Questions tagged [fading-channel]

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How to add Rayleigh Fading Coefficient to a BPSK signal with AWGN?

I have a problem with my code. I saw many programs that add the coefficients of rayleigh like this: h=1/sqrt(2)*(randn(1,N)+1i*randn(1,N)), where N=number of bits. ...
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1answer
64 views

bit reversed order of FFT matrix for channel estimation

Although the question seems similar to this one HERE, but what I want to ask about is little bit different. Assume we have a signal $X$ whose length is $N$x$1$, we convert that signal into time ...
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12 views

FWGN model and MATLAB implementation

I am studying channel modeling, at the moment, in the book: "MIMO-OFDM wireless communications with MATLAB", the explanation about the model is as follow: The code for generation of Doppler ...
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1answer
22 views

How is channel frequency response/channel state information related to free space path loss?

As we know, the path loss can be described by the equation as $$ \frac{P_{r}}{P_{t}}=D_{t} D_{r}\left(\frac{\lambda}{4 \pi d}\right)^{2} $$ In the OFDM system, such as Wi-Fi, there are infinite paths ...
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12 views

Simulating Rayleigh channel - Problem with adding channel coefficents

I am currently trying to simulate a Rayleigh channel using python (numpy). Full Jupyter Notebook on GitHub: Jupyter Notebook I assume that the channel changes with each new symbol. So I create myself ...
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41 views

About discrete time model for wireless channel

I am trying to understand Section 2.2.3 of the book "Fundamentals of wireless communication" by Tse and Viswanath. In this section the authors explain how to go from the continuous time ...
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30 views

Received signal's power under Raleigh fading

I am trying to understand how to calculate the power of a received signal under Raleigh fading. What I gather is that the Rayleigh fading is a complex Gaussian random variable and that the multipath ...
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71 views

Zero padding OFDM equalization

In ZP-OFDM, The convolution is linear. it's different from CP-OFDM which is circular convolution leading to have one tap equalizer in frequency domain. if I have a ZP-OFDM system, and we have a signal ...
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102 views

Fast/Slow Fading: How are doppler shift and coherence time related?

In the literature I've read that fast fading happens if the bit duration is larger than the coherence time of the channel. The coherence time of a channel is proportional to $\frac{1}{f_{Doppler}}$. ...
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1answer
45 views

Non Coherent BPSK with no Channel State Information at the receiver

Where or what is the proof for the failure of BPSK in fading channel when we have no knowledge of the fading coefficient $h$ at the receiver in the equation $y=hx+w$, where $x$ is BPSK symbol equally ...
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77 views

Compressive sensing based sparse vector estimation

I am newbie in compressive sensing (CS), I read about compressive sensing and its use for sparse vector estimation. As I understood CS can be used either in time or frequency domain. For me, The part ...
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29 views

SNR in case of complex channel and fading

I am trying to estimate SNR mathematically given in a paper. $$ y = hx + n$$ $h$ is channel fading, that is Rayleigh in my case, while $n$. Both $h$ and $n$ are random variables. ...
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1answer
30 views

Correlated fading channel: transmit and receive antenna correlation matrices

I am trying to create a non-i.i.d channel: correlated Rayleigh fading channel. $$ H= R_H \cdot H_o,$$ where $H_o$ is i.i.d. channel ( uncorrelated) and $ R_H$ is a channel correlation matrix, is ...
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93 views

Degrees of freedom in coding (for a communication channel)

I was reading on my lecture slides about how to achieve diversity (i.e. transmit more copies of the same message in order to avoid its corruption; this technique may be realized by repeating the ...
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1answer
29 views

Rayleigh fading channel as a scalar quantity [closed]

In most cases rayleigh channel is a vector. can a rayleigh channel be a scalar quantity i.e., can we have only one element in rayleigh fading channel.
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1answer
39 views

Is time varying channels same as circulary symmetric complex gaussian?

From the literature i understood that if the channel is non time varying then we can consider it as circularly symmetric complex gaussian distributed. So can we consider the same if the channel is ...
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36 views

Gain and average gain of two-path channel

For two-path channel with no loss or phase shift in the reflection, Why the gain of the channel at radio frequency less than average gain of the channel?
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1answer
32 views

Hf ionospheric channel model for large bandwidth

I know some models like the Watterson model for HF ionospheric channels but those are limited to narrow band frequencies. Are there some models to bandwidth like 12kHz up to 24 kHz?
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45 views

Detect orthogonal sequence with fading

For a set of $N$ orthogonal sequences $\textbf{A}^i = \{a_1^i,a_2^i,...,a_M^i\}, i =1 ..N$, the detection of these sequences can be done by calculating the inner product (dot product) of receive ...
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71 views

Is MMSE equalizer necessary?

For observation $y$, channel coefficient $h$ and gaussian noise $w \sim \mathcal{CN}(0,\sigma^2)$, $$y = hx + w \tag{1}$$ Note that for OFDM system, (1) is assumed channel input-ouput equation on ...
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2answers
81 views

Meaning: channel unknown and known at the transmiiter

What does "channel unknown" and "known at the transmitter" mean? In books about signal processing, it has always mentioned it if capacity or transmission (estimation) is discussed. I can't understand ...
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38 views

Why are the following two packet reception probabilities different?

https://www3.nd.edu/~mhaenggi/pubs/broadnets04.pdf In 3 page of this paper, the packet reception probability without interference is $e^{-\theta N Ad^2/ P}$. $\theta$ is sinr threshold. $N$ is a ...
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23 views

why if I want to create a rayleigh fading channel with $E[|H_{i,j}|^2]$,I should multiply $\sqrt{\frac{1}{N_R \times N_T}}$?

I want to create a rayleigh fading channel,and my classmate told me that I can create an $N_R \times N_T $ channel $\mathbf H$ with $E[|H_{i,j}|^2]$,that is,$\sqrt{\frac{1}{N_R \times N_T}}\times CN(0,...
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1answer
24 views

Small Scale Fading time varying or position varying

I would like to ask how small scale fading can affect a transmission with time. The particular system is an antenna transmitting an ASK modulated signal at 915MHz and with bandwidth between 200KHz to ...
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1answer
50 views

Notes or books to quickly get started on the basics of signal processing or wireless communication

I'll soon start working in signal processing, specially wireless communication systems. Hence I'd like to get a quick understanding of MIMO and related systems, for example, the topics like: 1) where ...
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56 views

Two different models of Rician fading

The amplitude of the signal in Rician fading case is characterized by the Rician distribution (let's call this model 1). However, the received power in Rician fading is sometimes modelled as (model 2)...
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1answer
1k views

channel gain calculation

I want to calculate the SINR term in an up-link of wireless communication system but there is different models for simulation. I want to know what is the exact meaning of $|h|^2$ in this formula: $\...
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1answer
35 views

Detecting multi-path propagation when one acoustic signal is dominant

I am sending an acoustic signal from a source to a receiver where there are limited number of paths the signal can travel. I want to detect if there has been multipath propagation or not when one path ...
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1answer
38 views

Assessing relative wireless channel quality using Capacity and Condition Number CDFs

I have Channel capacity analysis figures for two wireless channels show below: My question: While ergodic capacity in the first subplots are very clear in conveying the channel capacity, How to make ...
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1answer
165 views

Validating Jakes model in Rayleigh Fading channels

I am trying to validate the Jakes model by comparing the autocorrelation function given by $ \rho(\Delta t ) = J_{0}(2 \pi f_{d} \Delta t)$, where $ f_{d} $ is the maximum Doppler shift, $ J_{0} $ is ...
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1answer
49 views

What's the effect of spread spectrum on frequency- selective channel

In brief, we consider the channel as frequency-selective channel if the frequency of the signal is larger than then frequency of channel. So, does using the spreading spectrum change the frequency-...
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3answers
303 views

Explanation a flat fading channel in case MIMO OFDM

I am trying to understand flat fading and frequency selective channels. As I understood, in the case of flat fading channels MIMO channel elements, $h_{i,j}$, are random variables. Which assumption ...
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2answers
552 views

BER of QPSK modulation in Rayleigh fading channel model

i am having trouble deriving a BER analytical expression for QPSK modulation system operating in a Rayleigh Fading channel model. Could anyone direct me to a reference that would help in this matter. ...
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25 views

Channel models for wireless body area networks

To transmit a signal over wireless body area network, the signal is transmitted over a fading channel with additive white Gaussian noise. The channel model can be obtained from the IEEE standards. My ...
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1answer
630 views

Channel model: LOS Component and Rician K-factor

I am asking about Rician K- Factor in this model: I know that if $K=0$ then it is a pure Rayleigh fading, if $K= \infty$, then non fading Channel. What is it, if $0<K<\infty$ ? If i represet ...
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1answer
78 views

Channel estimation

In single-carrier systems, at the receiver, when we need to do channel estimation and equalization? Do we need to do before timing synchronization and CFO correction or before it? And, please let me ...
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1answer
47 views

Designing Rayleigh Fading Wireless Channel with particular properties [closed]

I have some information on particular wireless channel between an Access Point(AP) and K users as described in the picture below: How i can create this channel in Matlab?
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2answers
503 views

How to find the instantanous SNR over Fading channel

I would like to prove that the instantnous SNR of flat fading channel $$y=hx+n$$ is $$\gamma=\frac{|h|^2}{N_0}P$$ where $E\{z\}$ is the expectation of $z$ and $$ E\{x\}=P $$ $$ E\{n\}=0 $$ $$ E\{...
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1answer
92 views

channel estimation for cdma

I am looking for a method to make a multi-user channel estimation with CDMA. Here is my question: Is there a way to estimate multi-user channels with their spreading codes? If yes, what is the ...
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2answers
158 views

Digital communication BER performance

I've searched for the theoretical equations of bit error rate over Rayleigh flat fading channel basically for binary phase shift key and 16-Quadrature modulation but i didn't find them, could any one ...
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1answer
52 views

Questions about reproducing results of a paper on Communication Systems and Wireless Communication

I'm trying to reproduce the results of a paper on Device-to-Device Communication, channel assignment and mode selection (G. Yu, L. Xu, D. Feng, R. Yin, G. Y. Li and Y. Jiang, "Joint Mode Selection and ...
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32 views

Is it safe to call this WSSUS channel a Gaussian process?

BACKGROUND: Equation (3.6) of Wireless Communications by Goldsmith gives the baseband impulse response of a time-varying channel as: $$ c(\tau,t) = \sum_{n=0}^{N(t)}\alpha_n(t)e^{-j\phi_n(t)}\delta(\...
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76 views

CDF of product of two *translated* exponential variables

It is known that the CDF of the product of two exponential random variables is given by this answer If $X$ and $Y$ have rate parameters $\mu$ and $\lambda$, so their pdf's are $f_X(x) = \mu e^{-\...
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2answers
2k views

How to compute the channel gain from the path loss model of a wireless channel

I did my research but I did not get a satisfying answer. We have a transmitter and a receiver over a wireless communication channel. The channel's path loss is modeled as $ 128 + 37 \log_{10} (d)$, ...
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1answer
768 views

How can I generate time-variant Rayleigh channel in MATLAB

One of known models for channel simulation is called Rayleigh Fading channel, it's usually used to simulate wireless channel in time variant/invariant. As I know, Rayleigh fading channel can be ...
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1answer
50 views

Need information about following channel model

The following research paper is for blind channel equalization and the author has modeled the channel as 7 tap weights https://ieeexplore.ieee.org/document/1096877 On page 3 it has shown the ...
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1answer
116 views

What's the difference between SISO and SIMO in using matched Filters

Suppose we are transmitting a signal $x$ in $OFDM$ with $N$ subcarriers, After performing Parallel/Serial conversion and then N-points FFT, we suppose to have signal $s = IFFT^Hx$, Then adding the ...
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1answer
80 views

When to use Rician fading vs Gain for Directional Antenna

This is a pretty simple question. [The answer might not be simple :( ] If I am using a directional antenna, can I used Antenna gain $G_T=1$ as I am considering Rician Fading between transmitter and ...
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1answer
76 views

Is the Channel shortening similar to Time domain Equalizer (TEQ)

I used to read about Time domain equalizer (TEQ) in many lectures, i.e here , But in many other papers, that's called Channel shortening i.e here . However, in the a two above links, the cost ...
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1answer
1k views

Rayleigh fading with frequency selective fading channel

I Read in one reference that, the Rayleigh distribution is commonly used to describe the statistical time varying nature of the received envelope of a flat fading signal, or the envelope of an ...