8 votes

Can anyone explain how dft works as a filter bank?

To add to Richard's good answer, I specifically want to show the difference between: Down-conversion and low-pass filtering (heterodyne the signal). Bandpass filtering the signal directly (...
Dan Boschen's user avatar
  • 50.1k
6 votes
Accepted

Can anyone explain how dft works as a filter bank?

@Ahmet. The DFT equation you posted does not compute an array of complex numbers. For any single given integer value of frequency-domain index $k$ the equation tells us how to compute the single ...
Richard Lyons's user avatar
5 votes

Subcarrier spacing in OFDM

There are many intepretation of OFDM to answer your question. One way I find intuitive is looking at the resolution of (Discrete) Fourier Transform. By capturing a signal during time $T$, and by ...
AlexTP's user avatar
  • 6,585
3 votes
Accepted

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
3 votes

Advice needed for separating 3-channel signals

I understand that you receive A, B, and C and you want to separate it into A1, A2; B1, B2; C1, C2. From this, you can do the following: Model your expected signal A1 as some pulse shape (here, I ...
Maximilian Matthé's user avatar
2 votes

How to implement a $j$-level $M$-band wavelet transform of an image?

[EDIT: some code made available] The notion of $M$-band wavelet transform, $M\ge2$, generalizes the standard $2$-band wavelet. The theory is provides, for instance, in Theory Of Regular M-Band ...
Laurent Duval's user avatar
2 votes

How to estimate ALL time-delays across MULTIPLE signals?

There are papers describing a method called multichannel cross-correlation, that recursively estimates time delay of each signal. However, If I have not missunderstood you problem you can also ...
David Bondesson's user avatar
2 votes

Understanding Communication Theory Jargon for Statistical Linear Models

The equation you wrote down describes the case for a narrowband (flat fading) MIMO system. Narrowband/flat fading describes the scenario when your signal bandwidth is small relative to the channel ...
Engineer's user avatar
  • 3,022
2 votes

Understanding Communication Theory Jargon for Statistical Linear Models

The equation $y = hs + n$ is a discrete-time model of a certain kind of wireless communications system. $s$ is a complex number, drawn from a finite set called a "constellation", that represents the ...
MBaz's user avatar
  • 15.3k
2 votes

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

I would recommend you a book from Emil Björnson. He is a professor on the Linköping University and also produces a lot of content on his Youtube channel (which I will not link to avoid getting ...
TheWirelessClassroom's user avatar
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 ...
Fat32's user avatar
  • 28.1k
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
1 vote

concurrent multiple sound sources seperation for TDoA estimation

Shuo, Here is a couple of insights for your system: 1.- The different sound sources must play different signals (beacons), that may be resolved at the receiver device. A simple example would be to ...
Luis M Gato's user avatar
1 vote

Standardizing signals from the same experiment setup with different recording tools

I don't think there is a "one size fits all" answer for this. Here is one possible process assuming that your goal is "if I measure a system with both tools I should get the same result&...
Hilmar's user avatar
  • 44k
1 vote
Accepted

Does non-orthogonal multicarrier modulation use pulse shaping?

Yes, if we are not using orthogonal frequency multiplexing and concerned about interference in adjacent channels (specifically if we want to constrain the total spectral occupancy for one channel) ...
Dan Boschen's user avatar
  • 50.1k
1 vote

Averaging two channels with Python

Just doing np.mean(y,axis=0) seems to work for me. But to really check I'd need to know how you loaded the file. My code below. Code only ...
Peter K.'s user avatar
  • 25.7k
1 vote
Accepted

autocorrelation of multiple signals

You apply the same formula, but instead of using a scalar $x(n)$, you will have $x(n) \in \mathbb{C}^{M \times 1}$, where $M$ is the number of channels, and $x^{H}(n)$ is the $1 \times M$ matrix whose ...
Bob's user avatar
  • 2,233
1 vote
Accepted

What is the Co-channel interference in MIMO communication

Co-channel interference occurs when multiple users are sharing the same resource (e.g., time-slot and frequency) and is also known as multi-user interference. In your original question, you were ...
Guilherme Zilli's user avatar
1 vote

Binary image? Only black and white?

A binary code is a relatively abstract representation of some quantized information on two levels. As such (being an abstract think), it often requires to be interpreted to turn into a real-word ...
Laurent Duval's user avatar
1 vote

Binary image? Only black and white?

Your image is binary or two-tone per color channel. Thus you have 2x2x2=8 possible tones, or 3 bits. In a bitmapped image, you can encode each pixel using any number of bits, then use a global table ...
Knut Inge's user avatar
  • 3,350
1 vote

What do you mean by radio sensing a channel?

The station here is continuously monitoring the energy in the medium. Let us say you want to transmit in channel 1 of 2.4GHz band. Your RF hardware is always in receive mode if you don't want to ...
jithin's user avatar
  • 2,253
1 vote
Accepted

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

I don't know why we can't use RRC filter with OFDM ?!! Yes, of course, we do can. The only disadvantage for that is the complexity. however the gain will be in spectral efficiency improvement and ...
Zeyad_Zeyad's user avatar
  • 1,056
1 vote

Eight Sub Band Filter Design

This sounds like the classical job of a polyphase filterbank, and a cascade of polyphase synthesizers. Yes, do this in complex baseband. First, you use your filterbank to divide the 25 MHz in 25 kHz ...
Marcus Müller's user avatar
1 vote
Accepted

DoA estimation using microphone array

The mistake could be in assuming you know which angle $a$ to use when you don't know if the source is in front of or behind the array yet. In other words, you need to solve the same problem for $a$ ...
Guest's user avatar
  • 390
1 vote

What is the relation between noise (AWGN) variance and number of antennas?

There is no relationship if the noise if white. For the system $$\mathbf{y}=\mathbf{H}\mathbf{x}+\mathbf{n}$$ where $\mathbf{n}$ is $K$-dimensional, the covariance matrix is $\sigma_n^2\mathbf{I}_{K\...
BlackMath's user avatar
  • 675
1 vote

Distribution of the output of AWGN channel

I see this question is open for a long time, I am not sure if I understand it correctly. PDF of the symbols The first probability is a $P_{\mathbf{Y}}: \mathbb{C}^n \to \mathbb{R}$, you are not ...
Bob's user avatar
  • 2,233
1 vote

PortAudio: how to generate multiple sounds

The beauty of PCM (pulse-coded modulation, i.e. time samples of audio) is that the mathematical sum of two signals sounds like the acoustical superposition. So, just add your two sines sample-wise.
Marcus Müller's user avatar
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
Accepted

Real-time delay between signals

I can't comment because I'm a new user... have a look to these questions: Estimating the time offset (delay) between two audio signals in real-time Generalized Cross Correlation Time delay ...
Behind The Sciences's user avatar

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