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为了表述无线信道衰落的时变及远区分布特性,提出了利用时域有限差分(FDTD)方法研究由多径效应引起的时变无线信道衰落的方法。在此将无线信道的衰落建模为随机过程,而不是通常的确定性随机变量。首先基于Clarke统计模型,利用FDTD方法研究了时变无线信道的小尺度平坦衰落特征;然后利用Monte Carlo方法和FDTD方法产生了具有信道多普勒功率谱特性的色高斯随机过程,再基于无线信道的时变统计特性建模,用Suzuki模型研究了时变无线信道的快衰落;最后将无线信道衰落特性分布和理论分布做了比较,验证了方法的有效性。 相似文献
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从理论上分析了多径效应和多普勒效应对无线信道的影响,并分别从时域和频域给出了信号经历信道后的仿真图形,分析了典型时变多径衰落信道理论模型,并在此基础上建立了抽头延迟线(TDL)的确定性仿真模型;仿真分析表明,通过改变时延功率谱和确定性模型的参数计算方法,此模型可以进一步扩展并用于多种传播环境下的小尺度衰落仿真。 相似文献
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对衰落信道的准确建模对于自适应无线通信、认知无线电等应用中的信道预测具有重要意义。针对噪声功率存在时变特性的无线通信应用环境,提出了一种新的瑞利衰落信道的有限状态Markov模型。通过将接收信号的衰落电平进行离散化处理,建立了衰落电平区间与Markov模型状态之间的一一对应关系,推导了门限电平与状态转移概率和状态分布概率之间的理论关系式,并在此基础上提出了一种易于实现的基于等概率的信道模型。理论分析与仿真结果表明:在噪声功率时变的条件下,已有的基于信噪比的模型失效,而该模型能准确反映信道的衰落特性,最大相对误差小于7%。 相似文献
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飞行器不同飞行阶段经历的信道特性不同,多普勒频谱是表征信道特性的重要物理量.飞行器在某些飞行阶段下与地面站间存在可视通路,某些阶段下又不存在,导致地空信道特性复杂多变.基于散射体模型对飞行器从起飞到着陆的各个阶段的信道的多普勒谱做了仿真分析.仿真结果表明,飞行器在航行、到达/起飞、滑行阶段多普勒谱为Rician型,停场阶段为Rayleigh型. 相似文献
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Xu Feng Yue Dianwu 《电子科学学刊(英文版)》2007,24(4):462-469
Space time block coding is a modulation scheme recently discovered for the transmit an- tenna diversity to combat the effects of wireless fading channels. Using the equivalent Single-Input Single-Output (SISO) model, this paper presents closed-form expressions for the exact Symbol Error Rate (SER) and Bit Error Rate (BER) of Orthogonal Space-Time Block Codes (OSTBCs) with M-ary Phase-Shift Keying (MPSK) and M-ary Quadrature Amplitude Modulation (MQAM) over flat un- correlated Nakagami-m and Ricean fading channels. 相似文献
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计算机仿真无线Rice衰落信道的实现方法 总被引:4,自引:3,他引:1
应用第一类零阶修正的贝塞尔函数I0(x)一个近似式,推导Rice随机变量的概率分布函数(CDF)的近似闭式.采用蒙特卡洛法用计算机仿真生成Rice分布的随机变量序列.Rice分布的PDF仿真结果与理论值比较表明:两者是基本一致的.文中还介绍了采用此法来生成Nakagami-m 分布的随机变量序列,并给出仿真结果.该方法可以直接用于仿真Rice或Nakagami-m衰落信道环境下的无通信系统的传输特性研究. 相似文献
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Carlos A. Gutirrez Matthias Ptzold 《Wireless Communications and Mobile Computing》2013,13(10):951-966
We present in this paper a generalized version of the method of equal areas (MEA) that is well suited for the design of sum‐of‐cisoids (SOC) simulators for narrowband mobile Rayleigh fading channels characterized by any type of Doppler power spectral densities (DPSDs). Unlike the original MEA, the generalized MEA (GMEA) can be applied to the simulation of fading channels with asymmetrical DPSDs. This is an important feature because the simulation of such channels is of great interest for the laboratory analysis of mobile communication systems under non‐isotropic scattering conditions. We show that irrespective of the underlying DPSD, the GMEA results in a very good approximation to the autocorrelation function, average Doppler shift, Doppler spread, and envelope distribution of the channel. We compare the performance of the GMEA with that of the Lp‐norm method (LPNM), which is the method that has been most widely used for designing SOC simulators for fading channels with arbitrary DPSDs. The obtained results demonstrate that the performance of the GMEA measures up to that of the LPNM. In addition, the results show that the determination of the model parameters is easier and less time‐consuming when applying the GMEA. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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瑞利衰落信道中移动OFDM的Doppler Spread估计 总被引:1,自引:1,他引:0
提出了一种在瑞利衰落信道中移动多载波调制(OFDM)接收机的Doppler Spread估计方法.利用OFDM符号所固有的循环前缀,采用自相关检测方法,可以较准确地估计由于移动接收机运动所引起的Doppler Spread.在保证OFDM循环符号结构的条件下,不需要增加辅助导频和训练序列,可以直接用于普通OFDM接收机,以及采用发送分集(TD)和多输入输出(MIMO)技术的移动OFDM通信系统.理论分析和实验结果证明了方案的可行性. 相似文献
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To evaluate mobile communication systems, it is important to develop accurate and concise fading channel models. However, fading encountered in mobile communication is usually non‐stationary, and the existing methods can only model quasi‐stationary or piecewise‐stationary fading instead of general non‐stationary fading. To address this, this paper proposes an evolutionary spectrum (ES)‐based approach to modeling non‐stationary fading channels. Our ES approach is more general than the existing piecewise‐stationary models and is capable of characterizing a general non‐stationary fading channel that has an arbitrary ES (or time‐varying power spectral density); our ES approach is parsimonious and is also able to generate stationary fading processes. As an example, we show how to apply our ES approach to generating stationary and non‐stationary correlated Nakagami‐m fading channel processes. Simulation results show that the ES of the channel gain process produced by our ES‐based channel model agrees well with the user‐specified ES, indicating the accuracy of our ES‐based channel model. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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本文讨论了Nakagami-m衰落信道系统的中断容量性能,在发射端未知信道信息,接收端的信道估计存在误差时,给出了计算中断容量上界和下界的表达式,它们是接收端的估计误差和信道参数的函数,仿真结果表明随着估计误差的增大中断容量的上界和下界同时降低,但是中断容量的下界随着信道参数的增大而增大,上界随着信道参数的增大而减小。 相似文献
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I. Korn 《International Journal of Satellite Communications and Networking》1997,15(3):101-115
In this paper the bit error probability (BEP) of narrowband M-ary differential phase shift keying with differential phase detection (MDPSK-DPD) and maximum ratio combining (MRC) in Rician fading channels is computed. Two systems shall be investigated. In the first system the transmitted pulse is a Nyquist pulse with bandwidth B = R(1 + β), where R is the symbol rate and 0 ≤ β ≤ 1 is the roll-off and the receiver is matched to the transmitter. In the second system the shaping pulse is a rectangle of duration T = 1/R modified by narrowband Butterworth filters in the transmitter and receiver. The fading channel is both time selective with Doppler frequency shifts of fDT = 0, 0·01, 0·02 and frequency selective with time delays of td/T = 0, 0·1, 0·2. The number of diversity channels is L = 1, 2, 3 and the Rician factor is K = 0, 1, 6 dB, 10, ∞, thus the whole range between Rayleigh and Gaussian channels is covered. © 1997 John Wiley & Sons, Ltd. 相似文献
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Nakagami-m衰落信道下空时分组码的性能估计 总被引:2,自引:0,他引:2
基于等效单输入单输出SISO (Single-input Single-output) 模型,利用矩量母函数 (MGF) 分析法,空时分组码STBC (Space-Time Block Coding) 的误符号率是可以得到其准确闭式表达式的.对于独立同分布Nakagami-m衰落信道下的空时分组码的性能进行了研究,给出了采用M-PSK 和M-QAM调制方案的不同空时分组编码矩阵误符号率的闭式解以及基于闭式解的解析性能结果,通过蒙特卡洛仿真验证了闭式解的准确性.还从调制方案的角度对于几种新的空时分组码的性能进行了一些新的讨论. 相似文献
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Kai Yu Pingzhi Fan Li Hao Xianfu Lei 《Wireless Communications and Mobile Computing》2012,12(6):503-515
In this paper, large code division multiple access (CDMA) random access systems employing the decorrelator and minimum mean square error (MMSE) detectors are investigated over Rayleigh fading channels under the assumption that both the number of users and the spreading gain tend to infinity, but their ratio converges to a constant. The signal to interference ratio (SIR) is shown to converge almost surely to a constant and the bit‐error rate (BER) is expressed as a function of the traffic load, transmission probability, channel coefficient, and distribution of transmission power. Furthermore, the throughput, the spectrum efficiency, and the stability region are analyzed and simulated. For dominating systems, it is shown that the MMSE detector achieves much higher throughput and spectral efficiency than decorrelator detector. Besides, it is also disclosed that, when the signal to noise ratio (SNR) is larger than an optimum value, the spectrum efficiency increases as the ratio of bit energy to noise power spectrum density (Eb/N0) increases; however, when SNR is smaller than the optimum value, the spectrum efficiency decreases as Eb/N0 increases. For ordinary stable systems, it is demonstrated that their stability region gets narrower as the traffic load increases. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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智能车载协作系统中车辆快速移动使得无线通信信道具有时变特性,为有效评估系统的误码性能,给出了符合车载时变信道的一阶自回归(AR1)模型,提出了一种基于AR1模型的自适应解码转发(ADF)协作误码率分析方法.该方法通过AR1模型的多普勒频偏相关系数来刻画时变信道特性,根据中继译码结果自适应选择是否协作转发,提升了智能交通系统的可靠性.此外,利用矩生成函数(MGF)推导出ADF协作下多进制正交幅度调制(M-QAM)信号误码率封闭表达式,并分析了车载移动速度和信道状态信息(CSI)估计精度对误码性能的影响.数值仿真结果表明,车载系统能通过增加CSI估计精度,有效地减少车载快速移动引起的误码平顶值.该方法相对于放大转发(AF)协作通信方式,平均误码性能提高约8.7 dB. 相似文献