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 receiver/transmitter （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
Unmanned Aerial Vehicle（UAV） is developing towards the direction of High Altitude Long Endurance（HALE）. This will have an important influence on the stability of its airborne electronic equipment using passive the...Unmanned Aerial Vehicle（UAV） is developing towards the direction of High Altitude Long Endurance（HALE）. This will have an important influence on the stability of its airborne electronic equipment using passive thermal management. In this paper, a multi-node transient thermal model for airborne electronic equipment is set up based on the thermal network method to predict their dynamic temperature responses under high altitude and long flight time conditions. Some relevant factors are considered into this temperature prediction model including flight environment,radiation, convection, heat conduction, etc. An experimental chamber simulating a high altitude flight environment was set up to survey the dynamic thermal responses of airborne electronic equipment in a UAV. According to the experimental measurement results, the multi-node transient thermal model is verified without consideration of the effects of flight speed. Then, a modified way about outside flight speed is added into the model to improve the temperature prediction performance. Finally, the corresponding simulation code is developed based on the proposed model. It can realize the dynamic temperature prediction of airborne electronic equipment under HALE conditions.展开更多
Using computer-aided design three-dimensional （3D） simulation technology, the recovery mechanism of single event upset and the effects of spacing and hit angle on the recovery are studied. It is found that the multi...Using computer-aided design three-dimensional （3D） simulation technology, the recovery mechanism of single event upset and the effects of spacing and hit angle on the recovery are studied. It is found that the multi-node charge collection plays a key role in recovery and shielding the charge sharing by adding guard rings. It cannot exhibit the recovery effect. It is also indicated that the upset linear energy transfer （LET） threshold is kept constant while the recovery LET threshold increases as the spacing increases. Additionally, the effect of incident angle on recovery is analysed and it is shown that a larger angle can bring about a stronger charge sharing effect, thus strengthening the recovery ability.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
Using computer-aided design three-dimensional simulation technology,the supply voltage scaled dependency of the recovery of single event upset and charge collection in static random-access memory cells are investigate...Using computer-aided design three-dimensional simulation technology,the supply voltage scaled dependency of the recovery of single event upset and charge collection in static random-access memory cells are investigated.It reveals that the recovery linear energy transfer threshold decreases with the supply voltage reducing,which is quite attractive for dynamic voltage scaling and subthreshold circuit radiation-hardened design.Additionally,the effect of supply voltage on charge collection is also investigated.It is concluded that the supply voltage mainly affects the bipolar gain of the parasitical bipolar junction transistor（BJT） and the existence of the source plays an important role in supply voltage variation.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)
文摘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.
文摘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.
文摘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 receiver/transmitter （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).
文摘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.
基金the financial support of National Key R&D Program of China (No.2017YFB1201100)
文摘Unmanned Aerial Vehicle（UAV） is developing towards the direction of High Altitude Long Endurance（HALE）. This will have an important influence on the stability of its airborne electronic equipment using passive thermal management. In this paper, a multi-node transient thermal model for airborne electronic equipment is set up based on the thermal network method to predict their dynamic temperature responses under high altitude and long flight time conditions. Some relevant factors are considered into this temperature prediction model including flight environment,radiation, convection, heat conduction, etc. An experimental chamber simulating a high altitude flight environment was set up to survey the dynamic thermal responses of airborne electronic equipment in a UAV. According to the experimental measurement results, the multi-node transient thermal model is verified without consideration of the effects of flight speed. Then, a modified way about outside flight speed is added into the model to improve the temperature prediction performance. Finally, the corresponding simulation code is developed based on the proposed model. It can realize the dynamic temperature prediction of airborne electronic equipment under HALE conditions.
基金supported by the State Key Program of the National Natural Science Foundation of China (Grant No.60836004)the National Natural Science Foundation of China (Grant Nos.61076025 and 61006070)
文摘Using computer-aided design three-dimensional （3D） simulation technology, the recovery mechanism of single event upset and the effects of spacing and hit angle on the recovery are studied. It is found that the multi-node charge collection plays a key role in recovery and shielding the charge sharing by adding guard rings. It cannot exhibit the recovery effect. It is also indicated that the upset linear energy transfer （LET） threshold is kept constant while the recovery LET threshold increases as the spacing increases. Additionally, the effect of incident angle on recovery is analysed and it is shown that a larger angle can bring about a stronger charge sharing effect, thus strengthening the recovery ability.
文摘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.
基金Project supported by the State Key Program of the National Natural Science Foundation of China (Grant No. 60836004)Hunan Provincial Innovation Foundation for Postgraduates,China (Grant No. CX2011B026)
文摘Using computer-aided design three-dimensional simulation technology,the supply voltage scaled dependency of the recovery of single event upset and charge collection in static random-access memory cells are investigated.It reveals that the recovery linear energy transfer threshold decreases with the supply voltage reducing,which is quite attractive for dynamic voltage scaling and subthreshold circuit radiation-hardened design.Additionally,the effect of supply voltage on charge collection is also investigated.It is concluded that the supply voltage mainly affects the bipolar gain of the parasitical bipolar junction transistor（BJT） and the existence of the source plays an important role in supply voltage variation.
