PG-Sensing: Progressive Out-of-Band Spectrum Sensing for Cognitive Radio

One of the major challenges in cognitive radio networks is to maintain the quality of service (QoS) for secondary transmissions while ensuring the protection of primary users PUs); the latter requirement is normally enabled through inband spectrum sensing. To maintain QoS of secondary traffic, a secondary user (SU) has to quickly switch to another empty spectrum band when a PU returns to its currently occupied spectrum by SU. The issue of how to quickly and accurately identify a free spectrum band when the operating spectrum band becomes unavailable is of practical interest; out-of-band spectrum sensing is a mechanism that can be leveraged for this purpose. In this paper, we propose a novel progressive out-of-band spectrum sensing (PG-Sensing) scheme that consists of two components, 1) progressive scanning which adaptively selects a subset of the available candidate spectrum bands which have a higher chance of being empty, and 2) multiband sequential shifted chi-squared test (SSCT) based searching that searches only the set of selected spectrum bands in the first step. The proposed PGsensing scheme significantly reduces the time to resume secondary transmissions thus allowing SUs to reliably and quickly switch to a free spectrum band when necessary while maintaining good QoS for PUs as well as SUs.