Performance of fixed relays in orthogonal frequency division multiple access （0FDMA） systems, especially the coverage and capacity performance at the cell edge, is evaluated in this paper. Two methods, theoretical a...Performance of fixed relays in orthogonal frequency division multiple access （0FDMA） systems, especially the coverage and capacity performance at the cell edge, is evaluated in this paper. Two methods, theoretical analysis and calculation and Monte Carlo simulation, are used for the evaluations. By theoreti- cal analysis and calculation, frequency efficiency equation of a relay is introduced and numerical results are calculated. Monte Carlo simulation results also verify that the calculation method is reasonable. The evaluation shows that a relay can increase system performance to a certain level if it is designed appropriately, otherwise it will be harmful for the system performance, even to reduce it.展开更多
In limited feedback-based CloudRAN(C-RAN) systems,the inter-cluster and intra-cluster interference together with the quantification error can seriously deteriorates the system spectral efficiency.We,in this paper,prop...In limited feedback-based CloudRAN(C-RAN) systems,the inter-cluster and intra-cluster interference together with the quantification error can seriously deteriorates the system spectral efficiency.We,in this paper,propose an efficient three-phase framework and corresponding algorithms for dealing with this problem.Firstly,a greedy scheduling algorithm based on the lower bound of the ergodic rate is performed for generating an elementary cluster in the first phase.And then the elementary cluster is divided into many small clusters according to the following proposed algorithms based on the short term instantaneous information in the second phase.In the end,based on the limited feedback two zero-forcing(ZF) precoding strategies are adopted for reducing the intra-cluster interference in the third phase.The provided Monte Carlo simulations show the effectiveness of our proposed algorithms in the respect of system spectral efficiency and average user rate.展开更多
An enhanced extended Kalman filtering （E2KF） algorithm is proposed in this paper to cope with the joint multiple carrier frequency offsets （CFOs） and time-variant channel estimate for MIMO-OFDM systems over high m...An enhanced extended Kalman filtering （E2KF） algorithm is proposed in this paper to cope with the joint multiple carrier frequency offsets （CFOs） and time-variant channel estimate for MIMO-OFDM systems over high mobility scenarios. It is unveiled that, the auto-regressive （AR） model not only provides an effective method to capture the dynamics of the channel parameters, which enables the prediction capability in the EKF algorithm, but also suggests an method to incorporate multiple successive pilot symbols for the improved measurement update.展开更多
In the review paper of N. J. Fish, the topics concerning the basic theory of lower hybrid wave heating and current drive are presented. In the consideration of radio-frequency heating and current drive of tokamak plas...In the review paper of N. J. Fish, the topics concerning the basic theory of lower hybrid wave heating and current drive are presented. In the consideration of radio-frequency heating and current drive of tokamak plasma near the lower hybrid frequency, the parallel wave length is imposed by the coupling device parallel to the magnetic field and is modified by gradients along the field. The important effects are found on wave penetration and damping when the toroidal aspect ratio is low. It may be possible to change the plasma current via electron Landau damping with a coupler rf power spectrum.展开更多
One of the most important electron density diagnostics, microwave reflectometry, has been developed on many large and medium nuclear fusion devices in recent years . Not only the electron density profiles with high te...One of the most important electron density diagnostics, microwave reflectometry, has been developed on many large and medium nuclear fusion devices in recent years . Not only the electron density profiles with high temporal and spatial resolutions, but also the profiles of plasma rotation and turbulence can be obtained with this diagnostic system.展开更多
文摘Performance of fixed relays in orthogonal frequency division multiple access （0FDMA） systems, especially the coverage and capacity performance at the cell edge, is evaluated in this paper. Two methods, theoretical analysis and calculation and Monte Carlo simulation, are used for the evaluations. By theoreti- cal analysis and calculation, frequency efficiency equation of a relay is introduced and numerical results are calculated. Monte Carlo simulation results also verify that the calculation method is reasonable. The evaluation shows that a relay can increase system performance to a certain level if it is designed appropriately, otherwise it will be harmful for the system performance, even to reduce it.
基金supported by the National Natural Science Foundation of China(NSFC) under Grant(No. 61461136001)
文摘In limited feedback-based CloudRAN(C-RAN) systems,the inter-cluster and intra-cluster interference together with the quantification error can seriously deteriorates the system spectral efficiency.We,in this paper,propose an efficient three-phase framework and corresponding algorithms for dealing with this problem.Firstly,a greedy scheduling algorithm based on the lower bound of the ergodic rate is performed for generating an elementary cluster in the first phase.And then the elementary cluster is divided into many small clusters according to the following proposed algorithms based on the short term instantaneous information in the second phase.In the end,based on the limited feedback two zero-forcing(ZF) precoding strategies are adopted for reducing the intra-cluster interference in the third phase.The provided Monte Carlo simulations show the effectiveness of our proposed algorithms in the respect of system spectral efficiency and average user rate.
文摘An enhanced extended Kalman filtering （E2KF） algorithm is proposed in this paper to cope with the joint multiple carrier frequency offsets （CFOs） and time-variant channel estimate for MIMO-OFDM systems over high mobility scenarios. It is unveiled that, the auto-regressive （AR） model not only provides an effective method to capture the dynamics of the channel parameters, which enables the prediction capability in the EKF algorithm, but also suggests an method to incorporate multiple successive pilot symbols for the improved measurement update.
基金Supported by the National Natural Science Foundation of China（10075016, I0275018. 10135020）
文摘In the review paper of N. J. Fish, the topics concerning the basic theory of lower hybrid wave heating and current drive are presented. In the consideration of radio-frequency heating and current drive of tokamak plasma near the lower hybrid frequency, the parallel wave length is imposed by the coupling device parallel to the magnetic field and is modified by gradients along the field. The important effects are found on wave penetration and damping when the toroidal aspect ratio is low. It may be possible to change the plasma current via electron Landau damping with a coupler rf power spectrum.
文摘One of the most important electron density diagnostics, microwave reflectometry, has been developed on many large and medium nuclear fusion devices in recent years . Not only the electron density profiles with high temporal and spatial resolutions, but also the profiles of plasma rotation and turbulence can be obtained with this diagnostic system.
