In this paper, we derive the minimum noncoherent distance of block-coded 16QAM, and propose noncoherent block-coded 16QAM (NBC-16QAM) accordingly. Various noncoherent block coding schemes are compared via computer simulations. We find that for both NBC-16QAM and the noncoherent 16QAM scheme proposed in 2002, the curves of bit error rates do not decade exponentially. When the block length is very small, 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.

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.

In this letter, we propose three noncoherent block coded twisted amplitude and phase shift keying (NBC-TAPSK) schemes which are derived from noncoherent block-coded MPSK. We also propose a new noncoherent detector and a corresponding noncoherent distance for nonconstant-energy signals over the additive white Gaussian noise (AWGN) channel. At high data rates, NBC-8TAPSK has the best bit error performance among all noncoherent schemes.