Frequency Envelope Modulation (FEM): A Passive Approach to Universal Spectrum Recognition and Network Self-Configuration

Abstract

Cognitive radio has become a key solution for spectrum utilization issues over the last several years. Much research has focused on coexistence cognitive networks- where secondary users are vying for spectral "white space" when primary users vacate a licensed frequency band. This work will instead focus on an "open spectrum" regime, where there are no primary or secondary users, but all are provided equal access to the available band. Many cognitive medium access control (MAC) layers have been proposed to regulate the use of spectrum in a spectrum sharing regime, but most require the use of a common control channel (CCC) for information exchange. Additionally, while there is much research focusing on the spectrum sensing problem (detecting the presence of unused bands), the problem of spectrum recognition (determining the band of a signal of interest) has not received as much attention. We propose a new modulation scheme, frequency envelope modulation (FEM), that enables the creation of an open, cognitive ad hoc network. This network uses distributed spectrum sensing and information sharing to dispense with the need for a CCC. The effect of FEM on the physical layer is analyzed, as well as the network configuration time using FEM. We show that knowledge sharing via FEM reduces configuration time exponentially compared to uncoordinated scanning.