Cognitive Radio System for Dynamic Allocation of Uhf Band Channels Based on 802.11AF and Using the Energy Detection Algorithm

Abstract

This paper describes the development of a cognitive radio system through a software-defined radio approach, using universal software radio peripheral (USRP) devices and digital television equipment for communication in the UHF band. The algorithm was developed in LabVIEW and is based on energy detection, where the average power of the video carrier of the tv signal is calculated and compared with the established threshold value. As a result of detection, free channels are determined and assigned for the transmission of an Secondary User (SU), which will synchronize with the receiver the same working frequency. For the evaluation of the performance tests, a DTT transmitter and receiver were used, which simulate a Primary User (PU), and when the system detects it, it releases the frequency in use of the SU and assigns another free frequency to it to guarantee continuity of trasmission service. Tests were carried out to determine the efficiency of the system, taking into account the response time of the system and its efficiency to allow coexistence of systems within the same spectrum. System response times were measured, being 1.07 s and 41.47 s the shortest and longest response time respectively, for frequency change in order to avoid interference with the PU. Using sampling techniques, the average system response time was 21.33 s, proving that the system is efficient in environments with high interference for services that are not sensitive to latency.