Questions tagged [forward-error-correction]

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1answer
30 views

Why does the flat part of the BER curve appear after the Viterbi decoder (MatLab)?

I am trying to implement convolutional codes according to this MathWorks example in MatLab 2014a. ...
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2answers
28 views

I am trying to convert a signal into another unit, but the error keeps increasing during each iteration

I have a signal, A, and I want to convert it into another unit by using a formula: $$s_i = \frac{(1+x_i)}{(1-x_i)}\cdot s_{i-1}$$ where $x_i$ is each sample of ...
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0answers
9 views

Trellis-converging offset and the min-sum algorithm

I am going through a paper on the design of interleavers for Turbo codes and I am a little bit confused about how to calculate what they call Trellis-Converging offset. They define such parameter of a ...
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1answer
63 views

Is it possible to generate Hamming code with minimum distance $d$ which can correct more than 1 bit error?

In literature, all I am seeing is Hamming code with minimum Hamming distance $3$. Theoretically a Hamming code with minimum distance d can detect $d-1$ errors and can correct $(d-1)/2$ error. So ...
0
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1answer
47 views

Does Reed Solomon successful decoding guarantee valid payload?

I've got a CCSDS message. It was decoded by viterbi, de-randomized and processed by Reed Solomon decoder. Decoder said that 14 bits were corrected. However when I decode payload according to the ...
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2answers
73 views

Does Forward Error Correction (FEC) affect upsampling factor?

Is the redundant data introduced during forward error correction (FEC) counted as upsampling? I'm taking a binary data stream, doing convolutional encoding of rate 1/2 on it, then making it NRZ ...
0
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1answer
34 views

Design of Reed-Solomon Code where $n < q-1$

I'm trying to figure out how to design a Reed-Solomon generator polynomial where $n$ divides $q-1$ (I believe it's denoted by $n|q-1$) but where $n < q-1$. For example, lets say we have a $q=16$ ...
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1answer
125 views

Viterbi Decoder without traceback

How can I use Viterbi algorithm for a real time scenario where I cannot afford to have delay in the tracing back the best path to the initial state?
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2answers
620 views

Confusion in Channel Encoding and Convolutional Encoding

If I'm making NRZ signal by first encoding 1 input bit into 10 bits multiplied by -V/+V before sending it into a channel, is it called channel encoding? If I then modulated it using GMSK technique, ...
2
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2answers
237 views

What are trellis?

I hear the term trellis used in many contexts (trellis codes, trellis graphs, etc). From what I gathered from reading online resources, it seems that it's just a constraint graph that connects nodes ...
2
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1answer
70 views

Forward error correction with limited possible errors

I am using a Reed-Solomon FEC implementation in GF(1024) to correct T=15 errors in a given codeword. In the particular implementation though, I know for a fact that for each transmitted symbols, the ...
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1answer
53 views

Defending Continuous values using Error Correction Codes

Say I'd like to transmit, using FSK modulation, a 100-bit packet which has a continuous field. I'd like to protect this value with an error correction code but an error in the MSB of this value is ...
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2answers
550 views

Difference between diversity gain and coding gain

I am reading about space-time codes. They break down further into 2 sub categories called space-time trellis codes and space-time block codes. It says that trellis codes offer both diversity and ...
1
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1answer
134 views

Fountain codes and LDPC codes

I am having a small clarification with the difference between LDPC and fountain codes. In LDPC codes, each parity bit is depenedent on numerous data bits. Isn't that similar to fountain codes as the ...
0
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1answer
72 views

Difference between diversity combining and multiplexing

How exactly are diversity combining and multiplexing different? My current understanding is that, in certain types of diversity combining such as maximal ratio combining, the same message is sent ...
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1answer
97 views

lower-rate LDPC codes

Currently I am using $(128, 64)$ LDPC codes to error correct messages wirelessly sent in Arduino using the SoftwareSerial library. I was advised to use a lower-rate LDPC code and see if that improves ...
0
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1answer
31 views

Does Reed-Muller codes exist when $r = 0$ and $m = 0$?

Does Reed-Muller codes $\mathrm{RM}(r,m)$ exist for $r = 0$ and $m = 0$? Namely, does $\mathrm{RM}(0,0)$ exist? Some books mention that $m$ should be a natural number whereas some books mention that ...
0
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1answer
44 views

Block code error control with $d \ge c+u+1$

This is about error control coding formula $$ d \ge c+u+1$$ of a block code, with $c$ being the number of correctable errors, $u$ being the number of uncorrectable errors, and $d$ being the ...
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0answers
52 views

Is there a way to see video after applying packet loss

I have encoded a video stream using JM using RTP. Then i have applied rtp_loss on it but after that i am unable to decode video. Like in this example a video with different packet loss percentages are ...
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2answers
1k views

How to compute bit level soft decisions from an M-ary symbol?

When working with a decoder such as LDPC that can take in soft-decision inputs (or channel posterior probabilities as I've seen them called as well), how are these soft-decision values calculated for ...
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1answer
333 views

Important differences between BCJR and SOVA algorithms?

BCJR algorithm needs noise variance for Gamma (branch metrices) calculation. So I am wondering does SOVA (soft output Viterbi algorithm) needs noise variance?
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0answers
91 views

QC-LDPC Decoder - Is it a codeword?

I'm designing a QC-LDPC decoder in VHDL. It uses a layered decoding method - only a single block row of parity equations is evaluated each iteration (the bit values are still updated every iteration). ...
4
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1answer
3k views

QPSK soft decoding

I'm trying to decode a Hamming Block Code transmitted using a QPSK modulation. For the moment I can sucessfully decode it using hard decision but in order to improve performance I'd like to use soft ...
2
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1answer
276 views

extended hamming code

for the (7,4) Hamming code, I know how to decode a codeword using the syndrome decoding method, by just using the 3 parity bits, and it is correctable if there is just 1 error. However, for the (8,4) ...
4
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3answers
3k views

Why is an interleaver often placed between an outer block code and an inner convolution code?

It seems that when doing FEC with a concatenated-code, an interleaver is often placed between the outer block code and the inner convolution code. The explanations I've seen say that this is because ...
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1answer
3k views

How to compute generator matrix from a parity check matrix?

I have a parity matrix ("H") that is not in canonical form (the identity matrix is not on the right side). I'm trying to programatically calculate the generator matrix ("G") from it. The Wikipedia ...
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1answer
345 views

Viterbi Decoder - Decoding Continuously Encoded Stream Partially

I am in trouble with Viterbi decoder for a while. I have some questions. I need to decode messages from a continuous stream which is encoded without resetting the state metrics. Each message starts ...
8
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2answers
1k views

Deep space communications BER and FEC?

What kind of bit error rate do they get from deep space communications (Pioneer, Voyager, et.al.), and what kind of modulation and FEC allows them to recover messages with that microscopic level of ...