WIRELESS PROPAGATION CHANNEL (original) (raw)
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PROPAGATION MODELS FOR WIRELESS COMMUNICATION SYSTEM
This paper gives an overview of the propagation models in wireless communication systems. Wireless communication system uses several physical media, ranging from sound to radio to light. These characteristics are affected by the physical environment between the transmitter and receiver. Wireless communication system suffers from various unwanted effects of fading which may be caused due to multipath propagation, path loss, shadowing, Doppler spread and cochannel interference. There are various signal propagation ranges in wireless communication channels.
Propagation Model For Wireless Communications
2012
Wireless technologies have had an enormous impact on networking in recent years. It can create new business opportunities and allow users to communicate and share data in a new fashion. Wireless network decrease installation cost, reduce the deployment time of a network and overcome physical barrier problems inherent in wiring. In this article, we give a presentation of wireless propagation in atmosphere. We discuss in depth the characteristics of propagation. To complement the analysis, we give an account of experiments performed in Matlab-based.
Performance Evaluation of Channel Propagation Models and Developed Model for Mobile Communication
American Journal of Applied Sciences
Propagation models represent a solidifying of mathematical equations and algorithms that are used for radio signal propagation prediction in specific regions. In this research different propagation models are analyzed and compared. These propagation models have been proposed at the operating frequency of 3.8 GHz for different transmitter antenna heights in all types of terrain. These propagation models depend on location, frequency range and clutter type such as urban, suburban and countryside. We have to bear in mind that the results of the path loss estimation of Free Space model are identical and equal to (119 dB) for 18 m and 34 m transmitter antenna heights at 3.8 GHz in urban environment. It is obvious that Egli model shows the highest path loss values in rural environment as compared with the other models. By the end of this paper, a developed empirical radio propagation model is proposed to be appropriate in urban and rural environments.
A good understanding of the wireless channel, its key physical parameters and the modeling issues, lays the foundation for the rest of the book. This is the goal of this chapter. A defining characteristic of the mobile wireless channel is the variations of the channel strength over time and over frequency. The variations can be roughly divided into two types (Figure 2.1): • Large-scale fading, due to path loss of signal as a function of distance and shadowing by large objects such as buildings and hills. This occurs as the mobile moves through a distance of the order of the cell size, and is typically frequency independent. • Small-scale fading, due to the constructive and destructive interference of the multiple signal paths between the transmitter and receiver. This occurs at the spatial scale of the order of the carrier wavelength, and is frequency dependent. We will talk about both types of fading in this chapter, but with more emphasis on the latter. Large-scale fading is more relevant to issues such as cell-site planning. Small-scale multipath fading is more relevant to the design of reliable and efficient communication systems – the focus of this book. We start with the physical modeling of the wireless channel in terms of electromagnetic waves. We then derive an input/output linear time-varying model for the channel, and define some important physical parameters. Finally, we introduce a few statistical models of the channel variation over time and over frequency. 2.1 Physical modeling for wireless channels Wireless channels operate through electromagnetic radiation from the transmitter to the receiver. In principle, one could solve the electromagnetic field equations, in conjunction with the transmitted signal, to find the 10
The performance of any communication system is eventually determined by the medium which the message signal passes through. This medium may be an optical fiber, a hard disk drive of a computer or a wireless link, is referred to as communication channel. There exists a large variety of channels, which may be divided into two groups. If a solid connection exists between transmitter and receiver, the channel is called a wired channel. If this solid connection is missing, this connection is called a wireless channel. Wireless channels differ from wired channels, due to their unreliable behavior compared to wired channels. In wireless channels the state of the channel may change within a very short time span. This random and severe behavior of wireless channels turns communication over such channels into a difficult task. There are several different classifications regarding the wireless channels. Wireless channels may be distinguished by the propagation environment encountered. Many different propagation environments have been identified, such as urban, suburban, indoor, underwater or orbital propagation environments, which differ in various ways. The wireless channel puts fundamental limitations on the performance of wireless communication systems. The transmission path between the receiver and the transmitter can be altered from simple line-of-sight to one that is drastically obstructed by buildings, foliage and mountains. Even the speed of the mobile impacts how rapidly the signal level fades. Modeling the wireless channel has historically been one of the most difficult parts of the communication system design and is typically done in a statistical manner, based on measurements made specifically for a designated communication system or spectrum allocation.
Results in Engineering, 2023
Propagation channel properties influence the development of wireless communication systems. During system design, channel properties are required to choose the suitable air interface (modulation, coding and access scheme). Comparisons and assessment of different solutions are performed using wideband propagation channel models. During network planning, prediction channel models provide valuable inputs to optimize network parameters. This article aims to present a short overview of these different propagation channel models. To cite this article: P.
Fading Characteristics over Wireless Channels
Journal of Engineering and Applied Sciences, 2019
Multipath fading is phenomena that may cause attenuation and distortion to the transmitted signal. The signal transmitted may be diffracted, refracted or reflected over a spread of times from obstacles such as ground, hills, building that are located in the transmission path between the transmitter and receiver sides. Multipath fading, therefore, needs to be taken into consideration when designing wireless radio communication systems. This study presents the key characteristics and simulation modelling for various types of fading channels in the wireless transmission system. Besides, an effort has been made to illustrate the performance comparison of different types of small-scale fading that are subjected to due to multipath delay spread in time and a movement of mobility. The simulations of small-scale fading over the wireless channel that are dependent on Doppler spread and delay spread were determined using communication toolbox in MATLAB.