The goal of the research is to determine the fundamental, information theoretic limits of when and how to layer multiple wireless networks on shared and/or unlicensed bands in a seamless and spectrally efficient manner. Wireless networks are everywhere: WiFi, Bluetooth, cordless phones populate increasingly dense unlicensed frequency bands. Cellular, satellite, military and first-responder networks occupy exclusively licensed bands that are gradually giving way to dynamic, secondary spectrum sharing forms of licensing. For both types of licensing, it is crucial that multiple wireless networks co-exist in the same finite spectral resources in an intelligent, efficient and scalable manner. The time is ripe for a fresh look at how to optimally layer wireless networks, reaching far-beyond today's ``interference-limited'' solutions which combine orthogonal access and the treatment of interference as noise.
The research moves away from classical information theoretic single-layer, homogeneous networks to include realistic oblivion constraints on how different layers should interact in a hierarchical fashion. Understanding how to best layer networks constitutes a major step towards eliminating current spectral inefficiencies. The fundamental bounds on the performance of layered networks developed will reveal when incentives for networks to adopt a layered policy exist, which is expected to significantly impact the design of future networks. Both distributed and centralized layered networks are investigated, with goals to: 1) develop a structured framework for layered networks, 2) derive capacity regions for deterministic layered networks and associated Gaussian layered networks to within a constant gap, 3) understand layered networks through asymptotic metrics by considering the generalized degrees of freedom of the layered network, the throughput scaling laws with number of nodes in each layer, and the throughput scaling law with number of layers.
