Power control and multi-bands assignment for Cognitive Radio in LTE scenario

In this paper, we study the problem of multi-bands assignment and power control of a CR system which includes K of Cognitive Radio transceiver (CR Tx-Rx) using Orthogonal Frequency Division Multiplexing (OFDM) technique. They coexist side by side with L bands of a primary user system (PU). Each CR Tx-Rx is assigned to a portion of temporal free spectrum. In order to exploit this temporal free spectrum effectively, a multi-band allocation is permitted, where many pairs of CR Tx-Rx have their own radio frequency (RF) front-end. Firstly, we propose an efficient low complexity bands assignment to each pair of CR. The Idea is to allocate the total interference from PU to every CR Rx equally. After the frequency bands for each pair of CR Tx-Rx have been operated, we solve the total sum-rate maximization problem of CR downlink capacity with interference and power constraints concerning CR intra-network interference. However, the problem of multi-band allocation technique is the vulnerability to synchronization errors which leads to a loss of orthogonality. In this study, we take not only the conventional mutual user interference (MUI) between PU and CR but also inter user interference (IUI) between CR users into account. The results show that the CR transmission capacity depends critically on bands assignment and power allocation approaches. These effects are investigated in LTE-A scenario.