Figure 2. Constraint length (K)=7, code rate (r)=1/2 convolutional. encoder. Implementation of Convolutional Encoder and Viterbi Decoder using Verilog HDL . Implementation of Convolutional Encoder and Viterbi Decoder using VHDL. Conference Paper (PDF Available) ยท December with 2, Reads. Request PDF on ResearchGate | Paper: VHDL Implementation of Convolutional Encoder and Viterbi Decoder | In digital communication the.

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The data bit streams sent by the transmitter are conceived as a sequence of voltage samples. This employs an on-chip circuitry as part of the decoder design to accomplish testing and make decoding circuits easily testable. The shift register is initially filled with an all zero sequence and the first binary digit referring to Figure 2.

During the data transmission, suppose three of the received symbols got corrupted underlined, bold red.

The survivor path storage cknvolutional stores the corresponding bit-sequence of the lowest cost paths. Here, the output bvdataout0bvdataout1 and bdataout are in high impedence state.

An Experimental Implementation of Convolution Encoder and Viterbi Decoder by FPGA Emulation

Each stack will be run in pop mode or push mode in turn. In the secoder approach each state has a register to store the survivor path information. They are widely used in modems and digital cellular telephony. Our main task is to implement the above algorithm in FPGA.


A Path is defined as a sequence of state transitions with corresponding input and output data. Not particularly on the space channel but also in many instances on satellite channels, sufficient bandwidth is available to permit moderate bandwidth expansion.

The author has shown that the power dissipation of the registerexchange and trace-back approaches and the convoluyional dissipation of shift and selective update methods [13]. Or output contains redundant bits to reduce probability of error introduced by additive white Gaussian noise.

This procedure continues until the last input digit, for the case in Figure 1. This is the essence of the encoder system which is shown in block diagram in Figure 2.

Design and Implementation of Viterbi Decoder Using VHDL – IOPscience

The test system functions as an off-line testability with minimum sharing of decoder resources. The Viterbi algorithm is used to find the most likely path to determine the hidden input states.

A comparison can then be made by comparing the bits obtained from the Decoder Output and the M-Sequence Generator. Among the two, soft decision performs better as it can capture more information of input signal at the cost of higher complexity.

Design and Implementation of Viterbi Decoder Using VHDL

Translating block diagram in Figure 2. To get the right order of output bit stream, 2 stacks is ecnoder to push-pop the decoded bits from traceback.


Hamming distance is equal to the number of bits, a bit combination differs from the other combination [19]. We generate decoded data from calculated survival in ACS using traceback scheme.

Here, the shift registers shift to the right for each input. Thereby it becomes necessary to quantize it into several voltage levels so that it can be processed digitally. This further reduces the probability of errors in the received signal that may be corrupted by noise [13]. Here, VHDL is used throughout the whole system as well as this project. Since the received signal is a voltage, therefore it can be analog.

The Viterbi decoder is drcoder of 4 sub-units: Using these three primary components, the test system had been successful i,plementation simulate a ‘soft decision’ test data for the decoder input.

PopDataOut is the output from stack0. All the corrupted bits can be restored to their correct values during the trace-back procedure in Viterbi decoding. For concolutional message of the length L, after the initial phase of M encoded bits dk, there are L – M identical trellis segments.

Error-correcting convolution codes prove to be a powerful methodology to limit the effects of noise in digital data transmission.