On the error performance of 8-QAM involving a /spl pi//2-wedge-shaped decision region

In this paper, the error performance of an 8-QAM constellation involving a /spl pi//2-radian wedge-shaped decision region is analyzed. By rotating the orthonormal basis functions anticlockwise by /spl pi//4 radians, an exact closed-form expression for the symbol error probability over an additive white Gaussian noise channel (AWGN) is derived. Comparing the 8-QAM and 8-PSK schemes, the former yields better bit-error rate (BER) performance on the basis of equal bandwidth and the same average energy per bit.