non-regenerative relays over flat Rayleigh fading channels. We derive the probability density function (PDF) and asymptotic symbol error rate (SER) expression with MRC scheme. Then we use Matlab to simulate the performance.
摘要In recent years the variety and complexity of Wireless Sensor Network (WSN) applications, the nodes and the functions they are expected to perform have increased immensely. This poses the question of reducing the time from initial design of WSN applications to their implementation as a major research topic. RF communication programs for WSN nodes are generally written on microcontroller units (MCUs) for universal asynchronous receiverransmitter (UART) data communication, however nowadays radio frequency (RF) designs based on field-programmable gate array (FPGA) have emerged as a very powerful alternative, due to their parallel data processing ability and software reconfigurability. In this paper, the authors present a prototype of a flexible multi-node transceiver and monitoring system. The prototype is designed for time-critical applications and can be also reconfigured for other applications like event tracking. The processing power of FPGA is combined with a simple communication protocol. The system consists of three major parts: wireless nodes, the FPGA and display used for visualization of data processing. The transmission protocol is based on preamble and synchronous data transmission, where the receiver adjusts the receiving baud rate in the range from min. 300 to max. 2400 bps. The most important contribution of this work is using the virtual PicoBlaze Soft-Core Processor for controlling the data transmission through the RF modules. The proposed system has been evaluated based on logic utilization, in terms of the number of slice flip flops, the number of 4 input LUTs (Look-Up Tables) and the number of bonded lOBs (Input Output Blocks). The results for capacity usage are very promising as compared to other similar research.
基金the National Key R&D Program(grant number 2019YFA0706500)the National Defense Basic Research Projects(grant number JCKY2021603B030).
摘要Traditional landers typically encounter difficulties achieving stable landings because of the weak gravity and complex terrain of small celestial bodies.A multi-node lander with flexible connections can improve the stability of a small celestial body landing.However,this also poses new challenges,particularly for landing guidance in hazardous terrain.To address this problem,an equivalent simplified dynamic model of a multi-node flexible lander is first constructed,and its flat output is determined.Subsequently,a trajectoryplanning method combining the flow and vector fields is designed to avoid collision,and the parameters of the vector field are optimized online according to the dynamic and obstacle constraints during the descent process to obtain a more suitable trajectory.Finally,the effectiveness of the proposed trajectory-planning method is verified through comparative simulations of landing and obstacle avoidance from the hover point to the landing area.This study offers new prospects for upcoming small celestial body landing missions in complex terrains.
摘要In view of the obvious changes in color between the upper and lower leaf scar in sugarcane nodes,a method of simultaneous multi-nodes identification on a single sugarcane stem was proposed based on the analysis of gradient characteristics of sugarcane images.In combination with image processing and machine vision recognition technology,two cameras were used to acquire different parts of sugarcane images,and the two images were integrated into a complete image of sugarcane by image mosaicking.The Sobel operator is used to calculate the gradient of the sugarcane image in a horizontal direction,and the gradient image is obtained.The sugarcane gradient image was scanned by a rectangular template with a width of 14 pixels and a step length of 12 pixels.The features of average gradient and variance gradient were used to identify sugarcane nodes for the first time.The experimental results showed that the recognition accuracy was 96.8952%,and there were fewer false detected sugarcane segments.The detection efficiency could be improved by detecting multi-nodes on a single sugarcane stem at the same time.
摘要为提升极端灾害情景下城市基础设施网络的安全韧性,针对现有关键节点识别方法存在的异质性刻画不足、识别精度有限等问题,提出1种融合改进中心性与级联影响(fusion of improved centrality and cascading impact,FICCI)的关键节点识别方法。以深圳市某区交通-电力-通信基础设施为研究对象,构建跨层依赖网络模型,通过改进中心性度量刻画结构异质性与功能耦合度,并引入度量分配法则将中心性度量与负载-容量级联影响值加权融合,获得关键节点排序结果;进一步在多层基础设施网络和3种公共网络上进行验证。结果表明,与传统方法相比,FICCI在级联失效规模、未供电服务损失指数和应急疏散延迟指数等5项指标上整体表现更优;当节点移除百分比达到6%,12%后,在功能退化与结构鲁棒性评估中的优势更为明显;该方法能够支撑基础设施系统脆弱性评估与设防策略优化等实际应用。研究结果可为助力韧性安全城市建设提供参考。