Dynamic Channel Selection for Cognitive Femtocells

The ever-growing demand for mobile broadband is pushing towards the utilization of small cells, including metrocells, picocells and femtocells. In particular, the deployment of femtocells introduces significant challenges. First, the massive number of expected femtocells cannot be deployed using the traditional planning and optimization techniques. This leads to uncoordinated deployment by the end-user. Second, the high density of femtocells, including vertical reuse, leads to very different inter-cell interference patterns than the ones traditionally considered in cellular networks. And last, but not least, the possibility of having closed-subscriber-groups aggravates the inter-cell interference problems. In order to tackle these issues we consider the implementation of some aspects of cognitive radio technology into femtocells, leading to the concept of cognitive femtocells. This chapter focuses on state-of-art techniques to manage the radio resources in order to cope with inter-cell interference in cognitive femtocells. Different techniques are presented as examples of gradually increasing sophistication of the cognitive femtocells, allowing for dynamic channel allocation, dynamic reuse and negotiated reuse based on information exchanged with neighbor cells.