Subcarrier and power allocation in OFDM based cognitive radio networks A Survey

Abstract: This paper investigates the subcarrier and power allocation problem for an OFDM-based cognitive radio (CR) system. For CR systems it is important to keep the interference below the certain threshold to the primary user and the total power allocated to the CR user under a constraint . Since the joint subcarrier and power allocation problem is a non-convex integer problem and a closed form solution is difficult to find, a optimal and suboptimal algorithm that separates subcarrier and power allocation is investigated. The suboptimal subcarrier algorithm is proposed that allocates subcarriers to CR users that not only increase the transmission rate, but also reduces the interference introduced to the primary user (PU) band. Comparison results show that for CR systems the proposed algorithm is able to load power into the subcarriers while keeping the interference below a specified threshold.

Keywords: Cognitive radio, OFDM, Subcarrier allocation, Power allocation