Implementation and performance of an opportunistic cognitive radio system

This paper presents part of the experimental results obtained during the French national research project GRACE, which deals with opportunistic cognitive radio and spectrum management. The consortium, composed by French big- and small-size companies and research institutes, proposes a cognitive orthogonal frequency division multiplexing (OFDM) signal based on IEEE 802.16e standard, with time-windowing and dynamic spectrum adaptation. An experimental setup comprising a primary link and a secondary, cognitive, link was used to emulate the operation of an opportunistic cognitive system in presence of narrowband high-priority signals. In this paper, we present the experimental setup and report the experimental results related to a sensing algorithm, a time-synchronization procedure and a reconfiguration algorithm proposed by the consortium. Other conclusions drawn from the measurement campaign are quickly introduced, but not fully presented here due to lack of space.