In Search of Wireless Spectrum: WPI Research Team Conducts Measurement Campaign in Four U.S. Cities to Assess Nation's Spectral Resources

Ridged Horn Antenna used for gathering information on spectrum usage.

By Alexander M. Wyglinski, Ph.D.

A WPI ECE research team of both undergraduate and graduate students, supervised by Professor Alexander M. Wyglinski, are actively quantifying the Nation's electromagnetic spectrum assets in order to determine whether there is enough of this finite natural resource for supporting current and future wireless services, some of which could potentially rely heavily on large amounts of spectrum.  Modern society depends on ubiquitous wireless access in order to function.  However, with the increasing demand for untethered network connectivity reaching unprecedented levels, especially for high data rate applications and services, the problem of wireless spectrum scarcity is beginning to emerge as a serious detriment to the growth of the wireless sector.  Federal regulators worldwide have already identified this problem and have proposed several solutions to resolve this scarcity issue via changing conventional wireless spectrum regulations to allow for secondary access of licensed spectrum by unlicensed devices.

The proposed modification of wireless spectrum regulations assumes that the majority of wireless spectrum is extensively underutilized.  Although this assumption is based on several independently conducted measurement campaigns in the U.S. and abroad, there still exists a need to obtain a deeper understanding of this natural resource.  By gaining this insight into wireless spectrum, appropriate technical and legislative actions can be taken in order to support continued growth in the wireless sector. 

Most spectrum measurement studies focus primarily on only a few large, high population density urban centers rather than the typical mid-size US city.  Moreover, extensive research is needed in order to relate RF spectrum across an urban geographical region.  Finally, there is currently no existing long-term trend analysis of RF spectrum availability in the US.  Such an analysis can assist US spectrum policy in determining new approaches to allocating spectrum in order to further support our national wireless infrastructure.

The NSF project: "NeTS-WN: Quantification of Spectrum Availability for Wireless Network Access" led by Dr. Alexander Wyglinski (Principal Investigator), an Assistant Professor of Electrical and Computer Engineering at Worcester Polytechnic Institute (WPI), is currently seeking solutions to these above mentioned issues with his research team consisting of Ph.D. student Srikanth Pagadarai and two undergraduate students, Alexander Camilo and Robyn Colopy, both funded through the NSF Research Experiences for Undergraduates program.   

To quantitatively assess the occupancy of the wireless spectrum, Dr. Wyglinski and his research team first constructed at WPI a custom-built mobile wireless spectrum measurement test-bed that is capable of detecting occupied wireless spectrum from 80 MHz to 3000 MHz with signal strengths as weak as -125 dBm.  The test-bed can be easily transported to a measurement site and operated with minimal setup time. 

Next, to automate the wireless spectrum measurement process, a universal open-source software interface to the spectrum analyzer equipment was developed in order to facilitate the rapid acquistion of wireless spectrum occupancy information.

Finally, in June of 2008, Dr. Wyglinski and his research team conducted wireless spectrum measurements for several frequency bands in the 100 MHz to 3 GHz range at five downtown locations in each of the following four cities: Worcester, MA; Rochester, NY; Pittsburgh, PA; Buffalo, NY.  Phase 2 of the spectrum measurement campaign will be conducted in four more U.S. cities in the summer of 2009.

The 6 GB of wireless spectrum occupancy data collected from these measurements is an extremely valuable source of information to the research community.  Efforts are currently underway to process this data to extract spectrum occupancy statistics (see Figure 1) and to make this spectrum database available online to the entire community. 

Figure 1

Knowing how much wireless spectrum has been officially allocated to various organizations within the U.S. is an essential first step in providing a benchmark for any spectrum measurement campaign and availability assessment.  The survey of official allocations conducted by Professor Wyglinski and his team, in conjunction with actual wireless spectrum measurements, has made it possible to provide a solid quantitative value representing how efficiently our national wireless spectrum resource is being utilized.

Furthermore, the custom-built mobile wireless spectrum measurement test-bed developed at WPI can be used to conduct further research into wireless spectrum usage as well as other activities into wireless systems and networking innovations.  The measurement test-bed can also be employed in a classroom or teaching laboratory setting for the purpose of undergraduate and graduate education.

By understanding how wireless spectrum is currently being utilized over both the short and long terms, the research community and the wireless sector as a whole can devise new approaches and techniques that would enable greater wireless ubiquity and access in the US and worldwide.

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The WPI wireless spectrum measurement team (L to R): Pagadarai, Colopy, Camilo, and Wyglinski.

Camilo, Pagadarai, and Colopy prepare the equipment for a wireless spectrum measurement sweep in downtown Rochester, NY.

Colopy and Pagadarai perform an initial check of wireless spectrum measurements obtained in downtown Buffalo, NY.

A ridged-horn antenna is trained on downtown Buffalo, NY on 22 June 2008.

April 3, 2009