The Convolutional Encoder block encodes a sequence of binary input vectors to produce a sequence of binary output vectors. This parameter is a MATLAB ® structure whose format is described in Trellis Description of a Convolutional Code. You can use this parameter field in two ways. The puncture vector is a pattern of 1s and 0s where the. A GENERALAZED CONVOLUTION COMPUTING CODE IN MATLAB WITHOUT USING MATLAB BUILTIN FUNCTION conv(x,h). I runned the aghil vinayak program got output but t is 1*6.
Why we need an encoder
C/C++: Convolution Source Code. In mathematics and, in particular, functional analysis, convolution is a mathematical operation on two functions f and g, producing a third function that is typically viewed as a modified version of one of the original functions (from wikipedia.com). Code = convenc(msg,trellis) code = convenc(msg. Code = convenc(msg,trellis) encodes the binary vector msg using the convolutional encoder whose MATLAB trellis structure is trellis. For details about MATLAB trellis. Is the same as the syntax above, except that it specifies a puncture pattern, puncpat, to allow higher rate.
In the communication link, the noise, multipath effect and all the other effects that affect the communication can induce errors on the communication link. In this post, we already addressed the topic introducing the Reed-Solomon encoder.
Here we want to exploit another encoder widely used in communication link: Convolutional Encoder.
After a brief introduction to the Convolutional encoder, we will go to see the thing that interests us the most, I mean the VHDL implementation of a Convolutional Encoder.
Convolutional Encoder Architecture
When we talk about encoders, we can classify the channel coding in two main categories:
BLOCK CODING:
- Cyclic codes
- BCH
- Product Turbo code
- LDPC
TRELLIS CODING:
- Convolutional coding
- TCM (Trellis Code Modulation)
- Turbo codes (SCCC or PCCC)
- Turbo TCM
In this post, we are going to analyze the architecture of the Convolutional Encoder used in DVB-S standard and its implementation in VHDL.
The convolutional encoder is based on a rate 1/2 mother convolutional code with constraint length K = 7 corresponding to 64 trellis states.
The input serial stream is encoded in two branch X and Y with the following polynomial:
- X output (171 octal)
- Y output (133 octal)
Figure 2 reports the encoder architecture.
VHDL implementation of Convolutional Encoder
Figure 2 shows the classical architecture of a convolutional encoder.
The VHDL implementation is straightforward. Just implement the delay line end the two branches with XOR as below.
VHDL Simulation of Convolutional Encoder
In order to verify the VHDL implementation of the convolutional encoder, the best thing is to simulate the VHDL code and compare the encoder output with a reference pattern.
What is the best way to generate a reference I/O pattern?
Matlab or Octave give us the possibility to generate a reference pattern for the convolutional encoder.
Here below an example of Matlab/Octave command used in the generation of the reference matching vector:
In Figure 3, the yellow “error_flag” signal is used to simplify the matching between the output of the Convolutional Encoder VHDL module and the reference Matlab test vector.
The input and output data to the convolutional encoder is read from the reference file and run-time verified during the VHDL simulation.
Layout of Convolutional Encoder
Figure 4 reports the RTL view of the VHDL code presented above.
In the figure is highlighted the XOR function for X and Y branch.
C Program For Convolutional Code Matlab Pattern Free
Conclusion
In this post, we have presented the convolutional encoder general architecture. A VHDL example of a Convolutional encoder has been tailored to the general architecture.
![C program for convolutional code matlab pattern download C program for convolutional code matlab pattern download](/uploads/1/2/4/7/124799891/836963229.jpg)
The Matlab/Octave script provided can be used to generate reference vector for VHDL matching.
References
[1] https://www.altera.com/
[2] https://www.mathworks.com/
[3] http://www.scilab.org
[4] https://www.gnu.org/software/octave/
[5] https://en.wikipedia.org/wiki/Convolutional_code
[6] “Channel coding: Convolutional codes” Vahid Meghdadi, University of Limoges
[7] Digital Video Broadcasting (DVB); Framing structure, channel coding and modulation for 11/12 GHz satellite services EN 300 421 V1.1.2
Properties
Code For Matlab Functions
TrellisStructure
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Trellis structure of convolutional code
Specify trellis as a MATLAB® structure that contains thetrellis description of the convolutional code. The default is theresult of
. Use the istrellis functionto check if a structure is a valid trellis structure.
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TerminationMethod
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Termination method of encoded frame
Specify how the encoded frame is terminated as one of
Truncated | Terminated .The default is Truncated . When you set this propertyto Truncated , the object assumes that the encoderstops after encoding the last symbol in the input frame. When youset this property to Terminated the object assumesthat the encoder forces the trellis to end each frame in the all-zerosstate by encoding additional symbols. If you use the comm.ConvolutionalEncoder System object togenerate the encoded frame, the TerminationMethod valuesof both encoder and decoder objects must match.
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Algorithm
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Decoding algorithm
Specify the decoding algorithm that the object uses as one of
TrueAPP | Max* | Max .The default is Max* . When you set this propertyto True APP , the object implements true a posterioriprobability decoding. When you set the property to any other value,the object uses approximations to increase the speed of the computations.
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NumScalingBits
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Number of scaling bits
Specify the number of bits the decoder uses to scale the inputdata to avoid losing precision during the computations. The defaultis
3 . The decoder multiplies the input by 2NumScalingBits anddivides the pre-output by the same factor. This property must be ascalar integer between 0 and 8 .This property applies when you set the Algorithm property to Max* . Regedit tricks pdf free downloads.
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CodedBitLLROutputPort
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Enable coded-bit LLR output
Set this property to
false to disable thesecond output of the decoding step method. The default is true .
It could either show a single path, or all of the various paths, through the use case, starting with an actor (user, external system, event) initiating some kind of action. State diagrams show the various states that are valid for an object (which could be anything from a method to a class to the system as a whole). A sequence diagram typically shows the execution of a particular use case for the application and the objects (as in instances of a class) that are involved in carrying out that use case. Activity diagram adalah.
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