A Novel Expanded 16-Dimensional Constant Envelope QPSK Constellation

We introduce a 16-dimensional constant-amplitude constellation that is generated by concatenating either four constant envelope quadrature-quadrature phase shift keying (CEQPSK) symbols from Saha and Birdsall or four CEQPSK symbols recently discovered by Cartwright and also introduced here. Our new constellation doubles the number of points available for data transmission without decreasing the distance between points or increasing energy, and may therefore be used in a trellis coded modulation (TCM) system without constellation expansion penalty. Because the new constellation has constant envelope, the modulation scheme becomes very attractive for nonlinear channels such as the magnetic recording channel or the satellite channel with traveling wave tube amplifiers. Keywords—Multidimensional constellation, constant envelope, quadrature-quadrature phase shift keying, constellation expansion, trellis coded modulation.