# Write a convolutional code in matlab

It is also a programming language, and is one of the easiest programming languages for writing mathematical programs. Trellis diagram is one of the method used in viterbi decoding.

### Convolutional encoder simulation matlab

The predecessor state for State , which is State , is the same as the predecessor state for State ! If the target number of errors or maximum number of transmissions you specify for the simulation are too small, the curve fitting algorithm might fail. For each state transition, the number on the arc shows the branch metric for that transition. Let the input sequence be For the first time instant, to save these results as "accumulated error metric" values, associated with states. Other MathWorks country sites are not optimized for visits from your location. Once this information is built up, the Viterbi decoder is ready to recreate the sequence of bits that were input to the convolutional encoder when the message was encoded for transmission. Note that for an n, 1, m code, there are only two branches leaving each state. The accumulated error metric values for the other two states are undefined. The final binary output of the encoder is thus 00 11 10 00 01 10 01 11 11 10 00 10 11 00 11 10

But if the input bit is a one, the encoder transitions to the state at the next clock edge. The output sequence at each stage is determined by the input bit and the two previous input bits.

The complexity of a Viterbi decoder increases rapidly with the code rate. The Hamming distance or other metric values we compute at each time instant for the paths between the states at the previous time instant and the states at the current time instant are called branch metrics. The octal numbers 7 and 5 represent the code generator polynomials, which when read in binary and correspond to the shift register connections to the upper and lower modulo-two adders, respectively.

The inputs to the bottom modulo-two adder are 10 2, so the output is also a one. Convolutional codes are used for real time implementation because they can be encoded and decoded simultaneously.

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