Energy-efficiency analysis of cooperative sensing schemes in ad hoc WLAN cognitive radios

Abstract

Wi-Fi has become a ubiquitous wireless technology in a relatively short period of time. Each of us has a wireless gadget competing for the Wi-Fi bandwidth and thus has to compromise on the data speeds in order to share the limited Wi-Fi spectrum. Contrary to this Wi-Fi crowding phenomenon which is yet to worsen with the ongoing explosive growth of wireless devices, studies show that 90% of the time, spectrum designated to legacy technologies like the television (TV) spectrum was found to be unoccupied and not every channel was in use always. Cognitive Radio (CR) Technology is the riposte to this dichotomy. A CR is an intelligent device which scans the radio spectrum for free channels and uses them to its own advantage. However, in order to access the vacant spectrum and reap the benefits, the CRs need to coordinate among themselves using cooperative spectrum sensing schemes. This thesis work studies and analyzes the energy efficiency of two such generic cooperative sensing schemes - Distributed and Centralized, in an ad hoc WLAN backdrop. Furthermore, the corresponding enhanced and adaptive versions of these two schemes are proposed, where only a fraction of the nodes scan as opposed to all nodes in the network. Using an analytical energy model for sensing, the energy costs of the proposed cooperative sensing schemes are quantified. A comparative numerical analysis is further performed to demonstrate the amount of energy savings of the proposed schemes over their generic counterparts and non-cooperative schemes.