Commonalities of several modulation techniques

We study commonalities of new bandwidth efficient and power efficient quadrature-quadrature phase shift keying (Q/sup 2/PSK), constant envelope Q/sup 2/PSK (CEQ/sup 2/PSK), rotative QPSK (RQPSK), frequency and phase shift keying (FPSK), expurgated FPSK (E-FPSK), and the well-known orthogonal frequency division multiplexing (OFDM) (or multicarrier modulation) and L-orthogonal (LO) signaling on AWGN channels. "Identical" systems are defined as systems that have the same bit error rate (BER) versus the bit energy to noise ratio function and the same power spectral density. The results show that: (a) Q/sup 2/PSK, FPSK, and OFDM are "identical", and (b) CEQ/sup 2/PSK, E/sub 4/-FPSK and LO are "identical". Also, a mistake in an article by Fleisher and Qu (see IEEE J. Select. Areas Commun., vol.10, no.8, p.1243-1253, 1992) is corrected.