| Communication over the noncoherent additive white Gaussian noise (AWGN) channel is considered, where the transmitted signal undergoes a phase rotation, unknown to the transmitter and the receiver. The effects of phase dynamics are explicitly taken into account by considering a block-independent model for the phase process.; Two main problems regarding this channel are investigated in this work. The first is the design and analysis of practical powerful codes whose performance is close to the theoretical limit. The second, more theoretical problem, is finding the fundamental limits of communication over this channel.; Code design is initiated with a practical and intuitive coding scheme that uses pilot symbols to facilitate phase estimation and effectively translate the noncoherent channel into the coherent AWGN channel. This coding scheme is analyzed using a recently discovered technique, called density evolution, and the inherent trade-off associated with the pilot-power is quantified.; We consider a theoretical aspect of communication problem by analyzing the information capacity and the structure of the capacity achieving signaling scheme. In particular, the capacity achieving input distribution is characterized; it is shown that the maximizing density has circular symmetry, is discrete in amplitude with infinite number of mass points and always has a mass point at zero. Furthermore, asymptotic expressions show that the probability of a mass point is decreasing double exponentially with its amplitude. Based on these results, the capacity is evaluated through numerical optimizations for unconstrained and modulation-constrained input distributions.; Inspired by the capacity results, two novel classes of coding and modulation schemes are proposed for fast and moderate phase dynamics. In the case of fast phase dynamics, optimized modulation alphabets are designed in conjunction with simple serially concatenated convolutional codes, and show close-to-capacity performance with reasonable overall complexity. In the case of moderate phase dynamics, specially designed modulation alphabets that have linear complexity with block length, are utilized together with optimized irregular low-density parity-check codes. Simulation results show that these codes can achieve close-to-capacity performance with moderate complexity, and outperform the best known codes so far. |
