Lab Research

Research Areas

Figure 1: Bellyband smart fabric antenna

Figure 1: Bellyband smart fabric antenna

Recent advancements in specialized materials and fabrication technologies offer exciting opportunities to realize seamless garments as sensors and actuators for biomedical applications. Knitting fabrication, known as the inter-meshing of yarns into loops (resulting in fabrics), is an ancient form of textile production widely used in the fashion industry. Knitting technology has gained a lot of attention in the field of wearable electronics and has potential to become a widespread method of construction for smart textiles in the future. In particular, Shima Seiki knitting technology enables customization and innovation in the design and fabrication of wearable smart textiles for biomedical sensing and actuation applications. While most electronic textiles in existence today make use of circuits adhesively integrated onto a host garment, our knitting technology enables the creation of garments with seamlessly integrated sensors and actuators. This type of fabric production offers huge savings in terms of manufacturing costs and significantly reduces material waste, enabling new design approaches and innovation in garment and product development.

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Figure 1: A 2X4 antenna array. Figure measurements are in mm

Figure 1: A 2X4 antenna array. Figure measurements are in mm

Forecasts of increasing demand on cellular communications, as a result of the growing number of devices that run data-consuming applications, cannot be fulfilled through research that focuses only on the spectral efficiency of the already congested conventional cellular spectrum at frequencies below 6 GHz. DWSL believes that solving the spectrum scarcity problem can be done by paving the way for the utilization of under-licensed spectrum at millimeter wave (mmW) frequencies for cellular communications.

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The accessibility of small Unmanned Aerial Vehicles (UAV) has increased dramatically over the past few years. UAVs are now much more affordable to build and manufacture. The decrease in cost is sparking interest in utilizing UAV in commercial applications in various fields including security, disaster relief, infrastructure inspection, and telecommunications. DWSL is investigating wireless applications for low-altitude multicopter UAVs equipped with software-defined radio (SDR) platform. The lab is currently building a low-cost UAV-SDR hexacopter testbed using popular off-the-shelf multicopter components and a lightweight SDR system.

Figure 1: UAV Mounted with Monopole Antenna

Figure 1: UAV Mounted with Monopole Antenna

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Electrically reconfigurable antennas are capable of dynamically reshaping themselves and their radiation characteristics in response to the needs of the overlying communication link and network. Most past work on reconfigurable antennas focused on antenna geometries that provide agility in frequency. DWSL has pioneered the application of pattern reconfigurable antennas to multiple input multiple output (MIMO) communication systems and has, more importantly, demonstrated how reconfigurable antennas can be treated as a valuable additional degree of freedom for software defined radio, cognitive radio, and systems "beyond cognitive radio"1. Sample DWSL reconfigurable antennas are shown in Figure 1.

Figure 1: DWSL Reconfigurable Antenna Architectures

Figure 1: DWSL Reconfigurable Antenna Architectures

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Two prominent examples of SDR in the academic community are the GNU USRP/USRP2 SDR and the Wireless Open-Access Research Platform (WARP) testbed. Multiple nodes of both GNU radio and WARP are available in our laboratory for evaluation and development of software defined radio networks, as is the HYDRA testbed developed in collaboration with the University of Texas at Austin. However, the majority of SDR platforms that are widely available to the academic and industrial research community have several notable limitations, including:

  • Sampling rates and processing capabilities limited so that systems are predominantly limited to IEEE802.11 data rate
  • Lack of available FPGA fabric and programming flexibility to allow implementation of newest algorithms proposed by the communications and signal processing community
  • Exclusive focus on radio-frequency based communications

To address these limitations, using funding from NSF (CNS #0923003 and CNS #0854946), DWSL is developing a "Software Defined Communication" (SDC) Testbed1 for release to the wireless academic and industrial research community. The SDC Testbed seeks to provide a research and development platform capable of designing and prototyping next generation wireless communication standards which make use of radio, optical, and ultrasonic communication modalities. The vision for this platform builds on the current principles of SDR. Specifically, it extends this concept through utilization of propagation media beyond the RF spectrum while meeting the high bandwidth demands of emerging communications standards. The project will provide an open source tool for both the commercial and academic wireless research communities. Furthermore, it is designed to provide a cohesive and affordable hardware/software infrastructure for fast and flexible algorithm development across multiple layers of the communication stack.

Figure 1: Conceptual Diagram of the SDC Testbed

Figure 1: Conceptual Diagram of the SDC Testbed

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The increasing demand for high-speed, high-quality mobile communication has fueled interest in spectrum-efficient multiple-input multiple-output (MIMO) wireless communication links. Systems with MIMO communication links use multiple antenna arrays, one at the transmitter and one at the receiver, to take full advantage of the spatial dimension of the propagation channel. When properly designed, multi-array communication links can provide multi-fold increases in link throughput in addition to dramatic reductions in channel variation. This can be used to provide higher data rates to single users, lower delay links, or to allow multiple users to coexist in the spatial channel. Due to these advantages, MIMO capability is being considered for indoor local area networks, cellular multimedia data networks, and broadband fixed wireless access.

Orthogonal frequency-division multiplexing (OFDM) is a modulation technique designed for frequency selective communication mediums that does not increase the complexity of equalization at the receiver and allows for high throughputs. OFDM divides the wideband, frequency selective transmission channel into several orthogonal, flat fading narrowband channels. Thus, each sub-frequency can be treated as an independent channel, allowing for various forms of adaptive modulation techniques to be performed on each subcarrier.

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Diffuse free space optical local area networks (LANs) have several potential advantages over conventional radio frequency networks. Beyond the potential for increased data rates, the optical spectrum offers a large unregulated bandwidth capacity potential. Diffuse optical networks are not limited by electromagnetic interference due to the physical constraints of the infrared (IR) medium. Therefore, they are easier to deploy (since they do not require frequency planning) and are more secure than their RF counterparts (since IR radiation is confined within the physical boundaries of the coverage area. However, even with these potential advantages over RF systems, current academic and commercial diffuse optical LAN networks still provide lower data rates than RF LAN, due to the optical power decreasing greatly as the signal diffuses from a medium.

Figure 1: Alamouti Free Space Optical Code adapted for use in MIMO Free Space Optical LAN

Figure 1: Alamouti Free Space Optical Code adapted for use in MIMO Free Space Optical LAN

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Various industrial control networks require data communication in environments where metallic structures restrict network connectivity. For instance, Navy ships making use of wireless control networks below decks require a means to pass signals from one compartment to anther. In some applications, the barrier can be penetrated with wiring, while applications involving structures such as pressurized pipelines, watertight bulkheads, armor plating, etc., make it undesirable to physically penetrate the structure. Ultrasonic wireless links have been proposed to overcome this problem by using through-metal data communication. However, the ultrasonic link experiences sound wave propagation latency. Further, its reverberant nature limits the communication bandwidth and therefore creates a bottleneck to network traffic. Narrowband approaches suffer from high ISI caused by signal echoing within the bulkhead. DWSL has developed a communications testbed that allows for prototyping and evaluating ultrasonic communications.

Figure 1: Ultrasonic Physical Layer Testbed

Figure 1: Ultrasonic Physical Layer Testbed

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Environmental pollutants are known to have detrimental health effects, especially for populations living in areas with heavy exposure. Air quality monitoring is one way to measure the amount of these substances to assess the amount and type of pollutants present in an environment. Air monitors designed and developed in DWSL have been used to monitor particulate matter (PM) concentrations in two areas: Port Richmond, Philadelphia, and North Penn High School in Lansdale, PA. These nodes were deployed for one week at each location to measure particulate matter concentrations.

The air monitors, often referred to as air sensor nodes, consist of:

  • Dylos DC1100 indoor air monitor
  • Wireless transmitter (to communicate with other nodes and the base station)
  • 1 or 2 batteries (depending on location of the node and ability to be connected to a power source)
  • CO sensor (in selected nodes)
  • Necessary circuitry to run Dylos, draw power from two batteries, and communicate wirelessly (fabricated by Drexel Engineering students and North Penn students)
Figure 1: Particulate Matter Sensor Node

Figure 1: Particulate Matter Sensor Node

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In this project, DWSL addresses the problem of near-field and far-field propagation by combining two different computational electromagnetic (CEM) techniques: Method of Moments (MoM) and Electromagnetic Ray Tracing (ERT).

Next-generation communications systems will make use of smart antenna technology to handle the increasing demand for wireless services. Smart antenna technology makes use of adaptive antenna arrays at the basestation to improve system capacity and quality. The channel encountered by this array of antennas is referred to as the vector channel. During transmission, the excitation currents fed to the array elements are adjusted in relative amplitude and phase so as to adjust the overall radiation pattern of the array. Using these relative amplitude and phase excitations, referred to as beamforming, regions of constructive interference can be steered to focus signal energy to locations of interest. In an analogous way, by analyzing the relative amplitude and phase of signals received by the array, the direction of arrivals of incident energy to the array can be determined. This process is referred to as direction of arrival (DOA) analysis.

When smart antenna arrays are used at both ends of the communication link, the result is a Multiple-Input, Multiple-Output (MIMO) system. MIMO systems use sophisticated space-time coding techniques to greatly improve the capacity of wireless links over conventional wireless systems. The system can thus take full advantage of the spatial dimension of the propagation channel. When properly designed, these MIMO or multi-array links can provide multi-fold increases in link throughput while also providing dramatic reductions in channel variation.

Figure 1: Illustration of a MIMO System

Figure 1: Illustration of a MIMO System

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Collaborators

  • Michele D'Amico (Politecnico di Milano)
  • Antonio Forenza (Rearden Communications)
  • Robert Heath (University of Texas - Austin)
  • Moshe Kam (New Jersey Institute of Tech.)
  • Hao Ling (University of Texas - Austin)
  • Scott Nettles (University of Texas - Austin)
  • Athina Petropulu (Rutgers University)
  • Daniele Piazza (Adant, Inc.)
  • Harri Saarnisaari (University of Oulu)
  • Akbar Sayeed (University of Wisconsin)
  • Saurabh Sinha (University of Cape Town)
  • Mikko Valkama (Tampere Univ. of Tech.)