Tradeoff Analysis between Spectrum Efficiency and Energy Efficiency in Heterogeneous Networks (HetNets) Using Bias Factor

—Recently, Small Base Stations (SBSs) are added to macro-cell layout to extend network coverage and increase system capacity. Whereas, most of the users incline to connect to Macro Base Stations (MBSs) due to their overwhelmingly higher transmit power. As a result, the imbalanced distribution of load leads to the underutilization of the resources of SBSs, which may deteriorate the network performance. The small Cell Range Expansion (CRE) aims at solving the problem by setting a positive bias factor. Although this technology turns out to be effective, it’s not easy to understand the corresponding effect on network performance. Therefore, the average area weighted load per cell is derived to address this issue. Meanwhile, we utilize Area Weighted Spectrum Efficiency (AWSE) and Area Weighted Energy Efficiency (AWEE) to observe the effect of bias factor from the perspective of cells per tier. Further, the efficiency (SE) and efficiency (EE) of different tiers are calculated on tier level. Simulation results show that there is a tradeoff between the overall SE and EE with varying bias factors, which provides a new insight into the analysis of network performance.