A novel trellis-coded sequence and phase modulation (SPM) scheme is pr
esented for the direct sequence spread spectrum (DS/SS) system. As an
example, the combined two sequence and four phase-shift-keying (2-S/4-
PSK) modulation scheme is described and analysed. It is shown that the
trellis-coded SPM can obtain an additional gain of 1.1-1.2dB over cod
ed MPSK modulation.