In this paper, we derive minimum noncoherent distances of block-coded TAPSK (twisted amplitude and phase shift keying) and 16QAM (quadrature-amplitude modulation), both using linear component codes. According to the derived distances, noncoherent block-coded TAPSK (NBC-TAPSK) and noncoherent block-coded 16QAM (NBC-16QAM) are proposed. If the block length is very small, NBC-16TAPSK performs best among all noncoherent schemes and NBC-16QAM performs worse due to its small minimum noncoherent distance. However, if the block is not short, NBC-16QAM has the best error performance because the codewords with small noncoherent distances are rare.
