EXPERIMENTATION OF MODULATION SCHEMES ON USRP

Abstract

Digital Communication is the transfer of digitized data from one point to another. There are multiple modulation schemes which are being used in digital communication. To understand these modulation schemes properly engineers mainly use simulators like MATLAB. Hardware implementation of these modulation schemes is a challenging task but technology has made it easier through Software Defined Radios. The current technology is moving towards software defined solutions for hardware systems. A Software Defined Radio (SDR) is a radio system with software based implementation of hardware components and is equipped with the ability to tune to different frequency bands. SDRs are used to transmit and receive data using different modulation schemes, as well as different physical parameters, across a large frequency spectrum, by using hardware that can be programmed and powerful software. An SDR performs significant amounts of signal processing using a Field-Programmable Gate Array (FPGA) or components of digital electronics that can be reconfigured. A combination of both can, also, be used. This work aims to investigate the possibility of employing the GNU Radio Companion, an open source SDR implementation, and the Universal Software Radio Peripheral (USRP), a hardware platform for SDRs, to implement transmitter and receiver of different modulation schemes. Transmitters and receivers of different modulation schemes has been implemented in GNU Radio and tested over SDRs. Data for channels in line of sight and non-line of sight has been collected using this setup. Each transmitter and receiver has been tested over different frequencies in different scenarios. There were some problems which we have faced during implementation of all these modulation schemes and solved. To maximize the performance of developed systems we investigate filters and channel estimation techniques. All the modulation schemes systems have been simulated in GNU Radio and tested on N200 SDR kit and are giving good results.