This paper presents a new algorithm based on the power inversion (PI) and the linearly constrained minimum variance (LCMV). This algorithm is capable of adjusting the weights of the antenna array in real time to r...This paper presents a new algorithm based on the power inversion (PI) and the linearly constrained minimum variance (LCMV). This algorithm is capable of adjusting the weights of the antenna array in real time to respond to and improve the global positioning system (GPS) received signals coming from the desired directions and at the same time to highly suppress the jammers coming from the other directions. The simulation is performed for fixed and moving jammers. It indicates that this structure can give deeper nulls, more than 115 dB depths for fixed jammers and more than 94 dB depths for moving jammers.展开更多
Hybrid Distributed Coordination Function (HDCF),a modified medium access control pro-tocol of IEEE 802.11 standard,is proposed in this paper to support both smart adaptive array anten-nas and normal omni-directional a...Hybrid Distributed Coordination Function (HDCF),a modified medium access control pro-tocol of IEEE 802.11 standard,is proposed in this paper to support both smart adaptive array anten-nas and normal omni-directional antennas simultaneously in one wireless LAN. Omni-directional an-tennas follow the standard Distributed Coordination Function (DCF) and smart antennas follow the Directional DCF (DDCF). The proposed DDCF is based on Hybrid Virtual Carrier Sense (HVCS) mechanism,which includes Omni-directional Request-To-Send/Clear-To-Send (ORTS/OCTS) hand-shake mechanism and directional data transmission. HDCF is compatible with DCF. When a node transmits in a directional beam,the other nodes can multiplex the physical channel. Hence,HDCF supports Space Division Multiple Access (SDMA). Simulation results show that HDCF can support hybrid antennas effectively and provide much higher network throughput and lower delay and jitter than DCF does.展开更多
Considering that perfect channel state information(CSI) is difficult to obtain in practice,energy efficiency(EE) for distributed antenna systems(DAS) based on imperfect CSI and antennas selection is investigated in Ra...Considering that perfect channel state information(CSI) is difficult to obtain in practice,energy efficiency(EE) for distributed antenna systems(DAS) based on imperfect CSI and antennas selection is investigated in Rayleigh fading channel.A novel EE that is defined as the average transmission rate divided by the total consumed power is introduced.In accordance with this definition,an adaptive power allocation(PA) scheme for DAS is proposed to maximize the EE under the maximum transmit power constraint.The solution of PA in the constrained EE optimization does exist and is unique.A practical iterative algorithm with Newton method is presented to obtain the solution of PA.The proposed scheme includes the one under perfect CSI as a special case,and it only needs large scale and statistical information.As a result,the scheme has low overhead and good robustness.The theoretical EE is also derived for performance evaluation,and simulation result shows the validity of the theoretical analysis.Moreover,EE can be enhanced by decreasing the estimation error and/or path loss exponents.展开更多
For the application of wireless sensor networks in the military field, one of the main challenges is security. To solve the problem of verifying the location claim for a node, a new location verifica- tion algorithm c...For the application of wireless sensor networks in the military field, one of the main challenges is security. To solve the problem of verifying the location claim for a node, a new location verifica- tion algorithm called node cooperation based location secure verification (NCBLSV) algorithm is proposed. NCBLSV could verify malicious nodes by contrasting neighbor nodes and nodes under beam width angle using an adaptive array antenna at a base point. Simulation experiments are con- ducted to evaluate the performance of this algorithm by varying the communication range and the an- tenna beam width angle. Results show that NCBLSV algorithm has high probability of successful ma- licious nodes detection and low probability of false nodes detection. Thus, it is proved that the NCBLSV algorithm is useful and necessary in the wireless sensor networks security.展开更多
The adaptive array antenna may be considered as a general sidelobe canceller. Directional interference suppression is based on a recursive state estimation of Kalman filter. For the stationary filter,this leads to an...The adaptive array antenna may be considered as a general sidelobe canceller. Directional interference suppression is based on a recursive state estimation of Kalman filter. For the stationary filter,this leads to an iterative solution of Wiener Hops matrix equation. The performance of sidelobe canceller are studied by computer simulation. The result of simulation shows that the sidelobe canceller may be regarded as a special case of an adaptive array atenna.展开更多
A multi-beam adaptive antenna is investigated by considering the adaptive beam forming performance for time-variant channels on the focus of mobile to base station or reverse link. This antenna is constructed by Fresn...A multi-beam adaptive antenna is investigated by considering the adaptive beam forming performance for time-variant channels on the focus of mobile to base station or reverse link. This antenna is constructed by Fresnel zone phase-correcting plane (FZP) focusing element and uniformly spaced feeds array. An estimator for the beamforming weight vector in the presence of angle spreads is derived using a code filtering approach. Owing to the time-varying nature of the channels, a recursive method for computing and tracking the above optimal weight vector solution that is easy to implement is applied. The effects of angle spread, maximum Doppler frequency, and forgetting factor are studied. Simulation results showed that this type of adaptive antenna is capable of performing adaptive beam forming for time-variant channels effectively.展开更多
Downlink transmit beamforming is a promising technique to reduce interference, and power control is a technique to adjust transmission power to satisfy the link quality. Joint transmission power control and beamformin...Downlink transmit beamforming is a promising technique to reduce interference, and power control is a technique to adjust transmission power to satisfy the link quality. Joint transmission power control and beamforming are proposed to minimize total transmission power. The joint optimization problem is solved by receiver beamforming and power control in virtual uplink. SIR based power control is performed to adjust the power allocation, and transmit beamforming weight vectors are determined by Minimum Variance Distortionless Response (MVDR) criterion. The multipath combining weight vectors are determined by maximum ratio combining criterion. Simulation results show the joint optimization scheme decreases the transmission power, and system performance is enhanced.展开更多
文摘This paper presents a new algorithm based on the power inversion (PI) and the linearly constrained minimum variance (LCMV). This algorithm is capable of adjusting the weights of the antenna array in real time to respond to and improve the global positioning system (GPS) received signals coming from the desired directions and at the same time to highly suppress the jammers coming from the other directions. The simulation is performed for fixed and moving jammers. It indicates that this structure can give deeper nulls, more than 115 dB depths for fixed jammers and more than 94 dB depths for moving jammers.
文摘Hybrid Distributed Coordination Function (HDCF),a modified medium access control pro-tocol of IEEE 802.11 standard,is proposed in this paper to support both smart adaptive array anten-nas and normal omni-directional antennas simultaneously in one wireless LAN. Omni-directional an-tennas follow the standard Distributed Coordination Function (DCF) and smart antennas follow the Directional DCF (DDCF). The proposed DDCF is based on Hybrid Virtual Carrier Sense (HVCS) mechanism,which includes Omni-directional Request-To-Send/Clear-To-Send (ORTS/OCTS) hand-shake mechanism and directional data transmission. HDCF is compatible with DCF. When a node transmits in a directional beam,the other nodes can multiplex the physical channel. Hence,HDCF supports Space Division Multiple Access (SDMA). Simulation results show that HDCF can support hybrid antennas effectively and provide much higher network throughput and lower delay and jitter than DCF does.
基金partially supported by the National Natural Science Foundation of China(61571225,61271255,61232016,U1405254)the Open Foundation of Jiangsu Engineering Center of Network Monitoring(Nanjing University of Information Science and Technology)(Grant No.KJR1509)+2 种基金the PAPD fundthe CICAEET fundShenzhen Strategic Emerging Industry Development Funds(JSGG20150331160845693)
文摘Considering that perfect channel state information(CSI) is difficult to obtain in practice,energy efficiency(EE) for distributed antenna systems(DAS) based on imperfect CSI and antennas selection is investigated in Rayleigh fading channel.A novel EE that is defined as the average transmission rate divided by the total consumed power is introduced.In accordance with this definition,an adaptive power allocation(PA) scheme for DAS is proposed to maximize the EE under the maximum transmit power constraint.The solution of PA in the constrained EE optimization does exist and is unique.A practical iterative algorithm with Newton method is presented to obtain the solution of PA.The proposed scheme includes the one under perfect CSI as a special case,and it only needs large scale and statistical information.As a result,the scheme has low overhead and good robustness.The theoretical EE is also derived for performance evaluation,and simulation result shows the validity of the theoretical analysis.Moreover,EE can be enhanced by decreasing the estimation error and/or path loss exponents.
基金Supported by the National High Technology Research and Development Programme of China ( No. 2004AA001210) and the National Natural Science Foundation of China (No. 60532030).
文摘For the application of wireless sensor networks in the military field, one of the main challenges is security. To solve the problem of verifying the location claim for a node, a new location verifica- tion algorithm called node cooperation based location secure verification (NCBLSV) algorithm is proposed. NCBLSV could verify malicious nodes by contrasting neighbor nodes and nodes under beam width angle using an adaptive array antenna at a base point. Simulation experiments are con- ducted to evaluate the performance of this algorithm by varying the communication range and the an- tenna beam width angle. Results show that NCBLSV algorithm has high probability of successful ma- licious nodes detection and low probability of false nodes detection. Thus, it is proved that the NCBLSV algorithm is useful and necessary in the wireless sensor networks security.
文摘The adaptive array antenna may be considered as a general sidelobe canceller. Directional interference suppression is based on a recursive state estimation of Kalman filter. For the stationary filter,this leads to an iterative solution of Wiener Hops matrix equation. The performance of sidelobe canceller are studied by computer simulation. The result of simulation shows that the sidelobe canceller may be regarded as a special case of an adaptive array atenna.
基金the Natural Science Foundation of Chongqing Municipal (CSTC2006BB2360)
文摘A multi-beam adaptive antenna is investigated by considering the adaptive beam forming performance for time-variant channels on the focus of mobile to base station or reverse link. This antenna is constructed by Fresnel zone phase-correcting plane (FZP) focusing element and uniformly spaced feeds array. An estimator for the beamforming weight vector in the presence of angle spreads is derived using a code filtering approach. Owing to the time-varying nature of the channels, a recursive method for computing and tracking the above optimal weight vector solution that is easy to implement is applied. The effects of angle spread, maximum Doppler frequency, and forgetting factor are studied. Simulation results showed that this type of adaptive antenna is capable of performing adaptive beam forming for time-variant channels effectively.
基金This work is supported by Hi Tech Research and Development Program of China"863"(No.2004AA123180).
文摘Downlink transmit beamforming is a promising technique to reduce interference, and power control is a technique to adjust transmission power to satisfy the link quality. Joint transmission power control and beamforming are proposed to minimize total transmission power. The joint optimization problem is solved by receiver beamforming and power control in virtual uplink. SIR based power control is performed to adjust the power allocation, and transmit beamforming weight vectors are determined by Minimum Variance Distortionless Response (MVDR) criterion. The multipath combining weight vectors are determined by maximum ratio combining criterion. Simulation results show the joint optimization scheme decreases the transmission power, and system performance is enhanced.