| The concept of cognitive radio with many promising features like spectrum sensing, dynamic spectrum access has the potential to greatly improve the spectral efficiency. In this thesis, we study the problem of spectrum-hole sharing, i.e., vacant channel and power allocation to multiple cognitive radio (CR) users who coexist in a network. Based on the game theory, we formulate two different objective functions considering user requirements. In the first scenario, the sum data rate of a network is maximized. A non-cooperative game with pricing is formulated for interference transmission in which each cognitive radio user is equipped with multiple antennas at both transmitter and receiver. Each user incorporates a vector of adaptive pricing factors on each channel based on transmission power of other users. The formula of optimal pricing is derived and a distributed iterative algorithm is designed through small amount of information exchange between users. The simulation results demonstrate the performance gain of the proposed algorithm over the classical iterative water-filling algorithm without pricing and intuitive pricing formulations.In the second scenario, a new metric indicating user satisfaction in both data rate and power consumption is formulated. Initially, joint channel and power allocation algorithms are designed for both orthogonal transmission and interference transmission for cognitive radio users equipped with single antennas. Then, these algorithms are extended for multiple antennas configuration. Numerical results demonstrate the efficiency of the proposed algorithms. The performance comparison is conducted for orthogonal and interference transmissions under different interference scenarios. The performance gains by allowing interference transmission and by using multiple antennas at transceivers are demonstrated. |
