Programmable Wireless Networking Testbed for Cognitive Radio Experimentation
While the demand for additional bandwidth from both existing and new wireless services is steadily increasing, the amount of available/unlicensed spectrum is very limited. At the same time, several measurement studies have shown a relatively low level of spectral occupancy in most licensed bands across frequency and time. To solve the apparent spectrum scarcity problem, the dynamic spectrum access (DSA) concept can be employed, where unlicensed users can "borrow" licensed bands while simultaneously respecting the rights of the incumbent license holders. To enable DSA networks, software-defined radios (SDRs) and cognitive radios can be employed. These radios can rapidly adapt and configure themselves to the prevailing operating conditions by implementing most of their radio functions in digital logic and software. The goal of this project is to implement a programmable wireless networking testbed using software-defined radio (SDR) units for the purpose of conducting research into cognitive radio technology.
Quantification of Spectrum Availability for Wireless Network Access
To resolve the apparent scarcity of available prime radio spectrum (300 MH -- 3 GHz), the dynamic spectrum access paradigm was proposed to improve spectrum utilization. By enabling temporary unlicensed wireless access to unoccupied licensed spectrum, called spectrum holes, a larger number of wireless transmissions can be supported by the same spectrum while simultaneously respecting the rights of the incumbent license holders. However, this paradigm heavily depends on the location and size of these spectrum holes, which can vary randomly with respect to time, frequency, and geography. The objective of this project is: (i) to accurately characterize the availability of prime spectrum in mid-size US cities, i.e. average and most common case, for secondary access via theoretical and experimental techniques, (ii) to quantitatively determine the long-term behavior and trends of spectrum occupancy and spectrum hole availability, and (iii) to understand and obtain insight into the electrospace characteristics (time, frequency, spatial) over a large urban area. This project is supported by the National Science Foundation (NSF) via grant number 0754315.
Practical Transceiver Optimization Techniques Employing Cognitive Radios
With most of the SDR radio functions implemented in digital logic and software, the transceiver parameters can be tailored to the operating environment in order to enhance the spectral efficiency of the system. Although there has been extensive research in developing algorithms that can automatically adjust these parameters (modulation, transmit power levels, coding rate), these algorithms are either computational complex, require a substantial amount of transmission overhead, or select parameters that are far from the optimal solution. Using versatile and powerful SDR technology, the focus of this project is to develop practical adaptive allocation techniques for enhancing the spectral efficiency of the system.
Distributed Cognitive Radio Networking
To be updated
Interference Minimization Techniques for Agile Wireless Transmission
To be updated