Abstract An efficient turbo encoding scheme is introduced in this paper, it considers unpunctured trellis-coded modulation constituent encoders. This scheme, called unpunctured turbo trellis-coded modulation (UTTCM), uses a new QAM mapping technique that considers both Ungerboeck mapping and Gray code mapping. The simulation results, over Gaussian and Rayleigh fading channels, are performed for throughput 2, 3 and 4 bits/s/Hz with 16QAM, 32QAM and 64QAM modulations, and rate 2 3 , 3 4 and 4 5 constituent TCM encoders with memory order of 4. This results show that the proposed scheme outperforms the turbo-codes scheme (TC), and with a reduced complexity of the decoder, its performance, over Gaussian channel, is within 0.4 dB from the performance of parallel concatenated trellis-coded modulation (PCTCM) at a bit error rate of 10 - 5 .