Full Duplex Prototype of OFDM on GNURadio and USRPs

International audienceFull-duplex is a technology in telecommunication domain that can perform transmitting and receiving at the same time and in the same frequency band. The major obstacle of full-duplex is the self-interference (SI). Some previous works have focused on the SI cancellation in radio frequency (RF), and generally on a narrowband signal model. We have implemented a full-duplex prototype with orthogonal frequency-division multiplexing (OFDM) technology on GNURadio and Universal Software Radio Peripherals (USRP). We focus on the baseband, namely the digital part of the SI cancellation. Our testbed can achieve a digital cancellation of 27dB. After the cancellation, the signal of interest can achieve a bit error rate (BER) in the scale of 105 at 4 meters, which is very close to the performance of half-duplex. This is, to our knowledge, the first full duplex implementation for OFDM technology

Software Defined Platforms for Visible Light Communication: State of Art and New Possibilities

International audienceThe requirement of connected devices exponentially increases day by day as well as the bandwidth needed for novel applications. As a consequence of this, radio frequency spectrum becomes more and more crowded, thus leading to serious limitations in the diffusion of novel technologies when considering challenging environments such as hospitals and airplanes, where EM interferences are particularly unwanted. The integration of Visible Light Communication (VLC) in the existing infrastructures could provide a valid tool to address these issues. In this context, Software Defined concepts could significantly simplify the integration process, leading to the development of low cost and flexible architectures. To this end, Universal Software Radio Peripheral (USRP), designed and commercialized by Ettus Company and National Instruments, is emerging as a comparatively low cost hardware platform for software defined architectures, allowing rapid prototyping and test bed validations. The aim of the present work is to exploit the current literature in the framework of Software Defined Systems based on USRP platform for VLC purposes, while briefly highlighting some useful potentialities for the development of solid and flexible architectures

Energy-detection based spectrum sensing for cognitive radio on a real-time SDR platform

There has been an increase in wireless applications due to the technology boom; consequently raising the level of radio spectrum demand. However, spectrum is a limited resource and cannot be infinitely subdivided to accommodate every application. At the same time, emerging wireless applications require a lot of bandwidth for operation, and have seen exponential growth in their bandwidth usage in recent years. The current spectrum allocation technique, proposed by the Federal Communications Commission (FCC) is a fixed allocation technique. This is inefficient as the spectrum is vacant during times when the primary user is not using the spectrum. This strain on the current available bandwidth has revealed signs of an upcoming spectrum crunch; hence the need to find a solution that satisfies the increasing spectrum demand, without compromising the performance of the applications. This work leverages on cognitive radio technology as a potential solution to the spectrum usage challenge. Cognitive radios have the ability to sense the spectrum and determine the presence or absence of the primary user in a particular subcarrier band. When the spectrum is vacant, a cognitive radio (secondary user) can opportunistically occupy the radio spectrum, optimizing the radio frequency band. The effectiveness of the cognitive radio is determined by the performance of the sensing techniques. Known spectrum-sensing techniques are reviewed, which include energy detection, entropy detection, matched-filter detection, and cyclostationary detection. In this dissertation, the energy sensing technique is examined. A real-time energy detector is developed on the Software-Defined Radio (SDR) testbed that is built with Universal Software Radio Peripheral (USRP) devices, and on the GNU Radio software platform. The noise floor of the system is first analysed to determine the detection threshold, which is obtained using the empirical cumulative distribution method. Simulations are carried out using MATrix LABoratory (MATLAB) to set a benchmark. In both simulations and the SDR development platform, an Orthogonal Frequency Division Multiplexing (OFDM) signal with Quadrature Phase Shift Keying (QPSK) modulation is generated and used as the test signal