Given the difficulties associated with field testing of wireless communication systems in diverse environments, it would be beneficial to have a testbed that can expose real radio hardware to realistic indoor and outdoor wireless channels in a controllable and repeatable manner. To address these challenges, we are building the Drexel Grid SDR Testbed. This testbed is a unified experimental framework to rapidly prototype and evaluate a diverse range of wireless systems using: i.) field measurements to evaluate real time transceiver and channel-specific effects and ii.) network emulation to evaluate systems at a large scale with controllable and repeatable propagation channels. The hardware of the Drexel Grid SDR testbed consists of: i.) the Echo Ridge DYSE 24 port network channel emulator for multi-link emulation as well as hybrid measurement and simulation, ii.) a centralized server for experiment management hosting virtual machines for each of the nodes in the grid, iii.) 20 N210 and 4 X310 NI software defined radios (SDRs) deployed in a ceiling based network for over the air (OTA) testing (using omni-directional or reconfigurable directional antennas) or adaptive network and channel emulation, and iv.) a wired network for routing RF, timing, and control signals to nodes for automated experimentation with the testbed.
Complementing this hardware infrastructure is a software infrastructure composed of i.) an API with a custom built experimenter interface for reserving nodes and controlling the wireless channel emulator for both over the air and emulated experiments, and ii.) an LXC container based system for deploying SDR software supporting either GNU Radio or a custom full radio protocol stack that we have developed for cross layer prototyping and experimentation. Some key features of the testbed include:
Flexible, real-time prototyping - Many SDR platforms in the industrial and academic research community are focused on relatively small variations of existing standards. The Drexel Grid SDR Testbed builds upon our work in developing a real-time, cross-layer, full radio stack software implementation, along with our experience in developing new antenna technologies for wireless communication systems. This flexibility, and potential for cross-layer integration, will be essential to consider a diverse set of applications including cybersecurity, cyberphysical systems, smart cities, and the Internet of Things without the constraints imposed by commercial standards.
Repeatable and customizable channels - Many existing wireless testbeds do not have real-time customizable and repeatable physical layer propagation channels. We are using the EchoRidge DYSE channel emulator to create customizable and repeatable channels using industry-standard and custom channel models while also enabling OTA testing in an indoor office environment with novel antenna technologies that provide broadband and directional radiation pattern capabilities. Furthermore, we have developed a software layer to allow site-specific electromagnetic ray tracing to provide the far-field channels encountered by the radio and have demonstrated how this can be used for site specific emulation for applications like UAV air-to-air and air-to-ground communication channels.
Scalability - While testbed-based measurement campaigns often provide greater realism, they usually also suffer from a lack of scalability (i.e., less than a dozen nodes in any single experiment) due to the difficulty and expense in developing and maintaining custom hardware. The Drexel Grid SDR Testbed will addresses this limitation by providing a software API and hardware network emulation that will allow physical nodes and virtual nodes to co-exist with one another from the perspective of the overlying network as well as the underlying physical layer propagation channels.
The Drexel Grid SDR testbed is being used for a wide variety of research and educational projects at Drexel University, and uses a container structure similar to that used by the DARPA Spectrum Challenge Colosseum. It is our hope to make our testbed available to external users to allow them to run experiments such as i.) deploying radio containers with the ability to adjust the wireless channel between nodes and ii.) evaluation of custom antenna technologies with our customizable full stack software defined radio network. If you are interested in discussing potential research collaboration using the testbed in these or other areas, please contact us.
For internal Drexel users, you may access the testbed and training materials here. Note that you must be connected to the campus VPN to access this site.