Channel allocation in multi-cell OFDMA downlink systems

As wireless networks evolve to orthogonal frequency division multiple access (OFDMA) systems, inter-cell interference control becomes a critical issue in radio resource management. The allocation of the same channels in neighbor cells cause inter-cell interference, so the channel allocation needs to be taken carefully to lower the inter-cell interference. For channel allocation, we consider two types of approach: centralized and distributed. In centralized approach, there exists a central server for channel allocation. This approach gives optimal allocation results, but requires a lot of information exchanges and calculations. In this paper, under the assumption of static users, we tackle a channel allocation problem by using the centralized approach and propose heuristic algorithms that require low complexity. Our proposed algorithms show good performance in terms of throughput and power consumption compared to the other centralized schemes. Our algorithms of power allocation with fixed increase (PAFI) and rate allocation with fixed increase (RAFI) show 2 to 3% lower throughput compared to the optimal scheme while they reduce the power consumption by up to 40%. Our schemes show approximately 10% more throughput and 70% less power consumption compared to the scheme of frequency reuse factor 1 that is fully distributed. In distributed approach, each cell independently tries to allocate channels to lower the interference level without using a centralized server. We sketch a way of dynamic channel allocation considering the interference range for our distributed approach.