10 votes
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Flat fading criterion of OFDM subcarrier spacing

Your mathematical derivation is correct, your $H[k]$ is the single-tap equalizer (i.e. one tap for each subcarrier, and the subcarriers do not mix with each other. That's the orthogonal in OFDM). ...
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7 votes
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Educational purpose - What is the correct way to simulate a multipath fading channel which has ISI

Lets say we want to transmit a sequence of discrete data $\left\lbrace x[n] \right\rbrace$. But because we are living in analog world, the sequence must be modulated. Call $T_s$ is symbol duration ...
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7 votes

Practicality of the assumption of i.i.d. for Rayleigh channels

I am a little late but I post my answer anyway so that someone having the same question will find it interesting and discuss. The discrete baseband multipath channel can be modeled as a FIR, i.e. $$...
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6 votes

OFDM intra-block multipath interference

By using cyclic prefix and its associated demodulation techniques, LTE OFDM (nearly) eliminates the inter-symbol inteference (ISI). The intra-block inteference, if I understand well your question, ...
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5 votes
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Correct way to simulate Rayleigh fading for indoor environments

A discrete-time baseband model of a multi-propagation channel can be written as $$y[m] = \sum_l h_l[m] x[m-l] + w[m]$$ where $l$ is the index of channel taps if the channel is modeled as a FIR $\{...
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4 votes
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Transmitting over Unknown Fading Channel

The strategy depends heavily your "realistic scenario", e.g. which estimator, which equalizer, which estimation error, etc. In general scenario, you cannot trust the estimate of $h$, it means that ...
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4 votes

Why do we express complex noise as Gaussian distributed while the channel is Rayleigh distributed?

There are too many things named after Rayleigh floating around in this problem. Consider first additive white Gaussian noise with two-sided power spectral density $\frac{N_0}{2}$. This is generally ...
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4 votes

Rayleigh Fading Simulation

Your approach will not model the actual channel but can be used to create the received waveform as having passed through a Rayleigh fading channel. I describe considerations to actually create the ...
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4 votes
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Matlab: Difference between flat fading and Rayleigh multipath fading, terminologies and concept

The fundamental idea to keep in mind is that in a wireless channels with reflections, if you transmit $s(t),$ you'll receive $$r(t)=\sum_{i=1}^Na_is(t-\tau_i).$$ Another important idea is that ...
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4 votes

Why exponential decay power delay profiles are used to model fading?

While it is correct that discrete-time channel tap is usually modeled as circularly symmetric Gaussian, having power being exponentially distributed (see this answer and the cited book therein for the ...
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3 votes
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Question about path loss exponent estimation from measurment

The path loss exponent does not depend on the reference distance. There are two mistakes in your path loss formula. First, path loss does not include the gains of transmit or receive antennas. Second, ...
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3 votes
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Matlab: Correct method of generating Rayleigh fading channel

Question 1: Yes, it is a multipath Rayleigh Channel with $ 1000 $ taps. You need to know that when you generate complex coefficients, and the real part and the imaginary part of this coefficients ...
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3 votes
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what does mean quasi-static channel

Quasi-static is almost-static. In other words, for a block (or window) period of time, you could assume that your channel is static. Below, i attach a figure that depicts this scenario. As you can see ...
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3 votes
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Rayleigh fading with frequency selective fading channel

First it is useful to understand what a Rayleigh and Ricean distribution is, and then we can more easily see how that statistic can be used to describe certain fading channels. A zero-mean complex ...
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3 votes

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

To answer the literal questions you asked: yes see above To Frame Challenge your question and give you what you were probably looking for: The path loss equation you cited: $$ 128+37\log_{10}(d) ,...
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3 votes
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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 No offense, but that ought to win the prize for the least-...
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2 votes

Flat fading criterion of OFDM subcarrier spacing

There's a lot of very valid aspects that you touch, but from what I've learned (and experienced having fun with OFDM SDR transceivers), the main reasoning to do OFDM is having a narrow-channel ...
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2 votes

Channel modelling for wireless body area network

IEEE 802.15.4a defines multiple bands from 2.4 to 10 GHz for operation. You should focus on one. Not sure you're actually looking for diffraction and not more for backscatter from surrounding objects ...
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2 votes
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Brief introduction to wireless communication and communication terminologies

Well, these are very fundamental questions, and I think they are written in any good book. But maybe it's hard to extract the exact information from them, which you ask for. So, let me briefly answer: ...
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2 votes
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MIMO System Model in Matlab

In a wireless system, most of the noise is added by the receiver itself. The received signal is very weak (-100 dB or less is typical), and its power is comparable to the thermal noise of the receiver'...
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2 votes
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why did convolution coding achieve BER less than Reed-Solomon?

Reed-Solomon codes are good for correcting bursts of errors (such as those that often occur in computer memory systems such as RAM, or on less volatile media such as CDs and DVDs) or at the output of ...
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2 votes

Correct way to simulate Rayleigh fading for indoor environments

Your question is quite unclear, but it seems like you're trying to simulate the continuous-time radio channel. In this model, you do not multiply by complex coefficients; rather, you add delayed and ...
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2 votes

Cyclic prefix length in baseband OFDM with ZF equalizer

The channel which you have created is having 4-Taps and all taps are one after the other, meaning roughly there are 4 multi-paths and they are very close to each other. How close depends on what is ...
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2 votes

what does mean quasi-static channel

Quasi-static channels can be said as "block-wise" time (in)variant. For example, your channel has no variations over time (not in delay domain) for some time-period, e.g., 1 ms, but the channel may ...
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2 votes

Intersymbol interference due to limited channel bandwidth

Here is a graphic I have that demonstrates ISI due to multipath propogation: Notice the eye diagram in the upper right hand corner showing what we should receive if there was no ISI, or other noise ...
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2 votes
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Is the Channel shortening similar to Time domain Equalizer (TEQ)

Most likely people use different words to describe the same concept. This happens quite often. The TEQ is the more general term and also used to equalize other methods that OFDM, while CS is related ...
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  • 1,046
2 votes
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How can I generate time-variant Rayleigh channel in MATLAB

Yes, you can have time variant channel in MATLAB either by using comm.RayleighChannel() , you can read about it in help of matlab. or the other way you use the ...
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  • 1,046
2 votes

Digital communication BER performance

OK, let me explain that in easier way, As you know, in a communication system, to transmit information from transmitter to receiver, we use the binary information system. which means, for example, ...
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  • 1,046
2 votes

Digital communication BER performance

For BPSK it's $$P_e = \frac{1}{2}\left[1 - \sqrt{\frac{\gamma}{\gamma+1}}\right]$$ where $\gamma$ is the average SNR. For 16-QAM, I am not sure if there is a closed-form solution. Check this book. ...
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2 votes

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

One of the most readable (imho) authors on the communication systems is Simon Haykin and the following book from him would probably address most of the issues you would encounter in a wireless ...
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