Spectrum refarming: A new paradigm of spectrum sharing for cellular networks

Spectrum refarming (SR) is a promising radio resource management technique which allows different generations of cellular networks to operate in the same radio spectrum. In this paper, an underlay SR model is proposed for an Orthogonal Frequency Division Multiple Access (OFDMA) system to refarm the spectrum assigned to a Code Division Multiple Access (CDMA) system through intelligently exploiting the interference margin provided by the CDMA system. We investigate the mutual effect of the two systems by evaluating the asymptotic signal-to-interference-plus-noise ratio (SINR) of CDMA users, based on which the interference margin tolerable by CDMA system is determined. With the interference margin together the transmit power constraints, the resource allocation problem of OFDMA system is formulated and solved through dual decomposition method. Simulation results have verified our theoretical analysis and validated the effectiveness of our proposed OFDMA resource allocation solution, as well as its protection to CDMA services.