Signals arrive out of phase at the intended receiver from collaborative beamforming （CB） nodes due to the instability in the output frequency signals of the universal software radio peripheral＇s （USRP） local osci...Signals arrive out of phase at the intended receiver from collaborative beamforming （CB） nodes due to the instability in the output frequency signals of the universal software radio peripheral＇s （USRP） local oscillator （LO）. These nodes including the target must synchronize their oscillator frequencies for coherent signal reception. In order to do this, frequencies and phases of the signals should be estimated in software defined radio （SDR） and smoothen with nonlinear filters such as the extended Kalman filter （EKF）. The process noise parameters of the NI USRP-2920 nodes will have to be calculated and used with the EKF process noise covariance matrix. These nodes are green communication hardware devices where most of the hardware units are now software defined. This article uses the direct spectrum method to obtain the phase noise values at various frequency offsets of the NI USRP-2920 in order to calculate the power spectral density of fractional frequency fluctuation. By applying the power-law noise model to this obtained value, the generated white frequency noise and random walk frequency noise values are q_1=1.93x10^-21 and q_2=5.86x10^-18, respectively.展开更多
In this paper, we present a protocol, CEWEC （Collaborative, Event-Triggered, Weighted, Energy-Efficient Clustering） , based on collaborative beamfor^ning. It is designed for wireless sensor nodes to realize the long...In this paper, we present a protocol, CEWEC （Collaborative, Event-Triggered, Weighted, Energy-Efficient Clustering） , based on collaborative beamfor^ning. It is designed for wireless sensor nodes to realize the long-distance transmission. In order to save the energy of sensor nodes, a node ＂wakes up ＂when it has data to be uploaded. In our protocol, multi-layer structure is adopted： trigger-node layers, clusterhead-node layers, child- node layers. The number of child nodes and clusterheads depends on the distance of transmission. Clusterheads are selected according to the node 5 s weight which is based on its residual energy and distance to the trigger node. The main characteristic of this protocol is that clusterheads can directly communication with each other without the large-scale base station and antennas. Thus, the data from the trigger node would be able to be shared within the multi-layer structure. Considering the clustering process, energy model, and success rate, the simulation results show that the CEWEC protocol can effectively manage a large number of sensor nodes to share and transmit data.展开更多
A novel collaborative beamforming algorithm is proposed in a wireless communication system with multiple transmitters and one receiver. All transmitters take part in the collaboration and the weighted message is trans...A novel collaborative beamforming algorithm is proposed in a wireless communication system with multiple transmitters and one receiver. All transmitters take part in the collaboration and the weighted message is transmitted simultaneously. In order to maximize the beamforming gain, the transmitters use one bit feedback information to adjust the phase offset. It tracks the direction in which the signal strength at the receiver can increase. The directional search and perturbation theory is used to achieve the phase alignment. The feasibility of the proposed algorithm is proved both experimentally and theoretically. Simulation results show that the proposed algorithm can improve the convergent speed of the phase alignment.展开更多
基金supported by the Ministry of Education Malaysia,Universiti Teknologi Malaysia and RUG vote 11H60
文摘Signals arrive out of phase at the intended receiver from collaborative beamforming （CB） nodes due to the instability in the output frequency signals of the universal software radio peripheral＇s （USRP） local oscillator （LO）. These nodes including the target must synchronize their oscillator frequencies for coherent signal reception. In order to do this, frequencies and phases of the signals should be estimated in software defined radio （SDR） and smoothen with nonlinear filters such as the extended Kalman filter （EKF）. The process noise parameters of the NI USRP-2920 nodes will have to be calculated and used with the EKF process noise covariance matrix. These nodes are green communication hardware devices where most of the hardware units are now software defined. This article uses the direct spectrum method to obtain the phase noise values at various frequency offsets of the NI USRP-2920 in order to calculate the power spectral density of fractional frequency fluctuation. By applying the power-law noise model to this obtained value, the generated white frequency noise and random walk frequency noise values are q_1=1.93x10^-21 and q_2=5.86x10^-18, respectively.
基金Sponsored by the National Natural Science Foundation of China(Grant No.61301100)
文摘In this paper, we present a protocol, CEWEC （Collaborative, Event-Triggered, Weighted, Energy-Efficient Clustering） , based on collaborative beamfor^ning. It is designed for wireless sensor nodes to realize the long-distance transmission. In order to save the energy of sensor nodes, a node ＂wakes up ＂when it has data to be uploaded. In our protocol, multi-layer structure is adopted： trigger-node layers, clusterhead-node layers, child- node layers. The number of child nodes and clusterheads depends on the distance of transmission. Clusterheads are selected according to the node 5 s weight which is based on its residual energy and distance to the trigger node. The main characteristic of this protocol is that clusterheads can directly communication with each other without the large-scale base station and antennas. Thus, the data from the trigger node would be able to be shared within the multi-layer structure. Considering the clustering process, energy model, and success rate, the simulation results show that the CEWEC protocol can effectively manage a large number of sensor nodes to share and transmit data.
基金supported by the National Natural Science Foundation of China(6130115561571003)+2 种基金the Ministry of Education(MCM20130111)the Funds for the Central Universities(ZYGX2014J001)the State Grid Power(W2015000333)
文摘A novel collaborative beamforming algorithm is proposed in a wireless communication system with multiple transmitters and one receiver. All transmitters take part in the collaboration and the weighted message is transmitted simultaneously. In order to maximize the beamforming gain, the transmitters use one bit feedback information to adjust the phase offset. It tracks the direction in which the signal strength at the receiver can increase. The directional search and perturbation theory is used to achieve the phase alignment. The feasibility of the proposed algorithm is proved both experimentally and theoretically. Simulation results show that the proposed algorithm can improve the convergent speed of the phase alignment.
