Spectrum Measurement in FM bands for Cognitive Radio Design using NI USRP and LabVIEW Tilty Tony(Author) Electronics and Communication Rajagiri School of Engineering and Technology Kochi, Kerala, India tiltytony04@gmail.com Jaison Jacob Electronics and Communication Rajagiri School of Engineering and Technology Kochi, Kerala, India jaisonjacob09@gmail.com Abstract— Frequency spectrum is the scarcest resource for wireless communication. The FCC has stated that there are some frequency bands that are underutilized. Hence the frequency spectrum is not scarce but it is underutilized. An efficient way to utilize the spectrum is cognitive radio. An important point for designing future systems is to gain knowledge about the occupation of the frequency bands which may be used by the cognitive radio. This includes the general characterization of the traffic density at the frequency bands as well as a detailed analysis of the temporal frequency allocation. In this paper, measurements are taken in FM band and the spectrum occupation analysis is done using USRP. Short-term and real-time measurements to enable the radio to predict occupancy is carried out based on the spectrum monitoring performed at various timings of the day. Keywords-Spectrum measurement; Spectrum Sensing; Cognitive Radio; Cognitive Radio design I. INTRODUCTION Frequency spectrum is the scarcest resource for wireless communication. The FCC has stated that there are some frequency bands that are underutilized. Hence the frequency spectrum is not scarce but it is underutilized. An efficient way to utilize the spectrum is cognitive radio. Cognitive radio makes use of spectrum holes in the band. Spectrum occupancy measurements helps to efficiently utilize the spectrum band [1]. Motivation of this paper lies in the increasing wireless demanding constrained by limited resources. The paper implements a real time spectrum occupancy measurement for 91.9 MHz ISM band using NI-USRP hardware and lab-VIEW software. LabVIEW is a powerful graphical software development environment which can be used for RF data acquisition and instrument control [4]. The measurement setup allows for analysis of white spaces in FM band. This paper is organized as follows. . Section II gives a brief overview of previous spectrum measurement studies. Section III describes the experimental setup and introduces the sensing procedure for performing spectrum measurements. Section IV combines the processing of data through acquisition and measurement and analysis setup. A preliminary analysis of the results and conclusions for using the NI USRP as a spectrum measurements device is provided in section V. Finally section VI concludes the paper. II. BACKGROUND AND RELATED WORKS The implementation simplicity of the energy detector makes it favorable candidate for spectrum sensing task. The most important advantages of the energy detection method are the relatively low computational requirements, the almost universal applicability and the fact that it doesn’t require any prior information regarding the signal that is to be detected. The received signal is passed through a filter then squared in amplitude. Average of this signal is compared with a threshold value. The main aim of related works in the area of spectrum occupancy measurements has been to gain a better understanding of the utilization of spectrum in different locations [9]. These works focused particularly on wideband spectrum measurements and investigated the related parameters such as sweep time and resolution bandwidth [3]. Although a LabVIEW-based Software -Defined Radio approach has not yet been implemented. III. MEASUREMENT SETUP AND APPROACH In the CR system, the USRP motherboard which consists of the analog-to-digital converter (ADC), digital-to-analog converter (DAC), digital up conversion (DUC) and Field Programmable Gate Array (FPGA) is used as the interface between the software, the PC and the real world, the radio frequency (RF) band. It is responsible for converting the analog signal to digital domain and vice versa. The USRP front end which is connected with the USRP motherboard is responsible for down converting the RF signal to the baseband signal for the USRP motherboard to do further processing. A. Sensing Setup The sensing setup consists of a computer/laptop, spectrum analyzer (USRP) with one omni directional antenna. National Instruments (NI) LabVIEW is installed on