超宽带频率依赖性信道模型下的PAM和PPM性能比较

在超宽带无线通信中,频率依赖性信道扭曲了发射脉冲波形,影响了通信系统的性能.文章分析此类信道模型下脉冲位置调制和脉冲幅度调制的性能,结果表明,在频率依赖性信道中PAM调制优于PPM调制.     

新的感知无线电信道模型及其容量分析

将新的感知无线电信道模型将交织型信道模型和干扰型信道模型结合在一起,引入开关的概念,将频谱空洞的检测融合在信道中,形成有部分主用户信息的感知无线电双用户信道模型.在这种新的信道模型中,将主用户和感知用户之间的信道看作是一个压缩信道,引入压缩率,感知用户通过一个压缩信道来感知主用户的部分信息.针对新的感知信道模型,分析并计算了相应信道容量.最后,仿真验证了理论模型的有效性和容量优势.     

MIMO信道建模仿真与容量研究

MIMO(多天线输入输出)技术是新一代无线通信系统中的一项关键技术,由于其具有能在不增加带宽与功率的前提下成倍地提高天线系统的容量和频谱效率的优势而受到广泛的关注和研究。但是在实际应用中MIMO技术目前仍有大量的问题亟待解决,而MIMO信道模型在很大程度上影响到MIMO系统的大容量和其他的性能的实现,因此需要建立相应的模型来更好的研究和评估MIMO系统的性能,文中以镜像法与电磁无线传播理论为基础建立MIMO信道的仿真模型,进行编程仿真,得到仿真结果。     

基于降低噪声影响TH-PPM-UWB室外信道估计

为了给适合军事通信的室外超宽带通信技术发展提供技术支持,针对跳时脉冲位置调制超宽带系统的室外信道,提出了一种基于降低噪声影响的信道估计算法。通过仿真,对该算法的性能进行了分析,仿真分析结果表明,该算法有效易行,导频个数越大,估计的值越准确。     

新型无线信道复用方式WSDM及其容量分析

如何进一步高效利用无线电频谱资源,始终是无线通信领域的重要研究课题之一.无线信道统计复用(WS-DM),作为一种新型无线信道复用方式,允许在无线信道上同时同频传送多路信号,从而有效提高无线电频谱的利用效率.首先介绍了基于WSDM技术的无线通信系统,并对其中的关键环节进行了简要分析.其次,运用Shannon信息理论分析了基于WSDM技术的无线通信系统的容量,理论推导得到了信道容量的闭合表达式.计算机仿真结果表明,相对于传统的时分复用(TDM)、频分复用(FDM)等复用方式,WSDM的频带利用率更高,在无线通信中具有更大的优越性.     

基于射线追踪法的月球基地通信信道特性分析

在探月任务中,创建月球基地是一项重要任务。为了满足月球基地获取高清晰度视频和科学数据的高速数据传输需求,以及宇航员和月球探测车等设备支持高容量数据速率通信的需求,需要充分利用太赫兹频段的频谱资源。太赫兹频段的频谱资源相对较为丰富,可以提供更大的带宽和更快的通信速率。本文以LUNA月球基地为研究对象,采用信道建模的方法,对该场景下的太赫兹频段信道特性进行了仿真和分析。通过对该信道特性的评估,为未来的月球基地通信系统方案设计提供链路等方面的性能评估。首先本文对LUNA月球基地的工作模块和居住模块的构造进行了详细的研究。采用了射线追踪法和单刃形衍射模型的混合建模方法,建立了一种适用于月球基地内近距离通信场景的多射线信道模型。最终推导出了适用于该场景链路的信道容量模型。其次本文对LUNA月球基地的工作模块LUNA大厅和居住模块FLEXHab进行了建模,并借助太赫兹信道模拟器CloudRT进行信道仿真。对信道的大尺度衰落特性和小尺度衰落特性进行了分析。最后为了估算信道容量,采用了注水功率和等功率分配两种不同的分配方式。所提出的信道模型可用于评估太赫兹频段月球基地内通信系统的性能,并对月球基地通信系统的建设提供理论依据和参考。     

3G LTE空间信道模型的三维修正及容量分析

空间信道模型SCM(Spatial Channel Model)是3GPP用于LTE系统仿真的MIMO二维信道模型。本文在SCM模型的基础上,综合考虑基站端和移动台端电波的离开角和到达角的三维特性,给出了三维MIMO信道模型的信道参数描述,提升了信道建模的准确度,并推导出该信道模型下包含极化特性的MIMO信道系数表达式。同时探究了天线间距、水平角扩展、俯仰角扩展等对MIMO信道空时相关性的影响。研究结果显示,随着俯仰角扩展从0°到60°增大,散射环境越来越强,信号在空间的色散度越高,不同天线单元接收到的信号之间的相关性越小,信道容量将会越大。     

基于阵列流形分离的多输入多输出信道模型

基于三维阵列流形分离技术,建立了一种天线独立的随机多输入多输出(MIMO)信道模型。将天线阵列的导向矢量进行球谐基函数展开,实现了天线阵列和无线传播环境的分离。对分离出的无线传播环境部分单独进行基于空间相关性的统计建模,得到了一种天线独立的解析MIMO信道模型。所建模型可方便用于MIMO系统性能评估与分析设计。以圆柱阵列和球阵列为例,仿真验证了新模型的正确性和有效性。     

AWGN信道下TH-PPM UWB通信系统性能分析与仿真

首先介绍了TH—PPM UWB信号,然后从理论上对加性高斯白噪声（AWGN）信道下系统的性能进行了分析,包括误码率分析和系统容量分析,最后对系统的误码率和接入用户数进行了仿真比较。结果表明,重复码长度、脉冲重复时间和用户数目的选取对系统的误码率都有较大的影响,同时,系统容量与输出信噪比和数据传输速率有关并趋于定值。     

无线激光通信类脉冲位置调制性能比较

为了比较各种类脉冲位置调制性能,对类脉冲位置调制的编码结构、平均发射功率、带宽需求、传信率、功率谱密度、信道容量等进行了比较,分析了其性能特点及使用场合.结果表明,开关键控调制方式容易实现,但功率利用率低;脉冲位置调制方式提高了功率利用率,但是带宽效率差,同时需要符号同步;数字脉冲间隔调制结构复杂,缩短了符号长度,带宽效率高,不需要符号同步;双头脉冲间隔调制方式提高了带宽效率和传输容量,不需要符号同步,大大简化系统实现复杂度.     

Channel model for wireless communication around human body

A channel model for a wireless body area network at 400 MHz, 900 MHz and 2.4 GHz is derived. The electromagnetic wave propagation around the body is simulated with a finite-difference time-domain simulator. Creeping waves were identified as the propagation path around the body. Its impact on the delay spread in an indoor environment is discussed.     

Channel model for simultaneous backhaul and access for mmWave 5G outdoor street canyon channel

Wireless Networks - Millimeter waves (mmWaves) with very wide frequency bands are proposed for 5G new radio to deliver higher data-speed and capacity. Transmission using mmWaves suffers significant...     

Path-loss model for broadcasting applications and outdoor communication systems in the VHF and UHF bands

A simple propagation model for the VHF and UHF bands is presented. The model is a computational form of the data provided by the FCC F(50,50) propagation curves, and it is aimed to be used by practicing engineers. It allows the estimation of median path loss, received power or electrical field strength which usually is sufficient in many practical applications. The model is independent of frequency and is applicable to outdoor environments in a range of distances from 0.5 miles (800 m) up to 40 miles (64.36 km) and transmitting antenna heights from 100 ft (30.48 m) up to 2000 ft (609.6 m), and is based on a receiving antenna height of 30 ft (9 m).     

Channel capacity of the distributed MIMO relay in visible light communication systems

Visible light communication (VLC) is a novel paradigm that uses light-emitting diode (LED) light as an information carrier and has several advantages over radio-frequency communication in terms of the bandwidth, security and multi-path fading. When the VLC system is considered in an indoor environment, LED lamps, which are placed at the ceiling to provide ambient light, can offer rich spatial resources for VLC as distributed intermediate relaying terminals. This paper introduces a novel distributed multiple-input multiple-output (D-MIMO)-relaying VLC scheme and analyzes its communication performance. Using the sum rate of the broadcasting and multiple access relay channels, a tight upper bound on the channel capacity was derived. The numerical results showed that the D-MIMO-relaying VLC scheme outperformed the direct-path-based scheme in terms of the channel capacity. For a given indoor environment, the capacity of D-MIMO-relaying VLC can be improved further by selecting the appropriate relay parameters, such as the number of LED–PD pairs in a relay, distance between relays and height of relays.     

Channel model and capacity for broadband indoor MIMO-WLAN systems based on measurements at 2.4 GHz

This article provides a channel model which is suited for broadband indoor WLAN (wireless local area network) applications. Especially the communication within one room is addressed. These applications are characterized by no or very slow movements of the terminal in conjunction with high data rates requiring high bandwidths for transmission. Present WLAN systems offer data rates up to 108 Mb/s, multiple antenna systems (MIMO systems) are at the beginning of their introduction into the market. Upcoming demand for even higher data rates necessitating higher bandwidth efficiency is almost sure. This requires at first hand a full understanding of the channel in order to make best use of it. The article shows that the channel can be described best by a deterministic model, which needs only few dominant paths. This is underlined by channel sounder measurements and simple calculations. Making use of this deterministic channel model the article shows capacity improvements over a widespread Rayleigh fading model assumption.     

Channel and capacity estimation errors

Systems with multiple element transmitter and receiver arrays have been shown to achieve very high spectral efficiencies. The theoretically achievable Shannon capacity is a function of the channel between the transmitters and the receivers. On the simulation level, one assumes certain statistical characteristics for the channel, but on a practical level, the actual channel is measured. We show that the accuracy of the measurements affects the accuracy of the capacity estimation when using the Shannon formula. We study analytically how the channel estimation error appears in the capacity formula, and we derive mathematical expressions for the first- and second-order approximations of the error. We also present simulation results that show the effect of the system size, the measurement accuracy, the system signal-to-noise ratio and the nature of the channel itself on the accuracy of the estimation of the channel capacity.     

分布式MIMO系统信道容量分析

首先推导了分布式MIMO点对点链路遍历信道容量的近似表达式或理论下界,然后给出小区平均遍历容量的表达式.在此基础上,研究D-MIMO与C-MIMO系统分别在BT和ST两种天线选择机制下的平均遍历容量.最后通过仿真,证明了所推导理论表达式的正确性,同时比较了两种MIMO系统的信道容量.     

Channel capacity and state estimation for state-dependent Gaussian channels

We formulate a problem of state information transmission over a state-dependent channel with states known at the transmitter. In particular, we solve a problem of minimizing the mean-squared channel state estimation error E/spl par/S/sup n/ - S/spl circ//sup n//spl par/ for a state-dependent additive Gaussian channel Y/sup n/ = X/sup n/ + S/sup n/ + Z/sup n/ with an independent and identically distributed (i.i.d.) Gaussian state sequence S/sup n/ = (S/sub 1/, ..., S/sub n/) known at the transmitter and an unknown i.i.d. additive Gaussian noise Z/sup n/. We show that a simple technique of direct state amplification (i.e., X/sup n/ = /spl alpha/S/sup n/), where the transmitter uses its entire power budget to amplify the channel state, yields the minimum mean-squared state estimation error. This same channel can also be used to send additional independent information at the expense of a higher channel state estimation error. We characterize the optimal tradeoff between the rate R of the independent information that can be reliably transmitted and the mean-squared state estimation error D. We show that any optimal (R, D) tradeoff pair can be achieved via a simple power-sharing technique, whereby the transmitter power is appropriately allocated between pure information transmission and state amplification.     

E波段微波通信系统中信道估计技术

针对E波段微波通信系统单载波块传输特性以及采用的帧结构,在MATLAB平台下仿真分析了LS信道估计、MMSE信道估计以及基于DFT的信道估计的MSE性能。理论分析和仿真结果表明,三种信道估计技术各有其优势,在中低信噪比时可以实现较好的系统误符号率性能。     

Channel capacity of fading channels for differentially encodedtransmission

The capacity of flat fading channels when applying differential encoding with noncoherent reception and no channel state information available at the receiver is considered. Numerical results indicate the gains achievable by multiple symbol detection in the case of slowly time-varying channels and provide a comparison between schemes with different potential bandwidth efficiencies