We propose an inverse method to determine the material parameters of a transparent device without any knowledge of the corresponding transformation function. The required parameters are independently obtained and expr...We propose an inverse method to determine the material parameters of a transparent device without any knowledge of the corresponding transformation function. The required parameters are independently obtained and expressed as functions of the introduced generator. Moreover, to remove the inhomogeneity and anisotropy of material parameters, a layered transparent device composed of only homogeneous and isotropic materials is presented based on the effective medium theory. The feasibility of using the layered device in antenna protection is also investigated. Full-wave simulation is carried out for verification. This work paves a new way toward designing metamaterial devices without specifying the underlying coordinate transformation, and has great guiding significance for the practical fabrication of transparent devices.展开更多
This paper proposes a Service Differentiated-Dynamic Slotted Multiple Access （SD-DSMA） protocol with QoS guarantee. The Media Access Control （MAC） frame format is variable according to the traffic of uplink and do...This paper proposes a Service Differentiated-Dynamic Slotted Multiple Access （SD-DSMA） protocol with QoS guarantee. The Media Access Control （MAC） frame format is variable according to the traffic of uplink and downlink and the traffic of control and data. In addition, the services are divided into two categories, Guaranteed Bandwidth （GB） and Best Effort （BE）. Uplink control message slots are designed for the GB users to reduce contention. Taking into consideration the techniques in physical layer, a two-Dimensional Radio Resource Allocation （2-D RRA） method is proposed. The 2-D RRA is an efficient way to allocate radio resources for multi-cell, multi-user OFDM/TDMA system as it takes into consideration both the channel condition and the co-channel interference. The piggyback mechanism and fair scheduling algorithm are adopted for GB services, and the max C/I scheduling algorithm is used for BE services. The simulation results show that the proposed MAC protocol has better performance in terms of delay, probability of successful access request.展开更多
An outdoor propagation measurement campaign for beyond 3G （B3G） as well as a wide-band indoor measurement campaign have been performed recently in Beijing, China, in which the sounding signals are transmitted by an ...An outdoor propagation measurement campaign for beyond 3G （B3G） as well as a wide-band indoor measurement campaign have been performed recently in Beijing, China, in which the sounding signals are transmitted by an one-antenna base station and received by a two-antenna mobile receiver operated at 3.49～3.51 GHz bandwidth. Different scenarios： stationary line-of-sight （LoS）, stationary non-LoS （NLoS） scenarios, and dynamic NLoS are deliberately chosen in a classic urban environment and office environment. The initial results are presented in this article. Parameters including vector channel impulse response, path loss, rays number, excess delay spread etc. are extracted, analyzed, and briefly reported here.展开更多
A perspective view for next generation mobile wireless network is given in this paper, named as Mobile Ubiquitous Service Environment (MUSE). The main mechanisms and principles for MUSE and related issues are also given.
The Wide-Sense Stationary Uncorrelated Scattering （WSSUS） model has long been viewed as a basic channel model to describe the fading dispersive channel. But non- WSSUS models have more universal applicability when t...The Wide-Sense Stationary Uncorrelated Scattering （WSSUS） model has long been viewed as a basic channel model to describe the fading dispersive channel. But non- WSSUS models have more universal applicability when the wireless mobile channel with broadband is studied with finer and more detailed knowledge of propagation environments. So the four-Dimension （4-D） characteristics of channel, namely time, lag, frequency, and Doppler, should be studied together. In this paper, Wigner-Ville distribution of Time-Frequency （TF） domain is introduced to analyze channel in which the incidence rays are non-stationary and correlated with each other. Several channel models, according to different move modes of incidence rays, with time-varying Doppler shift are designed and 4-D Local Scattering Function （LSF） are computed and simulated respectively. Our simulation results show the LSF present asymmetric and non-periodic TF distri- bution for some symmetric and periodic move modes of incidence rays.展开更多
The long symbol duration makes Orthogonal Frequency Division Multiplexing (OFDM) robust against frequency-selective fading, and also makes OFDM sensitive to time-selective fading. First, this paper deduces the Inter-s...The long symbol duration makes Orthogonal Frequency Division Multiplexing (OFDM) robust against frequency-selective fading, and also makes OFDM sensitive to time-selective fading. First, this paper deduces the Inter-subCarrier Interference (ICI) caused by time-selective fading, and then analyzes in detail how time-selective fading affects the performance of OFDM system, e.g. Bit-Error Rate (BER) and the channel capacity of each subcarrier. At last, some simulation figures are given.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61161007 and 61261002)the Natural Science Foundation of Yunnan Province,China(Grant No.2011FB018)+2 种基金the Postdoctoral Science Foundation of China(Grant No.2013M531989)the Key Program of Natural Science of Yunnan Province,China(Grant No.2013FA006)the Fostering Foundation for the Excellent Ph.D.Dissertation of Yunnan University,China
文摘We propose an inverse method to determine the material parameters of a transparent device without any knowledge of the corresponding transformation function. The required parameters are independently obtained and expressed as functions of the introduced generator. Moreover, to remove the inhomogeneity and anisotropy of material parameters, a layered transparent device composed of only homogeneous and isotropic materials is presented based on the effective medium theory. The feasibility of using the layered device in antenna protection is also investigated. Full-wave simulation is carried out for verification. This work paves a new way toward designing metamaterial devices without specifying the underlying coordinate transformation, and has great guiding significance for the practical fabrication of transparent devices.
基金This workis supported by National Nature Science Foundation of China (60302024 ,60496312 ,60132010) .
文摘This paper proposes a Service Differentiated-Dynamic Slotted Multiple Access （SD-DSMA） protocol with QoS guarantee. The Media Access Control （MAC） frame format is variable according to the traffic of uplink and downlink and the traffic of control and data. In addition, the services are divided into two categories, Guaranteed Bandwidth （GB） and Best Effort （BE）. Uplink control message slots are designed for the GB users to reduce contention. Taking into consideration the techniques in physical layer, a two-Dimensional Radio Resource Allocation （2-D RRA） method is proposed. The 2-D RRA is an efficient way to allocate radio resources for multi-cell, multi-user OFDM/TDMA system as it takes into consideration both the channel condition and the co-channel interference. The piggyback mechanism and fair scheduling algorithm are adopted for GB services, and the max C/I scheduling algorithm is used for BE services. The simulation results show that the proposed MAC protocol has better performance in terms of delay, probability of successful access request.
文摘An outdoor propagation measurement campaign for beyond 3G （B3G） as well as a wide-band indoor measurement campaign have been performed recently in Beijing, China, in which the sounding signals are transmitted by an one-antenna base station and received by a two-antenna mobile receiver operated at 3.49～3.51 GHz bandwidth. Different scenarios： stationary line-of-sight （LoS）, stationary non-LoS （NLoS） scenarios, and dynamic NLoS are deliberately chosen in a classic urban environment and office environment. The initial results are presented in this article. Parameters including vector channel impulse response, path loss, rays number, excess delay spread etc. are extracted, analyzed, and briefly reported here.
文摘A perspective view for next generation mobile wireless network is given in this paper, named as Mobile Ubiquitous Service Environment (MUSE). The main mechanisms and principles for MUSE and related issues are also given.
文摘The Wide-Sense Stationary Uncorrelated Scattering （WSSUS） model has long been viewed as a basic channel model to describe the fading dispersive channel. But non- WSSUS models have more universal applicability when the wireless mobile channel with broadband is studied with finer and more detailed knowledge of propagation environments. So the four-Dimension （4-D） characteristics of channel, namely time, lag, frequency, and Doppler, should be studied together. In this paper, Wigner-Ville distribution of Time-Frequency （TF） domain is introduced to analyze channel in which the incidence rays are non-stationary and correlated with each other. Several channel models, according to different move modes of incidence rays, with time-varying Doppler shift are designed and 4-D Local Scattering Function （LSF） are computed and simulated respectively. Our simulation results show the LSF present asymmetric and non-periodic TF distri- bution for some symmetric and periodic move modes of incidence rays.
文摘The long symbol duration makes Orthogonal Frequency Division Multiplexing (OFDM) robust against frequency-selective fading, and also makes OFDM sensitive to time-selective fading. First, this paper deduces the Inter-subCarrier Interference (ICI) caused by time-selective fading, and then analyzes in detail how time-selective fading affects the performance of OFDM system, e.g. Bit-Error Rate (BER) and the channel capacity of each subcarrier. At last, some simulation figures are given.
