A quaternary constant-envelope modulation with 4-D trellis coding

Presents a coded continuous-phase constant-envelope modulation which employs a simple (QPSK-type) linear receiver followed by a decoder which operates on symbol-rate samples of the demodulated signal. In the absence of channel coding, this modulation achieves a 40% reduction of the transmitted signal bandwidth, but loses 2 dB in power efficiency with respect to MSK. Before proceeding to investigate more powerful 4-D trellis codes, the authors briefly discuss a simple form of multilevel coding which employs a single parity-check code for the bit sequence associated to the first partition level of the signal constellation. For 4-D trellis coding, the set partitioning tree is redefined in such a way as to increase the minimum distance between parallel transitions. With a 16-state 4-D trellis code, the proposed modulation outperforms MSK by 2.8 dB, while conserving a 20% reduction of the 99.9% signal bandwidth