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Spectram-sculpting-aided interference avoidance for OFDM-based cognitive networks

This paper studies how to efficiently reduce the mutual interference between primary and secondary networks. Different to conventional cognitive system, in which primary and secondary networks have no information exchange, the media access control mechanism we propose allow an operating PU to share the length of its remaining occupation time to SUs. With the help of such information exchange, the primary network can be better protected and the secondary network has the potential to reduce the energy consumed by spectrum sensing. To realize such a dynamic information sharing, we propose a novel spectrum-sculpting-aided scheme in this paper. Specifically, the PU deliberately inserts one zero-subcarrier into its data carriers, and uses the zero-subcarrier's position to claim its status. Through two-step sensing, each SU can attain the PU's remaining operation time, and then adjust its sensing strategy to avoid interference to the PU. Analysis of interference probability, together with simulation results, clearly exhibit the advantages of the proposed scheme in terms of the mutual interference and the amount of SU's sensing times.