Software Defined Radio Capabilities

DWSL has developed a testbed that challenges the radio frequency-centric view of software defined radio. In particular, a testbed and software framework has been developed for rapidly prototyping Multiple-Input Multiple-Output (MIMO) "Software Defined Communications" systems that enables wireless networking research over radio, ultrasonic, and diffuse optical propagation modalities.

Typically, software defined radio dynamically switches between multiple communications and networking protocols in response to the network state. However, in our testbed, reconfigurability extends beyond these protocols to include the transceiver hardware. This testbed has enabled a large number of research and educational projects in areas including MIMO ad hoc radio networking, electrically reconfigurable radio frequency antennas, conductive organic polymer antennas, MIMO diffuse optical local area networking, and "modality diversity" systems that make hybrid, coordinated use of two or more propagation media for wireless networking.

The above shows a basic block diagram of a MIMO software defined communication system. Three such nodes were implemented in 2004-2005, with an additional two nodes in 2005-2006. Each node has 2 RF antenna array elements and transceivers, and the system can be expanded without re-design to 4 array elements and transceivers. Each node can also have 4 ultrasonic or 4 diffuse free space optical transceivers.

In each node, there are three main components, an analog front end / transceiver that can include conformal or standalone antenna arrays, a frequency agile RF transceiver donated from Texas Instruments (RCS 110), a software defined baseband data acquisition system (PXI 5122 and 5421), and general purpose PCs for the MAC and higher layers. The RF transceiver cards are capable of transmitting at all channels in both the Industrial, Science, and Medicine (ISM) band between 2.4 and 2.5 GHz as well as in the Unlicensed National Information Infrastructure (UNII) band between 4.9 and 5.9 GHz. The cards are designed to operate independently of existing wireless standards, and thus provide us with maximum flexibility. Custom-built transceivers also exist for diffuse free space optical and ultrasonic communication modalities.

The analog front end and the baseband data acquisition system are all contained in a PXI chassis from National Instruments. Analog signals are converted to and from digital using PXI data acquisition cards from National Instruments and then passed to a dedicated chassis processor (PXI-8186) which implements the physical layer in LabVIEW. This processor then communicates over gigabit ethernet with a general purpose host which runs the MAC, higher layer network protocols, and any application software.

WARP Board

DWSL also owns 5 MIMO nodes of the Wireless Open-Access Resarch Platform (WARP) developed by Rice University. Baseband processing in WARP is achieved using a Xilinx Virtex-II PRO FPGA capable of processing data at 100s of Megabits per second with onboard embedded PowerPC processor cores. Each WARP node daughtercard has ISM and UNII band radio transmitters with dual 65 MS/sec 14-bit ADCs and dual 125 MS/sec 16-bit DACs. This platform is flexible, allowing for software reconfigurability of all layers of the protocol stack. WARP is also modular so that new daughtercard modules can be implemented to prototype communication networks with other frequency bands, radio standards, or communication modalities (e.g., optical, ultrasound). Programming WARP can be accomplished using a variety of interfaces ranging from low level VHDL code, Xilinx System Generator, and Matlab for physical layer algorithm development and Platform Studio in C/C++ for implementing higher layers of the protocol stack. Furthermore, WARP has a large community of users to provide technical support and a vehicle for dissemination of research results and newly developed communication and networking techniques.

Antenna Fabrication Facilities

DWSL owns a printed circuit board milling machine from T-Tech. The laboratory also contains all the necessary accessories for fabricating multi-layer (up to 6 layers) circuit boards, vias for inter-layer connections, and solder masks. Import of various CAD formats is possible with this fabrication tool. Milling of antennas and circuit boards has been accomplished on a variety of substrates including FR-4 and Rogers Duroid.

For printing conformal antennas out of unconventional materials on non-traditional substrates, the Fujifilm-Dimatix DMP-2831 materials printer makes use of a unique fluid deposition system including a MEM print-head that uses an electrically controlled membrane to eject fluids. The printer can deposit controllable drop sizes down to the pico-Liter scale, and is capable of printing on virtually any substrate. The print cartridges are filled easily via syringe, and the correct printing parameters can be observed through the use of a drop-watching camera which puts the 16 nozzles of the print head under magnification. To make pattern design simple, the optional Gerber file importing software was purchased allowing virtually any design to be created in a number of CAD environments and imported directly into the printer. Once the printing if finished, an included fiducial camera puts the substrate under magnification so that it can be viewed on the single-drop scale to ensure the proper overlapping and layout.

Sensor Network Capabilities

Computational Electromagnetic Simulation Tools

DWSL has CAD software to model electromagnetic antennas and propagation. It owns a license of the ray tracing software system, Fasant, from Dr. M.F. Catedra, Universidad de Alcala in Madrid, Spain. DWSL has further modified this system to simulate smart antenna and MIMO system performance in urban environments of mobile communications systems. DWSL owns a network of PCs and has computer aided models of several downtown environments (Philadelphia, PA - Austin, TX - Ft. Benning, GA) for conducting computational electromagnetic simulations.

DWSL has access to the FEKO and NEC system for moment method characterizations of near/far field propagation in standalone and conformal antenna arrays. Design and analysis capabilities include HFSS, ADS, and other specialized computer programs.

DWSL has developed a testbed that challenges the radio frequency-centric view of software defined radio. In particular, a testbed and software framework has been developed for rapidly prototyping Multiple-Input Multiple-Output (MIMO) "Software Defined Communications" systems that enables wireless networking research over radio, ultrasonic, and diffuse optical propagation modalities.