Adaptive OFDM System for Peaceful Coexistence of Heterogeneous Users

With the drastic growth of every new wireless application, the spectrum becomes more and more congested. On the other hand, it is commonly believed that the usage of spectrum is vastly underutilized all over the world. Inspired by the scarcity of spectrum resource, a coexistence method which shares the same frequency band between users has been actively studied. In this paper, we propose a peaceful coexistence scenario based on an adaptive OFDM system. In this scenario, the secondary user senses the sub-carriers corrupted by the primary user. Then, these sub-carriers are excluded to reduce the performance degradation caused by the interference. Instead, we employ the adaptive modulation depending on the channel condition to preserve the desired data rate. However, this exclusion leads to the throughput degradation. To compensate this loss, the secondary user examines the channel condition and adaptively assigns different modulation scheme. The simulation results demonstrate the validity of the proposed scenario. Specifically, our scenario provides more efficient usage of spectrum and peaceful coexistence for two heterogeneous users.