Is RF spectrum space all used up the United States? FCC license allocation charts and high-priced auctions imply that this is the case. But, we know this is not true. Spectrum usage varies greatly with:
Radio technology has advanced greatly over the years. We started with analog (tube) radios, migrated to solid-state (transistors), and more-recently, digital radio platforms (DSP, specialized ASICs). Now, we are on the verge of a new revolution: software-defined radio.
Software-Defined Radios are radios in which the radio operations such as FFTs, filtering, and demodulation are implemented in software. A generic piece of hardware can be used to digitize a radio signal allowing processing to be done using the raw sample data. This allows tremendous flexibility in that radio behavior can be change as needed by changing some code. A software-defined television also potentially could be your FM radio, your cell phone, and your GPS receiver simply by changing the program it is running!
This technology also makes much easier the development of a new class of radios which may be able to help alleviate the RF spectrum scarcity problem. So-called cognitive radios listen as well as transmit, can step around or under existing signals, and can adapt cooperatively with new and existing systems.
This thesis is a study of radio frequency spectrum space in the range from 50 MHz to 860 MHz - a range that covers FM radio broadcasts, television, as well as some others. Using the gnu radio software-defined radio platform, I will develop algorithms to try to identify the type of transmission being carried on a particular frequency. Traditional spectrum usage studies have made quantitative measurements of spectrum energy. With the algorithms such as those from this thesis, cognitive radio systems can be made to adapt in a qualitative way to their surrounding RF environment. I hope to be able to say what sort of signal is at a particular frequency rather than just say that something is there.
A pdf copy of my thesis is available here:
Cooley, James E., "A Day in the Life of the RF Spectrum."
S.M. Thesis, Massachusetts Institute of Technology,
Cambridge. September, 2005. (pdf)
You can find some PowerPoint presentations I have given on this topic below:
At the Communications Futures meeting, January, 2005
At the Communications Futures meeting, 2/25/05
Questions, comments: j c o o l e y (at) m e d i a (dot) m i t (dot) e d u