Efficient Use of Paired Spectrum Bands through TDD Small Cell Deployments

Traditionally, wireless cellular systems have been designed to operate in FDD paired bands that allocate the same amount of spectrum for both DL and UL communications. Such design is very convenient under symmetric DL/UL traffic conditions, as used to be the case when voice transmission was predominant. However, due to the overwhelming advent of data services, which involves large asymmetries between DL and UL, the conventional FDD solution becomes inefficient. In this regard, flexible duplexing concepts aim to derive procedures to improve spectrum utilization by adjusting resources to actual traffic demand. In this work, we review these concepts and propose the introduction of TDD SeNB to operate in the unused resources of an FDD-based system. This proposal alleviates the saturated DL/UL transmission commonly found in FDD-based systems through user offloading toward a TDD system based on SeNBs. In this context, the flexible duplexing concept is analyzed from three points of view: regulation, LTE standardization, and technical solutions.