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) · December with 2, Reads. Request PDF on ResearchGate | Paper: VHDL Implementation of Convolutional Encoder and Viterbi Decoder | In digital communication the.
|Published (Last):||23 November 2013|
|PDF File Size:||2.82 Mb|
|ePub File Size:||17.21 Mb|
|Price:||Free* [*Free Regsitration Required]|
Fabian Schuh, Johannes B. The System Block Diagram for the project. Thus, the results here verified that the og system works as expected. In this way a implementatino of correlation between each sample in the signal is automatically obtained. To get the right order of output bit stream, 2 stacks is used to push-pop the decoded bits from traceback.
In addition, this chip does have another function, that is to function as a convolutional code encoder. The branch metric computation block computes the branch metrics for each deocder. A comparison can then be made by comparing the bits obtained from the Decoder Output and the M-Sequence Generator. The constraint length plays an important role in the efficiency of convolution encoder hence, it needs a better understanding.
The results obtained from synthesis, simulation and hardware testing were accurate, error-free in recovering the original information successfully.
The operation of Viterbi decoder is simulated under Mentor Graphics. For a message of the length L, after the initial phase of M encoded bits dk, there are L – M identical trellis segments. Vitwrbi is system reset.
If state h of stage j-1 store minimum path metric PMh,j-1then the minimum path metric PMi,j at state i of stage j is:. The BM unit is used to calculate branch metric for all 16 trellis branches from the input data.
By the use of differential detection technique and with the aid of a matched filter at the receiver one can easily retrieve the transmitted symbols by means of a decision-feedback equalization DFE or maximum-likelihood sequence estimation MLSE using the Viterbi algorithm . The decoder system implements the Viterbi Algorithm for decoding soft decision inputs. For the proposed work, an integration of correct hardware and software is required for device to function appropriately.
Generate decoded data by traceback reading the survival path for 4K stages. Simple Block Diagram of the Encoder System. Here, v represents the number of outputs of the encoder; k is the number of inputs of the encoder, N-1 is the number of memory elements Flip- Flops and N represents the constraint length.
Convolution codes were first introduced in by Elias as FEC coding scheme . Translating block diagram in Figure 2. Branch Metric Unit Diagram.
Design and Implementation of Viterbi Decoder Using VHDL
In maximum likelihood sense this is the most optimal algorithm for decoding of a convolution code. For simplicity for this project and to be consistent with the decoder system design, the output of the Serial-Parallel Converter is such that the first 3 bits are the most significant bit MSB of the 2-bit encoded symbols from the encoder system and the latter 3 bits are the least significant bit LSB.
Using these three primary components, the test system had been successful to simulate a ‘soft decision’ test data for the decoder input. Hence, the chip generated in this project functions as a decoder, specifically Viterbi decoder, for digital communications over noisy channels. Few categories of algorithms that already exist for such purpose are listed below:.
Design and Implementation of Viterbi Decoder Using VHDL – IOPscience
An 8 bit adder is used for path metric calculation. There are two approaches for generation of decoded output sequence, register-exchange and back-trace. During the data transmission, suppose three of the received symbols got corrupted underlined, bold red. A convolution encoder is characterized in N, k, v format. The encoder system is an essential part of the test system in which will be discussed later. Hence, a FPGA can offer a massive parallel execution thereby increasing the throughput of the program.
First, We give a brief introduction about Viterbi algorithm. With this way of configuration, the FPGA is capable of operating by itself as a Convolutional encoder or Viterbi decoder. Total 5 hierarchy levels are used. The hardware resource requirement hugely changes in response to channel noise conditions. In selective update method the survivor path information is routed by a multiplexer vydl appropriate registers.
The 2 stacks are always in different mode. Traceback is carried out in memory unit.
Hence, it gains benefit through the reuse of the same hardware. The test system functions as an off-line testability and employs an on-chip circuitry as part of the decoder design to accomplish testing and make decoding circuits easily testable. Decoding With Viterbi Algorithm: This can benefit for low power design of Forward error control approach.
The test system implements the convolutional code signals to test the decoder system which is generated by the convolutional code encoder. This system is divided into two distinct part: The above procedure can be viewed in a finite state machine with transition from the old state to the new state for a given binary input will yield 2 output coded symbols.
In the back-trace scheme, only the survivor path information for each state is stored for each code symbol. This can be realized by applying clock gating-scheme . This can be easily extricated from Figure 7.