Channel estimation in narrowband wireless communication systems

Channel estimation is an integral part of standard adaptive receiver designs used in narrowband, digital wireless communication systems. In this tutorial paper, commonly used approaches to channel estimation are reviewed. Both time‐invariant and time‐varying channels are considered. For time‐varying channels, both pilot symbol interpolation and data‐directed channel tracking are considered. Applications include the Global System for Mobile communications, the Enhanced Data rates for Global Evolution system, and another Time‐Division Multiple‐Access system known as Telecommunications Industry Association/Electronics Industry Association/Interim Standard—136 (TIA/EIA/IS‐136 or IS‐136). Copyright © 2001 John Wiley & Sons, Ltd.     

下一代移动通信系统中的信道分配策略

下一代移动通信系统是一个由微蜂窝、宏蜂窝和卫星小区构成的多层覆盖体系结构,在该体系结构中,多媒体业务将占有很大的比重。基于这一特点,建立新的通信系统模型, 并通过将软-通信质量概念与统计复用技术相结合,获得了一种较好的信道分配方法。通过对算法进行系统仿真,比较了它与传统信道分配算法的优劣。仿真结果表明:新的信道分配方法会增加系统容量,减少通信业务阻塞概率,极大的提高整个系统的性能。     

A human body model for efficient numerical characterization of UWB signal propagation in wireless body area networks

Wireless body area network (WBAN) is a new enabling system with promising applications in areas such as remote health monitoring and interpersonal communication. Reliable and optimum design of a WBAN system relies on a good understanding and in-depth studies of the wave propagation around a human body. However, the human body is a very complex structure and is computationally demanding to model. This paper aims to investigate the effects of the numerical model's structure complexity and feature details on the simulation results. Depending on the application, a simplified numerical model that meets desired simulation accuracy can be employed for efficient simulations. Measurements of ultra wideband (UWB) signal propagation along a human arm are performed and compared to the simulation results obtained with numerical arm models of different complexity levels. The influence of the arm shape and size, as well as tissue composition and complexity is investigated.     

无线光通信光功率衰减模型分析

现有的无线光通信系统中,光功率衰减模型普遍采用的是平面波假设下的模型,而实际无线光通信系统发射的激光是高斯光束。因此,建立高斯光束下的光功率衰减模型更加符合实际情况。利用理论推导结合仿真的方法,分析了高斯光束下发射光功率计算中积分限的选取,在综合考虑精确性和简易性的原则下,建立了高斯光束的光功率衰减模型,并以此为基础,比较了平面波和高斯光束下的光功率衰减模型,研究了平面波近似带来的误差。结果表明:两种模型明显不同,平面波假设下的模型会低估无线光通信系统的性能,在分析最大可通信距离时会带来12%~13%的相对误差。     

Channel model for satellite indoor communication,system design

In this paper the development of a channel model for wireless indoor communication, specifically with regard to indoor retransmission of satellite signals and reception by fixed and portable receivers in the L band, is described. The study is confined to the channel model, though it does not include the assessment of particular transmission forms. The theories and approaches used in the model are mainly derived from the field of mobile communication. They are combined to a straightforward chain from large- to small-scale variations yielding information about the several stages of fading. One of the features is the evaluation of the complex field distribution across a local area that can be transformed into a time-varying fading when assuming a moving receiver or a non-stationary environment. © 1998 John Wiley & Sons, Ltd.     

An attempt to model the human body as a communication channel

Using the human body as a transmission medium for electrical signals offers novel data communication in biomedical monitoring systems. In this paper, galvanic coupling is presented as a promising approach for wireless intra-body communication between on-body sensors. The human body is characterized as a transmission medium for electrical current by means of numerical simulations and measurements. Properties of dedicated tissue layers and geometrical body variations are investigated, and different electrodes are compared. The new intra-body communication technology has shown its feasibility in clinical trials. Excellent transmission was achieved between locations on the thorax with a typical signal-to-noise ratio (SNR) of 20 dB while the attenuation increased along the extremities.     

Path loss model for wireless narrowband communication above flat phantom

A new empirical path loss model for wireless communication at 2.4 GHz above a flat, lossy medium, representing human tissue, is presented. The model is valid for dipole antennas for heights up to 5 cm above the phantom and for distances up to 40 cm, and was applied to muscle and brain simulating media. For antennas placed close to the lossy medium, it was found that antenna height has a major influence on path loss. The model has been validated by measurements and simulations, which show excellent agreement     

UWB-IR室外通信信道模型及其容量近似求解

针对几公里范围的军事通信,在经验测试数据的基础上建立了的超宽带冲激无线电(UWB-IR)室外通信的信道模型,通过仿真对在该模型条件下通信系统的误码性能进行了分析,并利用化简和近似求解的方法,对其容量进行了分析和计算.     

Multi-objective optimization framework complying IEEE 802.15.6 communication standards for wireless body area networks

Wireless Networks - Wireless body area network (WBAN) routing protocols are primarily designed for improvement of network performance parameters such as network lifetime, throughput and latency....     

无线移动信道的仿真模型分析

通过对无线移动信道衰落特性的分析，建立了数学模型和计算机仿真模型，并对计算机仿真结果进行了分析，得出了相应结论。     

无线通信的跨层优化

传统的OSI分层结构无法适应无线网络环境，随着越来越多无线应用的出现，人们提出了跨层设计，其主要内容就是通过在协议栈的各层之间（主要是应用层、传输层、网络层、链路层和物理层）传递特定的信息，使协议栈能够根据无线环境的变化来实现对资源的自适应优化配置，从而更有效的利用无线网络资源，提高系统的性能。     

Spatio-temporal coding for wireless communication

Multipath signal propagation has long been viewed as an impairment to reliable communication in wireless channels. This paper shows that the presence of multipath greatly improves achievable data rate if the appropriate communication structure is employed. A compact model is developed for the multiple-input multiple-output (MIMO) dispersive spatially selective wireless communication channel. The multivariate information capacity is analyzed. For high signal-to-noise ratio (SNR) conditions, the MIMO channel can exhibit a capacity slope in bits per decibel of power increase that is proportional to the minimum of the number multipath components, the number of input antennas, or the number of output antennas. This desirable result is contrasted with the lower capacity slope of the well-studied case with multiple antennas at only one side of the radio link. A spatio-temporal vector-coding (STVC) communication structure is suggested as a means for achieving MIMO channel capacity. The complexity of STVC motivates a more practical reduced-complexity discrete matrix multitone (DMMT) space-frequency coding approach. Both of these structures are shown to be asymptotically optimum. An adaptive-lattice trellis-coding technique is suggested as a method for coding across the space and frequency dimensions that exist in the DMMT channel. Experimental examples that support the theoretical results are presented     

无线OFDM系统传输信道模型化参数检测

利用导频子载波时频相位相关性统计检测与QAM信号解映射判决误差统计，提出了一种适用于频域导频无线OFDM系统的传输信道模型化参数检测方案，包括信道最大多径时延、最大多普勒频率和信噪比检测；能够有效解决传统的OFDM信道估计算法通常按照最恶劣信道情况上限进行设计，以及基于MMSE准则最优信道估计器中信道先验信息统计运算复杂度高的缺陷；仿真结果表明，在低复杂度条件下可以有效获知当前传输信道模型参数的近似统计信息。     

室内无线通信系统的路径损耗模型研究

随着移动通信技术的蓬勃发展,室内无线通信也得到了广泛的应用,然而,室内环境的复杂性和多变性,也为室内无线通信技术的发展和普及带来了许多挑战。信号在传输时,要受到反射、绕射、散射、多径传播等多种因素的影响,这给研究无线信道带来很多困难,因此建立路径损耗模对于研究室内通信系统的特性十分必要。无线信道的路径损耗模型包括位置通用模型(像ITU模型,WINNER模型等)和位置专用模型(像d1-d2模型,Supachai Phaiboon模型等),文章将会对这两类模型分别进行分析。     

A physical model of the wireless infrared communication channel

A simple analytical model of the wireless infrared communication channel in indoor environments is presented. The infrared signal is modeled as the combination of a diffuse component and a line-of-sight (LOS) or direct component. For the diffuse component alone, the properties of the channel are found using Ulbricht's integrating sphere. When a LOS component is also present, the transfer function depends upon the Rician factor K given by the ratio of the electrical power in the LOS and diffuse signals after the detector. For small K, the transfer function shows notches down to low frequencies, but due to the nature of light never for zero frequency. We confirm that a K-factor ⩾13 dB is required also in infrared wireless links in order to support distortionless data transmission beyond 100 Mbit/s. Increasing the directivity at the receiver and/or at the transmitter improves the effective value of K. Here, we show that a moderate directivity will be sufficient for high-speed infrared communication in typical indoor scenarios     

Network coding for wireless communication networks

This special issue includes a collection of 19 outstanding research papers which cover a diversity of topics on the application of network coding in wireless communication networks.     

Quantum communication for wireless wide-area networks

In this paper, a quantum routing mechanism is proposed to teleport a quantum state from one quantum device to another wirelessly even though these two devices do not share EPR pairs mutually. This results in the proposed quantum routing mechanism that can be used to construct the quantum wireless networks. In terms of time complexity, the proposed mechanism transports a quantum bit in time almost the same as the quantum teleportation does regardless of the number of hops between the source and destination. From this point of view, the quantum routing mechanism is close to optimal in data transmission time. In addition, in order to realize the wireless communication in the quantum domain, a hierarchical network architecture and its corresponding communication protocol are developed. Based on these network components, a scalable quantum wireless communication can be achieved.     

Traffic models for wireless communication networks

Introduces a deterministic fluid model and two stochastic traffic models for wireless networks. The setting is a highway with multiple entrances and exits. Vehicles are classified as calling or noncalling, depending upon whether or not they have calls in progress. The main interest is in the calling vehicles; but noncalling vehicles are important because they can become calling vehicles if they initiate (place or receive) a call. The deterministic model ignores the behavior of individual vehicles and treats them as a continuous fluid, whereas the stochastic traffic models consider the random behavior of each vehicle. However, all three models use the same two coupled partial differential equations (PDEs) or ordinary differential equations (ODEs) to describe the evolution of the system. The call density and call handoff rate (or their expected values in the stochastic models) are readily computable by solving these equations. Since no capacity constraints are imposed in the models, these computed quantities can be regarded as offered traffic loads. The models complement each other, because the fluid model can be extended to include additional features such as capacity constraints and the interdependence between velocity and vehicular density, while the stochastic traffic model can provide probability distributions. Numerical examples are presented to illustrate how the models can be used to investigate various aspects of time and space dynamics in wireless networks     

Propagation modelling for indoor wireless communication

It is important to characterise the indoor radio propagation channel to ensure satisfactory performance of a wireless communication system. Site measurements can be costly; propagation models have been developed as a suitable low-cost alternative. The existing models can be classified into two major classes: statistical models and site-specific propagation models. Statistical models rely on measurement data; site-specific propagation models are based on electromagnetic wave propagation theory. The ray-tracing technique is very useful in site-specific propagation modelling. This paper gives an overview of indoor propagation modelling and concentrates on a discussion of the ray-tracing modelling technique because of its practical appeal and its applicability to any environment