On May 17th, Nutaq attended the 2013 New England Workshop for Software Defined Radio, also known as SDR Boston, where we connected with our community of developers and researchers in SDR. One presentation drew our attention, from Prof. Kapil Dandekar of Drexel University.
Drexel University’s OFDM Testbed
Drexel’s Wireless Systems Laboratory spent several years working on their Software Defined Communications (SDC) Testbed. The goal of this project is to provide the community with a framework for OFDM waveform development from which one can easily generate signals, establish radio links, modify core OFDM parameters at run time, and so on. Drexel built their OFDM system from the existing grounds of a Xilinx® reference design, which implements an OFDM chain in FPGA. That OFDM chain may also be simulated with bit-true, cycle-true precision in Simulink® from MathWorks®, thanks to the System Generator for DSP™ plug-in from Xilinx. Prof. Dandekar’s group added missing components such as forward error correction and synchronization, and made it as flexible as possible in changing key OFDM parameters. In terms of hardware, Drexel used Xilinx ML605 FPGA board, and integrated Nutaq’s highly tunable Radio420m front end.
The great flexibility of the SDC means it can be used to implement different flavors of OFDM waveforms, from the standard ones like Wi-Fi, Wimax, and LTE, to non-standard ones like the adaptation Drexel did for ultrasound communications through thick metallic walls of Navy’s ships. The Radio420m matches well with this flexibility, by enabling wireless operation anywhere between 300 MHz and 3.8 GHz, with 16 choices of instantaneous bandwidth (see image at right), from 1.5 MHz up to 28 MHz. For applications that have specific analog requirements, Drexel has integrated alternate, inter-changeable front-end modules, such as an ultrasound transceiver, or ultra-wideband A/D and D/A converter.
Laval’s MIMO-OFDM Reference Design
Presenting right before Prof. Dandekar was Jean-Benoit Larouche, M. Sc. candidate at Laval University. Jean-Benoit shared with the community his progress in building an OFDM reference design, which has a lot a commonality with Drexel’s initiative. Again leveraging the model-based design flow enabled by Simulink and System Generator, Jean-Benoit performed a live demonstration of an HD video source being streamed through his 2×2 MIMO scheme and played on the receiver end. The waveform was developed and demonstrated using Nutaq’s PicoSDR, also featuring Virtex®-6 FPGA and Radio420m front end.
Given the outcome of both initiatives, there is no doubt that developers now have valuable tools at their disposal to experiment with OFDM waveforms, and build upon these testbeds and reference designs to create tomorrow’s wireless systems and applications.