9
votes
Accepted
FFT vs DFT Run Time Comparison (Complexity Analysis) in MATLAB
Abhinav Jain, Welcome to DSP Community.
I build for you a proper testing of the run time comparison.
Few tips about timing in MATLAB:
Never time in a script. Always call a function to do the heavy ...
- 20.5k
6
votes
Accepted
Interleaving or randomisation?
So, the technical difference between a scrambler and an interleaver:
The interleaver is just a permutation of input symbols; a resorting.
The scrambler is an operation designed to modify the ...
- 32.5k
4
votes
Accepted
Finding preferred pair of $m$-sequence for Gold code
Printed tables of irreducible polynomials of large degrees are usually incomplete because there are so many of them! What one can do is use various tricks of the trade to figure out a set of $68 = 2\...
- 20.9k
3
votes
Why is Line coding called "Line coding"?
Line coding is the process of how one can choose to map, i.e. encode, information (e.g. bits) into signals (voltage/current) that can be sent over a transmission line. There are different encodings ...
- 733
2
votes
Accepted
Randomized prefix code
No, it is not possible. A proof follows.
Let $\mathrm{E}(L \mid 0)$ be the expected codeword length for the prefix code $0$ that minimizes it. The answer to the question is "no" if it is always true ...
- 13.7k
2
votes
Accepted
RS FEC correct more than t/2 errors sometimes... why is this happening?
Beware: what you're seeing could be the result of a bug in your code.
Having said that: in general, algebraic codes such as BCH and RS are very hard to decode using algebraic algorithms. Practical ...
- 15.4k
2
votes
What is the best coding strategy?
"Best" requires you to provide some quality metrics and these are in most cases highly dependent on your specific application.
Generally there are two classes of compression algorithm "...
- 48.2k
2
votes
Accepted
How good is the Leech lattice for AWGN coding or MSE quantization of Gaussian sources?
Tables 7.1 and 7.2 from Lattice Coding of Signals and Networks by Zamir are essentially this.
Also the figures in this paper: https://arxiv.org/pdf/1103.0171.pdf
2
votes
Interleaving or randomisation?
Scrambler is generally used on the message bits itself (before coding happens on the message bits) to prevent long run of 0s or 1s in the message bit pattern. Originally it came from ethernet ...
- 2,303
2
votes
Accepted
What's the difference between quantization and coding?
Quantization is simply the rounding associated with going from a higher precision numbering system to a lower precision, for example analog to digital, or floating point to fixed point, or from a 16 ...
- 55k
2
votes
Accepted
Multi-bit gold code
Yes, that is the whole point of Gold sequences. If $x$ and $y$ are a pair of preferred m-sequences of period $N$, then their periodic cross-correlation function is bounded. It also happens to be take ...
- 20.9k
1
vote
Optimal idle or frame sync symbols for OQPSK
If designing a new waveform and choosing parameters such as preambles, idle channels, etc, we need to be clear on what problems we are trying to solve, and these involve further details if known on ...
- 55k
1
vote
Shortened linear codes
I know Ci has to be a linear code because the codewords in it are taken from C which is linear
Not that fast! You removed elements from $\mathcal C$ – the result need not be a linear code anymore. ...
- 32.5k
1
vote
Accepted
Having trouble interpreting z-transform description of a predictor from a codec paper
This seems a 2D filter.
$A(z_\ell,z_b)=(1-\alpha{z_\ell^{-1}})\cdot\frac{1-{z_b^{-1}}}{1-\beta{z_b^{-1}}}$
Is a FIR on the $\ell$ dimension and recursive in the $b$ dimension.
Let's express in terms ...
- 2,393
1
vote
Optimal FEC option for extremely low SNR situation
Very shortly: as you approach the ultimate Shannon limit (-1.59 dB = Eb/N0) with a finite-length code, then you're better off not coding at all. Intuitively, you have very little energy to spend, and ...
- 32.5k
1
vote
Understanding of Reed Solomon code
You're doing a Reed Solomon in the form of RS(255,223), or RS(n, k). In the case that the data you're trying to encode is shorter than k, then you can just add zeros to the data until the data size is ...
- 378
1
vote
Transition table / matrix for convolutional encoder K=3 understandings
The OP's question reveals many mis-understandings of the issues.
The convolutional code in question is a nonsystematic $[2,1]$ convolutional code with constraint length $K = 3$. The specification is ...
- 20.9k
1
vote
Differential Encoding for M-PSK
I don't fully understand what the OP means by DQPSK but suspect that he believes that the D in DQPSK stands for "differentially coherent demodulation of" QPSK, that is, DQPSK means ...
- 20.9k
1
vote
Most reliable way to decode PAM2 signal with unknown signal levels?
I suggest as a simple approach start with the threshold you chose and then bin the samples that are above and below threshold and take the average of each of those separately and then adjust your ...
- 55k
1
vote
Bandwidth and BER of FM0 encoding
40kHz would be the two sided bandwidth, in which case sampling requirement is 40khz minimum
- 2,655
1
vote
Accepted
Definition of Perfect Code (and example of Hamming Code)
I give an explanation that avoids the pejorative comments of Engineer.
First question: can you explain me these two definitions of perfect code?
Those are not two definitions of perfect codes but ...
- 20.9k
1
vote
Accepted
What is the Asymptotic Equipartition Property (AEP)?
When you are sampling a stochastic process $n$ times, the larger you make $n$, the higher the probability that the series of samples is contained in the so called strongly typical set of outcomes of ...
- 2,383
1
vote
Accepted
Prefix code of symbol pairs
A simple example: consider a source $S = \lbrace 0, 1 \rbrace$ with probabilities $\lbrace 0.9, 0.1\rbrace$.
If you take one symbol at a time, no compression is possible: you need one bit per symbol.
...
- 15.4k
Only top scored, non community-wiki answers of a minimum length are eligible