Resource Allocation in OFDM-based Cognitive Radio Systems

Elektrotechnik Diplomarbeiten (April 2008 - Oktober 2008) ofdm


Milan Zivkovic,


Radio spectrum is one of the most valuable resources for wireless communication. According to actual measurements, the most of the licensed spectrum is severely underutilized in both the time and spatial domain. Spectrum efficiency can be significantly increased by giving access of the frequency bands not used by primary (licensed) users to a group of secondary (unlicensed) users. Cognitive radio (CR) is the novel approach enabling flexible, efficient and reliable spectrum use by adapting the radios operating characteristics to the dynamically changing environments. By observing the spectrum of interest CR is able to cleverly detect the unused spectrum and determine transmission characteristics (power, bandwidth, symbol rate) of secondary users. This Talk will give an introduction to Cognitive Radios as a whole, but will focus on Spectrum Management, the ability to utilize unused parts of the spectrum in an optimal way, given all relevant transmission parameters obtained by other CR subsystems. Challenges as "out-of-band" interference introduced by secondary users and transmission power limits are addressed and used as additional constraints to enhance current optimization algorithms. Besides the necessary mathematical model, a simulation environment as well as first results will be presented.