System Design for Cognitive Radio Conmunications

The rising number and capacity requirements of radio systems bring about an increasing demand for frequency spectrum. Cognitive radio offers a tempting solution to this problem by proposing opportunistic usage of frequency bands that are not occupied by their licensed users. Since it is a rather new concept, there is no consensus on the practical implementation of cognitive radio communications. In this paper, a comprehensive system design for cognitive radio is presented. The details of spectrum sensing and dynamic spectrum shaping, which constitute the basics of opportunistic spectrum usage, are given. It is proposed to transmit the spectrum sensing related information via on-off keying (OOK) modulated ultrawideband (UWB). The limits on the range of one-to-one cognitive communications are discussed. A processing gain based approach that leads to an increased range for cognitive networks is proposed. Different signaling options for the real data communications are given, and among these options an impulse radio that employs raised cosine filters is investigated in detail