An investigation of inter-cell subcarrier collisions in OFDM-based cognitive radio networks

An OFDM-based cognitive radio (CR) system that assumes a random carrier access method is studied herein paper, where secondary users (SUs) randomly access the subcarriers belonging to the primary network. The SUs do not have access to any information concerning the availability of primary users (PUs) subcarriers because no spectrum sensing mechanism is employed. Therefore, subcarrier collisions may occur between the subcarriers of SUs and PUs. In addition, inter-cell collisions among the subcarriers of SUs belonging to different cells can occur due to the inherent nature of random access scheme. This paper conducts a stochastic analysis of the number of subcarrier collisions between the SUs' and PU's subcarriers assuming fixed and random number of subcarriers for each user, respectively. As a performance benchmark, the expression of the average capacity of a SU is derived and simulated under the Rayleigh channel fading model.