Uplink Performance Improvement by Decoupling Uplink/Downlink Access in HetNets

In dense and heterogeneous cellular networks (HetNets), significant imbalance between uplink (UL) and downlink (DL) transmissions may happen in regard to signal-to-interference-and-noise ratio and traffic load. Under this circumstance, decoupled UL/DL access (DUDA) is proposed for HetNets for improving system performance. In this paper, we theoretically investigate UL performance improvement brought by a DUDA mode over a conventional coupled UL/DL access (CUDA) mode based on stochastic geometry theory. We employ fractional power control to determine location-dependent user transmit power. We consider two kinds of user equipment distributions, namely uniform and clustered distributions, which are modeled as Poisson point and Neyman-Scott cluster processes, respectively. Numerical results reveal that system performance in terms of spectral efficiency and energy efficiency of the DUDA mode is better than or equal to that of the CUDA mode in HetNets. We identify the conditions under which the DUDA mode performs significantly better than the CUDA mode. Numerical results also show that the DUDA mode can improve load balance and fairness. In addition, we find that the DUDA mode is more beneficial for ultradense networks. Simulation results further validate the effectiveness and accuracy of our analytical model.