共查询到20条相似文献,搜索用时 0 毫秒
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YANG Shan CUI Qi-mei XU Yue-qiao LUO Yuan Key Laboratory of Universal Wireless Communications Ministry of Education Beijing University of Posts Telecommunications Beijing China 《中国邮电高校学报(英文版)》2011,(5):1-6
Power allocation(PA)plays an important role in capacity improvement for cooperative multiple-input multiple-output(Co-MIMO)systems.Many contributions consider a total power constraint(TPC)on the sum of transmit power from all nodes in addressing PA problem.However,in practical implementations,each transmit node is equipped with its own power amplifier and is limited by individual power constraint(IPC).Hence these PA methods under TPC are not realizable in practical systems.Meanwhile,the PA problem under IPC is essential,but it has not been studied.This paper extends the traditional non-cooperative water-filling PA algorithm to IPC-based Co-MIMO systems.Moreover,the PA matrix is derived based on the compound channel matrix from all the cooperative nodes to the user.Therefore,the cooperative gain of the IPC-based Co-MIMO systems is fully exploited,and further the maximal instantaneous capacity is achieved.Numerical simulations validate that,under the same IPC conditions,the proposed PA scheme considerably outperforms the non-cooperative water-filling PA and uniform PA design in terms of ergodic capacity. 相似文献
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Katayama M. Yamazato T. Okada H. 《Selected Areas in Communications, IEEE Journal on》2006,24(7):1267-1276
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es and the radiation field are finally determined. 相似文献
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An optimal power allocation (OPA) method with mean channel gains is proposed for a multinode amplify-and-forward cooperative communication system. By making use of M-PSK modulation, a closed-form symbol-error-rate (SER) formulation and corresponding upper bound are first derived. Subsequently the OPA method is utilized to minimize the SER. Comparison of the SER of the proposed OPA method with that of the equal power allocation (EPA) method, shows that the SER of both methods, which is approximately optimal performance, is almost the same when relays are near the source. OPA outperforms the EPA when the relays are near the middle between the source and destination or near the destination. The proposed OPA method depends only on the ratio of mean channel gains of the source-to-relay to those of the relay-to-destination. Extensive simulations are performed to validate the theoretical results. 相似文献
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协同通信系统中基于遍历容量的近似最优功率分配 总被引:2,自引:1,他引:1
传统半双工放大转发(AF)协同通信无论信道状态如何,总是采用协同通信模式,在一定程度上降低了系统自由度的利用率.基于此研究了"何时协同"与最优发送功率分配的问题.首先给出了AF系统的遍历容量表达式及其上界;然后以遍历容量上界为代价函数,提出一种适用于AF系统的近似最优功率分配方案(AOPA),通过比较源-目的端与中继-目的端的统计信道增益来判定是否需要采用协同通信模式;最后,还分析了在中继端按随机方向模型移动时AOPA方案的性能.理论分析和仿真结果表明,AOPA方案在系统容量和误码差错性能上均要优于等功率EPA方案. 相似文献
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ZhouLerong GuoJinghong WeiGang 《电子科学学刊(英文版)》2004,21(4):332-336
This letter derives the Equivalent M-band Discrete Wavelet(EMDW) transmission mode of Orthogonal Frequency Division Multiplexing(OFDM) transmission systems, and presents a new Quadrature M-band Discrete Wavelet(QMDW) based OFDM-CDMA(Code Division Multiple Access) communication systems for high speed Power Line Communication (PLC) channels,This system gives much better robustness to Inter-Channel Interference (ICI), Multi-User Interference (MUI) and noise interference, which is verified by simulation. 相似文献
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Innovative model for time-varying power line communication channel response evaluation 总被引:1,自引:0,他引:1
Barmada S. Musolino A. Raugi M. 《Selected Areas in Communications, IEEE Journal on》2006,24(7):1317-1326
This work presents a channel model for the broadband characterization of power lines in presence of time variation of the loads. The model is characterized by taking into account both measured and geometrical channel characteristics and can easily be used to take into account also the presence of noise. The channel is described by a two-port equivalent described by a scattering matrix determined from a wavelet-based expansion of the input and output quantities. Upper and lower bounds for the response of the channel in presence of time-varying loads are determined in a fast and efficient way avoiding time consuming Monte Carlo simulations. The bounds determination allows the estimate of noteworthy quantities for the tuning of currently used modulation schemes for power lines communications such as orthogonal frequency-division multiplexing. 相似文献
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为了抑制脉冲噪声对电力线正交频分复用(OFDM)通信系统的影响,最常用的方法之一是在接收端OFDM解调器之前前置一个置零非线性单元,即传统置零法。然而,由于引入了非线性失真,其性能并不理想。针对传统置零法引起的非线性失真问题,提出了一种基于迭代消除非线性失真的改进置零法。首先,对接收到的时域OFDM信号进行脉冲噪声检测和置零处理;然后,在频域利用已检测的符号来重构时域置零处理引入的非线性失真,并通过迭代提高重构的准确性;最后,从频域接收信号中减去重构的非线性失真。仿真结果表明,所提改进算法与传统置零法相比,有非常大的性能提升,增强了电力线OFDM通信系统对脉冲噪声的抵抗能力。 相似文献
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Siriwongpairat W.P. Weifeng Su Olfat M. Liu K.J.R. 《Signal Processing, IEEE Transactions on》2006,54(1):214-224
The emerging ultrawideband (UWB) system offers a great potential for the design of high speed short-range wireless communications. In order to satisfy the growing demand for higher data rates, one possible solution is to exploit both spatial and multipath diversities via the use of multiple-input multiple-output (MIMO) and proper coding techniques. In this paper, we propose a general framework to analyze the performance of multiband UWB-MIMO systems regardless of specific coding schemes. A combination of space-time-frequency (STF) coding and hopping multiband OFDM modulation is also proposed to fully exploit all of the available spatial and frequency diversities, richly inherent in UWB environments. We quantify the performance merits of the proposed scheme in case of Nakagami-m frequency-selective fading channels. Different from the conventional STF coded MIMO-OFDM system, the performance of the STF coded hopping multiband UWB does not depend on the temporal correlation of the propagation channel. We show that the maximum achievable diversity of multiband UWB-MIMO system is the product of the number of transmit and receive antennas, the number of multipath components, and the number of jointly encoded OFDM symbols. Interestingly, the diversity gain does not severely depend on the fading parameter m, and the diversity advantage obtained under Nakagami fading with arbitrary m parameter is almost the same as that obtained in Rayleigh fading channels. Finally, simulation results are presented to support the theoretical analysis. 相似文献
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Data communications over low voltage power distribution networks provide an alternative and cost-effective last mile access technology. It offers data and voice services to users in residential and business areas. Currently, many field trials with different broadband power line communications systems are running worldwide. This article describes one of these systems for the last mile application in European power line networks. It addresses major field deployment aspects, such as range, coverage, coupling, and intercell interference. 相似文献
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Vehicular ad hoc networks play a critical role in enabling important active safety applications such as cooperative collision warning. These active safety applications rely on continuous broadcast of self-information by all vehicles, which allows each vehicle to track all its neighboring cars in real time. The most pressing challenge in such safety-driven communication is to maintain acceptable tracking accuracy while avoiding congestion in the shared channel. In this article we propose a transmission control protocol that adapts communication rate and power based on the dynamics of a vehicular network and safety-driven tracking process. The proposed solution uses a closed-loop control concept and accounts for wireless channel unreliability. Simulation results confirm that if packet generation rate and associated transmission power for safety messages are adjusted in an on-demand and adaptive fashion, robust tracking is possible under various traffic conditions. 相似文献
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The multi-input multi-output (MIMO) communication framework is adopted for wireless sensor networks by having multiple sensors
equipped with single-element antennas cooperate in transmission. A power method-based iterative algorithm is developed that
computes the optimal transmit and receive eigen-filters distributively among the sensors while transferring most of the computational
burden to the central collector node. Since the proposed algorithm implicitly exploits the channel state information (CSI)
both at the receiver and the transmitter, it is expected that the resulting spectral efficiency is higher than what can be
achieved by receive CSI-only space-time coding. This intuition is confirmed by employing a variable-rate adaptive modulation
scheme for the eigen-transmission and comparing its spectral efficiency with that of orthogonal space time block codes (OSTBCs)
at specific target bit error rates. The performance is also evaluated using realistic channel estimation as well as the least
mean square (LMS) and recursive least square (RLS) algorithms for iterative eigencoding.
This material is based upon work supported by the Air Force Office of Scientific Research under Award No. FA9550-04-C-0074
and Toyon Research Corporation Subcontract No. SC6431-1.
Seung-Jun Kim received B.S. and M.S. from Seoul National University in 1996 and 1998, respectively, and Ph.D. from University of California,
Santa Barbara in 2005, all in electrical engineering. From 1998 to 2000, he served as a Korea Overseas Volunteer at Chiang
Rai Teachers College in Chiang Rai, Thailand. Since 2005, he has been with NEC Laboratories America in Princeton, NJ. His
research interests lie in detection/estimation theory, spread-spectrum communications, multiple antenna techniques and cross-layer
design.
Richard E. Cagley received the B.S. degree in engineering from Harvey Mudd College, Claremont, CA in 1997 and the M.S. and Ph.D. degrees in
electrical engineering from the University of California, Santa Barbara in 1999 and 2003 respectively.
Dr. Cagley currently holds a position with Toyon Research Corporation, Goleta, CA. Prior to joining Toyon, he held positions
with Fujant Incorporated, Jet Propulsion Laboratories, and Qualcomm Corporation. His general research interests are in the
areas of physical and MAC layer design for wireless communication. This includes multiuser detection, interference cancellation,
space-time processing, spectrum management, and digital receiver design.
Ronald A. Iltis received the B.A. (Biophysics) from The Johns Hopkins University in 1978, the M.Sc in Engineering from Brown University in
1980, and the Ph.D. in Electrical Engineering from the University of California, San Diego in 1984. Since 1984, he has been
with the University of California, Santa Barbara, where he is currently a Professor in the Department of Electrical and Computer
Engineering. His current research interests are in CDMA, software radio, radiolocation, and nonlinear estimation. He has also
served as a consultant to government and private industry in the areas of adaptive arrays, neural networks and spread-spectrum
communications. Dr. Iltis was previously an Editor for the IEEE Transactions on Communications. In 1990 he received the Fred
W. Ellersick award for best paper at the IEEE MILCOM conference. 相似文献
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Seungwon Choi Jung-Hyun Park Dong-Jo Park 《Communications Letters, IEEE》2008,12(4):271-273
We deal here with distributed cooperative communication systems in which a single source transmits its information with the help of multiple relays to a destination. Specifically, we consider decode and forward relay networks based on orthogonal frequency division multiplexing (OFDM). Most previous work needs a priori information for antenna allocation to obtain cooperative diversity advantages. We propose a simple method that does not require additional information in order to coordinate relay transmission. Our main proposal is to retransmit randomly cyclic-shifted sequences of the received symbol at relays. Simulation results verify that full gain in diversity is achieved when the number of subcarriers is sufficiently large. 相似文献
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现代通信系统电源设计 总被引:1,自引:0,他引:1
DonaldAshley 《今日电子》2004,(12):62-64
通信设备使用的电源器件有很多种,从前端的功率因数校正(PFC)AC/DC电源到后端的高效DC/DC模块和负载点(POL)转换器,不一而足。从需要很高效率的中间总线转换器(IBC),到那些日趋细小轻巧的VoIP数字电话,以及要求多路紧密调节电压(7~13路输出)的数字用户线(xDSL)电源等,DC/DC电源在现代通信中获得了广泛应用。 相似文献
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This paper considers a robust mean-square-error (MSE) equalizer design problem for multiple-input multiple-output (MIMO) communication systems with imperfect channel and noise information at the receiver. When the channel state information (CSI) and the noise covariance are known exactly at the receiver, a minimum-mean-square-error (MMSE) equalizer can be employed to estimate the transmitted signal. However, in actual systems, it is necessary to take into account channel and noise estimation errors. We consider here a worst-case equalizer design problem where the goal is to find the equalizer minimizing the equalization MSE for the least favorable channel model within a neighborhood of the estimated model. The neighborhood is formed by placing a bound on the Kullback-Leibler (KL) divergence between the actual and estimated channel models. Lagrangian optimization is used to convert this min-max problem into a convex min-min problem over a convex domain, which is solved by interchanging the minimization order. The robust MSE equalizer and associated least favorable channel model can then be obtained by solving numerically a scalar convex minimization problem. Simulation results are presented to demonstrate the MSE and bit error rate (BER) performance of robust equalizers when applied to the least favorable channel model. 相似文献
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Jungwon Lee Hui-Ling Lou Toumpakaris D. Jang E.W. Cioffi J.M. 《Communications Magazine, IEEE》2009,47(1):32-40
Hybrid ARQ, an extension of ARQ that incorporates forward error correction coding, is a retransmission scheme employed in current communications systems. The use of HARQ can contribute to efficient utilization of the available resources and the provision of reliable services in latest-generation systems. This article focuses on wireless systems using HARQ with emphasis on the multiple-input multiple-output paradigm. MIMO-HARQ offers new opportunities because of the additional degrees of freedom introduced by the multiple antennas at the transmitter and receiver. The architecture of MIMO transceivers that are based on bit-interleaved coded modulation and employ HARQ is described. Additionally, receiver implementations are presented and compared in terms of complexity, memory requirements, and performance. 相似文献