Hierarchical coherent and non-coherent communication

In this paper, we propose a method for simultaneous communication of coarse and detailed information over three types of layers: two nested layers to be communicated non-coherently using Grassmannian constellations and an additional layer to be communicated coherently using unitary constellations. The layered architecture gives rise to four classes of receivers: coherent and non-coherent receivers, each operating in one of two distinct SNR regions. An operational bottleneck of this architecture is the detection complexity of these layers. To overcome this difficulty, four sequential detectors are developed. These detectors enable somewhat comparable, and in some cases identical, performance to that of their optimal maximum likelihood counterparts with significantly less computational cost.