7 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, ...
AlexTP's user avatar
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4 votes
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How to accurately model wideband RF reflections?

So, to give you something to read up on first, the channel you describe is a Rician or Rayleigh channel, depending on whether you have a dominant line-of-sight path or not. So, as a first approach, ...
Marcus Müller's user avatar
4 votes

Multipath resistance of spread spectrum systems

The key idea in spread-spectrum communications is to use much more bandwidth than the minimum required for the signal being sent. Multipath effects occur when the sent signal $s(t)$ and a delayed, ...
Peter K.'s user avatar
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3 votes

MUltiple SIgnal Classification (MUSIC) Implementation

I'm going to group number 1 and 3 as related. For a high level description of MUSIC, you can take a look at MATLAB's overview here. One of the main steps in the algorithm is to find the eigenvectors ...
Envidia's user avatar
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3 votes
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Wireless Channel Multiplicative Model

What's labeled $(1)$ in your question is a special case, the flat channel. It can be represented as a single coefficient. In general, channels aren't flat, and we then need to apply $(2)$ instead. ...
Marcus Müller's user avatar
3 votes
Accepted

Sound reflections plot

This is an idealized case of the echogram that simply depicts the times of arrival and energy of reflections. You can see this type of plot in literature and as an output in modelling software such as ...
jojeck's user avatar
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3 votes

Intersymbol Interference -- Root raised cosine filter redundant if doing impulse response equalization?

I think it can be misleading to think RRC are used to eliminate ISI. The only purpose of Raised Cosine (RC) and Root-Raised Cosine (RRC) filtering in the transmitter specifically is to constrain the ...
Dan Boschen's user avatar
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3 votes
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Is Phase Locked Loop is essential for BPSK signal reception?

There are three different kinds of synchronization in a passband digital communications system: Carrier synchronization: the receiver needs to know the exact frequency and phase of the carrier used ...
MBaz's user avatar
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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 ...
Ahmad Bazzi's user avatar
2 votes

what does mean quasi-static channel

Quasi-static channels are a "block-wise" time (in)variant. For example, your channel has no variations over time (not in the delay domain) for some time period(e.g., 1 ms), but the channel ...
user520823's user avatar
2 votes
Accepted

Where in the signal chain is Channel Equalization applied?

Generally, any matched filtering would be done before equalization, since there is no practical advantage that I am aware of to applying a matched filter afterwards. Most textbooks that I've read ...
Ill-Conditioned Matrix's user avatar
2 votes

channel gain calculation

In your definition of the SINR, $h$ is the channel coefficient. What it means is this: if we send a signal $x(t)$ and model our channel as stationary and frequency-flat then the signal we receive is $...
Florian's user avatar
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2 votes

Why does altering path length in radio transmission alter the phase of the received signal?

Yes indeed it will be (although we could argue that it may not be necessarily for all distances since the phase is cyclical!). In free space the signal propagates at the speed of light, therefore ...
Dan Boschen's user avatar
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2 votes
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Understanding Pathloss and latency

There are many possible ways to model path loss to include both attenuation and delay (latency). For example, this page from Molisch gives a way to include both: the Power Delay Profile approach.
Peter K.'s user avatar
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2 votes
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How to code Rician fading channel gains from k-factor?

To Q1: Yes you can use a complex Gaussian distribution with mean to simulate a Ricean distribution. In Matlab, you can use something like ...
Harris's user avatar
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1 vote
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How to determine the number of multipath?

You can't really tell that from anything. The maximum delay spread together with your sampling rate, however, gives you the number of paths that you can tell apart with a single observation of the ...
Marcus Müller's user avatar
1 vote

MUltiple SIgnal Classification (MUSIC) Implementation

There is library called armadillo - for C/C++. Using it, you can implement almost everything as in octave - free analog for matlab. Matlab has special modules (phased) which I suppose could highly ...
Stoyan Mihaylov's user avatar
1 vote
Accepted

Why does altering path length in radio transmission alter the phase of the received signal?

Next, I receive the signal at two different locations with different distances from the receiver. Will the phase of the received signals be different for the two sites? It depends on the time ...
auspicious99's user avatar
1 vote

Why does altering path length in radio transmission alter the phase of the received signal?

Phase measurement depends on a reference time or point. If your time reference or clock sync is the same speed-of-light signal, then the phase of a signal with reference to itself is zero. If ...
hotpaw2's user avatar
  • 35.3k
1 vote

Hf ionospheric channel model for large bandwidth

There is the Watterson channel model, and it can be extended to any bandwidth
Abby_DSP's user avatar
  • 315
1 vote

Simulating multipath channel

You put zeros in between to show delay between the channel taps. I don't know what $M$ is in your code but suppose $M=10$ and say your sample rate is 10 MHz. Then you can interpret ...
Engineer's user avatar
  • 3,022
1 vote

MU-MIMO Sensitivity to Line of Sight (LOS)

There is no mention of light-of-sight (LOS) on the time you mentioned. There is a mention of point-to-point, however. Point-to-point channels could be LOS or multipath. MU-MIMO is better than point-...
BlackMath's user avatar
  • 675
1 vote

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

Let's tackle this piece by piece: Path loss Your path loss model gives the path loss in dB. Convert to linear scale. You can directly read $\alpha$ and $G$ from the result. Haven't read that paper ...
Marcus Müller's user avatar
1 vote
Accepted

Need information about following channel model

The channel impulse response represent the weighted gains and phases at different delays, so yes this is a multipath channel. You can simulate the channel (in Matlab as you requested, what I show ...
Dan Boschen's user avatar
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1 vote
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Cross-correlation peaks in acoustic multi-path conditions

I assume by "shift" you mean "shift in time". No, the first correlation peak should not be shifted in time, you should just get multiple peaks, assuming the time difference of arrival is not much ...
Jim Clay's user avatar
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1 vote

What is the suitable mathematical form of the multipath channel impulse response?

Let's say we have a function that we transmit which is: $$x(t)$$ Transmitting the function is kinda easy part. We assume there is just the function we are trying to send. However things are a little ...
Furkan Küçük's user avatar
1 vote

modelling wireless multi-path channel - is channel response sum of delta(t-path_delay) or "delta" should be smoothed somehow?

You may try this paper: Asplund H., et al - How typical is the "Typical Urban" channel model? - Mobile-based Delay Spread and Orthogonality Measurements to see an actual measurments result, ...
Zvord's user avatar
  • 41
1 vote

OFDM Times of Arrival of multipath

I don't fully understand your question, since you correctly state $\tau_i$ are delays of the multipath therefore, $\tau_1$ is simply the delay incurred by the shortest path. And no, $\tau_{i\ge2}$...
Marcus Müller's user avatar
1 vote

I want to know if there is a practical way to find out if multipath propagation is significant for audio in a given environment?

Never done this but it might work. Record the audio simultaneously using multiple microphones located in the neighborhood of your main recording position. If the cross-correlations between signals ...
Olli Niemitalo's user avatar

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