Dynamic spectrum aggregation for future 5G communications

We discuss dynamic spectrum aggregation methods, opportunities, and issues for future 5G communication in cognitive cellular networks. We focus on multicarrier technologies, which have been recognized as capable of flexible utilization of fragmented spectrum opportunities in unlicensed frequency bands, such as enhanced NC-OFDM and NC-FBMC. These techniques can be applied to shape the signal spectrum so that it is concentrated within used frequency bands, and the out-of-band transmitted power and associated interference generated to the incumbent coexisting systems are limited. We present key issues associated with spectrum aggregation that are recognized at the transmitter and the receiver. We also discuss solutions of these issues that can make spectrum aggregation viable for 5G systems.