The section labeled soft decisions uses an eightregion partition in the quantizing encoder block to prepare for 3bit softdecision decoding using the viterbi decoder block. The following matlab project contains the source code and matlab examples used for convolutional encoder and hard decision viterbi decoder. The llr values computed by the demodulator are multiplied by 1 to map them to the right quantizer index for use with viterbi decoder. Hard decision decoding takes a stream of bits say from the threshold detector stage of a receiver, where each bit is considered definitely one or zero. Use matlab function pwelch to find power spectral density or do it yourself. Specify the trellis as a matlab structure that contains the trellis description of the convolutional code. The following two example models showcase the fixedpoint viterbi decoder block used for both hard and soft decision convolutional decoding. The labels on the branches indicate branch metrics. This object uses the viterbi algorithm to decode convolutionally encoded input data. Viterbi decoder mathworks makers of matlab and simulink.

I need to use convoultional encoder with code rate 12 or 34 with puncturing and the decode the data using vitdec soft decision viterbi decoder with no quantization i am writing the code but i have mistake in vitdec stage. One approach is called hard decision decoding which uses hamming distance as a metric to perform the decoding operation, whereas, the soft decision decoding uses euclidean distance as a metric. If you are reading this reference page in the matlab help browser, click fixedpoint harddecision viterbi decoding and fixedpoint softdecision viterbi. Soft decisions for dqpsk demodulation for the viterbi decoding of the convolutional codes thushara c. The section labeled hard decisions uses a tworegion partition to prepare for harddecision viterbi decoding. Soft decision viterbi decoding with puncturing in matlab. Implementation of the soft input soft output viterbi algorithm sova decoder.

The model shows hdl code generation for a fixedpoint viterbi decoder block used in soft decision convolutional decoding. The snr of my signal in question is high enough that the outputs of the two should be the same. The complexity of a viterbi decoder increases rapidly with the code rate. Performs softdecison viterbi decoding with puncturing over an awgn channel using simulinkr. Soft decision viterbi decoder input community forums. Softdecision viterbi decoding with puncturing matlab central. You can specify additional namevalue pair arguments in any order as name1,value1.

This model shows how to use the convolutional encoder and viterbi decoder blocks to simulate a punctured coding system. The modulation used is bpsk and the channel is assumed to be awgn alone. Viterbi decoder file exchange matlab central mathworks. In a harddecision viterbi decoder, the bmu design is straightforward since the bms are the hamming distances between the received code words and expected branches. Soft decisions for dqpsk demodulation for the viterbi. Unquantized decoding, where the decoder inputs are real values, though better in terms of ber, is not practically viable. Viterbi decoder matlab codes and scripts downloads free. Soft input soft output viterbi algorithm file exchange matlab. Specify the format of the input to the decoder as unquantized hard soft. Soft decision decoding is used for the maximum likelihood decoding, when the data is transmitted over the gaussian channel. As expected, the soft decision decoding produces the best results. Puncturing is a technique that allows the encoding and decoding of higher rate.

Performance analysis of softdecision and harddecision. The viterbidecoder object decodes input symbols to produce binary output symbols. Block interleaving for soft decision viterbi decoding in ofdm systems van duc nguyen and hanspeter kuchenbecker university of hannover, institut f ur allgemeine nachrichtentechnik appelstr. This example shows the ber performance improvement for qpsk modulation when using loglikelihood ratio llr instead of hard decision demodulation in a convolutionally coded communication link. A viterbi decoder that is set up for soft decision decoding processes these quantized values. For a softdecision viterbi decoder, the received code words are. With llr demodulation, one can use the viterbi decoder either in the unquantized decoding mode or the soft decision decoding mode. The following two example models showcase the fixedpoint viterbi decoder block used for both hard and softdecision convolutional decoding. The behavior simulation system was looped until 100 data bit errors were detected or. In this letter, a softdecision viterbi algorithm sova combined with lowdensity parity check is investigated to achieve high chromatic dispersion tolerance and alleviate the high optical signal. It is necessary for turbodecoding and turbolike decoding. The convolutional encoder and the viterbi decoder are not at all efficient, since it uses many if and forloops. Softdecision viterbi decoder matlab answers matlab.

This matlab function decodes each symbol of the codedin input by using the. Puncturing is a technique that allows the encoding and decoding of higher rate codes using standard rate 12 encoders and decoders. Soft viterbi decoder the viterbi decoder can be either hard or soft decision decoding22. Use the convolutional encoder and viterbi decoder system objects to simulate a punctured coding system. Implementation of soft decision viterbi decoder based on a. Implements soft decision viterbi decoding for a rate 34 code over an awgn channel using simulinkr. Im having trouble getting the output of a soft decision decoder to be the same as a hard decision decoder. There are hard decision and soft decision viterbi decoders.

I bought your book but i couldnt find this code in it. This packet is a is95 baseband simulation for 1 data channel of 9. Soft decisions for dqpsk demodulation for the viterbi decoding of the convolutional codes conference paper in acoustics, speech, and signal processing, 1988. Softdecision decoders are often used in viterbi decoders and turbo code. Convolutional encoder and hard decision viterbi decoder in. Implements softdecision viterbi decoding for a rate 34 code over an awgn channel using simulink. Index termsviterbi algorithm, softinput softoutput algorithm i. Simply the hard decision decides whether the received bit is a one or zero by setting the. To meet the requirement for fec with a large coding gain, the soft decision viterbi decoding will continue to play an important role in the future.

Convolutional and turbo encoding and decoding, app, posteriori, viterbi, and binary, octal, or trellis. In two previous posts, we have discussed convolutional coding and the associated hard decision viterbi decoding. Highrate punctured convolutional codes for soft decision viterbi decoding. Block interleaving for soft decision viterbi decoding in. Implements softdecision viterbi decoding for a rate 34 code over an awgn channel using simulinkr. I am confusing that what input we will give to viterbi decoder. The exact boundaries of the quantizer are empirically determined here. Specify the trellis as a matlab structure that contains the trellis description of. Convolutionally decode binary data by using viterbi algorithm. A soft decision viterbi decoder receives a bitstream containing information about the reliability of each received symbol. Convolutional coding an overview sciencedirect topics. As this matlab function input requires soft decisions only in these 7,6,5,4,3,2,1,0 range. The following matlab project contains the source code and matlab examples used for soft decision viterbi decoding with puncturing.

Introduction he softoutput decoding algorithms is becoming a standard tool in communication receivers. Ive attached a matrix of 4bit quantized signalsundertest each signal is a column and a script im using to compare the decoded outputs. A hardware implementation of the soft output viterbi. A viterbi algorithm with softdecision outputs and its. This model shows how to use the convolutional encoder and viterbi decoder. Each value in fmetric represents the final state metric of the corresponding decoder state. In this post lets extent viterbi decoding algorithm to soft input decision scheme. A hard decision viterbi decoder receives a simple bitstream on its input, and a hamming distance is used as a metric. Syntax for soft decision decoding it gives you the confidence interval 0 to 2nsdec or quantization 3bit or 5 bit for example. Convolutional encoder of code rate12, with 3 memory elements and a corresponding hard decision viterbi decoder. Soft decision viterbi decoder input hi, i am going to use viterbi ip core in trellis mode. Click here to download matlab octave script for computing ber for bpsk with awgn in soft decision viterbi decoding. Softdecision viterbi decoding with puncturing file.

Estimate bit error rate ber performance for harddecision and. Constrain length is three for both viterbi hard decision decoding method and viterbi soft decision decoding method. Viterbidecoder creates a viterbi decoder system object, h. Matlab code for lte convolutional code and viterbi decoder matlab,code,for,lte,convolutional,code,and,viterbi,decoder. In contrast to the situation in lesson 5 we assume now that the demodulator outputs a graded multilevel confidence measure concerning the. Hewavithana and mike brookes department of electrical and electronic engineering imperial college, exhibition road, london sw7 2bt, uk abstract the conventional soft decision algorithm for dqpsk uses. Download viterbi decoder matlab source codes, viterbi. Viterbi decoding of convolutional codes gaussianwaves. Therefore, a softdecision decoder will typically perform better in the presence of corrupted data than its harddecision counterpart. Well, i am facing a problem that how to apply the depuncturing to the soft decisions 7,6,5,4,3,2,1,0 to decode properly. With llr demodulation, one can use the viterbi decoder either in the unquantized decoding mode or the softdecision decoding mode. Soft decision decoding also sometimes known as soft input viterbi decoding builds on this observation.

It does not digitize the incoming samples prior to decoding. Abstract in this paper, frequency and time interleav. Rather, it uses a continuous function of the analog sample as the input to the decoder. Estimate ber for hard and soft decision viterbi decoding. Viterbi decode the signals using hard and unquantized methods calculate the number of bit errors the while loop continues to process data until either 100 errors are encountered or 10 7 bits are transmitted. The simulation ends after processing 100 bit errors or 10. On the contrary to the hard decision the demodulator. Matlab code for lte convolutional code and viterbi decoder. If you are reading this reference page in the matlab help browser, click fixed point harddecision viterbi decoding and fixedpoint softdecision viterbi.

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