# Questions tagged [viterbi-algorithm]

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### What happens when the Viterbi trellis is full?

When the Viterbi trellis traceback is completely filled, but more encoded data needs to be processed, what happens? Is the oldest states in the trellis removed, with their decoded bit(s) extracted ...
• 11
88 views

### Why is my Hard Decision Decoding of Convolutional codes not performing well?

I am encoding and decoding a randomly generated bitstream of data using a [5 7] convolutional code. For the decoding part I am using a Viterbi Decoder and trying both HDD and SDD. However, my results ...
39 views

### Understanding Baum's auxiliary function used in Hidden Markov Model

I am studying HMM from "Fundamentals of Speech Recognition" by Rabiner. Regarding the problem of how to adjust the parameters of a HMM, the proposed method was Baum Welch method (Expectation-...
12 views

### Exact computation cost using Forward Procedure for HMM probability evaluation

I am understanding the HMM concept for Speech Recognition. One of the three problems (HMM) to be solved is Probability evaluation $P(O|\lambda)$. Instead of a straightforward approach which is ...
1 vote
67 views

### Maximum Likelihood for Colored Noise: Implementing using Viterbi Algorithm

I have a question regarding the ML estimation in presence of colored noise, i.e., Additive Colored Gaussian Noise. I want to implement this using a Viterbi algorithm, since I need to take the '...
• 121
256 views

### Viterbi decoder K=3 using ADD-COMPARE-SELECT Operation

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. I'm reading from book : digital communications bernard ...
1k views

### GnuRadio CC Decoder or How to use FEC Extended Decoder

I am currently trying to recover a satellite signal, encoded following CCSDS standards. This includes a convolutional code with rate 1/2 and constraint length 7. I am receiving the signal through an ...
• 33
280 views

### Help understanding ka9q viterbi27 streaming operation

I'm working to implement a k=7, r=1/2 convolutional code and Viterbi decoder for forward error correction. I want to operate in streaming mode, so that can pull data from the stream before the entire ...
65 views

### Problem with 1st order PLL update equation

The output of a communication channel is given by: $x(t) = \sum_n{a_n}h(t-nT)$, where $\{a_n\}$ are BPSK symbols, $h(t)$ is the channel response, and $T$ is the symbol period. If there is an ...
• 233
122 views

### 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 ...
427 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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1 vote
83 views

### convolutional coding with higher order QAM

I've implemented a simple 1/2 rate convolutional code and a viterbi decoder algorithm. I followed the most-common type of convolutional coding implementation I could find by googling: 1 input bit gets ...
• 467
19 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 ...
431 views

### Viterbi Algorithm - Selecting survivor paths which both contain the same Hamming distance

To my (limited) knowledge, when determining which survivor path to choose to produce an error-corrected output of a binary Viterbi decoder, the path with the smallest Hamming distance is the most ...
1 vote
153 views

### Convolutional FEC decoding - is it necessary to know where a decoding block begins and ends with convolutional codes?

I understand that the difference between convolutional and block-based FEC is that convolutional codes can be used in a continuous stream – however every implementation I saw still uses blocks. So I ...
• 13
1 vote
71 views

### Viterbi equalization of Fibonacci coding

I'm working a Viterbi equalizer for a BPSK signal which uses Fibonacci coding. In the more theoretical descriptions of the Viterbi algorithm I've read, there's a term for the probability of a ...
• 417
349 views

### Determining pulse shape for Viterbi Equalization

I believe I understand well enough how the Viterbi algorithm can reverse the effects of ISI when the combined impulse response (transmit filter, multipath, receive filter) is known. I've read How I ...
• 417
498 views

### Applying Viterbi algorithm to compensate for ISI in PSK31

I am implementing a receiver for the amateur radio mode PSK31. It is effectively a BPSK modulation with a pulse shape of a raised cosine twice the width of one symbol. Here are four consecutive pulses,...
• 417
264 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?
• 337
471 views

### Decoding final bits with viterbi

I'm writing a viterbi decoder and I'm rather confused about the correct process of decoding the final k bits for a kth order ...
1 vote
101 views

### State definition in Viterbi Algorithm?

An ISI channel of length 'L+1' $\mathbf{h}=[h_0 \space h_1 \space … \space h_L]$can always be modeled as a finite state machine(FSM) of memory 'L'. For a binary input $x\in\{+1,-1\}$,a state can be ...
• 187
126 views

### Performance of Viterbi detector over non-minimum phase channels

For sequences that are transmitted over channels with memory $\mu=n$ and response H=$[h_0 h_1 \ldots h_n]$,Viterbi algorithm implements Maximum Likelihood (ML) detection and BCJR implements Maximum A-...
• 187
412 views

### Viterbi Decoder=1/2 k=4 [closed]

Woud anyone have a viterbi decoding tool or c-code or .m file for (R=1/2, K=4)? I am trying to decode a bitstream received in RFSTUDIO from a non-TI transceiver and it says that it uses this kind of ...
1k views

### Viterbi equalizer in a GSM system

I'm about to tackle implementing a Viterbi equalizer fo a GSM system in gnuradio. I went through the internet and ieeexplore and I think that this document explains it best: Application of Viterbi ...
• 61
83 views

### Does the input data have to be passed through the Baum-Welsh function to compute the Viterbi decoder?

I'm using a Hidden Markov Model in order to train an application for gesture recognition. Currently, I have gathered samples, and, using a library have trained these values (They have been passed ...
• 485
4k 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 ...
• 223
309 views

### Most efficient algorithm for comparing two paths

I'm working with a Continuous Hidden Markov Model, and using the Viterbi Decoder which finds the best possible path for a given sequence. Here is how my algorithm works: ...
• 485
Does converting zeros into ones and ones into zeros in the input stream affect the decoding result? Empirically I have seen that it does not affect, decoding $[0 1 0 1 \ldots]$ and $[1 0 1 0 \ldots]$ ...