Spectrum refarming for OFDMA small cells overlaying CDMA cellular networks

In this paper, a novel spectrum refarming (SR) system is proposed in which the Orthogonal Frequency Division Multiple Access (OFDMA) small cells overlay the Code Division Multiple Access (CDMA) cellular networks in the same legacy CDMA spectrum. In order to predict and control the interferences from the OFDMA small cells to the CDMA macrocell, the OFDMA downlink transmissions in the small cells are arranged to be synchronous with the CDMA uplink transmission in the macrocell. We first analyze the interferences between the OFDMA small cells and CDMA macrocell, then formulate the OFDMA resource allocation problem for this proposed SR system. Through assigning the interference margins to each OFDMA small cell, a new resource allocation algorithm is proposed to solve the formulated problem efficiently. Simulation results are given to validate the effectiveness of the proposed algorithm and evaluate the performance of the proposed SR system.