Coverage Analysis for Two-tier Dynamic TDD Heterogeneous Networks

Over the last decade, mobile data traffic has risen dramatically and the amount of UL and DL transmissions has been characterized by substantial asymmetry and time variations. Dynamic time-division duplex (TDD) has the capability to accommodate to the traffic asymmetry by adapting the UL/DL configuration to the current traffic demands. In this work, we study a two-tier heterogeneous network (HetNet) where the macro tier and small cell tier both operate dynamic TDD and use orthogonal frequency bands. We propose a policy that leads to different associations in UL and DL, and derive the load-aware coverage probability. We evaluate how the association policy affects the system performance and derive the UL/DL configuration, base station density, and bias factor that maximize the per tier or network-wide coverage probability.