An Experimental Approach to Spectrum Sensing in Cognitive Radio Networks with Off-the-Shelf IEEE 802.11 Devices

Abstract

Spectrum sensing is essential to the realization of spectrum agility in cognitive radio (CR) networks. Although fundamental tradeoffs and theoretical limits associated with spectrum sensing have been studied extensively, there have been very few experimental studies focused on building a spectrum "sensor" with commercial off-the-shelf devices. We have therefore built a prototype of CR-based sensor implementation with off-the-shelf IEEE 802.11 devices. 1 In particular, we have explored issues in implementing a spectrum sensor, mostly at the MAC layer, as well as the difficulty in implanting sensing functions into industrial network interfaces. Our experimental results demonstrate the feasibility of building a spectrum sensor and the construction of an incumbent-detection mechanism with off-the-shelf devices. We have also identified technical difficulties, such as device-dependency in determining the detection threshold, in-band signal jamming between secondary devices, and adjacent channel interference due to out-of-band signal emission. This experimental experience has led us to suggest a sensor design guideline for commercial wireless interfaces which can also facilitate other CR-related research.