Questions tagged [channelcoding]
Questions related to channel coding, forward error correction, code performance calculations, and decoding algorithms. Typical code examples are Hamming codes, cyclic codes, BCH, Reed-Solomon, turbo codes, and LDPC.
131
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What are different encoding schemes used in gigabit ethernet?
I was reading about digital transmission, there are many steps namely
Analog to Digital conversion
Source coding
Channel coding
Line coding
Pulse shaping
Modulation
Multiple access techniques
Out of ...
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41
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Comparing communication systems with different modulation orders and code rates
I propose an end-to-end communication method in my research. The key part of the method is not the channel coding and modulation but we use them anyway. I am using 1/3 rate Turbo codes with QPSK and ...
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Raw BER or Uncoded BER in LTE/5G
Could you please tell me what would be the benefit of using Raw BER (or uncoded BER) in comparison to BER?
Thanks
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How to calculate the following mutual infomation between $X$ and $Y$ in matlab or python?
Recently I meet the following question: Let $X\in {\mu_1,\mu_2,\cdots,\mu_m}$, $Y \in {R_1,R_2,\cdots,R_n}$, where $\mu_i, i = 1,2,\cdots,m$ is means of $m$ gauss probablity density function, $Y$ is ...
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How to accomodate feedback bits from Base Station to devices in LTE or 5g?
I am trying to think of a way in which the base station (BS) can send say 100 bits of feedback to devices in my cell. My confusion is what is a good way to send this feedback bits.
This is during the ...
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137
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Generate 5G compliant parity check matrix and save it to .alist file
My aim is to try out the 5G LDPC codes by using the aff3ct library. This library needs the parity check matrix loaded from a .alist or a .gc file to create the LDPC encoder. I've been looking how to ...
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122
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Why can interleaving make the channel "memoryless"?
I'm trying to understand "interleaving" from a theoretical point of view. This paper claimed that by sufficient long interleaving, the channel can be treated as memoryless.
Does this holds ...
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recursive, systematic convolutional encoder with finite response
In an exercise, we had the following recursive encoder given:
For which we should find an input sequence that generates an output with finite hamming weight (I see this question similar to a find ...
- 103
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103
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RS FEC correct more than t/2 errors sometimes... why is this happening?
According to the Reed-Solomon Wikipage, the RS code can correct up to $\lfloor\frac{t}{2}\rfloor$.
While I was playing around with Reed-Solomon FEC (github repo), I noticed that sometimes the RS(544, ...
- 155
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Proof of the minimum distance of Reed-Solomon codes
How we can prove that the t-error-correcting Reed-Solomon code with symbols from $GF(2^m)$ generated by
$$g(X)=(X+\alpha)(X+\alpha^2)...(X+\alpha^{2t})$$
has minimum distance exactly $2t+1$ where $\...
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What are the possible forms of generator matrix of a systematic linear block code?
My text book, Communication systems by Simon Haykin says
Block codes in which the message bits are transmitted in unaltered form are called systematic codes.
I am not getting what it means. A ...
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Chosing the right type of convolution code for a M-QAM transmitter
Coming from my previous question (link to this here). Given the following transmitter design,
with these parameters,
bit rate of 55 Mbps
maximum bandwidth of 17 MHz
code rate : 1/2
minimum SNR to ...
- 135
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Selecting convolutional code for a M-QAM transmitter
I am tasked in an assignement to select an appropriate rate 1/2 convolution code for a QAM modulated transmitter with the following setup,
However, from my understanding of codes and modulation they ...
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How is maximum log likelihood calculated for BPSK?
I am seeking to understand, exactly, how to calculate a soft MLL output from a received BPSK signal, and what information is needed. I would like to implement turbo coding in my system, but the ...
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Eb/N0 on a VLC simulation using OOK modulation
I have been doing a matlab simulation of a VLC (visible light communication) system that uses OOK for the modulator.
I have to explain the basic knowledge behing the simulation and I´m having lots of ...
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Understanding $E_b/N_0$ under different coding rates
I'm trying to understand the $\\E_b/N_o$ concept and how different coding rates affect it. I've read a bunch of topics, specifically this and this, but I'm still missing something to have a clear ...
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Convolutional codes with specific free distance and constraint length
I have to implement a paper where the author in the simulation section has only mentioned the free distance and states(constraint length) of the convolutional code. I have searched the 3GPP ...
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What is meant by channel knowledge? Difference between partial and full?
Keep coming across the term channel knowledge (specifically in the transmitter) in a reading for class but can't really grasp the idea and don't see a clear cut definition. From what I understand it ...
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Help with creating/drawing the PDF of signals X and Y
Given is an analogue source $x$ equally distributed in the interval $[-1;+2]$.
By means of a mapping, the signal $Y$ is calculated according to
$Y = (X - 1)^3$
is generated.
Sketch the $PDF$ of the ...
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303
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Effect of altering FEC k/n versus symbol rate on BER performance
Let's say I hypothetically have a forward error correction (FEC) code with coding rate $k/n= 1/2$. Let's say it is given for now that for a fixed signal-to-noise ratio (SNR) in an additive white ...
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MAP (BCJR) Algorithm with channel LLRs
I have a question about the decoding of convolutional codes with the MAP (BCJR) algorithm.
Let $\mathbf{u}$ denote the uncoded bits and $\mathbf{v}$ is the coded bits. Here is the point!
Let $\mathbf{...
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Reuse channel decoder for a smaller code dimension of linear block codes
I am working with the 5G NR polar code and have implemented the CRC-Aided Successive Cancellation List decoder based on this paper (Tal et al. 2012).
As my decoder is only used to decode a limited ...
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Optimal idle or frame sync symbols for OQPSK
Okay, everyone here knows that my thing was audio and that I have never gotten paid to do anything regarding communications systems. So, while I know a thing or two about DSP and even a little about ...
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103
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Increasing Spreading Factor vs reducing FEC rate
This time, I have been reading a lot about how LoRa works and how it is able to achieve such long ranges in non-LOS propagation channels. However, a simple doubt arises regarding the way they ...
- 157
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Adding FEC to sporadic burst of Huffman-encoded words
This question may be interpreted as a second part of this other question. Basically, if we encode our data using Huffman's encoding and we want to introduce some FEC afterwards, unless we use a ...
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781
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Shannon capacity limit & FEC comparisons
In this figure from Fundamentals of Digital Communications by Madhow , pp 328 there is a comparison of a rate 1/3 turbo code with the shannon limit for rate 1/3 BPSK:
Trying to understand the limit ...
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Why are the minimum distances of a code and its interleaved code equal?
I know this is probably a very trivial question, but I am completely stuck. Let $C$ be a linear $[n,k,d]$ Code. Then the interleaving of depth $t$ is the Code $C(t)=\{(c_{11}, \dots, c_{t1}, \dots, c_{...
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318
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Optimal FEC option for extremely low SNR situation
I am new to this site, which I joined with the aim of finding someone to help me with a little doubt.
I am trying to design a system that must be able to work at extremely low (the lower, the better, ...
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Is there an optimal way to quantize log-likelihood ratios of an AWGN channel?
My understanding is that given an AWGN channel and BPSK modulation, an LDPC decoder that uses message passing takes as input log-likelihood ratios $L$ of the following form by Bayes' rule:
$$
L=\frac{...
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Verifying LDPC matrices in CCSDS blue book
My understanding is that LDPC is a linear block code such that its generator matrix $\mathbf{G}$ and parity check matrix $\mathbf{H}$ satisfy $\mathbf{GH}^T=0$.
I am using the CCSDS blue book here as ...
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What's the shortest possible code that correct all the single bit errors?
Suppose the original code is a 2-bit binary coding with 3 possible alphabet.
\begin{align}
a&\rightarrow 00\\
b&\rightarrow 10\\
c&\rightarrow 11
\end{align}
Is that $\operatorname{Hamming}...
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Understanding of Reed Solomon code
We send the data in bytes to the RS Encoder block. The RS Encoder block encodes the data with the Reed Solomon (225,223) code. It waits for 223 bytes and after this encode them to make a codeword of ...
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Channel coder: Does encoder help? Input signal distortion:
I am studying the channel coding theory. The channel coder adds redundant information to the input signal, that helps a decoder to reconstruct the signal.
BUT: Can encoder help to eliminate effects ...
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code construction process in polar coding
Arikan in his paper (arXiv link or IEEE link) about polar coding, explains how you can force the channel to polarize by applying a linear transformation (the generator matrix). He calls this a split ...
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system bit rate vs channel coding
We are usually asked about the full system bit rate. However, we use channel encoding in practical systems, for example conventional coding with rate $(1/3)$. My question is about the full system bit ...
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Conventional channel coding/decoding
I am trying to understand the algorithms of channel coding. Regarding the conventional channel which is, for me, the easiest one to implement, I have a question regarding the output of its decoder.
...
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553
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Setting Parity Check Matrix for LDPC channel coding
I am trying to implement the LDPC code for OFDM system, where I input data should be binary of length $1024$ and the output coded data of length $2048$ (means of rate 1/2).
As known in Matlab ...
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LDPC for channel coding
I am working on OFDM over harsh channel, so the channel coding is an essential thing for achieving a reliable communication.
According to my reading, LDPC is almost the best channel coding we can use ...
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Is there two version of ulaw and alaw encoding in audio compression?
I am new to encoding in audios and i have searched for ulaw and alaw and found there is conversion from audio to this encoding CCITT alaw/ulaw and as i have known alaw/ulaw belongs to ITUT group not ...
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Degrees of freedom in coding (for a communication channel)
I was reading on my lecture slides about how to achieve diversity (i.e. transmit more copies of the same message in order to avoid its corruption; this technique may be realized by repeating the ...
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Channel encoding after digital modulation
Generally, when using channel encoding followed by interleaving, that process should be performed before the modulator and the system structure should be like that :
For me, I only use the ...
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Minimum value of G (Amplitude) that guarantees an error probability of at least $10^{-2}$ in a 32-PAM transmission system
pretty much new here.
This question comes from an Online course quiz which i have already completed but cant seem to get a good sleep over, just because i cant figure it out.
Below is the question ...
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Interleaving or randomisation?
I am trying to implement a digital communication system as a learning exercise. For error correction, I am using two concatenated codes (RS and convolutional). However, I read that, in order to reduce ...
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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 ...
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Update rule in Soft Output Viterbi Algorithm (SOVA) -Hagenauer rule
Soft output of SOVA, suggested by Hagenauer http://www.cse.lehigh.edu/~jingli/teach/S2003turbo/notes/SOVA.pdf , says in 2.2.2 "The Soft-Output Viterbi Algorithm" that
$L_{j}^{\verb|^|}:= f(L_{j}^{\...
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112
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Understanding Asymptotic Equipartition Property
I have some problems in understanding the precise meaning of the Asymptotic Equipartition Property, related to a large number n of independent and identically distributed random variables (X1, X2, ...,...
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Definition of Perfect Code (and example of Hamming Code)
Let's consider the following sentences about coding a message before transmitting it in a communication system (here you find the complete pdf)
First question: can you explain me these two ...
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Notes or books to quickly get started on the basics of signal processing or wireless communication
I'll soon start working in signal processing, specially wireless communication systems. Hence I'd like to get a quick understanding of MIMO and related systems, for example, the topics like:
1) where ...
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Nyquist noiseless channel capacity; how can bit-rate be two times the bandwidth?
I'm confused by the Nyquist channel capacity formula. How can channel maximum capacity approach double the bandwidth.
$C = 2\times BW \times log_{2}(L)$ bits/sec
The way it was explained to me ...
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How to detect missing bit position in a bit-stream?
I'm trying to establish a one-way communication and facing problem in the receiver end because of some missing bits. For example, if the sender sends 100 bits the receiver received 95/96 bit. Now the ...
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