An Overview of the Physical Insight and the Various Performance Metrics of Fading Channels in Wireless Communication Systems (original) (raw)
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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.
EURASIP Journal on Wireless Communications and Networking, 2014
In this paper, performance analysis of wireless communication over α − η − μ fading channels has been investigated. First, analysis has been carried out for the case when communication is subjected to the influence of co-channel interference. Closed-form expressions have been derived for the probability density function and cumulative distribution function of the received signal-to-interference ratio. Outage probability has been obtained for this case, in the function of various values of system parameters, and also for the case when selection diversity has been presented at the reception. Further, simultaneous multipath fading and shadowing occurrence has been analyzed, through deriving novel composite Gamma long-time faded α − η − μ fading distribution. First-order statistical parameters have been obtained in closed form, for this novel composite distribution, and capitalizing on them, standard performance measures have been efficiently evaluated, graphically presented and discussed in the function of system parameters.
2013
The mobile radio channel places strong limitations on the performance of wireless communication systems because the transmission principle in wireless communication is more complex than those of the wired networks. In this paper we discuss the radio propagation with an objective to provide an overview of various characteristics of radio channel and an understanding of the process and factors that influences these characteristics. Section I describe a typical outdoor scenario for terrestrial mobile radio channel and principle causes of information loss (multipath fading). Section II presents the various radio channel characteristics like path loss which is used to denote the local average received signal power relative to the transmit power and helps in providing the information on coverage area. Other higher order statistical characteristics such as level crossing rate (lcr) and average duration of fade (adf), which relates the time rate of change of the received signal to the signa...
A Study on Path Loss and Shadowing for Wireless Communication Channels
International Journal of Advanced Research in Computer Science and Electronics Engineering (IJARCSEE), 2019
The demand for accelerated speed, anywhere, and any time connectivity has made wireless communication networks increasingly dense. This has resulted into intense research on how speed of data transfer, security of data, spectrum sharing, and storage of the big data realized can be improved in an efficient way. However the major challenge which has necessitated continuous research progress in the subject is the study of communication path loss and shadowing and how it can be eliminated or lessened to improve the channels involved. This paper will perform experiments on radio propagation models, ray tracing models and perform its simulations in Matlab, as well as provide a review of the various path loss models. The simulation results obtained indicated that when the receiver far away from the transmitter, the signal begins to be weaker and weaker until it is lost. However if the receiver will move away from a closer base station, and while the signal is weakening, it encounters another base station, the two base stations performs a handshake and the signal will start gaining strength.
On the Performance Analyses in Composite Multipath-Shadowed Fading Wireless Channel
The Generic-K distribution is a new flexible statistical model used to describe the composite multipath shadowed fading channels. This three parameter model is versatile enough to represent short term fading such as Rayleigh, Rician or Nakagami-m as well as shadowing. With the aid of Moment Generating Function (MGF) approach and Padé approximation (PA) technique different performance measures such as outage probability and Average bit error rate have been analyzed for a variety of modulation formats. We first use the PA technique to find simple to evaluate closed-form rational expressions for the MGF of output SNR, unlike previously obtained relatively complicated expressions in terms of MeijerG & Whittaker function. Using these simple expressions, we evaluate the performance over single and multi channel receivers under shadowed fading for arbitrary values of fading parameters. Our results are validated through computer simulations which shows perfect match.
On the K and K G Fading Channels
In this paper, the composite Rayleigh-Gamma and Nakagami-Gamma distributions are considered. Multipath short-term fading and long-term fading (shadowing) affect wireless channels. A composite fading model was proposed for the modeling of shadowed channels, which resulted in a closed form solution for the probability density function (pdf). These composite Rayleigh-Gamma and Nakagami-Gamma are well-known as the K-distribution and K G -distribution, and are applied to cases where both micro-and macro-diversity schemes are implemented to mitigate short-term fading and shadowing, respectively. Thus, the composite pdf model offers significant improvement over approaches, which use lognormal pdf for shadowing. The results demonstrate the simplicity and usefulness of the composite pdf in the performance analyses of shadowed fading channels.
Rayleigh fading channels in mobile digital communication systems .I. Characterization
IEEE Communications Magazine, 1997
When the mechanisms of fading channels were first modeled in the 1950s and 1960s, the ideas were primarily applied to over-the-horizon communications covering a wide range of frequency bands. The 3-30 MHz high-frequency (HF) band is used for ionospheric communications, and the 300 MHz-3 GHz ultra-high-frequency (UHF) and 3-30 GHz super-high-frequency (SHF) bands are used for tropospheric scatter. Although the fading effects in a mobile radio system are somewhat different than those in ionospheric and tropospheric channels, the early models are still quite useful to help characterize fading effects in mobile digital communication systems. This tutorial addresses Rayleigh fading primarily in the UHF band. That affects mobile systems such as cellular and personal communication systems (PCS). Part I of the tutorial itemizes the fundamental fading manifestations and types of degradation
Fading Statistics for the Joint Fading and Two Path Shadowing Channel
New expressions for the joint moments, mean, variance and amount of fading (AF) of the Joint Fading and Twopath Shadowing (JFTS) distribution are derived in this letter. The derived expressions for theoretical mean and variance are shown to agree with the experimental results. The AF expression is used for comparing the severity of fading imparted by the JFTS distribution to the fading severity of other common small scale fading and composite fading / shadowing distributions.
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