Average bit error and symbol energy

1. What is the relation between bit energy and symbol energy?
2. What is the relation between BER and symbol error rate?

What is the relation between bit energy and symbol energy?

Because each symbol carries 2 bits, the average energy per bit is E_b = E_av /2=A².

What is the relation between BER and symbol error rate?

Consequently, the BER is approximated by the symbol error rate (SER) divided by the number of bits per symbol b. where BPSK and QPSK have the same BER because a QPSK signal can be seen as two independent BPSK signals.