CRAC: Cognitive Radio Assisted Cooperation for Downlink Transmissions in OFDMA-Based Cellular Networks

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In this paper, the authors propose a novel framework of Cognitive Radio Assisted Cooperation (CRAC) for downlink transmissions in Orthogonal Frequency-Division Multiple Access (OFDMA) - based cellular networks. In the proposed CRAC framework, relay stations are deployed in each cell and have spectrum sensing capability. In turn, they can access unoccupied white space to opportunistically obtain additional sub-channels to assist relaying information for cellular users. One of promising novelties is that the proposed CRAC considers joint resource allocation which includes transmission mode selection, relay station allocation, and transmit power/sub-channel allocation, to cost-effectively provide services and applications.