What is poly2trellis function?

The poly2trellis function accepts a polynomial description of a convolutional encoder and returns the corresponding trellis structure description. This output can be used as an input to the convenc and vitdec functions.

What is constraint length in convolutional code?

Constraint Length of Convolutional Code Constraint length, k, is the size of the shift register in the memory encoder without feedback. It means how many stages are needed for the combinational logic that produces the output bits. The shift register of size k, stores the present bit and the past (k -1) bits.

Why do we use convolution codes?

The sliding nature of the convolutional codes facilitates trellis decoding using a time-invariant trellis. Time invariant trellis decoding allows convolutional codes to be maximum-likelihood soft-decision decoded with reasonable complexity. Convolutional codes are often described as continuous.

What are the advantages of convolutional codes?

The main benefits I gathered from using convolutional codes is that, it’s easy to implement and does better (than linear codes) in cases where you have higher error probability rates and noisy channels. Information bits are spread along the sequence. Lastly, these codes have memory.

What is puncturing in convolutional codes?

Puncturing is a technique that allows the encoding and decoding of higher rate codes using standard rate 1/2 encoders and decoders. The example is somewhat similar to the one that appears in Soft-Decision Decoding, which shows convolutional coding without puncturing.

How do turbo codes work?

The natural coding rate of a turbo code is R = 1/3 (three output bits for one input bit). To deal with higher coding rates, the parity bits are punctured. For instance, transmitting Y_1 and Y_2 alternately leads to R = 1/2\ . The original turbo code [BER] uses a parallel concatenation of convolutional codes.

What’s the difference between block code and convolution code?

In block codes, the data comprises of a block of data of a definite length. However, in convolutional codes, the input data bits are not divided into block but are instead fed as streams of data bits, which convolve to output bits based upon the logic function of the encoder.

What is meant by convolution code?

In telecommunication, a convolutional code is a type of error-correcting code that generates parity symbols via the sliding application of a boolean polynomial function to a data stream.