An Adaptive Soft Frequency Reuse Scheme for LTE Systems

Enhancing cell edge user performance is an important and challenging issue for cellular mobile communication systems. The next generation cellular mobile system, 3GPP long term evolution (LTE), aims at improving cell edge user performance through effective inter-cell interference coordination (ICIC) and spectrum resource allocation schemes. An adaptive soft frequency reuse (ASFR) algorithm is proposed, aiming at optimizing the system throughput while guaranteeing the minimum data rate requirements for both cell center and cell edge regions. The ASFR algorithm can adaptively adjust the major and minor subcarriers, and their respective transmit power in each cell according to the system traffic loads. In the ASFR, the optimal resource allocation in each single cell is first determined by using exhaustive search and greedy descending methods. Then the single cell resource allocation is repeated iteratively among all cells until the system throughput does not change any more. Simulation results show that the ASFR algorithm yields an SFR resource allocation after a number of internal iterations. It is also shown that the ASFR algorithm improves the cell edge user throughput and achieves higher system throughput compared with several traditional frequency allocation schemes. These advantages reveal that the proposed algorithm is more preferred for the LTE system.