# Need some help in bit error rate calculation for QPSK when using Gray coding

Why is Probability of Bit Error = 2 times the Probability of Symbol Error in QPSK with Gray Coding. Is it because one bit error has the potential to cause two symbol errors (2 symbols where they differ by 1 bit from the original symbol being sent) ? Or there is a more rigorous mathematical proof ?

## 1 Answer

No, it's because one channel symbol affects two adjacent payload bits.