A Static Spectrum Aggregation Algorithm in Cognitive Radio System

Cognitive radio （CR） is known as an intelligent technology allowing a secondary user （SU） to occupy a primary user＇ s （PU＇ s） band when it is idle. Appearance of the idle band may be contignous or non-contiguous. In other words, the PU＇ s band and the idle band are distributed alternately over the spectrum. Apparently the non-contignous idle band cannot be fully utihzed in this context. This paper proposes an algorithm to solve the problem of low utihzation of the non-contignous idle band and to increase the number of the SU who needs access to the spectrum by a static spectrum aggregation （SSA） method combined with non-contiguous orthogonal frequency division multiplexing （NC-OFDM）. The simulation results show that the SSA algorithm realizes at least 70% utilization of the idle band which provides access to the spectrum for as many as 30 SUs as expected.