一种新的Jakes模型参数计算方法

本文分析了小尺度无线衰落信道的理论参考模型—Clark模型,比较了两种较为重要的确定性仿真模型的参数计算方法—精确多普勒扩展法（MEDS）和随机精确多普勒扩展法（R_MEDS）,提出了一种新的用于仿真平坦衰落信道Jakes模型的参数计算方法,即在MEDS的基础上对离散多普勒频率引入随机抖动。仿真数据和图形表明,在模型复杂度较低的情况下,新的信道模型的自相关和互相关特性较R_MEDS有很大改善,而且与原始MEDS相比,新模型多普勒频率为随机变量,可以有效仿真瑞利衰落、多个不相关的瑞利衰落和频率选择性衰落信道等,并且可以结合工程需要设定随机抖动幅度,保证了衰落信道的不相关性和遍历性的有机统一。      

Rayleigh衰落信道的建模与仿真

以经典Jakes模型的发展为线索,分析比较了具有代表性的改进Jakes类和非Jakes类模型,通过以瑞利衰落波形的二阶统计特性为判别信道效能的依据,得出高效信道模型所具有的参数特征以及仿真多个独立瑞利衰落波形的方法等.仿真数据表明,模型的精确度是以计算量和复杂度为代价.     

一种改进的瑞利衰落波形仿真方法

在分析比较了蒙特卡罗法、等距法和等面积法的性能基础上,提出了一种改进的瑞利衰落波形的参数计算方法,该方法是在仿真模型的参数确定之前对取样多普勒频率进行了预处理,即进行多次采样并将采样的均值作为瑞利衰落信道的多普勒系数,仿真数据和图形表明新信道仿真模型在自相关统计特性方面,较原蒙特卡罗方法有较大改善,与等距法和等面积法相比使信道参数具有随机性,不仅可以有效仿真单个瑞利衰落,还可以对多个不相关瑞利衰落进行仿真。     

无线信道中一种新的瑞利波形仿真模型

该文提出了一种新的简单的产生满足任意自相关特性的瑞利波形的仿真模型,在此基础上得出无线信道中瑞利衰落波形的产生方法。该方法可以容易地产生多个相互独立的瑞利衰落波形,从而为研究各种频率分集无线通信系统提供了可能。仿真结果表明该模型能够有效地产生符合小尺度无线信道特征的瑞利衰落波形,满足自相关特性及平稳性的要求。     

瑞利衰落信道Jakes模型的研究与性能分析

无线衰落信道是无线通信系统的重要组成部分,因此信道建模和仿真对于无线通信系统的开发具有极其重要的作用。文章通过对平坦瑞利(Rayleigh)衰落信道进行仿真建模研究,给出了瑞利衰落信道可以采用Jakes模型进行建模的分析结果。     

OFDM系统抗多径衰落性能计算机仿真分析

本文分析了多径衰落信道接收信号的特点,建立了多径传播的仿真模型,并对正交频分复用OFDM系统,分别通过AWGN高斯信道、两径瑞利衰落信道、六径瑞利衰落信道进行计算机模拟仿真,得出OFDM系统具有抗多径衰落性能的结论.     

一种改进的非相关多径瑞利衰落信道模型

针对非相关多径瑞利衰落信道,提出了一种改进的基于莱斯正弦和的仿真模型。在原始精确多普勒扩展方法的基础上,对多普勒频率引入了新的旋转角定义,实现了各多径信道的非相关性。理论与仿真分析表明,该方法的自相关和互相关特性与参考模型相比具有极好的吻合性,并且在相同实现条件下,与其他改进型精确多普勒方法相比精度上也有了20%的提高,证实新模型能更准确地描述非相关多径瑞利衰落信道。     

一种新型低复杂度双层分组天线选择算法

针对平坦相关瑞利衰落信道环境下的端到端大规模MIMO系统复杂度过高的问题,提出一种基于离散布谷鸟搜索的低复杂度双层分组天线选择算法。该算法首先基于天线信道相关性对大规模天线阵列进行分组处理,进而利用新型双层算法对分组的天线集合进行优化天线选择。其中,新型双层算法的第一层是每小组天线基于离散布谷鸟搜索的内部选择,第二层是对第一层选择的所有天线利用离散布谷鸟搜索进行最终的选择。提出的新型天线选择算法可有效降低大规模MIMO系统复杂度。仿真结果验证了在平坦相关瑞利衰落信道环境下,提出的天线选择算法能够以较低选择复杂度获得接近最优选择方法的容量性能和较优的BER性能。     

一种改进型的无线信道模型研究

本文引入Clarke参考模型,采取了一种改进型的瑞利衰落信道模型作为单径瑞利衰落信道的仿真模型,并用MATLAB编程仿真实现.该技术有助于对移动通信系统电磁干扰的研究.     

一种无线信道复合衰落模型的分析与仿真

移动通信过程中由于移动设备所处的环境不同,存在不同的信道衰落,从各种衰落模型的相互关系出发,提出了一种移动无线衰落信道混合应用模型。通过实现瑞利衰落分布和对数正态分布,经线性和非线性变换可以得到Nakagami和Suzuki等分布。对提出的复合衰落模型进行仿真,仿真结果符合理论值。该混合衰落模型设计和仿真方法可以用于指导信道模拟器设计和通信系统仿真。     

An efficient simulation of multiple correlated Rayleigh fading envelopes

In order to better assess the performance of wireless communication systems, it is desirable to produce multiple Rayleigh fading envelopes with specified correlations. In this paper, we analyze theoretically a procedure which generates correlated Gaussian random variables from independent Gaussian random variables and give a physical explanation for the limitation of this procedure. Then, based on some uncorrelated Rayleigh fading envelopes, a simple but efficient procedure for generating an arbitrary number of cross-correlated Rayleigh fading envelopes is proposed. Simulation results and computational complexity analysis are presented, which show that the proposed method has some advantages, such as high accuracy, low computational complexity and easy implementation, over the conventional simulation method.     

A novel approach to modeling and efficient simulation offrequency-selective fading radio channels

A multipath radio channel concept based on channel orthogonalization techniques in two inner product spaces is presented and compared to the conventional approach of modeling each individual Rayleigh or Rice fading multipath ray individually. The proposed simulator can be applied to linear amplitude/phase modulation and linear fading channels including Nyquist filtering. It is shown to be a good approximation to the conventional model in the case of tight rolloff factors. Channels having quasi-or truly continuous delay profiles can now be properly represented at significantly reduced computational complexity. The proposed simulation concept leads to the lowest level of complexity being achieved for the prevailing channel and noise conditions on a particular channel     

一种改进的MIMO-OFDM的信道估计算法

针对频率选择性衰落信道下MIMO—OFDM的系统,基于瑞利衰落信道的模型,利用m序列的自相关性,提出了一种基于m序列做梳状导频的多输入多输出正交频分复用最小二乘算法,该算法可以避免对大矩阵求伪逆,以减少计算复杂度,从而提高了信道估计的计算性能。通过对该算法的误码率性能分析和计算复杂度分析,结果表明,相比传统经典最小二乘算法,所提出信道估计算法在中低信噪比下,有效提高了信道估计性能,适合于在实际应用中实现。     

Simplified transmitter design for MIMO systems with channel uncertainty

This article investigates transmitter design in Rayleigh fading multiple input multiple output (MIMO) channels with spatial correlation when there are channel uncertainties caused by a combined effect of channel estimation error and limited feedback. To overcome the high computational complexity of the optimal transmit power allocation, a simple and suboptimal allocation is proposed by exploiting the transmission constraint and differentiating a bound based on Jensen inequality on the channel capacity. The simulation results show that the mutual information corresponding to the proposed power allocation closely approaches the channel capacity corresponding to the optimal one and meanwhile the computational complexity is greatly reduced.     

一种新的多径相关瑞利信道的数学模型：理论分析及仿真比较

产生统计独立的多径相关瑞利信道是无线信道仿真的一个基本问题.Jakes模型得到了广泛应 用,但它在统计独立性方面还存在一些问题.该文提出一种新的相关瑞利信道的数学模型.理论分析和仿真 比较表明它在计算复杂度和统计独立性方面比最初的Jakes模型及其近来发现的改进模型更加简单有效.     

Adaptive equalization and interference cancellation for wirelesscommunication systems

An adaptive equalization and interference cancellation method is proposed. The proposed scheme can cancel both intersymbol interference and cochannel interference, and is blind in the sense that no knowledge of the training sequences of the interfering users is required. In particular, it is a maximum likelihood sequence estimation (MLSE) equalizer that is implemented by the generalized Viterbi algorithm (GVA) with an RLS-based channel estimator. To demonstrate the potential of the proposed method, various simulation results over a frequency selective Rayleigh fading environment in the presence of cochannel interference are presented. In addition, a sequential algorithm is introduced to reduce the computational complexity of GVA     

Model of independent Rayleigh faders

The Jakes (1974) fading model is widely accepted for the simulation of wireless communication channels, but it is very difficult to create a multiple uncorrelated fading waveform. Dent et al. (1993) proposed a modified version of the Jakes model, but it does not solve the problem very well. Li and Huang (2002) also proposed a new model, which overcomes the undesired properties. But its computational complexity is twice as great as that of the Jakes and Dent models. A novel model is proposed. Its correlation properties are as good as those of the Li and Huang model, yet computational complexity is reduced by a half.     

Novel Results on 3G Reconfigurable Outer Block Interleaving Based on FER

Outer block interleaving and time transmission interval (TTI) are two interrelated parameters for the design of 3G systems. Particularly, they represent a critical issue for the implementation of UMTS turbo coding in flat Rayleigh fading channels. Thus, an efficient TTI choice can save computational complexity. In this paper different scenarios are investigated using the maximum UMTS frame length and simulation results are presented for the four possible outer block interleaver configurations in the case of flat Rayleigh fading channel. Considering frame error rate (FER) performance we propose a TTI of 80 ms for rural and urban/suburban outdoor operating environments for the majority of scenarios. For indoor/low range outdoor operating environment 20 ms is the proposed choice apart from low data rates.     

System Capacity Analysis and Antenna Placement Optimization for Downlink Transmission in Distributed Antenna Systems

System capacity and antenna placement play crucial roles in wireless communication systems, and they are of great value to network planning. In this paper, we are motivated to analyze the system capacity and optimize the antenna placement in distributed antenna systems. This paper establishes a composite channel model which takes path loss, lognormal shadowing and Rayleigh fading into consideration. To reduce the computational complexity, an approximate theoretical expression of system capacity is derived with selective transmission at the transmitter and maximal ratio combining at the receiver. An antenna placement optimization problem is formulated, and then a genetic algorithm (GA) based searching scheme is proposed to solve the proposed optimization problem. The computational complexity analysis indicates that the proposed GA-based searching scheme is computationally efficient in terms of both running time and storage space. Numerical results show that the approximate theoretical expression of system capacity can provide a very good approximation to the simulation results, and the proposed GA-based searching scheme for solving the antenna placement optimization problem can consistently offer a large capacity gain over other existing schemes.