Capacity of blockwise noncoherent M-APSK/AWGN channel

Capacity-achieving input distribution for the blockwise noncoherent M-APSK/AWGN channel is characterised. Upper and lower bounds on the normalised capacity, with and without the use of differential encoding, are derived. They show that the coherent channel capacity is approached with increasing channel coherence interval. Moreover, they indicate that the coherent capacity is approximated faster with differential encoding.