Design and implementation of an end-to-end architecture for 3.5 GHz shared spectrum

The paradigm of shared spectrum that allows spectrum bands that are underutilized by primary owners to be exploited opportunistically by secondary devices has been a subject of intense research in recent years. The 2008 FCC rule-making allowing unlicensed use of underutilized DTV white space represented the first step in that direction and elicited similar efforts in other countries. The 2012 PCAST report [5] in the U.S. pushed this new trend further by advocating shared use of 1000 MHz of federal government spectrum with commercial systems and set the goal to release 500 MHz of spectrum by 2022. As a first step towards this goal, the FCC targeted 3550-3700 MHz band used primarily by naval radars and fixed satellite station for release. As of writing of this paper, the FCC has announced the first set of rules for this band to enable deployment of low-powered network technologies like small cells. The proposed rules require a Spectrum Access System (SAS), akin to a TV Database (TVDB) to implement an innovative three-tiered spectrum management system - dynamic incumbents in the top tier, Priority Access License (PAL) users in the second tier and Generalized Authorized Access (GAA) users in the third tier. Realizing this vision requires a new end-to-end architecture, component protocols and novel radio systems. Our paper represents a step in this direction. Specifically, we present our candidate architecture and its end-to-end implementation that includes a scalable SAS to activate dynamic exclusion zones for incumbent protection, manage primary/secondary devices and dynamically assign spectrum. We present a new protocol Protocol for Tiered Access to Shared Spectrum (PTASS) for transactions between network entities in the architecture. We also describe in detail our prototype end-to-end 3.5 GHz LTE/Wi-Fi testbed. To the best of our knowledge, this is the first paper about the 3.5 GHz shared spectrum access system and the first end-to-end trial of a live 3.5 GHz wireless communications in practice.