R Gandhiraj

Modern analog and digital communication systems development using GNU Radio with USRP

In this modern world many communication devices are highly intelligent and interconnected between each other. Any up-gradation of the hardware in the existing communication devices is not easier one. Compatibility of the new hardware with existing hardware is highly essential. But the new protocols may or may not support the older one. The solution for these problems can be provided by using the reconfigurable hardware design. The hardware can be reprogrammed according to the new change in technology up-gradation. The cost of commercially available hardware and software requirements for setting up such a module is very high. This can be solved by using Open source hardware and software such as Universal Software Radio Peripheral (USRP) and GNU Radio. This work demonstrates how the modern analog communication system like Community Radio Schemes and Radio Data System (RDS) and digital communication systems such as Simple Digital Video Broadcasting (DVB) and OFDM based data communication can be developed using the Open source hardware USRP1. This work will be helpful even for first year level of engineering students to easily implement any communication and control applications with cheaper cost.

Exploiting GNU radio and USRP: An economical test bed for real time communication systems

Communication experiments using normal lab setup, which includes more hardware and less software raises the cost of the total system. The method proposed here provides a new approach through which all the analog and digital experiments can be performed using a single hardware-USRP (Universal Software Radio Peripheral) and software-GNU Radio Companion (GRC). Initially, networking setup is formulated using SDR technology. Later on, one of the analog communication experiments is demonstrated in real time using the GNU Radio Companion, RTL-SDR and USRP. The entire communication system is less expensive as the system uses a single reprogrammable hardware and most of the focus of the system deals with the software part.

Plug-ins for GNU Radio Companion

This paper gives an insight on how to develop plug-ins (signal processing blocks) for GNU Radio Companion. GRC is on the monitoring computer and does bulk of the signal processing before transmission and after reception. The coding done in order to develop any block is discussed. A block that performs Huffman coding has been built. Huffman coding is a coding technique that gives a prefix code. A block that performs convolution coding at any desired rate using any generator polynomial has also been built. Both Huffman and Convolution coding are done on data stored in file sources by these blocks. This paper thus describes the ease of signal processing that can be attained by developing blocks in demand by changing the C++ and PYTHON codes of the HOWTO package. Being an open source it is available to all, is highly cost effective and is a field with great potential.

Real time implementation of FMCW radar for target detection using GNU radio and USRP

Nowadays, FMCW (Frequency Modulated Continuous Wave) radar is widely adapted due to the use of solid state microwave amplifier to generate signal source. The FMCW radar can be implemented and analyzed at low cost and less complexity by using Software Defined Radio (SDR). In this paper, SDR based FMCW radar for target detection and air traffic control radar application is implemented in real time. The FMCW radar model is implemented using open source software and hardware. GNU Radio is utilized for software part of the radar and USRP (Universal Software Radio Peripheral) N210 for hardware part. Log-periodic antenna operating at 1GHZ frequency is used for transmission and reception of radar signals. From the beat signal obtained at receiver end and range resolution of signal, target is detected. Further low pass filtering followed by Fast Fourier Transform (FFT) is performed to reduce computational complexity.

Radiation pattern measurement of log-periodic antenna on GNU Radio platform

Current laboratory setup for performing radiation pattern measurement of any antenna is composed of signal generators and a spectrum analyzer. The cost of these equipment increases substantially with the demand of precision in the output. In this paper, the radiation pattern measurement of a log-periodic antenna is done on a new platform, consists of GNU Radio Companion (GRC) and Universal Software Radio Peripheral (USRP). This forms a simple way of performing the radiation pattern measurement at low cost, compared to the conventional methods.

Real-time communication system design using RTL-SDR and Raspberry Pi

RTL-2832U USB receiver - Raspberry Pi setup receives and decodes the FM signals and sends to another computer across the Local Area Network. It can be realized by means of SDR-Sharp software in remote PC; hence it can be used for communication. Raspberry Pi is a low cost, credit-card sized computer. Whereas RTL-2832U USB receiver has a mode where it dumps raw IQ samples over USB to the computer. The GNU Radio experiments supports this relatively cheap USB receiver as a software defined radio. Using GNU Radio Companion, all real-time communication experiments can be reproduced.

MultiUser Spectrum Sensing based on Multitaper Method for Cognitive Environments

This paper gives a brief but comprehensive review of the Multitaper spectrum estimation method that uses the data tapers or windows in digital signal processing. Instead of using a single kind of window functions, here a cluster of window functions are mentioned, which is known as Slepian tapers. This taper family minimize leakage also, and computing them requires solving eigenvalue problems that are large for long time series. However, the eigenvalue problems have a special structure that makes a fast algorithm possible.Secondly, the enabling of the algorithmic method with Cognitive Radio (CR) Technology, which is an advanced version of Software Defined Radio (SDR) Technology is discussed. SDR Technology is supposed to become a prevailing technology in the field of wireless communication. The Software Radio is an interesting area, in which the GNU Radio explores and then the Universal Software Radio Peripheral (USRP) formulates it. Here the paper also proposes the idea of constructing a block in GNU Radio Companion using the same algorithmic method in GNU Radio. Keywords— Slepian tapers, Software Defined Radio, Cognitive Radio Networks, GNU Radio, USRP.

Accelerated FFT computation for GNU radio using GPU of raspberry Pi

This paper presents the effective exploitation of Graphical Processing Unit (GPU) in Raspberry Pi for fast Fourier transform (FFT) computation. Very fast computation of FFT is found useful in computer vision based navigation system, Global Positioning System (GPS), HAM radio and on Raspberry Pi. A comparison is performed over the speed of FFT computation on BCM2835 GPU with that of 700 MHz ARM processor available in Raspberry Pi and also with intel-COREi5 processors. The FFT is computed for any one dimensional input signal and its analysis is done on different processors with varying signal lengths. The GNU radio is installed on Raspberry Pi, and the FFT computation done on GNU radio is accelerated using GPU of Raspberry Pi. Even though the Raspberry Pi GPU is primarily built for video enhancement, the parallel computational ability of GPU is utilized in this paper for accelerated FFT computation.

Study of polyphase structure made easy using GNU Radio

Our current education system lacks in providing visualization of concepts, without which the learning process is incomplete. Particularly, in case of complex signal processing algorithms, visualizing is very difficult or almost impossible. The aim of this paper is to understand and provide visualization of the basic concepts of multirate signal processing using low cost computing platform, GNU Radio. Multirate signal processing has a significant influence at the physical or hardware layer of modern communication systems. In real, multirate signal processing is found at the core of communication systems that couple the Software Defined Radio (SDR) and Software Communications Architecture (SCA) to reconfigure system resources for operation over a wide range of modulation formats and waveforms. In multirate systems, polyphase structure plays an important role in reducing the computation rate by noble identities. The parallel processing makes it very efficient in implementation architecture. GNU Radio companion is an open source graphical simulation tool which we utilized for better understanding of complex signal processing concepts. In our paper we have implemented simple multirate signal processing building blocks.

Measurement of radiation pattern of Quadrifilar Helix Antenna (QHA) using GNU Radio

Communication experiments in conventional lab set-up require more hardware compared to softwares which increases the hardware complexity. This problem can be solved by using Universal Software Radio Peripheral (USRP-2) and open source software GNU Radio. This paper proposes a novel method to investigate radiation pattern measurements such as Half Power Beam Width (HPBW) and Front-to-back ratio of Quadrifilar Helix Antenna (QHA) using USRP-2 and GNU Radio. The Quadrifilar Helix Antenna is a simple and inexpensive equipment used for non-geosynchronous satellite research. This antenna is unique in its simplicity of design and powerful performance compared with standard directional receivers.