Constellation diagram - Sequence

In this article let us understand that why in constellation diagram we have a sequence like 00, 01,11,10 and why not 00,01,10 and 11 .

As we know AWGN(Additive white Gaussian Noise) is predominant in the transmission systems (while we also have other noises like shot, thermal etc) .

So when we transmit the symbols using the modulation format of our choice(in the picture we have taken the example of QPSK as a reference), we encode the bits per symbol using the M-ary encoding (log2 M) .

We map these symbols using the Gray coding named in the honor of scientist Mr Frank Gray .This coding ensures a change of only 1 bit during the transition.

For example from 00->01 ( 1 bit) ,01--->11(1bit again and so on and so forth) We can conclude this with the idea that Gray coding in the constellation diagram facilitates us in error correction as an adjacent symbol error causes only one bit to be incorrect