Dynamic spectrum access using the interference temperature model

To combat spectral overcrowding, the FCC investigated new ways to manage RF resources. The idea was to let people use licensed frequencies, provided they can guarantee interference perceived by the primary license holders will be minimal. With advances in software and cognitive radio, practical ways of doing this are on the horizon. In 2003, the FCC released a memorandum seeking comment on the interference temperature model for controlling spectrum use. Analyzing the viability of this model and developing a medium access protocol around it are the main goals of this article. A model consisting of interference sources, primary licensed users, and secondary unlicensed users is modeled stochastically. If impact on licensed users is defined by a fractional decrease in coverage area, and this is held constant, the capacity achieved by secondary users is directly proportional to the number of unlicensed nodes, and is independent of the interference and primary users’ transmissions. Using the basic ideas developed in the system analysis, interference temperature multiple access, a physical and data-link layer implementing the interference temperature model, was formulated, analyzed, and simulated. A system implementing this model will measure the current interference temperature before each transmission. It can then determine what bandwidth and power it should use to achieve a desired capacity without violating an interference ceiling called the interference temperature limit. Ultimately, the resulting performance from the interference temperature model is low, compared to the amount of interference it can cause to primary users. Partly due to this research, in May 2007, the FCC rescinded its notice of proposed rule-making implementing the interference temperature model.