Abstract
In this chapter, the author describes a software-defined radio (SDR)/digital signal processing (DSP)-based cognitive system that has been developed based on the universal software radio peripheral (USRP) and the GNU radio software platform to detect satellite signals. The USRP, running Ubuntu operating system, with interchangeable daughterboard, allows for a variety of experimental settings. The USRP Xilinx Vertex 3 FPGA chip can handle C++, Python, and/or VHDL device programming and configuration. The goal is to create a detector in C++ and Python to implement a cognitive system capable of recording the L1 signal from a DirecTV satellite. The GNU radio companion (GRC), an open source for building software defined radio, and Matlab/Simulink logic blocks are used to create the desired flow graph that results in building and generating the detector program. The proposed experiments explore the effects of different detection techniques, and provide some quantitative results on performance improvements via the software-defined radio approach.
TopIntroduction
This chapter details the steps taken to apply SDR/DSP algorithms to USRP to implement a satellite signal detector. One should be able to follow these steps with the specified set of hardware and software to get the same configuration on the proper USRP device. This project was implemented under the supervision of NASA scientists and faculty advisors in dedicated NASA labs. Following lessons learned here and authors’ previous experiences in data visualization and signal processing research and training relevant labs were designed to enhance the Computer Engineering program at the Virginia State University (VSU) (Sheybani, 1992, 2002, 2006, 2007, 2008, 2010, 2011, 2012, 2013, 2017; Javidi, 2008, 2010, 2014, 2015, 2017; Ouyang, 2010; Garcia-Otero, 2011; Badombena-Wanta, 2010; Ettus, 2014, 2015; Luttamaguzi, 2017; Mathworks, 2014).
The Universal Software Radio Peripheral (USRP) development technique is based on designing and implementing radio frequency (RF) based systems. The distinctiveness originates from the interchangeable daughterboard within the USRP. The system is designed around the Xilinx Vertex 3 FPGA chip. This means C++, Python, and VHDL can be used to program this device. The project description consists of creating a receiver/detector. The objective of the project is to research and comprehend the hardware functionalities of the USRP in association with the companion software/firmware (SDR, DSP, GNU, etc.) in implementing space communication systems. The purpose is to create codes in C++ and Python to implement receiving/detection capabilities of the device. The goal of this project is to design a receiver that is capable of recording the L1 signal from a DirecTV satellite (Anon, 2014; Mathworks, 2014; Ettus, 2014; Dupleich, 2013; Grimm, 2014).
Key Terms in this Chapter
DSP: It is the use of digital processing, such as by computers or more specialized digital signal processors, to perform a wide variety of signal processing operations. The signals processed in this manner are a sequence of numbers that represent samples of a continuous variable in a domain such as time, space, or frequency.
SDR: It is a radio communication system where components that have been traditionally implemented in hardware (e.g. mixers, filters, amplifiers, modulators/demodulators, detectors, etc.) are instead implemented by means of software on a personal computer or embedded system.
USRP: It is a range of software-defined radios designed and sold by Ettus Research and its parent company, National Instruments. Developed by a team led by Matt Ettus, the USRP product family is intended to be a comparatively inexpensive hardware platform for software radio, and is commonly used by research labs, universities, and hobbyists.
Communications Satellite: It is an artificial satellite that relays and amplifies radio telecommunications signals via a transponder; it creates a communication channel between a source transmitter and a receiver at different locations on Earth. Communications satellites are used for television, telephone, radio, internet, and military applications. There are over 2,000 communications satellites in Earth’s orbit, used by both private and government organizations.