Distance based utilization of licensed spectrum in cognitive radio

摘要

For a cognitive radio (CR) system, the process of spectrum sensing has lot of importance. The objective of CR is to improve the utilization of unused spectrum band while ensuring sufficient protection to the primary users (PUs). If sensing and transmission take place simultaneously, the CR efficiency can substantially be improved. The energy detection scheme is a highly used sensing scheme. In this scheme, the value of threshold is selected mainly under a given false alarm probability (P̅) or detection probability (P), widely known as constant detection rate (CDR) or constant false alarm rate (CFAR) principles, respectively. However, CR becomes inefficient for the case when secondary transmitter is at sufficient distance d to the location of CR In this case, the signal to interference plus noise ratio (SINK) is larger than the value of SINR (minimum SINR value which is necessary in decoding the intended PU information). This paper proposes an approach where the CFAR and CDR principles are used opportunistically, based on the CR-PU distance. Here a novel frame structure is used in which the tasks of spectrum sensing and data transmission are executed simultaneously. In the proposed approach, the CR system achieves a significant improvement in its throughput compared to that in which the tasks of spectrum sensing and data transmission are executed alternately. Finally, simulated results are provided to validate the proposed theoretical analysis.