Flexible Duplex for Cognitive Femtocells in Two-Tier Networks
Small cell network architecture is considered as an effective solution to the ever growing demand for high data rate, with femtocells being a promising paradigm. The dense deployment and the uncoordinated operation of femtocells bring various challenges for interference management. Motivated by the flexible sub-channel allocation capabilities of cognitive radio, the authors propose a Cognitive Hybrid Division Duplex (CHDD) for two-tier networks. In this scheme, macrocells operate in Frequency Division Duplex (FDD), while the underlying cognitive femtocells employ Time Division Duplex (TDD). The CHDD scheme has the flexibility of providing asymmetric data rates from the TDD mode, while managing inter-tier interference with FDD.