Carrier aggregation in heterogeneous cellular networks

Heterogeneous networks (HetNets) and carrier aggregation (CA) are two distinct features of next-generation cellular networks. Small cells in HetNets are vital for data off-loading and can significantly improve area and cell edge spectral efficiency compared to using just macrocells. CA further increases the transmission bandwidth and thus network capacity by aggregating multiple component carriers on the physical layer. In this paper, we propose a tractable multi-band multi-tier model to study multi-flow CA in HetNets, where base station positions in each tier follow an independent Poisson point process. Our model incorporates an appropriate notion of load which allows the study of the impact of biasing on HetNet performance. For a typical HetNet consisting of two tiers, macro cells and small cells, and two bands, 800MHz band and 2.4GHz band, we observe that the gain (in terms of UE ergodic rate) is about 35% to 40% if the small cells adopt optimal biasing factor compared to the case without biasing. Our model also incorporates the impact of band deployment. For the typical HetNet described, our study suggests that deploying the 800MHz band and 2.4GHz band in both the macro and small cells helps the HetNet best exploit the CA feature.