Questions tagged [equalization]
The equalization tag has no usage guidance.
127
questions
1
vote
1answer
57 views
Mathematical expression of Multicarrier frequency equalizer
I have a signal $X$ with length of $N$, multiplied with any unitary matrix, i.e the transpose of DCT matrix as:
$x = D' X$
where $D'$ is the transpose of the of DCT matrix. Then let's add $CP$ guard ...
0
votes
0answers
42 views
MATLAB model for equalizer using LMS algorithm adaptive filter and unexpected output curve
The MATLAB code below is for equalizer using lms algorithm adaptive filter and then plotting MSE (Mean Square Error) Vs Iteration numbers
...
1
vote
1answer
36 views
The cost function of LS algorithm
I'm trying to understand the derivation of LS algorithm for channel estimation in OFDM.
Could anyone explain why do we need complex conj transpose in the below equation?
0
votes
0answers
19 views
Compensating for poor illumination across a specific image axis - possible solutions?
A friend of mine is working at an institute for nano-membranes. Currently they are using ImageJ and do a lot of manual (in my opinion inaccurate) work to process some membrane "photos" (...
0
votes
0answers
8 views
quantification of histogram equalization improvement
My project consist of classification of images using ML. The images are microscopic slices. For the feature extraction phase, I am using multiple filters and got a good result.
So I decided to do a ...
2
votes
1answer
33 views
Channel equalization affect on input signal
I have the following problem.
Am trying to understand how the channel block affects the input signal s(n).
I know that x(n), the input signal to the filter is basically:
\begin{equation}
x\left(n\...
0
votes
0answers
64 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 ...
0
votes
1answer
38 views
ZP-OFDM vs. CP-OFDM channel equalization
Now, I am working on OFDM equalization, according to what I understood, Adding CP into the OFDM block change the convolution from linear to circular. That circular convolution enables using point-wise ...
0
votes
0answers
19 views
Equalization of ultrasonic transducer [duplicate]
I am working with ultrasonic transducers with frequencies 100 kHz, one for transmission one for reception. The transmitted signals are chirps. I would like to measure the time of flight between ...
1
vote
2answers
86 views
Distortion of OFDM signal when using RRC filter
I am trying to transmit OFDM signal in pass-band based on RRC filter, but what I noticed that the signal before the RRC filter is completely different compared with signal after the RRC filter (It ...
0
votes
1answer
63 views
Should we upsample the channel when upsample the signal
I have an OFDM system with Number of sub-carriers $N= 1024$, modulated data using $QAM$ modulation is transmitted via those subcarriers as follows:
...
0
votes
1answer
42 views
Convolution that outputs a unit impulse
Im thinking whether any convolutional operation can output a unit impulse, an example to further explain:
where a convolution between system $h[n]$ and unknown system $g[n]$ would output $\delta[n]$.
...
0
votes
0answers
23 views
Time Reversal OFDM
I am trying to understand the Time Reversal OFDM where ,According to my opinion, the channel is reversed in time domain at receiver side and then equalized.
what I found online is something similar ...
0
votes
1answer
65 views
What's the computational complexity of MMSE equalizer in OFDM system
As I know that in case of one tap OFDM equalizer, (ZF equalizer), we should have $N$ division complexity since we divide every subcarriers by its correspondent channel tap in frequency domain.
But I ...
0
votes
0answers
13 views
chromatic and polarization mode dispersion compensation in electrical dmain
I am currently working on adaptive compensation of chromatic and polarization dispersions in the electric domain using LMS (least squares method) and CMA (constant module algorithm) algorithms.
I am ...
0
votes
0answers
42 views
How to implement Minimum mean-squared error (MMSE) equalization?
I have the channel estimation and noise power estimation and I need a matlab implementation of time domain siso channel Equalization.
Theory:
Consider the FIR filter of length $N+1:$
$$
\hat{s}_{k}...
0
votes
0answers
41 views
On the channel estimation based on vector
I have a matrix $X$ of size .i.e $(8,8)$ with $M$ columns and $N$ rows. Suppose I took it's $iFFT$ column wise resulting matrix $x$ of size $(8,8)$ too,
$x = F^HX_{(:,m)}, $ ...... (1),
where ...
1
vote
1answer
49 views
Is DFE equalizer always blind or can we use reference signal?
I have made a blind DFE Equalization, I mean decision directed .
But I am not sure how to make an implementation based on reference signal known by receiver and emitter. In the back forward filter ...
1
vote
1answer
44 views
How to use matlab toolbox for 2qam dfe equalizer?
I made Channel equalization with matlab,
You can find the code below.
...
1
vote
1answer
93 views
The use of LS estimation with Vector OFDM
I work in Vector OFDM, but I had an issue in channel estimation in that scheme. For example, I try to use LS channel estimation but I can't get the performance back. However, in conventional OFDM, I ...
0
votes
1answer
90 views
Channel estimation and interpolation by vector in OFDM
I have V-OFDM system (Vector OFDM) where every symbol is organized as in below figure:
The black cirles are pilots and white circles are data. First, iFFT operation it taken per column, and then ...
0
votes
2answers
70 views
OFDM time vs. frequency domain channel estimation/equalization
In OFDM, the majority of Equalizers are used in frequency domain. I mean the signal is transmitted in time domain (after performing iFFT), then to estimate the channel we should perform FFt to use ...
0
votes
1answer
56 views
Effect of Adding the cyclic prefix on the toeplitz matrix in OFDM
Assuming we have $N$ symbols to transmit encoded in block $k$,
Performing $N$āiFFT at the transmitter, we now have
The resulted signal $x(k)$ has length of $N$. inserting a cyclic prefix $CP$ ...
0
votes
0answers
45 views
How to compute the DFE based MMSE equalizer FF and FB coefficients in a non adaptative way?
I seek your assistance,
I am reading the Proakis 5th edition and I came across a paragraph explaining the tuning of DFE filters, i.e, how to compute the FF(FeedForward) and FB (Feedback Filter) ...
0
votes
0answers
31 views
Code implementation of Channel estimation based DFE Equalizer in matlab (or octave) without the the signal processing tool box
I want to implement a DFE in matlab without the signal processing toolbox:
I have two filters ( FeedForward and FeedBack) with taps length equal to 15.
I know the update equation of the LMS ...
0
votes
0answers
8 views
How to choose the algorithm for DFE filter adapatation, if the criterion is MMSE?
I hesitate between LMS and RLS ,
and for the feedforward filter and feedback filter, what must be the length of the filters as a function of the channel delay spread.
Any help will be really ...
0
votes
1answer
44 views
MMSE- Channel estimated based - DFE Equalization
For HF ionospheric channels ( frequency range 3 up to 30 MHz), I Want to make channel equalization in time domain, using MMSE criterion. I have to do it using the channel estimation.
I have some ...
1
vote
0answers
61 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}$$
Note that for OFDM system, (1) is assumed channel input-ouput equation on ...
0
votes
1answer
52 views
Adaptive equalization vs inverse of transfer function
I have the following equalization problem as shown in the figure below:
Now I can compute the coefficients for my adaptive FIR filter c (dim(c) = N) the following:
$\mathbf{c_{opt}} = (\mathbf{H}^T\...
3
votes
0answers
42 views
Block CMA algorithm
The Constant Modulus Algorithm is a common equalization method which adapts at every sample in an attempt to give a filter which produces a fixed power output. Divergence/convergence of the CMA ...
2
votes
1answer
125 views
Output of Zero-forcing equalizer doesn't match theoretical calculations
Let's say I have a sequence $x[n]$ (signal) and perform convolution with another sequence $h[n]$ (channel), so:
$$
y[n] = h[n]*x[n] = \sum_{k}{h[k]x[n-k]} \leftrightarrow Y(z) = H(z)X(z)
$$
I'm ...
0
votes
2answers
96 views
Types of equalizers
I can't get my mind around the different types of equalizers and the difference between some of them. I've been looking at different books unsuccessfully.
So far, I have Wikipedia's list and this ...
2
votes
4answers
408 views
What Information Is Lost by Histogram Equalization?
I cannot think of a way to restore an original image after histogram equalization. But this latter seems to "enhance" (= increase contrast of) the image's details. What information is then lost by ...
1
vote
1answer
19 views
Question about image equalization
Let $f$ be an $N \times M$-image and suppose that $g$ is its equalization.
Question - Why the equalization does not change the objects, why a car on $f$ does not convert into a bus on $g$?. It is ...
0
votes
1answer
97 views
On the signal recovery in OFDM after estimation
Given a modulated signal X which is transmitted based on OFDM with N = 256 sub-carriers through channel ...
0
votes
0answers
67 views
Clip wav by PSD
I have the following two things.
sequence_1: Sound file in the wave format.
PSD_1: Some PSD (Power Spectral Density).
I want that the PSD(sequence_1) < PSD_1 for all indices.
How I think about ...
1
vote
0answers
24 views
Converting the equalizer coefficients from VSA at 2 sample/Symbol to 1.5 sample/Symbol
I was looking for some feedback on conversion of equalizer/filter coefficients at different sampler rate.
Problem Statement:
We have built a transmitter system whose output is at 1.5 sample/symbol (...
2
votes
0answers
19 views
How to exploit auditory masking to boost intelligibility
I am currently working on a dynamic equalizer to improve a synthesized voice's intelligibility in noisy environments.
The current implementation of my algorithm simply applies a parametric EQ to the ...
1
vote
1answer
79 views
Training Fractionally Spaced Channel Estimator and Equalizer
If you are attempting least squares channel estimation with a fractionally spaced channel estimator, do you want the training sequence to also be fractionally spaced or symbol spaced? It looks like ...
0
votes
0answers
87 views
Digital Communications block diagram question
I am new to digital communications and trying to understand the basic underlying concepts of digital comm systems. So far , studying the course , I have some questions which if anyone can answer would ...
1
vote
0answers
192 views
The Definition of Q Factor by an Equation and How to Graph
I am currently building an EQ in an music app, and it's relatively simple:
6 bands of fixed center frequency, and a Q knob to control the Q of all bands, because we do not currently have space for ...
0
votes
1answer
92 views
Is CMA equalization applicable for OFDM
I have a question regarding the constant modulus algorithm (CMA), as you know it's one of the known algorithms used for blind equalization. The cost function of the CMA is build blindly, it means ...
1
vote
1answer
131 views
Where in the signal chain is Channel Equalization applied?
I am reading about channel equalization and I am somewhat confused on where in the signal chain channel equalization is normally applied and if it's before or after a correlator detector or matched ...
3
votes
1answer
388 views
What is the difference between an equalizer and a channel estimator?
I was wondering what is the difference between channel estimator and channel equalizer?
Thanks!
0
votes
1answer
48 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 ...
0
votes
1answer
54 views
Equalizing a temporal sound signal with a convolution
This question is more or less the following of a previous question.
The aim is to equalize some sounds signals. By equalizing, I mean increasing or decreasing some frequency ranges, a bit like an ...
0
votes
1answer
181 views
Inter-Symbol Interference (ISI) channels
Is there any open and free data-set for digital ISI channels? I want to have a variety of ISI channels' taps, such as $h[k]$ here. Especially looking for BPSK channels.
0
votes
1answer
73 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 ...
0
votes
1answer
48 views
how to set Equalizer's coefficient using generalized eigenvector.
In that paper https://jwcn-eurasipjournals.springeropen.com/articles/10.1186/1687-1499-2012-72 .. Equation 3,
$J(w) = w^HBw/w^HCw$ ..
$B$ and $C$ are matrices, $w$ the filter coefficients vector ...
1
vote
1answer
459 views
estimate the impulse response after equalization
I want to estimate the impulse response of the channel at the receiver. Assuming
some arbitrary impulse response: h=[1 0.2 -0.4 0.0 0.6]. Once the equalizer is ...
