A Two-Level Distributed Sub-Carrier Allocation Algorithm Based on Ant Colony Optimization in OFDMA Systems

In this paper, we develop a distributed sub-carrier allocation algorithm with a low complexity in OFDMA multi-cell system , which is decomposed into two sub-problems: inter-cell and intra-cell sub-carrier allocation. During inter-cell process, based on time-variant characteristics and performance differ-ences among cells of sub-carriers, each base station applies Ant Colony Optimization (ACO) to choose available sub-carriers dynamically, which contributes to reduce co-channel interference. According to pheromone associated with channel capacity, the probability of choosing sub-carrier with better capability is higher. Then during intra-cell process, each base station sufficiently uses multi-user diversity to satisfy all users´ QoS requirements and greatly increase system throughput. Simulation results show that this algorithm exhibits substantial gains over existing frequency reuse schemes.